Your Questions About Solar How To Regulate To 12v

Lisa asks…

Solar Panel wattage for my Electric Bike?
I am looking to purchase an Electric Bike for transport to work. I work on an Organic farm and need to save some energy up those hills.

I need help figuring out what size solar panels would be needed to charge the battery, and whether its plausible.

I’m looking at Ebay in Australia as I am immigrating down there. I prefer to afford the foldable/portable solar panel system: 80 watt, 120 watt, 160 watt, but IF necessary a bit more.

300w 3 PHASE 36v ELECTRIC REAR WHEEL
THREE 12v 17ah SLA BATTERIES (Total 36v)

or

Motor: 250 Watt brush-less DC hub
Batteries: 24V/10Ah pack, valve regulated

can anyone out there help explain to me how to figure this out?

thanks

Lizzie asks…

I have a 4w solar panel that’s rated at 250ma short-circut and 230ma operating current. And I have a 12v charge controller. What I was thinking of doing is using the panel to trickle charge my Hyundai Sonata’s battery through the cigarette lighter. I already have a male cigarette lighter plug and know which wire is the positive and which is the negative. But I have 3 questions for you:

(a) Looking at the owner’s manual, it says that the cigarette lighter outlet isn’t active (on) unless the engine is on. So I’m thinking that charging won’t happen when the engine isn’t running. Am I correct here?

(b) Assuming I am correct in (a) and the engine must be running for the cigarette lighter to be working, will the panel when plugged into the lighter help the alternator charge the battery? I’m thinking that the panel would help the alternator out so it doesn’t have to work as hard. But maybe I’m wrong on this so that’s why I thought I would ask.

(c) Is the charge controller even needed with my panel being relatively small? No biggie hooking up the regulator, but I was just thinking I could cut down how much I need to have in the car. So this one is more curiousity than anything.

I also have a side question that you may be able to answer too. Normally, I use NIMH batteries because most of the stuff I do requires relatively low current and voltage. So I use LM317T current regulators to keep the current within my needed range. I was thinking of getting a small SLA battery (either a 6v, 1.2mah or 12v, 1.2mah) to extend the duration of the devices I power with the NIMH and have 3 questions:

(a) Will my 12v charge controller work with a 6v SLA battery? It’s about a $8-10 difference in price so I was wondering if I can save some money. FYI, for my purposes the 6v would be enough.

(b) With SLA batteries, it is more important to regulate the voltage or the current? I’ve heard that it’s the voltage that needs to be monitored. I ask this because I was wondering if I can avoid the charge controller and simply use a LM317T current regulator set low enough for trickle charging. If not, then it’s no biggie using the charge controller. Just thought I could compact things more with the LM317T.

(c) I keep the solar panel leaving up against a window in my house that gets a lot of sun throughout the day. And keep the NIMH batteries on the floor with a wire running up to the window. The room is well ventilated and doesn’t get too hot. Temps can range anywhere from about 60 to 85 degrees F. My question here is this. I know that SLA batteries vent hydrogen gas. Will the sunlight in the room and room temp possibly lead to an explosion? FYI, little light hits the floor area when I keep the batteries. But I don’t know what the tolerance level of the batteries would be. So I thought I would ask you experts out there if I’d be ok. My guess is yes, but I want to make sure.

Thanks in advance for all your help!!
Thanks Lee for your help. I want to avoid having to open the hood at differing times to do the charging. So I was trying to make it easier by doing it through the cigarette lighter.

And fyi, you can configure the LM317T to regulate either voltage or current. I do it all the time to make sure my various size NIMH batteries and devices don’t get too much current. So depending upon your configuration and resistor values, you can regulate the voltage or current. And I understood that trickle charging a SLA battery is supposed to be C/100.

My problem was I wasn’t sure if the engine needing to be running would basically cancel out the positive effect of the solar panel charging the battery. At max, I get 305ma. But generally, it ranges from about 180-270ma.