How many 18650 cells should I use for 12 volt power supply

Hi All,

New to the forum but been reading here.....

I have a dirt bike lighting project I'm working on.

I bought a lighting kit which includes the headlight, turn signals, and stop light, horn, but I need it all to run on battery since my bike does not have a charging system.

I was thinking on using 18650 batteries but they are 3.7 volts. So how many should I use?

3 cells will give me 11.1 volts, and 4 will get 14.8.

After a fresh charge the 4 cells will be around 16 volts and I'm not sure if that's too much.

Is 16 volts too much for an H4 halogen bulb???

I could also use a voltage regulator but don't know which one....

Any help would be appreciated.

dinky,

A vehicular "12 volt charging system" isn't really that. They all charge higher than that, 12ish 13ish to 14ish volts depending on what system and what battery. What boils the electrolyte in one battery is what another chemistry needs to charge.

If no charging system, then this is a constant loss system. I'd be wary of relying on that for offroad as you might be stuck in the dark who knows where. I've been stranded with a bike in the dark a couple of times with a blown charging system. Twice it was the regulator, once it was just the carbon brushes, one time it was an antique with weird antique problems. This isn't counting ignition system stoppages.

Curious, what model dirt bike? How is ignition handled? Magneto ignition? Nice thing about mag vs battery ignition is that it's two separate systems. A charge system failure is irrelevant to engine ignition. In a 12v battery constant loss, you'd be lucky to make it 50-80 miles depending on the bike.

Budget for the project? There's better purpose made superlightweight batteries for this but the ones I'm thinking of are very pricey at $250ish last I checked.

If it really is for off road in a bike otherwise unequipped, how about the brighter off-the-shelf LED bicycle lighting systems as they're already intended to be slapped and bolted on? You're not doing 50mph through the trackless woods at night (I hope.) That H4 is going to annihilate a battery quick without the charge system component.

Sure we need to go custom on this?

I'd might look at 12 sealed lead acid battery for your setup. They can be found in many shape and sizes.

Thanks for the reply....

I don't need the light to stay on all the time. Just when I want to get on the road to the next trail. I have a 5 watt daytime running light so battery draw will not be so bad.

I was able to keep the 35 watt headlight on for an hour last night using 10 aa panasonic rechargeable batteries, 2000mah.

And I need something small to mount at the front forks behind the number plate so it needs to be small and light.

dinky

Three.


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I'd go with 4. The extra couple voltage won't harm most systems.

Personally I'd get a Fenix BC30 Bike lamp and then just power the rest off of 2-3 18650s