BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: Phil C on 29 November, 2021, 10:00:59

Title: Battery flat
Post by: Phil C on 29 November, 2021, 10:00:59
Not specific to BSA - hope you don't mind.
My 2011 Bonneville's battery was flat as a pancake this morning. Last used the bike on 1 Nov, so about four weeks ago. Cursing myself for not using my Optimate. Would a good battery be flat after four weeks?  Phil
Title: Re: Battery flat
Post by: Pete Gill on 29 November, 2021, 10:25:17
Hi Phil
I suspect you’ll need a new one. If its the original one from 2011 its done well!
I use the gel mat batteries now such as Motobatt. Ive found they hold their charge in winter much better than the traditional ones.
I expect you’ll be able to charge it and it will work for a while, but if its already 10 years old I cant see it will have much life left now.

Pete
Title: Re: Battery flat
Post by: Phil C on 29 November, 2021, 10:34:27
I bought the battery three years ago. Would you expect it to be okay after the bike hadn't been used for four weeks?
Phil

PS Was going to go out on it to buy some bread. My daughter has borrowed my car. But the old B40 started first kick. Had to smile. One up to the old girl.🙂
Title: Re: Battery flat
Post by: AdrianS on 29 November, 2021, 10:51:31
Batteries can last for 10 years or a year. Batteries that are used last better than those rarely used.
Take your battery off and connect it to your optimate or whatever you trickle charger unit you have.
May desulphate and come back to life but may end up weak.
Cold weather normally sorts batteries out and many will fail when the temperature drops.
If you are not using a bike for a long time especially over winter, remove the battery from the bike, charge it up and store it inside and top up charge every 4-6 weeks. Otherwise use a battery tender on the bike.
For what they cost and for the inconvenience of a knackered battery, if in doubt get a new one!
Title: Re: Battery flat
Post by: Mike40M on 29 November, 2021, 11:06:04
It might be that modern vehicles constantly draws current. Though some modern motorcycles can have a winter sleep and start in spring, other not.
Worst I have is a 2018 Citroen van that has to be run at least once a month to maintain battery charge. Even worse. some modern cars with flat or removed battery must be reprogrammed when fitting a charged battery. Also experienced that some of the modern electronic regulators we fit to our old bikes draw current. I now have the habit to take out the fuse on bikes not frequently used.
As Pete says, your Bonnie battery might need replacement. Or simply sell the bike and rely on the B40.

Edit: Batteries are best stored fully charged and cold. All chemical processes goes slower at low temperatures. A charged battery will not freeze. A poorly charged battery can crack at -30C. Happened to me.
Title: Re: Battery flat
Post by: Derek996 on 29 November, 2021, 14:08:19
Not specific to BSA - hope you don't mind.
My 2011 Bonneville's battery was flat as a pancake this morning. Last used the bike on 1 Nov, so about four weeks ago. Cursing myself for not using my Optimate. Would a good battery be flat after four weeks?  Phil
I wouldn't expect the battery to be flat after 4 weeks unless, it is faulty, the lights have been left on, or there is a parasitic drain. I charge the batteries on my bikes about every 4 or 5 weeks during the winter lay off but they seldom need more than a little topping up. Try charging the battery and see how it holds up but if it has been deeply discharged, down to less than 9.5 volts or so it will never be the same again. I never rely on an Optimate to keep a battery charged.
Title: Re: Battery flat
Post by: Editor on 29 November, 2021, 15:27:52
I had to replace the battery on my Hinckley Bonnie after last winter's lay up, mind you it was about eight years old. I found it would hold the charge for about 3 weeks then lost its cranking amperage.
As I now have about 4 batteries on the bikes to maintain, I tend to charge them in turn during the winter seeing how long it takes to become fully charged. If it takes less than a day or two, I know it's still in good condition.
FWTW I use the Motobatt AGM ones on the BSA's and I got a Halfords AGM one for the Bonnie.
Chris