12 volt charging question

[ripvan1]

I have 2 x 12 volt 140ah varta (big and heavy) batteries which I am charging at home on a small domestic car charger - the first one has now been on charge now for 48 hours and the green fully charged light has yet to come on - do the knowledgeable here think the charger is not man enough for this size battery?

Took this one off charge and am now trying the other.

The b/acid looks fine and batteries would, by their condition appear to be relatively recent.

Thanks

 

[Playtime]

There are three possibilities here from the info you have given.

1. The battery was deeply discharged and has not yet achieved full re-charge. In the worst case the charger may only be charging at 1 or 2 amps and could take upwards of 100 hours to fully charge one battery.

2. The battery is dead and will never be fully charged. Even if it looks good on the outside the plates inside could be shot.

3. The charger 'green light' does not function as expected.

Do you have a multimeter or a battery hydrometer? If not, you really need to purchase one or the other to determine which of the above scenarios is correct. Halfords can supply a hydrometer and Maplins, or a good hardware store, can supply a multimeter. Each should cost well under a tenner.

If you don't want to get either then I would you suggest you leave the battery on charge for at least 100 hours, checking the water level in all cells periodically.

If you get the multimeter then you should get a reading of more than 12.8V after the battery has been resting for more than 12 hours if it is fully charged.

If you get the hydrometer thren you should get a reading of 1.265 at 80 degrees F if fully charged.

 

[ripvan1]

Thanks playtime, multimeter it is then, there was some life left in batteries when on board echo sounder and lights - but not spinning engine.

Good answer, thanks

 

[VicS]

I have 2 x 12 volt 140ah varta (big and heavy) batteries which I am charging at home on a small domestic car charger - the first one has now been on charge now for 48 hours and the green fully charged light has yet to come on - do the knowledgeable here think the charger is not man enough for this size battery?

Took this one off charge and am now trying the other.

The b/acid looks fine and batteries would, by their condition appear to be relatively recent.

Thanks

You dont say what the maximum output current of the "small" domestic car charger is.
For a 140 Ah battery you should be looking for something with a output in excess of 12 amps or charging will take a long time. Preferably 16 or 20 amps.

Sometimes a deeply discharged battery will not charge at all at low rates.


Monitoring the battery terminal volts while you are charging it will give some indication of how successfully it is being charged and as Playtime suggests the aim should be to charge until the rested voltage 12 hours or so later is in the range 12.7 to 12.8 ish volts.. More for a really good battery.

 

[bikerbill]

Check the Amps output of your charger with the multimeter which should be at least 4amps. You could take your batteries to a local garage, who will test the discharge rate of your battery and tell you if any cells are faulty. You can however, spin the starter motor briefly, having imobilised the engine first, then look to see if any cells are bubbling therefore faulty.

 

[VicS]

Check the Amps output of your charger with the multimeter which should be at least 4amps. You could discharge the battery by carefully crossing the terminals with heavy screwdrivers then look for bubbles coming from any of the cells. if there are bubbles, the battery is knackered. Take care when doing this and wear eye protection just in case.

This would be an extremely foolish thing to do. Sparks produced could easily ignite any hydrogen gas that may be present.. Bubbles will be a mixture of hydrogen and oxygen in just the right proportions for maximum effect.

A battery full of sulphuric acid exploding close to you, eye protection or not, could really spoil your day .. and a good few of those that follow too.

 

[elton]

Check the Amps output of your charger with the multimeter which should be at least 4amps. You could discharge the battery by carefully crossing the terminals with heavy screwdrivers then look for bubbles coming from any of the cells. if there are bubbles, the battery is knackered. Take care when doing this and wear eye protection just in case.

This would be an extremely foolish thing to do. Sparks produced could easily ignite any hydrogen gas that may be present.. Bubbles will be a mixture of hydrogen and oxygen in just the right proportions for maximum effect.

A battery full of sulphuric acid exploding close to you, eye protection or not, could really spoil your day .. and a good few of those that follow too.

