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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)

electric1 12-05-2012 14:09

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

Originally Posted by OceanPlanet (Post 949909)
That funny....Genasun has been doing this for years!! Glad you're figuring it out...;-)

Nothing funny here, Genasun is too expensive, there is no point for us to design a system at same price range as Genasun as we would be in direct competition in a very frugal and small market. So we had a simpler and cheaper system to offer, but now that this market is growing and more people are getting into LiFePO4 it makes sense economically for us to offer a more flexible system, but still at very affordable price point.

ebaugh 12-05-2012 14:29

Quote:

Originally Posted by electric1

Float voltage should be at 3.4V per cell, or 13.6V on a 4S bank.

That's gonna be a little hi for the LA chemistry. Hmmm.

electric1 12-05-2012 14:42

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

Originally Posted by ebaugh (Post 949926)
That's gonna be a little hi for the LA chemistry. Hmmm.

I should have been more clear, float for LiFePO4 should be no more than 3.4V, but it can be a little less, say 3.35V or even 3.3V. Less than 3.3V makes no sense since they are at 3.3V for a good portion of discharge time anyway.

ebaugh 12-05-2012 14:52

Quote:

Originally Posted by electric1

I should have been more clear, float for LiFePO4 should be no more than 3.4V, but it can be a little less, say 3.35V or even 3.3V. Less than 3.3V makes no sense since they are at 3.3V for a good portion of discharge time anyway.

The discharge curve I have for GBS shows a rapid fall to about 3.27V at 95% SOC at .5C. Then it flattens out. But that is a pretty high rate for this application. Like 600 amps......way too high.

Does anyone have or can email me discharge curves (for any lithium phosphate) at more like .05C?

T1 Terry 12-05-2012 17:35

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

Originally Posted by electric1 (Post 949788)
You should stop spreading this baloney around.....are you an expert in statistical analysis of cell failures? Where do you get your data to allow yourself to make such bold statements?

What you say is true only for a badly designed and badly implemented BMS, of which there have been a few reports, but its certainly not as bad as you are painting it. Several shunting BMSs have been on the market for years with no reported failures, at least not when its installed properly.

I speak from actual experience, not like you repeating some wild stories you hear on the Internet forums. My company makes miniBMS and we are proud of the quality of our product and its design which includes many safety features, proven by 3+ years of real world use.

I do agree that BMS is not absolutely required on 4S banks if handled properly, but at the same time investing a small extra capital in a simple system which serves as insurance policy, is a wise thing to do.

We have many customers using our HousePower BMS on housebanks and very happy with it.

This post is not an ad for our product, but merely an attempt to stop these silly lies being spread by some overly dramatic members.

Quote"
I do agree that BMS is not absolutely required on 4S banks if handled properly, but at the same time investing a small extra capital in a simple system which serves as insurance policy, is a wise thing to do."


If you are that confident your BMS will not kill cells but instead save them from damage (isn't that the reason for fitting a BMS in the first place?) then give a full battery bank replacement guarantee with every one of your BMS units fitted. Until you are willing to do that you are practicing and fine tuning your gadgets in the market place at the customers peril. If a BMS is not really needed for a 4 cell series system then why would someone spend the $$ and take the risks?
If a cell shunt fails to the “on” condition, how does your system turn it off? Isn’t it true that any such failed unit must be removed from the cell to stop it continually discharging that cell to the point of cell failure?

T1 Terry

T1 Terry 12-05-2012 17:59

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

Originally Posted by s/v Holiday (Post 949810)
Hi T1 Terry,

Glad to see you back on this thread. I have been studying all the previous posts and really appreciate all the good info you and others have posted here. I am also considering adding the Cell logger so I can be more involved in monitoring my bats but I have a question. Will the logger be able to read the individual cells when they are in Series? Or should I just install one for the 4 Parallel strings of batteries?

Thanks for your help.

