battery charging while not using devices

[simonineaston]

A lot of my lipo powered devices don't see as much use in winter as during the warmer months, southern softy that I am... What is folks' experience of keeping their batteries in top condition while they're infrequently used? I'm thinking in terms of whether to keep them connected to their respective chargers all the time - or else letting them drain and then charging them fully as the warmer months get near. Are there any Golden Rules to stick to charging to make sure the battery packs last as long as possible?
I've read that periodical full discharge is a good idea, however a battery pack I recently let empty now has a bms issue that I've worked out is to do with the cells becoming unbalanced. The bms sees this as unaccepatable and the pack's now unusable. While I'm all in favour of lipo battery management systems reducing the risk of fire (see topics on the subject of fires in home...) I obviously want to emply a charging regime that results in the battery pack having the longest possible life.
Any advice?
Note I'm thinking about lower current batteries for gps / phones etc. rather than bigger packs for cycles with loads more ooomph, but I guess the principles are similar / the same.

[mxg01]

The only thing that everyone seems in agreement about is, don't store them empty. Everything else on this subject has as many opinions as there are people willing to give one.

[simonineaston]

hahaha! Thanks for the advice

[axel_knutt]

Since the lifetime is supposed to be maximum when they're kept about 50-60% charged, anything aimed at achieving that would be my choice if I could be bothered. Gauge how quickly they discharge & charge, then give them something like a few minutes once a month if you can remember.

Growing up in the 60s & 70s in the days when the Ever Ready man used to have to restock shops with fresh batteries once a week on a sale or return basis. I've always had a jaded view of batteries, I associate them with torches that don't work when there's a power cut, toys that stop after ten minutes, and corroded contacts. I began to warm to them with watches and calculators etc that run for a year or two, but now we're going backwards. Batteries that die if you charge them and die if you don't take me back to a time when all I wanted for Christmas was a mains transformer for my battery powered railway set.

I'm typing this on a laptop that I still regard as nearly new, but the battery has been knackered for a year, and you can't just unplug it and replace it.

[mattheus]

Growing up in the 60s & 70s in the days when the Ever Ready man used to have to restock shops with fresh batteries once a week on a sale or return basis. I've always had a jaded view of batteries, I associate them with torches that don't work when there's a power cut, toys that stop after ten minutes, and corroded contacts. I began to warm to them with watches and calculators etc that run for a year or two, but now we're going backwards. Batteries that die if you charge them and die if you don't take me back to a time when all I wanted for Christmas was a mains transformer for my battery powered railway set.

Can I interest Sir in a Di2 Groupset? Hmm?

----------------
I feel your pain Mr Knutt! I suspect the reason we've apparently gone backwards recently is users' desperate clamour for:
- convenience, and
- low price above everything.

Would it improve your faith in battery technology if you knew that there are satellites in orbit around us that have recharged their cells - typically once a day, or more - for 14 years without significant* fade?

(it helps that they usually keep them above 80% charged. Amongst other factors ... )
* a weasel word in this context, sorry.

[simonineaston]

Growing up in the 60s & 70s in the days when the Ever Ready man used to have to restock shops with fresh batteries once a week

I'm of the Duracell generation When those rather odd French lamps came onto the market, some of us thought we'd died and gone to heaven!

onandonandon...

Duracell_Bunny.png (106.93 KiB) Viewed 935 times

[rjb]

Go back to university.
There's some very useful information here. https://batteryuniversity.com/

[PH]

How long are they inactive?
In my case it's most likely to be lights not used much in the summer months, though even then there's be a couple of summer overnights I'll use them, or take them touring just in case. So probably a maximum of three months, I'll put them away fully charged, and recharge before use, which is no more than a 10 - 15% top-up. I'm not suggesting that's optimum or perfect, but I think it's good enough for me. As already said, the thing that really does harm is to let them fully discharge.

[simonhill]

The two big gel batteries in my campervan, I keep topped up.

I am often away in the winter and fully charge, then remove all fuses so no drain. Nearly 100% after 2 months.

I'm told this is best.

My campervan has a display unit. Very low power, but over a few months enough to discharge a battery, hence removing fuses. My vehicle is old and no other gizmos (eg alarm) on the engine battery and that sits there happily for a couple of months.

[3rigel]

Short answer aim for middle charge.

From what I have read in the past for longevity of lithium ion batteries between 40 and 60% will give you the longest life from the battery. Car manufacturers already build in a minimum of 10 to a maximum 90% availability i believe in a lot of cases to extend life so avoid both the extremes. The only caveat is that you need to know is the actual values of the cells inside to do your own calculations to be sure.

[Nearholmer]

For the sort of cells I think you are talking about, for long term non-use, charge no higher than c85% nominal cell voltage, and don’t allow to drop lower than c40%.

I have damaged a set in one item that I have by allowing them to deep-self-discharge, so now they won’t accept anything like full charge, and won’t retain charge for anything like as long as they should. It is possible to nurse along cells damaged in this way, and cells that are simply old and very tired, by careful use of a manually-set constant current charger to get them up to the voltage that a typical regulated charger, which applies a constant voltage finishing charge, will recognise, then charge them with that, but it is a faff. Most automatically regulated chargers simply won’t recognise a deeply discharged cell.

Good quality chargers often have an automatic ‘top up’ feature, which triggers when cells self-discharge to a given level, but they are usually designed to keep cells ready for instant use, so the trigger threshold and the level that they charge to are rather high for optimum life in long term storage, after which you would expect to charge fully before using.

Different types of cells need different regimes.

[[XAP]Bob]

Since the lifetime is supposed to be maximum when they're kept about 50-60% charged, anything aimed at achieving that would be my choice if I could be bothered. Gauge how quickly they discharge & charge, then give them something like a few minutes once a month if you can remember.

Growing up in the 60s & 70s in the days when the Ever Ready man used to have to restock shops with fresh batteries once a week on a sale or return basis. I've always had a jaded view of batteries, I associate them with torches that don't work when there's a power cut, toys that stop after ten minutes, and corroded contacts. I began to warm to them with watches and calculators etc that run for a year or two, but now we're going backwards. Batteries that die if you charge them and die if you don't take me back to a time when all I wanted for Christmas was a mains transformer for my battery powered railway set.

I'm typing this on a laptop that I still regard as nearly new, but the battery has been knackered for a year, and you can't just unplug it and replace it.

What grates is that it isn't the battery that's at fault - it's the BMS.
Unfortunately it's technically possible to charge batteries without any intelligence, but it doesn't do the cells any good.
Similarly it's cheaper to let "voltage too low to operate" be the automatic off switch, but it's far better to do a controlled shutdown before then.

For cheap handheld devices this ends up being the chosen path by many manufacturers - for larger batteries (think EV or home battery) they put a little more work into the BMS and a battery can do 1000 to 1500 complete cycles with only minor degradation.

[Tim Holman]

Now that@ a question worthy of Simon Armitage:

Are you EverReady or Duracell?

Tim