Nicholas123
N/A
This is probably a crackpot idea but could you connect say two 3/4 amp battery chargers to one battery & get a combined charge of 7/8 amps & does anybody know if it would harm either the battery chargers or the battery?
Using two battery chargers
- Thread starter Nicholas123
- Start date
halcyon
Well-Known Member
Are you talking basic simple charger, or one with regulation ?
It can work, but with problems, battery charger hunting.
You may get 4 amp charge instead of the 2 amp you normally get from a 4 amp charger.
Brian
William_H
Well-Known Member
2 battery chargers
Much depends on the style of battery charger. If they are the crude old constant current high voltage type of years ago then no problem and yes you should double the current in. They work on the principal that without a load they generate perhaps 17volts. This is often in the form of pulsed DC from the AC wave. They rely on the internal resistance of the charger to reduce the voltage to that of the battery because of the current flow. They tend therefor to pump in current regardless of charge state and can overcharge the battery. (not a 3/4 amp charger on a big battery of course.
When electronics became so cheap we got firstly the constant voltage charger which works like your alternator regulator on your car. This produces a precise 14v and the battery takes charge depending on the charge state. Usually good at first diminishing with charge. If you put 2 of these in parallel the battery will only take what it wants so may with a very flat battery use the higher capability of 2 chargers but as the charge current diminishes 2 will do no better than one.
The modern chargers tend to provide a higher voltage to get more charge current into the battery in the bulk charge mode then goes down for float. If you have 2 identical chargers then again they may provide more charge to a flat battery initially but the value of 2 chargers will go as charge current falls. They may also tell one another that the battery is fully charged so go to maintenance stage too soon.
I don't think the chargers will damage one another but you do need an amp meter to monitor how much goes into the battery to then just the worth of 2 chargers.
Just an opinion I would fit an amp meter and just see how one charger goes. olewill
Much depends on the style of battery charger. If they are the crude old constant current high voltage type of years ago then no problem and yes you should double the current in. They work on the principal that without a load they generate perhaps 17volts. This is often in the form of pulsed DC from the AC wave. They rely on the internal resistance of the charger to reduce the voltage to that of the battery because of the current flow. They tend therefor to pump in current regardless of charge state and can overcharge the battery. (not a 3/4 amp charger on a big battery of course.
When electronics became so cheap we got firstly the constant voltage charger which works like your alternator regulator on your car. This produces a precise 14v and the battery takes charge depending on the charge state. Usually good at first diminishing with charge. If you put 2 of these in parallel the battery will only take what it wants so may with a very flat battery use the higher capability of 2 chargers but as the charge current diminishes 2 will do no better than one.
The modern chargers tend to provide a higher voltage to get more charge current into the battery in the bulk charge mode then goes down for float. If you have 2 identical chargers then again they may provide more charge to a flat battery initially but the value of 2 chargers will go as charge current falls. They may also tell one another that the battery is fully charged so go to maintenance stage too soon.
I don't think the chargers will damage one another but you do need an amp meter to monitor how much goes into the battery to then just the worth of 2 chargers.
Just an opinion I would fit an amp meter and just see how one charger goes. olewill
halcyon
Well-Known Member
ghostlymoron
Well-Known Member
Yes, I'd call it modern. My best charger I've had since 1972. It still works, doesn't freak out at a very low voltage and is suitable for 6 or 12 volts. I've also got a C-Tek from Aldi's.You class those as modern ? I making them 28 years ago
Brian
Nicholas123
N/A
This is all academic now gentlemen as my Aldi battery charger seems to have met it's match & given up the ghost.Thanks for the info anyway gentlemen.
Just for the record my simple remaining battery charger from the 70's is also doing a good job.So much for modern technology!
& come to think of it,now into rant mode......I had a super dupe Boch or is that Bosh battery charger on my boat in Belgium.It looked brand new & I doubt could have been used much but that conked out after a few days of continuous connection trying to maintain current to run the fridge
Just for the record my simple remaining battery charger from the 70's is also doing a good job.So much for modern technology!
