Do my lights have over discharge protection?

filedog · May 22, 2015, 3:01pm

Just got a couple new 18650 lights, and I wonder if they have over discharge protection. Neither one lists it, and I've read reviews, but haven't found an answer.

One is a Solarforce P60 drop in: http://www.solarforceflashlight-sales.com/product_detail.php?t=RB&s=53&id=692

and the other is the Convoy M1 https://www.fasttech.com/products/1601/10002364/1212404

Is it just assumed that most modern lights have this protection? The M1 apparently won't fit my protected Panny NCR18650B cells,

so I got these: http://www.mtnelectronics.com/index.php?route=product/product&path=59_88&product_id=191 which are unprotected.

My charger is an XTAR VP2, so it's capable of charging them, and safe as far as overcharging, so my only concern with the unprotected cells if they over discharge.

hank · May 22, 2015, 10:00pm

There are two kinds of low voltage indication to look for — either power off, or some kind of blink or flicker ‘warning’

I assume neither one is there and use protected cells.

You can test for it with an unprotected cell that’s already at low charge — put it in for a few minutes and see if the light keeps draining it, check the voltage, try again, and if it’s getting down to the safe level assume there’s no protection in the circuit board.

One tricky way to check — annoyingly complicated — is to buy a couple of “2/3A” NiMH cells
https://www.google.com/search?q=2%2F3A+NiMH

Two of those, with a 1/4” magnet between them gives you 2.4v more or less
(put the magnet in one of those nylon spacer/fat washer things to keep it from slipping sidewise and shorting to the case)
drop into a 18650 flashlight.
You have to check with a voltmeter to see what you’re actually getting; you can run NiMH down without harming the cells, to see how low the voltage can go before the light quits lighting up.

I’ll test some of mine and post by editing this response.

EDIT — of course, anyone with a DC voltage supply and a rheostat can do a better test.
hmmmm … http://www.instructables.com/id/Easy-variable-voltage-power-supply/

hank · May 22, 2015, 9:40pm

(tell us what indication you have? does it blink, or step down, or actually go dark? And at what voltage, if — I dunno how much Li-ions sag at low voltage, will checking the battery at that point give a reasonable guess where the driver cutoff is set, anyone know?)

Also note —- inexpensive lights often have, um, some variations in the driver used. Anything that would help identify the actual driver (maybe a picture of it in the pill, at least) could help.

I know for example the ZeusRays have had a variety of different drivers in them, over time.

filedog · May 22, 2015, 11:04pm

Ok, that's great info on how to test, I can do that.

Yes, it would be great to have a list, I'm kind of surprised that modern lights leave out that info..... On your Acebeam, how do you know it has that feature?

I have no indication, yet, just got 'em, need to use unprotected cells in one, wanting to exercise caution with them. I know I can pull the cells and text voltage,

but with all the features on these lights, I would expect over discharge protection would be more common. The Solarforce drop in doesn't have those parts visible.

wolfdog1226 · May 22, 2015, 11:09pm

^ Nice pooch!! Looks like Capo’s cousin! :bigsmile:

filedog · May 22, 2015, 11:51pm

Yeah, 2.5 is low, right? Since you've tested, do most of your lights have some similar protection?

hank · May 23, 2015, 12:53am

I found a thoughtful discussion of this over at CPF, in particular this response from user VidPro back in 2009:

Recommended reading; brief excerpt follows:

