maintaining batteries out of season?

[young Ed]

not sure this is right section? if not mods please move as you see fit

anyway so this winter we have just come out of i bought my self a cree led bike light a proper nice bright one for the front and it came with a 4 cell lipo battery and i bought an additional 4 cell lithium ion. all good and well but now it's a lot lighter and i don't ever really ride in the dark or when i need them what do you all do to stop them going duff over the spring/summer whilst you don't need them? do you just slap them on and turn them off just to discharge the batteries to them charge them back up again to maintain them, or do you just not use them and just plug the charger in every now and then?
or do you just accept they go duff over the year and replace them at the start or each winter?
Cheers Ed

 

[cosmicbike]

Lipo and Li ion need to be stored at about 70% charged. You can find exact storage voltage levels on the net.

 

[Shut Up Legs]

I just use mine on every ride, all year, regardless of the light conditions. This gives motorists fewer excuses to pretend they never noticed me.

 

[Wobblers]

Lipo and Li ion need to be stored at about 70% charged. You can find exact storage voltage levels on the net.

Almost! The usual recommendation is lithium ion batteries (lipo batteries are one type of lithium ion) should be stored in a cool place at 40% charged. Ideally they should be stored in the fridge at 4C (place in a plastic bag to prevent condensation reaching them) - though that may invoke protests from other fridge users! Lithium ion batteries should be charged once every 6 months - or sooner, if the instructions say so - to prevent over discharge as a result of self discharge.

Nickel metal hydride batteries should be stored charged, and not left to discharge below an open circuit voltage of 1 V. I've found it best to give them a full charge/discharge cycle once every year, even the low self discharge types such as eneloops. This prevents large crystals forming on the electrodes and also means you have an idea of the cell's capacity so can tell if it's deteriorating.

Whatever you do, do not leave either chemistry permanently on charge: at best, you'll massively reduce its life.

 

[S.Giles]

Good quality Li-ion batteries seem to be tough as old boots. I run my Cree front light off two very old Nokia (actually Sony) mobile phone batteries wired in parallel. They weren't used for a very long time before they were given to me, but worked (and continue to work) perfectly. It is said that Li-ion batteries should never be allowed to fully discharge, so I make sure mine never are.

 

[Kookas]

Good quality Li-ion batteries seem to be tough as old boots. I run my Cree front light off two very old Nokia (actually Sony) mobile phone batteries wired in parallel. They weren't used for a very long time before they were given to me, but worked (and continue to work) perfectly. It is said that Li-ion batteries should never be allowed to fully discharge, so I make sure mine never are.

It shouldn't really be allowed to get below 40% for the best battery lifespan. But you likely won't be able to fully discharge a mobile phone battery as it'll have a circuit which cuts out the power before it goes truly flat. If it did go 100% flat, it wouldn't be able to be charged again.

 

[S.Giles]

But you likely won't be able to fully discharge a mobile phone battery as it'll have a circuit which cuts out the power before it goes truly flat.

I took the Nokia units apart and discarded the protection circuits, so I don't have that safety margin! Apparently it isn't a good idea to use protected batteries for lights because they switch off suddenly leaving you in darkness (instead of slowly dimming).

 

[MickeyBlueEyes]

I charge my batteries every 10 weeks through the summer. Ay Up recommend every 12 weeks as a guide.

 

[Pale Rider]

Neither full nor empty is about the strength of it.

The battery will lose charge gradually when not in use.

In the absence of a meter, you could fully charge the battery occasionally then leave the light on for a short while.

This method also allows you to abide by the other golden rule: 'Use it or lose it.'

Lithium batteries do not like being left unused for months on end, but a few weeks is neither here nor there.