Hey All...here is probably a very "stupid" question for ya...

If I have a 5000 mah LiPo, and a 5000 mah NiMh....would the run time of the LiPo be more?

Yes, the lipo is certainly capable of running longer, it’s more efficient, a lot less energy lost going into heat. Depends on current draw, but 20-30% improvement is not uncommon.

But also be aware that unlike nimh you shouldn’t run a lipo all the way down for good battery life.

When I converted my 18th scales, I was getting 10-12min on gp1100s (yeah, it was a while ago, lol) and run time jumped to 20-22min with the same mah lipo. Now lipos have gotten better, I can put a lot more mah in the same space with lipo and run times are 30-35min.

ALl the heat a NiMh makes when its being discharged is energy wasted and prob most of teh reason lipo gives better run times. A proper setup shouldn't be making lipo anything more than just warm when its run.

What you meant by "All the way down" is it no longer responds? are there any way maybe that the lipo will stop sending current if it reaches a specific mimimum volt left? I usually run it till it's not moving my car anymore.

Nowadays it's somehow lesser LHS will stock NiMH batteries. It will gradually be replaced by LiPo. If you get one of the match pack. Another concern is does it hold up full capacity full charge. Since it has been lying there years in store.

A Lipo should NEVER be discharged below 3.0V per cell. Many newer ESCs have a cutoff built in, and you can purchase separate cutoffs for ESCs that do not come equipped. Running without a cutoff until a lipo stops or even close to it would really shorten the life of the pack, if not ruin it the first time. Most Lipo chargers will not even charge the pack if it shows less than minimum voltage fr safety reasons.

LiPos do not like to be "undervolted."

A battery is a voltage AND a current source, so the amount of capacity left is proportional to its voltage as the charge is being emptied out of it...

If you're going to run LiPos, make sure your ESC has a cut-off feature and that you set it correctly, depending on what configuration the battery (2S?, 3S? 4S?).

If it doesn't have one, you can get some piggy-back systems that will do an alarm or cut-off for you... Again, make sure you set it correctly with a bit of margin...