Lifep04 batteries and balancing

I keep seeing things that mention these batteries don't need to be balanced.

Why is that?

I almost never seen the bank showing above 13.2v, but when I have an individual battery on charge, it will hit 13.7 after charging stops.

I assumed this was because one (or more) of the batteries was low and I'd need to separate them and charge each to full on its own and possibly see if one isn't working right.

Typically when you fully charge your batteries up they will balance on their own both internally and with other batteries in parallel.  The most important thing is to ensure that the battery cable length is exactly the same for each.

Crinstam Camp wrote:I keep seeing things that mention these batteries don't need to be balanced.

Why is that?

I almost never seen the bank showing above 13.2v, but when I have an individual battery on charge, it will hit 13.7 after charging stops.

I assumed this was because one (or more) of the batteries was low and I'd need to separate them and charge each to full on its own and possibly see if one isn't working right.

This doesn't sound right. 4x3.2v cells should charge to  3.65v per cell at full charge 3.65x4=14.6v  the key is keeping them between 80 and 30% for the longest life.

According to the battery manual, during charging they should come up to 14.6. Full charge at rest should be 13.6.

I have the 6 batteries in parallel (edited to fix brain fart) 3 down three up with batteries 1 and 6 beside each other. All the cables are identical to each other, as are the connectors.

The inverter and solar charge controller both hook to the positive on battery 1 and negative on battery 6.

The AC charger from our generator is positive on 6, negative on 1.

The only time I've ever seen them over 13.2 is when I charged them separately, although I haven't done all 6. Last time was when we still only had 4.

I'm thinking I likely should charge them up for a bit then pull them apart and test each one. Maybe one is faulty or something?

They say they don’t need to be equalized because the BMS battery management system is supposed to do that for you. If you built your own from individual cells, you need to get a bms for the total voltage and number of cells you have.

Do not buy premade battery banks and hook them in series to get a higher voltage, buy the right voltage and hook them in parallel if you need more amp hours

R Scott wrote:Do not buy premade battery banks and hook them in series to get a higher voltage, buy the right voltage and hook them in parallel if you need more amp hours

I meant parallel, however, according to the manufacturer, hooking them in series to increase the voltage is fine, why do you disagree?

Most the batteries I looked at recently specifically said not to. It is possible they have a BMS that will equalize in that configuration, but the guys I knew that tried that configuration had problems. They were using big name batteries, not random Amazon word salad brands.

Been looking into this issue for my electric golf cart and UTV.  In general, it appears that the online community with whom I interact seems to agree that it's better to get a battery of the voltage desired for the system and then parallel connect batteries of the same voltage in order to increase Ah ratings of the system.   Series connection of lower voltage batteries to achieve the voltage desired has some advantages, but for most people the finicky nature of battery and/or cell balancing may not be worth the hassle.  The reason I'm weighing these two options has to do with winter:  The golf cart and UTV are stored in an unheated garage that will easily see many nights of -20 to -30 degrees F.  If I were to shell out enough cash, I could purchase the higher end LiFePO4 batteries that have bluetooth monitoring -AND- and heating circuit to make sure that the batteries are pre-heated before the charging cycle begins.  But if I were to choose series-connected 12V batteries,  removal of batteries from the cart (~20 - 30 lbs each) to store in the house during cold weather would not be so difficult.  But it also would be more crucial with this arrangement to monitor balance between the batteries in the array as well as the cells within each battery....so a phone app that provides this information from the battery BMS would need to provide that.  At this point, I've found one provider whose 36V/50Ah battery will just squeeze into the space currently occupied by 2 of the 6V lead acid batteries powering the cart.  For the 12V option, many suppliers sell "GC2" golf-cart replacement size LiFePO4 batteries that would require the series connected configuration.  So there are several factors to weigh in this decision, but to echo R Scott's comments, 'the community' seems to agree that parallel connection of batteries, each of which already are at the desired voltage for the system, is the more robust way to go.  At least at this point in time....

Well without an actual reason beyond "some guys" and "the community" as to why it's bad, I'm going to have to go with the manual that came with them.

But hey, if anyone wants to buy me a new a set of 48v batteries, I'll be more than happy to use them.

What brand battery are you using? LiFePo batteries have some sort of battery management system (BMS) inside, and different BMS's operate differently.

Daniel Schmidt wrote:What brand battery are you using? LiFePo batteries have some sort of battery management system (BMS) inside, and different BMS's operate differently.

Timeusb 12V 100Ah LiFePO4 RV Battery Pro

"Flexible Connection Options: Supports series, parallel, and series-parallel connections. Enables the storage of a massive 20.48 kWh of energy utilizing 16 x 12V 100Ah batteries configured in a 4P4S connection."

https://www.timeusbpower.com/products/12v-100ah-pro-lifepo4-battery

So, it mentions in the manual that you shouldn't have more than 4 in a parallel set.

I emailed the company and asked them about having 6 in parallel.

This is what they said.

Timeusb wrote:
Using more than the recommended number of batteries in parallel can lead to several issues. When you connect 6 of the "Timeusb 12V 100Ah LiFePO4 RV Battery Pro" batteries in parallel, you may experience imbalances in charging and discharging. This can result in some batteries being overcharged while others are undercharged, potentially leading to reduced battery life, performance issues, or even damage to the batteries.

