Substitute for lithium coin cell for time backup

[muttley]

I have a reptile thermostat/timer in which there is a backup battery to hold the time during a power outage. The battery is a LIR 1620 lithium coin cell (3.6v, 20 mAh). I cannot source this cell anywhere in Australia and have found only wholesalers (1000 units min) online. Am I able to use a different chemistry in its place? I have a NiMH 3.6v 70mAh from an old pool chlorinator that I could use.

 

[CocaCola]

No you can not use a different cell tech, the charging circuit will not be compatible...

Have you looked on Ebay? You can get one for about $4 delivered...

Heck almost any store in the US that sells batteries has CR1620 or CR1632 on the shelf... The CRs are slightly different (not rated or chemistry designed for recharging, and probably won't take a charge but you will be able to still use it as a battery backup when the device is off, in a pinch) they will work for the immediate time if it's an emergency... Just swap it to a LIR when you get a chance... Don't keep the CR in there long or when the unit is plugged in, and best to check it to make sure it's not overheating or what not to avoid trouble, basically just use it as a temp fix if you really need to, or wait for the LIR to come in from China...

Worst case if you have to and there is space use a LIR2016 or LIR2032... A little larger...

FYI the first two numbers are the diameter in mm, the next two are the mAh... The higher the mAh the 'thicker' the battery is, for example a CR2016 is half as thick as a CR2032...

Have you checked any computer repair shops that might have them in stock for motherboard clock backups?

 

[(*steve*)]

Yep, you can find CR1620 cells all over the place. I have seen them in Chemists, supermarkets, hardware stores, etc..

Find something with "1620" in it's part number, that looks pretty much the same, and has the correct voltage (often labelled as 3V).

 

[muttley]

Thanks for the replies appreciate it.
CR Lithium 3.0v coin cells are plentiful in Australia too bit I am after a rechargeable figuring that I can´t solder in a non-rechargeable as the device will be trying to recharge it (as Coca Cola indicates).
There is plenty of space so will now broaden my search to include LIR 2016 and 2032.
I did try ebay for a LIR 1620 but no hits - I will try again.... I think I was including ¨3.6v¨ in the search because this is what I figured was important - wanted to exclude any 3.0v that would come up.

 

[CocaCola]

Also check the main ebay site not the local ones, and contact the sellers about shipping to OZ if they won't...

Also supply houses like Mouser and Digikey have rechargeable coin cells, again maybe not a drop in replacement but if there is room...

http://www.mouser.com/Power/Batteri...70eZ1z0wd7g&Keyword=Rechargeable+coin&FS=True

http://www.digikey.com/product-sear...argeable-secondary/394468?k=rechargeable coin

I would speculate that a nominal 3 volts is fine, there are times that it would not be but in most cases you should not have a huge issue...

 

[(*steve*)]

Lithium and NiMH have different charge regimes.

If you have room, you may be able to get away with replacing it with the smallest LiPo battery you can find (likely to be close to AA size)

I'd double-check that it is rechargeable. There are a number of PCB mounted lithium batteries that are not.

 

[(*steve*)]

An Australian source is here.

Beware that not all are rechargeable (as I have noted above)

edit: they'll probably hit you up for $10 in postage unless you can get in an pick them up yourself.

 

[muttley]

Again - many thanks for your advice.
I found LIR 2016 and 2032 on eBay USA - just need to cross the shipping bridge. Here in Oz Li batteries need to go by road.
I took a couple of pics when I opened up the thermostat. It appears to have an option to install a LIR2032 - just need to figure out the terminations for BAT1. The original 1620 was soldered vertically into the two holes close together next to where it says BAT2. I have a cell holder so the battery can sit flat. Here goes trying to attach the pics....