1 - 3 of 14 Posts

#### brian_

· Registered
Joined
·
8,629 Posts
6 x 8volt vs 4 x 12volt, if the amp/hr rating is the same then they would perform about the same also total weight of the pack, 12volt vs 8volt.
Yes, but common lead-acid deep-cycle batteries are about the same weight per battery, at the limit of what one person can reasonably handle. The different voltages just exist to break the mass of the whole battery set into suitable chunks.

In golf cars, the batteries are normally in series. A common standard setup is six 8-volt batteries. The higher-capacity option is eight 6-volt batteries. No one uses 12-volt batteries, because the capacity of four of them (of a reasonable size each) is just not enough.

Some Trojan examples, of comparable construction (not comparing a cheap 12 volt starting battery to an industrial-grade deep-cycle battery):
• 6V: T-125 240 Ah, 66 lb (30 kg), so a set of eight is 240 Ah @ 48 V in 528 lb (240 kg)
• 8V: T-875 170 Ah, 63 lb (29 kg), so a set of six is 170 Ah @ 48 V in 378 lb (174 kg)
• 12V: T-1275 150 Ah, 85 lb (39 kg), so a set of four is 150 Ah @ 48 V in 340 lb (156 kg)
Similar boxes, split into different numbers of cells to change the size of the total 48V set.

So, you decide on your battery chemistry and construction, your total capacity, and how big a box you want to lift... and you have your battery ("module" in EV terms) voltage and capacity.

If you're happy with lead-acid, and only need two-thirds of the capacity of the current six X 8V configuration, you can use four X 12V (of something like the size above).
If you want more capacity, you can use really big and really hard to manage 12 volt batteries;
e.g. J185P-AC, 205 Ah, 114 lb (52 kg) each, or 205 Ah @ 48 V in 456 lb (208 kg)

#### brian_

· Registered
Joined
·
8,629 Posts
The vendors design most 12V to not last nearly as long as the 6V units, often **half** the rated cycles for a given cycling depth.
Stereotypes don't help; facts do. The 12 volt battery which I used as an example (Trojan's T-1275) is rated for the same cycle life (1,200 cycles @ 50% DOD) as the 6 volt models in the same product line (Signature Line). That makes sense, since it is built the same way.

Pricing is another matter - that has nothing to battery technology and much to do with supply and demand.

#### brian_

· Registered
Joined
·
8,629 Posts
Problem isn't just weight.
Weight isn't a problem with the voltage selection, either. The values which I quoted clearly show that the total capacity is proportional to the total weight - regardless of the voltage per battery (which means the number of cells per battery box) - within the same product line (so comparable construction).

1 - 3 of 14 Posts