CJ

The Junsi cell logger 8 will handle 1 to 8 sets of paralleled cells connected in series, this covers 3v to 24v systems. The units will display paralleled cell voltages to 3 decimal places, has adjustable alarm functions for high cell voltage, low cell voltage, high pack voltage, low pack voltage a differential voltage between cells. It has an alarm port that can trigger a relay to cut charging voltage, cut non essential loads, set off an external higher volume alarm.... what ever function you can think of.... all for $14 or $28 for a unit that can also monitor up to a mth or mores battery voltages for all cells monitored and display it a graph or as a table chart. This is very useful for maintenance assessing, if a set of parallel cells drop voltage more than the others under load yet register higher voltage than the others while charging it clearly indicates this is an aera that requires further attention. Generally nothing more than a loose terminal bolt or corroded connection, fixed at this stage it’s fixed, left till cell failure causes a lot more problems. If a shunt balance BMS system is continually covering up this issue it won’t appear until cell failure occurs.
If an alarm sounds then generally most people will go and see why, the cell logger flashes what parameter set off the alarm so it can be attended to, the human brain is the battery management system, the cell logger merely reports what's happening.
The question is, do you have 100% faith in a system still under development? Or do you trust your judgement ability to decide the correct course of action if an alarm goes off? $28 and your brains or what ever $$ and a system with no guarantee of success or financial restitution for failure, which looks the better deal?

If the EV community are removing their already purchased BMS systems to me it says a lot about their faith in them.

T1 Terry

T1 Terry 12-05-2012 18:09

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

Originally Posted by electric1 (Post 949913)
Nothing funny here, Genasun is too expensive, there is no point for us to design a system at same price range as Genasun as we would be in direct competition in a very frugal and small market. So we had a simpler and cheaper system to offer, but now that this market is growing and more people are getting into LiFePO4 it makes sense economically for us to offer a more flexible system, but still at very affordable price point.

Genasun is a whole different kettle of fish, a sophisticated dual battery system giving a full redundancy capability is one battery system should fail, expensive yes, but too expensive? Your system isn't offering anything like the Genasun system does is it so how can you use it as a comparison?
Never a good look try to make your system look better compared to another, it should be able to stand on it’s own merits shouldn’t it?

T1 Terry

OceanPlanet 13-05-2012 05:44

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

Originally Posted by electric1 (Post 949913)
Nothing funny here, Genasun is too expensive, there is no point for us to design a system at same price range as Genasun as we would be in direct competition in a very frugal and small market. So we had a simpler and cheaper system to offer, but now that this market is growing and more people are getting into LiFePO4 it makes sense economically for us to offer a more flexible system, but still at very affordable price point.

Makes sense. For the DIY folks that want (and are able) to put together their own system. Genasun has also sold BMS-only kits to those that want to get their own cells, build the racks, etc.

electric1 13-05-2012 09:00

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

Originally Posted by T1 Terry (Post 950026)
If a shunt balance BMS system is continually covering up this issue it won’t appear until cell failure occurs.

This is not true and it shows your lack of basic understanding of BMS systems.

Quote:

Originally Posted by T1 Terry (Post 950026)
If the EV community are removing their already purchased BMS systems to me it says a lot about their faith in them.

This is another baseless and false statement from the top of a soap box.


Quote:

Originally Posted by T1 Terry (Post 950031)
Never a good look try to make your system look better compared to another, it should be able to stand on it’s own merits shouldn’t it?

First off I never said my system is better, I said its simpler and cheaper, learn the difference. Is Cadillac better than Honda? Is apple better than orange?

And there is nothing wrong with comparing different systems based on true specs and features, not just some dramatic statement from the top of a soap box.

T1 Terry 13-05-2012 16:04

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

Originally Posted by T1 Terry (Post 950015)
Quote"

Quote:

Originally Posted by T1 Terry (Post 950015)
I do agree that BMS is not absolutely required on 4S banks if handled properly, but at the same time investing a small extra capital in a simple system which serves as insurance policy, is a wise thing to do."


If you are that confident your BMS will not kill cells but instead save them from damage (isn't that the reason for fitting a BMS in the first place?) then give a full battery bank replacement guarantee with every one of your BMS units fitted. Until you are willing to do that you are practicing and fine tuning your gadgets in the market place at the customers peril. If a BMS is not really needed for a 4 cell series system then why would someone spend the $$ and take the risks?
If a cell shunt fails to the “on” condition, how does your system turn it off? Isn’t it true that any such failed unit must be removed from the cell to stop it continually discharging that cell to the point of cell failure?

