Parallel Different SoC LiFePo4 Batteries?

There's a lot of lore & myth around why manufacturers tell you to get LFP batteries to the same voltage before wiring them in Parallel. The myth & Lore suggests it is because you will blow something up. That's not why they tell you this. In this video we parallel a 400Ah LFP pack at 100% SoC with a 10Ah pack at 0% SoC.

[@hjboven]

Hello mr. Marine How to, glad to see you online and are doing better. I learned so much from you via your website. Thank you for your curiosity trying to figure out how lifepo works. It made me go the lifepo way and I never regretted it.

[@koffibanan3099]

Hey Rod, I didn't realise you suffered a stroke! Glad to see that you look absolutely fine and you are back in your lab testing things, busting myths :)
Keep well and all the best!

[@toddsawicki]

Great video thanks Rod!

[@mvintrigue-trawlerdiy1101]

Good video, very informative. Thank you!

[@mckenziekeith7434]

In addition to the battery internal resistance, the wires have some resistance. While small, it may be significant compared to the internal resistance of the smaller battery. So not negligible. Anyway, I am glad you did this because I have been wondering just how large the currents would be. For example if you have an emergency parallel switch on a boat to parallel the house bank with the starter battery, do you need to worry about the inrush current? Based on this, I would say probably not.

[@RechargeableLithium]

Good to see you back, Rod! There's nothing wrong with your voice. 👍

[@haydenwatson7987]

I agree. Rod, you don't sound any different than I do in the morning, and I have no excuse other than getting old.

[@xhumeka]

I suppose if you tried to parallel two of your 400 Ah batteries with the same state-of-charge difference the results would be much different, correct? In that scenario I guess the BMS would trip due to the very large surge current? Thanks for a great video!!!

[@mrl22222]

I have a battery made of 4 CATL 100a cells dated 6/2013. It just tested at 97ah. In 2013 it tested at 101ah. .