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Grumpy pants

Can you revive NiMH batteries?

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I went to use these batteries after a long period of dormancy but they hold little or no useful charge, they appear to accept a charge but that is not the  translating into anything worthwhile. 

At a guess they are 6-7 years old, they haven’t had a huge amount of use and they have been laid up for probably the best part of 3-4 years with the very rare charge to test motors, odd quick run type that type of thing. 

I really do not want to buy replacements or change up to Lipo- so is there anything simple in lay mans terms I can do?

image.jpg

 

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Repeated charge/discharge cycling might bring them back to some sort of usefulness. Worth a try!

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They are either almost-dead or all-dead.  

Charge, let it cool, discharge, let it cool...  Repeat that 5-6 times.  (if you don't cool between charges and discharges, you can quickly kill them with heat)  If they don't hold charges by then, it's all-dead. (Often one part of the battery is extra warm)  Nothing to do but to recycle them.    

Since you have 3, one of them might be almost-dead, and hold like 2000mAh.  As Turnip said, it's worth a try.  

 

 

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Strange they’re dead so young.  When I got my lad a neo scorcher recently I bought a new nimh but also dug out my old nimh that must be getting on for 15 years old.  To my amazement the old nimh charged up and has been running alongside the new battery with good results.  I expected it to last about 5 mins but it happily runs for ages.

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I agree with the others. Over the course of nine years, I had four Carson Modelsport NiMH packs (3000 mAh and 4500 mAh) go dead on me.

I tried repeated charging/discharging for a few times.

 

I monitored the charging process using one voltmeter and one ammeter, and it became apparent that the packs accepted only a tiny fraction of their original capacity, so after being charged to peak voltage they dropped back below nominal voltage soon after being disconnected from the charger.
 

I brought them to the battery recycling bin of my local supermarket.

 

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35 minutes ago, TurnipJF said:

Repeated charge/discharge cycling might bring them back to some sort of usefulness. Worth a try!

Agreed, my charger gives an indication of how well the battery got charged, discharge and re-charge cycles has improved batteries before.

 

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You are fortunate that you have a well balanced battery, James.  

When you were using it, it must have never reached full-drain.  What kills a pack is an unbalanced cell.  You can never have all 6 cells to hold exactly the same amount of energy.  One of them is bound to be weaker than the other 5.  While stored, it gives all its current to the other 5 cells.  But somehow all 6 cells of your pack were close enough in their capacity, they maintained an equilibrium. That's as rare as 6 countries never going to war for 100 years.  

 

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My two HPI Plazma batteries have exact the same issue. The batteries take  a charge but have no real punch. Item related? 

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39 minutes ago, Juggular said:

While stored, it gives all its current to the other 5 cells.  

I don't think you really mean this and that's it's just a matter of choice of words, but just in case somebody should think it's literally as described, I feel obliged to comment.

In batteries with the cells connected in series and in storage, no current can flow from one cell to another. That's only possible for cells connected in parallel, and in that case, current will flow from the cell(s) with the highest voltage to cell(s) with a lower voltage and until cell voltages are the same. That will almost without exceptions be from the best cell(s) to the cell(s) in a poorer condition and/or lower state of charge.  In batteries with the cells connected in parallel and with cells in different states of deterioration, the resulting different rates of self discharging and different actual capacities will contribute to (further) imbalance within the battery.

However, self-discharging is not causing currents to flow between cells in a battery with the cells connected in series. The loss of energy happens within each single cell, and is lost in a chemical process that produces heat and increases pressure. For any current to flow in a battery with the cells connected in series, the battery must be connected to a load (or short circuited). In an open circuit (battery disconnected) no current can flow, neither out of the battery, nor within the battery itself.

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Ok all good tips gang, thank you.

I’ve just recharged them for 3rd time using a replacement charger for a run later on today.

I’ll go through the charge, discharge routine 3 more times in the hope of a resurrection.

If not recycle them and replace ☹️

Unfortunately I sold 3 new batteries just 4 weeks ago for half cost of replacing these as I didn’t think I needed them.   

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I shall do the same by discharcing the batteries with a Spintec discharger (set on Constant Voltage with a current of 35A) and charge the batteries with 2.5A. Let's see if they come back to life.

