This is a small improvement over shanemadden's original mod. It adds some additional startup settings for better convenience and balance (or unbalance!).

You can now set the recipe cost and the amount of power the wagon can hold and transmit. From 5MJ up to 5TJ, 300kW to 300GW.
I have also changed the recipe to be a bit more suitable (and costly), but added the option to opt out of that.

The new recipe requires 2.5 advanced circuits and 5 batteries per multiple, rounded down, instead of 0.5 electronic circuits and 1 accumulator, and the raw components of a cargo wagon instead of the ready-made wagon. The cost setting multiplies the battery and circuit costs, and this also works for the old recipe. The power setting specifies how many accumulators worth of capacity and throughput the wagon will have.

Default for both settings is now 4, so the accumulator wagon doesn't outcompete normal accumulators in terms of cost or space, and this makes their usefulness quite limited. Keeping both values the same and enabling the new recipe keeps things reasonably balanced, even if you decide to crank it up a bit. The original mod was at 100/10, but you can go much higher now if you like.

Link to original mod and its author:
https://mods.factorio.com/mod/accumulator-wagon
https://mods.factorio.com/user/shanemadden