To ensure optimal performance and longevity, it is best to adhere to the manufacturer's guidelines, which recommend a maximum of 4 batteries in parallel. If you need more capacity, consider using additional battery banks or configurations that comply with the specifications.

If you have already connected 6 batteries, I recommend monitoring their performance closely and considering reconfiguring your setup to align with the recommended guidelines. If you have any further questions or need assistance, feel free to reach out

I still don't understand why it should matter, but tomorrow I'll unhook it all, charge the batteries up individually, hook 4 up parallel, let them sit for 12 to 24 hours and then hook them back into the system.

It sucks that we'll have two batteries just sitting here waiting until we get two more, a new inverter and charger for 48v, but I don't see what else I can do.

I disconnected them all and tested each one. They were all within 0.1V of each other, which would seem to indicate I didn't have a balance issue?

I'm charging each one up separately to 13.5V which is what the manual says is 100%. I'll leave each on 30 minutes after it hits that then move onto the next. I'll test each just after they come off charging then again an hour later after they rest.

Assuming I get four that get up to full charge I'll hook them together in parallel, on their own overnight, test them again and if they're still all good, hook them back into the system and see what it shows.

Okay, I'm only part way through this but I thought I'd update and ask a couple of questions.

The battery bank was showing 13.1 when I pulled it apart. After letting them sit for a while I tested each one and they were all at 13.1 or on the verge of it. As in some showed 13.0 switching to 13.1 back and forth.

So I started charging each individually. I let them rest for an hour before testing.

1 of them came up to 13.5. On this one, the charger was only putting out 1 amp by then end.

1 of them came up to 13.4
2 of them only came up to 13.3.

With those 3, the charger was still putting out 50amps when I unhooked it, but the battery voltage hadn't changed in over an hour.

I'm going to continue charging today.

When I get through the other two I'm going to put the low ones back on charge.

Should I just leave them on it longer? If so, how long?
Should I change the amperage for charging them? If so, to what?

I got 4 of the batteries to full charge at least today.

The manual says 13.5 is 100%

13.5, 13.6, 13.7 and 13.9 is what the batteries tested at after sitting for over an hour after charging.

I hooked them all in parallel with no charge or load on it and will leave it like that until tomorrow when I'll unhook and test each one again before hooking them into the system.

They test out at 13.6 as a bank right now.

After letting it sit until about noon the next day, the bank was testing at 13.5 and when I pulled it apart, each battery was at 13.5.

I hooked it all back up and depending on the meter/tester I looked at, it showed 13.2/13.3.

We didn't have very much sun yesterday, way too much smoke from the fires out west, so I didn't get to see if it would come up at all, but in the morning before the sun came up they all read as we 13.2.

Last night after the sun went down they were showing 13.2/13.3 again.

This morning they were again all showing 13.2

I'm still confused how I can get different readings on every damn meter I use and why it dropped from 13.5 to 13.2/13.3 just from hooking it up, but it's definitely holding charge better now than when I had the 6 batteries hooked up.

I don't know if it's just because they were all properly balanced or if it's because their BMSs just work better with only 4, but I'm happy it's better.

At some point I may try balancing all 6 and hooking them up again to see what happens but for now I'm happy with the improvement.

Usually with these type of batteries, you're buying from a company where they are buying from the another source, which is why they can't give you the exact reason on why you shouldn't connect more than 4 batteries in parallel.

Crinstam Camp wrote:
I'm still confused how I can get different readings on every damn meter I use and why it dropped from 13.5 to 13.2/13.3 just from hooking it up, but it's definitely holding charge better now than when I had the 6 batteries hooked up.

The issue is you're experiencing may be related to the built-in BMS and balancing.
Inside each battery is a set of 4 more batteries that are being balanced. These bms usually have a slight parasitic draw and will usually have what is considered 100% balanced at a level lower than the max voltage of the battery. This is to prevent batteries from getting damaged by overvoltage.

The 13.5 to 13.2 drop that you're experiencing is probably occurring while the bms is still balancing. If you search the internet, you'll find some people set their bms to consider their DIY solar pack at 100% when each cell is balanced at 3.3v. Which is close to the voltage range that you are seeing at 13.2/13.3 volts. Unfortunately, you will not be able to diagnose this without opening each pack, which I don't recommend since your batteries have a 5 year warranty.

However, the next best thing you can do is a lifepo4 capacity tester. This will allow you to check the overall capacity of each battery individual battery bank, help determine which battery is the weakest and by how much.

Crinstam Camp wrote:The manual says 13.5 is 100%

Usually LiFePO4 documentation say charged to 14.6. I charge mine to 14v.

13.5-13.6 is the 100% resting voltage.

LiFePO4 batteries are known for their relatively flat voltage between 10-90%, ie. 13.2 could be 70-80% full.

For individual cell voltage it doesn't start getting out of the flat part of the curve until above 3.4. So biased on video of testing, I don't have balancing start until the cells are above 3.45.

My guess the reason you don't want a lot of parallel batteries is that a 13.3 battery won't charge the 13.2 next to it because it doesn't have "force" to get over the internal battery resistance. That is the reason charging voltage isn't the same as full voltage. Instead small amounts is current goes between the batteries and is turned to heat by the resistance of the wires and the batteries. The more batteries in parallel the worse the problem.