Extending battery endurance with solar cells

[longsundayrun]

Hi again !...I'd like to extend the range of my EV / Magic Pie 3 by adding 3 solar cells to the system. I'm running 3 - 12 volt SLA s in series, 18ah ...... I have 12 volt, .1 amp solar cells...Can I parallel 1 solar cell to each battery to charge it a bit as we run ?....any opinions ?....thanks !

ps... we got 24 miles on a charge last time...

[Phil O Dendron]

Hi,

you should add a diode to each solar panel to prevent current flowing from the battery to the solar panel when the sun is not shinig enough
and the battery has a higher voltage level than the panel, otherwise it would reduce your mileage 

cheers, phil.

[longsundayrun]

Hi Phil !....thanks for the reply !...Actually, the solar cell I use puts out way over the rated  12 volts...like 14-17 if aimed at the sun correctly...the diode I've used before on my arrays....you're right about that !!...thanks !

[Cornelius]

Your panels with 0,1A output wouldn't add much though; 24 miles on 18Ah would mean 0.75 miles/Ah, so, in 1 hour, your panels in full sun would add 0.075 miles - ideally...

[Marsbar]

okay, remember SLA wastes like 40% of energy while charging to heat...

So you have 18Ah. Say 40% is wasted. You need to charge 25,2Ah.

So, let's assume you have full sun, and you have 3 panels making 36V 0.1A.

It will take you 252 hours, or 21 days to recharge them in full sun and angled directly at the sun   

(25.2Ah/0.1Ah/12hrs day)=21

ps! I used SLA before but never again. The weight is simply too high and they can only be charged approx. 250 times until they are half dead...