Solartron 7081 Battery Question

[essele]

Hi,

I've just started looking at a Solartron 7081 that I bought for repair ... it has an NVM FAIL error, which is not suprising given the ER3400 is completely missing!

But while I wait for a new(ish) one to arrive I've been looking at other issues ... and I'm a bit confused about the battery situation.

The battery on the lower board is a 3.6V lithium inorganic battery which is completely dead ... I'm assuming I can just replace this with another 3.6V lithium battery, something like this: https://uk.farnell.com/eve/er14250p/battery-lithium-1-2aa-3-6v-axial/dp/1365936

The battery on the IO Board is the one that's confusing me ... in a number of the forum posts about the 7081 this is talked about as a Ni-Cd and is indeed shown on the schematic as a 3.6V NiCAD with what looks like a charging circuit.

At least one person has replaced this with a supercap, which I understand ... however, both in my device and in a number of post in the forum this has been replaced by a lithium battery ... in my case an RS 593-473, these are not rechargeable!

Surely this is a problem?

Wouldn't I be better off with one of these?  https://cpc.farnell.com/varta/55615603940/battery-ni-mh-mempac-pcb-3-6v/dp/BT00152?ost=bt00152

[justanothername]

It has a charging circuit, so the normal way would be to change to a supercap or a NiMh battery.
Since it does trickle charging it is not that critical to use NiMh instead of NiCd. If you want to be safe, change R403 to 1k or higher.

However you can use a primary cell (Li-SOCl2 - the have a large capacity). Then you may want disable the charging circuit. The easiest way would be to desolder R403.