Monday, Feb 08, 2010 at 10:19
@
John,
.....not to cause confusion.....
Very valid point indeed, and sorry for my unconventional suggestion of putting the two fuses between the two batteries.
I think this example is suited to highlight the charge/discharge imbalance situation in a more conventional circuit, because it is not only electrically perfectly balanced, it also appears balanced to the eye.
But this circuit also has a significant advantage if you look at it closer.
In a real world situation, where the negatives of both batteries are connected to chassis ground, and the positives to the charge/load wire via fuses, the circuit is not inherently balanced because the wire resistances are more of a concern than in the first circuit.
In the first circuit, all it takes for balancing, is an equal wire length of the two 'fused paths' between the batteries.
The lengths of the other two wires, one to chassis ground and the other one to the charger/load plus is totally irrelevant in terms of battery charge/discharge balancing.
This circuit allows for the battery ground to be anywhere on the chassis, totally independent from the load/charger ground.
To achieve the same grade of balancing in a more conventional circuit, the negatives of the batteries need to be wired to the same ground point, the wires need to be of equal length, and the same goes for the positive connections to the load/charger.
The only way to alleviate the potential for imbalance in a conventional circuit is to use cross connectors between the batteries minus terminals, and have the chassis connection half way between them (T split or Y split).
The same goes for the positives to the load/charger.
Or, another way to make a conventional circuit balanced is by connecting the minus cross connector to chassis ground on minus battery one, and don't connect the other battery minus to chassis at all. Similar goes for the plus side above the fuses, only in the opposite way.
The only prerequisite for balancing, is that the two paths (yellow/green) need to be of equal length and wire gauge.
See picture below:
The first circuit albeit unconventional is certainly more elegant in that it does not allow room for any wire induced imbalances as much as a conventional circuit does.
The other point of yours is quite important too, when making up your mind on the number of batteries:
...if one's down you always have another one left - make it redundant.
@olcoolone,
don't worry, they do.
Best regards, Peter
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