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-   -   LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks (https://www.cruisersforum.com/forums/f166/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069.html)

bill good 04-08-2011 01:29

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Thanks all, I did say "thinking outside of the box" The MX-60 & the Gell 250ahr bank works OK but has limited capacity. Just figured with such low charge/discharge (max 4A) a 40ahr cell should not get out of bal & would employ data logging & tracking. The other question was opinion on which chemistry appears to be better LYP or LFP or is it more sales hype?

Regards Bill

T1 Terry 04-08-2011 01:34

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Do you mean using the LFP’s as a sort of capacitor and after the sun has gone down feeding the stored energy in the LFP’s back through the MX 60? I tried a similar thing with 3 X 6v lead acid batteries to make 18v nom. and feed that back through my Plasmatronic PL20 to charge the LYP pack at a nom.12v. The result was the smoke coming out of the PL20, after thinking about why this happened I realised there is a huge number of amps stored in the batteries, all trying to get through the regulator at once and it simply couldn't cope. Fortunately I stopped the test before all the smoke came out so it still works as a solar regulator. The next trick was to try feeding the 18v nom. to the 12v nom LYP pack via the 200amps shunt attached to the PL20 regulator using a length of 6mm sq conductor cable, I still have the marks in the fingers. The shunt topped out reading at 250amps and the plastic started melting off the cable after a few seconds. Still not satisfied I tried attempt using a pair of pliers to hold the cable, the amps were lower this time and dropped back to around 100 but the cable got hot, I stopped when the terminal voltage started to head over 14v. When the charging stopped the terminal voltage dropped back to 13.5v. I tried again but this time the amps were only around 100 and the cable was very hot, the terminal voltage again reached 14v, about this stage I realised the lead had melted away around the terminal bolt on the lead acid battery. I decided that this was not a good method of fast charging LiPo batteries I then went back to allowing the PL20 to just charge using the solar input at 10 amps. Here is the graph of the cell voltages https://www.cruisersforum.com/forums/attachment.php?attachmentid=30199&stc=1&d=13124464 22
The blue line is the terminal voltage read from the left scale, the multi coloured line is the cell voltages read from the right scale

T1 Terry

T1 Terry 04-08-2011 01:44

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Hi Bill,
The LFP/LYP thing is that Winston Chung separated away from Thundersky batteries taking his patented formula that included Yttrium in the cathode with him and opened a company named Winston Batteries. The claim is the Yttrium gives better low temp performance and Winston Batteries claim the longest cycle life of all the prismatic cells with their LYP cells, 3000 cycles to 80% DoD and 5,000 cycles to 70% DoD. Who knows if these claims are true or not, even 3,000 cycles is over 8 yrs discharging the cells to 80% DoD every day, they haven't been available that long.

T1 Terry

bill good 04-08-2011 01:53

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Thanks T1 Terry & all

Bill

electric1 04-08-2011 05:44

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
LiFePO4 batteries have very small internal resistance and can absorb up to 3C charge rates if you can keep them cool enough. They will get warm at such high rate and it will shorten their life if you do it often. Best practical charge rate for every day charging is between 0.1C and 1C. Anything in this range will be happily absorbed at very high efficiency. Since IR is low, the battery is like a short circuit for the charger, so current limiting is critical ( as Terry's fingers can attest to :whistling: ). Even slight difference in charger's voltage and battery voltage will result in max current flow until voltage evens out.

Direct solar panel connection requires a diode to prevent back flow of current, and there will be voltage drop across diode, so take it into account. Direct solar charge is inefficient and risky, since you need higher voltage to overcome battery voltage and it will only happen when plenty of sun is available, but then you risk overcharge if there is no BMS in place. Since battery has low IR, panel's voltage will always track battery voltage, which may not be its MPPT point, hence wasting potentially available energy. For these reasons MPPT controller makes more sense, removes the need for diode, and pays for itself long term due to better efficiency.

Intentional Drifter 09-08-2011 10:11

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Although I believe that I understand the overall advantages of using LiFePo4 batteries for a house bank, I'll be the first to admit that I quickly get lost in the technical details. Has anyone assembled a tutorial or something along the lines of "LiFePo4 for Dummies"?

Personally, I would find such a resource quite helpful. While my current bank of Sonnenschein gel cells is doing fine, I know that it's just a matter of time. Being a catamaran, I would love to both increase my usable daily energy budget while at the same time take a lot of weight off the boat. A discussion and "how to" guide would go a long way toward helping me feel more comfortable in making that transition.

