# Solar Panel Battery Charge Time

Registered Users Posts: 1
Hi I'm new to solar power so I hope someone can answer this easily. If you can share the math so I can do it myself in the future I'd appreciate it!

I have deep cycle LiPo model airplane batteries I need to charge. They're typically 12V @ 1-5 amps, and have a 500 Ah capacity. My question is how long would it take to charge this battery with solar panel(s) at X watts (for X=50, 100, 200, 300, 500, 1000). Do I need to hook up to more than 1 panel and use some voltage converter to get some of these higher powers? Any recommendations on panels, converters, connection schemes, or other pieces I need would be great!

Thanks so much in advanced everyone..

• Banned Posts: 17,615 ✭✭✭
Re: Solar Panel Battery Charge Time

Welcome to the forum.

What you and we need to know here is what the battery manufacturer recommends for charge rate & Voltage. Then see if solar can be used as a source to duplicate that need. Chances are it can.

This bit I don't understand: "They're typically 12V @ 1-5 amps, and have a 500 Ah capacity." A battery is rated in Voltage & Amp hours @ rate (20 hour rate is typically used for RE). What is the 1 to 5 Amps? Discharge rate used or recommended peak charging current? It would be pretty ridiculous to try and charge a 500 Amp hour battery @ 5 Amps as it would take a very long time.

Some batteries recommend a constant current charge, others a Voltage peak & time charge, and various combinations there of. If this were a standard FLA battery in an RE application you'd want to see a peak current of 5 to 13 (or perhaps higher) percent of capacity, or 25 to 65 Amps which would require approximately 400 to 1000 Watts of panel and a good MPPT type charge controller.
• Solar Expert Posts: 3,123 ✭✭✭✭
Re: Solar Panel Battery Charge Time
This bit I don't understand: "They're typically 12V @ 1-5 amps, and have a 500 Ah capacity." A battery is rated in Voltage & Amp hours @ rate (20 hour rate is typically used for RE). What is the 1 to 5 Amps? Discharge rate used or recommended peak charging current? It would be pretty ridiculous to try and charge a 500 Amp hour battery @ 5 Amps as it would take a very long time.

Just a guess, but since we are talking about LiPO4 and model airplanes, I suspect that the batteries are 500mah not 500Ah. Unless it is a very very large model!
And a Lithium battery of that size could produce 1-5 amps for a correspondingly short period of time.
SMA SB 3000, old BP panels.
• Banned Posts: 17,615 ✭✭✭
Re: Solar Panel Battery Charge Time
inetdog wrote: »
Just a guess, but since we are talking about LiPO4 and model airplanes, I suspect that the batteries are 500mah not 500Ah. Unless it is a very very large model!
And a Lithium battery of that size could produce 1-5 amps for a correspondingly short period of time.

That would make more sense.