Not sure if this will sound ridiculous, but I have been wanting to check the actual capacities of our local AA/AAA and D primary batteries.
My BT-3100 has a discharge function. Can I safely discharge primary batteries in this charger?
I’m not sure but in the C3100 V2.2 when I test with Li-ion it first fully charges the batteries then performs the discharge, and then a full charge after that.
If you just choose the Opus’ Discharge mode, (not the Test), it will just discharge at the rate you choose, then will stop at .9V (2.9V with li-Ion) with no other additional action taken by the charger.
Welcome back strongest2004 my friend, glad to see you back here in BLF. I have seen somewhere someone a thread asking about discharging primaries but can’t find it at the moment.
Sure, the charger won’t care what it’s discharging as long as you set it up right.
The main difference between primaries and rechargeables is rechargeables are sealed cells. This prevents venting during the charge process. Discharging the cells is actually what they are designed for so it will make little difference to the cell how it is discharged (given it’s not shorted etc…) for either type. If you are game you can actually charge primaries. Just do it on a very low charge rate. The lower the better. As I said before primaries are unsealed so a higher charge rate will heat them and cause them to vent, this could be said about any battery. They just have different rates of safe charge.
I know you didn’t need to know this I just couldn’t help putting in my 2 cents. 
Completely different chemistry. Yes, you can charge primaries but every time you do they get weaker and more likely to leak. They are most decidedly NOT designed to be recharged, no matter how many companies that put out those kind of chargers try to convince you otherwise.
Yes they get weaker because they are unsealed therefore let out a small amount of has anyway. I wasn’t referencing or even aware that charger manufacturers are saying these kinda things??
Have you charged primaries before? Just curious of the results.
Primary cell Wiki
[A primary cell is a battery that is designed to be used once and discarded, and not recharged with electricity and reused like a secondary cell (rechargeable battery). In general, the electrochemical reaction occurring in the cell is not reversible, rendering the cell unrechargeable. As a primary cell is used, chemical reactions in the battery use up the chemicals that generate the power; when they are gone, the battery stops producing electricity and is useless.]
Yes I have one and I’ve tried it….a bunch. If you ONLY discharge them a little and then immediately recharge them, you can keep them going for awhile. Let them go too far and they won’t recharge, or if they do the charge simply doesn’t hold.
But, that’s kinda dumb because a quality rechargeable would have worked better with less hassle in the same arrangement most of the time. Why bother?
The real misfortune is leaking. The more often you do recharge them, the larger the voltage cycle, and the longer them time the more they leak. Having electrics destroyed for trying to save a couple bucks is simply not rewarding penny pinching.
Oddly it does seem to be useful for trying to recover old abused NiXX cells. OTOH, with (some) cells getting to be of much higher quality I’m not much into saving old NiXX junk anymore.
You’re right, there are better ways. Why bother? because it has got me out of a pickle as a temporary measure. I’m not recommending anyone and everyone ‘do this’. As I said in my original post “if you are game”. People don’t have to do it if they are not comfortable with the idea. You have tried it, so have I. For others it might just be interesting info. I thought it somewhat relevant to the topic.
Indeed, why bother? Curiosity mainly. Drive by cheapness, this is Budget LF after all. :bigsmile: And it could get you out of some bind, not knowing what kind of limitations you have in OZ. That part, I agree with entirely.
Thanks everyone for your replies/inputs.
Where I am from, primary batteries are so cheap compared to alkalines and lithiums that it’s hard for me to disregard them as backup power sources. But it looks like there dangers far outweigh the possible benefits/info gained. Will just manage the ratio of rechargeable (eneloops and 18650s) vs primary batteries.
Bro Tatasal.
Thanks for the warm welcome. I’m back after a long timeout.
Powerfocus, Opus. (same product, different label?)
BT-C3100, BC3100 (Exactly same model?)
Knowledge is power (pun partially intended)
There are times and places where it makes sense to “recharge” a primary, and there are times and places where it does not. This is where judgement comes in, but it is good to know we have options.
Just wondering, using Discharge function on primary cells (for testing) on the SkyRC MC3000 should be safe, since the “Discharge” function should not be doing any other stuff like trickle charging, right?