ID

T1 Terry 09-08-2011 16:31

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
There is a lot of different avenues you can take with LiFeP04 battery banks, even more than with lead acid. Because Li batteries don't suffer the loss of capacity under heavy loads (Well heavy for house batteries) a large inverter can be powered from a small Li battery, something impossible to do with lead acid.
Li batteries charge much faster so a big alternator could can be better utilised for short runs rather than long slow recharges.
Li batteries can handle being semi discharged for long periods without any damage so 100% recharging each time is not needed. This means a recharge from 80%DoD (20% capacity) up to 20% DoD (80% capacity) or any combination between 80% DoD and fully charged. there is talk that staying between 70% DoD and 10% DoD gives an even greater number of life cycles but no ones worn a set out yet as house batteries so actual cycle life is really in the unknown. the manufacturer of Winston LYP cells claims 3,000 cycles to 80%DoD and 5,000 cycles to 70% DoD so if staying in the middle some where means they live even longer you may need to write them in your will.
They adapt readily to any good solar regulator that is fully adjustable and any good regulator is adaptable to Li batteries. by this I mean the batteries will stay reasonably balance with the gentle top charging a solar regulator gives as long as the max voltage is not greater than 3.5v per cell because solar will hold them at that voltage as long as it has the capacity and the sun is shining. I like to use 3.45v per cell, this equates to 13.8v for a 12v nom. battery pack and that's a common figure used by many battery charger manufacturers.
These cells adapt to series/parallel connection with ease, I.E. A 12v 4 cell 180ah battery can be made from 4 X 180ah cells, 2 X 90ah cells in series X 4 sets to make a 12v 180ah battery, even 3 x 60ah cells in series X 4 sets to make a 180ah battery. the combination is up to you and the space you have to fit them
Li cells need to be held in light compression to stop their sides from bulging. If the side bulge some capacity can be lost because the very thin plates that make up a cell start to separate and it's the close bond that makes these cells work so well. It's not a vice like crush, more a firm hold to keep the sides flat. The manufacturers make plate and band kits to bolt the cells together in packs but if you want to make a special configuration then some planning to include a side crushing mechanism is needed.

This probably caused more confusion but you maybe able to see why a one size fits all approach doesn't really work for Li batteries.
If you have an idea what you want to achieve, what space you have to fit the cells and how you plan to charge them just ask the question, I am and I'm sure there are many other happy to help you out with any guidance you need.
Here is a picture of a home made 360ah 12v battery pack, the comparison is a 100ah 12v AGM to the right and 125ah 6v agms to the left and behind. That pack behind is 250ah AGM lead acid, weighs 85kg the 360ah Li pack including the cradle weighs 57kg

T1 Terry

spiv 09-08-2011 21:50

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Like ID, I have a good understanding of electric and mechanics, but not enough to jump into this new technology.

My new Salina has still the original battery bank which is 660ah in the stb engine room for the engine and the house and a 100ah in the port engine room for the engine only. All lead acid.

In time, I would like to add capacity and shift the batteries midship for better weight distribution.

I read an article where at the end of extensive tests and calculations, the author concluded that A/h for the $, lead acid are still coming in front even considering replacing the batteries after their useful lifespan.
Of course the premise was that you must use, discharge and recharge the batteries as per their specs (ie: never discharge lead acid more than 80%).

Has any of you more experienced done such an analysis?
Can you share your view on:
  • life-cost/ ah?
  • $/kg?
  • etc etc...

T1 Terry 09-08-2011 22:03

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Any idea what type LiFeP04 batteries were used for the comparison Stefano? I'm still looking for examples of real life cycling for LI batteries in a house battery situation. The only failures I,ve seen are from poor pack design or abuse, none that have come to the end of cycle life. That makes realistic comparisons extremely difficult.

T1 Terry

spiv 10-08-2011 05:12

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Terry,
I have searched everywhere for that article, I thought I had a PDF on my computer, but cannot locate it yet.
I think it was by Nigel Calder and it was published either on Professional Boatbuilder or Ocean Magazine.

I found one on the cost of producing energy on board: here he proves that for instance for air-conditioning, it's cheaper to use batteries and recharge them when depleted than use a genset at low load constantly.
I.E: Use the genset at high load to charge the batteries, then use an inverter to run the aircon. Then recharge. This is cheaper even taking into account the losses incurred through charging and inverting.
I cannot upload this article as it is 7MB.

s/v Thea 10-08-2011 08:49

If you do a straight comparison between LA an Li I don't think there is any doubt that LA are less expensive. There are other considerations that make Li attractive, if I could have fit in 8 - L 16 batteries I probably would not have considered the Li. In slightly more space than my 6-GC batteries I was able to put in 800Ah of Li. If you are sizing bank for worst conditions ie minimal solar and using engine or genset to charge batteries then Li gives you approximately double the effective Ah, so the 800 Ah of Li is giving me the capacity of 8 - L16s with less weight than the GCs.

