Car battery as panel input?

[John.DS99]

There are times when my solar panels are providing power, but the batteries are full. If you had a spare car battery, you could charge it up.

Would it be possible to use that car battery as a substitute for solar panel DC input later in the day if you had depleted your main battery?

 

[SamDeleted]

Do you mean through a solar charge controller?

Essentially using it as a DC-DC converter

If it's MPPT then yes it's possible but the car batteries voltage has to be within the start up range of your mppt

Also it's not going to work if you're trying to move 12v to 12v , because your main battery bank would need 14.5v~ to charge, while your car battery even full would be around 12v under load ... 99% of MPPTs only step down, they don't step voltage up

It works great for 24v > 12v , 48v > 12v ect.

 

[SamDeleted]

Question: DC/DC converter, SCC

I'm trying to charge a 24vdc AGM battery bank from a 48v agm battery bank, I've had my eye on a 110w victron dc/dc converter, £70~ But was wondering if it's possible to use a solar charger controller as a DC/DC step down converter ? I've got a spare STECA MPPT or two , 15amp, 100v max solar...

diysolarforum.com

It's actually a question I asked not so long ago

 

[John.DS99]

On my cheap little system it is a powerstation that has solar inputs. When the battery is full I was thinking if I had a car battery I could use the dc outputs to charge it and use it in some way later such as solar panel input after the powerstation battery was depleted.

Just thinking, not knowing anything.

 

[SamDeleted]

Charging one battery from another using a Solar charge controller?

I had an idea of how to charge one battery from another with higher voltage until their voltage is equal. Connect the one with lower voltage at the batter connection of a Solar charge controller like normal. Connect the higher voltage battery to the solar PV input. As I understand it, Solar...

diysolarforum.com

 

[SamDeleted]

Have a read of that , Will the owner of the forum doesn't recommend it , others say it works just fine


It's been talked about a lot on here, different options

 

[SamDeleted]

MPPT as Battery to Battery Charger? - Victron Community

community.victronenergy.com

 

[John.DS99]

Thank you Sam