As usual, the answer depends. In this case, the type of battery will give you different answers. Here's some numbers that I generated based on the following assumptions:
1) the load is 60A @ 50v (12 volt batteries average 12.5 in use)
2) the Peukert exponents used were 1.3 for wet cell, 1.1 for AGM and 1.02 for Lithium.
3) numbers are for 100Ah @ 50v which is 5000wh per bank or 10,000Ah combined. capacities are to 100% DOD.
Here we go...
Wet cell 5KWh - 47.5 minutes, 2 banks - 94.9 minutes, 10KWh - 116.8 minutes
AGM 5Kwh - 78 minutes, 2 banks - 156 minutes, 10KWh - 167.2 minutes
LiFePO4 5KWh - 95.2 minutes, 2 banks - 190.3 minutes, 10KWh - 193 minutes
We can see that for wet cells, a single bank has over 20 minutes more rated capacity than the 2 small banks at this load. AGMs only gain about 10 minutes by combining the banks and Lithium gain less than 3 minutes by bringing the banks together. The Lithium batteries have twice the load capacity of the wet cells with exactly the same standard rated capacity.
Now let's factor in depth of discharge using 50% for wet cells, 65% for AGM and 80% for LiFePO4.
Wet cell 2.5KWh - 23.7 minutes, 2 banks - 47.5 minutes, 5KWh - 58.4 minutes
AGM 3.25Kwh - 50.7 minutes, 2 banks - 101.4 minutes, 6.5KWh - 108.7 minutes
LiFePO4 4KWh - 76.1 minutes, 2 banks - 152.2 minutes, 8KWh - 154.4 minutes
So, one can see that the same "size" batteries can have almost three times the usable capacity depending on the technology. The effects are more pronounced for small battery banks, as illustrated above. Doubling the size of the bank again reduces the advantages of each technology, but there is still a big difference. One should consider this when evaluating the purchase price of batteries; in some cases, more expensive batteries may be cheaper per mile of range.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@
>
> 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
>
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