Dual 6v Battery Systems
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hawkeye
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Dual 6v Battery Systems
With a 12v system that consists of two 6v batteries, do you need a special charger? This is on a boat that does not have an alternator for charging, so it's all shorepower or solar for me. I really want to keep the cost down if possible. What about the Xantrex Truecharge 10Tb?
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Tim
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Any 12 volt charger will work if you connect the batteries in series (just the way they are connected on your boat) and attach the charger cables to the correct terminals (the positive on one battery, and negative on the second). Some chargers are set up to charge a single 6-volt battery, but if you're looking at charging on board, there's no real benefit to this.
Cheap chargers are rarely worth using, as they lack the regulation and control of better chargers and may very well damage your battery during such use. Even most so-called "trickle" chargers tend to overcharge if left continually connected, so I'd recommend charging when then need it, and otherwise leaving the charger disconnected--unless you buy a fancy (expensive) permanent charger.
Cheap chargers are rarely worth using, as they lack the regulation and control of better chargers and may very well damage your battery during such use. Even most so-called "trickle" chargers tend to overcharge if left continually connected, so I'd recommend charging when then need it, and otherwise leaving the charger disconnected--unless you buy a fancy (expensive) permanent charger.
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bcooke
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Just for a bit of battery trivia...
Warning: Obnoxious lecture follows...
All batteries are composed of individual cells linked together. The cell is usually a plate and an electrolyte material. Through a chemical process the plate becomes positively charged and the electrolyte negatively charged (or the other way around, now that I am pontificating I can't remember). The voltage produced in the individual cells is pretty consistent and depending on what type of battery i.e. lead acid, ni-cad, or whatever, the cell voltage will be between 1 and 3 volts. (I think 1.2 volts in a lead acid(car) battery and 2.2 volts in a ni-cad, then there are the exotics which I don't have a clue about.)
A battery usually has multiple cells linked in series which means the positive terminal of one cell is connected to the negative terminal of its neighbor cell in a chain of connections. The thing about connecting a battery or cell in series is that the voltages (electrical pressure if you will) add themselves together.
Battery voltages are determined by how many cells are connected in series. A six volt, a twelve volt, and a 24 volt battery are constructed exactly the same. The only differences are in how many cells are inside the battery and connected in series.
The point of my lecture is that connecting two six volt batteries in series is exactly the same as having one twelve volt battery. If you wanted a 24 volt battery you could connect two twelve volt batteries in series or four six volt batteries in series. (2x12 = 4x6=24).
That is why any twelve volt charger will work fine. The charger doesn 't know the difference (because there isn't one) between a twelve volt battery and two six volt batteries connected in series.
Just because I am on a roll... If you were to connect the cells in parallel, that is positive to positive and negative to negative, then the voltage would be the same (not added up) but the capacity would be the sum of the individual cell capacities. That is because with the like terminals connected, the cells all act as one - the cell plate area determines the capacity and when connected in parallel all those plate areas act as one big plate and the capcity is determined by the total of all the cell's plate areas. The same goes with entire batteries. Connect two batteries in parallel (again positive to positive, negative to negative) and the system capacity is the sum of all the batteries' capacities.
End of lecture. You may continue with what you were doing before.
-Britton
Warning: Obnoxious lecture follows...
All batteries are composed of individual cells linked together. The cell is usually a plate and an electrolyte material. Through a chemical process the plate becomes positively charged and the electrolyte negatively charged (or the other way around, now that I am pontificating I can't remember). The voltage produced in the individual cells is pretty consistent and depending on what type of battery i.e. lead acid, ni-cad, or whatever, the cell voltage will be between 1 and 3 volts. (I think 1.2 volts in a lead acid(car) battery and 2.2 volts in a ni-cad, then there are the exotics which I don't have a clue about.)
A battery usually has multiple cells linked in series which means the positive terminal of one cell is connected to the negative terminal of its neighbor cell in a chain of connections. The thing about connecting a battery or cell in series is that the voltages (electrical pressure if you will) add themselves together.
Battery voltages are determined by how many cells are connected in series. A six volt, a twelve volt, and a 24 volt battery are constructed exactly the same. The only differences are in how many cells are inside the battery and connected in series.
The point of my lecture is that connecting two six volt batteries in series is exactly the same as having one twelve volt battery. If you wanted a 24 volt battery you could connect two twelve volt batteries in series or four six volt batteries in series. (2x12 = 4x6=24).
That is why any twelve volt charger will work fine. The charger doesn 't know the difference (because there isn't one) between a twelve volt battery and two six volt batteries connected in series.
Just because I am on a roll... If you were to connect the cells in parallel, that is positive to positive and negative to negative, then the voltage would be the same (not added up) but the capacity would be the sum of the individual cell capacities. That is because with the like terminals connected, the cells all act as one - the cell plate area determines the capacity and when connected in parallel all those plate areas act as one big plate and the capcity is determined by the total of all the cell's plate areas. The same goes with entire batteries. Connect two batteries in parallel (again positive to positive, negative to negative) and the system capacity is the sum of all the batteries' capacities.
End of lecture. You may continue with what you were doing before.
-Britton
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hawkeye
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Thanks for the schooling Britton. Because of the large capacity of these batteries, even the $130 Xantrex charger I bought takes a real long time to fill 'er up when the're empty. I don't stay in one slip that long when I'm out and about. I would get a 15 amp charger if I had the budget, but the 10 amps from the xantrex will get me by for now.