The Li are much more efficient for Ah in/out so I get better return on my substantial investment in solar. As the Peukert's constant for Li is effectively unity you can efficiently use higher loads. This summer on a sunny days when my batteries are fully charged by 1:00 or so I'll run the water heater off the inverter for half hr or so, giving enough water for a couple of showers and washing the dishes, something I could not have done with the GCs.

Certainly getting the Li was risking a fair amount of $ as there is not really enough history to be certain how long they will last but for me the benefits out weighed the risks.

Doug

OceanPlanet 10-08-2011 09:21

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
The pdf is a bit long, but hopefully contributes some answers (or supplements some of great posts here). I use this in some Li vs. LA seminars I do. Sorry for any branding references...

T1 Terry 10-08-2011 16:07

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Thanks Bruce,
A good power point presentation. Do you mind if I post it on a few other forums? Regarding the alternator being run with no load, wouldn't it be easier to run the alternator output through the start batteries and then on to the house batteries? That way the start batteries act as a buffer so the alternator never sees a no load situation. What charging voltage do you use/recommend per cell? What is the Max. volts and min. volts per cell you use/recommend? Does your BMS operate off individual cells or terminal voltage?

T1 Terry

OceanPlanet 11-08-2011 00:41

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Sure T1, help spread the "Word" (lithium)...;-)

Excellent questions!

The "charge start batt first" idea is one way to go. However because the Li charge profile is different (never goes to lower float voltage), over a long period of charging (long motoring, etc.), and without the temp regulation that lead would like...it's less than ideal for the start batts (if they're lead/gel/agm). Best to have the alt protection built into the Li charging system but by no means mandatory if well options thought-out.

Genasun (for the cells they are using now) limit the max voltage per cell to 3.55V, and each BMS (typically there are two separate banks running in parallel) monitors and balances the individual cells in it's bank.

If any cell in a bank goes over 3.55V, first the BMS opens the alt field circuit, then (if the voltage keeps going up because it's some other charge source gone awry) then the BMS opens the charge bus relay to its bank (cutting it off from ALL charge sources). The other bank may still be charging (and the alt field still have a path). If BOTH banks have a cell or cells reaching 3.55V then both will cut the alt field and shut it off completely before cutting the 2nd charge bus relay.

So this system protects the batteries and alternator no matter what is going on with various charge sources (could be solar, AC/DC charger, genset, wind, hydro, whatever). Of course all sources should have their own regulation but if anything goes wrong with them it's good to know that the batt system looks after itself (and the alternator(s) without any human input.

It may sound complicated, but the idea is to make the installation virtually fool-proof for the user, to prevent over and under voltage. Hope all this is helpful....

T1 Terry 11-08-2011 01:48

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Thank you Bruce,
One small suggestion, when the field is cut to the alternator it should also open a relay in the solar + cabling before the regulator. This will protect the solar regulator from loosing the load path while the solar is still pumping amps in. With an MPPT regulator this often results in the regulator dumping every thing straight through because it no longer has a battery reference voltage, these units are generally multi voltage so often the highest possible voltage is selected anything still connected to the house circuit gets fried. There was mention of this happening a few posts back to McG I think. PWM controllers don’t change their voltage setting but they can let 20v panel open circuit voltage feed through when they loose battery sensing voltage.

Does the BMS have a hysteresis for HVC and LVC? Say HVC 3.55v open and 3.39v reconnect and LVC 2.5v and 3.1v reconnect or does it use a timer circuit?

I'm not a fan of active cell balancing as you already know but passive BMS in the form of cell protection is something Li cells/batteries definitely need because of the damage risk, just how complex is up to the buyers pocket size I guess.

To BMS or not to BMS is a very contentious and often heated subject so I’ll avoid going there, this has been a very good thread so far with lots of very good information, I’d hate to think I set off a flame war.

T1 Terry

OceanPlanet 11-08-2011 09:48

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
T1, since you brought it up... Actually Genasun's main business is MPPT solar controllers. They have no problem with a load cutoff and are used all the time with the Genasun BMS. Besides, all the loads/devices you might be worried about would be on the LOAD bus anyhow...not the CHARGE bus. So they would never see a voltage spike even if there was one.

And yes, the load bus relays have a higher HVC than the charge bus, so that the loads stay on in a HVC; and the charge bus LVC is lower than the load bus, so that charging can stay on in a LVC.

Thanks for the great questions and input!

