battery discharge rate question - batteryholics united
 

hello all, this is a question for the somewhat experienced battery enthusiasts...

considering a 4000 mAh / 10.8 V battery has somewhat too much kick for an aeg and will break something (say stock parts)
is there a chance that a 1000mAh battery with the same voltage might be less dangerous, considering it also probably has a much lower discharge rate ?

thanks.

If the physics still apply, I don't think changing the mAh will change the discharge rate. A 4000mAh and a 1000 mAh battery still do the same amount of work(Voltage is the same) the mAh is the rating for charge, or battery capacity if I'm not mistaken. So a 4000 would just last longer in the same gun. At least that's what I assumed

Only in NiMH cells
Your amperage delivered is based on the physical contact inside the cell, so the smaller the volume (sub-c cell versus C cell), the less amperage provided, thus the less torque supplied to the motor and the less ROF

Strictly in technical talk, a 4000mah battery has the same performance as a 1000mah battery, but a 1000mah NiMH is always a mini pack and a 4000mah NiMH is always a large pack, so the difference is in amperage supplied

Why are you looking at a 10.8v large battery? What's your ultimate goal here?

I want crazy trigger response with zero dollars and just two extra cells.
I have designated one of my aegs as a guinea pig victim.
Some pistons will not survive.
You can't stop me.

(I won't use lipo, it goes against my vow of cheapness)

But Lipos ARE cheap :P

More seriously...

A small lipo around 20-25C rating usally do the job very well. You can find them in rc stores for around 15$.

If you stay in Ni-MH world it is important to know the discharge rate of your battery wich is harder to know most of the times. If you have a 1A 10.4v battery with a 5C rating it is still going to be worse than a 1A battery 9.6v with 10C rating.

In all cases switching connectors to deans (3$) will help a lot also as tamyia are very bad connectors overall and they are not design to handle discharge of more than ~10A.

vow of cheapness makes you spend $60+ on a NiMH but not $39 on an 11.1v 20C 4900mah battery?
The 11.1v 1200mah 25C batts I use on my PTW are $9 each

Also, without a mosfet you are guaranteed to destroy your trigger contacts.

no, I spent nothing, I'm adding two cells I had kicking around to a battery that came with the gun.Don't misunderstimatify me.

so it works

ok I need to find a free mosfet, or maybe an old piece of dry sausage will do

A 1000mah lipo will have the same performance as a 6000mah lipo assuming the smaller pack provides 100% of the amperage required by the motor
A mini NiMH pack never provides 100% of the amperage required by the motor, so you'll have around the same performance as a 9.6v large battery.

I'm curious to know, you don't want to buy a new battery, but you're willing to waste $100 of internals by running high voltage?

you know as well as me that I will waste at the worst a piston, but that was my question here: will it blend ?

I don't want to buy the charger.
:D

Worst case you break the back end of your piston off, it jams your gears and the most likely thing to go is usually the spur gear. And at some point you'll melt the trigger.
Half of the gear train failures I've seen are from chunks of piston jamming them up and breaking teeth from the shock of stopping so fast. The other half is from gears just being really shitty lol

you're so dramatic! are you a gun doctor by chance? ah yes I see lol

this weekend I will tell you what happened.
will
it
blend?

You are about to put 2 more subc cells to your pack.
Assuming it is 2 cheap ass subc cell laying around for a while.
The internal resistance of those individual cell will probably be higher that the one of a dog shit and will be the limiting pack performance. That doesn't take in account that the cells and the pack will not have the same balance between cells and the thermal shock your gonna give them while soldering with your probably vow of cheapness soldering iron.

In other words when its gonna be time to charge your pack, please do yourself a favor and don't let your pack chaging without surveillance and monitor the temp. If you can't hold it in your hand, stop charging, dispose safely and environmentaly and do yourself a favor to buy a cheap lipo and lipo charger (under 50$ for both) that gonna be a lot performance wise while still being in the vow of cheapness.

the cell types are the same and they are decent quality packs.

You guys are so dramatic it's funny.I have soldered many battery packs and gun-doctored the shit out of all my guns, I know all that crap.
I'm amused at the amount of serious-consequences bullshit you are spreading, but I totally expected that here ;)

the answer I was looking for was given on post #7
I might add a few components to deal with the current.Right now I'm fighting with the rear-wiring for the extra cells.Yes they are in a separate pack :D ( I hope I'm shocking you at least a little bit)

will
it
blend?

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.

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.

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.

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

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.

:) will it blend?

**ominous music**

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.

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.

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.

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.

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.

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

It'll blend like hot dogs in a Magic Bullet :cool: