Disappointing battery life/ run time

[Derek Attree]

Hi Guys
I took my Stug III to Wings and Wheels last week and was disappointed
with the run time I got from the tank on what seemed to be fully charged batteries.
I only ran for about 35 Mins maximum and the batteries went to 22 volts and the tank kept stopping.(Needed reset on the power board... Fail safe mode ?)
The batteries are 24 amp hour and I charge them every 2 - 3 weeks to keep them topped up.
The tank has only had about 3 hours running since it was finished.
I also gave them an over night charge before going to the show.
I recharged them when I got home and they measured 26 volts...I am charging as a pair
using an Accumate charger and the batteries are about 2 years old.

Any Ideas as I see Robin and John getting much longer run times than that with bigger heavier tanks than the Stug...
I have no sound or smoke either.

Thanks

Derek

[Adrian Harris]

Derek, I would measure the voltage on each battery, rather than as a pair, to see if one of them is failing.

I'm a convert to the idea of charging the batteries individually, as this means they each get the voltage/current they need, rather that the average over the two batteries.

I would guess I got about an hour of running at TankFest, on each set of batteries, and that's with an oil based smoker (2 amps) and the sound running.

Adrian.

[chris fry]

hello Derek,
good way to test those batteries is to jack the tank up off its tracks and run both the tracks flat out and using a voltage meter test each battery, need 3 hands really but this will indicate if you have a battery that is dropping under 12volts under a load, you may have a loose terminal or loose wire on one of the batteries so worth checking these terminals, puzzled that the tank stopped on 22volts, did the indicator on the power supply module show an amber light or flashing red as the red indicates voltage is at 14-18volts but will still run just!! (back to your car) even amber is 18v-23v and that's indicating partially discharge of the batteries, Adrian is right about charging one at a time but this isn't always easy with the way the batteries are linked together, going on what other builders have used and there feedback the accumates are not that good chargers, they do tend to pump most of the charge in to the highest voltage battery so not charging the lower voltage battery if there is one.
hope this of some help.
Chris.

[Derek Attree]

Hi Adrian and Chris
Thanks for the input.
So I did a bit of detective work over the weekend and I took the 2 batteries
out of the Stug and measured them after a full charge and a short run with the
tank jacked off the ground so the tracks were free to run.
During this run the tracks slowed after about 5 mins running at full speed,
this is the point I removed the batteries and disconnected them form each other .
One measured 12.13 volts and the other 12.6 volts.
Tonight I will charge them one at a time and then repeat the run test to see what happens...By the way the batteries are 22Ah not 24Ah as I put in the first post.


Derek

[Adrian Harris]

Derek, you probably need to measure the battery voltage whilst the tracks are running, as a bad battery cell can "recover" to a passable looking voltage once any load is removed.

Adrian.

[Derek Attree]

Hi Adrian
Thanks
Will do

Derek

[chris fry]

hello Derek,
when the tracks started to slow down after 5 mins running did you notice what colour the bulb was on the power supply module, I would have thought if the tracks had started to slow down the bulb indicator would be showing flashing red, also did you check all the terminals on the batteries??, if the terminals/wires were loose they would generate some heat so just put your finger on one of the terminals when your running the tracks flat out to see if there is any heat build up.
keep us informed,
Chris.

[Derek Attree]

Hi Chris
I did not see the light change colour as the electronics is buried and I can only just
get to the on off button.
The terminals were very tight I needed a spanner to undo them and there was no movement
in the contacts before.
I tried them to make sure nothing was loose...I will try a run tonight and see what happens...

Thanks again for your input.

Derek

[Derek Attree]

Hi Guys
Well after charging both batteries as singles I reconnected them
into the tank and set the tank tracks running with the tank on blocks and then measured each battery whilst under load and saw the dramatic drop off indicating a dead battery.

One fell to 11.3 volts but stayed there the other dropped and kept dropping and fell
to 7.9 volts in about 14 minutes.

Just out of interest the colour change LED on the power board stayed green for about 4 minutes and then went to amber and then to flashing red at about 12 minutes.

After removing them from the tank the one that was 11.3 volts went back to 12.3 volts and the 7.9 volt one got back to about 10.4 volts...(Dead cell)

So it looks like the cold winter took its toll on these batteries despite me regularly charging them.

Need to buy 2 new ones and find a warm place for them over winter...

Thanks again to all that gave advice.

Derek

[chris fry]

hello Derek,
glad you have got to the root of the problem, hardware express that armortek recommend are worth a try, 10% discount as well and they are very quick to dispatch, the 24ah is the one to go for if you are going to run a smoker, but just check the sizes as they are big batteries and don't know if 2 will fit inside the stug,
on a quick note gel batteries are not that susceptible to cold conditions, so they will be fine in the workshop etc over the winter, its better to discount the batteries if they are stood idle for long periods and charging them once a month keeps them active.
hope this helps,
chris.