Solar Panel for Lithium Batteries

[E-bike]

Hi, I am looking to charge 52V / 20-Amps lithium batteries with solar panels. How many solar panels will I need?

[Sunking]

Hi, I am looking to charge 52V / 20-Amps lithium batteries with solar panels. How many solar panels will I need?

As many as it takes to give you 20 amps x 52 volts = 1040 watts. Panel voltage will need to be at least 64 volts.

[Mike90250]

How fast do you want to recharge them ? More panels = faster charging

[E-bike]

Thanks Sunking. Mike90250 we'd like to charge them in 4 hours.

[jflorey2]

Hi, I am looking to charge 52V / 20-Amps lithium batteries with solar panels. How many solar panels will I need?

You have 1040 watt hour batteries. To charge them in 4 hours you will need ~260 watts. That's about 400-500 watts of panels after losses and realistic operating conditions. You will likely end up with two 72-cell panels, each about 250 watts. That will give you about 70 volts, which is what you'll need to run an MPPT charge controller.

[Sunking]

Thanks Sunking. Mike90250 we'd like to charge them in 4 hours.

Does not work that way with solar. You want a 4 hours charge rate. To do that you have to know the battery AH capacity. Example if it is 20 AH you need to charger that can supply 5 amps. Problem is even if that is a commercial AC charger takes 6 to 7 hours. There are not that many Sun Hours in a Day to do with solar.

I assume you have an E-Bike Right? I also assume you are using either LFP or LiPo battery. If that is correct you want to charge at C/1 or C/2 with solar and in practice will take 2 to 4 hours to charge. So if you have a 20 AH battery will take 20 or 10 amps respectively.

To do that on say a 52 volt battery the panel wattage required is easy to figure out. Charge Amps x Battery Voltage x 1.2 = watts using a MPPT Charger. So lets say 20 amps x 52 volts x 1.2 = 1248 watts with a 20 amp MPPT Controller. You are looking at a $2000 to $2500 battery charger. That wil getter done in 2 hours.

Or you can do 4 hours for 650 watts of panels and a 10 amp MPPT charger will cost about half that and do the job in 4 hours.

Hope you got lots of cash to go green. If it were me I would just buy a commercial charger for $50 and pay that mean ole POCO 1 cent to charge up in 2 hours.