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

[diugo]

3.45V is the open circuit voltage the cell naturally falls back to, after a full charge and after all charge (and load) current is removed.

[mcarling]

NTSB new/burned comparison photos of the 787's lithium cobalt batteries.

[goboatingnow]

LiCo. great energy density, great fire hazard. Just ask Sony

dave

[SailFastTri]

I think the elephant in the room is FIRE!

I've been monitoring this thread for a while, and although the new technology is clearly very attractive, what's been holding me back is worry about what I don't know. What you don't know CAN HURT YOU.

The very newsworthy example is the Boeing 787 battery fires in the news. I also remember issues reported in the news a few years back when cell phones were combusting in people's pockets. Those systems are designed by EE's who presumably have the best experience, so what makes you (or me) think we can design a system that won't burn our boats to the waterline?

I also wonder whether insurance would cover a fire caused by new technology mods cobbled together by a boat owner from diverse suppliers with components of unknown origin/quality and questionable testing as a system?

I will continue to watch this technology with great interest, but until these systems are marketed and sold by main stream channels as a "system" I'll watch from the sidelines, I think. Can someone convince me this is wrong?

[diugo]

Balqon is now effectively sold out of its 260Ah and 400Ah clearance cells.

[noelex 77]

Originally Posted by SailFastTri

. Can someone convince me this is wrong?

This is common, but largely unfounded concern.

There are many different types of Lithium batteries and most are quite dangerous. They will burn with a fire that is very difficult to put out and even sometimes explode.
LiFePO4 batteries are quite different and are much, much, safer than other lithium chemistries. The general consensus is that they are safer than lead acid batteries, especially wet cells.
The only slight area for caution is that LiFePO4 batteries can deliver very high currents, just what you want in a battery, but the fusing needs to be well done.

When these batteries replace lead acid batteries hopefully we should see a reduction in some of horrific eye injuries that are seen with LA batteries.

[deckofficer]

Originally Posted by diugo

Balqon is now effectively sold out of its 260Ah and 400Ah clearance cells.

Folks that waited too long will have to step up to the 700 amp cells at $462. Looking forward to one of the members using these cells and sharing pictures.
Balqon - Advanced Transportation Solution

[goboatingnow]

Originally Posted by SailFastTri

I will continue to watch this technology with great interest, but until these systems are marketed and sold by main stream channels as a "system" I'll watch from the sidelines, I think. Can someone convince me this is wrong?

Why should anyone convince you of anything. All we can do is put as much information as we find into yours hands. Then its up to you.

As to what is sold by "mainstream" channels, have you looked at Victron or Mastervolt.

Dave

[hellosailor]

Wired reports that it seems the Boeing fires started after the plastic separator film in the batteries was somehow punctured, with no indication that charging, etc. had anything to do with it. This would point to a manufacturing defect at Yuasa. Obviously, that's still a work in progress.

[NahanniV]

Originally Posted by diugo

...asymptote....

I had to look that up. Then I decided to pull the plug on my charger

Originally Posted by diugo

3.45V is the open circuit voltage the cell naturally falls back to, after a full charge and after all charge (and load) current is removed.

OK, I think mine will get there eventually.

I'm letting the cells settle in parallel while I put together a load test.

I'm thinking of a 20A load.

[diugo]

I'm doing a live load test right now, doing a rare full discharge. Have used 140 of my 260Ah so far, taking 70 hours, so just 2A average current. Timing is good, as it's been quite cloudy and will remain so all weekend. At this rate, should completely run out of juice some time Monday. It better be sunny by then though, or I may have to dig up my old AGMs!

Nothing but solar panels on the USS Asymptote!

[Lagoon4us]

Looking and learning from the Airline fire they place the BMS and Battery pack in an aluminium box, this is possibly an idea to be incorporated in a marine installation rather than simple banding.

Any small possibility of fire is contained within and leaves the top or area above only to have some fire rating, ours goes under a bunk and probably similar to most installations, the lead acids are currently housed there by the manufacturer with no provision for fire or gassing.

I think with some good containment design it will be much much safer.

[T1 Terry]

Originally Posted by mcarling

Sounds good Barra. 400AH of LiFePO4 will give you more usable capacity than 540AH of AGM.

However, I agree with the point above that 600W of solar will be a lot for this size battery bank. Even the 300W you have now is large for this size battery bank.

Sorry if this has already been sorted but I've got a lot of catch up reading to do.
I originally had 1.5kW of solar at nom. 12v charging a 360Ah pack with no issues, the solar regulator does all the work, when the battery is full it stops charging, that's the way solar works. I now have around 3kw (varies because i'm always experimenting) of solar charging a 720Ah pack, all at 12v nom, no issues and there hasn't been any issues for the last 2 yrs.
conctant voltage charging (CV) at a voltage not not higher than the toal full pack voltage and there are no problems, try to charge them with a much higher voltage and you are going to have troubles every step of the way. It's the old glass of water thing, no matter how fast or slow you pour it in, when it's full it's full, you can't put any more in unless you increase the volume of the glass. you can't force 14.4v into a battery that is full at 13.6v and not expect an over flow, or in this case, an over voltage on at least one cell.
The only possible reason for trying to charge at a higher voltage is to try and get it happen faster, just like the glass of water, if you don't have full control as it reaces full, you are going to have an overflow. Pluse Width Modulation (PWM) control allows that last bit to full to be trickled in there so there is no over flow.

I'll send you a PM Barra

T1 Terry

[T1 Terry]

Does anyone have any concrete information regarding the Boeing problem with their lithium cobalt batteries? Has the battery coolant been ruled out yet/ That was the cause of the chevie volt battery fires, not the batteries at all.
if you are going to use a lithium chemistry that involve huge thermal runaway issues you must use a coolant system as well, i can't imagine they would put lithium cobalt batteries in anything but a model plane with a good coolant system, this is the reason for the aluminium case I think you'll find, coolant containment, not battery containment.

T1 Terry

[hellosailor]

Terry, Wired magazine reports that investigators are looking at punctured separator film in the battery as being the cause. That is, the plastic film which separates the innards of each cell apparently had or developed pinholes or cracks, which allowed the wrong stuff to mix and overheat and light up. The same way that sticking a knitting needle through the battery would have. That's preliminary--but what they are reported to be concentrating on.

FWIW, in the US a 600W solar array for a 400AH battery would not be out of line. The 600W array would provide a full charge for flat batteries in 10 hours, more or less. And since we expect to get the equivalent of 5 hours of full power in any full days use from a solar array, that means a 600W array could recharge a 400AH battery from the 50% discharge point, in one day. Or fully recharge in two days.

Given two or three days of overcast, a battery bank down more than 50%, and wanting to recharge that in a day or two...not excessive sizing at all, really. Rather generous, but not at all excessive.