any high drain devices will slam a smaller battery so hard the voltage will tank when it reaches this location, so the protection kicks in earlier.
a Very slow drain on same said battery (like say low PWM rates or direct drive slowdowns) by the time the battery reaches any protection level of 2.5 the battery will be discharged MUCH further.
so your underLOAD voltage will depend on the battery and the load, and all the HUMAN has to remember is “Before the cells capacity is gone” so to speak.
EX: a 5mm white led put on a li-ion and allowed to droop to nothing will have completly drained the cell (~2.3-2.4v) with no bounceback.
a 1c load from a Boosting driver pushing the battery current up as the battery is depleated in voltage will reach a low voltage point much faster.
if your talking the RESTING voltage, then ALL of those would be concidered to low and in dire need of recharging.
To put ONE number on a the Voltage location for stopping a load, would not take Actual remaining capacity into account.
a perfect stop alogrythm in, would be at a Percentage of actual remaining capacity instead (that being neer impossible).
i point that out only because people want some NUMBER a definable location, and a specific voltage number is not what is needed, plate seed, or chemicals in place or whatever they want to call it is what is needed, and no specific voltage number can define that for every occurance.
if there was a visual voltage representation it is when the voltage starts to take a dive, aka some parts of the chemical conversion processes are completed.
so in general flashlight use with protected cells, when your draining the cell rapidly the average 2.4 2.5 2.7v protection will work ok, but if your doing the slow low drain thing, then YOU Certannly NEED to stop before you drain the thing so far it cant re-charge fully later.
if your making a driver or protection with a cutoff built in, then more than ONE voltage cut-off point could be usefull, but then tiny little brains only have so many lines of code , leaving big human brains available to compensate
if you had more than one voltage point in a driver cut-off , with normal discharge batts ,it would be:
higher when the load is smaller (like cutting off at 3.2v or higher even)
Lower when the load is larger (like cutting off at 2.5v when load is 1c)
so your devices cuts off when it reaches the “about empty” location.

That guy’s a lot smarter about this stuff than I am.

———> Conclusion: if two NiMH cells in series make it light up, it’s got NO low voltage protection.

xv-750 · May 23, 2015, 1:05am

When battery voltage drops the Nanjg 105C driver in that light switches to low mode and flashes to show low voltage.

filedog · May 23, 2015, 1:51pm

hank:

I found a thoughtful discussion of this over at CPF, in particular this response from user VidPro back in 2009: li-ion discharge limit - 2.5v/2.7v/2.8v/3v??? | Candle Power Flashlight Forum Recommended reading; brief excerpt follows:

any high drain devices will slam a smaller battery so hard the voltage will tank when it reaches this location, so the protection kicks in earlier. a Very slow drain on same said battery (like say low PWM rates or direct drive slowdowns) by the time the battery reaches any protection level of 2.5 the battery will be discharged MUCH further. so your underLOAD voltage will depend on the battery and the load, and all the HUMAN has to remember is “Before the cells capacity is gone” so to speak. EX: a 5mm white led put on a li-ion and allowed to droop to nothing will have completly drained the cell (~2.3-2.4v) with no bounceback. a 1c load from a Boosting driver pushing the battery current up as the battery is depleated in voltage will reach a low voltage point much faster. if your talking the RESTING voltage, then ALL of those would be concidered to low and in dire need of recharging. To put ONE number on a the Voltage location for stopping a load, would not take Actual remaining capacity into account. a perfect stop alogrythm in, would be at a Percentage of actual remaining capacity instead (that being neer impossible). i point that out only because people want some NUMBER a definable location, and a specific voltage number is not what is needed, plate seed, or chemicals in place or whatever they want to call it is what is needed, and no specific voltage number can define that for every occurance. if there was a visual voltage representation it is when the voltage starts to take a dive, aka some parts of the chemical conversion processes are completed. so in general flashlight use with protected cells, when your draining the cell rapidly the average 2.4 2.5 2.7v protection will work ok, but if your doing the slow low drain thing, then YOU Certannly NEED to stop before you drain the thing so far it cant re-charge fully later. if your making a driver or protection with a cutoff built in, then more than ONE voltage cut-off point could be usefull, but then tiny little brains only have so many lines of code , leaving big human brains available to compensate if you had more than one voltage point in a driver cut-off , with normal discharge batts ,it would be: higher when the load is smaller (like cutting off at 3.2v or higher even) Lower when the load is larger (like cutting off at 2.5v when load is 1c) so your devices cuts off when it reaches the “about empty” location.

That guy’s a lot smarter about this stuff than I am. ------> Conclusion: if two NiMH cells in series make it light up, it’s got NO low voltage protection.

Excellent info! The Convoy isn't here yet, but I did test the Solarforce, and it didn't light, thanks!

Ok, I will run the test on the Convoy when I get it, but it looks like both have protection, thanks!