T1 Terry 11-08-2011 15:00

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Had me thrown there for a minute Bruce but I checked out the Genasun website and it appears they deal in small solar stuff. My system is a little over 1.5kw of solar and the voltage spike resulting from cutting off that off at full tilt would destroy a regulator quick smart that’s why I suggested cutting the solar input before the regulator.
The reason for the hysteresis question was a concern about relay flutter or chatter. If the HVC had say a 3.55v per cell or 14.2v in a balanced 12v nom. pack without some hysteresis (differential) between open and close as soon as the solar stopped the voltage would drop resulting in the relay closing and the whole cycle repeating, virtually creating a PWM regulator using a relay. If it wasn't a solid state type the contacts would last in the minutes range before the relay was stuffed, especially if it was a high voltage MPPT type, the arc across the contacts when opened would not be a good thing to repeat too often.
The idea of using a separate charge and discharge bus requires everything to go through the battery so monitoring would require 2 shunts and a unit that could accurately do the math that included any losses to give you an accurate State Of Charge. This is the real gauge for battery monitoring to determine when charging is required. That magic 20% SOG or 80% DoD is the safety point so the operator really needs to know what that figure is at a glance to know if all is well or the generator is going to need a run to give a safety margin. I guess it's not so much an issue on a boat out at sea but in a motorhome starting the generator up in free camp after about 4pm or before about 10am results in a sudden drop in popularity and if you were to do it in the middle of the night a good chance of reduced life expectancy.

T1 Terry

OceanPlanet 12-08-2011 00:20

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Hey T1,
There are a few details I forgot that effect your worries. There are many of these systems working perfectly on top yachts.

1) Genasun uses a small MPPT controller on EACH panel (or one each on smaller groups) vs. running to one big controller. This is much more efficient on yachts as each controller can optimize the output of it's own panel's shading condition. Obviously this isn't the way you'd do it for residential or land-based PV where there is usually not the shading issues we have on yachts. They can handle the load cutoff no problem.

2) Since the battery banks are two parallel (or in some cases, three) banks, one always tends to have an HVC before other so you get the BMS alarm and some warning before the other goes off. So you may not even have a comeplete load cutoff for the controllers before you recognize there's a regulation problem. In may experience this rarely happens anyway except on new boats where they haven't finished adjusting the various charging sources regulation (inverter/chargers, etc.)

3) Using a regular neg. shunt monitor (like a Victron BMV602/s) in the common neg, it is simple to monitor and track the entire bank's SOC %-wise. Do it all the time. You can program in your alarms as you like; whether voltage or percentage-based.

Sorry for the slow reply, I'm in Lanzarote polishing up a battery system (920Ah x 24V) and new alternators on the Volvo 70Telefonica. Fun stuff!

T1 Terry 12-08-2011 06:50

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Now there's a problem that I hadn't thought about but obvious now you mention it, the shade from sails. I guess the panels are separated in the best vantage positions around the boat so inter connected wiring in series with a single controller wouldn't be a logical move so your system is tailored to suit sailing boats in particular.
Each system has it's own set of problems, on a motorhome it's aerials, satellite dishes vent hatches, roof top airconditioning and trees in all the best camping spots :lol:
Do boats more rely on generator charging and solar as a top up? Do many use wind or water driven turbines?

920ah @ 24v, that is a serious system, is it for propulsion or just house power? I guess air conditioning would be run off a system that size because the near zero Peukert’s factor of Li cells would make that more efficient than an engine driven unit.
Thought about the controller per panel idea but the cost would be prohibitive on my type of set up, too many panels. Ultimately the final plan for my system is 3 X 48v 180ah Li battery pack that can be switched from parallel for house power to series to provide 144v nom for a hybrid drive set up with regen braking and solar for recharging.

T1 Terry

Adamante 12-08-2011 12:32

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by T1 Terry (Post 749636)
Ultimately the final plan for my system is 3 X 48v 180ah Li battery pack that can be switched from parallel for house power to series to provide 144v nom for a hybrid drive set up with regen braking and solar for recharging.

What would be the advantage of switching from the 144 V series combination to the 48 V parallel for extracting 12 V house power? In either case a DC to DC converter would be needed so why bother with the switching?

T1 Terry 12-08-2011 13:23

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Adamante (Post 749832)
What would be the advantage of switching from the 144 V series combination to the 48 V parallel for extracting 12 V house power? In either case a DC to DC converter would be needed so why bother with the switching?


