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Old 27-10-2012, 17:28   #631
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Well, didn't this suddenly come to life again :lol: I thought this topic had died for a while as I hadn't received an email notification of a post till this morning.
4 pages to catch up on.
Sorry if I don't acknowledge who asked what or mentioned what but the bouncing back and forth through near 100 posts would make my head spin and eyes water.

There was a reference to Winston cells max charging voltage at 4v but apparently no understanding of what the 4v refers to, it is the peak charging voltage, but at a constant current charge of 3C or 3 times the cell capacity in amps, 300 amps for a 100 amp cell, what's the chances of generating that sort of current for a 400Ah battery, 1200amps, what about an even bigger battery pack? The reason this high voltage is given is to set a point where constant current charging stops and constant voltage charging starts when using a high capacity charger to affect a fast charge, even lithium ferrous cells have an upper charge acceptance rate so voltage will climb before a 100% charge is obtained. Further down the specs the charging rate all cycle life is measured at is 0.5C, the 4v per cell no longer applies here.
A lithium ferrous cell is fully charged at 3.4v, anything higher than that generates heat, the heating is simple maths stuff, voltage above 3.4v x amps = watts. At the constant current of 3C into a 100Ah cell would be 300 amps, at 4v it's 0.6v over fully charged if all the current had been accepted into the cell, 300 x 0.6 = 180w, how long would that take to boil the electrolyte in the cell and cause gassing? By stopping the high current at this point the charge can distribute through all the cell packs and cells in the string if paralleled. At a 5amp or 10 amp charge there is much less heating, 10 x 0.6 = 6w, sustained for a very short term, not much heating so little damage, held there for hrs, the electrolyte will still boil and the cell will vent. Increase the voltage and the problem gets worse, at around 4.5v lithium plating accelerates, then big irreversible damage starts to occur.

A battery high voltage alarm or battery disconnect is really rather useless, the problem is at cell level, not whole of battery level, turn off the charging when a cell reaches 3.6v for a period of 5 mins or so is a far better option. This allows the high cell to settle and distribute the charge across all the cell or cells within that group and for any loads to burn the high bit off that cell so when charging resumes in 5 mins time there will be some capacity to accept more charge.

How do you achieve this, with a simple cell voltage monitor with an alarm function and external alarm port. This alarm port can both trigger an audible alert, like a smoke alarm, and switch a relay or trigger a timer circuit to switch a relay. Switching the alternator input needs some extra thought so the diode pack is not damaged, a simply high current diode with the cathode (stripped end) connected to the start batteries and the anode parallel connected into the charging cable would do it. So a relay cuts the alternator current after the diode close to the house battery pack, the alternator voltage sensing would need to be done at this point, before the relay, that way there is minimal voltage drop in wiring etc to affect the reading but the rise in voltage when the relay disconnects so the house battery voltage less the diode voltage drop is now sensed causing the regulator to throttle back the alternator, not suddenly switch it off, much easier on all the component still connected to the circuit when it switches back on.

A mains charger, simply switch a mains power relay before the charger, this works for combi inverter chargers as well, the charger part stops and the inverter part restarts providing the needed load to draw the high cell down.

Solar charging, simple switch the solar off before it reaches the controller, it will just react like cloud went over and blocked the sun.
Where do you get this stuff for a DIY set up?
Such a cell monitor is available and quite cheap, a Junsi Cellog 8, available from hobby shops for between $14 and $30, depending if you want data logging as well. A timer circuit is available in kit for from the likes of Jay Car etc around $30 from memory, drive solid state relays with a suitable heat sink would be the easiest method, simple stuff really and not very expensive.

Why can't the BMS manufacturers get together and come up with a common strategy? Then they would need to say the other makers unit was as good as their unit and they would have to agree that a cell balancer and what type was definitely needed in all cases..... I think striving for a single world govt and religion would be an easier task :lol:

T1 Terry
EDIT: If I missed something you like my opinion on could you ask it again please, that allows for those sick of me putting my opinion in to put that forward too :lol:
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Old 27-10-2012, 17:58   #632
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Terry, we all agree on cell level monitoring. My experience is however that out of balance situations are very rare with fractional C charging systems. Hence HVC systems are somewhat redundant. That's not to say they shouldn't be installed. ( but I would refrain from suggesting DIY solutions. ) alternator switch off is a little more complex and many times the field isn't accessible , so diversion switching is probably best.

I am currently charging at 3.65 with no issues. ( small capacity systems) mind you I have a custom charger with an aggressive stop point. ( it's not a boat system )

HVC systems are not readily available and are clumsy for current retrofits. As i said in my experience they are a piece of mind solution rather then a engineering solution. My advice, set the charge voltages low, ( 13.6v ) use a cell level warning system and don't bother with HVC systems unless well engineered.

