Batteries are normally rated at the 20-hour discharge value. So a 110AH
battery, rated at 20 hour discharge rate can deliver 5.5A for 20 hours
(5.5 x 20 = 110) before it is 100% discharged. Much as you can't bake a
cake in half the time by doubling the oven temperature, the above 110AH
battery cannot supply 11A for 10 hours, nor can it supply 110A for 1 hour.
If you parallel your two 48V strings, then each string will only be hit
for half the amps of the total current draw.
So if your controller wants 50A input, then each string will give 25A.
Here is a battery spec sheet for a 105AH 12V marine deep cycle battery:
http://www.surrette
Note the bottom of page1 has a table of discharge rates in hours. (I
attached a quick graph of the amps/discharge if it comes through)
In this case, the 105AH battery is the 20 hour rate and this is how
pretty much all batteries are marketed.
Look further down at the 1 hour rate. You will notice that the 105AH
battery is now a 38AH battery. Big difference.
So if your motor controller draws 50A from the batteries, you will get
much less than an hour, likely somewhere in the neighbourhood of 30 minutes.
In other words, if you motor on one string until it's used up, then
switch to the other, you wind up doing all your motoring at the 50A draw
rate.
But if you connect both strings together to make a 200AH pack, then each
string is hit for a 25A draw rate and according to the above PDF, that
would give you in the neighbourhood of two hours or twice as much and
effectively double your usable range for 0 penalty in weight or expense.
I have ignored depth-of-discharge issues which will further reduce your
usable range.
The important info is that by reducing the amp-draw per battery, you can
get more amps out of the whole system.
Hope the above was more illuminating than confusing.
Cheers,
/Jason
acsarfkram wrote:
> Does anyone know what the theoretical range difference would be for running two separate banks of 48 volts - 100ah each or one bank of 48 volts - 200ah?
>
> For me at this point the redundancy of two separate banks makes "feel" better. I know I'm a real techie.
>
> Mark
>
Attachment(s) from Jason Taylor
1 of 1 Photo(s)
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