Odd Nokia fault

It happens with all three of the BL-4C cells I own. Plus, remember that the phone works for a day or so - after being judged to be flat - and then another day or so - all with the same cell.

Probably high internal resistance in the battery. Many phones of that vintage could not operate from an external charger without a good battery being present due to the high peak current requirements when transmitting (which they do autonomously to register with the base station). John

I'd hazard a guess that the battery is dying. When my galaxy was in its battery death throes all sorts of things related to 'gimme more amps' got very flaky.

Id hypothesise the battery has gone a bit high impedance and from time to time under use it flags a 'low battery' warning even though it is charged. New batteries seem to be inexpensive and available, so Id try that

If all three are of the same vintage, that may not be as significant as you would like.

Sadly repairing a mobile phone of the more old or budget end of the market doesn't make sense. If it's not the battery...it may be skip time.

you can get a new one for under £40