Most arguments for HVC systems seem to talk about failure mode issues. Yet charging failures almost inevitably lead to no output rather then loss of regulation and high output.

Whatever about HVC systems I see no point in LVC systems. ( unless you have a backup battery solution)

I would also like to say that the argument in snother post for high capacity tubular traction LA is a valid one, however the data I had suggested cycle time reduction if taken to 20% SOC. further more the big advantage of lithiums is the relative insensitivity to undercharge. Undercharging is generally not an issue in fork trucks, but is a continuous issue on boats. Tubular traction batteries suffer issues if not regularly charged to 100%, Li doesn't .

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Old 27-10-2012, 19:22   #633
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hi Dave,
The cell run away at the top end of charging is real enough, I'll post a few log charts showing it happening, one with manual control, the second with the cell logger driving a timer circuit, 2 mins in this case driving a 45 amp load, the hot water heater. In the second chart the only charging source was solar, a 24v battery and the regulator set for 28v. when the charging voltage was dropped to 27.6v the steps are far more rapid, a small load across 6 & 7 cell draining 0.25Ah out and the line flattened, the controller switched off at 27.6v and all the cells remained under 3.6v and quickly balanced out.

12v systems don't suffer the runaways near as bad but it still can occur, better safe than sorry.

This HVC system is simply a back up, not designed as a control system, the log graphs show clearly what cells need a little bit of attention. Simple and easy to do for the DIY enthusiast.

T1 Terry
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Old 28-10-2012, 01:40   #634
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by CharlieJ View Post
A simple solution for the Lagoon 440 windlass wiring dilemma would be to install a 1-2-Both-Off selector switch in the B+ to the windlass. Port engine start battery B+ to Position 1 on the selector switch, stbd engine start battery B+ to Position 2 on the selector switch and the windlass B+ to the Common terminal on the selector switch.

The operational rule would be very judicious about placing the selector switch in the Both position as that would parallel your two starting batteries.
Agree totally we have decided to use a simple battery selector/isolation switch to get rid of this dangerous system that for sure will fail when we really need it. Murphy Rule 1#.

Cheers
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Old 31-10-2012, 01:24   #635
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Ok i'm presently ordering batteries and solar panels, i've designed a tilting frame to hold three 245watt panels.
Fabrication of the frame is first up then i'll strip the batteries out and mount in the new meanwhile running off shore power here at the marina during winter recess!!!!
I've decided to get the batteries running using existing power generation units rather than change everything at once.
This is an economical way for me and probably an interesting educational exercise as well as my knowledge of these systems can build as i progress.
Junsi cell logger and plugs will be delivered to Aussie address so i can pick up on our xmas visit.
Cheers all.
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Old 28-11-2012, 03:11   #636
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I need an Idiots Guide to LFP Batteries. Can anyone recommend a book or a web site with tutorials or guides please? I am looking for something that will tell me what to look for, what I need for a robust (bulletproof?) system and how to maintain it.

I intend to install about 2 x 400AH of LFPs in June next year. My problems are as follows:

1) I don't understand the pricing disparity for what are ostensibly similar products which probably came out of the same factory in China. There is almost a 200% differential in some cases.

2) I roughly know what the BMS does but don't know how it does its magic and neither do I know to distinguish between rival BMS manufacturers products.

3) I understand the need for cell balancing, but where does one get a 30A 3.4V charger? Or should one expect the battery supplier to balance the cells for you?

They sure as hell don't make it easy to join this arcane club.

-----
ps.. I am thinking of building my own small battery .. say around 100AH and experimenting now to see if I can get it working. Does the practice and technology scale up easily? Is this a good way to learn?
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Old 28-11-2012, 03:39   #637
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Neelie, I would say that LiFe in large prismatic form isnt really accessible for the new bee. You can buy some very expensive, completely packaged drop in replacements for LA batteries ( Mastervolt, Genasun etc).. if you want to roll your own, the tech isnt quite in the take it off the shelf stage.


Reading this thread will give you an appreciation of teh basics, but there is a lot of detail left unspoken
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Old 28-11-2012, 04:57   #638
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

It really is simple and straight forward once you know how, I'm sort of writing a book on how to do it but I keep answering questions on forums rather than getting on with it :lol:
As far as BMS systems for 12v house batteries - there all the same, not necessary, why would you need a 30 amp 3.4v charger? A 5 amp charger has the cells that are a little behind all caught up within an hr or so, 30 amps is a tad over the top.
Take the time to read through the posts on this thread, there is a lot of good info here, steady methodical preparation and they will last a life time but go at it like a bull at a gate without understanding why your are doing what you are doing and try to cut corners and it will bit you on the butt big time

T1 Terry
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Old 28-11-2012, 05:33   #639
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Terry - Thanks for the reply. Now get back to your book!! I'll be the first one to buy it.

