Advice on CMOS Battery

Heatvent

New Member
Sep 19, 2019
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I need to replace a Tadiran TL-5242X 3.6V lithium high energy battery. The ones I see online don't have the same micro connector (not sure what type exactly maybe something in the JST family) and they run about $14 + shipping. Not sure if there are other options for replacing (I will need to salvage the connector cable anyway).
  • First, I assume this is not rechargeable (doesn't say it is on the case and is from a 1991-ish 386 PC)
  • Could I get away with a 3V CR2032 instead?
  • If not could I just use a generic AA format 3.6v lithium battery and a AA holder (pretty sure this will be fine)?
  • Is there a common setup people go with for XYZ reason?
Thanks!
 

Dale Mahalko

Member
Jul 25, 2019
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8
Due to the ongoing problems of old batteries sometimes leaking and destroying circuit boards, my personal view is that you can prolong the life of your hardware by keeping a potentially leaky battery away from it, using a long pair of wires from the battery terminals to the circuit board, and putting the battery inside a poly sandwich bag zip-tied somewhere to the case, away from the chassis.

This is what I did with an old Amiga 2000 with a Video Toaster. The battery is similarly floating in midair inside a ziplock bag tied to a metal support bar across the top of the case, using about 25 cm of wire to isolate it from the motherboard. The Amiga is currently in a self-storage facility and I don't have to worry that I might go back in 5 years and find the board traces destroyed by a dying battery.
 

Heatvent

New Member
Sep 19, 2019
15
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So I have a second PC and this one has a pair of Panasonic BR 2/3A 3V lithium batteries in series (so total of 6V). Hard to tell if that was stock from the factory or something replaced along the way. However, it does have the rather odd connector (not JST but something around the same size but not sure if I have seen this before). So chances are it is stock. For this one maybe 2 stacked CR2032 batteries?
 

Dale Mahalko

Member
Jul 25, 2019
52
9
8
It is best to look for engineering specifications so that you do not overvolt the device with your jury-rigged alternative.

Google search for: Tadiran TL-5242X 3.6V lithium

First result after the ad:

Click on "Technical datasheet"

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The BR 2/3A is still commonly available.

Poly-carbonmonofluoride Lithium Batteries (BR series), specifications

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If a battery has wires or flat metal tabs attached to the terminal ends in an unusual manner, they are almost always spot-welded to be like that, because just a tiny amount of power is needed in a very small area, and the battery will not be damaged by the sudden instantaneous heating and cooling of the spot-weld.

If you have a battery shop like Batteries Plus near you, they have one of these tiny spot welders and can probably fabricate whatever wire or terminal configuration you need, if you can provide them with the original or at least some good photos of it.

DO NOT SOLDER WIRES. The high heat of soldering and the slow process of heating until the solder melts and joins the metals, may cause the battery to melt, bulge, spray corrosive liquid, explode, or start burning.

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An off-board battery holder of some kind, with long wires attaching it to the circuit board, is the best route so you are not cutting wires and having to redo all this again in 5+ years from now when the batteries you are installing have gone dead again.