Reliability of electronics in Li-ion battery devices

[Jeff Layman]

About a month ago I posted that the charging/power electronics in a Hoover Jovis vacuum cleaner had failed after about 6 years. Yesterday our power-failure emergency torch/light obtained from Lidl about 4 years ago (I think it's this one

) didn't come on when we had a power cut. I checked and it too was dead. I think the base unit is working as there is around 13 across the coil, but the 14430 battery in the torch body is at about only 2.2V. I've no idea how long it's been not working.

Am I just unlucky or is Li-ion equipment unreliable? An old B&D Dustbuster finally gave up the ghost after at least 15 years, and a rechargeable torch similarly lasted more than a dozen years. Both had NiMH batteries.

[4587Joey]

Yes.

No, I have never had one fail.

[Animal]

All batteries fail. You did well to get 12 & 15 years from them.

[Jeff Layman]

It's not the batteries I am asking about. It's the charging/discharging electronics, in the devices connected continuously to the charger when they are not being used. I have a 9-years old 18V Li-ion drill which is fine, but the batteries are only connected to the charger when I need to use it. We have another Li-ion battery-powered vacuum cleaner permanently in its charger cradle. It's a couple of years old now, and I wonder if it too will fail within another couple of years or so.

[The Natural Philosopher]

NiMh are not infinite life batteries. All my RC transmitters that had been boxed for 5 years without a charge needed new ones.

[The Natural Philosopher]

Sorry - my last post assumed NiMh.

Li-Ion have also limited life and the older the batteries are the faster they used to fail. Like electrolytic capacitors they have a gooey electrolyte that can dry out

5 years is good going. Electric car owners are in for some shocks after 7-8 years when the garage reports - "you need an £8000 new battery"

[Theo]

There is nothing intrinisically wrong with the charging electronics, only that the reliability of the charging electronics depends on the quality of the charging electronics. Like power supplies everywhere, you can get top-spec units and ones where corners have been cut on spec and safety. It is also possible that you're using them contrary to the design (eg if the manual says 'remove battery from charger once full').

It is quite possible for the battery to disconnect itself from charging once it's fully charged, so as not to be continuously pumping charge into the battery. But it's also possible that a dumb charger/BMS is just holding the output at 4.2v per cell, which isn't something you want to do continuously.

Just like there were fancy NiCd chargers, and ones composed of a transformer and a resistor, you get what you pay for.

Theo

[Paul]

The lithium chargers don't generally trickle charge. That would lead to overcharging.

The rules are pretty strict for the design of such, because of the risk of fire.

If the charger would stop at 80% full, that would extend the service life of the product. Stopping at 80%, roughly corresponds to stopping the charge process just after Stage 1.

Paul