Custom LiFePoO4 question

[bdserv]

Originally Posted by stondini

I have a lifted 2017 CCP running 22" tires, stock controller and stock motor.

After going back and forth a few times between 280Ah and 150Ah I finally decided to build my pack out of 3.2v 150Ah batteries, mainly due to space.

The plan is to build the batteries in series for a 48V 150Ah battery.

Now the last part - how do I charge the thing. I have the stock ERIC charger and a quick visit to the mfg website says not to use them on Lithium batteries. For those who have built batteries, which chargers are you using?

I am in the same boat as you and heading in the same direction. Also bought my batteries from Mike on the DIY Solar forum.

I have a DPI charger that has a mode for LFP so I plan to give that a try for a charger.

I am waiting to hear back from the supplier on the need to top balance - these are matched cells so if they arrive at essentially the same terminal voltage I am thinking I will just build the 16S pack and bulk charge from the get-go. If they are all too different from each other then I will have to buy a decent benchtop power supply to top balance.

From what I have seen so far, balance currents from the BMS are minimal and only practical for small cell-to-cell differences, so if balancing is needed the BMS is probably not going to be a practical approach.

[stondini]

What voltage delta would necessitate the need for a bench charger? Asking for a friend

[bdserv]

I've been told that you can't really determine SOC strictly from terminal voltage because the discharge curve is so flat, so it's a good idea to top balance so that you have a known starting point for all the cells. That's my plan at this point.

[Pat911]

Correct. The only accurate way to know SOC is with a coulombmeter. Plenty of external units but many smart BMS’s also include a coulombmeter.

I use this one. Renogy Battery Monitor

Cheers
Pat.

[stondini]

https://www.aliexpress.com/item/4001...32da4c4dIgWUpi

That's the BMS I'll be using - I don't want to skip steps but would like to avoid buying something I'll use one time.

[Pat911]

That BMS will be ok as long as 200A continuous is enough for your cart.