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

[mrm]

Originally Posted by noelex 77

My start/ winch battery bank is getting on its last legs. The current batteries are Gel 200AHR. Overkill, but the "start batteries" also power the large 3500 anchor windlass. I anchor all the time and would like a reasonable reserve to anchor multiple times if needed.

EV-Power | LiFePO4 Battery Pack (12V/17Ah PCM)

Thoughts?

Originally Posted by from EV-Power web site

Note: Due to the limitations of the protection circuit module (PCM), these LiFePO4 block 12V batteries may not be suitable for high current traction applications. They cannot be used as starting batteries. Check with us for more details. These batteries have PCM (protection circuit module) electronics inside. The PCM manages the internal cells and provides overcharge and discharge protection.

Have you noticed that note under the pack you consider?

If you will have monitor/logger anyway, why not use separate cells?

Edit: see you edited the link. In that case, 4x100Ah will work fine.

[Lagoon4us]

Can we consider what AC powered charger would be most suitable for a 400 Amp LiFeP04
battery pack, there is some consensus previously of modifying settings on existing chargers to achieve an acceptable charge rate.

We have a 80AMP Dolphin 12Volt charger that i believe are not really configurable. Bob has indicated a Inverter/Charger is a good move so what brands/types/amp ratings do we look at?

Cheers

[T1 Terry]

Originally Posted by noelex 77

My start/ winch battery bank is getting on its last legs. The current batteries are Gel 200AHR. Overkill, but the "start batteries" also power the large 3500 anchor windlass. I anchor all the time and would like a reasonable reserve to anchor multiple times if needed.

I think LA would be the sensible choice, but having used small cylindrical lithium batteries for many years I think the time is right to boat system.

I need to order from European distributers. The customs problems here when dealing with Chinese, or USA imports are just not worth contemplating.

This company looks promising and I considering ordering 4 cells probably about 100Ahrs.
EV-Power | LiFePO4 Battery Pack (12V/17Ah PCM)

My questions.
1. Any opinion on the quality of these cells
2.Sinopoly, or winston
3.I plan on no BMS but I will manual balance as required. I would like a cell logger. This one, or is something else better?
EV-Power | Cell Logger 8 cells / 1 battery (USB port)
4. What happens if I parallel the house bank and the start bank?. I can see the potential for very high currents flowing from a charged house bank (400AHr gel) into a depleted lithium bank.

Thoughts?

There is no problem with a charged house bank linked to a lithium battery as far as high current flow from the Gels to the lithium, it would be in the other direction. Rested fully charged voltage of a lead acid batery is around 12.8v, a lithium battery fully discharged would be around 11.8v but as soon as charging starts it will jump up to 13v in a very short period, no more current will flow and the lithium battery will be less than 20% charged.
What current will be required to power the anchor winches and for how long? The start duty is high amps but very short duration, the 100Ah battery will handle that easily.
My advice would be, link the house battery to the lithium battery with a relay capable of handling 200 amps for a short time but 100 amps continuous, link this to the cell logger alarm via a small relay circuit that demands very little current, the alarm circuit in the cell logger can't handle high current or back EMF. Have a second switch to the relay so it is only closed (on) when the house battery is charging, this way the cell logger will turn the relay (and therefore the charging) off when a cell reaches 3.6v. the relay that drives the larger 200amp relay will need to ratchet in the open (off) position one the alarm port triggers the relay, but auto reset when the power is turned off and then back on.
Connect all charging methods to the lead acid house batteries.

Can the electrical folk here draw up a simple ratcheting and auto reset mini relay circuit?

T1 Terry

[hellosailor]

"i believe are not really configurable."
Can you confirm what voltage and stages it actually charges at? Does it follow a program, or is it a dumb charger? (In which case there might be a simple voltage adjustment that can be made internally.)
"Smart" devices often remind me of toddlers. "Look Momy, I made a picture on the wall for you!" Yeah, well, like the Mad Hatter said about it being the very best butter.<G>

[bill good]

Battery Vehicle Society &bull; View topic - Lifepo4 cells catch fire!

(Scan back to the start of this thread)

To all Went on a search about 12 mths ago to find out from other users of LIFEPO4 batteries last year on any high temp fires & found there had been some. The result of these two events are much worse than the B787 fires!!