A 4kw inverter and all appliances are 240vac. No more paying ridiculous prices for half efficient products because that is all that can be used because of the 12v battery limitation.
Previously big inverters were not really an option because lead acid batteries lost a lot of capacity once the C20 rating was exceeded, the only way around it was to use a huge battery pack. Those days are over with Li batteries, they don't suffer the lost capacity effect.
There will be a DC to DC converter as well, linked to the 12v start battery to keep it charged and to power the LED lights and a few 12v appliances like the GPS and stereo but the major appliances are 240vac.
A fridge freezer for instance, just over AU$2,000 for a 221ltr Waeco fridge freezer or AU$550 for a 250ltr frost free auto defrost Fisher & Paykel. Aust govt energy and efficiency tested to operate in 40 Deg C and higher temps, the Waeco struggles above 32 deg C and burns a lot of battery power because they are running at or near 100% duty cycle in those temps.
A 1hp split system aircond in the bedroom will run all night from the battery bank so sleeping and mouldy clothes will no longer be a problem in the high humidity areas.

Things may be different on a boat with electrical safety issues but Iíd imagine an RCD/RVD combination unit would keep things safe.

T1 Terry

s/v Jedi 12-08-2011 13:52

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Please stop this talk about 144V house battery banks and matching inverter/chargers etc.... I can barely control myself now and am afraid you guys are gonna push me into spending mode again...
:jump:
ciao!
Nick.

T1 Terry 12-08-2011 18:24

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by s/v Jedi (Post 749883)
Please stop this talk about 144V house battery banks and matching inverter/chargers etc.... I can barely control myself now and am afraid you guys are gonna push me into spending mode again...
:jump:
ciao!
Nick.

The 144v is for propulsion not as a house battery bank. The 3 X 48v house battery banks are switched from parallel connection to series connection to create the 144v. The number one 48v pack remains tied to the inverter and the DC to DC converter, the other two 48v packs switch.
It could work well for someone looking at pulling the diesel propulsion motors out and fitting electrics and mounting one of the diesels in a better position as a gen set.

T1 Terry

Adamante 12-08-2011 18:30

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Using 240 V AC appliances instead of 12 V DC is a very sensible approach. I plan to do the same, but at the 120 V AC level.

However, that still doesn't explain why you are switching your battery connection to a 48 V DC parallel configuration to run the 4 KW inverter. Why not run the inverter directly from 144 V DC?

s/v Jedi 12-08-2011 18:49

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Adamante (Post 750076)
Why not run the inverter directly from 144 V DC?

Exactly, why consent with that dull old 48V stuff. I was serious mentioning 144V house banks!

cheers,
Nick.

bill good 12-08-2011 19:40

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
But them 4KW inverters for grid power are about $1/watt ie $4000.00. Also they want a lot more than 144vDC. getting into danger zone!!

Bill

T1 Terry 13-08-2011 07:21

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by bill good (Post 750105)
But them 4KW inverters for grid power are about $1/watt ie $4000.00. Also they want a lot more than 144vDC. getting into danger zone!!

Bill

Exactly, a lot harder to recharge as well. A 48v 4kw inverter with built in soar controller and 50amps mains battery charger with the voltage levels reset to suit Li batteries was AU$980 including freight. Anything above 125vdc is heading into dangerous lethal territory, switch these voltages is trick business requiring capacitor precharging among other things and becomes a specialist type build. Overkill for house power but a necessary evil for electric propulsion if you need to make big kw's and torque.

T1 Terry

witzgall 13-08-2011 08:07

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
I will give you all the back story sometime soon, but in the meantime, it looks like I will have the opportunity to install a 16 cell, 800ah 12v LIFEpo4 bank on our boat, taking up the space of our 4 t-105 trojans, and weighing about the same. To do this, I imagine I will need to wire them up as 4, 3.2 volt banks, each comprised of four, 200ah 3.2v cells. My two battery boxes are back to back, with space for two banks in each one. So the individual cells would be connected to each other with bus bars, and the two adjacent cells would be attached to each other with (hopefully) bars as well. But the two, resulting 6v cells would need to be attached to each other with cable, and I am unsure as to what size I would need, or if this is even safe, as the currents these two cables could carry have the potential to be huge!

The reason I wish to do it this way, instead of just making up four, 200ah 12v banks and them connecting them in parallel, is that I have a single BMS system, designed to attach to a 4 cell 12v system.

Should I look into getting another BMS, is that the better way?

Chris

s/v Jedi 13-08-2011 08:14

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by T1 Terry (Post 750264)
Anything above 125vdc is heading into dangerous lethal territory

Actually, it is current that kills, not voltage. 48V DC is often considered the upper level before it becomes dangerous (which is why 48V is used so often) but I read about a case of electrocution at 42V DC so 48V is still not 100% safe.

If one is scared of voltages above 48V then you can't have AC anymore as the world uses 110-250V. It is a mistake to think that 220/230V is more dangerous than 110V: statistics of cases of electrocutions show that.

The issue of cost is something else... 48V DC equipment will be better priced and I agree it's a big step beyond the 12V systems most boats are handicapped with now.

ciao!
Nick.

