Rotating Batteries

[radioman]

Originally Posted by yurtle

I've never noticed this, but wasn't really paying attention either. Middle batteries are protected from the environment more that the outer batteries. Only one side is exposed, while the other batteries have two sides exposed. Could be temperature related during charging, storage, and use?

Next time I fill mine, I'll see if I notice a difference within the normal pack and the two extras, which are exposed on all four sides. Maybe gassing occurs more on the "protected" batteries than on the ones with more exposure?

I believe you are absolutely right. I remember a shelf mounted power supply which had two batteries in series and one was against a warm service. The two batteries always had a slightly different amount of charge voltage because of the difference in temperature. Temperature affects the specific gravity and therefore the charging current effect on different batteries connected in series. The best way for arranging a bank of batteries would be in a line or spacing between them but you can't do that in a golf cart because of space limitations.. There might be some merit in rotating batteries but I suspect the gain would not be worth the work.

[JohnnieB]

Originally Posted by radioman

I believe you are absolutely right. I remember a shelf mounted power supply which had two batteries in series and one was against a warm service. The two batteries always had a slightly different amount of charge voltage because of the difference in temperature. Temperature affects the specific gravity and therefore the charging current effect on different batteries connected in series. The best way for arranging a bank of batteries would be in a line or spacing between them but you can't do that in a golf cart because of space limitations.. There might be some merit in rotating batteries but I suspect the gain would not be worth the work.

I agree that the center batteries get warmer and warmer chemistry is more reactive, so temperature compensated chargers reduce the charge voltage by 0.0028V for every 1°F rise in temperature. Since all the batteries have the same current flow through them for the same length of time, wouldn't the warmest batteries, having the most reactive chemistry, have the fullest charge?

That might explain having a lower On-charge voltage and using more water, since they would be the first to reach the gassing stage and might go deeper into it, but I don't know one way or the other.


Personally, I'm too lazy to juggle 70 pound batteries around, so if my battery pack gets too far out of balance, I'm going to use equalization charging or individual charging to get them back in line.

[B-Dubya]

I am new to working with DC power so please correct me if I am wrong.
The current measurement most people refer to is taken in sires of the entire battery string and is just a sum of the string. Isn't it possible that due to internal battery factors i.e. sulfation that the current could be different along the pack? Once the charging current falls below 10 amps you could insert your current meter between various batteries along the string and come up with differ values?

[JohnnieB]

Originally Posted by B-Dubya

I am new to working with DC power so please correct me if I am wrong.
1. The current measurement most people refer to is taken in sires of the entire battery string and is just a sum of the string.
2. Isn't it possible that due to internal battery factors i.e. sulfation that the current could be different along the pack?
3. Once the charging current falls below 10 amps you could insert your current meter between various batteries along the string and come up with differ values?

1. Total current flows through every component in a series string. It is the sum of the voltage drops across each component in a series string that is equal to the applied voltage.
2. No, the current is the same at all points in a series circuit. However, the voltage across each component in the series string can be different and the voltage On-Charge battery voltage will vary according to the battery's internal resistance, which depends of the sulfation of the plates, state of charge, temperature of the electrolyte and some other factors.
3. No need to. One ammeter anywhere in the circuit will tell what the amp flow is at any other point in the circuit.

You are on the right track, but either mixing up Volts and Amps or series and parallel circuits. Hang in there, the fog will lift.

[yurtle]

Voltage drops at any point in a series circuit that has resistance. Current in = current out. That's the law.

[720Deere]

Thanks for the lively and informative discussion! Things were pretty boring on the forum yesterday so I thought I would ask a stupid question to stir things up.

Just to clarify something, the batteries in question are number 3 & 4 going from 36+ to 36- cables to the controller. The would be the 2 batteries on the far left of the cart which to me is the middle of the series. Temperature should be no more issue for them than it is for the two on the right side.

[radioman]

Some carts have six or more batteries. What about the ones surrounded by batteries on three sides?

[yurtle]

Six battery packs have two that are surrounded on three sides.

[radioman]

I don't think whatever a battery's position in the bank of a set of good batteries properly installed (no taps to power lower voltage devices) in a typical golf cart is going to make any significant difference.

[gornoman]

The amount of water a golf cart battery consumes is directly related to how difficult it is to fill. The difficult ones ALWAYS require more service. Murphy's Law.