Advice needed for motorbike electrics

[cyclistbruce]

Hi,

I'm after some advice on motorbike electrics and Li-Ion batteries. I need to fit a 1.9a LED beacon to the rear of my motorbike so that it can be used for marshalling. I want it to be able to run off a seperate supply as you can't turn off the headlights and main battery drains quickly.

My idea was to get a 12v Li-ion battery and wire this to the LED light, with a seperate feed in from the alternator. So that (in theory) the alternator will run the Light and charge the battery, which can then power the light when the engines not running.

Would there be any issues with this, particuarly with the charging of the battery, am I likely to knacker it as theres no cut off?

Cheers in advance.

 

[ajelec10]

When battery's are connected in parallel, they discharge each other, that's why if you install a second battery in a vehicle you need to install a split charging system this is just a relay the connects the secondary battery in parallel to the main battery when the ignition is on. You may have a problem using a lithium battery as these require special charging devices that monitor the state of the battery. The alternator could blow the lithium battery pack up? If your only running one led light you could get a Makita drill battery rig up a stand alone system running the led and just change battery when flat and recharge in normal charger? Hope this helps.

 

[stuartcourt]

When battery's are connected in parallel, they discharge each other, that's why if you install a second battery in a vehicle you need to install a split charging system this is just a relay the connects the secondary battery in parallel to the main battery when the ignition is on. You may have a problem using a lithium battery as these require special charging devices that monitor the state of the battery. The alternator could blow the lithium battery pack up? If your only running one led light you could get a Makita drill battery rig up a stand alone system running the led and just change battery when flat and recharge in normal charger? Hope this helps.

know who I am coming to for my van electrics (do my head in)

 

[cyclistbruce]

Thanks for the reply, I somehow thought it wasn't going to be that easy! I did think about the drill battery idea, but I didn't think it would last long enough. The rear beacon is 1.9A a and I may possibly need 2x 1A front led strobes. So that's about 4A, I think the Makita battery's are about 3Ah?

 

[Marvo]

I'd agree with Ajelec10, charging a Li-Ion battery using a vehicle alternator is definitely a no-no. A 4 Amp load at 12 volts is pretty low and your existing motorcycle battery should handle it for an hour or more and still be able to start the bike. Maybe just carry an extra fully charged bike battery to run the LED's.

 

[cyclistbruce]

Thanks for that, the only problem I had with the bike is you have to have all the electrics on, so it's the headlight and fan that drain the battery. I might just wire directly to battery, so I can still use them when the engines not running. And hope I don't forget and leave them on over night!

 

[telectrix]

if you're wiring to the battery, make sure to fit in-line fuse/s.

 

[D Skelton]

Wire the lights from the switch feed at the fusebox. That way they will be seperate from the other electrics but will not be able to be witched on when the key is removed