How long should a battery hold charge?

[N Dentressangle]

Had to jump start SWMBO's 2002 Hornet this morning. It's got 5k on the clock and had a new battery about 6 months ago.

The other thing it has is a Datatool alarm, the kind you can't ever entirely switch off, but probably pretty standard on bikes.

If you leave the bike for a week, the battery is too flat to start the engine, and sometimes gets like this even after a few days. She doesn't do long rides, but the commute to and from work is a 12 mile round trip.

Should the battery be discharging this quickly? It's been checked over by All About Bikes in Bristol, who fitted the battery, and who say there's nothing wrong with the alarm or the battery and that she's just not riding it enough. I'm dubious...

Any thoughts?

[black-k1]

I hate bike alarms!!!

I would expect the battery to last much longer than a week (my 10 year old battery in my Honda VTR would go about 3 months before not having enough juice to start the bike) but with an alarm - who knows?

Edited by black-k1 on Monday 23 June 10:17

[Muffles]

Reg/rec? That went on my CBR and was hard to diagnose, it was only when it got hot that it started failing. Also it didn't go completely - above 5k rpm or so it would still charge, but 5k was the 'break even' point or something.

[dern]

You need to measure the current flowing from the battery with everything switched off as you'd leave it in the garage. Then find out whether that's within the range pulled by the alarm and if it is then there's not much you can do about it I'm afraid. Alarms are cack imo. If all is within spec then get a trickle charger and plug it in everynight.

[tim2100]

Sounds like the alarm is draining the battery. Worth checking what the voltage is on the battery and find out what drain the alarm is.

Any way of disconnecting the alarm and seeing if it still drains?

My Fireblade can go 2-3 months without use with alarm etc. and turns over first time.

Is the bike kept in a garage with power? if so may be worth getting an optimate to keep the battery topped up.

[N Dentressangle]

Hmmm. Yes, I hate alarms too.

All About Bikes reckon they've checked the alarm and it's fine, but the voltage reg might be a thought. I know the previous owner had the alarm disconnected because of this problem, but just wondered what kind of experiences others had with alarms and battery drain.

Thanks all.

[dern]

N Dentressangle said:

All About Bikes reckon they've checked the alarm and it's fine, but the voltage reg might be a thought. I know the previous owner had the alarm disconnected because of this problem, but just wondered what kind of experiences others had with alarms and battery drain.

Having an alarm on my blade meant that over the winter it was touch and go whether there would be enough charge left to start the engine as it's got to run the fi fuel pump and all that jazz. I think it was at that point I started leaving it on the trickle charger every night.

[aeropilot]

I hate alarms for this reason too, and was warned off fitting one when I bought my Ducati Monster many years ago, as the batteries were too small on the Duc to maintain a decent charge if you didn't ride it regularily. Even without an alarm, the battery would be discharged enough not to be able to start it after about 3-4 weeks if it hadn't been given a decent run...

Not having power in the garage, meant that in the end I had to buy a 2nd battery, and keep one on trickle charge in the flat, knowing that a battery change would be reqd., before being able to ride it, if I had not been able to for a few weeks.

T'was a right PITA.

Have same problem now with the Harley now as well as that has a factory alarm. I did try one of those Oxford solar powered trickle chargers, but, it seems that it's ability to supply is less than the drain from the alarm, so again, if you leave it for more than about 3 weeks the battery hasn't enough capacity to turn over 1600cc of v-twin.
So, back to the 2 battery routine again....

If you've got a power supply in the garage, then an Opitmate is the best investment you can buy for a bike(s) without a doubt, and still is even if you have to go the alternative 2nd batt route with one kept on charge in your house.

[Sossige]

aeropilot said:

If you've got a power supply in the garage, then an Opitmate is the best investment you can buy for a bike(s) without a doubt, and still is even if you have to go the alternative 2nd batt route with one kept on charge in your house.

Another vote for an Optimate or Accumate, you can't buy better. The problem with a battery is if you totally discharge it, it will never recover properly and not hold charge properly.