# Can I use a 48V battery to pull power from on a 12V battery solar system?

Registered Users Posts: 1

Quick question guys! If I have a 12V battery solar system, can I use a 48V battery to pull power from once my 12V battery starts to get low?? So in other words once the 12V battery gets low can I parallel tie it to the 48V battery as long as I’m not charging the 12V battery. Will it allow the inverter to run while the 12v battery is pulling power from the 48v battery??

• Registered Users Posts: 4,495 ✭✭✭✭✭
I wouldn't recommend doing it directly.  With that much potential difference, the full 48v bank at ~51v vs reasonable charging voltage of ~14.5v.  Unlike a solar panel with a Vmp of ~18v, a battery bank can put out very large current, potentially damaging the batteries and/or connecting wiring.

To do it safely, you'd need something in between the batteries to reduce voltage and control current.
Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
• Super Moderators, Administrators Posts: 32,015 admin
Welcome to the forum Easy,

If I understand your question correctly... Yes, you can pull energy from one system and transfer it to another. The power can be used to charge the 12 volt battery bank, run the AC inverter and DC loads, or both.

However, you need something to convert the voltage/current from the 48 VDC battery bank and safely/properly convey it to the 12 VDC battery bank.

This can be a 48 to 12 VDC converter, it could be a battery charger (48 VDC to 12 VDC, or even a 120 VAC charger from your 48 volt bank to the 12 volt bank), or even a "power resistor" acting as a ballast to keep the current from getting too high (works, but you lose 75% of teh energy during the transfer--as waste heat in the ballast resistor).

As always with solar and power, the details matter. How much energy/current do you want to transfer, is this something you want to automate, or what...

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 5 ✭✭
This is not recommed to do. will have too many problems

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