When to change RCR123s in Micra?

I recently installed a rechargeable CR123 in my Micra so I could enjoy a bit of guilt free light (saw that term on CPF and love it!!). The cells are 600mAH unprotected. They last about 45 minutes in the Micra before it starts to dim.

My understanding of RCR123's is still bit hazy despite a fair bit of reading on CPF. I assume since my cells are unprotected they can potentially be over discharged and thus wrecked.

My questions are:

1- in a fully current regulated light like the Micra, at what point should I be changing the RCR123's out? As soon as it starts to dim (this is what I currently do)? Before that even?

2 -Is it safe to run the light until it's just a feeble glow?

3 -Is the current regulation keeping the LED driven bright at the expense of the battery? Can a current regulating light pull too much juice out of the battery and wreck it?

Obviously things can't be too bad or no one would bother using RCR123's! Still, any input would be appreciated.

Get a DMM and measure voltage of your R123 cell used in Micra at say, 15 minute intervals. When it shows about 3.7 volts, within a few minutes after removing for testing, start checking every 5 minutes. When the battery reads 3.3 or 3.2 volts, stop running light. Record how long your light ran, and try to keep track of running time. I check my batteries often. The batteries have a longer run time at good voltage than you might expect, compared to primary Cr123 cells, longer than their nominal mAh ratings might indicate, expecially when used in regulated lights. I ran my 5 watt Nuwai at medium setting, pulling 750mA's, for one hour last night starting the two 650 mAh R123's out at 4.14 volts each. At end of run both cells read just under 3.7 volts, actually 3.66 volts, and light was still in full regulation.

Bill

Thanks for the reply Bullzeyebill. While I like my light I'm not that keen on filling out a timesheet when I use it /ubbthreads/images/graemlins/smile.gif I might pull the DMM out anyway just out of interest!!

I agree that I got a lot longer out of the batteries than their mAh suggested ( well, at least for their 1st charge - maybe I've killed the battery already by letting the flashlight run dim for a minute /ubbthreads/images/graemlins/smile.gif ).

Hello Gadgetnerd,

Bill gave you some good advice.

If you look at Li-Ion cells like you would the lead acid battery in your car you will get more life from your cells.

If you were to run your car battery down nearly flat every time you used your car, you would have to replace the battery often. Li-Ion cells are like that. They benefit from frequent charges.

You can monitor your usage and decide how often to charge. I have lights that I charge every Sunday morning. Since they are only partially discharged, charging only takes a few minutes. If I find myself using the light a lot, I will get an extra cell for it and swap cells half way through the week.

The analogy between lead acid and Li-Ion cells does not extend to storage. Lead acid batteries are stored at 100% full charge. Li-Ion cells suffer some loss in capacity when stored at 100% and do better when stored at around 3.8 volts (roughly 40%). While this applies to "long term" storage, I believe anything over 24 hours is long term... It is difficult and time consuming to test this, so just consider it an educated guess.

Tom

Does this same logic apply to nimhs?

I want to avoid the same thing.

I was under the impression from reading on this site, that one could discharge to 2.7 volts without damage to the r123's.
Maybe SilverFox could comment on this.

2.7 volts is the stop point but that is with a built in safety buffer. 2.5 volts is the limit you can go down to with Li-ions. If you get even slightly over the edge of 2.5 volts...you've damaged the Li-ion cell.

I think of Li-ion cells as more dramatic versions of NiMH cells. You don't take NiMH cells down to the limit and keep a safety voltage stop point of .8 volts. When you charge a 1.2 volt NiMH cell to full capacity it always reads higher than 1.2 volts off the charger, around 1.42 volts. Li-ions do the same except more extreme by ending a charge with a reading around 4.2 volts.

Remembering 2.7 volts is the stop point using Li-ion cells is like driving a car to 5 feet to the edge of the cliff. If you drop the Li-ion to 2.5 volts it would be equal to putting your car wheels on the edge of the cliff. One little slip and your...gone! /ubbthreads/images/graemlins/frown.gif

Hello Pajamas,

No.

NiMh cells can build up crystals during normal use that are erased by a discharge/charge cycle. Individual cells can be discharged to 0.8 volts (0.7 volts under heavy load) without doing damage to the cell. A battery (several cells grouped together) can safely discharged to 1.0 volts per cell.

The reason for the higher voltage limit on a battery pack is to minimize the possibility of cell reversal due to pack imbalance.

An occasional slow charge (0.1 C) for 14 hours will re-balance the battery pack for peak performance.

In summary, NiMh cells will perform OK when frequently topped up, but will perform better when cycled. If you have a NiMh battery pack, keep the discharge voltage above 1.0 volts per cell during discharge and occasionally do a 0.1 C slow charge to re-balance the pack.

Non of this applies to Li-Ion cells or battery packs.

Tom

Hello Anglepoise,

In an effort to get more capacity from Li-Ion cells, the chemical mix is changing. Li-Ion Polymer cells are evolving faster than Li-Ion cells and some early testing has revealed that discharging below 3.0 volts UNDER LOAD can damage the cells. This works out to about 3.5-3.7 volts after the load has been removed and the cell is allowed to rest for a few minutes.

The difficulty with a more volatile mix (which gives greater capacity) is that it is unstable at both high and low voltage extremes. When you charge to 4.2 volts or discharge to 2.8 volts (resting) you can suffer some loss in capacity if the cell remains in that condition for any length of time.

