24v solar panel to 12v battery

System
System Posts: 2,511 admin
Hi,
I got an offerto buy this panel http://abcsolar.com/pdf/sm110.pdf which the seller says is from 1998 so probably lost 10% of its power. Do not if thats true. I got an offer on the SM-110-24 so it will output 24v. If i buy a regulator can it then charge my 12v battery?

Another question is. If the sun is perfect does it mean the panel will charge with 3.15A so if i have a 100A car battery it will take 100/3.15 = 31h ?

Donnib

Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: 24v solar panel to 12v battery

    No & No.

    If you use a 24 volt panel, it outputs 35 volts. Now maybe these panels are user configurable, and you can change the jumpers to make it a 12V panel. But if you use it as a 24V panel, to recharge a 12V battery, you are throwing away half your wattage. You would need a MPPT charge controller to down convert and preserve your watts.

    The battery - it would take 31 hours to charge it from dead, but you should never take the battery below 50%. So only 15 hours - or 3 solar days to recharge. Problem is, after 24 hours and still discharged, the sulfur deposits that build on the plate, become hardened and don't dissolve back into the acid well.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 24v solar panel to 12v battery

    The answers are: sort of. :roll:

    You can use a "24 Volt" panel to charge a 12 Volt battery, but if you use the inexpensive PWM type of controller you will miss out on a low of the panel's power. If you use the expensive MPPT type controller you will miss all that money you used to have.

    The Imp on the panel is 3.15. That means that you're not likely to see more than that for charging current. It does not mean it will take 31 hours to recharge a 100 Amp hour battery. In the first place, if you have to "put back" 100% of a battery's capacity it is totally dead and isn't going to recharge in 31 years no matter how much current/Voltage you put it it. For the most part deep cycle batteries are only meant to be discharged up to 50%. Automotive batteries much less.

    On the whole, this panel would be about the same as a "trickle charger" or "slow charger" on a 100 Amp hour battery.

    You might want to read through the battery FAQ's to get a good understanding of them:
    http://www.windsun.com/Batteries/Battery_FAQ.htm