Hey, I just purchased four trojan 6v deep cycle 225ah batteries from someone who was planning on adding solar to their camper but didn't get around to it. He had the battery shop he purchased them from make some cables and hooked them up in series but he never got around to hooking anything to the bank before deciding to sell them. I disconnected the batteries to check the voltage and to move them into my car and now back at home I'd like to top them off with my 2/10/50amp auto/manual shumacher battery charger. I've never used the charger for 6v batteries before but it does have a setting on the automatic side of things for charging 6v at 10amps. My main question is if its best for me to hook them up in series again and charge them all at the same time as a 12v battery bank or if I should charge them separately as 6v? I'm planning on only using two of these batteries in my camper and selling the other two to make some of my money back if that makes any difference in how I should charge these. Thanks!
Charging several 6v batteries with battery charger
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MrNoodly
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Hook them up in series and charge them like 12V batteries. That's what would be happening if the solar was all hooked up and a controller was doing the charging.
https://www.atbatt.com/how-to-wire-6v-batteries-in-series-or-parallel-configuration/
https://www.atbatt.com/how-to-wire-6v-batteries-in-series-or-parallel-configuration/
MrAlvinDude
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Charge each 6V battery, to exactly the same charge. Let each battery sit for a day or so, and then measure the voltage.
If the voltages are very close, like 6.00 Volt (use multimeter with at least two digits). Then you can make them into 2x 12V systems.
If it becomes too difficult to get them to the same 6.00V charge, (or you do not have a 2 digit multimeter) then once they are very close to the same voltage (within 0.2 volt for instance), then parallel all of the 6V batteries, and let them sit for 24-48 hours or so.
This duration of sitting time, while they are paralleled, will help them get to exactly the same voltage. So after a while they will all (slowly) get to the same 6.00V (or whatever voltage they started out to be very close to, like 6.88 or 5.95 or...)
Batteries that are later connected in series, MUST be at an equal voltage, when they are connected in series. Or one of the batteries will tend to get overcharged.
Like if one 6V battery is at 6.2 and the other 6V is at 6.8, so the difference is 0.6V
and you then push power into them, while they are in series, then the difference between them will remain.
Most modern chargers will provide between 13.8 and 14.6V during the charge cycle. So lets say they get to 13.8V, and thus each 6V battery should be at 13.8 / 2 = 6.9 each.
HOWEVER, because there will still be a 0.6V difference between the batteries, one will actually be 6.6V and the other will be 7.2V.
And 7.2 volt is too much for a 6V battery.
Over charging a battery is NOT a good thing. Especially not if they are sealed batteries anyway.
If they are open cell, then the batteries will go into ''cell equalizing mode', which means that you need to make sure to check water levels and acid levels afterwards.
Sealed batteries must NOT be 'cell equalized' (over charged). As it will create over-pressure, and will cause release of gasses that should NOT be released from sealed batteries. Gasses in sealed lead acid batteries is an integral part of the normal charge cycle, and once they are released into the outside, the sealed battery can no longer be charged properly.
In other words, overcharging a sealed battery (typically to over 14.8V)(or 7.3V for a 6V battery) WILL cause permanent damage to the charge ability of a sealed battery.
So in short.
- Charge the 6V batteries to the same 6.00V charge.
- Parallel all batteries for some time
- then create 2x 12V batteries by connecting 2 6V batteries in series.
When in use. Measure the actual voltage of each 6V battery, from time to time. And if they become too far apart from the same 6.00V reading. Then put the 2 6V batteries in parallel again, and let the get to the exact same voltage again. And then they are good to go back to create a 12V battery again.
Does all of this make sense to you?
If the voltages are very close, like 6.00 Volt (use multimeter with at least two digits). Then you can make them into 2x 12V systems.
If it becomes too difficult to get them to the same 6.00V charge, (or you do not have a 2 digit multimeter) then once they are very close to the same voltage (within 0.2 volt for instance), then parallel all of the 6V batteries, and let them sit for 24-48 hours or so.