T1 Terry


Maybe you missed this post Electric1 as you haven't mentioned the level of faith in your own product to offer the guarantee I mentioned...... could there be a problem?


My knowledge comes from a lot of research over many yrs including a wealth of knowledge from the true lithium guru, jay Whitacre, and 12mths of hands on testing and either verifying or debunking various untruths being spread by some with a vested interest in these myths continuing.

(1) Cells do not go out of balance with each other if a sensible max charge voltage is maintained
(2) There is no more capacity to be gained after 3.4v per cell rested voltage
(3) 4 cell unit packs built as parallel/series packs will self balance as load and charging is applied as long as they were balanced from the beginning.
(4) Shunt balance systems need the cells to be balanced in the first place as their ability to discharge over capacity is very limited due to heat issues.
(5) Shunt balancing systems also need special charging systems so the charge rate can be reduced to a lower value than the shunts max load capability, this makes them none compatible with normal charging systems.

Basically, a shunt BMS system will maintain a battery bank in balance that would have remained in balance anyway, therefore they are not necessary and an added risk component completely nullifying the KISS principle that all good systems use. Why add complication and error points to a system that simply doesn't need it?
I have no financial vested interests in the knowledge I offer, can you say the same thing?

T1 Terry

electric1 13-05-2012 17:02

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

Originally Posted by T1 Terry (Post 950567)
Maybe you missed this post Electric1 as you haven't mentioned the level of faith in your own product to offer the guarantee I mentioned...... could there be a problem?

I didn't miss it, I just chose to ignore it because it's asinine. Why would I offer a warranty for a product I don't sell? ( battery itself ). Show me one company in the world that warranties someone else's product. Completely unreasonable. However, I work with several battery dealers who package my BMS with their cells and then offer much better warranty than if cells alone were sold. I have faith in my product based on 100s of customers with positive feedback and not a single return over 3 years. There have been warranty claims, no one is perfect, vast majority are installation mistakes though, which we still fix under warranty unless they are blatant errors covered to death in the install manual.

Quote:

Originally Posted by T1 Terry (Post 950567)
My knowledge comes from a lot of research over many yrs including a wealth of knowledge from the true lithium guru, jay Whitacre,

Well, unfortunately a lot of your "knowledge" is false, but I have no time or desire to educate you. The video posted by professor Whitacre is excellent, but most people don't understand critical details of it because he can't cram entire course of electrochemisty in such short timeframe. You have shown in many of your posts that you don't understand some important points, but I am sure its just a matter of time if you choose to keep an open mind.

As for BMS for housebank, I have always been saying, its an insurance policy for the most part, to protect the pack from the user himself. If you are meticulous and have time on your hands to babysit the battery, don't buy anything other than DVM. But, if you want to have a life outside of the battery compartment, get a simple BMS and move on.

electric1 13-05-2012 17:25

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

Originally Posted by T1 Terry (Post 950567)
I have no financial vested interests in the knowledge I offer, can you say the same thing?

This kind of attitude is the main reason I chose not to post on forums. For some ridiculous reason people think that best advise would come from someone without vested interest in the subject. Its the most retarded logic ever.

When I need advise or want to learn something, I want to hear from most vested people, since they made the subject their business and hence have true knowledge. Why would I want to learn from some armchair self-proclaimed expert who played with one battery and suddenly knows everything?

I think most people here are smart enough to see thru a sales pitch when they see one, so I don't feel any shame in sharing my knowledge despite being in the business of designing, producing and selling BMS systems. But after I encounter this resentment and attitude from people I am trying to help, I'd rather just go away and spend my valuable time elsewhere.

OceanPlanet 13-05-2012 17:37

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Whew, relax guys! As far as I can tell, most everything both of you say is true (on the tech side) however different perspectives can eventually reach different answers.

