identify: NiCad or NiMh?

electrolyte

Newly Enlightened
Joined
Jan 4, 2019
Messages
61
I have a laboratory freezer (ultralow cascade) that was built in 1996 and the design might go back a couple of years before that. There is a battery pack for the failure alarm to keep that part working long enough send out a distress call in case of main power fail. Battery pack itself has no immediately useful markings on the outside of the wrap or on the tab cells themselves.

My faulty memory tells me that this was a time when both battery types were in wide use. That would probably not be a reliable indicator anyway. Is there any good way to determine if they are NiCad or NiMH? It is a flat, three-cell solder tab pack with two leads n a plug. The only information that I see printed on the pack besides warnings for recycling and disposal are 329C and SL120. I see additional info for voltage (3.6) and 800 mAh rating and I see a reference to "Dryseal".

Is there any reasonable way to determine what chemistry this is? I was thinking maybe density (weight). Note that the batteries have been abused (stored dead) and the onboard battery charger/monitor indicates that it is dead so no functional testing is likely possible.
 

LMF5000

Newly Enlightened
Joined
Mar 10, 2011
Messages
84
Location
Malta
Can you upload some images from all sides? Perhaps there's the crossed-out rubbish bin with "Cd" under it that reminds you not to throw away cadmium-containing batteries?

Anyway, you can "jump start" it by connecting it in parallel with a battery of the same voltage. Eventually it will recover enough voltage for the charger to try to charge it. Put 5 cycles on it, and if it improves, it was most likely NiCd. If the performance is still very poor after 5 cycles, it's most likely Ni-MH. NiMH can't handle sitting at a low voltage as well as NiCd can.
 

Lynx_Arc

Flashaholic
Joined
Oct 1, 2004
Messages
11,212
Location
Tulsa,OK
800ma is probably nicad if the cells are AA sized or larger as when nimh came out in AA sized they were typically 1200mah. Nicads tend to be white shrink wrapped while nimh are often green shrink wrapped.
 

mattheww50

Flashlight Enthusiast
Joined
Jun 24, 2003
Messages
1,048
Location
SW Pennsylvania
To be honest, I don't think it makes any difference whether they are NiCd or NiMh. The output and charging characteristics are virtually identical, the NiMh cells invariably have higher capacity (and often much higher, early AA NiCd's were typically 450-550mah). I'd rebuild the pack with NiMh cells and not worry about it, because at the end of the day, it is unlikely to make any difference. However I'd bet they are NiMh, by the early 1990's there were already issues with Cadmium pollution, so NiCd's were already becoming rare in new products.
 

john1230

Newly Enlightened
Joined
Nov 21, 2016
Messages
43
To be honest, I don't think it makes any difference whether they are NiCd or NiMh. The output and charging characteristics are virtually identical, the NiMh cells invariably have higher capacity (and often much higher, early AA NiCd's were typically 450-550mah). I'd rebuild the pack with NiMh cells and not worry about it, because at the end of the day, it is unlikely to make any difference. However I'd bet they are NiMh, by the early 1990's there were already issues with Cadmium pollution, so NiCd's were already becoming rare in new products.

I was going to say it makes no difference whether it's NiCd or NiMh, but you beat me to it.

electrolyte: I assume that since the freezer is classified as "laboratory" you have access to electronic equipment? if so you can solder 3 Eneloops together and make a replacement for the original battery pack. Although by the age of your freezer, the Eneloops will out last the motor on the freezer itself. So I don't know if it's worth the cost/hassle.
 

fmc1

Enlightened
Joined
Mar 16, 2017
Messages
216
Location
Long Island NY
If you are going to replace them for sure I would go with NiCd's. The main reason is you have no idea how the charging circuit works and NiCd's will be way more tolerant of things like trickle charging, long top offs and high negative deltaV termination. All of those will damage LSD NiMh's. Tenergy NiCd AA's are rated at 1000mAh, accurate for the old ones but the newer ones that I bought this year should be rated a little higher. I'm a big eneloop fan. I have over 100 of them but they would not be my choice for this application.


Frank
 

Sirstanky

Newly Enlightened
Joined
Nov 11, 2018
Messages
6
From 1996 and 800 mah, I'd say nicad. Nicads are more robust than nimh cells in 1996. My RC cars in 1996 ran nicads up until nimh became mainstream around 1999. They are getting hard to find as far as replacements. You would be gone swapping it out for a similar capacity nimh 3 cell/3.6v pack. The charging is pretty much the same (delta V) with constant current.
 

electrolyte

Newly Enlightened
Joined
Jan 4, 2019
Messages
61
Thanks for your kind and thoughtful replies and I apologize for my delay in thanks. I have to check to see if I can get notifications of responses to my threads. I did come back and write thanks one day, but IIRC, I had browser problems and apparently, it did not stick.

The wrapping on the pack is not green, now white, but yellow :rolleyes: I had pretty much decided that they are most likely NiCad cells. I judge by manuals from similar equipment from the same manufacturers. I am pretty sure the charger circuit is a pretty dumb because the manuals all say that it takes a few (or many) hours to charge a fully discharged battery. That is why I wanted to avoid NiMH if it was indeed a NiCad OEM. I reasoned it is trickle charging.

This is a bioscience lab and unfortunately, the only test electronic equipment are the DMMs or AMMs and anything else that I bring from home. We do have some decent old-school power supplies. Most of them have, unfortunately, specialized use and the safety controls on them cut them off if the load is not as expected. They don't like batteries which is very frustrating.

I did a little more study of the manual and took a chance on a google search of the straight-up manufacturer part number + battery. (I did not call about replacement part price because it would have been a PITA and priced like solid gold.) Turns out that they just borrowed the Nexergy (400116) number for a 3-cell, 800 mAh pack. So there we are.

We are lucky enough to have this very freezer as a spare. They are expensive (maybe 15 kilobucks) so many operations don't have that luxury and have to scramble around sticking materials into other freezers and gatheing up coolers and dry ice if one fails. That leaves me, however, with the problem of how to keep a battery around for a freezer that is turned off most of the time. I considered buying an RC charger, then maybe find an old portable phone charger to maintain a pack. Then I decided to let it ride and if we have to start it up in an emergency, I'll grab a (bulkier) battery holder out of my parts drawer and graft it in there. I'll throw 3 old NiMH batteries in until I can buy some NiCads. There is plenty of space behind the control panel to fit it in somehow. After that, it would become the permanent solution to the storage issue.
 

Lynx_Arc

Flashaholic
Joined
Oct 1, 2004
Messages
11,212
Location
Tulsa,OK
Yellow is almost always nicad from my experience. One problem you can get from trying to replace nicad with nimh is nicad cells can often deliver more current than nimh cells. If it is easy to get to and you can disable any charging circuitry you may consider a lithium ion based battery pack and charger solution as the voltage should be the same. 3x18650 if it would fit would be optimal. The only issue with lithium ion is typically not wise to leave the battery pack plugged into a charger because by chance it could trickle charge it a little.
One solution could be to buy a power bank and tear it open and run wires from the LED board and micro USB ports to remote ports and LED mounted conveniently so you can plug in a charger when it needs charging.
 

electrolyte

Newly Enlightened
Joined
Jan 4, 2019
Messages
61
Thanks Lynx, I had though of digging onto the board and disabling the charging ability. Your suggestion is far more elegant than I could plan. I wish I had time, but this has to remain as a small project and not approach full-blown hobby status.

I suspect that the NiMH would provide power fast enough, but I know that I'd have to check.
 
Top