Plazma discharge.JPG

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I have tried this too with a few packs , some still perform better than others ( I think one of them is also a Plazma ) , but good for backyard bashing

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3 hours ago, Juggular said:

You are fortunate that you have a well balanced battery, James.  

When you were using it, it must have never reached full-drain.  What kills a pack is an unbalanced cell.  You can never have all 6 cells to hold exactly the same amount of energy.  One of them is bound to be weaker than the other 5.  While stored, it gives all its current to the other 5 cells.  But somehow all 6 cells of your pack were close enough in their capacity, they maintained an equilibrium. That's as rare as 6 countries never going to war for 100 years.  

 

Strange then.  But I always used to recharge them after use so maybe that’s why?  Last time I would have used it would be around 12 years ago (until last weekend) but no doubt it’d have been charged after I last used it.  It’s done the last two weekends with me and my lad & it’s been decent enough.  The new one lasts a bit longer obviously but not by a load.

 

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I'm in the same boat. All the NiMH only lasts about 10min. per pack, sometimes shorter... I reckon they should at least last 20 minutes or more... my cars all run stock... 

It seems that even the older Tamiya Pack that's a NiCd holds more charge after being stored for more than 10 years...

I have these... 

eVF26Re.jpg

Havent used them in aabot 4-5 years and I dont want to replace them... they were used sparingly... 

I have 2 IMAX B6 clones that I dont think work well with NiMh so I've been using an older peak pulse charger... problem with that specific charger is it discharges the NiMh pack all the way down to 2.6v before charging... it makes me wonder if I should now buy a better charger, or change to LiPo and make use of my B6 clone chargers...

 

 

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I've never really managed to revive a nimh pack - nicads do respond though. I've not looked back since switching to LiPo...

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8 hours ago, Gruntfuggly said:

I've never really managed to revive a nimh pack - nicads do respond though. I've not looked back since switching to LiPo...

I’m not ready to take on the cost or learning curve yet tbh. 
 

I’ll squeeze the life out of these NiMH and then I might have to come over to the dark side 😂

 

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I am just charging them up for the 4th time, but based on last nights run I would say- 

1. Is as dead as a dead thing

2. Is in the ambulance on it’s way to A & E 50/50 chance of survival

3. The magic will come back
 

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The end just blew off battery  2 💥-   I’ve turned the Amps down a bit for battery 3 😂

image.jpg

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51 minutes ago, Grumpy pants said:

I’m not ready to take on the cost or learning curve yet tbh. 
 

I’ll squeeze the life out of these NiMH and then I might have to come over to the dark side 😂

 

Let me know what it is like on the dark side.

The first of my HPI Plazma's took a charge of 3800 mAh. Using it in a 540 equiped car it gave the car run time but is not as fast as with my other packs. Giving full throttle from stand still caused the car to stall. By giving moderate throttle the car started moving and gained speed. 

Started the next cycle just now.

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21 hours ago, No Slack said:

I shall do the same by discharcing the batteries with a Spintec discharger (set on Constant Voltage with a current of 35A) and charge the batteries with 2.5A. Let's see if they come back to life.

Plazma discharge.JPG

Lol.

Good job. You were only supposed to blow the b**** end off. Lol

Don't turn the amps down next time. 

Just film it, turn the amps up. 

Id strip the cells and use a single cell for LEDs or something else like see how many you can fit in a tt01, then wire them all up together for a Ni-mh speed run. 

 

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1 hour ago, No Slack said:

 

Sorry No slack. I quoted you by accident and can't remove it.

Edited by wolfdogstinkus

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2 hours ago, Grumpy pants said:

The end just blew off battery  2 💥-   I’ve turned the Amps down a bit for battery 3 😂

image.jpg

Film it.

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Whoa! 

Out of curiousity, anyone here tried to re-pack their NiMH? I am currently debating if I should open mine up and see which cell is kaput and try to salvage the usable ones... 

I certain that there's some good cells in my packs as it still packs a punch but just doesn't last long anymore... 

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My second HPI Plazma accepted a charge of 4000 mAh but is also a bit weak speedwise. But it seems both batteries come to life a little. Next cycle is now happening.

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