Regarding warranty, I don't think I'd be selling (mostly) Genasun if they didn't cover everything in the system. Cells & all. However, having that level of security probably adds to the cost, so I can't say that's the only way to go for everybody.

T1 Terry 14-05-2012 05:40

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
I'll leave it at that Electric1, you obviously must need to make a living from what you sell so I'll leave it up to the customers to decide, derogatory remarks don't actually help your case, especially when they are so far off the mark.
My 720Ah house system, the 180Ah demo pack and all the systems I have helped set up don't use a BMS system and they all function as designed with no out of balance issues over the last 12 mths, that speaks for itself. Set the system up properly from the beginning and it won't cause you any grief, they look after themselves as far as balance as long as you don't over voltage charge them, no need to be continually watching them, the $28 cell logger does that for you.

T1 Terry

electric1 14-05-2012 06:29

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

Originally Posted by OceanPlanet (Post 950621)
Regarding warranty, I don't think I'd be selling (mostly) Genasun if they didn't cover everything in the system. Cells & all. However, having that level of security probably adds to the cost, so I can't say that's the only way to go for everybody.

For those of you looking for a complete LiFePO4 package with warranty, google search "Lithionics Battery". They offer wide variety of batteries for any application, with integrated BMS.

electric1 14-05-2012 08:23

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

Originally Posted by T1 Terry (Post 950881)
I'll leave it at that Electric1...

You made a lot of good posts here and shared a lot of good info, kudos to you for taking the time. I only intervened when you slipped into false rhetoric, which serves no purpose and only pushes people away from true knowledge.

Lets stick to facts and numbers and leave empty rhetoric to Internet trolls :)

Overlord 14-05-2012 10:22

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Hi Electric 1. Your BMS has worked very well for me so far. My system is not set up correctly because if my battery SOC is high and we have a hot cloudless day and i am not on the boat , my outback charger over charges and your BMS kicks the solenoid and the charge is stopped till i reset....so its saved my Hi-power LifePO4 a few times already
My question is : any idea why the outback flexmax 60 does not go into float mode ?
and could it be that i have one supercell which is lower than the other 3. I have 600a , 12 x 200ah high power. I tried to balance them but found it long and tiresome . As soon as one super cell was going red and i would bleed it down , trying to get the lagging cell up , then one of the other super cells would turn red and i was jumping from cell to cell , back and fourth...all this at 3am in NC in mid winter out in the cockpit of the boat.
So for the past 5 months , i have been living with one super cell out of balance.I have 3 kyocera 240 w panels

Overlord 14-05-2012 10:31

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
I also use a link 10 monitor. When i am 300 ah in the neg , my SOC reads about 13v. This is pretty close to flat i think. I have a 600ah bank. 80 % = 480ah
Does this sound right

electric1 14-05-2012 10:39

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

Originally Posted by chris smith (Post 951032)
My question is : any idea why the outback flexmax 60 does not go into float mode ?

I just downloaded user guide for Flexmax 60/80 , on page 23 there is a setting for Absorbing and Float voltages. What do you have these set to? Chance are you have one or both set too high, hence tripping HVC.

I recommend to set Absorbing to 14.2V and Float to 13.6V

at 13V you still have plenty of energy left in the bank, you can easily drive it to 11.8V and still have reserve capacity left.

electric1 14-05-2012 10:45

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

Originally Posted by chris smith (Post 951032)
...all this at 3am in NC in mid winter out in the cockpit of the boat.
So for the past 5 months , i have been living with one super cell out of balance.

Yes, initial balance can be tedious, but its only done once. You have been on the right track, just didn't see it thru. Maybe get back to it on a nice summer day when you have some spare time? You might have been very close to finish when you stopped it.

Nothing wrong with imperfect balance as long as you have cell level BMS protection and don't drive your bank to empty every cycle. Imperfect balance simply means you would not be able to get rated bank capacity if you ever needed it, since least charged cell would limit at the bottom and most charged cell would limit at the top. BMS would prevent you from over-discharging former and from overcharging latter, so no harm done.

