Leakage - Amondotech Titanium 1800 Super High Discharge NiMH

[County]

I have now had at least 2 instances of battery leakage on different sets of batteries (Amondotech Titanium 1800 Super High Discharge NiMH) used for my 9-AA cell Mag 85. I disregarded the first instance thinking it was just an isolated issue. I ordered an entirely new set of 9 only to have the same problem on at least one of the cells. The leakage occurred during charging while using Alin10123's "Universal Ultra Smart Charger (2-12 cells)" with the FM 9AA->3D battery carrier. Several of the batteries were wet, but I couldn't determine which cells had leaked.

I returned the second set of 9 batteries with an RMA to Amondotech for credit, and within the shipping-refund-availability time window, however they did refuse to refund my shipping stating "no trouble found" with the returned batteries.

I have not had any problems using the same charging setup on the Energizer 2500s, Duracell 2500s, and now Eneloops.

 

[light_emitting_dude]

I'm just curious of what leaks out of a NIMH? Obviously alkaline leakage is corrosive but what consists of the NIMH leakage?

Never had a NIMH leak here.

 

[BigusLightus]

I bought 6 cells to test in my 2D ROP and one of them is beginning to turn black after only two cycles in the flashlight and three cycles on the charger. I've never seen this happen before. The set of six that I have did not light up my ROP as well as my Eneloops.

 

[mdocod]

I'm not the most informed on the subject of pack building... But I was wondering.. did you make sure all the cells were in a "balanced" state of charge before putting them in your "pack." ?

 

[BigusLightus]

Interesting that you asked. I've never balanced or measured any of my packs. Never felt the need. However, this time I measured the open circuit voltage of the 1800's after they did not light up my ROP as expected and found five batts at almost exactly 1.43V - 1.44V and the black batt at approx .1.34V. I was really surprised to see how close the 5 were so that made the black one really stand out.

I could measure the open circuit current but I'm not yet convinced that will be a useful measurement. Or would it?

Edit: Just measured open circuit current. Almost 15 Amps for all batts except the black one which measured 14.56. However, I had to fiddle with it to get any measurement at all. So, I'm now thinking that the black stuff on the neg. terminal is preventing the batt from connecting properly. Perhaps this one batt is holding everything back.

 

[mdocod]

it seems to me that when building up a pack, not starting with cells that are in a balanced state would lead to problems faster... However, the nice thing about NIMH and NICD is that these chemistries are very tolerant to overcharging, so you can usually pack charge them even somewhat out of balance and some of the cells are bound to get a little overcharged, but after the pack "rests" for a few hours the overcharged cells tend to settle down and everything balances out.

RC guys routinely buy sets of "matched" cells. Manufactures of high performance cells will test the cells for capacity and resistance and send them in "matched sets" so that the pack will stay the most balanced possible over the course of it's life. I don't think this is necessary in all applications, but it would be ideal.

 

[County]

Light Emitting Dude: don't know much about the chemical properties of leakage out of NiMHs. I can tell you that it reacted to cause a white powderish type material to appear on the inside of the battery tube of my Mag85. It does seem corrosive. Also, the same type of reaction appeared on the metal rod that runs through the center of the FM 9AA->3D holder. The battery holder cleaned up nicely, but I couldn't get the white powdery substance that seemed to have bounded to the tube, fully out of the host.

BigusLightus: After the leakage on my second set of new Titanium 1800s, I also had an instance where one of the batteries had the postive button turn black.

 

[BigusLightus]

I'm wondering now if there is a simple method or circuit that will help me measure and balance my cells or should I just charge each one in a charger with separate channels. Are the open circuit numbers helpful in determining the current state of a cell?

 

[NiOOH]

Leaking of NiMH cells happens when the safety vent opens. There may be three reasons for that
1.overcharge
2.overcharge
3. long storage in fully discharged state. In this case the voltage slowly drops to close to zero. The pressure inside the cell approaches atmosphere pressure, which opens the vent held closed by the pressure difference.
The liquid that leaks during venting is electrolyte. It is a concentrated solution of potassium hydroxide (KOH) with some minor additives. THE LIQUID IS CORROSIVE. AVOID ANY CONTACT WITH YOUR SKIN.

