Small backup/semi off grid office setup

[Terence1983]

AFAIK, it's a combination of both. You need the voltage higher than the battery, but it's the amps that provide the oomph. So 12V needs a panel higher than 12V, and then you can parallel them to get the amps up

For instance an 80w panel which was 18v and 4.44amps, if you connect 2 in parallel you would then double it eg 18v with 8.88amps and 160w so the battery would recharge faster. The charge controller would obviously then control the voltage as the battery is only 12v correct?

 

[wingnut771]

For instance an 80w panel which was 18v and 4.44amps, if you connect 2 in parallel you would then double it eg 18v with 8.88amps and 160w so the battery would recharge faster. The charge controller would obviously then control the voltage as the battery is only 12v correct?

Correct but I think it controls the amps and not the voltage so just make sure to keep voltage of the panels below the max of the charger, but you want your solar to equal more than your load or else you'll be in the dark. Make sure you get MPPT and not PWM. MPPT is much more efficient.

 

[TheChamp]

Surely that is dictated by your correctly sized MPPT charger and panel makeup? So, still pretty easy to get 25A?

Yes true, but if you are on a limited budget it makes a difference on what you can get away with, I guess that's what I am trying to say.

As an example my mppt has a range of 26V to 72 V, at 24V I can get away with one 400W panel because it will give me enough voltage to fall within the mppt range and also enough current to power my 8A load directly from the panel, maybe with a few amps lower.

Same scenario at 12V, my panel will be good for voltage but will fall short on current as I would be needing much more than what the panel can produce. Both systems won't be performing optimally but I would take the 24V system over the 12V.

Plus the limits imposed by most mppt controllers at 12V, most cannot go beyond 500W. I do guess there are other ways around it.

 

[wingnut771]

For instance an 80w panel which was 18v and 4.44amps, if you connect 2 in parallel you would then double it eg 18v with 8.88amps and 160w so the battery would recharge faster. The charge controller would obviously then control the voltage as the battery is only 12v correct?

EDIT: but I see what people are saying, it's hard to get a controller that does more than 15A @ 12V. Looking at the smartsolar victron, it's rated 220W @ 12V but 440W @ 24V.

 

[wingnut771]

Yes true, but if you are on a limited budget it makes a difference on what you can get away with, I guess that's what I am trying to say.

As an example my mppt has a range of 26V to 72 V, at 24V I can get away with one 400W panel because it will give me enough voltage to fall within the mppt range and also enough current to power my 8A load directly from the panel, maybe with a few amps lower.

Same scenario at 12V, my panel will be good for voltage but will fall short on current as I would be needing much more than what the panel can produce. Both systems won't be performing optimally but I would take the 24V system over the 12V.

Plus the limits imposed by most mppt controllers at 12V, most cannot go beyond 500W. I do guess there are other ways around it.

Thanks, yes I agree, see my edit.

 

[Lupus]

Parallel don't you mean if he wanted to extend his 12V capacity?

Yup sorry

 

[clickingbuttons]

Increase your budget or buy a generator.

 

[Terence1983]

Increase your budget or buy a generator.

That's the plan, I may buy a small generator in the interim to cover me in the invent of being without power for a day and save for proper solar.