Battery life and behaviour

[tagh]

I have two Black and Decker lithium 36volt batteries which power three garden tools. On of the two seems to be misbehaving, indicating it is fully charged, then empty then half full and cutting out when cutting after a short while, then restarting again. What does this imply, please? Is there anything that can be done to restore it?
The other battery seems perfectly normal.

Thanks in advance.

[RobertArthur]

@ Tagh, any feedback from the battery charger? Is there a cure for this intermittent behaviour: I doubt it. The traditional methods, run it almost empty, fully charge it with a high current using an external power supply are not always safe in the case of lithium-ion batteries. Handle and charge with care. The magic freezer trick to get its capacity back (another type of problem): I never tried it.

[tagh]

Thank you RA

[hughnique]

I bought a couple of replacement batteries for my old Dewalt drill when one of the two I already had refused to take a charge, I got them from Ebay and to all intents and purposes they appeared to be genuine Dewalt. Alright for a couple of months then they started to flag a bit, still usable but need frequent charging. The batteries I am having trouble with now are for the Dect phones, they say they are fully charged but they won't last a female chinwag, easy to obtain AAA's though.

[Hotrodder]

I had the same problem with a dect phone. I have a pair that rest in their own separate chargers. One of them was running out so quickly it was impossible to have even a moderate conversation so I replaced the batteries in the phone with new ones. The problem persisted. I tried again with higher amperage batteries but still no result. Then I suspected it was the charger base was faulty. Got a S/H one on ebay and now the phone works fine with the same longevity as its mate in the other room.

[Hotrodder]

Rechargeable batteries that are supplied with a device normally serve well because they are subject to quality control standards set by the brand name manufacturers. Most of the "equivalent" replacements available online are not, so its a gamble. Some are reasonable. Some are junk. And branding printed on the battery pack is no guarantee its not a fake. A replacement from a bricks and mortar dealer will cost almost as much as a new tool, phone, etc. but at least you have a genuine guarantee in case of trouble.

[RobertArthur]

@ Hughnique, a trial and error approach is not bad at all, but measuring is sometimes even better. These little NiMH triple-A batteries have, fully charged, a voltage of about 1.44 V. Two in series and you need a charging voltage of more than 2.88 V. An example of our Panasonic DECT phone: 5.39 V.

[rabbit]

There is an article today in the Times that say the London Fire Brigade attend a lithium battery fire every 2 days and 8 people have died as a result since 2020. Usually caused by cheap lithium battery replacements. I had a camera catch fire in my luggage. I always buy premium brand now.

[niemeyjt]

And if you ever puncture one, they really go off big time and take a lot of extinguishing. Hence if you drop one in an aircraft they say not to move the seat and to call a member of the cabin crew asap.

I would agree about buying manufacturers' own batteries and not cheap knock-offs.