Do I have a battery problem?

[lynallbel]

Ref Tayna sending back batteries is a pita.
Plus if they test it with their kit, and its says it is okay you are respsonsible for postage both ways.

My advice is in future buy your batteries from somewhere local, I now use Halfords with a trade card.

 

[Quandary]

So you think your wall mounted charger can charge your battery, but your alternator somehow cannot?

A week ago, no, and when it was suggested in posts 2,4 and 5 I was sceptical, i had never even heard the expression 'dumb charger',but now it seems to have worked and the battery seems to be holding charge, now 12.95 after resting 40hrs.

I suspect there is a problem with your boat.
How does the alternator charge the engine battery and the house batteries? VSR? Does it work?

So far it has, it is only this one battery that had failed to hold, now after a couple of attempts to fully charge it, it looks as if it might.

 

[Refueler]

So you think your wall mounted charger can charge your battery, but your alternator somehow cannot?

I suspect there is a problem with your boat.
How does the alternator charge the engine battery and the house batteries? VSR? Does it work?

I have had that suspicion all way through - that on-board charging has a fault.

The info that the 3rd battery has been added - this might play with my question of which battery is the sense lead connected to control charging ? If the VSR system was installed during the 2 battery period - then if sense fitted - then it would be connected to one of those two. If a 3rd battery is added such as the 'problem' one and sense is still left on the original two ?
My idea would be to put sense lead to the hardest worked battery ... which I generally regard as the starter battery.

I'm only thinking out loud as I don't use VSR ... needs someone with better knowledge of VSR and Sense lead etc.

 

[PaulRainbow]

I have had that suspicion all way through - that on-board charging has a fault.

The info that the 3rd battery has been added - this might play with my question of which battery is the sense lead connected to control charging ? If the VSR system was installed during the 2 battery period - then if sense fitted - then it would be connected to one of those two. If a 3rd battery is added such as the 'problem' one and sense is still left on the original two ?
My idea would be to put sense lead to the hardest worked battery ... which I generally regard as the starter battery.

I'm only thinking out loud as I don't use VSR ... needs someone with better knowledge of VSR and Sense lead etc.

That would be wrong in every installation i can think of. The starter battery starts the engine, it's barely depleted and quickly recharged. The domestic bank is supplying all other loads and this is where the sense wire should be connected.

That said, with a VSR in the system, the VSR will close soon after starting the engine and the batteries will all be in parallel, so it won't make any difference where the wire is connected, either bank or machine sensed.

 

[PaulRainbow]

So far it has, it is only this one battery that had failed to hold, now after a couple of attempts to fully charge it, it looks as if it might.

Your previous posts suggest the alternator is only outputting 13.5V. I would suggest that you double check that and if that is indeed the case you need to look into rectifying that, 13.5 is not enough to fully charge your batteries. Also, double check what voltages the mains charger is outputting. Have you said what the mains charger is (save me reading back through the whole thread) ?

 

[Quandary]

Your previous posts suggest the alternator is only outputting 13.5V. I would suggest that you double check that and if that is indeed the case you need to look into rectifying that, 13.5 is not enough to fully charge your batteries. Also, double check what voltages the mains charger is outputting. Have you said what the mains charger is (save me reading back through the whole thread) ?

What I said was that my recollection was that the voltmeter on the panel which I believe monitors the domestic batteries was showing 13.5 with the engine running but it is analogue and perhaps not that accurate, similar to my memory. The last mains charger used is unbranded but probably purchased in Halfords or similar 48 years ago when I was restoring a Jaguar XK140, it has a high/ lo switch which will not shift but if I place a brick on top of it it shows 14. 4 volts when connected to the battery terminals. There is a newer digital read out at the back (the same brand as the VSR), it does not always show a reading but i believe may monitor the engine start battery. There was a gas monitor terminal on the engine battery but I have disconnected that long since in case it was contributing to the problem. There is a switch that can be inserted and turned to energise the engine battery if that is flat but I have never needed to use it.
Edit -- more diligence reveals the charger make is Bradex made in Bradford way back in the day when such things were made in the UK.

 

[PaulRainbow]

My advice in post #45 still stands, you should check the charging voltages of all onboard charging sources. Feel free to ignore that if you choose, but if the alternator really is charging at 13.5V, start saving up for some more new batteries.

 

[Quandary]

Questions before I go back over to the boat tomorrow
If the system maintains a resting battery voltage above 12.7 is there a problem?
If a battery charged with a voltage of 14.4 shows 14.2 on disconnection and 13.0 after resting for 48 hours is it now holding charge?
If the alternator is providing a voltage above 13.7 will it charge the batteries?
How accurate can I expect a digital multimeter to be?

 

[TernVI]

Questions before I go back over to the boat tomorrow
If the system maintains a resting battery voltage above 12.7 is there a problem?
If a battery charged with a voltage of 14.4 shows 14.2 on disconnection and 13.0 after resting for 48 hours is it now holding charge?
If the alternator is providing a voltage above 13.7 will it charge the batteries?
How accurate can I expect a digital multimeter to be?

Probably not.
Yes.
Only extremely slowly. As in days/weeks not hours.
You can expect whatever you care to, but when things don't stack up, check the meter.

When there is an AC component, noise, spikes what have you on top of a DC level, cheap meters may be fooled. When the battery is low they go bad. I've got several of those £5 Maplin type meters, they usually agree +/- 2 least significant digits with the expensive meters.
For a rough check in the right ballpark, a brand new alkaline PP3 battery should be around 9.5V at no load.

If things still don't add up, I either find a better way to measure it (like the difference between two voltages) or get the scope out.

 

[Refueler]

Generally I agree with previous answer .... but here goes :

Questions before I go back over to the boat tomorrow
If the system maintains a resting battery voltage above 12.7 is there a problem?

