Why do my batteries show 16v?

[jimmy_the_builder]

I've got two 170ah domestic batteries which appear to have bitten the dust. These are reasonably good quality batteries so I took them home and checked the fluid levels - all ok. Then I put one of them on to charge with my optimate charger, and after not very long it showed the battery as being charged. After this it was showing 16.7v (this was last night). Now it's showing 16.1v.

I really don't know anything about batteries so forgive the dim question but why is this voltage so high?

Cheers
Jimmy

 

[DAKA]

If its not a dodgy volt meter I presume your garage is very hot at the moment coupled with a short in a cell causing heat to be generated within the battery, the heat is enhancing the voltage , I suspect it will not hold charge for long but hope I am wrong .

 

[jimmy_the_builder]

Voltmeter is good; garage is 23c. There are no hotspots on the battery. Hmm.

Cheers
Jimmy

 

[ccscott49]

Charger connected or not?
You should see where I am coming from.

 

[markleuty]

Voltmeter is good; garage is 23c. There are no hotspots on the battery. Hmm.

Cheers
Jimmy

I had exactly the same problem with my batteries yesterday. They were reading over 16V and still cool to touch.

On my voltmeter, the low battery indicator had come on, so I replaced the battery in the voltmeter and lo and behold, the batteries were measured at a much more sensible voltage.

I have no idea why a fading battery in the voltmeter would cause it to read high, but I think that is what it must have been...

Mark

 

[jimmy_the_builder]

Charger connected or not?
You should see where I am coming from.

Not connected.

Cheers
Jimmy

 

[jimmy_the_builder]

I had exactly the same problem with my batteries yesterday. They were reading over 16V and still cool to touch.

On my voltmeter, the low battery indicator had come on, so I replaced the battery in the voltmeter and lo and behold, the batteries were measured at a much more sensible voltage.

I have no idea why a fading battery in the voltmeter would cause it to read high, but I think that is what it must have been...

Mark

Aha. The BATT indicator is on on mine as well. How interesting. Ok - I'm off to get another voltmeter. Stand by!

Cheers
Jimmy

 

[jfm]

16.7 just doesn't stack up. If the battery is standing there, with no charger connected, and you haven't done open heart surgery on it and changed it to a 7 cell battery rather than 6, then anything above 14 or so defies the laws of electrochemistry. Suggests the voltmeter is faulty (or at least made in the same factory that makes Mercedes speedos...). Are you realy sure about the voltmeter?

 

[jimmy_the_builder]

Are you realy sure about the voltmeter?

Not now - I think Mark might have put his finger on it. I've just arrived on the boat where my other voltmeter is, and shortly I shall be returning home to try again. The excitement of all this is barely imagineable!

Cheers
Jimmy

 

[oGaryo]

The excitement of all this is barely imagineable!

Cheers
Jimmy

Jimmy, please hurry back, I can only hold my bated breath for a little while

 

[markleuty]

Jimmy, please hurry back, I can only hold my bated breath for a little while

+1

 

[gjgm]

Not now - I think Mark might have put his finger on it. I've just arrived on the boat where my other voltmeter is, and shortly I shall be returning home to try again. The excitement of all this is barely imagineable!

Cheers
Jimmy

I cant wait for the full voltmeter research article to appear in Motorboat and Yachting.This would have made one of the most challenging WNS if only they werent sitting in your garage, though I suppose you could have held that info back until post 395...

 

[tinkicker0]

Some smart chargers if detecting sulphated cells in a deep discharged maintenance free battery, will sent 20v through to break up the lead sulphate and ready the battery to accept a charge again.

Maybe this is it?

 

[andy59]

yep , please hurry Jimmy my tea is getting cold as i stare at the screen waiting !!!!!

 

[jimmy_the_builder]

Sorry for the delay everyone, I've had to have a cup of tea on the boat while I'm here. Mind you, I'm learning all about evc leg trim calibration at the same time, gosh.

Cheers
Jimmy

 

[DAKA]

Sorry for the delay everyone, I've had to have a cup of tea on the boat while I'm here.
Jimmy

How can you just sit there drinking tea at a time like this

 

[jimmy_the_builder]

How can you just sit there drinking tea at a time like this

I know, I know, a shocking disregard of the real priorities, sorry. You'll be pleased to know that I've finally finished my tea, and am heading back to Chez Builder right now...

Cheers
Jimmy

 

[VicS]

Some smart chargers if detecting sulphated cells in a deep discharged maintenance free battery, will sent 20v through to break up the lead sulphate and ready the battery to accept a charge again.

Maybe this is it?

The Optimate chargers in fact do this, but you'd not expect the battery to remain at 16 volts once the charger is switched off.

 

[rbcoomer]

Are we there yet?

 

[jimmy_the_builder]

Are we there yet?

Yes we are, whew! It turns out that I've got a duff voltmeter - so total forum respect to Pete who first asked the question and Mark who suggested the BATT indicator about 100 posts ago.

Using the _good_ voltmeter, the battery is showing 13.1v. I guess my supplementary question is - how can I tell if this battery is definitely u/s - will the unloaded voltage drop over a relatively short period of time?

Cheers
Jimmy

(I think I need another cup of tea after all this high drama)