Nimh or Lithium ion powered

[jojobeans]

Just to continue the discussion, I'm curious to know if 5000mAh NiXX packs are actually 5000mAh. (Don't worry, I ordered one to test!) I say this because I know from rebuilding old cordless drill packs that the only Sub C sized cells (Same size cells that are used in stick packs you can generally find that claim to be 5000mAh are from China and are not 5000mAh. More like 3600-3800mAh. Now, granted, my data is a bit old because it's been about 10 years since the last time I messed with them, but I doubt anything has changed. Just in case it did, that's why I'm going to test a stick pack to see once I get it. The stick packs that you see labeled 3XXX are most likely really that mAh rating. 3800mAh is probably about as much as I've seen a legit Sub C put out. Also, I'm pretty sure this has not changed because if you look up batteries or packs from Tenergy (A Chinese battery company that actually makes good batteries and seems to state real specs instead of overblown specs) I can't find a single one rated over 3800mAh. That being said they do have single Sub C cells you can buy that do claim to be 5000mAh. I find that doubtful but if someone managed to make one it was probably them.

Great, now I wanna buy one of there 5000mAh Sub C cells to test lol

NiMh packs are definitely limited on capacity just due to chemistry. I’d wager to bet 3000-4000 is probably the maximum capacity per pack. Running them in parallel is likely the only way to get more capacity, but at that point I feel weight would have a larger impact of run time than what the extra capacity would supply.

I’d also wager to bet a brushed motor in a high traction/high stall environment like a crawler puts more load on batteries than a moderately geared quality brushless system in something like a basher that’s just ripping around a baseball diamond. I would think a NiMh in a crawler even though it’s “slow” is probably the worst thing to be using a NiMh pack in.

Definitely looking forward to your findings. If there’s a way to test load while running I think brushed vs brushless load testing would be some neat data. Eagle tree data logger maybe? Do they still make those? I know from experience brushed models suck the juice out of a LiPo much faster than mild, much faster brushless systems. So that leads me to believe there’s far more amperage draw from a bushed setup compared to brushless… kind of deconstructing the NiMh ONLY work for brushed cars and will not work with brushless argument.

 

[Greywolf74]

NiMh packs are definitely limited on capacity just due to chemistry. I’d wager to bet 3000-4000 is probably the maximum capacity per pack. Running them in parallel is likely the only way to get more capacity, but at that point I feel weight would have a larger impact of run time than what the extra capacity would supply.

Yeah, parallel would definitely be too bulky and heavy.

I’d also wager to bet a brushed motor in a high traction/high stall environment like a crawler puts more load on batteries than a moderately geared quality brushless system in something like a basher that’s just ripping around a baseball diamond. I would think a NiMh in a crawler even though it’s “slow” is probably the worst thing to be using a NiMh pack in.

I'm fairly certain that it's the opposite of that, but I have no proof, as I'm not much of a crawler guy. I'd be curious of others opinions on this particular issue.

Definitely looking forward to your findings. If there’s a way to test load while running I think brushed vs brushless load testing would be some neat data. Eagle tree data logger maybe? Do they still make those?

Unfortunately, Eagle Tree went out of business toward the end of 2020 due to the covid BS. You can still get Hyperions eMeter II even though it was discontinued in approx 2023.

 

[Greywolf74]

NiMh packs are definitely limited on capacity just due to chemistry. I’d wager to bet 3000-4000 is probably the maximum capacity per pack. Running them in parallel is likely the only way to get more capacity, but at that point I feel weight would have a larger impact of run time than what the extra capacity would supply.

I’d also wager to bet a brushed motor in a high traction/high stall environment like a crawler puts more load on batteries than a moderately geared quality brushless system in something like a basher that’s just ripping around a baseball diamond. I would think a NiMh in a crawler even though it’s “slow” is probably the worst thing to be using a NiMh pack in.

Definitely looking forward to your findings. If there’s a way to test load while running I think brushed vs brushless load testing would be some neat data. Eagle tree data logger maybe? Do they still make those? I know from experience brushed models suck the juice out of a LiPo much faster than mild, much faster brushless systems. So that leads me to believe there’s far more amperage draw from a bushed setup compared to brushless… kind of deconstructing the NiMh ONLY work for brushed cars and will not work with brushless argument.

So after doing some testing, it looks like these 5000mAh NiMH packs are producing about 4300mAh. This is a bit better than I expected. Like I said though it's been probably 8–10 years since the last time I rebuilt a battery pack using Sub C's so it doesn't surprise me that they've improved upon the cells some. That being said, they are definitely shy of 5000mAh though.

 

[tudordewolf]

So after doing some testing, it looks like these 5000mAh NiMH packs are producing about 4300mAh. This is a bit better than I expected. Like I said though it's been probably 8–10 years since the last time I rebuilt a battery pack using Sub C's so it doesn't surprise me that they've improved upon the cells some. That being said, they are definitely shy of 5000mAh though.

View attachment 217439

I bet if you run that two more times you'll actually get a better result each time.

I've had 4200mah sub-c's both in packs for my bump box and individually for my glow ignitor, and both when new or after sitting for a few months, they needed to be "refreshed" with a couple charge/discharge cycles before testing to their full capacity, but I did get labeled mah out of them. It depends on the manufacturer too, there probably are some that exaggerate, but I can vouch for tenergy & zeee branded sub-c nimhs from personal experience.

I don't think there's anything that inherently makes brushless incompatible with NiMh, you just have to design for slightly more modest current draw. You can still get some pretty impressive performance because brushless is much more efficient than the brushed motors NiMh is usually associated with, so you will get more usable energy to the wheels, and the amount they can store has nearly doubled compared to when they were the only option. People once made do with 1200mah sub-c packs and plain 540 brushed motors. I think it is important to optimize the build rather than try to over-tax it the way one does when pushing a lipo/brushless combo to the max with higher and higher motor gearing.

That means low kv motor, low motor tooth count - you're not going to go as fast as a lipo might, but you can still make a vehicle that has springy acceleration and is fun to drive. You probably won't get good results with a 4300kv 3650, maybe not even a 3300 - I would recommend an F540 motor, 3100kv, and that should keep the current draw under about 30A or so.

I did a build of the HSP "pangolin" crawler with an F540 motor & a 6-cell Nimh, and it had enough pep that at full tilt it was constantly leaning to the side from the driveshaft torque.

 

[Greywolf74]

I bet if you run that two more times you'll actually get a better result each time.

I'm one step ahead of you. I cycled them 3 times before I ever tested them and then I tested both packs 3 times. The average mAh is approx 4300mAh. Oh, and these are Zeee brand packs.

 

[tudordewolf]

I'm one step ahead of you. I cycled them 3 times before I ever tested them and then I tested both packs 3 times. The average mAh is approx 4300mAh. Oh, and these are Zeee brand packs.

How foolish of me, of course you did, you're the master of battery testing. Not surprised about the Zeee's honestly, I was probably wrong about mine. The tenergy's only claimed 4200 though, and delivered on them.