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

[Maine Sail]

Originally Posted by NahanniV

What type of a battery analyzer do you have ?

I'm also not sure from you post if your measurement is for all the cells in series ? Or a single cell ?

I think the rated value for the cells may be an impedance value, measured by passing an AC current through the cell; That test would give a lower value than the resistive load method outlined by diugo. I don't pretend to understand it all: How to Measure Internal Resistance – Battery University

I think the test outlined by diugo could give a good baseline to compare future tests against.

ALSO, if you missed my previous post, I'd be interested to know what the manufacturing codes on your cells are.

Thanks,
JM

The analyzer is an Argus 500 specifically designed for testing batteries.. I just tested it again, on the large aluminum nuts, instead of the SS bolts, and got .58 mΩ...

Good news is that both my Midtronics and Argus analyzers are showing this 400Ah battery producing more than 4800 cranking amps. Course I am certain the internal algorithms are not "tweaked" for LiFePO4 but I have to guess it may be a close approximation to CA ability.....

[senormechanico]

Originally Posted by ebaugh

Other than the leakproof, no maintenance aspect, Im not sure there is much advantage to AGM over LA. There was a guy a while back on this thread that made a really good case for tubular LA forklift batteries. Even in comparison to LiFePO4.... If you can deal with the size and weight, and perhaps the cost in North America. I think they may be more widely available in Europe.

Battery weight is never a good thing in a boat, even in a submarine.

[senormechanico]

Originally Posted by deckofficer

How much longer could it be? This battery is rated 1280 w-hr and I'm past 1430 w-hr. A lot better than the first cycle at 980 w-hr, but I thought I timed it right so my constant checking of cell voltages didn't interview with my dinner time.

We've been there charting a boat refrigerator equipped with a state of the art phase change cold plate !

Eight hours (and sometimes many more) of temp vs time at ten minute intervals for several cycles over many days. AAAaaghhh...!!

[FlyingCloud1937]

Originally Posted by downunder

Seems it is simply too new a concept for Lloyd at present. Thats OK.

The insurance issue he raises is a red herring though.

Downunder and everyone else.

First I have 30 years experience in the Marine and marine Electrical arena. I grew up as a Marina Owners kid.

I have had a boat/yacht most of my adult life. I design on-board power systems as a business.

I don't spec anything for another yacht that I wouldn't use on my own.

I want to see and expect that the Li technology will mature into an aspect that I can spec for my customers...it's just not there today.

I appreciate all of you early adopters because you help pave the way. But each and everyone of you are not in complete agreement or or only following another's lead.

Insurance is not a red hearing neither for the yacht owner nor the installer.

I have seen many an issue not even involving an experimental technology have look and read here https://www.google.com/#hl=en&tbo=d&...w=1251&bih=653

research Li here https://www.google.com/search?q=life...w=1251&bih=653

My point is your are breaking the trail and early adopters are the beta testers whom bare most of the costs.

I happy to sit on the sidelines and cheer on the early adopters so that I don't have to bear the costs to reach a mature industry.

My own out of pocket cost will be lower, and my liability exposure will be less as well.

Lloyd

[NahanniV]

Originally Posted by Maine Sail

The analyzer is an Argus 500 specifically designed for testing batteries.. I just tested it again, on the large aluminum nuts, instead of the SS bolts, and got .58 mΩ...
.....

Man you have some nice equipment !

The value quoted by Winston is a per cell value and is a maximum.

Your tester uses a method similar to the one diugo suggested, except the load (100A) is applied in a 1mS pulse:
http://www.skandinaviskenergiteknik...._brochurer.pdf --- See large pulse resistance.

It seems to me that unless you are using the same test equipment and procedures the resistance values are only good as a future baseline. I.E. if you periodically test in the future and the resistance starts to rapidly increase it might point to a problem.

[deckofficer]

50 hours, 1500 watt-hr, cells reading 3.29, 3.30, 3.29, 3.30.

[Maine Sail]

Originally Posted by NahanniV

It seems to me that unless you are using the same test equipment and procedures the resistance values are only good as a future baseline. I.E. if you periodically test in the future and the resistance starts to rapidly increase it might point to a problem.

