Adding more panels to a solar system ?

[Ezookiel]

I have an "Eva Kool" 100w folding panel that feeds my Optima Yellow Top (55a/h) in my Ark Powerpack.
I am going to wire an Anderson plug running directly inside the Powerpack to the battery, and feed the solar panel into that.
However, it now appears that I may be buying a much bigger fridge than originally intended - namely an 80L side-by-side Fridge and Freezer in one unit. That is going to chew far more juice than I had originally accounted for when planning on buying the Bushman Fridge which is about 40-50Litre.
So now the 100w may not be sufficient (I don't have the specs on powerdraw on the 80L Engel side-by-side so can't check this)

I was wondering if I can just buy, say an 80w, and just hook it into the battery along side of the existing 100w as well.
Or should I find some way to rewire the panels so that the new panel and the old panel feed together into the one - probably new uprated - charge controller, and then feed THAT all into the box.
I realise this is probably better, but I don't have the technical knowhow to do it, and it is a hell of a lot to carry around.

Doing it that way seems so messy, and even if I can run them seperately, it's a lot to carry around, so I am wondering if I shouldn't just buy a 160w - 200w panel instead and use THAT on its own, and then put the 100w somewhere else. I'm sure I could find a use for it - maybe mounted permanently to the roof of the Patrol to keep the starter battery filled or something (not that it gets used for anything much).

Thanks in advance for any help you can supply.

[PJ.zook]

Really the only thing stopping you is the controller. If it can control 180W of power, then theres no problems hooking both panels together into the controller. Its the same as using one bigger one with same output as both smaller panels combined.

[Ezookiel]

But can I put two sets of panels, with their own individual controllers, onto the same battery ?
Basically like asking if I can hook two battery chargers up to the same battery I guess.

[suggy126]

No you can't, cause which ever one is charging better (most likely the bigger one) will over ride the other and shut it down so you end up with only one panel anyway. You have to use a single controller to controll all the panels together or it won't work properly.

[PJ.zook]

suggy I thought all the controllers job is, is to limit the voltage output of the solar panel so it doesnt overcharge your battery, so on a bright sunny day youre panel doesnt try and shove 18volt or something into the battery.

[tektrek]

But can I put two sets of panels, with their own individual controllers, onto the same battery ?
Basically like asking if I can hook two battery chargers up to the same battery I guess.

You sure can!!

One controller (or battery charger) will switch to float before the other near the end of charge.

I often hook up a 60A charger and a 25A charger to a 100Ah deep cycle battery concurrently for a faster charge. I also mix & match other chargers to obtain odd charge rates like 14A + 8A = 22A charge.
Easily done being a wholesaler of switchmode chargers!

No harm done.

PM me if you have any questions.

[tektrek]

No you can't, cause which ever one is charging better (most likely the bigger one) will over ride the other and shut it down so you end up with only one panel anyway. You have to use a single controller to controll all the panels together or it won't work properly.

I'm afraid you are wrong on this.

I've been designing to order discrete portable solar systems since the mid 1980s. Shutdown does not occur unless the controller is designed to do so (pretty rare these days). The smaller controller will simply switch to float mode.

Separate controllers, i.e. one per module, are acceptable. You could have say 3 PV modules each with its own controller with all 3 PV modules charging the one battery or 2 PV modules to a battery and another PV module & controller to a second battery.

tektrek (Innovative Solutions since 1986) www.tektrek.com.au

[tektrek]

suggy I thought all the controllers job is, is to limit the voltage output of the solar panel so it doesnt overcharge your battery, so on a bright sunny day youre panel doesnt try and shove 18volt or something into the battery.

You are quite correct P.J.

Most nominal 12V solar panels (a.k.a. PV modules) have an output of 18-26VDC which if directly connected to a 12V battery would make it boil and if not corrected, disintegrate.

The maximum voltage before gassing of a lead acid battery (sealed or unsealed including calcium, lead calcium, silicon lead) is 14.7VDC @ 20degC. At 14.75VDC gassing occurs along with loss of electrolyte and possible sulphation may occur as a result of this loss.

Immobilised GEL electrolyte batteries should not be charged at anything higher than 14.4VDC @ 20degC. Anything above 14.4VDC will damage the cells beyond repair/recovery.

Most batteries fail because people take the cheap way out by buying what we in the industry call "supermarket" chargers like the cheapy 4A (unregulated) chargers at auto shops.

Remember it's over voltage that kills a battery, not current (i.e. Amps).