Aux lights draining battery

[Bobble]

Fitted some aux spotlights to the bike recently and despite being the fairly normal 55w pair, they seem a bit much for the battery.
Bike is a 2004 BMW F650GS.
The lights are bulbs with filaments, not LEDs, and although a bit heavy at 55W, I was lead to believe the 400 W (?) alternator on the BMW would cope.
Apparently not. Rode to work this morning, around 60 miles and on arrival, attempting to re-start the bike to park it a bit better, the battery just didn't have the oomph to start the bike, in fact, a couple of tries and everything went very dim.
Left it a couple of hours, went back to see have a closer look and in two hours the battery had recovered enough to start the bike as if nothing had happened.
So are the lights too much or is the battery/alternator/both of the above a bit tired?

[peterekins]

Does sound like the lights are taking too much power, battery could be bit lazy, try checking the voltage accross the battery terminals with lights off, then on. You should get about 14 volts if it drops significantly then theres the problem, may seem ok but as soon as your on the road using indicaters, brake light, it can soon drag the power out.
You could also switch all the lights off when you arrive and run the engine a few miuits just to boost the battery ready for later, not realy recomended, as you need to sort the problem but at least it won't let you down.

[Bobble]

Hmm, I guessed it might be a tired battery. It could be the original for all I know, then again, heated grips won't have helped.
That said, I've read tales of some of the American BMW GS crowd using them in winter with aux lights, heated grips, heated boots, intercom/radios, three bar electric heaters, tumble dryers, microwave....the lot, all without issue.

[mancunian]

Always check battery terminals first including earth strap

[Bobble]

Always check battery terminals first including earth strap

Ooooh, good point. They were disconnected as part of the install.

[Will]

Lots of faults on gs 650 are down to loose dirty battery terminals don't ask how i no :whistle: got to be worth checking leds do draw less current thou B)

[slimbo]

common fault as a pair of 55w lamps draw will be about 9 amps and pushing the generator output over max..with everything else switched on

try converting the lamps to led bulbs then you wont have an issue..

flea bay do a nice line in h7 led bulbs . 3watt are ok for daytime running the 7.5 watt units will give more light..depending on the reflectors and lenses...

[andymac]

Put led bulbs in

[Bobble]

Any recommedations for a particular brand? (if eBay could ever supply such a thing)
I've tried LED replacement bulbs in the past and find the physical size of the "filament" part is sometimes significantly larger.

[greybeard]

Check the output from the alternator if that's low there's the problem
At the battery engine running should show about 14 volts good luck
Make mine a guiness