I mostly use these testers with baselines, then going forward. I do keep a note book with known good test results of a bunch of batteries so if I don't have baselines I can make a pretty good WAG on condition even without a baseline. The Midtronics is more accurate than the Argus, better and more up to date algorithms, on CCA / MCA, but the Argus is much more portable than my EXP-1000HD. Sadly you can no longer buy the Argus 500 in the US. Midtronics sued them for pinching their patented technology, and won.

I plan to cycle my bank a few times, count the Ah's, and re-charge, discharge, and it will be interesting to see if the resistance readings change. I am now repeatably getting .58 mΩ. It did not like being clamped to the SS bolts...

[diugo]

Originally Posted by senormechanico

Battery weight is never a good thing in a boat, even in a submarine.

A quick, fun comparison of AGM vs LFP, without all the usual "cycle" promises.

New 6V 300Ah Lifeline GPL-6CT AGMs now cost about $420 delivered, so two of them come to $840---which is almost exactly what I paid for my four 260Ah Thunder Sky LFPs ($848). So AGM cost is no longer an advantage.

In terms of usable ampere-hours, the AGM can be discharged 50%, so that's 150Ah. The LFPs can be discharged 80%, for 208Ah. Cost per usable amp-hour, $5.60 for AGM vs $4.09 for LFP. LFP is 27% cheaper.

In terms of volume, the AGMs are over 30% larger. In terms of weight, 180lb AGM vs 76lb LFP. AGMs weigh almost 2.4 times as much! It was a nightmare extricating each 90lb AGM from the tight space under my RV sink. The 19lb LFP cells were MUCH easier to maneuver.

I'm really beginning to like my LFPs

[diugo]

Originally Posted by Maine Sail

Good news is that both my Midtronics and Argus analyzers are showing this 400Ah battery producing more than 4800 cranking amps.

The good news about the high internal resistance is that it now eliminates the need for a fancy $100 telecom fuse. At 8 millohms for my battery (1500A max current), even my shunt trip circuit breaker's 5000A DC interrupt rating is more than adequate.

[deckofficer]

And like you said Doug, your not even factoring in cycle life, but I will, 500 vs 2000. But on this subject, I am curious how it stacks up to 6 volt golf cart batteries. 230 a-hr Sam's Club (always was the least expensive) $100. So $400 for 4, 12 volt 460 a-hr. Balqon 400 a-hr is $258 X 4 = $1032. 460 X .5 = 320 usable a-hr, Winston 400 X .8 = 320 usable a-hr. Not counting cycle life, golf cart @ Sam's still is the low price leader but crunch cycle life, $0.51 per cycle Winston, $0.80 per cycle Sam's golf cart batteries.

[Maine Sail]

I had 92A pulling on my bank for 30 minutes and the battery was still at 13.08V, after 30 minutes.. Impressive stuff....

They really do hold a voltage.... I let them sit for a little while after the load and measured cell voltages.

Near perfect balance (Fluke 179 DVM)..

Cell #1 = 3.334V
Cell #2 = 3.336V
Cell #3 = 3.337V
Cell #4 = 3.336V

Tomorrow or Saturday I will capacity test & do a few more cycles then they are ready to be assembled for installation..

[deckofficer]

What was the 92 amp load?

[Maine Sail]

Originally Posted by deckofficer

What was the 92 amp load?

Ceramic disc heater through an inverter... It's a cheap inverter & craps out if I run the heater on high, but I can get it to about 92A and it will hold there and won't trip the inverter on over load...

[deckofficer]

I used to run a 13,500 btu A/C off my Trace 2012 and (8) 220 a-hr 6 volt batteries. Could do it for a little over 4 hours, enough time for socializing and 4 rounds of bridge. My boat was popular in the Sea of Cortez 20 years ago. Now most have an AC gen set capable of running a couple of A/Cs.

[deckofficer]

My numbers were bogus. My multi color LED light when placed on the "run through all the colors" pulled different wattage depending on the color. I guess I should have known that, but when the 50 amp charger tapered to 38 amps after just 37 minutes I realized my load couldn't have been a constant 30 watts. Put the amp meter on it and saw it swing from 0.89 amps to 3.08 amps depending on the color. So 11.8 watts to 41 watts. Hot pink happens to be the highest draw. When I first got this light, they forgot the remote and it was on hot pink, so I did my first draw down at 41 watts. Because of this, that draw down that I thought was at 30 watts and showed the battery only delivered 980 watt-hr, it really delivered 1340 w-hr.