Battery sizing for electric bicycles

[SunEagle]

Thanks. I saw a blog post https://www.altestore.com/blog/2016/...w-solar-panel/ that mentioned using a 89AH battery- sounds like that wouldn't work terribly well. So it sounds like the ideal target would be 50ah for my panel. I can get these 2 batteries at a pretty good sale price this weekend ($50 each for agm's)- do you think I should hold off and look for a single 50 instead?

Actually Amy from Altestore is a member of this forum and I value her input. Maybe 100 watts will be ok for an 89Ah battery but IMO that battery will not last that long,

Also you have 4 cheap HF panels that suppose to equal 100 watts but that may be only under Lab conditions. So you should expect less output then they post which may or may not get up to 5.5 amps.

I also say that your first battery bank is a learning one. So if you can get them cheap or free the go for it. But don't expect them to last their posted life since we all "learn" how to keep our first bank happy.

[wunder]

Thanks. I saw a blog post https://www.altestore.com/blog/2016/...w-solar-panel/ that mentioned using a 89AH battery- sounds like that wouldn't work terribly well. So it sounds like the ideal target would be 50ah for my panel. I can get these 2 batteries at a pretty good sale price this weekend ($50 each for agm's)- do you think I should hold off and look for a single 50 instead?

[SunEagle]

Hello wunder and welcome Solar Panel Talk

A real easy way to size the panel wattage and battery system is to have a charging system rated between C/8 and C/12 where C = the Ah rating of the battery. The middle ground would be C/10 or 1/10th the Ah rating of the battery as charging amps.

So a 70Ah battery system would require around 7 amps of charging. IMO most 100 watt panels probably have an Imp = 5.5 amps which would be in the C/12 area or just about the minimum amount of charging amps needed to keep it happy.

[wunder]

Hi everyone, I'm just getting my feet wet with solar power. I've got a 100w panel from Harbor Freight and I've been charging a 17ah 12v battery, but I need more capacity for what I'm trying to do. My wife and I have electric bicycles that I would like to charge exclusively with solar power. I've done some reading and searching and I think I have a solution, but I'd like to run it past more experience folks to see if I'm on the right track. We would like to ride several times a week, but we don't typically use more than about 1/2 the battery power at a time.

The bikes each have 11.6 ah @ 36 volts = 417 watt hours
My 100w solar panels apparently will generate about 400 watt hours per day from what I've read about solar hours and effective power generation.

So far so good- I think solar should be able to handle my needs.

I'm planning on buying 2 35ah batteries and hooking them up in parallel for 70ah total (840 watt hours)

The battery chargers for the bikes are 2 amps @ 42v = 84 watts

My questions: will 100w panel be able to keep 70ah worth of batteries charged? I have a 300w inverter which is working ok, but I'm also thinking it would be nice to be able to power my sump pump in the event of power outages as an emergency back up so I'm thinking about getting a 750w inverter for this purpose. Are there any downsides to a larger inverter?

Thanks in advance from this solar noob.