Hello,

I bought a multimeter and have been testing my batteries while running my Tamiya Panther. And I have answers!

A fully charged battery 7.2v rated battery comes out of the charger with about 8.5v in it, this is regardless of battery type be it NiCd, NiMh or LiPo.

After driving about in the tank the voltage drops to the stated 7.2v average fairly quickly and then flatlines at 7.2v for a long time (they are of course designed to do this and this is why they are rated at 7.2v)

When the tank DMD goes into save mode and stops, the battery on coming out of the tank still has a charge of between 6 and 7 volts. I believe the DMD shut down threshold is about 6 to 6.5 volts as even a spent battery with 7 volts still in it dropped to about 6 volts on the test bench under slight load. So one can imagine that in the tank when one runs over steep or difficult terrain the motor draws more power, the voltage drops below 6v - 6.5v under the strain, and the DMD shuts down.

I have repeated this experiment many times as I did not believe it at first. It seems wrong that the battery should still have so much charge in it on DMD failure. But the result was repeated over and over again with each sort of battery.

So it seems that the DMD is designed to shutdown at the end of the 7.2v flatline on the performance curve leaving your batteries still with lot of charge left in them.

One should not deplete LiPos below about 3v. So because the DMD shuts down at about 6v there is no danger of damaging your LiPos. (in theory but what happened to the batteries in Planedevs Pershing? Older DMD? different programming?)

We have also learnt that having run your LiPos to DMD failure your should not leave them connected in your tank for days afterwards as they continue to deplete and then bloat and damage themselves. Best practice is to remove them from the tank and charge them up again as soon as possible.

I would imagine that once a battery has reached the end of the 7.2v flatline on its performance curve the voltage drops away very quickly.

Another point that applies to all battery types, except LiPos and LiOns, is that because the shutdown threshold of the DMD is relatively high one should discharge the batteries fully every now and then before recharging them otherwise they may develop a memory (NiMh and NiCd) and thus shorter running times.

So now I am going to use my LiPos more and feel relatively safe doing so, though after the first shutdown I no longer try to limp home on restarts rather than picking the tank up and carrying it back for a battery change out.

If your LiPos do leak, bloat or explode, despite the above, please write in with a bit of background and we can work out what went wrong. Maybe not all DMDs are the same.

I can say for my part that the newer DMDs that came with the Panther perform as listed above. I do have 2 other tanks with Pershing DMDs in that were not subject to my testing, I will carry out some testing on them and report back.

Cheers

Alan.