Solar charging two batteries

[Lee]

Hi guys

Occasionally I am forced to use my observatory Windows PC when not observing. This involves reeling out a 240V lead to the obs. I have thought of having a 12V batt and inverter in the obs to run the PC for brief periods occasionally.
I already have a solar panel keeping a small 12V SLA battery charged for the alarm - Can I charge two different sized batteries at once - I expect I should just wire another charge controller/battery in parallel with what is there? Is this right??

TIA

[Starkler]

If they are both 12V and wired in parallel permanently theres no issue.

If the two batteries hold different levels of charge voltage when connected it will cause a current flow from one battery to the other which could be problematic.

[Lee]

If I had a separate charge controller (like this one) (http://www.jaycar.com.au/productView.asp?ID=AA0258) on the second battery (there is already one on the first) - this would stop any flow between the batteries shouldn't it??

[rally]

Lee,

Depending on the panels capacity and its charging voltage and mechanism, you may be able to put a diode in series with each charging feed.
That way the batteries are isolated form one another, but can be charged.

The diode will have a 0.7v drop so this may cause problems, in any event if the charging circuitry requires voltage sensing of the battery then this may be a problem.
At least make sure the batteries of the same type of battery - say SLA.

If it were me - I would buy a second charger or make a dedicated circuit to handle the charging depending on what is in the system you have.


Cheers
Rally

PS forgot it was solar !

[Lee]

I'll give it a crack with a second battery/controller together in parallel, and see how it goes.... what could go wrong! :D

[asterisk]

With the second regulator, hopefully nothing. As long as the panel is providing sufficient amperage to charge both batteries, then there should not be a problem. The solid state regulators are a much better unit than the older mechanical / solenoid units.

Avoid trying to charge two different amperage batteries from the one regulator - the regulator will turn off when the smallest battery is charged.

[Lee]

Thanks for the replies guys - I'll post an update when I get it going.... :)