Agreed. It would be a very dangerous, not to mention pointless. Apart from the risk of the hydrogen igniting, the screwdrivers will very quickly get hot enough to cause serious burns; the rapid discharge could easily cause the battery casing to explode, throwing acid everywhere; and the screwdrivers will most likely have their tips burnt off. Definitely not recommended.

 

[macd]

...and if you survived the explosion, you'd probably find that you'd cream-crackered your new multimeter.

 

[William_H]

A few comments to add to those already made. If the batteries, presumably both in parallel did not turn the engine then they were either very flat or cream crackered. or you have a fault in the wiring. The latter likely if other services seemed OK. Using the battery to try to start the engine is one very effective way to provide a high discharge current to test battery. Do each one separately. it is not practical to high discharge current test the batteries at home. Unless you substitute for your car batery and try to start car engine.
Yes you need to find what current your little charger is providing. If it is a really crude charger it will be pulsing current into the battery at 50 or 100 hertz rate not smooth DC. This will not be easily measured by your digital multimeter on current range because it samples the current over a short period. So meadurement will continually change. An old mechanical analogue amp meter will mechanically smooth out the variations giving an average.
Also as said the light indication on the charger may be spurious or unreliable.
The small charger should do the job but as said may take a long time to recharge big flat batteries. So at 1 amp it will take about 180 hrs to recharge each battery. At 2 amps it will still take 4 days.
If you are confident the charger is charging and leave it long enough you could then do a slow discharge test on the batteries. Connect a 12v headlamp or similar globe of 4 or more amps. This should glow brightly for more than 12 hrs if battery is any good. ie about half of claimed AH rating of the battery. if it is dud then you may only get a few hrs of glow.
That test however is only part of the story as a battery can die by way of not supplying the large start current you need for engine start. So your engine start enthusiasm will indicate condition of battery. You should occasionally check start engine on each battery alone to ensure both are able alone to start engine.
If at any time starting is bad then connect your voltmeter onto the battery terminal. (the actual post of the battery) If the voltage drops dramatically when you try to start the engine ie below 6volts then battery is bad. If the battery voltage remains near 12v then wiring or starter is bad. battery voltage can drop to 9v in normal engine cranking. good luck olewill

 

[charles_reed]

I have 2 x 12 volt 140ah varta (big and heavy) batteries which I am charging at home on a small domestic car charger - the first one has now been on charge now for 48 hours and the green fully charged light has yet to come on - do the knowledgeable here think the charger is not man enough for this size battery?

Took this one off charge and am now trying the other.

The b/acid looks fine and batteries would, by their condition appear to be relatively recent.



Thanks

The charger, assuming it's a cheap trickle charger, will NEVER fully charge batteries that size.
It was only meant to keep self-discharge, in car batteries of 1/2 that size, at bay.

You need a serious, switch-mode battery charger with an output of about 15 amps, with bulk, absorption and float charge phases to do the job.

 

[Breizh]

The charger, assuming it's a cheap trickle charger, will NEVER fully charge batteries that size.
It was only meant to keep self-discharge, in car batteries of 1/2 that size, at bay.

You need a serious, switch-mode battery charger with an output of about 15 amps, with bulk, absorption and float charge phases to do the job.

Absolutely correct. I used to direct a lot of my clients to these websites to help them understand batteries and what not to do:

http://batteryuniversity.com/

http://www.operatingtech.com/lib/pdf/A%20Guide%20to%20battery%20Charging.pdf

Also bear in mind that all batteries have a finite number of recharges in their lifetime & that the marine environment considerably shortens their useable lifetime. Extremes of temperature is bad and shortens their lifespan. Take them out in winter if they are not being used.

Breizh.

 

[JumbleDuck]

You need a serious, switch-mode battery charger with an output of about 15 amps, with bulk, absorption and float charge phases to do the job.

And yet somehow we managed to charge batteries that size ten or twenty years ago. I agree that a 4A charger is a bit weedy, though.

 

[bikerbill]

This would be an extremely foolish thing to do. Sparks produced could easily ignite any hydrogen gas that may be present.. Bubbles will be a mixture of hydrogen and oxygen in just the right proportions for maximum effect.

A battery full of sulphuric acid exploding close to you, eye protection or not, could really spoil your day .. and a good few of those that follow too.