This link is provided to show that more thought is needed in boat installations. We are dealing with products that may not have the QA to a standard we would like so please do not dismiss all warnings without proper considerations. The melt downs in any Li-Ion are likely to occure as a result of internal cell shorts & all the relays,fuses & other electronic bits will not help. I am thinking of making metal boxes to contain my LIFEPO4s. It is not about how stability of materals that is in question but the instalation. You would not leave 20 galls of fuel open to the cabin in the boat would you? We are after all here to share our collective knowledge.

"Safety is no Accident"

Regards Bill

[diugo]

Originally Posted by goboatingnow

The use of current counting is fraught with errors as well as you have to decide what is the top cutoff and the bottom cutoff, ie to reset the count, otherwise the amp counting gets quite rapidly out of sync. In practice I use 10 -12 bit ADCs to measure voltage and find that more reliable , certainly in lower capacity cells , where the voltage slope is more defined.

I find this post most intriguing, because counting amp-hours seems like the most practical way to keep an accurate handle on the battery's true state of charge. To make it less fraught with errors, one would need to define consistent cutoff voltage-current pairs, eg 12.00V @ 1.0A---as well as Peukert-adjust the amp-hours in and out.

I would think using voltage to infer SoC would also be error-prone, because the voltage varies with charge/discharge current, and would need to be interpolated from a rich data set (or a function representing it)---preferably specific to a particular battery.

[Lagoon4us]

Originally Posted by hellosailor

"i believe are not really configurable."
Can you confirm what voltage and stages it actually charges at? Does it follow a program, or is it a dumb charger? (In which case there might be a simple voltage adjustment that can be made internally.)
"Smart" devices often remind me of toddlers. "Look Momy, I made a picture on the wall for you!" Yeah, well, like the Mad Hatter said about it being the very best butter.<G>

The newer Dolphins are offering a LiFePO4 setting controlled with a BMS, i'm not back on board till next week so cannot check the older Dolphin settings BUT i recall a few posts on this thread discussing the difficulty.
May need to opt for a Victron inverter/charger as Bob previously discussed.

[hellosailor]

bill, are you the same bill who posted on that URL you gave "The use of a light gauge wire as a fuse to parallel (for balancing) in 12v applications instead of large strapping bars seems to have merit." ??

First, that's called a "fusible link wire" and it used to be standard in automotive design, usually the wire from the alternator output was a fusible link wire. The design carried over into boats with integral alternator/regulators. It has been obsoleted as a FIRE HAZARD for at least a decade now. Even when the fusible link wire is jacketed with a fiberglass or other wovn tube, it is a fire hazard compared to simply using a strap or suitably heavy wire, with a real primary battery type fuse. FWIW, this is old news.

Second, I don't see any mention of a battery fire there, just a blown "fuse" wire after the battery was run flat--which every maker and supplier warns you never ever to do.

OTOH there was more news about Boeing and Yuasa yesterday and today. B and other industry players want to use Li-Cobalt for energy density and say they can handle that. Japan Air apparently was quietly replacing batteries on an almost routine basis before the fires. I guess no one told them how many cycles these batteries are supposed to be good for, they seem to be replacing them often enough to send up a red flag. And Yausa apparently xrays every battery after production, because internal flaws are so hard to find and such a potential danger.

I'm glad I can get a nice safe used strontium pile from the Russians and don't have to worry about these problems. ;-)

[T1 Terry]

It seems the fire wasn't in the Dreamliner lithium cobalt batteries after all http://www.news.com.au/travel/news/airlines-switched-many-dreamliner-batteries/story-e6frfq80-1226565731266

From the article

Aviation regulators have released a picture showing the blackened remains of the battery that inspectors removed from the plane.
But they said last week there were no signs of a battery fire, while information gleaned from the flight's digital data recorder showed the power pack did not suffer a rapid surge in voltage.
The pack's voltage, in fact, had been at normal levels before it rapidly plunged ahead of the system alert that forced the emergency landing, a JTSB official told AFP last week.

the burns that can be seen on the outside of the case may indicate a shorted cable started the whole thing, not the battery at all.

T1 Terry

[hellosailor]

So if the greasemonkeys, ergh, excuse me, highly trained well-paid professional aviation mechanics, were playing swapee-swapee with too many batteries, and trying to turn the planes around too fast, and just weren't quite familiar with how these battery cables need to be positioned or accessed...

