RE: Battery questions [TANKS]

["Steve Tyng" <STyng-at-ACPTrust.com>]

Jeremy wrote:

> Just wondering how changing/charging batteries work on the 
> battlefield.  I know that batteries can be moved around on 
> the battlefield by supply vehicles, but is there enough time 
> to charge batteries during the day or do I need enough 
> batteries to make it through the entire day?

It takes longer than the couple of hours between battles to charge a
battery.  My 24V 6amp charger takes overnight to charge one set of 18AH
batteries.  Most battlers bring enough batteries for two one hour
battles.  In the Cromwell's case, I will usually use two sets 18AH
batteries for a days battling (four batteries total).  I bring an extra
third set as a backup.  The T34 ran at 12V and carried only one 18AH
battery and could go through three batteries in one hour of battling.

> It would seem to me that I'd need quite a stack of batteries
> if there isn't a chance to charge any up.

The number of batteries your tank will need depends on many factors
(motors, voltage, space, driving style).  Also, It appears that PWM
motor controllers are more battery efficient than on/off controllers and
will give longer running times.

> Also, is there normally AC power available near the 
> battlefield?  Should I get a charger that can run on DC and 
> use my car to charge the tanks batteries?

Usually AC is not available at the battle sites.  Get a smart charger
that will charge and then maintain your batteries.  Avoid cheap
automotive battery chargers because it is easy to leave these on for to
long and you will end up overcharging your batteries and damaging them.

> One last question:  I was cruising ebay looking at gell cells 
> and there are some people selling giant (~100AH) batteries 
> made to go in UPS's.  Is it better to get two of these (I'm 
> going to run 24v) and try to charge them in the tank between 
> battles and run the whole day that way, or get several sets 
> of smaller batteries and have to change them out?

Most battlers get by with 26 to 36 amp hour capacity for a one hour
battle.  100AH of battery in your vehicle (if it could fit) would
probably be overkill.

> Has anyone 
> had problems with the gell cells dieing from continually 
> charging them up and then draining them down to almost 
> nothing?

Don't drain them too nothing.  I added an easily visible voltage meter
to the Cromwell to avoid such a situation.

> I thought that doing that was very bad for gell 
> cells/lead acid batteries and that deep cycle batteries would 
> work better for such an application.

Yes, draining lead acid batteries below a certain voltage level (11.6
volts I think) will begin to damage them.  Deep cycle batteries are what
you want.  Avoid automotive and motorcycle starter batteries.  Batteries
marketed for alarm and UPS systems are deep cycle.


Steve Tyng