Yeah, i'm well aware of the potential risks involved and there is a definite knack to what I said. However, I will edit my post as I don't want anybody to get hurt.

 

[charles_reed]

And yet somehow we managed to charge batteries that size ten or twenty years ago. I agree that a 4A charger is a bit weedy, though.

Amazing how we view the past through rose-tinted specs.

I, for one was, cruising in 1978 and remember the awful problems of flat batteries - I fitted an early Adverc and that made sure I had charged batteries at the expense of several burnt out diode bridges. I finally found, an 8-amp switch-mode charger the the Co-op des Pecheurs in Treboul in 1988 (for FF82).
No I think we had lower expectations and fewer electrix.

 

[bikerbill]

Agreed. It would be a very dangerous, not to mention pointless. Apart from the risk of the hydrogen igniting, the screwdrivers will very quickly get hot enough to cause serious burns; the rapid discharge could easily cause the battery casing to explode, throwing acid everywhere; and the screwdrivers will most likely have their tips burnt off. Definitely not recommended.

Yes, worst case scenario, but the method would take 2 to 3 seconds, not enough time to cause much heat. This method was taught to me 40 years ago when I was an apprentice mechanic (before H&S) We did have a specific battery discharger to do this test, but my journeyman would tell me that using heavy screwdrivers worked in just the same principal as the tool we had, as long as we took care. Anyway, I have just this minute phoned a friend who is a battery distributor, who told me that the old fashioned dischargers were banned by H&S a few years ago!!! He still has one but is not allowed to use it.

 

[JumbleDuck]

Amazing how we view the past through rose-tinted specs.

I think that generally balances out with the other natural tendency to believe that current technology - or, to be more accurate, that current technology which we ourselves own - represents the pinnacle of engineering and that nobody ever charged a battery / anchored / reefed a sail / vacuumed a carpet before.

 

[ripvan1]

Thanks all, looked at the amp output and it's 0.6/3 point something so a bit toytown I suppose.

Also bought a multimeter - that doesn't seem to work either, just sparked slightly and leads from multimeter got hot - quickly !

I assume there's some power there because of the heat

 

[Playtime]

Thanks all, looked at the amp output and it's 0.6/3 point something so a bit toytown I suppose.

Also bought a multimeter - that doesn't seem to work either, just sparked slightly and leads from multimeter got hot - quickly !

I assume there's some power there because of the heat

What were you trying to measure with the multimeter? For the leads to get hot you must have been pulling quite a few amps and that should only happen if the meter is in current (amps) mode. If you were trying to measure volts, were the leads plugged into the right holes on the meter?

If you were trying to measure current then make sure the leads are in series with the load. Never put the probes directly across the battery in current mode. All you will do is heat up the leads and blow the internal fuse in the multimeter. If the fuse doesn't blow immediately you will probably damage the meter.

Did your meter come with a manual or leaflet. If so, read it carefully and try again (if the meter still works!).

 

[VicS]

Thanks all, looked at the amp output and it's 0.6/3 point something so a bit toytown I suppose.

Also bought a multimeter - that doesn't seem to work either, just sparked slightly and leads from multimeter got hot - quickly !

I assume there's some power there because of the heat

As Playtime says read the meter instruction leaflet

You would also be well advised to read the basic stuff in the boat electrical notes on Tony Brooks' TB-Training website http://www.tb-training.co.uk/
and also the section on using meters.

Simple diagrams illustrating use of ammeter and voltmeter may help

 

[VicMallows]

And yet somehow we managed to charge batteries that size ten or twenty years ago. I agree that a 4A charger is a bit weedy, though.

Yes, because we used (I still use!) basic brute-force chargers. Usually a 15-0-15v transformer with a full-wave rectifier and nothing else. The initial charging current was limited by the transformer and wiring resistance and would tail off as the battery voltage rose, but would never reduce to a charge suitable for a permanent maintenance charge. You can certainly charge any size battery that way if you have enough time.....indeed it is often the only way to 'revive' and get a bit more life out of an otherwise dud battery which a modern (intelligent?) charger won't touch.