The problem might just be mechanics and cables?

[bill good]

Yes I am the same Bill. I was using the cells as a backup camping about the USA for 100Days in a hippy van!! I took the cells too low & checked each one for normal current & charge before connecting them as a battery. Some max of 50mv was noted & being smart a piece of copper wire est 50 A was used to parallel/series the 8 cells back to 12v. This was checked out of the van for several hrs & all was steady at 13.8 Driving along the next day for a few hrs when one cell vented & one copper wire vaporized ie no longer wire, Not just fused. The cells internal protection worked & no fire. The cells have two stages of protection built in. (2 cells replaced & all seems OK). I cannot find the same protection in the prismatic cell. On the Boeing it was Li battery & that aircraft was 3 weeks old 159hrs & 22 cycles. I have seen one photo showing very likely internal short in one cell that has been examined. (APU battery) The second one was the other battery called the main battery but is the same part number & as of today is still to be reported at a level where we might see that report. The metal cases contained the problem in both cases. I understand all components external to the cases has been cleared of any fault. Sealed stainless battery box is very likely to be added to my boat. T1 Terry You have got me worried about the float charging now!! Thks

Regards Bill

[T1 Terry]

Why is that Bill, because you don't have some form of cell voltage monitoring? if that's the case, then at least I have alerted you to what killed the previous cells. monitor the cell voltages, stop charging if a cell hits 3.6v, it's as easy as that.

T1 Terry

[daddle]

Originally Posted by T1 Terry

Why is that Bill, because you don't have some form of cell voltage monitoring? if that's the case, then at least I have alerted you to what killed the previous cells. monitor the cell voltages, stop charging if a cell hits 3.6v, it's as easy as that.

T1 Terry

T1 - Thanks for your patient descriptions of your practice. It seems like a reasonable and safe way to proceed. The downside is the Ah capacity of the battery is limited to the Ah capacity of its weakest cell. Some capacity can certainly be sacrificed to simplicity and regular maintenance and measuring can avoid too severe of a performance loss.

[noelex 77]

Originally Posted by T1 Terry

What current will be required to power the anchor winches and for how long? The start duty is high amps but very short duration, the 100Ah battery will handle that easily.

Thanks for everyone's replies.

The winch draws about 100A. Normal anchor retrieval is only 5 mins or so with the alternator running (but at low revs) so the AHr draw will only be about 5AHrs out of the battery. Perhaps the greatest limiting factor is the discharge will be close to 1C intermittent for 5mins. In the worst case perhaps a 1.2C continuous for close to 10mins.

(The worse case scenario is the main engine refusing to start, perhaps draining the start battery down to 60% with the attempted starts. Then pulling the anchor out without using the main engine which in a strong wind would be using more power say 10-12AHrs. The draw in this situation would be about 120A and close to continuous for 10mins)


It seems to me perhaps 100AHrs of lithium would manage this. Given the small cost difference I would rather go on the larger if I am getting close to limit.

The company sells Sinoploy, Winston and Calb (GWA?) batteries all for a similar price. Have you any thoughts on the better brand.

[T1 Terry]

The weakest cell will always be the one charged the first and flat the first, not much you can do about that except swap that cell out once the capacity gets too low. As far as stopping when the highest cell reaches 3.6v, if it's always the same cell, use a small charger and top the lowest cell up to 3.6v at the same time. If it's just an imbalance, the cell that was the lowest will now become the highest, if the original high cell returns to be the high cell again, you will know that cell actually has a problem. Then the usual checks can take place, a quick check with an infrared thermometer on the two cell terminals will tell you heaps, if they are hotter than the others while charging, there is a resistance problem. Are the terminals snug tight, is there oxidisation build up at that cell terminal/link plate? If everything checks out ok, could be a problem starting to develop with that cell, recording a week long log with the logger set for 30 sec samples can then be down loaded onto a computer and you can see just what is happening, if it's always low during discharging and always high during charging and the terminals are clean and tight, time to order a replacement cell.
remember, we are talking about 150mV to 200mV differences, not 20 or 50, that's neither here nor there and not a reason for concern at all.

If you monitor the cell voltages there are never any surprises, they let you know there is a problem a long time before it becomes serious.

T1 Terry