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

[diugo]

Originally Posted by 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.

Your multimeter may have a min/max/avg mode which you can quickly use to determine the average current across one or more color cycles. Then you can just multiply the average current by the number of hours.

[Maine Sail]

BTW an hour in to capacity testing, at 100A, and the battery is holding steady at 12.85V....



A 400Ah bank of FLA with a 1.27 Peukert would be seeing an equivalent load of 154A +/- and be significantly more deeply discharged than 100Ah....

[Maine Sail]

Just passed 300Ah removed from the bank (75% depth of discharge) and with a 100A load running, FOR THREE HOURS, the battery is still at 12.59V! Wow..!! Cells are all discharging evenly and are at about 3.14V each....

I will say that with no Peukert, capacity testing is easy, load it up, count the amp hours removed..... Simple...

Watching these cells perform, and actually heating my garage in the process, they are truly quite impressive. Oh and cell temperatures have not budged in three hours at a 100A load.

[deckofficer]

I'm starting over. The color I'm using for the LED light pulls 3.2 amps. I will run until I see a real knee, not computed w-hr. Then I will give it a real bottom balance (as it turns out, I've given it a mid and top balance only). Then I will charge in parallel at 3.9 volts, and with that small of a volt diff, will probably take 150 hours but should be very nicely balanced.

Sorry for sharing erroneous numbers based on my light's 30 watt rating, I should have confirmed the load before sharing a load of BS with you folks that are following this thread.

To the others that have shared your info, thank you. Maine Sail, thanks again for the link to the PS.

[Maine Sail]

Originally Posted by deckofficer

To the others that have shared your info, thank you. Maine Sail, thanks again for the link to the PS.

I LOVE my power supply. Just programmed a Balmar Duo charger today with it...... Beats doing it in a bilge.....

[deckofficer]

Maine Sail,

I never caught your first name. These are impressive cells. Even though I haven't had the chance for heavy amp draw like you have done, I did have an inadvertent heavy amp draw when for a split second this alligator clip accidentally shorted across just two cells. Talk about a solid spark at 6.4 volts. Won't have to worry about losing the screw on that clip, it won't be threading all the way out.

Over the years I've accidentally shorted my share of 12 volt LA deep cycle batteries and the spark was nowhere as energetic as this was. My hand was holding the clip, so I jerked it off quickly. I can't imagine what would happen if someone drops a wrench across the terminals for any kind of time frame.

[diugo]

LFPs happily charging under full sun. 16 amps net charge through 8.4 millohms internal resistance, so expected to see 16x8.4=134mV voltage lift, but saw 250mV instead. Difference is the thermodynamic penalty---the integrated area between the charge and discharge curves.

So looks like I will need to bump the charger setpoint from 13.6 to 13.85V to compensate. Nice to see the solar panels working at full capacity all day long for a change! Should reach full charge tomorrow, then I can start a discharge capacity test of my own.

Was also able to test the circuit breaker's shunt trip. The labelling says 5A @ 12V, but it came in well under, at only 0.6A.

[diugo]

Originally Posted by deckofficer

I did have an inadvertent heavy amp draw when for a split second this alligator clip accidentally shorted across just two cells. Talk about a solid spark at 6.4 volts.

Bob, those close terminals and the potential for a load of current is nothing to sneeze at. Here's a youtube video of a guy who's done a nice job with his Winston batteries:

Winston Battery powered solar system. Episode 06a - YouTube

But look what he does at 6:11 in the clip, almost completing a 6.4V circuit with his Rolex! Imagine if he had made contact and the watch welded itself to the terminals.

[FlyingCloud1937]

Originally Posted by Maine Sail

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...

Hi Main...

That begs the question? I see 3 dissimilar metals used to make the jumper connections. It's a number 1 sin to use copper and aluminum connection in the marine market, as the alum... will quick corrode.

Also what concern have you with with the big alum... nut as it expands and contracts at a different rate to the copper.

The Li-Ion bat uses copper foil for the negitive plates with the foil ends clamped internally to the alum... post, and the big alum... nut screwed with case between.

Now we also have copper connected to alum... in an electrolyte inside the battery. What about the corrosion issue, will it over time develop a high resistance? Will each cell develop equal resistance? How will that effect cell balance. And over what period of time?

Lloyd

[Maine Sail]

Originally Posted by FlyingCloud1937

Hi Main...

That begs the question? I see 3 dissimilar metals used to make the jumper connections. It's a number 1 sin to use copper and aluminum connection in the marine market, as the alum... will quick corrode.

Also what concern have you with with the big alum... nut as it expands and contracts at a different rate to the copper.

The Li-Ion bat uses copper foil for the negitive plates with the foil ends clamped internally to the alum... post, and the big alum... nut screwed with case between.