& come to think of it,now into rant mode......I had a super dupe Boch or is that Bosh battery charger on my boat in Belgium.It looked brand new & I doubt could have been used much but that conked out after a few days of continuous connection trying to maintain current to run the fridge
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halcyon
Well-Known Member
Just for the record my simple remaining battery charger from the 70's is also doing a good job.So much for modern technology!
& come to think of it,now into rant mode......I had a super dupe Boch or is that Bosh battery charger on my boat in Belgium.It looked brand new & I doubt could have been used much but that conked out after a few days of continuous connection trying to maintain current to run the fridge
Funny you say that, back in the mid 90's I looked at changing over from transformer to switch mode chargers. Decided I did not like switch mode for marine chargers, so stopped making them. To-day most of the transformer chargers we made appear to be still running, some 28 years old, most switch mode chargers that came in have had to be changed.
Old thing, marketing is better than the technology.
Brian
alahol2
Well-Known Member
This is all academic now gentlemen as my Aldi battery charger seems to have met it's match & given up the ghost.Thanks for the info anyway gentlemen.
Just for the record my simple remaining battery charger from the 70's is also doing a good job.So much for modern technology!
& come to think of it,now into rant mode......I had a super dupe Boch or is that Bosh battery charger on my boat in Belgium.It looked brand new & I doubt could have been used much but that conked out after a few days of continuous connection trying to maintain current to run the fridge
Talking of failing chargers...
A friend has killed two Aldi chargers by starting the boat engine whilst the charger was connected to the battery. This morning I killed my old Halfords charger by starting my wife's car whilst the charger was connected. I took it apart and the internal fuse was OK and I couldn't see anything else that may have melted.
What is likely to be the cause? Would it be a major draw of current during starting or maybe a back current when the alternator starts up? Any ideas?
William_H
Well-Known Member
Battery chargers
I really like the old style chargers. They have just a transformer and a rectifier. They may also have a resistor to limit current or may rely on the internal resistance of the transformer. The rectifier can be a half wave type ie just one diode or full wave type with 2 diodes (and 2 secondary windings) or 4 diodes usually in a bridge in one package.
The charger without load produces a voltage which starts from 0 and rises in a sine wave rate up to a peak then drops again to 0. The peak voltage might be around 20v. This rise and fall occurs at 50 times per second for a half wave rectifier and 100 times per second for full wave rectifier. (the ac wave going from + to-ve means with half wave only the +ve half of the wave is used. With full wave the -ve half of the AC is turned around to be +ve and so is added in between the +ves.
Now when this rectifier output is applied to a 12v lead acid battery we get no current flow until this rising voltages exceeds the battery inherent voltage. Current then rises as the voltage wave rises then falls until the wave voltage falls below the battery inherent voltage.
The current that flows into the battery at the peak of the wave depends on the capability of the transformer to provide the current. Usually it is limited by the transformer or an external resistor. (often adjustable in old chargers). As the inherent voltage of the battery rises so less current goes into the battery because the amount of time the current flows is less and the difference between the battery voltage and the peak becomes less.
However there will always be a charge current typically dropping to about 40% from a half charged battery to fully charged. That means that you can get a faster charge to fully charged but does also mean that you can overcharge the battery and cook it.
Another interesting aspect of this type of charger is that you need an analogue meter with a needle to measure the current. The inertia of the needle means that it takes up an average current measurement which is exactly what you want to know. Digital multimeter will not know at what part of the pulse it is measuring so will give erratic readings.
Beware a battery which will not take a charge can develop a quite high voltage across the terminals when on this kind of charger. This voltage can kill devices connected to the battery when on charge.
Maybe this treatise will help alahol2 to fault find his hopefully simple charger. olewill
I really like the old style chargers. They have just a transformer and a rectifier. They may also have a resistor to limit current or may rely on the internal resistance of the transformer. The rectifier can be a half wave type ie just one diode or full wave type with 2 diodes (and 2 secondary windings) or 4 diodes usually in a bridge in one package.
