Another Battery Thread

NorcoT · Nov 13, 2012

Hey all, i have done a number of searches on old posts but havent found a straight answer.

My bike failed to start this week, on trying the starter motor slowly wound to a halt hence the battery obviously was flat. So I ran a volt meter across the terminals and it read about 10.8v.

Bought a new battery, installed it and checked the voltage with the engine OFF, reads 11.9v. Started up beautifully

So I once again checked the voltage across the terminals this time with the engine ON. At idle the voltage is around 13v. I rev the engine to 5000-6000rpm and it reads 13.9v.

Now the threads I have read say that 14v or above is normal charging voltage for around 5000rpm.

My question is, does what I have described above sound normal? 13.9v charging voltage across the battery at 5000rpm / 13v when idle / 11.9v with the engine off?

Thanks

FinalImpact · Nov 13, 2012

NorcoT said:
Hey all, i have done a number of searches on old posts but havent found a straight answer.

My bike failed to start this week, on trying the starter motor slowly wound to a halt hence the battery obviously was flat. So I ran a volt meter across the terminals and it read about 10.8v.

Bought a new battery, installed it and checked the voltage with the engine OFF, reads 11.9v. Started up beautifully So I once again checked the voltage across the terminals this time with the engine ON. At idle the voltage is around 13v. I rev the engine to 5000-6000rpm and it reads 13.9v.

Now the threads I have read say that 14v or above is normal charging voltage for around 5000rpm.

My question is, does what I have described above sound normal? 13.9v charging voltage across the battery at 5000rpm / 13v when idle / 11.9v with the engine off?

Thanks

Yes I would say so for the exception of the OFF value.
A 12V lead acid battery has 6 cells. Each when fully charged outputs about 2.12 to 2.16 volts per cell.
I would expect to see about 12.8+ from a good battery fully charged and with core temperature of 70F. I suggest you disconnect the battery after its fully charged and measure its voltage several times. It should stay up.

Does your bike have an alarm or some add on device that MAY be pulling current and draining the battery? It sounds probable and it needs to be isolated and fixed so you can leave you bike and not have to worry about the battery going dead.

texcollect · Nov 13, 2012

Don't mean to hijack the thread, but I to have a battery problem. I left the ignition on the other day when my bike was stopped for about 30 mins and came back to a flat battery. Bump started it and drove for 60 miles, but there still wasn't enough juice to start it. Stuck it on the tender overnight and the next day checked it out.

Resting Voltage 12.2
Running Voltage @ idle 12.8
Running Voltage @ 4k 13.6
Voltage when starting 8.0 !!

So I have a bad battery or a bad charging system. From starting voltage I'd say battery !!

NorcoT · Nov 13, 2012

FinalImpact said:
Yes I would say so for the exception of the OFF value.
A 12V lead acid battery has 6 cells. Each when fully charged outputs about 2.12 to 2.16 volts per cell.
I would expect to see about 12.8+ from a good battery fully charged and with core temperature of 70F. I suggest you disconnect the battery after its fully charged and measure its voltage several times. It should stay up.

Does your bike have an alarm or some add on device that MAY be pulling current and draining the battery? It sounds probable and it needs to be isolated and fixed so you can leave you bike and not have to worry about the battery going dead.

Its a new AGM battery which I put the acid into myself, I left it to rest 20 mins after filling, the resting voltage measured immediately after was 11.9v, so I guess maybe after the battery settling more / being run with the bike it may read higher?

The bike started perfectly anyway, much healthier sounding starter motor than before, a lot faster.

I have just measured the old battery and it now reads 11.6v..

If the charging voltages sound fine to everyone I guess I dont have to worry that it is the charging circuit on the bike?

I do have an alarm fitted, I've had the bike for 9 months now and never had an issue though so I wouldnt suspect that it is leaking voltage anywhere.

Motogiro · Nov 13, 2012

New AGM battery should have a resting voltage of about 2.23 VDC per cell so your static battery voltage should be over 13.0 VDC

When you have a bad battery it should be load tested to determine if the depth of charge is within specifications. I recently learned there are many places out there that are using electronic type load testers. They determine depth of charge with out an actual load and so can be pretty inaccurate. I'm going to buy or make my own load tester.

You can use voltage to give you a logical picture for predetermining battery conditions but you really should have a load test done to tell for sure.

FinalImpact · Nov 13, 2012

NorcoT said:
Its a new AGM battery which I put the acid into myself, I left it to rest 20 mins after filling, the resting voltage measured immediately after was 11.9v, so I guess maybe after the battery settling more / being run with the bike it may read higher?

The bike started perfectly anyway, much healthier sounding starter motor than before, a lot faster.

I have just measured the old battery and it now reads 11.6v..

If the charging voltages sound fine to everyone I guess I dont have to worry that it is the charging circuit on the bike?

I do have an alarm fitted, I've had the bike for 9 months now and never had an issue though so I wouldnt suspect that it is leaking voltage anywhere.

To my knowledge an empty cell is not going to reach full potential from filling alone and/or time. It needed to be charged to sustain a float voltage. Applying a load to a recently filled but NOT charged battery can damage the plates. IMO i would charge it completely before doing anything else.

NorcoT · Nov 13, 2012

FinalImpact said:
To my knowledge an empty cell is not going to reach full potential from filling alone and/or time. It needed to be charged to sustain a float voltage. Applying a load to a recently filled but NOT charged battery can damage the plates. IMO i would charge it completely before doing anything else.

Thanks, I read the manual that came with the Varta Battery more closely and it says "The battery comes dry charged... After filling leave for 30mins and check the voltage across the terminals, if it reads 12.7v or greater it is ready for immediate use, if lower then charge is required..."

Iv already but it in the bike, will take my volt meter to it again and see what it reads.

Thank you all for your input, i wanted to address my concerns that the battery dying could have been a charging problem but it seems 13.9v reading across the terminals is sensible when at 5000rpm.

Another Battery Thread

NorcoT

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FinalImpact

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texcollect

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NorcoT

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Motogiro

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FinalImpact

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