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NOTE:  A 107 db version is an option (for industrial use).

The On-Board Chargers are designed to automatically charge lead-acid batteries.
The US version chargers (110v, 60 hertz) plug into any grounded outlet and are UL approved.  All versions are "isolated and grounded," have a "soft-start,"  and are SCR regulated to prevent excessive or runaway current draw.

24-volt:  The 24 volt charger has a switch for choosing between sealed and flooded charging algorithms.

36-volt:  The 36 volt charger (at this time) can only be used for charging flooded lead-acid batteries.

An export version is available:
The 24 volt export version can be used with either 50 or 60 hertz, and from 90-125/180-250 volts (switch-able ranges).  (A female receptacle on the charger is the same standard as used on all computers, so that cords used in any country can be purchased locally.)

Battery Selection: 
Suggested batteries include 8 volt deep cycle "golf cart" batteries, or 12 volt deep cycle batteries (24, 27, 29, 30, or 31 series). 

We feel the optimal battery configuration for the 24 volt Gorilla is three 8-volt golf cart batteries.  These batteries provide the best compromise of performance, range, life, and economy (see range analysis below), and provide three to five years of use (with proper maintenance).  
(These batteries have been used in Club Car golf carts for almost ten years.)

Battery Capacity Chart and Range Analysis

Type	Minutes @ 25 amps	Minutes @ 75 amps	Weight (pounds)
Trojan T-875, 8 volt  standard on e-ATV 24	300	75	63 x 3 batteries = 189
Trojan 27 series, 27TMH, 12 volt standard on e-ATV 36	200	52	60 x 3 batteries = 180
Special order OPTIONS:
Trojan T-890, 8 volt	360	90	69 x 3 batteries
Trojan 31 series, 31XHS or SCS225, 12 volt	225	57	67 x 2 batteries
Trojan T1275, 12 volt	290	102(@56 amps)	82 x 2 batteries

The 24-volt Gorilla draws about 40 amps* from the batteries (at top speed, and on level ground).  Looking at the data for the T-875 batteries; you could average the 300 and 75 minute ratings (at 25 and 75 amps respectively) to get 187.5 minutes  at 50 amps.  (This is a conservative approach (we know about Peukert's Curve)).
Divide the 187 minutes by 60 minutes (1 hour), and see that the Gorilla should run for over 3 hours at top speed (3 hours X 15 Mph =  45 miles).  When we consider terrain, hills, turns, stop and go driving, load, etc; the Gorilla should still easily get a 25 to 35 mile range with the 8-volt batteries.  This has been experimentally confirmed with field testing.

You can use this same analysis to see what to expect from other batteries.
*  The 36-volt version pulls about 50 amps at top speed.  Hence, less range,  ~20 to 25 miles of flat cruising.

Other Battery Factors:
Sealed vs. Flooded:  
Sealed batteries require no periodic maintenance, but will cost more initially, have less range, and a shorter life span (in years).
We challenge sealed battery manufacturers to prove us wrong.

Flooded batteries will need to be "topped-off" with distilled water every one to three months depending on outside temperature, relative humidity (more frequent watering is required in desert  climates), depth of discharge, frequency of use, and charger power (Gorilla's "smart" charger is designed to minimize water usage).

8-volt deep cycle ~ versus ~ 12-volt "quasi-deep cycle" batteries:
The 8-volt battery is a true deep cycle battery (just like 6-volt golf and industrial vehicle batteries).  You can expect the 8-volt batteries to have a life of between 3 and 6 years (depending on harshness of use, depth of discharge, frequency of use, and proper maintenance).

We call the 12 volt deep cycle batteries "quasi" because they are a compromise between a deep cycle battery and a starter battery (there are a few exceptions and you'll pay for them).   You can expect a life of from as little as one year, and up to three or four years. 
Life of the 12 volt batteries depends on the factors listed above, and the initial quality of the battery. 
Deep cycle batteries are more expensive to manufacture.  Their plates should be thicker than starter batteries, and other costly elements (such as antimony) are added to prolong their life.  Some battery manufacturers don't spend the extra money.

The Trojan 12-volt deep cycle batteries listed above are a good compromise for people who don't need the range of the 8-volt batteries, but want more speed.

*Note:  Only two (of most brands) of the group 31 batteries will fit in the Gorilla.  Also, only two of the T1275 batteries will fit.
These options are limited to the 24 volt vehicles.