Overlord 14-05-2012 10:50

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Thank God for your BMS then , as by now i could have caused serious damage
mine was set Absorb 14.4 and float 13.8

electric1 14-05-2012 10:54

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

Originally Posted by chris smith (Post 951046)
Thank God for your BMS then , as by now i could have caused serious damage
mine was set Absorb 14.4 and float 13.8

I doubt there would be serious damage, these cells are pretty resilient, it takes repeated abuse or severe overcharge/over-discharge to damage them.

Drop both voltages by 0.2V and you should get better results.

Overlord 14-05-2012 10:59

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
have just done it. will wait and see what happens on a hot day. Anchored off Grand Cayman at the moment

atoll 14-05-2012 11:00

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
i have an 800 amp bank of ni cad wet cell as batteries in 1.2v cells any reccomendations on charging and use as house batteries

DaleM 14-05-2012 11:20

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
I just roughed in my solar / Lifepo4 battery bank over the weekend. Nothing blew up and the batteries charged. Here are the details:

The batteries are (4) 3.2 volt HiPower 200 amp cells bought used. They were initially balanced to 3.7 volts each. I wired them together to get 13.? volts using battery cable and lugs. The bank fits into a old plastic milk crate and drops into a locker in the boat. No BMS fitted. The existing 200 AH lead acid batteries stayed in place and are charged by the existing 120 volt charger or the engine alternator. The 1, 2 both switch picks which system is used.

Solar is mounted on the bimini. Solar is (2) 175 watt, 35 volt panels going through a Morningstar TriStar 45 MPPT controller with a separate output screen so I can read the battery state of charge. I programed it to charge at 13.8 and float at 13.6 to the LifePo4. The MPPT has a battery sense wire so the battery voltage is very accurate. Solar does not charge the LA yet.

The system charged the bank quickly with no problems. It was interesting to watch the amps quickly drop off as the bank reached 13.8. I shut it off when I left the boat just in case I screwed up in the installtion. I'll look it over next weekend before I go live 24/7.:whistling:

Here are things I learned:
Panels cost a lot to ship. Cheaper high voltage panels require an expensive MPPT charger to get the useable amps down to 12 volts. Higher priced panels and a cheaper controller may have worked as well. It is a pain to program the MPPT charger but that is the only way to not cook the batteries. All of this requires fuses and disconnect switches on every wire to make sure nothing gets fried. This is not an install it and forget it system like we treat lead acid batteries. It costs a lot but I have doubled my battery capacity in a small space. Momentarily combining both batteries seems to do nothing. The 13.8 volts does not seem to have enough voltage difference to push power to the charged lead acids.

Costs to do this:
Batteries used $600
(2) 175 watt solar cells $500 + $200 for shipping = $711
MPPT controller and remote meter $500
Wires, disconnects, fuses etc. $230

Total about $2,041
What do I get for that? A system I can pull two days of 60 to 70 amp hours out of with no sun before I switch over to engine charged bank.

What I plan to run on the system when we leave the dock:
small Engel fridge 22 AH
Small watermaker 16 to 20 AH
TV up to 12 AH
Everything else 10 to 20 AH, all LED lights, no radar, no SSB, no electric windlass on a 34 Pearson.

I thought I'd post this summary for those after me. Thanks to all on this forum for talking about Lifpo4 and solar.

Dale
Your mileage may vary, I am not an expert, this may be dangerous, don't try this at home, use at your own risk.:devil:

bill good 14-05-2012 15:43

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Interesting the specs on the cells going into service as starter battery for my boat indicate nom. voltage 3.2V & since there is not a lot of power usefull at higher levels a 3.3v 5watt zener & 1 OHM 2 watt resistor across each cell allows 14.2V alternator to give a equilizing charge on startup & with a battery charger & solar available & will bleed back to approx 3.3v per cell without then when the zener stops discharge with no elevated charge voltage final cell voltage remains above 3.2v & bal within 2MV. Analog + KISS. cost $2.00 per cell retail. So not top or bottom bal. but operating level bal. All parts used have 300% above specs so what is wrong given it is a 12V system?
Regards Bill (system under test)

ps for Atoll sounds like aircraft batteries & they have a special charger also keep away from L/A as vapour from the L/A may kill them. Balance on service intervals.

electric1 14-05-2012 16:39

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
3.3V zener is too low, you need at least 3.45V potential to charge these cells, or 3.5V-3.6V if you want decent charge rate. Full resting voltage will settle at 3.4V, then it will work for a while until it drops to 3.3V and only later down the road to 3.2V. Your 3.3V zener will spend too much time in open state and will waste too much power and get too hot.

