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How Do You Prevent Over Discharge?

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I know there are protected batteries, but I heard that over discharging ruins batteries. So how do you know when to replace your batteries so they don't over discharge?

Thanks
 





You must never discharge them under 2.7V (li-ion cells, ofcourse), or they got damaged (same for overcharge, when they go over 4.2V

Or, if you want to try, you can add a protection circuit (but you need to check if this worth the expense) ..... DX have some of them in different sizes, for different batteries ..... like this and this, as example (there are others too) .....
 
If you know the capacity of the battery and the loading current of the charger you can calculate the charging time. You have to add some time to the charging time to compensate the lost in energy transfer. Nothing is 100% efficient you know.

Example : battery capacity is 2600mAh and charging current is 600mAh. Charging time is 5 hours if the battery is almost empty.
 
Careful with the protected cells though, the pcb on the bottom adds a couple of mm and some hosts won't accept them.
I prefer the protected cells but also, as I'm sure you already know, the flexdrive has a built in shutoff at 2V.
This is well into the "damaging voltage" range of the li-ions but it is better than waiting until the laser goes dim ^_^
I actually JUST had a flashlight that I had forgotten to turn off go dead. When I remembered it, the light was just about off. I threw it into the charger and threw that into an old cast iron pot with a heavy lid. It charged up fine but It was more of an experiment than anything, I might have just gotten lucky with that one ;)
 
Mostly if the battery is dead I cut the pcb away and it is live again. With a bonus the battery will have higher discharge rate than before. The pcb prevents a high discharge current. You have to know anytime that this battery is no longer protected anymore. Use it with caution.
 
Sorry if I didnt word it right, I meant how do you know when to pull them out of the laser :)
 
With non protected lithium cells you can use a rc hobby charge and pump some current into them, in NiMH mode to get enough voltage in them so the charger recognizes them as a Lithium cell. It's actually a really dangerous thing to do. I work at a hobby store and do it from time to time on various lithium batteries. I have fixed around 20 or so and I have had 1 vent on me. We always use a fire resistant bag with charging Lithium batteries at the store to be safe called a li-po sac
 
well you can just keep a mental note of run time vs mah. or pull out occasionally and check voltage.
in my set up i have a flex drive v5 with 1- 18650 and it starts to flash and go into single mode with my 445. Lithium ions like to be kept full. so just charge it when ever to always keep it topped off. well if you have a decent charger that will auto shut off.

michael
 
Without pulling the batteries and checking them with a DMM I don't think there is any way (other than figuring out the math and timing your laser usage ^_^).
I just sacrifice the longevity of the lipos and charge them whenever I feel like it.
Keeping them in the fridge helps but they die a LOT faster if they are charged up all the time.
 
chipdouglas said:
well you can just keep a mental note of run time vs mah.
Click to expand...

In theory thats a good idea, but you have to assume the batteries are up to spec, and not degraded yet. If something labeled 1000 mAh actually only provides 600 mAh, cutting it off after draining 800 mAh won't do you much good. You need a very big margin of error this way.

I'd recomend getting protected cells, and choosing hosts that allow the additional length.
 
Ignis Fatuus said:
My Microboost flashes. Thankfully.
Click to expand...
Jerry told me that on the driver that is in my 445 that once it drops down to a certain point that it just shuts down since it is not getting the required voltage. It uses 2 16340's. The first time it shut down I thought my laser died and I pmed jerry and that's when he gave that info.
 
I am using a Micro BoostDrive, with 2900mAh AW 18650s, and when they start to die, the diode gues super dim, then bright, then dam, and it slowly flashes faster. I am guessing the protection circut on battery is kicking in.

My question arose when I seen DTR using unprotected all the time, and Larry's 18650s. I would like to get some, but I am nervous I would accidentally over discharge. What would be sick is if there was some way on drivers you could change the cutoff voltage.
Maybe in v6? Probably not, but wishful thinking:) Changing in values fitting for the major voltages of batteries (Their drop-offs). It would only be two settings. Shouldn't take up a ton of space. Lets talk Lava into it :)
 
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