On Sat, 21 Jul 2018 19:56:27 +0100, you wrote:
On 21/07/18 19:40, anotherlin@... wrote:
Hi everyone,
I need to replace the backup battery of a DM5010. It has leaked but I cleaned up the mess.
The service manual specifies a Nickel Cadnium 2.4V 150mAH at 14mA.
So far, I was able to find (on Mouser) a 2.4V 110mAH ().
Does it meet specification? In particular, we have 0.11AH vs 0.15AH.
I've absolutely no experience with rechargeable batteries. So I welcome your help.
One point to be aware of is how it is charged. If a cell is charged too fast or
for too long, it will be damaged.
Quite true.
An "intelligent" charger will determine when a cell is fully charged, and stop
charging. Frequently a backup battery does not have an intelligent charger, but
simply "trickle charges" the cells all the time it is connected to the mains.
At that time of development, there was really no such thing as a smart
charger, and it would have been about as complicated as the existing
CPU board. All they did was to trickle charge it. The "use" senario
was to have the unit plugged in and on most of the time, certainly
enough (averaged over a week) to keep the battery charged when
considering the power needed to keep the CMOS RAM alive.
So you probably need to determine the trickle charging current in the circuit,
and compare that with the datasheet's spec. In the absence of more specific
information, it is usual to assume than trickle charging at "C/10" is OK, which
would be 11mA for a 110mAh cell.
I think it was more like 1/20th C, but that's what I've remembered.
All that was really needed was to put in more (use the 66% rule) than
got taken out when the meter was turned off.
Harvey
