Re: [electricboats] Cells seem to have stopped increasing voltage when balancing

Thanks Bob. I will check that out.

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Re: [electricboats] Cells seem to have stopped increasing voltage when balancing

Peter.

You're balancing a batch if cells identical to the ones I recently finished capacity testing, recharging, and balancing as my new pack.

My ThunderStruck chargers and related monitoring gear were already installed on the boat, so on my test/work bench at home, all I had to use to recharge each cell after drawing it down were a 300 watt variable voltage power supply, and a 12vdc, 30 amp Lipo charger.

My target pre-install balance voltage for each cell was 3.55v starting from just under 3.00v.

My work flow for each cell was to do a discharge test (end state of ~2.7v recovering to ~3.0v) and use the variable power supply to bring the cell up 3.2v or so while the next cell was being discharged.  As each cell completed that cycle, I connected it in parallel with the previous cell such that I had 4 cells at roughly the same 3.2v.  After the four cells had some time to balance to one another (checking each cell with a good multimeter), I reconnected them into 12v series and attached my 30amp, 12v Lipo charger.  The 30a charger pumped more watts per cell than my 300 watt variable power supply could.

Once the cells were just over my target voltage, I took the 4-pack apart and reconnected them in parallel once more.  The next 4 cells went the same way, then I had 8 cells in parallel at my target, and so on thru the 16 cells.

If you don't have access to a 30+amp charger running at 48+volts, and are limited as I was to a low-watts power supply, or a 12v 30amp charger, then grouping them into 12v packs can take less time.

Whether discharging or charging, these cells will sit at around 3 3vdc for most of the cycle.  The like all Lipo cells, the discharge curve is quite flat between about 15% SOC and 90% SOC.

It's important to closely monitor each cell individually while charging to avoid exceeding 3.65v.  Once they get to ~3.55v they can climb pretty quickly to max allowable.

The equipment you're using is different than mine, and it seems youbare starting from a higher SOC for each cell than I was in my process.  So you'll have to make appropriate adjustments.

Be safe; have fun!!

[-tv]

 

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Re: [electricboats] Cells seem to have stopped increasing voltage when balancing

A FLIR infrared cam on your smartphone could easily show temperature differences during charging.

I have a small thing called FLIRONE PRO. Very efficient, very useful. Snaps into the USB-C gate on your phone.

On Monday, 14 October 2024 at 06:11:26 CEST, bobkart <couch45@msn.com> wrote:

It doesn't seem like that will speed things up.  The same amount of energy needs to go into the battery with either approach.  Sure, you'll see one four-pack get there more quickly.  But getting all sixteen cells full will not go more quickly.  It will go a bit more slowly due to the regrouping of cells (and self-discharge on four-packs not being charged).

 

I suspect you could use more power.  In the other thread, I suggested MeanWell's RSP-500-4.  Yes it costs more.  It's a spend-more or wait-longer tradeoff.  Not counting delivery time for the better charger.

 

Another possibility is that you have damaged-cell issues.  You may want to check for one or more cells being warmer than the others.  They could be 'sinking' current.  Although at the low level you're charging, you might not be able to tell the difference just by touching them.  At 100A the difference would be more obvious.

 

 

Re: [electricboats] Cells seem to have stopped increasing voltage when balancing

It doesn't seem like that will speed things up.  The same amount of energy needs to go into the battery with either approach.  Sure, you'll see one four-pack get there more quickly.  But getting all sixteen cells full will not go more quickly.  It will go a bit more slowly due to the regrouping of cells (and self-discharge on four-packs not being charged).

 

I suspect you could use more power.  In the other thread, I suggested MeanWell's RSP-500-4.  Yes it costs more.  It's a spend-more or wait-longer tradeoff.  Not counting delivery time for the better charger.

 

Another possibility is that you have damaged-cell issues.  You may want to check for one or more cells being warmer than the others.  They could be 'sinking' current.  Although at the low level you're charging, you might not be able to tell the difference just by touching them.  At 100A the difference would be more obvious.

 

 

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Re: [electricboats] Cells seem to have stopped increasing voltage when balancing

After doing this balancing for about 10 days and still a long way from 3.65v , and doing some more research, I am wondering about splitting the 16 batteries up into groups of 4 and then charging them, with a 12v LifePo4 charger, to 3.55v, which will take about an hour or two for each group of 4, which are now at 3.310. Then top balancing them to 3.65v. From what I have read LiFePo4 batteries flatline and increase a tiny bit at a time, until they get close to the target voltage, 3.65v, and then the balancing happens a lot quicker. The batteries are at 3.310 now, and they were at 3.27v ten days ago. If charging them in groups of 4 to 3.55v and then putting the 16 back in parallel to balance to 3.65 is an acceptable method I will do it and it will save me a lot of time and accomplish the same thing. I hope. Whatever thoughts you have would be appreciated. Thanks in advance.

Peter


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Re: [electricboats] Cells seem to have stopped increasing voltage when balancing

Thanks. Will check out those you tubes. I started the balancing at 3.27v. Only because that was their voltage when I got them 3 years ago.

Peter


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Re: [electricboats] Cells seem to have stopped increasing voltage when balancing

You have 4,480 ah at 3.2 volts. Sounds like you are putting in 3.52 amps? If your batteries are at 50% SOC you need to put in 2,240 ah. At 3.52 amps it will take 636 hours or 24 days! Sit tight. 

Matt Foley

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On Oct 12, 2024, at 10:09 AM, shredderf16 <Shredderf16@sbcglobal.net> wrote:



Peter,
   No clue. I just did the math and based on your voltage and amp readings (12 watts coming in) and came up with 7 days. The last time I did this myself it was a week to 10 days. Longest I've heard of from one of my buddies was 2-3 weeks. It really depends on the SOC when you first parallel them. Will Prowse on You Tube has a couple of videos on this. Watch them and maybe he's got some insight.
Jerry

On October 12, 2024, at 8:37 AM, Peter Knowlton <pqknowlton@gmail.com> wrote:

Since this group has provided me with the soundest advice I am coming back for some more, on a similarly related issue dealing with balancing my 16 Eve 3.2v 280 ah LifePo4 batteries. I purchased a dc power supply as advised. Charged the cells to 3.27, give or take, and then put the 16 cells in parallel. That was 10 days ago.  Put the dials at 3.7v and 3.52 ah. They are all now at 33.09v after 10 days, although the two end batteries are 3.10v. That is probably fine as it goes but here's the issue I need advice on: The batteries have not advanced from the 33.10/33.09 for over a day now. Every day before this the battery voltage would increase only a few tenths of a volt, but there was a steady increase. However, with no increase in the last 24 hours I am wondering if they are topped out, despite what I'm reading and seeing from others that they should be balanced to at least 3.5v. Any ideas why they might be "stalled" or are they topped out? Should I just patiently wait a little longer to see what happens or does no change in the last 24 hours mean they are topped out and ready to go? Thanks for whatever ideas you have.

 

Peter