I have 2 AGM 12V 125ah batteries I want to use parallel. They are right next to each other (so wire to be <a foot). 1200 watt inverter (more than I'll likely need), 50 amp MPPT/DC-DC charger, 3x100 watt solar panels, 12V refrigerator (plus usual led lights, fan, charging ports). Question: the 2 cables (+/-) should be what gauge? The inverter came with 4 gauge. The guy at local NAPA said that would do for joining the batteries as well. I read other on-line comments saying you need much bigger cables for the batteries. I find the wire sizing charts confusing. Can someone experienced just tell me what size I need?
Batteries in parallel
- Thread starter MJRW
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[font=Tahoma, Verdana, Arial, sans-serif]Don't know why my post (above) was cut off. Here it is in full:[/font]
[font=Tahoma, Verdana, Arial, sans-serif]I have 2 AGM 12V 125ah batteries I want to use parallel. They are right next to each other (so wire to be <a foot). 1200 watt inverter (more than I'll likely need), 50 amp MPPT/DC-DC charger, 3x100 watt solar panels, 12V refrigerator (plus usual led lights, fan, charging ports). Question: the 2 cables (+/-) should be what gauge? The inverter came with 4 gauge. The guy at local NAPA said that would do for joining the batteries as well. I read other on-line comments saying you need much bigger cables for the batteries. I find the wire sizing charts confusing. Can someone experienced just tell me what size I need?[/font]
[font=Tahoma, Verdana, Arial, sans-serif]I have 2 AGM 12V 125ah batteries I want to use parallel. They are right next to each other (so wire to be <a foot). 1200 watt inverter (more than I'll likely need), 50 amp MPPT/DC-DC charger, 3x100 watt solar panels, 12V refrigerator (plus usual led lights, fan, charging ports). Question: the 2 cables (+/-) should be what gauge? The inverter came with 4 gauge. The guy at local NAPA said that would do for joining the batteries as well. I read other on-line comments saying you need much bigger cables for the batteries. I find the wire sizing charts confusing. Can someone experienced just tell me what size I need?[/font]
B and C
Well-known member
The wire size tying batteries together has to be a minimum size able to handle your highest draw. Most people use 4 Ga unless you're connecting a large inverter. Be srue to connect your positive load/charge to one battery and the negative to the other battery.
It is best to use large cable sizes to connect the batteries, either series or parallel as yours. I would never use less than 2/0 cable between batteries. The main objective is to reduce voltage drop in the battery bank. Then, The individual devices can be wired with the smaller awg if appropriate for their ampere draw. And fuses at the positive battery terminal.
B and C
Well-known member
Anything connected to positive needs a fuse as close to the battery as feasible except for the cables tying the batteries together. It just becomes one bigger battery at that point.
