battery pack reason

[tculpepper]

I know there is some reason why manufacturers and everybody that ever puts batteries in a cart, puts the batteries they do. My question is this, Why 6 volts or even 8's? Just say a 36 volt setup. Why not 3 sets of 2 12 volts run parallel then in series? Why not 3 12 volts? Why is it always 6 6v's or 8's?

[COURTESYCART]

run time.

6 6v batteries have more lead and have a higher ah rating so longer run time.
6 8v batteries have even more lead and have a total ah rating higher than the 6 6v.

ye syou cna run your 36v cart off 3 12v batteries. I have done this with car batteries just to check the elec of the cart. RUN time was pretty much nonexistance. WIth 2 year old car batts, It ran for like 15 mins.

[JohnnieB]

A 48V system is a better example since a 48V pack can be built from 6V, 8V or 12V batteries.

It takes a given amount of energy (kWh) to move a given cart from point A to point be, so the greater amount of total energy stored in the battery pack, the further the cart will go on a single charge.

Attached is a chart showing 48V packs made up of various Trojan batteries and the resulting kWh stored.
As illustrated the pack with the most kWh is the one made up with the highest AH 6V batteries.

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I don't know why EZGO chose six 6V batteries for their 36V drive systems, perhaps it was the only Deep Cycle battery available at the time.

However, we are stuck with the space available for the batteries, so that has to be taken into consideration.

Here is a chart showing various 36V battery packs.

Yes, you can run six 12V batteries in a Series/Parallel arrangement for 36V and you can get a lot of run-time from it, but getting them to fit in stock battery rack will be an issue and charging them may cause problems also.

[tculpepper]

Makes sense now. I knew there was an advantage if they did it. Thanks guys! Johnnie B., I am going to use your info in explaining this to others so I at least sound like I know what I'm talking about!

[eflyguy]

What's interesting, Johnnie, is that the 12V batteries have significantly higher energy capacity. You would get a big increase going from 6x6 to 2x3x12.

I'm not sure about charging two series packs in parallel, though. As the individual batteries age and internal resistance changes, they would charge, and discharge, at slightly different rates. In the world of RC, running parallel batteries is common, but they should be charged separately.
..a

[JohnnieB]

Originally Posted by eflyguy

What's interesting, Johnnie, is that the 12V batteries have significantly higher energy capacity. You would get a big increase going from 6x6 to 2x3x12.

I'm not sure about charging two series packs in parallel, though. As the individual batteries age and internal resistance changes, they would charge, and discharge, at slightly different rates. In the world of RC, running parallel batteries is common, but they should be charged separately.
..a

What many people overlook is the fact that a battery is a number of cells connected in series.
A 48V battery pack is twenty-four 2V cells connected in series and the cells come packaged in boxes of 3 (6V), 4 (8V) or 6 (12V).
A 36V battery pack is eighteen 2V cells connected in series and the cells come packaged in boxes of 3 (6V) or 6 (12V).
Since the AH stored in a cell depends of plate area and volume of electrolyte and the boxes are all roughly the same size, the more cells packed in the box, the smaller the cells and the fewer AH stored.

Granted, the kWh stored in the 12V batteries is higher than the kWh stored in the 6V batteries, but only because there are twice as many smaller cells, the kWh per cell in 12V batteries is considerably less.

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Charging cells in series is not ideal, but in a series string, each is allowed to reach its own On-Charge voltage. On the other hand, when cells are charged in parallel, both are locked to the same voltage and one will, or may be, overcharged while the other is undercharged. Basically the issues with series charging are less destructive than the issues with parallel charging.

You run into similar issues when discharging batteries in parallel also.

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If anyone is considering building an extended run-time 36V battery pack using six 12V batteries, check the footprint of the 12V batteries, they come in bigger boxes than either 6V or 8V batteries, so they won't fit in a stock six battery battery frame.

[sportcoupe]

Battery frame? Who needs a stinkin battery frame?

Below are 6 - "12v battery's" for a 72v pack total. Each 12v pack is made up of 6 individual 12v in parallel.

[eflyguy]

Originally Posted by JohnnieB

... check the footprint of the 12V batteries, they come in bigger boxes than either 6V or 8V batteries ...

Well, that also explains the higher kWh - bigger means more lead, more capacity.
..a

[JohnnieB]

Originally Posted by sportcoupe

Battery frame? Who needs a stinkin battery frame?

Below are 6 - "12v battery's" for a 72v pack total. Each 12v pack is made up of 6 individual 12v in parallel.

IIRC, those are 30AH batteries, so you were carrying about 13.75 kWh.