Author Topic: Battery going flat when riding with lights on  (Read 327 times)

Offline owain

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Battery going flat when riding with lights on
« on: 06.10. 2017 10:27 »
Righto, the battery seems to be able to power all the lights for about 5 mins before going flat. Not great for winter. I'm running a 6v battery with a 6v negative wassell regulator and I've flashed the dynamo for negative earth. The battery is also powering the sidecar lights as well. All bulbs are 6v except for the headlamp which is 12v. The A10 is a plunger from 1950, my thoughts are that a) there should be a 6v bulb fitted and/or b) the dynamo needs renovating. Any ideas or diagnostics that could help?

Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline a101960

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Re: Battery going flat when riding with lights on
« Reply #1 on: 06.10. 2017 10:51 »
Quote
All bulbs are 6v except for the headlamp which is 12v.
Err, that is not a good idea. What is your reason for doing this? Replace your headlamp bulb with a 6V and all should be well.

Online mikeb

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Re: Battery going flat when riding with lights on
« Reply #2 on: 06.10. 2017 12:01 »
the 6v bulb is an obvious step. at best a 12v bulb will be very dim on 6v
have you fully charged the battery on the bench first? if so and it goes flat in 5 mins the battery is dead.
does the ammeter show its charging? if not check the dynamo and regulator. see other threads.
if all of that then what rate of discharge does the ammeter show when lights are on? and what is the combined wattage of all the lights on the bike?
New Zealand
'61 Super Rocket  - '47 B33 -  '18 Triumph Street Triple RS

Offline owain

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Re: Battery going flat when riding with lights on
« Reply #3 on: 06.10. 2017 12:31 »
I double checked all the bulbs again and confirm that they are all 6v (my mistake with the 12v bulb). When the lights are on the ammeter does not show any charging. With just the pilot light/tail lights it's -2 Amps  and with headlamp/tail lights it's showing -8 Amps. Will check wattage of all the bulbs
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline tinu

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Re: Battery going flat when riding with lights on
« Reply #4 on: 06.10. 2017 13:44 »
Last time I had troubles with el-power, the dynamo chain was broken.
A10 Golden Flash '57
VW T3 '84 "Bulli"


Offline tommo903

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Re: Battery going flat when riding with lights on
« Reply #5 on: 06.10. 2017 15:03 »
Owain...in case you're not aware, there is a step by step dynamo test on Priory Magnetos website. If you click on 'Dynamo Services' you will notice 'Dynamo Test' near the top of the page.
I have the same problem as you and and my suspicions lie with with the dynamo, but I also need to do the test to confirm.

Steve