Paul L 13-08-2011 08:37

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
What length and type of warranty are vendors giving on LifeP04 batteries when used in a marine environment?

bill good 13-08-2011 16:35

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
The higher the voltage the further the arc can be apart this is why the DC house power was found to have caused a lot of fires in the years past!! AC going thru zero voltage which did help put the arc (fire) out. To protect the batteries a current limiter type of fuse could be used as a link between the cells without the need of an external mounted fuse. The advantage of AC is to do with the distribution.

Adamante 13-08-2011 17:46

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by T1 Terry (Post 750264)
A 48v 4kw inverter with built in soar controller and 50amps mains battery charger with the voltage levels reset to suit Li batteries was AU$980 including freight.

Aah, so itís the cost of the 144 V inverter vs. a 48 V inverter. That makes sense.

I see 144 V inverters sell for about $2,500, so you are trying to save around $1.5K. Saving money is good :thumb: - if you can make it work.

But is it practical? For your switching scheme to work you have to add more power cable wiring, switches, and relays with contactors capable of handling the motoring currents. This type of equipment will not be not cheap. So you would be adding cost, complexity, a need for additional maintenance and creating the possibility of additional points of failure in the system.

You will also have an unbalanced load on your battery pack. If I understand your scheme correctly, the inverter will be normally powered by the parallel combination of the three battery banks. When you switch to motoring, two of the banks will see only the motoring current draw, but the third bank will also be seeing the inverter draw (and the DC/DC converter). So the three banks will be discharging at different rates. What do you do when pack one reaches 80% DoD while packs two and three are at 50%? How do you monitor and manage that so you donít kill one of the banks? Iím sure it can be done, but I suspect again at an additional cost and complexity.

Since the first bank will be cycled (charge, discharge) more often than the other two banks, you will have batteries at different points in their life cycle. This would of course depend on the frequency of the bank one cycling, but I would guess that if you are long- term cruising, bank one will be cycled at least once per day. Maybe not a huge factor given the life cycle estimates for LIFEPO , but still this inserts a dynamic variable into the system that needs to be managed.

How do you plan to implement the charging scheme? I assume you will have a 48 V DC charger to charge the parallel bank off the genset, solar, or shore power. How will you charge the batteries while motoring? When your batteries are in a series combination, your 48 V DC charger will only be able to charge one of the three banks. What about the other two banks? Or will you have another 144 V DC charger running off the genset to charge the whole string at one time? Again, added cost and complexity.

I have not seen this type of a complex powering scheme proposed for a boat before. It doesnít mean it canít be done or that itís not a good idea. I suspect that you have thought all this through more than I have, so it would be helpful if you could address those questions.

T1 Terry 13-08-2011 18:45

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by witzgall (Post 750282)
I will give you all the back story sometime soon, but in the meantime, it looks like I will have the opportunity to install a 16 cell, 800ah 12v LIFEpo4 bank on our boat, taking up the space of our 4 t-105 trojans, and weighing about the same. To do this, I imagine I will need to wire them up as 4, 3.2 volt banks, each comprised of four, 200ah 3.2v cells. My two battery boxes are back to back, with space for two banks in each one. So the individual cells would be connected to each other with bus bars, and the two adjacent cells would be attached to each other with (hopefully) bars as well. But the two, resulting 6v cells would need to be attached to each other with cable, and I am unsure as to what size I would need, or if this is even safe, as the currents these two cables could carry have the potential to be huge!

Quote:

Originally Posted by witzgall (Post 750282)

The reason I wish to do it this way, instead of just making up four, 200ah 12v banks and them connecting them in parallel, is that I have a single BMS system, designed to attach to a 4 cell 12v system.

Should I look into getting another BMS, is that the better way?

Chris


Hi Chris,
The size of the connecting cable is determined by the number of amps you wish to pass through it and the length of the cable. This one gets tricky because it's actually 6v you are trying to pass from one battery bank to the other, the lower the voltage, the higher the amps, the bigger the cable needs to be to minimise voltage drop. Many electricians work on a 5% voltage drop being acceptable but 5% at 6v 2% is even a bit much.
If the distance between the two 6v battery banks required a cable roughly 15ft long it would need to be 000AWG or bigger to carry 200amps and there would be losses, if the two banks were each 12v even though 2 cables would now be required using the same 200amp figure the losses would be negligible.
If you are willing to run 2 parallel 000AWG cables between the 2 6v battery banks then this is probably the better way to go because any imbalance between the cells is counteracted by another cell within each 3.2v unit. If a cell fails for any reason a voltage drop would be quickly seen in that cell group, the bad cell located and isolated and the battery pack brought back on line with just a 200ah loss of capacity but no loss of current supply capability. In other words, every thing would run as normal but more frequent recharges would be required till a replacement cell could be found and fitted.
Two 12v packs running in parallel would require 2 BMS units, the same amount of cabling but more of a chance of imbalance between the two 12v packs and less cell self balance but as a plus, the system could remain up and running while you isolated the battery bank with the crook cell, tested and removed that cell. A good BMS with HVC and LVC would be needed to protect the individual cell that would be running in that bank but it's a do-able, just cost more.
Each method has it's advantages and disadvantages, $$ and complexity is the real deciding factor.

