I'm currently working with two EG4 indoor power pro batteries connected in parallel, as specified in the manual, and they're managed by an off-grid 12000XP. Now, I'm looking to add a third battery, but its placement requires longer cables than what came with the initial setup. I'm contemplating a few options: I could either fabricate longer cables to parallel the third battery, insert a bus bar between the second and third batteries, or reconfigure everything and use a bus bar for all three. My main goal here is to maximize storage to handle outages, especially since my panel capacity is somewhat limited. I'm curious about opinions and reasons for preferring one option over the others.
2 Answers
Using a bus bar with equal length cables connecting all three batteries is definitely the way to go. I found a helpful guide by Victron on wiring that goes into more detail: [Victron Wiring Guide](https://www.victronenergy.com/upload/documents/The_Wiring_Unlimited_book/43562-Wiring_Unlimited-pdf-en.pdf)
You're right to consider cable lengths and resistance. Keeping them equal ensures that charging is balanced across the bank. You might want to check out the resistance of different wire gauges to see if the length difference to the third battery is significant. If your setup allows, rotating the third battery every so often could help keep them balanced, though with 300 lbs each, that might be a challenge! I’m going for a similar setup and am considering running longer leads from the ends for + and - connections instead of a bus bar.
Yeah, I'd rather avoid moving those heavy batteries! I've only about 12 inches of extra cable length—do you think that's enough to matter since most resistance charts refer to meters?
Yeah, making sure the cables are equal length is key to getting balanced power draw from each battery.