This duration of sitting time, while they are paralleled, will help them get to exactly the same voltage. So after a while they will all (slowly) get to the same 6.00V (or whatever voltage they started out to be very close to, like 6.88 or 5.95 or...)
Batteries that are later connected in series, MUST be at an equal voltage, when they are connected in series. Or one of the batteries will tend to get overcharged.
Like if one 6V battery is at 6.2 and the other 6V is at 6.8, so the difference is 0.6V
and you then push power into them, while they are in series, then the difference between them will remain.
Most modern chargers will provide between 13.8 and 14.6V during the charge cycle. So lets say they get to 13.8V, and thus each 6V battery should be at 13.8 / 2 = 6.9 each.
HOWEVER, because there will still be a 0.6V difference between the batteries, one will actually be 6.6V and the other will be 7.2V.
And 7.2 volt is too much for a 6V battery.
Over charging a battery is NOT a good thing. Especially not if they are sealed batteries anyway.
If they are open cell, then the batteries will go into ''cell equalizing mode', which means that you need to make sure to check water levels and acid levels afterwards.
Sealed batteries must NOT be 'cell equalized' (over charged). As it will create over-pressure, and will cause release of gasses that should NOT be released from sealed batteries. Gasses in sealed lead acid batteries is an integral part of the normal charge cycle, and once they are released into the outside, the sealed battery can no longer be charged properly.
In other words, overcharging a sealed battery (typically to over 14.8V)(or 7.3V for a 6V battery) WILL cause permanent damage to the charge ability of a sealed battery.
So in short.
- Charge the 6V batteries to the same 6.00V charge.
- Parallel all batteries for some time
- then create 2x 12V batteries by connecting 2 6V batteries in series.
When in use. Measure the actual voltage of each 6V battery, from time to time. And if they become too far apart from the same 6.00V reading. Then put the 2 6V batteries in parallel again, and let the get to the exact same voltage again. And then they are good to go back to create a 12V battery again.
Does all of this make sense to you?
Spaceman Spiff
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whodunit said:
Four 6 volt batteries hooked up in series = 24V.
- Series = voltages add.
- Parallel = amps add.
For a 12V battery bank (or to charge them with a 12V charger) you need to pair them in series and parallel the two pairs together or charge each pair separately.
My recommendation would be to charge each battery separately and pick the best matched two for your bank.
MrAlvinDude said:
Thanks for the thorough response! Yep I think that all makes sense. I didn't know that the voltage difference remains even after the batteries are connected in series so that's something new I learned. Since these batteries have been sitting connected to each other they are all the same voltage. They are also flooded lead so they are not sealed. Does that mean its safe to just charge them all together in series + parallel combination? or should I still charge them individually? I do like spaceman spliff's idea of picking the best pair of the four to keep for myself. just incase some are healthier than others.
MrAlvinDude
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So long as all 6V batteries have the same voltages (measure each battery using at least 2 digits, like 6.00V), then it does not matter if you charge them in series or in parallel.
The voltage of each battery can still be measured even if they are all connected in series (to form a 24V battery). Just remember that it is best to measure the voltage AFTER the batteries have settled.
It takles about 24-36 hours for the battery voltage to settle, after it has been used or charged some.
As the batteries are flooded batteries, you should measure the acid balance. both before and after they have been charged the first time.
Also remember to check the water levels, before you charge. And if the charge takes a very long time, check water levels, now and then, during the first charge.
When you measure each battery, after they have been charged, and settled. Then I believe that you can see which two are best matched (have close to the same resting voltage).
The voltage of each battery can still be measured even if they are all connected in series (to form a 24V battery). Just remember that it is best to measure the voltage AFTER the batteries have settled.
It takles about 24-36 hours for the battery voltage to settle, after it has been used or charged some.
As the batteries are flooded batteries, you should measure the acid balance. both before and after they have been charged the first time.
Also remember to check the water levels, before you charge. And if the charge takes a very long time, check water levels, now and then, during the first charge.
When you measure each battery, after they have been charged, and settled. Then I believe that you can see which two are best matched (have close to the same resting voltage).