 

[BigusLightus]

In my case I have owned these batts for only 3 months. I seriously doubt they have been overcharged or overdischarged or allowed to lay around too long. I find it interesting to note that I've used NiMH batts since 1998 and have never had one go bad in this manner. I did have some Energizers that died but they never showed any external signs of failure.

 

[County]

I also have been using NiMH for 7+ years, in various applications/chargers, etc, and had never had a leak.

 

[NiOOH]

In my case I have owned these batts for only 3 months. I seriously doubt they have been overcharged or overdischarged or allowed to lay around too long. I find it interesting to note that I've used NiMH batts since 1998 and have never had one go bad in this manner. I did have some Energizers that died but they never showed any external signs of failure.

Another possibility is faulty valves. It could be that they have opened at lower pressure than intended. In any case, with your experience I'd change brands.

 

[BigusLightus]

Sounds like good advice. I'll stick with Eneloops and stop trying to pinch pennies by buying the cheap stuff.

 

[County]

I wanted to report yet another instance of leakage with Amondotech Titanium 1800s NiMHs. At least 2 cells in my dad's 9AA battery carrier for his Mag-85 have started leaking. He charges them using Alin10123's "Universal Ultra Smart Charger (2-12 cells)."

 

[SilverFox]

Hello County,

What charge rate is he using?

Tom

 

[County]

Hi Tom-

That particular charger uses a 1.0A rate. And he is charging all 9 cells at once in the FM 9AA->3D pack.

I have experienced the same issue on 2 separate occasions with the same make/model of batteries. My charge setup is the same as noted above.

Regards,

 

[SilverFox]

Hello County,

I believe the problem lies with the charger...

As you use your cells, they fall out of balance. In order to balance the pack, you need to charge at 0.1C for 16 hours.

That charger is great for the charge cycles in between balancing, but you still need to balance the pack.

The charger charges at 1 amp (the rate you selected) and is looking for a -dV of around 5 mV per cell. If the pack is balanced, this works great. When the pack gets out of balance, one (or more) cells end up being over charged. At 1 amp, the over charge is capable of causing the cell to vent.

I noticed that at then end of the charge that charger does go into a trickle charge mode, but when charging at 1 amp it is only trickle charging at 50 mA. I am not sure if you could balance the pack with this low a charge rate, or how long it would take. The charge acceptance at low rates drops off.

With that in mind let's see if we can make a guess...

50 mA is roughly a 0.03C charge rate. It may be possible to balance the pack if you left it hooked up to the charger for an additional 54 hours after the charge has completed. This is also dependent on the self discharge rate of the cell.

At any rate, it may be worth a try.

Tom

 

[County]

Thanks for the info Tom. Unfortunately this charger doesn't have a selectable charge rate. The only other charger I have is a Duracell 15 MIN charger, but at least it has separate channels with separate adaptive charging for each battery, and does switch to a trickle charge (unknown rate) after the rapid charge sequence. Do you think placing the cells in the Duracell 15 MIN charger for the rapid + trickle sequence is ok to effectively balance the pack?

In the meantime, I could always try leaving the 9AA pack on the Universal Ultra Smart charger for the additional 54 hours in attempts to get a balanced charge, as you suggested.

I did want to mention that after ~10 or so charge cycles with Eneloops that I haven't had any issues..

Thanks for the input!!

 

[SilverFox]

Hello County,

After around 10 cycles, you are due... however the Eneloop cells seem to stay in balance better than most cells.

Individual charging looks like your only other option. Unfortunately the 15 minute chargers only take 4 cells at a time. I believe both the Energizer and Duracell 15 minute chargers have a good trickle charge that goes for 24 hours after the main charge is complete. You would have to put 4 cells, charge them, let them trickle charge for 24 hours, then set them aside. Next you would move on to the next 4, and finally the last cell. At the end, your cells would be reasonably close and you should be good to go.

Tom

 

[paulr]

If you look at the USL thread, the USL builders have also had problems with the Amondotech cells. They're using Elite cells now which seem to be the best so far.

I bought a 10 cell Vanson charger for my mag85, which is not a super fast charger but it supposedly has independent channels. Being able to charge all the cells at once is convenient.