And this system still does not give you per cell monitoring for HVC/LVC, which is more important than balancing alone.

T1 Terry 14-05-2012 16:47

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Hi Chris,
If you have access to AC mains power buy one of these https://https://www.hobbyking.com/hobb..._GENUINE_.html IMax charger balancers (around $40) and 2 https://https://www.ebay.com.au/itm/5p...item1e5dcf0032 plugs ($2.50 ea) with wiring and a https://https://www.hobbyking.com/hobb...idproduct=9282 Junsi cell log 8 ($28) so you can monitor the cell voltages while you are not on the boat by down loading the info to your computer.
The Balancer charger can charge an individual cell with settings to charge LiFeP04 cells so you can get the low cell up to where it should be, then plug in the JST-XH 5 pin plug and set the unit to balance the cells. Once it's finished you can unplug the unit and put it in the cupboard for next time.
The Junsi cell logger will record all the cell voltages so you can watch to see if there is a problem cell by following the graphs produced on your computer.
The bulk charge on the FlexMaster should be set to 14v, this is the area the most problems will be cause as the cells run away to high voltage very quickly once full so a high bulk charge will allow one cell to race away far more than is safe and the HVC will shut down the charge before the system can drop into absorb and float.
The system we developed to use the alarm port of the Junsi cell logger turns the charge off for 5 mins to allow the system load to pull the high cell down and then reconnects the charge, it will continue to do this until the other 3 cells catch up as any voltage above 3.4v in any one cell has virtually no capacity so it burns off quickly so very little is removed from the other cells, just the excess from the high cells, they soon self balance.

How long have you had the BMS fitted? Why didn't the shunt balancing bring all the cells in line, I thought that was what they were designed to do? Might be worth checking that the low cell isn't because one of the shunts is continually discharging dragging that cell low.

T1 Terry

deckofficer 14-05-2012 16:56

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
A couple of questions. Are all types of Ni cads designed to give best life by almost full (90+% DOD)? On bank sizing for LiFePO4, I've always been told to size to a series string only, if possible for desired capacity.

T1 Terry 15-05-2012 14:40

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Hi Bob,
Sorry, I know very little about using Ni Cad cells as house power batteries although I have been told by a few people using them that over voltage spikes have a good effect on clearing the crystal build ups and the same effect memory charge as deep discharging but I've never experimented with it so I'll leave that in the "here say" folder.

With LiFeP04 cells unless you have a very sophisticated system that can evenly share the load and charge between multiple battery banks you will have much better results by building capacity by paralleling cells and linking these clusters in series to build voltage, balancing is much easier and in my experience in a 4 series cell battery they will self balance if not over charged, 3.6v is the absolute max charging voltage in any one cell group in my opinion and has worked the best in my systems.

T1 Terry

mrm 15-05-2012 14:54

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
The recorded session of prof. Jay Whitacre from Carnegie Mellon University, discussing the LiFePO4 chemistry had been already referenced in this thread, but a long time ago and I think it is worth repeating, as most of questions asked recently on this thread are answered there in great detail. The first hour is a discussion of the battery chemistry and may appear too detailed to some without background in chemistry (although it explains a lot!), but around 1hr 10min he starts answering very practical questions and it is worth to carefully listen to this part at least.

Robotics Institute: Videos

Marius

JoeFish 04-06-2012 16:36

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

Originally Posted by mrm (Post 951901)
...but around 1hr 10min he starts answering very practical questions and it is worth to carefully listen to this part at least.

Robotics Institute: Videos

Marius

Marius,

Thanks for posting this. Very informative.

