Help needed on Ammo can solar project

Backwoods boy

Backwoods boy

CORNBREAD KILLER
Joined
Jan 25, 2010
Location
NWNC
I'm going to start a project using a .50 ammo can, 2 12v 10ah batteries in parallel (because they fit nice in the can) and solar charge controller (specs below in pic) to charge 12v items in case of the zombie apocalypse, really just something to put back or in the car. My question is, with the specs of the charge controller, how many watt solar panel should I use with the above setup to quickly/efficiently recharge the batteries? Thanks in advance.
 

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I took electricity back in high school and believe there was a formula to figure it out but its been 15 or so.years and i can't not remember.
 
Remember that class in high school with the test where the possible answers were:
A) <
B) >
C) Impossible to answer with the information given


Well in this case its C.

We know that it is capabl of outputing 10A at either 12V or 24VDC.
What we dont know is the power intake requirement to produce this output.
This should either be stated OR at a minimum a converter efficiency value provided.

Volts x Amps = Watts


So if we assume 12V * 10 A = 120 Watts.
Now assume a 25% efficiency (stab in the dark) you would need 480Watts.


*** I read the spec shet on a small busted phone screen if the input values are provided I apologize.
 
Unfortunately solor energy is just ok, if you want to "charge" your battery it will take a pretty big panel, not quite 480watts!!!! Lol. 20 watts will give you 2amps at ten volts, so a 20 watt panel will "charge" a 12v battery in about 12 hours or so , or one full day. Now if you just want to "maintain " a charged battery then a 5 watt panel would work just fine.
 
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krehel24 said:
20 watts will give you 2amps at ten volts, so a 20 watt panel will "charge" a 12v battery in about 12 hours or so , or one full day.
Click to expand...


Wouldnt that totally depend on the size of the battery, lol?

Re-read what I posted. Im assuming a 25% efficiency, some solar panels dont achieve that and some are much higher. He has a charger controller that outputs 10A, it may not have voltage compensation. It may be an all or nothing. 2A may be irrelevant if the controller requires a 10A out.
 
Ron said:
Wouldnt that totally depend on the size of the battery, lol?

Re-read what I posted. Im assuming a 25% efficiency, some solar panels dont achieve that and some are much higher. He has a charger controller that outputs 10A, it may not have voltage compensation. It may be an all or nothing. 2A may be irrelevant if the controller requires a 10A out.
Click to expand...


This is a good point, I didn't think about the controller. I was just thinking a panel alone to charge the battery, but yes if it requires 10A then pull out the wallet!!! I am still a little unclear about this project, wouldn't be easier and cheaper to just buy one of those jump boxes???


In regards to the controller spec, it is a little vague but I would think that is an output "up to 10A" this would make the whole thing make more sense
 
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Found a little info on interweb. Does this sound about right?

Multiply 20 AH x 30% which equals 6 amps
Multiply 14.4v x 6 amps equals 86.4 watts
Multiply 86.4 watts by 2 for efficiency of panel (50%) equals 172.8 watt panel.
 
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I haven't bought the controller. Its a 10a max output. Doesn't require 10a either.
 
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