Hi-Just got an Acebeam K40M+batts+charger from HK.Ordered on 11/4+received light 11/14,batts+charger 11/17.
Question-Batteries are 18650 Keeppower 3400 MAH+charger is Xtar VP4.I can choose between .25 amp or .50 amp on the charger.I assume .50 is faster(twice as fast?).Is there a reason,safety or battery longevity etc to charge at .25 amp rather than .50 amp?As always thanks for your help.
Keeppower 3400 is panasonic nrc18650b
Datasheet list standard charge current as 1625mA (“0.5C” half of its min. rated capacity, 3250mAh) so 0.5amp (500mA) is already slow and easy for this battery. No need to do 0.25A.
Thanks for the info!
Hello-Any idea of charging time for 4 18650 batts on this charger?Is it ok to half charge batteries and use them?I assume it’s ok to charge before complete discharge.Thanks
You don’t want to discharge them past 2.8V. It’s fine to use them before they are fully charged. If you’re using them in the Acebeam you want to make sure they are all the same voltage. Do you have a multimeter?
Thanks.I don’t have a multimeter.Do I need to get one?I’ve got 2 other “hobbies”so flashlight obsession should help me go broke faster.
Is it indeed ok to recharge the batteries before they are mostly discharged?
You don’t have to spend lots on a multimeter (Uni-T make some nice budget meters). It’s fine to charge li-ion cells before they are fully discharged.
Like First Aid skills, battery skills can also get rusty with time. So in that regard, I can’t recall, was it Li-Ion, or NiMh, (or perhaps both?) that it was better to recharge at the first opportunity rather than running lower? So to put into real life terms, if you went out to walk the dog and used your Li-Ion 18650 cell for only 20 minutes and it only went down to 4V from 4.2V, it would still be better to put it in the charger after every walk at 4V rather than after a week of walks when it might be at 3.2V? I recall this was true of some chemistry, but can’t remember which.
for taking the time to help.
I think this is true of Li-ion. At least, I remember reading somewhere (probably Battery University) that it is suited to the way we tend to use and charge phones. But also that fully discharging and charging to full capacity each time reduces the life, so it’s better to keep topping up.
With Ni-Mh I think it is better to discharge fully then charge because top-up charging can be considered a charge cycle, thus wasteful. There is also the memory effect, so more reason to fully discharge before recharging.
Thanks Chloe,
Sounds like what I also may have read at the same place. I thought that only NiCad had the memory effect, and I seem to recall that NiMh are also better topped up and NiCad were better run down due to the memory effect. Maybe Li-Ion and NiMh are the same in those respects. Time to go back to ‘University’ I guess…
Li-Ion slowly degrade chemically. They have a limited lifetime, even if not used. If they are stored with 40% charge and in a dry and cool place they degrade significantly slower. So I would assume that it would be better to use the battery for a few times before charging it, so the charge is closer to 40% at least some of the time, compared to charging it every time. I would also assume that the difference would be slight. However it is not good to store the battery discharged either. If the battery is stored with a low voltage (NCR < 2.5 volts, Others < 3.0 volts(?) ) then the battery may soon be permanently damaged.
Unless a NiMh is fully discharged before charged, some chargers may have problem detecting that it is fully charged. Then the charger may overcharge the battery before ending the charge cycle. And stop the charge using rising voltage or temperature cues rather than how the resistance/voltage change as the battery becomes full. That may reduce the life of a NiMh.
Ni-Cd batteries could develop "memory" unless you fully discharged them before charging again. NiMh and Li-Ion don't have that problem, but after a long time without use a NiMh may gain capacity if it is charged and discharged a few times.
Also I tend to rotate all my NiMh to ensure they get used at least a few times each year.
But I do the opposite with my Li-Ion. I rotate as few as possible as much as possible and store spares cool and dry at a voltage of 3.6-3.7. That is about 40% charge. When you get new batteries, that is the voltage they use to have. To store well before they are sold.
As a basic rule of thumb, there is no harm in charging and discharging lithium ion batteries within their normal operating parameters whenever it is most convenient to do so. No need to run them down to 3v before charging, and no need to wait until they are fully charged before using them.
You can give up capacity for lifetime by limiting the charging and discharging voltages further, but its easy to go overboard with that stuff. Does the battery serve you, or do you serve the battery?
Interestingly, slow charging can actually shorten battery life with some chemistries under some conditions, but I don’t think that is an issue for the batteries we are using, under the conditions we are charging them.
That’s very good!
I thought that when we got rid of the chains of nicads that slavery was over.