Battery drain

We are using the 7.2 v 3000 mAh NiMh batteries. They are brand new this school year and I have been disappointed with their performance. We will put them on charge and the battery charger will show when they are fully charged. Students will use them for simple motor movements and within five minutes of switching batteries, you can see that the battery is not fully charged. I know the batteries will drain with constant usage, but this drain is way too fast for the simple tasks we are trying to perform. Any thoughts?
Thank you.

Do you charge them on fast or safe? If you charge them on fast that could be the problem. If you have an lcd, use it to display the voltage and LMK what it reads.

Make sure that after charging the cable is all the way in. Sometimes the connection is loose, and won’t charge, because it thinks a battery isn’t attached.

LCD screen with battery voltage is a game changer.

If this is not for competition, get some lipo batteries. You can get much better performance for a fraction of the price. We always use lipos for practice and testing, and only use the vex ones at competitions and when doing final tests of autonomous (where a slight difference in battery performance might make a difference).

Thanks. We do charge them on safe mode only. I will double check on the connections, too.

Can you recommend a brand and supplier? Do you also use a different charger just for the LiPo?

The VEX chargers don’t support LiPo, so you would definitely need a different charger.

Hobbyking is by far the best place to get batteries and chargers. I had some really cheap lipo chargers which were no good, I just got this one that was recommended by another team, but haven’t used it myself yet as it just arrived: It can also be set to charge and discharge almost any battery type.

I would recommend avoided shipping from Hobbyking’s Asia location, because the US warehouse is only a tiny bit more expensive and much faster.

I’ve also thought about getting these ones that seem to be completely identical to the VEX NiMhs but cheaper: That way we can test on batteries that behave the same as competition ones without wearing out the actual competition ones.

Ours do that too. We just figured that it was because this year is such a demanding game

This year is nothing compared to last year (Nothing But Net)…

Nah, this year our Cortex and PE go straight to red while last year stayed green for at least 45 seconds.

This is because you can be using all the ports in your Cortex all at the same time (Backing up, lifting, and opening claw). The Cortex wasn’t made to handle that much. In NBN, there weren’t too many situations in which you would use all the ports at the same time.