Best,

J

--
Bonne Amie

bdbcat 06-06-2012 09:19

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

First post, read the whole thing first. Good reading.

Just took delivery of 12 pcs CALB 180AH cells.
Unfortunately, the wrong bus bars were shipped. Too short. sigh.....

CALB offers to replace the bus bars if I send them back to China first. Now, shipping $50 worth of copper halfway around the world, twice, in order to enable a $3K battery bank makes no sense to me.

I need to make forward progress on this project. So, I modify the short bars by opening their holes so that they fit, albeit with somewhat less contact area. In my configuration, I expect to see only about 40A max through each bar, so should be OK. But not great....

I ask CALB to sell me new, correct bus bars at full retail. What's $50 in the grand scale? No can do. 500 pcs minimum quantity without cell order. sigh again.....

And so we come to my question:
Anyone know of a source for CALB 180AH cell interconnects, or an economical flex braid interconnect good for 40-50 A?

Thanks
Dave

Cotemar 06-06-2012 09:38

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
I have made battery interconnects before out of copper tubing.

1) Cut copper tubing to length.
2) Hammer tube flat.
3) Drill two holes.

Better than any interconnect you can buy

bdbcat 06-06-2012 09:44

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

Thanks for the idea. I can do that...

Do you worry about lack of flexibility? Maybe more important in auto application, with higher vibration potential....But this is going on a 50 ft motor yacht. Not too much vibration in the battery compartment.

Thanks
Dave

hellosailor 06-06-2012 09:47

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
Dave, Cotemar has a point. Or you buy some copper bar stock, a hacksaw and a drill press if there's no reasonable machine shop around.

I expect that CALB isn't very concerned about US laws, but I think we have both federal and many state laws saying that if the merchant ships non-conforming goods, or goods you didn't order, it is THEIR problem to correct. Good luck enforcing a judgement in China...but you might look to see which laws apply to you and then suggest to CALB that if they don't follow them, it might be possible to have them barred from the US market. Might or might not be, but hopefully someone there will see that it is better to suck it up, than to risk this.

At 40A I'm thinking the perforated "pipe strapping" sold in hardware stores would be a good enough conductor. Ain't copper but for a few inches, it might work while you're buying time to debate with China. Holes pre-made. And then again, you may have plenty of contact area as it is, no need to kludge further.

Cotemar 06-06-2012 10:16

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

Originally Posted by bdbcat (Post 965615)
Cotemar....

Thanks for the idea. I can do that...

Do you worry about lack of flexibility? Maybe more important in auto application, with higher vibration potential....But this is going on a 50 ft motor yacht. Not too much vibration in the battery compartment.

Thanks
Dave

You do not have to worry about flexibility, because the interconnects are so short. If you take the DYI route you can cut a block of wood to make the form shown in the attached picture. Put your copper strip in the wooden block form and hit with a hammer to make the form.

EV-Power | Terminal Connectors for SE60AHA

bill good 06-06-2012 11:09

Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
 
have used flat aliminium bar from hardware store with good results. just make sure any anodizing is cut back (both sides).

off station... out of Australia & driving across USA!!!

Regards Bill

ebaugh 06-06-2012 16:56

I considered drilling holes in copper bar. Ended up with a different style battery that has 4 screws per terminal. I think if the battery's are secure then copper bar or flat copper pipe will work OK. Just don't have the battery's where they want to move and the terminal connection is what holds them in place.

For what it's worth, the spec for my batteries is a 3/4 inch wide, 1 mm bus bar is good for 100 amps.

Be careful how you connect them, on the outside ends near where you put the 12V taps, you might have more amps than you think.

s/v Holiday 06-06-2012 23:51

Hi Dave,

I feel for you as I just took delivery of my 32 cell 100ah lifepo4 battery's and they came with no interconnects. I have looked around the Internet as was not able to find interconnects being sold by themselves so I have decided to make mine out of marine tinned copper battery cable with but connectors. I got it from zdeals.com at a good price and will start crimping tomorrow. I was going to use copper strap but I am concerned about corrosion in the salt environment. I will post some pics when I get them installed.

Good luck,

CJ


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