Initial Charging of Parallel Battery Banks

[alferz]

One thing I haven't been able to find much in the way of recommendations for, is how you should go about the initial charge and syncing of two batteries prior to cycling them in parallel. Is there a step by step process you follow to do it? I know some of the basics, like pre-charging both to the same voltage. But the nuances like how long after charging to let them sit, whether to charge or discharge the parallel pack after initial sync, things that can go wrong or to watch for etc. Maybe none of the details matter and the batteries will just balance each other out quickly? Any pointers here appreciated!

 

[time2roll]

In parallel it is a minor detail to get them within 100 mV and connect. Can immediately put them in service to charge or discharge together.

 

[sunshine_eggo]

One thing I haven't been able to find much in the way of recommendations for, is how you should go about the initial charge and syncing of two batteries prior to cycling them in parallel. Is there a step by step process you follow to do it? I know some of the basics, like pre-charging both to the same voltage.

I'm good with 0.2V

But the nuances like how long after charging to let them sit,

No point in that. Charge to absorption, hold for two hours. If the BMS doesn't trigger protection, good to go. If it does, hold them at 13.8V for 24 hours.

whether to charge or discharge the parallel pack after initial sync,

If that's how you're going to use them, that's fine. If you want to get individual results, test them individually.

things that can go wrong or to watch for etc.

Overthinking it.

and the aforementioned BMS protection. Not at all uncommon with packaged batteries - one or more cells hit full before the others, and it needs some time to balance.