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In batteries, does stored energy vary with battery voltage?

May. 13, 2024

In batteries, does stored energy vary with battery voltage?

Yes.
You could make the 40 V, 2 AHr battery from two 20 V, 2 AHr ones, or the 60 V from 3 of them, (in series.)

The 20 V 2 AHr battery is supplying (1200W / 20V) = 6A , so will run for (2AHr / 6A) = 1/3 Hr
The 40 V 2 AHr battery is supplying (1200W / 40V) = 3A , so will run for (2AHr / 3A) = 2/3 Hr
The 60 V 2 AHr battery is supplying (1200W / 60V) = 2A , so will run for (2AHr / 2A) = 1 Hr

In theory! In practice I don't know how the nominal capacity relates to actual capacity in use.
Presumably the 1200W rating is a maximum and the actual power usage will vary with the task, so I'd think you'd get more hours actual use.

Edit: I missed SC's post. Agree with his comments.
But other thoughts it provokes about the relative merits of different battery packs:

When rechargeables are in series, they are as durable as the weakest link. When one fails (or heads in that direction), the others tend to get overcharged and deteriorate faster.
Since Li cells came along, more sophisticated equalising chargers have become more common. I expect, as SC says, that the higher voltage machines, being more the expensive ones, are likely to have better charging circuits. Even so I wonder how easy it is to keep 18 cells balanced, especially if the user regularly fast charges.
When you do have to replace them, the step cost is greater.

On the plus side, for the same useage the higher voltage battery is supplying lower current and generally that is less stressful (damaging) to the battery. So all the cells should have an easier and longer life.

As CS implies, it would be nice to be able to comment on this from experience rather than theory!