Batteries - Low Self Discharge?

[SupraChrgd82]

1 hour ago, Gebbly said:

How do you find that out. Are there battery details that indicate this rate of self discharge?

45-60 minutes would be more than enough for me from a single battery. Its certainly worth taking note of, thanks. I would be running the standard torque tuned Tamiya motor (brushed) that came with my kit and mostly running it around my garden which is a mowed lawn.

Noted by runtime.  If the 5000’s sit for a month (ish), the distance the crawlers travel is about 1/3 of what they travel with a fresh peak charge.  The 3000’s go about 3/4 of their peak charged distance. 

[Gebbly]

Wow, thats a surprisingly large difference in characteristics. That would never have occured to me, great tip, thanks.

Theres probably some interesting electronics/maths behind that which I might dig around to learn one evening.

[Saito2]

Out of curiosity, I've read online Nimh batteries should be stored at 80% charge, 60% charge and no charge. So what's best?

[sosidge]

10 minutes ago, Saito2 said:

Out of curiosity, I've read online Nimh batteries should be stored at 80% charge, 60% charge and no charge. So what's best?

Never no charge on a NiMH. We used to store at 0.9v per cell. I'm not sure what your source for that info is, but 80 or 60 won't really matter because the self-discharge rate is so high. If you leave a NiMH for a week it loses so much performance, always charge just before use if you want the pack to perform well.

[wolfdogstinkus]

If the guy wants to try LSD, let him try LSD!!!!

Those AA's from Turnigy /hobbyking were really good........ for torches and Thomas the tank engine but I wouldn't run a Tesla on them???.. although Elon may disagree.

[Willy iine]

3 hours ago, Saito2 said:

Out of curiosity, I've read online Nimh batteries should be stored at 80% charge, 60% charge and no charge. So what's best?

I believe you just need to keep some level of voltage in the cells.. I've had NiMH just drain to zero and die on its own, and others that didn't die and were recoverable.  

But the packs with some charge at all times has not died.  I just charge or peak it every now and then to keep them alive.  Nothing scientific for me.  

[alvinlwh]

4 hours ago, Saito2 said:

Out of curiosity, I've read online Nimh batteries should be stored at 80% charge, 60% charge and no charge. So what's best?

 

On 6/12/2022 at 2:37 AM, alvinlwh said:

While I had seen a number of lengthy posts of views (nonsense) on storage charge for NiMHs, broadly speaking, straight from the manufacturers, these cells store just as well full charged or drained. The only recommendation is to cycle them once a year (hopefully you will use them more frequently than that) and a few cycles will restore a pack that had been deeply discharged. 

https://www.pmbl.co.uk/blog/how-to-store-nimh-battery-packs

Also also to store them at reasonable temperature, which basically means room temperature is fine.

 

[Saito2]

10 hours ago, sosidge said:

Never no charge on a NiMH. We used to store at 0.9v per cell. I'm not sure what your source for that info is, but 80 or 60 won't really matter because the self-discharge rate is so high. If you leave a NiMH for a week it loses so much performance, always charge just before use if you want the pack to perform well.

Thanks. Sorry about the stupid question. I remember Nicads being discharged but thought Nimh weren't supposed to be left flat. A quick random google search netted me various answers and confused me.

6 hours ago, alvinlwh said:

  On 6/11/2022 at 9:37 PM, alvinlwh said:

While I had seen a number of lengthy posts of views (nonsense) on storage charge for NiMHs, broadly speaking, straight from the manufacturers, these cells store just as well full charged or drained. The only recommendation is to cycle them once a year (hopefully you will use them more frequently than that) and a few cycles will restore a pack that had been deeply discharged. 

https://www.pmbl.co.uk/blog/how-to-store-nimh-battery-packs

Also also to store them at reasonable temperature, which basically means room temperature is fine.

Thank you. Sorry I skimmed through the thread too fast, missing that you had already answered my question.

[nowinaminute]

I don't think Sanyo or any other LSD manufacturer ever made sub c cells, sadly.

It's a shame because even the AA Eneloops pack quite a punch for what they are. I've seen them just about handle sustained 10A loads on flashlight forums. Probably not recommended for continual use, but impressive for an AA, none the less. I've managed to run 280 and 380 brushless motors from them fornshort periods where any other AA NIMH I've tried wouldn't even get the motor turning.

I bet they would perform pretty well in sub c format, along with the LSD benefits.

I don't think they even make normal C or D cells, though. I'm pretty sure they have AAA and AA cells inside, running in parallel. 

I guess they just came too late in the game for it to be worthwhile them making them in sub C format, especially if it wasn't even economical to make them in regular C and D without "cheating"

In regards to "balancing" NIMH, it's worth remembering you can sort of balance them by doing a very low current trickle charge with a "dumb" wall charger of say 150ma output. NIMH cells can happily dissipate that excess energy as heat so its possible to leave the pack charging until all cells are full. Definitely not recommended with higher currents, like 1a+ though, as it will cook the cells.

[El Gecko]

On 6/17/2022 at 8:36 AM, Willy iine said:

I believe you just need to keep some level of voltage in the cells.. I've had NiMH just drain to zero and die on its own, and others that didn't die and were recoverable.  

But the packs with some charge at all times has not died.  I just charge or peak it every now and then to keep them alive.  Nothing scientific for me.  

Same for me. I have a decade-old Traxxas 5000 that still holds a "charge" but at a significantly lower peak voltage than other, newer batteries. But it's not because it's old, it's because it's the only one that's been drained to absolute zero and somehow recovered.