DC-DC Converters for Accessories

[fusion.wind]

Hello,

i have a 36v battery and wish to run lights from it.

Simplicity, I currently have a 6v front nice and bright fella. Is it worth putting in a 36v-6v DC-DC converter, or 'upgrade' and build something with 3 x 12v LEDs in series? If the converter went in parallel with the feed to the rest of the ebike bits, how much will it affect? Should I put other protections in like current limiters or extra smoothing capacitors for if the lights were set for flash will the pulsed current affect the controller circuitry, or should it be OK. The controller is BBS01b, but I wonder if it expects smooth ripple free DC.

Is it also worth wiring in a small current shunt and meter to measure as a bonus since I have no real view at the moment what is legs and what is motor.

I've had a quick Internet search to see what is around, but would be keen to hear if anyone else has done similar. I'm aware that powering the lights will shorten the potential ride...

Cheers.

 

[Danidl]

Hello,

i have a 36v battery and wish to run lights from it.

Simplicity, I currently have a 6v front nice and bright fella. Is it worth putting in a 36v-6v DC-DC converter, or 'upgrade' and build something with 3 x 12v LEDs in series? If the converter went in parallel with the feed to the rest of the ebike bits, how much will it affect? Should I put other protections in like current limiters or extra smoothing capacitors for if the lights were set for flash will the pulsed current affect the controller circuitry, or should it be OK. The controller is BBS01b, but I wonder if it expects smooth ripple free DC.

Is it also worth wiring in a small current shunt and meter to measure as a bonus since I have no real view at the moment what is legs and what is motor.

I've had a quick Internet search to see what is around, but would be keen to hear if anyone else has done similar. I'm aware that powering the lights will shorten the potential ride...

Cheers.

My advice, for what it's worth is not to bother..
But in specific terms the lamps on ebikes and others are typically 5 watts. And at 6 v that's an 1 amp. Most white lights LEDs require about 4 v accross them for operation, so there is already a power loss at 6 v.. Were you to buy build a DC DC convertor, at 90% efficiency, then the draw from your battery would only be 0.15amp. .. and would not be noticeable in terms of power draw or range reduction. The ripple introduced would not count for a hill of beans.. so don't worry about capacitors... The output resistance of the main battery is so low that it behaves like a perfect voltage source.
If you wanted to measure battery current and battery power, you already have a ready made shunt in place... The cable drawing power from the battery pack to the motor is of a fixed resistance, so measuring the voltage drop accross it measures the current..of course you need to measure it's value to calibrate it. But it is a loss free method of measurement.
Were you to decide to string 3 12 LEDs in series , with perhaps one to the rear as red and two on the front, they would probably be consuming 0.25amp , but you would have the problem of making housings and fixing them.

 

[Deleted member 4366]

You can buy lights with wide range dc/dc converters already in them. You can find them at Banggood.com under motorcycle lights. One you have the description, you can find them on Aliexpress and Ebay too.

A wattmeter is always nice. it helps you a lot to understand how the bike works. You can get ready made ones from Ebay. They have internal shunts, but I always take the shunts out and mount them remotely at the battery so that I can mount the wattmeter on my handlebars without thick wires. If you search the forum for wattmeter threads, you can see how I did it. I've done various types. Some are more waterproof than others.