Rechargeable batteries for Argus2 (and 1)

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Rechargeable batteries for Argus2 (and 1)

Post by forum_admin » Tue Jan 19, 2021 7:09 pm

By now most of these batteries are 10 years old, even if the original fire service users bought some new ones near the end of production.

Before condeming a pack, try a long slow manual charge of 100mA for a day on a constant current supply. Batteries that have been stored for a long time need to be 'woken up' slowly. One effect of charging cells that have been idle for a long time is that the reducing internal resistance looks like a battery that is charged (as NiMH and NiCd drop voltage when full) so the charger stops and then indicates full as it knows no better, although the battery bar will still be low as it has counted the charge in and out. For that leave for 2 hours (there is a slow top up charge in the Argus charger) remove and reinsert to trigger a new charge cycle.

The bad news with Argus1/Argus2 rechargeable packs is that they are solvent glue sealed, so any form of repair to replace cells is a problem, as is rebuilding them again given the lost material to restore. If you cut 18mm back from the contacts end with a razor saw you will be just clear of the contacts block so the cell pack will come away with the contacts leaving an empty sleeve.

The pack is 8 series NiMH flat top welded cells, 9.6V constructed 2x2x2. This is not a very common shape, however it seems to be a shape used for some Tamiya models which might give you a lead and some seem to be available in the hobbysit retail side. Avoid using conventional top hat / tag cells as the resulting assembly is likely to end up too long. For cells avoid the 'highest capacity' no-names from China in eBay which will be rubbish after a few cycles. Cramming in each extra 100mAh usually halves the service life.

The control board inside the battery operates as a capacity counter and is reset by removing power, resetting to the preset maximum capacity and 'pack empty'.
If the pack you fit is already full, the counter will not count up much when charged and show a flat battery. (ie 'empty plus no new input'). Best is to fit an empty pack and then charging it the first time sorts it.
If when fitting the pack you get a brief contact the pack might just learn a new maximum capacity of zero, so will never show above zero. That is only fixed with a reset. Best bet is to pool solder on the PCB and then drop the +ve wire on top.

An alternative is to put bare retail NiMH cells in the AA carrier. The battery bar will be misleading though, as it is set for the discharge profile of 8 x AA not 8 x NiMH
To use the camera charger either drill out the mechanical limit pin. or remove it from the charger, and the charger will charge away happily. The charger does not interact with the pack apart from showing the battery gauge level.


Bill

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