Help with cabin system

Old Guy

Hi everyone,

I just got a great deal on two 12V 185 amp hour Crown (CR-185) batteries.

I want to use them in my cabin. I only use the cabin once a week. Power usage will be very low, some LED lights and a water pump for shower and sink. Everything will be 12V (no inverter use).

I doubt I will ever discharge the batteries more than 40% (for the sake of calculation). The batteries will have all week to recharge. Way up on a hill and plenty of sun. 8)

Could anyone suggest a charge controller and what size panels I would need for something like this?

Thanks!

Cariboocoot

Re: Help with cabin system

Fairly simple, really.
Two 185 Amp hour 12 Volt batteries in parallel = 370 Amp hours @ 12 Volts.
Minimum charge current of 5% (and you do want charge current here; not maintenance current) = 18.5 Amps.

Now how to get it?
You could use a PWM controller and about three 130 Watt 12 Volt panels:
http://www.solar-electric.com/ss-20l.html $79
http://www.solar-electric.com/solartech-spm130p-s-n-130-watt-multicrystalline-solar-module.html $255
This would give you slightly more than the minimum (good) and max out the controller. Cost: $844
Or you could use a small MPPT controller and 200 +/- Watts of higher Voltage panels:
http://www.solar-electric.com/mosumpsochco.html $224
http://www.solar-electric.com/trina-solar-multicrystalline-240-watt-tsm-240pa05.html $228
This would limit you to only 15 Amps (a bit low but should work) and max out the controller. Cost: $452

Amazing, isn't it? You could actually use two of those MPPT 15's and two of the Trina panels and get 30 Amps charging (8%) for $904.

You have to take into account things like shipping costs (bigger panels = more money) and mounting (bigger panels = heavier and larger). But there are certainly some options.

Old Guy

Re: Help with cabin system

THANK YOU!

One more question please.....
A neighbor upgraded his controller to a MPPT and offered to give me his Xantrex C60. This is a 60 amp model. Will this work with the three panels you suggested?
I am assuming it wouldnt hurt to have the controller rated for more than the panel output and I could add more later if needed. Is this correct?

Cariboocoot

Re: Help with cabin system

The C60 is a PWM type controller. It will work with the "12 Volt" Solartech panels on your system. It does not matter that it is capable of handling 60 Amps.

It would work with the other panels too, only much of their power would be lost due to the Voltage difference. In essence you'd only get Imp as current max regardless of the panel Watts.

Old Guy

Re: Help with cabin system

Thank you again Cariboocoot.

I think I get it now.

niel

Re: Help with cabin system

be sure it has the bts (battery temperature sensor) sometimes also referred to as an rts or remote temp sensor. if he does not have one then buy one.