Flat Battery Fault Finding

Deleted account W

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Flat Battery Fault Finding…

I’ve spent the day trying to find out why my battery keeps letting me down.

The battery failed on me on the way home from Wales last weekend.

I’ve had the battery on an Optimate all week and the display showed charged and battery condition “Good”

First thing I checked was the battery voltage under no load with the engine off – 12.35 V

That’s OK it should be between 12V and 12.5V

Next to check is that the alternator is charging the battery, I checked the voltage across the battery with the engine running and the lights and grips off – 14.10V
That’s OK it should hold a steady voltage between 13.5V and 14.2V

Next I did a basic load test. To do this I pulled the HT leads off both spark plugs. I turned the engine over and noted the voltage across the battery - It fell from 12.35V to 5.6V, it also turned over for 7 seconds before it lost the power to turn the engine over and started making the dreaded clicking noise.

That’s not good, it should only fall to 10V and defiantly not lower than 8V, it should also turn the engine over for at least 20 to 30 seconds.

So this leads me to believe my batteries shagged, or the starter is pulling too much current.

How can I tell which of the two solutions is the correct one?

I don’t want to buy a new battery and find out it’s the starter or visa versa.

I’m an electrician by trade but Moto-lectrics are a bit of a dark art as far as I’m concerned
:)
 
Got a new BM battery cheap, if you want one:D
 
Much more likely to be the battery than the starter.

The battery will also be the cheaper of the two to replace :rolleyes:

And, if it's not the battery, you will have a spare one ready for when it is :D

Beware when getting a "non standard" battery that the terminals are exactly in the same postion as the original, there is very little slack in the wiring loom :mad:

Iain
 
Kev - I'd say its deffo the battery.

If you've been riding / charging it should hold a charge full stop.

If it was the starter the battery voltage would recover.

As you know the battery will hold a 'surface ' charge - thats typical of being shagged.

if it was the starter - the battery would recover but still struggle to turn the motor over

I bought a new BMW battery and its a sealed gel battery - exactly like a hawker.

PS double check by using jump leads from the car - or take the battery out and use leads.
 
motomartin said:
Kev - I'd say its deffo the battery.
Click to expand...

I think your right, I'm going to get a new one ordered Monday, hopefully get it on the bike before the BMF next weekend.

From what I've read the Hawker AGM isn't the same as a normal gel battery (see the link in my post above).

Unless thats just Hawker advertising bullsh*t :rolleyes:
 
Kev, I got my battery from these people, fast service (phoned up & it was delivered day) and the terminals are on the battery (and it was cheaper!!!)

Westco (AGM type) @£62 from www.motorbikebatteries.co.uk

Lee
 
Grumpy Lee said:
Kev, I got my battery from these people, fast service (phoned up & it was delivered day) and the terminals are on the battery (and it was cheaper!!!)

Westco (AGM type) @£62 from www.motorbikebatteries.co.uk

Lee
Click to expand...

Got one of these from Motoworks, I'll stick it on tomorrow and hope for the best.
 

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Check that the bike is not discharging the battery too much over night - measure the current into the bike from teh battery when everything is off .. should be less than say 10 milliamps.

As for which is faulty .. unless the starter is making noises -grinding /squeelin - then it is probably the battery. And that is the cheapest and easiest to change.
 
Ah-Ha - The Famous hawker Red Tops.

I designed the portable starter cart trolleys for Mclaren - inside the little box on wheels was 3 of these - albeit larger and gruntier.

They were connected in parallel to give a massive 24V volt kick to the engines via the starter probe.
The other reason was that the hydraulic system needed to spin over at a certain speed to activate lots of little sensors and things - 12 V wasn't up to it, but 24V through the poor little 12V Mitsubishi starter motor certainly woke it up.
 
motomartin said:

I designed the portable starter cart trolleys for Mclaren - inside the little box on wheels was 3 of these - albeit larger and gruntier.

They were connected in parallel to give a massive 24V volt
Click to expand...

Paralell connection = same voltage.

Series connection = addition of all votages
There fore 12+12 +12 (three of them) = 36 volts

Something wrong with yer memory. Suggest attendance at the Alzhiemers Rally SA. [Sedan] 3rd weekend in August. Last time I was there I got the award for the longest memory.
 
Ah-Ha - The Famous hawker Red Tops.

I designed the portable starter cart trolleys for Mclaren - inside the little box on wheels was 3 of these - albeit larger and gruntier.

They were connected in parallel to give a massive 24V volt kick to the engines via the starter probe.
The other reason was that the hydraulic system needed to spin over at a certain speed to activate lots of little sensors and things - 12 V wasn't up to it, but 24V through the poor little 12V Mitsubishi starter motor certainly woke it up.


We used to replace the all the batteries AND starter motors twice a year.
5 carts and probes.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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