WIRING FOR GAINING RANGE
If I wanted to gain range on my scooter, could I drop one or two more 12 v SLA batts (35AH) onto my scooter? Is it possible to wire the batteries in a parallel & series config to keep the system supplying 60v primary and gain range? I'd like to be able to drop a couple 12v batts on top of the 5 x 12v 35AH = 60v in the trunk to add to the string, maybe creating a range of 40 miles for a longer trip occasionally. Any ideas?
First, I redirected this to a more appropriate forum.
Second, yes you can wire batteries in parallel/serial combinations. But I think the geometry you're suggesting isn't quite right.
You described putting two batteries (a.k.a. "a couple") in parallel with a 5 battery string. Uh...? The voltages don't add up. You could add five batteries to a five battery string and it would work well. But to add two batteries to a five battery string creates a misbalanced pack.
Perhaps consider putting 5 additional batteries on a small trailer. During shorter trips, you can quickly and easily disconnect the trailer so you're not hauling around the extra range battery weight, but its there when you want it. Just an idea...
Scottmagic, to wire two or more batteries in series, they all need to be the same capacity to get any benefit, because the capacity will be that of the lowest capacity battery in the string. However, the voltage can be different.
To wire two or more batteries in parallel, they must be the same voltage. However, the capacity can be different.
This means unless you either step up the voltage of the added battery(s) somehow, or go to a higher system voltage, you will need as many batteries as you already have to increase the range. That is, unless you take the existing batteries out, and modify the bike so it can take larger batteries.
A higher system voltage might actually be a good option, but this would be somewhat expensive requiring changing the controller, and the charger or adding chargers (if doing bank charging).
You could add one or two 35 ah batteries in series with the existing string to go to a 72 or 84v system, and than set the throttle output to the controller so the motor voltage doesn't go above 60v (having the same top speed as before). This also allows you the option to increase the top speed, but that may cause motor heating issues, and reduce or eliminate any potential gain in range.
A more conventional option is to use smaller batteries. You might be able to fit five 12ah 12v, or maybe even 20ah 12v batteries. These can be wired in series for a 60v string which can be wired in parallel with the existing 60v string.
To get a good rough calculation of the extra range, just take the added battery capacity divided by the existing capacity, and multiply that by the existing range. If going to a higher voltage but with the same 35ah capacity, than take the added voltage divided by the stock voltage times the existing range.
Thanks everyone for the explanation. Much appreciated.