Ok - here's quote from a Battery manufacturers site :
"A fully-charged 12-volt battery, allowed to “rest” for a few hours (or days) with no load being drawn from it (or charge going to it), will balance out its charge and measure about 12.6 volts between terminals. When a battery reads only 12 volts under the above conditions, it's almost fully depleted. "
So answer is likely its OK.

If a battery charged with a voltage of 14.4 shows 14.2 on disconnection and 13.0 after resting for 48 hours is it now holding charge?

Again look at above .. I'd be happy with that !

If the alternator is providing a voltage above 13.7 will it charge the batteries?

First you say 'above 13.7V' ??

Quote from Auto Electrics site :
"A fully charged battery should read over 12.6 volts. The actual output voltage produced by the alternator will typically be about 1-1/2 to 2 volts higher than battery voltage. At idle, most charging systems will produce 13.8 to 14.3 volts with no lights or accessories on. "

Yes it will BUT if its 13.7V - probably not fully - the charger needs to be at a higher voltage than the battery to overcome battery resistance to charge. This resistance to charge gets greater and greater as the battery charges up - this is seen on the meter by the amps decreasing as charge level increases. Think of it .... charger at 14.5v ... battery at 12v ... charger has relatively easy time of its and pours the charge in at high rate ... but as the battery charge level goes up - the 14.4V has less 'overhead' to push the charge in .. so it each final % of charge takes significantly longer than at start.
But if that charger does not have that decent overhead ... usually charger si about 14.5+ V ... then you start at a low overhead and as battery charges - if the charger is only putting out 13.7V - then you could find battery only gets into the 90+ % region or less.

How accurate can I expect a digital multimeter to be?

Until recently I owned laboratories and meters are literally in each room. We had expensive calibrated jobs and for non important work cheap off the shelf DIY shop jobs ... in fact I have two on my desk now from one of my ex labs. Comparison of our expensive Standards meters and the cheapo chinese ? For practical purposes 'zero'. They were surprisingly accurate. They all in fact better than the Specs parameters quoted in their docs.

 

[Refueler]

That would be wrong in every installation i can think of. The starter battery starts the engine, it's barely depleted and quickly recharged. The domestic bank is supplying all other loads and this is where the sense wire should be connected.

That said, with a VSR in the system, the VSR will close soon after starting the engine and the batteries will all be in parallel, so it won't make any difference where the wire is connected, either bank or machine sensed.

Ok ... fair enough ...

I suppose because I sail in the region that you barely need lights etc. as sun sets very late .. rises very early, barely use domestic battery in fact - my starter battery is hardest worked.

Just thinking out loud as its strange he has one battery that doesn't charge fully.

 

[Quandary]

Thanks guys, I think we may have debated this enough and I know a bit more now, I can appreciate how irritating it can be dealing with an idiot.
I will check the alternator output, probably tomorrow when I take the suspect battery back, this will be a lot easier at the batteries than at the alternator itself.
But the explanation given in the first couple of posts still appeals to me, I seem not to be the first to experience this problem with a new battery.
This morning after 60 hours at rest the voltage which started at 14.2 now reads 12.87, the canal is closed tomorrow so I plan to spend a few hours at the boat checking stuff then and off out to the wild ocean the next day.

 

[Quandary]

The problem battery is back in the boat, when I started the engine and ran it at 2000 revs the multimeter was showing 14.2v across the starter battery terminals and after a time the voltage in the house bank which was reading 12.7 began to rise also. Shore power connected overnight to consolidate.
My conclusion, those who advised that the new battery needed a heavy charge to encourage it to hold charge seem to have been right, I was not aware of this possibility until I asked here so many thanks, my alternator is fine and not the source of the problem. I will keep testing the voltage in this battery for a while before I allow it to work on it own without supervision.

 

[VicS]

The problem battery is back in the boat, when I started the engine and ran it at 2000 revs the multimeter was showing 14.2v across the starter battery terminals and after a time the voltage in the house bank which was reading 12.7 began to rise also. Shore power connected overnight to consolidate.
My conclusion, those who advised that the new battery needed a heavy charge to encourage it to hold charge seem to have been right, I was not aware of this possibility until I asked here so many thanks, my alternator is fine and not the source of the problem. I will keep testing the voltage in this battery for a while before I allow it to work on it own without supervision.

Thanks for the update.

Your 8 amp Optimate charger should be fine for recharging it if necessary provided it does not become so heavily discharged again. You seem to have been given some duff about it only being a 0.8 amp maintenance charger.

Have you any idea why the battery became so heavily discharged? You don't want that to happen again.

 

[PaulRainbow]

Thanks for the update.

Your 8 amp Optimate charger should be fine for recharging it if necessary provided it does not become so heavily discharged again. You seem to have been given some duff about it only being a 0.8 amp maintenance charger.

Have you any idea why the battery became so heavily discharged? You don't want that to happen again.

Ever keen to earn a browny point i see. Did anyone actually say the Optimate was an 0.8A maintenance charger ?

 

[PaulRainbow]

The problem battery is back in the boat, when I started the engine and ran it at 2000 revs the multimeter was showing 14.2v across the starter battery terminals and after a time the voltage in the house bank which was reading 12.7 began to rise also. Shore power connected overnight to consolidate.
My conclusion, those who advised that the new battery needed a heavy charge to encourage it to hold charge seem to have been right, I was not aware of this possibility until I asked here so many thanks, my alternator is fine and not the source of the problem. I will keep testing the voltage in this battery for a while before I allow it to work on it own without supervision.

Good to read you made the checks and found that the alternator is putting out a reasonable voltage, you can rest easy on that score. I expect you'll have no further problems.