battery discharge rate question - batteryholics united

[lurkingknight]

the discharge rates on nimh are generally under 10C... closer to 5C , some as low as 3C I believe... so it's some pretty lowass amperage to power a motor trying to pull over a stiff spring and short gears.

[ThunderCactus]

Originally Posted by Jimski

the answer I was looking for was given on post #7

Yeah but that's a lipo, not a NiMH lol
It's also on a PTW that can handle it, not a stock AEG


You can absolutely run an AEG off a 10.8v mini NiMH, I wouldn't recommend it, but it WILL be safer than the 10.8v 4000mah battery.

With the mini, obviously you'll just have really poor battery life and eventually strip the piston and possibly worse. It'll definitely run the gun though, you're making up for lack of amperage with higher voltage.

With the large, it's going to be a close equivalent to an 11.1v lipo

The bigger pack will blend for sure.

If you're wiring cells into a different pack, you'll be altering the drain on the pack. It'll just lose life every time you charge it.

[Kos-Mos]

Don't add cells to an existing pack.
It will die in a fire very soon.

The only exeption is brand new pack and cell, from the same company and batch.
Or two same brand/type/ratin packs, bought at the same time, and used together or the same number of cycles that you use to make a larger pack.

I would run 9.6v 4000mAh if you have space for it.
It will give you a very nice trigger response, on par with 7.4v LiPo.

[Jimski]

You can absolutely run an AEG off a 10.8v mini NiMH, I wouldn't recommend it, but it WILL be safer than the 10.8v 4000mah battery.

With the mini, obviously you'll just have really poor battery life and eventually strip the piston and possibly worse. It'll definitely run the gun though, you're making up for lack of amperage with higher voltage.

exactly!
we'll see what happens.I'm kinda impatient.

[Jimski]

Originally Posted by Kos-Mos

Don't add cells to an existing pack.
It will die in a fire very soon.

The only exeption is brand new pack and cell, from the same company and batch.
Or two same brand/type/ratin packs, bought at the same time, and used together or the same number of cycles that you use to make a larger pack.

I would run 9.6v 4000mAh if you have space for it.
It will give you a very nice trigger response, on par with 7.4v LiPo.

that's the thing, I only have space for almost nothing.( and my recent vow of cheapness forbids me buying any type of battery container, external won't do and I want to keep the whole thing light, so big capacities are not considered.)

I definitely expect some heating up.I want to see if it is that bad.

[Jimski]

The bigger pack will blend for sure.

will it blend?

**ominous music**

[ThunderCactus]

Originally Posted by Kos-Mos

Don't add cells to an existing pack.
It will die in a fire very soon.

I would run 9.6v 4000mAh if you have space for it.
It will give you a very nice trigger response, on par with 7.4v LiPo.

as long as they're at the same charge, it should last a while
a "pro battery shop" in winnipeg fucked me by not balancing the cell they added to my pack back when I ran a custom 9.6 mini for a PEQ. Dicks.

And it's somewhat misleading, a 7.4 generally has slightly less ROF than a 9.6 mini, but that's not always true either.
Highly dependent on your setup and motor. Basically, the more the NiMH pack starves the motor of amperage, the better the 7.4v will perform.

Generally on a stock gun, a 9.6 mini will be just a bit better than a 7.4 lipo.
Let's say the 9.6 mini nets you 950rpm, the 7.4 lipo will be around 850rpm
The large cell NiMH will provide a lot more amperage, usually all the amperage the motor needs, so let's say the 9.6 large nets you 1200rpm, and will always be faster than a 7.4v lipo. Tradeoff being you need a mosfet to prevent the 9.6 from melting your trigger, and they're much more expensive.

Back to the mini packs, if you throw in high speed gears and a nice torque motor, maybe the 9.6 NiMH mini won't even be able to turn the gun over, whereas the 7.4 lipo might do 1200rpm

[Kos-Mos]

Originally Posted by ThunderCactus

as long as they're at the same charge, it should last a while
a "pro battery shop" in winnipeg fucked me by not balancing the cell they added to my pack back when I ran a custom 9.6 mini for a PEQ. Dicks.

And it's somewhat misleading, a 7.4 generally has slightly less ROF than a 9.6 mini, but that's not always true either.
Highly dependent on your setup and motor. Basically, the more the NiMH pack starves the motor of amperage, the better the 7.4v will perform.

Generally on a stock gun, a 9.6 mini will be just a bit better than a 7.4 lipo.
Let's say the 9.6 mini nets you 950rpm, the 7.4 lipo will be around 850rpm
The large cell NiMH will provide a lot more amperage, usually all the amperage the motor needs, so let's say the 9.6 large nets you 1200rpm, and will always be faster than a 7.4v lipo. Tradeoff being you need a mosfet to prevent the 9.6 from melting your trigger, and they're much more expensive.

Back to the mini packs, if you throw in high speed gears and a nice torque motor, maybe the 9.6 NiMH mini won't even be able to turn the gun over, whereas the 7.4 lipo might do 1200rpm

Now, they added cells that had a different life cycle. Internal resistance was probably lower than your old cells.
The extra voltage had to go though all the old cells, and cause more heat. That plus the probably partially dried electrolytic fluid in the older cells caused more heat.

Either one or more of the old cells completely died prematurely (or inverted), or one of the new cell died REALLY fast, possibly even blowing-up.

You CANNOT add cells in a pack unless they have the same age and wear life. Period.

Jim, let me know if you want a dirt cheap FET to try stuff. It's dumb, not computerized, but can take 40V and 240A.

[ThunderCactus]

They had built the pack to begin with, so all the batteries were of the same manufacturer and batch, they straight up added a ~70% storage charged cell to a 100% fully charged pack.
It only had 2/3 the life of my completely assembled 9.6 pack and since there's no balancing option on the packs, it never charged that one cell so the voltage would drop off fast (since you're essentially losing 1.2v prematurely). Eventually I just threw it out. Probably would have exploded on me eventually. I never had the cell go to 0v though because I'd change it out as soon as the voltage dropped, but I'd get ~400mah out of it before the drop compared to ~900mah on the properly built pack.
So bottom line, the dude modding my pack was a dick.

[targetGspot]

you're going to spend more money this way. they warn about mixing old and new batteries in toys, remotes, etc. the same applies here. the old and new batteries will hold a slightly different charge, and discharge at a slightly different rate. something will give and you will be out a battery pack anyway. I'm slowly switching to lipos as my old batteries die. 1 decent charger, $45. Lipos are actually cheaper and smaller so easier to find room in your guns. 7.4's in "lesser" guns and 11.1 in good guns. I've not run into any issues that way. Also lipo's work better in colder weather and for me they've been lasting longer. You're only going to save $$ if you think about it first.

[Jimski]

but the thing is they're not exactly old, they come from a pack I got just two month ago for some RC.They stand a good chance of being exactly the right thing.
However I'll try to have all the cells +battery as balanced as possible before running the gun.

[targetGspot]

I still wouldn't bother. likely going to lose a battery pack. Better off moving to lipo's, a little $ now will save you in the long run and provide better performance at the same time. Keep the old battery and use it as needed. I've found lipo's have "saved" me from needing to buy a peq or switch battery location by having to buy a crane stock and change the wiring.

[ThunderCactus]

Plus, $9 high quality batteries. How can you say no to that? lol

[Sloth]

It'll blend like hot dogs in a Magic Bullet