T1 Terry

T1 Terry 13-08-2011 19:25

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by Adamante (Post 750559)
Aah, so itís the cost of the 144 V inverter vs. a 48 V inverter. That makes sense.

I see 144 V inverters sell for about $2,500, so you are trying to save around $1.5K. Saving money is good :thumb: - if you can make it work.

But is it practical? For your switching scheme to work you have to add more power cable wiring, switches, and relays with contactors capable of handling the motoring currents. This type of equipment will not be not cheap. So you would be adding cost, complexity, a need for additional maintenance and creating the possibility of additional points of failure in the system.

You will also have an unbalanced load on your battery pack. If I understand your scheme correctly, the inverter will be normally powered by the parallel combination of the three battery banks. When you switch to motoring, two of the banks will see only the motoring current draw, but the third bank will also be seeing the inverter draw (and the DC/DC converter). So the three banks will be discharging at different rates. What do you do when pack one reaches 80% DoD while packs two and three are at 50%? How do you monitor and manage that so you donít kill one of the banks? Iím sure it can be done, but I suspect again at an additional cost and complexity.

Since the first bank will be cycled (charge, discharge) more often than the other two banks, you will have batteries at different points in their life cycle. This would of course depend on the frequency of the bank one cycling, but I would guess that if you are long- term cruising, bank one will be cycled at least once per day. Maybe not a huge factor given the life cycle estimates for LIFEPO , but still this inserts a dynamic variable into the system that needs to be managed.

How do you plan to implement the charging scheme? I assume you will have a 48 V DC charger to charge the parallel bank off the genset, solar, or shore power. How will you charge the batteries while motoring? When your batteries are in a series combination, your 48 V DC charger will only be able to charge one of the three banks. What about the other two banks? Or will you have another 144 V DC charger running off the genset to charge the whole string at one time? Again, added cost and complexity.

I have not seen this type of a complex powering scheme proposed for a boat before. It doesnít mean it canít be done or that itís not a good idea. I suspect that you have thought all this through more than I have, so it would be helpful if you could address those questions.

I'll try to start from the top and work down.
It's not only the cost of a 48v inverter V 144v inverter, there is a charger as well and ease of obtaining a replacement or fixing the fault. The 48v inverter/charger/solar regulator I'm trialling is a card based unit. A few test points will determine what card failed so spares could be carried if the inverter was a life and death issue.

I'm guessing the cabling wouldn't be an issue, to make up a 180ah 144v battery bank would require the pack to be broken up to better distribute the weight. Isolation would also be required between packs for the purpose of maintenance so it's just a different type of switching relay rather than no relay at all.
The unbalanced load on the No.1 battery pack would be partly offset by it being the only pack being charged by the 48v charging system. In my case that will be 1kw of solar but it could be an alternator in a hybrid assist set up or the whole 144v pack charged by a gen set.

In the case of an out of balance between the 3 packs a simple switch back to parallel connection will again balance them. I expect the no.1 pack will cycle more but not between the fully charged and 80%DoD but rather in the middle range. There is no data regarding the effect of this but a number of informed sources including Jay Whitacre from the Carnegie University suggest that this intermediate state cycling has no real effect on cycle life so it can virtually be ignored. The practical results are yet to be tested but with a 3,000 cycle life to 80% DoD it will take 8 yrs or more to see who's right or wrong.

My case is a lot different to a boat application as it's in a motorhome so my recharging while in series mood will be via regenerative braking. As it will be a hybrid set up it will double as a genset if required.
In a single drive set up in a boat I can see this system working quite well, the electric AC motor connected to the prop shaft with the diesel engine coupled with a dog clutch behind the electric motor. When more grunt is needed or regen required or steaming for a long period a combination of the two units could be used but in general for manoeuvring in or out of a mooring etc simple electric propulsion with switchable reverse would be the ideal set up.

Hope I didnít miss any bits, naturally this is a hypothetical system I'm looking at for a boat application so lots of fine tuning would be needed but I think it would work well.