Now we also have copper connected to alum... in an electrolyte inside the battery. What about the corrosion issue, will it over time develop a high resistance? Will each cell develop equal resistance? How will that effect cell balance. And over what period of time?

Lloyd

Lloyd,

I will let you know when corrosion is an issue on my boat. This is my FLA bank at year 5. ZERO corrosion on batteries that "vent"..... It still looks just this good today... That is until I rip it all out in a few weeks and install the Winston cells....

In short I am not at all concerned about it as the EV guys throw these under the hoods of cars and drive them on rainy salted roads.... My battery compartment is a Ritz Hotel compared the the environment some of the EV guys put these through.....

[FlyingCloud1937]

Well it seems I was able to goggle a quick picture. While this isn't a Winston Cell it's a Shandong HiPower cell, presumably the Winston is similar.

Here is a link to the website of this photo Li-Ion BMS - Prismatic cells I think everyone interested in Li-Ion will find this site has good resources

Lloyd

[Maine Sail]

Holy COW!!!!!! I just completed my capacity testing and all I can say is WOW!!

She flew past 400Ah's like it was nothing. The load on the bank started at around 102A +/- and ended at 106A +/-. I ran the 100A+ load for over 4 hours straight and the pack voltage only bottomed out at 11.8V +/-. The lowest cell, about 0.01 difference than the others, only hit 2.93V.. The BMS board was not even close to alarms or LVC's..

I programmed the Victron BMV-602 battery monitor for a Peukert of 1.0 as Winston/Balquon said to. I then applied a 100A +/- load and simply counted the Ah's removed with the CE or consumed energy screen on the battery monitor..

This shot was taken as she passed the 400Ah mark.


This is where the Ah's were when the shot was taken.



I've worked on a LOT of boats and a LOT of battery systems but never, ever seen anything like this. This bank will have a very, very easy life on our boat compared to what I just did to it.........

I stopped the test at 425Ah's. Based on voltage it could have gone longer and produced more capacity. For "Clearance" cells that I paid $1032.00 for, less than Lifeline or Odyssey AGM's I am pretty impressed.

I also made a video to show the process that I will try to get uploaded.. I will likely never draw the bank this low again but boy was it impressive to watch....

BTW that $210.00 bank of "Wal*Mart batteries currently on our boat just ended its SIXTH year. They still test at over 90% of new Ah capacity and still exceed CCA and MCA with both the Midtronics and Argus analyzers.

How long do you think the LiFePo4's will last? I don't really care, as it is more for the education and experience, but I'd have to guess the way I will care for the bank I should easily exceed the Wal*Mart bank....

By then I'll be onto the next great technology, just because... The Wal*Mart bank will easily go another year or two if I wanted and most people would have never even approached three years. It's all how you care for stuff......

[deckofficer]

Originally Posted by Maine Sail

How long do you think the LiFePo4's will last?

I'm 60 and expect any LiFePo4 cells I buy will outlive me.


Maine Sail, since you are so well versed in batteries, and I over time with designing off grid power and EVs, we both see the amazing capabilities of these cells. Even at Balqon's normal prices, AGM, gel, flooded, NiCd aren't a good deal anymore. Nickel Metal Hydride I still use, but because the oil companies own the rights to all single cells > 10 a-hr, I won't be doing much with them.

[catakate]

Originally Posted by Lagoon4us

Google Translate

Very informative, albeit a translation. Picture shows a ruptured battery, not a huge issue!

Nice one, I have a similar charger from previous hobby, only need the batteries now

[deckofficer]

I was impressed enough with these cells to buy them. Then after a balance was really impressed with them exceeding their posted ratings until I found out my 30 watt load was not 30 watt. But now I'm back to being impressed. I measured the load on the color that drew the most amps (whitish pink) it was 3.7 amps. I knew this draw was higher than cycling through all the colors just because the heat sinks in the LED light fixture got quite warm instead of staying cool as it did cycling the colors.

Ran a 3.7 amp load for 39 hours which is 144.3 a-hr out of a battery rated at 100 amp. Cell voltage at this time were still above the knee at 3.20, 3.20, 3.21, 3.22, but I wanted to go to bed.

Bank is in parallel again and charging at 3.9 volts, 4 amps, should take about 100 hours to charge, and balance should be perfect. I can't wait to put the motor load of the kayak on these batteries, as all my calculations were not based on what these cells can do in the real world. At 3/4 cruising setting, the motor is drawing around 200 watts, so I expected just a tad over 5 hours run time at 5 kt, or 25 nm to 80% DOD. With how it has tested out, appears 25 nm will be easy. 50+ nm for the 2 packs.