Powering market lights from battery

[JamesW]

Supposing I wanted to power my existing front lights from the battery of the bike but have the ability to take them off this and put them on another bike - so not a permanent fixture...

The battery pack for these says that they are 7.4V (Moon XP 1500)

could I use this to step down my 36V battery voltage:
http://www.banggood.com/DC-3V-40V-To-DC-1_5V-35V-Adjustable-Step-Down-Power-Supply-Module-p-91815.html
If the answer is yes, Could I reallistically add another 2/3 in parallel to give me 12V, 5V and 3V supplies on the bike
for running other things like EL wire, other lights / USB powered devices

 

[Geebee]

These regulators work really well BUT a fully charged battery is going to be ~42v which is above spec. so potential for failure.

 

[JamesW]

Anything more suitable?

 

[patpatbut]

This

http://em3ev.com/store/index.php?route=product/product&path=41&product_id=90

Working flawlessly on mine

Pat

 

[Geebee]

Probably cheaper to buy one of the lights from banggood and just leave it on the bike.

 

[mfj197]

Here you go JamesW - Hobbyking 20A SBEC. I was recommended this over on the mtbr Lights - DIY forum for exactly the same purpose. It has selectable output voltage of 5V/5.5V/6V/7V/9V and will output up to 20A current. Input voltage from 2 to 12s Li-Ion batteries. I had to order it from Hobbyking's US warehouse but I now see it's in stock in their UK one too - link above is to UK item.

I haven't actually wired it in yet as I haven't carried out the ebike conversion but I'll certainly be wiring this in.

If your current battery pack is 7.4V then the LED controller for 3 XM-Ls is either buck (dropping voltage) or boost (raising voltage). You could therefore set the SBEC to either output 7V or 9V - wouldn't matter which.

Michael

 

[JohnCade]

Not really relevant to this but looking at the manual for my German bike the other day it states that bikes over 11 kilos must have independent lighting from a dynamo, and not internal battery powered lights. Presumably an e bike battery powered light would be okay too.

I wonder if this is just a German law or if it applies here too but is ignored?

 

[JamesW]

Is there something suitable for a 12V rear LED as well - 1 adapter for both front and rear voltages without twiddling a pot?

I Like Michaels thing from Hobby King - I have one on my desk to give me a USB level voltage, and I've ordered d8veh's initial suggestion in the Lights again thread for a front light, so I'm thinking that will go straight from the 36V, but I'd like to have a rear light too and they all seem to bee 12V, I'm not as keen on patpatpat's one as I'm not sure if the output will vary as the input drops off from the battery?

What sort of fuse rating do I want to put inline to ensure I don't blow the battery with these things (what is the calculation?)

James

P.S John - UK Law does not specify the requirement for lights to be powered from a dymano anymore, the lights must be a minimum brightness and between certain heights when mounted on the bike from recollection. I belive you will find it in the highway code!

 

[Geebee]

Just had a thought re rear red leds, buy 2 sets of these (2 LEDs per set) and wire 3 in series to allow running directly from your battery.
They need a single hole mount each so a quick bit of DIY and if they are any thing like the white ones on my car they will be bl..dy BRIGHT.
Oh and they wont draw 10w most likely less than 3w.
http://www.banggood.com/Car-10W-LED-Eagle-Eye-Light-Daytime-Running-Backup-Lamp-12V-p-956545.html
Disclaimer: I have not run these particular LED's in series but have done so with many in the past with never an issue.

 

[JamesW]

Thanks Geebee

I had been looking at something like this:http://www.banggood.com/LED-Motorcycle-Tail-Brake-Light-Indicator-Rear-Lamp-Unit-Chrome-p-85418.htmlon the basis it should bolt straight onto my rear rack with minimal DIY, the problem is that they are 12V and the battery is 36V which is which I thought I needed to step down.

I wouldn't need to step down the other 12V LEDs if I wire them in series then?

 

[Geebee]

If you wire 3 in series it should then run on 36v ok.
If I had any spares I would give it a test run, but mine are bolted to the car.

As stated above I have not done it with these particular leds but have never had an issue doing it with many others, the only reason for the disclaimer is that if they are running a buck converter I do not know what they will do in series and I can not find any info about it.

 

[JohnCade]

Is there something suitable for a 12V rear LED as well - 1 adapter for both front and rear voltages without twiddling a pot?

I Like Michaels thing from Hobby King - I have one on my desk to give me a USB level voltage, and I've ordered d8veh's initial suggestion in the Lights again thread for a front light, so I'm thinking that will go straight from the 36V, but I'd like to have a rear light too and they all seem to bee 12V, I'm not as keen on patpatpat's one as I'm not sure if the output will vary as the input drops off from the battery?

What sort of fuse rating do I want to put inline to ensure I don't blow the battery with these things (what is the calculation?)

James

P.S John - UK Law does not specify the requirement for lights to be powered from a dymano anymore, the lights must be a minimum brightness and between certain heights when mounted on the bike from recollection. I belive you will find it in the highway code!

Must just be German law then. I expect the last time I looked at the Highway Code was when I sat my test fifty years ago. I think the red flag law for motors was still current.

 

[JamesW]

Ok. I'll have to revise the difference between buck and boost and then maybe I'll power up slowly from a bench top supply at work if that's what people would recommend I do? - If I go down that route.

Would adding the 4th LED in series cause a problem? - It should future proof the rear lights against a battery size increase.

 

[Geebee]

Ok. I'll have to revise the difference between buck and boost and then maybe I'll power up slowly from a bench top supply at work if that's what people would recommend I do? - If I go down that route.

Would adding the 4th LED in series cause a problem? - It should future proof the rear lights against a battery size increase.

It will make the lights run dull as they wont see enough voltage each.
The lens on them give a nice wide veiwing angle, and 1 would make most bike tail likes look anemic.