Battery charging via mains and solar wiring

[Ghodula]

I have 4 x 100ah parallell & serial batteries @ 24v which I am charging via a 315w solar panel via a 20a mppt controller. Happy days.
I also have a basic 30a mains to dc charger and a spare 300a battery selector.

So I would like to hook up the + from the solar to one of the selector terminals and the + from the main charger to the other, so I can't have both charging simultaneously.

The question is what do do with the solar negative and mains charger negative. Can I splice them together?

 

[rogerthebodger]

The question is what do do with the solar negative and mains charger negative. Can I splice them together?

Yes

 

[JerryC]

The question is what do do with the solar negative and mains charger negative. Can I splice them together?

"Splice"??? Blimey, I hope this is just casual language! Yes you're right in principle to want to connect all the negatives together, but please do it properly ...

Hopefully you already have a massive two pole switch/relay to completely isolate the battery bank, which should lead directly to two separate copper busbars, one each for the positive and negative. The correct way to connect the all negatives together is bolt them to the negative busbar and is known as a 'star' connection.

 

[[70521]]

You might confuse your charger with two inputs like that especially since the voltage from the wind generator can be variable.

 

[rubberduck]

You might confuse your charger with two inputs like that especially since the voltage from the wind generator can be variable.

Does he have a wind generator as well ?

 

[Ghodula]

Many thanks for the replies that puts my mind at rest

The batteries have a big main isolater switch, no wind generator. Wilco on the busbar

 

[Croftie]

I may be wrong here and stand to be corrected but is there any need?
AFAIK you can have both the solar and the charger operating at once, the battery will take what it needs.
I believe that if you are disconnecting the solar as you suggest via a switch it should be between the panel and the mppt controller not after it.

 

[rogerthebodger]

I may be wrong here and stand to be corrected but is there any need?
AFAIK you can have both the solar and the charger operating at once, the battery will take what it needs.
I believe that if you are disconnecting the solar as you suggest via a switch it should be between the panel and the mppt controller not after it.

You are correct that strictly speaking a switch is not necessary if all the chargers have some intelligent controller.

I have both solar and engine driven alternator connected all the time and and have a switch on my mains charger that selects my domestic or engine start battery but it does not disconnect the solar and/or alternator.

I do have circuit breakers in my solar setup between the solar regulator and the battery so I think the best place for a change over switch is between the battery and solar regulator/charger as the OP proposed.