Paralleling Batteries prior to putting them in series

[whatismouse]

Ok I received one 24V lifepo4 pack back from warranty, the other one I have that didn't get sent in for warranty is at a lower state of charge. They differ in voltage by 0.7V. Prior to putting them in series for my 48V battery bank, I decided to put them in parallel using the same resistor I bought for pre-charging inverter capacitors. It is, however, a 50ohm resistor, and thus limits the amperage of balancing to 0.01amps. So not wanting this to take forever, can I just hook them up in parallel without a resistor? What kind of amperage would I see if I were to do this?

 

[BarkingSpider]

Years ago, I synced my two BYD packs with thick car jumpstart cables. Even with that, the cables got really hot and the plastic went soft on the cable handles, it was scary. Even a fraction of a volt difference between the packs can mean a huge inrush of power. To avoid that, Charge/Discharge as necessary both the battery packs so they are close as possible voltage wise, ie 3.2v. Then connect them in parallel directly to the battery terminals with jump start cables. Let the voltage settle for a few minutes, only then consider connecting the two pack together permanently. Take your time or you will blow your BMS.

 

[whatismouse]

I don't have a 24V charger...

 

[whatismouse]

Could I short the higher voltage battery with the same resistor until the voltage drops by .7?

edit: its a 10watt resistor so if there is a 26.3V difference between the terminals, i =v/r , i = 26.3/50ohms; i = .526 amps, * 26.3V = 13.15 watts,

so i guess no, because I would exceed the wattage of my resistor?

Or I could put two resistors, dropping wattage to 7.5?

 

[BarkingSpider]

I highly recommend this charger, and they gave me a $35 rebate amazon card! I use it to charge all my batteries.

https://www.amazon.com/gp/product/B08DJ1FDXV/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

 

[BarkingSpider]

Just put them in 48v series and let the BMS do its job. No need to parallel them.

 

[whatismouse]

each 24V battery has its own bms...so I don't think this would work. Correct me if I'm wrong.

 

[whatismouse]

I highly recommend this charger, and they gave me a $35 rebate amazon card! I use it to charge all my batteries.

https://www.amazon.com/gp/product/B08DJ1FDXV/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

nice, I think I would go for the 60V in case my 48V battery bank ever goes below my inverter/charger minimum (I think 42V?) Had been looking for something in case that happens...

 

[Pyrofx]

Mine lasted 27 hrs. Then lights just went out. Totally dead machine