T1 Terry

OceanPlanet 14-08-2011 08:07

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by T1 Terry (Post 749636)
Now there's a problem that I hadn't thought about but obvious now you mention it, the shade from sails. I guess the panels are separated in the best vantage positions around the boat so inter connected wiring in series with a single controller wouldn't be a logical move so your system is tailored to suit sailing boats in particular.
Each system has it's own set of problems, on a motorhome it's aerials, satellite dishes vent hatches, roof top airconditioning and trees in all the best camping spots :lol:
Do boats more rely on generator charging and solar as a top up? Do many use wind or water driven turbines?

920ah @ 24v, that is a serious system, is it for propulsion or just house power? I guess air conditioning would be run off a system that size because the near zero Peukertís factor of Li cells would make that more efficient than an engine driven unit.
Thought about the controller per panel idea but the cost would be prohibitive on my type of set up, too many panels. Ultimately the final plan for my system is 3 X 48v 180ah Li battery pack that can be switched from parallel for house power to series to provide 144v nom for a hybrid drive set up with regen braking and solar for recharging.

T1 Terry

T1, Yep house banks. In this case it is WAY overkill for the boat's loads but the rules have a minimum battery weight. So their capacity is so much that for some legs they don't need to charge at all (bring less fuel, be lighter, go faster....). Very cool plan you have for hybrid drive! Will you be posting info on that on some other site? Ok to PM me off this thread...we're getting way off the track...;-)

witzgall 18-08-2011 18:15

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
If I can get them all into the original battery boxes, then the distance might be < 2 feet between the two sets of 3,2v banks.

Chris

Quote:

Originally Posted by T1 Terry (Post 750595)
Hi Chris,

If the distance between the two 6v battery banks required a cable roughly 15ft long it would need to be 000AWG or bigger to carry 200amps and there would be losses, if the two banks were each 12v even though 2 cables would now be required using the same 200amp figure the losses would be negligible.


T1 Terry


electric1 19-08-2011 08:31

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by witzgall (Post 754069)
If I can get them all into the original battery boxes, then the distance might be < 2 feet between the two sets of 3,2v banks.

Chris

Don't worry about the distance, just use appropriate cable size and even oversize it if you can. Any welding shop can supply 1/0 or 2/0 thin stranded cable with lugs. Voltage drop on a few feet of such cable is negligible. In EVs people split battery banks between front and rear all the time, there is no problem at all.

DO NOT parallel strings of series connected cells. Parallel cells to get desired AH capacity, then string those paralleled groups in a single 4 unit series string for 12V nominal bank. Paralleling strings is asking for trouble in the long run. There is no need for multiple banks either, its a waste of cells/weight/money. Single bank gives you best return on investment.

T1 Terry 19-08-2011 16:16

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by witzgall (Post 754069)
If I can get them all into the original battery boxes, then the distance might be < 2 feet between the two sets of 3,2v banks.

Chris

Misunderstood what you posted, I thought you were saying the battery boxes were in each side of the boat, not that they were side by side.
I would recommend against using solid bar to link the cells but rather braided link like the ones from EV works or the multiple layer copper straps that Trev from Basically Natural sells. I'm sure there are other sellers with similar style cell links. The cable to link the two battery boxes can either be made up from welding cable like Electric1 suggests or from the cable the car audio people use, this was my choice because the cable conductor is super fine strands but the outer case is a tough hard wearing material. The welding cable is often rubber coated to give it the flexibility but it's not hard wearing and damages easily.
Don't forget to sand the oxide coating off the cell terminals and link straps and paint them with "Alminox" or one of the other anti corrosion pastes recommended for aluminium to copper electrical connections. A simple but time consuming job but will save a lot of future headaches.

T1 Terry

romanystar 29-08-2011 14:38

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
I'm new here, as a member, but have read most all the threads on this subject. I've seen mention in other places that the ability of these batteries to accept a high charge rate can lead to melting down an alternator that does not have temperature protection in the controller.

I am close to spending the money to change out my tired T145's to 8 CALB 180's. I'm trying to determine which other pieces of the puzzle will need to be upgraded. I already have a programmable shore power source, and an adjustable MPPT solar controller.

The Ample Power alternator controller is nearly 20 years old, but does a fine job of 3 step regulation. Should I be replacing it to get something that will monitor battery temperature? Any suggested products?

Paul

OBTW: Welding cable is not usually tinned and is not a great idea in the marine environment.

romanystar 29-08-2011 16:45

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Quote:

Originally Posted by romanystar (Post 762257)
Should I be replacing it to get something that will monitor battery temperature? Any suggested products?

Whoops, meant to ask if there is a suggestion for an alternator controller that monitors alternator temp.

I am aware of the Balmar, but don't like push on spade connectors on the boat.


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