"It really is simple and straight forward once you know how.." .. but then, so is neurosurgery.

Therein lies the rub, Terry, to an expert like you its a no brainer. To a newbie, it can be overwhelming mainly because the dollar cost of failure is large. Hence I think I'll start with a single small battery and experiment. I have read through most of the posts on this thread, but get lost in the minutiae when two experts collide on a differing point of view.

Thanks for the hint of only needing a 5A charger. I see your point.

Goboatingnow.. Of course, you're 100% correct.
But we all need to start somewhere, we're all newbies in some some field or other. The reason why I'd like to "roll my own", is so that I can understand and maintain it. If I buy a turnkey system, I become prisoner to their proprietary technology and to their support and spare parts department. In the end, I may be forced into going down this route, at which point, high quality AGM's will begin to look a more attractive proposition.

If I can't go with generic off the shelf components, I'll give the whole idea a miss. ... but I'm not bloody giving up yet!
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Old 28-11-2012, 10:20   #640
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Since so many who are interested in LiFePO4 Batteries frequent this thread I feel I should pass on my experiences to save others the problems I have had. Winston, via their website, announced that Balqon in Harbor City, California is their retailer. I purchased (8) 100 a-hr cells and paid in full on 8-24-12. Still no cells, and a complete run around from the company, having low level employees answer the phone and promise that Steven Barhanovic will return my call when he gets out of the meeting. Seems he never gets out of meetings as this morning is my 5th call that found him in a meeting.

Has anyone had dealings with Balqon and what was your outcome?
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Old 28-11-2012, 10:22   #641

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

neelie-
Idiot's Guide? Easy. Either give someone your wallet and tell them to take care of it, or walk away and put in conventional lead batteries. Two simple choices (decisions, decisions!) pick one and neer look back.

At this point in time I would argue that is the only simple solution, because every "lithium" battery maker is singing a different song, claiming there's only one right way to do anything (their's), and no real good track record or warranties to make good informed decisions on.

There's probably a pony in that pile someplace, but no simple or reliable way to find it.

And if your charging system can match up for it, gel batteries may give you better service (more cycles and deeper cycles) than AGMs, with the same sealed convenience. At least the folks who make those all agree on how they have to be cared for.

Bob-
I'm hoping you paid for those with a credit card. If so, call the credit card company and ask for a charge-back because the merchant failed to deliver or make the refund, and you've called them five times to discuss the problem but no one will take or return your calls. End of story and you get your money back, if it was a credit card. (You'll have to check & follow their procedures but that's typical.)
Three months with no delivery, hey, maybe the ship sank but the odds are something is very wrong and the sooner you bail out, the better the odds that you can. If you paid cash or some other means, file a small claims court proceeding and go after whatever assets might exist, while they still do.
Either way, you'll motivate the retailer and if they are legitimate in any way, they'll take care of business. If they don't pay up on small claims, you follow procedure and seize assets, like batteries. Funny how a sheriff at the front door can get past the "in a meeting" problem.

Teddy Roosevelt taught me how to use the carrot and the stick: One carrot, offered politely. Then get out the stick. Life's too short to count past "two".
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Old 28-11-2012, 10:38   #642
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Credit card purchase, the bank is sending the forms I need to fill out. I posted to see if others have had any dealings with Balqon, and a warning to others that might consider this retailer. Just being a good CF'er.
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Old 28-11-2012, 11:26   #643
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Just bought (8) 100 a/hr cells from Balqon - Advanced Transportation Solution for $880. Best price I've found so far, and only a 3 week lead time.
I have to correct this post. It has been over 3 months and still no cells, no calls returned or emails answered. I have had to put a dispute to my credit card company, hoping it isn't too late, but to save others, don't buy from this vendor.
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Old 28-11-2012, 12:26   #644
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neelie unfortunately right now there no easy way for a newbie to easily access this tech. You have to either a EE professional or a good tech amateur and can hence understand the basics. For you therefor its a waste money time cause your going to have to climb the learning curve yourself. Ie buy bits suck it and see.


The component industry isn't just there yet to offer solutions or even kits of solutions. It's a roll your own if you read this thread frequent some EV threads and have a reasonable grasp of battery electrics or some electronics background. Then you'll garner enough to have a go ! ( remember a little knowledge is a dangerous thing )

Other then that , it's a wait I'm afraid

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Old 28-11-2012, 15:08   #645
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Not good news at all Bob, I wondered why they were having a sale to clear stock a while back. I guess a lot of US companies are still feeling the squeeze on sales and are battling to keep the doors open. Maybe an email inquiry to Winston Batteries themselves and ask could they check out the problem from that end as it's harming their sales in the US and squashing a huge ptential market. Winston Chung spent millions in the US to promote the company name so he won't want that money wasted.

T1 Terry
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