The charger without load produces a voltage which starts from 0 and rises in a sine wave rate up to a peak then drops again to 0. The peak voltage might be around 20v. This rise and fall occurs at 50 times per second for a half wave rectifier and 100 times per second for full wave rectifier. (the ac wave going from + to-ve means with half wave only the +ve half of the wave is used. With full wave the -ve half of the AC is turned around to be +ve and so is added in between the +ves.
Now when this rectifier output is applied to a 12v lead acid battery we get no current flow until this rising voltages exceeds the battery inherent voltage. Current then rises as the voltage wave rises then falls until the wave voltage falls below the battery inherent voltage.
The current that flows into the battery at the peak of the wave depends on the capability of the transformer to provide the current. Usually it is limited by the transformer or an external resistor. (often adjustable in old chargers). As the inherent voltage of the battery rises so less current goes into the battery because the amount of time the current flows is less and the difference between the battery voltage and the peak becomes less.
However there will always be a charge current typically dropping to about 40% from a half charged battery to fully charged. That means that you can get a faster charge to fully charged but does also mean that you can overcharge the battery and cook it.
Another interesting aspect of this type of charger is that you need an analogue meter with a needle to measure the current. The inertia of the needle means that it takes up an average current measurement which is exactly what you want to know. Digital multimeter will not know at what part of the pulse it is measuring so will give erratic readings.
Beware a battery which will not take a charge can develop a quite high voltage across the terminals when on this kind of charger. This voltage can kill devices connected to the battery when on charge.
Maybe this treatise will help alahol2 to fault find his hopefully simple charger. olewill
lookoutThere_54
New Member
where did you buy one of those?
halcyon
Well-Known Member
This applies to small car type chargers, marine chargers from around 1980 on have had a controller fitted. Either a fixed 13.6 volt, or multi-stage, we introduced this type back 1984 / 5. The multi-stage charged up to 14.2 volt, then dropped to 13.6 float / power supply mode.
The available current with transformer chargers is set by the core size, this limits the available power, thus amperage, the voltage you see is set by the battery, not the charger. As the battery recharge level comes up, so does the voltage to carry out the chemical conversion. The transformer having a fixed power, current reduces as voltage increases, thus you see the tail off in small chargers. Marine chargers normally had a larger transformer rating, thus the need for a voltage regulator to limit top end voltage. Normally the charger would be 10% of battery bank size, so for 200 amp hour you fitted a 20 amp charger. This allowed a 20 amp nominal current to recharge a flat battery in around 10 hours, normally a lot shorter as the battery was not flat. When 14.2 volt was reached, equalisation charge was not needed as the battery had been deep charged, thus avoiding excessive water lose. It would have been better to charge up to 14.4 volt ( above this the voltage rises steeply for little extra recharge ) but it was possible for old batteries to just reach 14.4 volt. Thus a bad battery may not drop down to float charge, by setting 14.2 volt it ensured you reached float charge, but at the expense of a little capacity.
So if your boat was fitted with a transformer charger check what system.
Brian
Nicholas123
N/A
I don't know about alahol2 but that sounded like rocket science to me.....thanks for trying to explain it anyway William.My Boch fancy charger like alahol2's showed no sign of damage inside when I looked to see if there was a fuse that had blown.None of the people who I spoke to who I presumed knew more about these things than me had a clue about what to do so I binned it.
Got my money back for the Aldi charger & my battery still refuses to 'come alive.'(it seems to show progress on first removing the old charger left on overnight but after a few minutes that voltage gain seems to disappear & it reverts to between 11.5 & 12v's according to my Aldi Battery & Alternator tester).
I am now left with a desulpherizer as my only means of resurrecting this battery it seems to me,any thoughts on that?
Regards Nicholas.
Nicholas123
N/A
I was wondering about that water loss business.......this battery of mine would bubble & make an incredible collection of noises like a stew simmering when under charge & it is described as maintenance free-Calcium but I noticed a little vent so the gasses must be able to escape to the outside world.Does that not mean that it could boil dry or 'cook' as William put it?
PS:I always turned off the charger after I had heard it 'stewing' for a little while for fear of it exploding because of sulpherization possibly blocking up the plates.Did I do the right thing?
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