Let me balance this with the protection circuits used in Pila cells, cell phones, video cameras, lap top computers, and PDA's. A typical protection circuit used in the Pila cell will limit charge voltage to 4.30 volts (+- 0.05 volts), and limit the discharge to 2.3 volts (+- 0.1 volts). This protection is designed to minimize damage to the cell and give adequate cycles, while protecting it against overcharge which can result in "rapid venting with flame."

Looking at the extremes, you could go to 4.35 volts and 2.2 volts.

I have done some testing at these extremes and seen little short term degradation. I do not recommend them, but an occasional excursion will not immediately kill the cell.

The Pila cell is designed to be charged in a 4.6 volt 1.5 amp charger. At this load, the protection circuit kicks in at 4.3 volts, but the resting voltage ends up at around 4.185-4.195 volts. The same thing happens during discharge. Pila cells are used in lights that draw somewhere near 1.5 amps. At that load the protection circuit kicks in at 2.3 volts, but the cell's resting voltage is closer to 3.5 volts.

Your question was can you discharge to 2.7 volts without damage? The answer is a bit complicated (sorry for being long winded) and it depends upon the load. In a light that is only drawing 200 mA, the answer would be no (in my opinion the low voltage cut off should be 3.0 volts or above for low current draws). In a light that is drawing 1500 mA, the answer would be yes.

Tom

Thanks Silverfox.
My main concern is one of safety. The fact that I might get longer or shorter life out of my Li Ion r1213 cells does not concern me too much as there will be better technologies continually appearing. But I do not want to explode something and start a fire.

Like others, new to Li-Ion rechargeables, I am going very slowly and sticking to single cells. My one re chargeable is an Aleph, with a Wiz 2,750 ma bias Light engine that cuts off when the single cell discharges to 2.7 volts. I then immediately re charge and so far I have been delighted in the whole process.

Tom,

Thanks for the info. Unfortunately I have no way of measuring the voltage on my nimhs. Currently using them in FMs 9AA holder in a Mag85. I was trying to find out if I can just let the light dim enough before recharging or if I should periodically cycle them even though the light still shines brightly.

That discharge to 2.7 volts for unprotected R1233's means discharged under load to 2.7 volts. So, that might relate to say, 3.2 volts when cell is removed from light. Good guide is to not go below 3.2-3.4 volts for a rested cell.

Bill

This LI ion stuff is getting to be a pain.in my KL-1 it might dim just a little, but then off it goes. when i check the batt Voltage it's 00.2(one batt goes to oo.o sometimes) so I guess i have damaged my Batt's. (batt station unit's if that makes a diff)

But I have not found a reduction in runtime or charging after the few cycles i have done. (10 maybe)

I am not gonna carry a MM with me and test every five min's,
so I will just factor in new LI ion's once these start to not work. I figure if they work fine for 15-20 cycles am still money ahead.
And it seem's to be every Li ion, that has one problem or another, so i don't think it's a just quality or protection
issue, or something I can "buy" my way out of.

All that said,,, I do like using them and will till i find
it to be problematic, or a hazard, or not worth it, Because it's not been that i am having any problem's, everything is fine so far. it what I keep reading here that make's me suspect of the technology, not anything that's happened.VDG

voodoo...what charger are you using? It could be the charger that is slowing frying the insides of your Li-ion cells.

The reason I ask is because I have a charger that I put away because it was just overcharging my cells enough to make me worry. The peak voltage coming out of the suspect charger was 4.35 volts. A voltage that high would slowly cook Li-ion cells. I only got about 15 charges out of a cell because of the ambitious charger. So I put the charger away and use my charger from BatteryStation that makes my cell voltage at 4.17...ahh...just right for me.

I haven't had any problems with any other Li-ion cells and I'll tell you I've been seen a lot of them.

Voodoogreg are you using protected cells? From what I've read they'll actually read 0.00 or close to it once their protection cuts in - but then they should charge up just fine.


[ QUOTE ]

This LI ion stuff is getting to be a pain.in my KL-1 it might dim just a little, but then off it goes. when i check the batt Voltage it's 00.2(one batt goes to oo.o sometimes) so I guess i have damaged my Batt's. (batt station unit's if that makes a diff)
But I have not found a reduction in runtime or charging after the few cycles i have done. (10 maybe)
I am not gonna carry a MM with me and test every five min's,
so I will just factor in new LI ion's once these start to not work. I figure if they work fine for 15-20 cycles am still money ahead.
And it seem's to be every Li ion, that has one problem or another, so i don't think it's a just quality or protection
issue, or something I can "buy" my way out of.

[/ QUOTE ]

These RCR123s sure are a lot of hard work!

Bullzeyebill and Silverfoxes advice is absolutely correct (thanks guys!) but is a bit too involved for my personal level of laziness.

Provided they don't explode and wreck my $100 flashlight I can live with killing a $20 battery after 10 charges!

Thanks guy's,, it's two batt station charger's. i must not see quick enough for early warning sign's, in my LSH-P it will flicker, but on the KL-1's it just goes out. So two different charger's and 4 R123's so i think it's just me
not noticing the dimming.
None the less as I said, i haven't noticed an adverse effect
and if i do i guess i will get a couple more. Who know's
maybe my little auto ranging MM might be reading something different when i test them depleted. VDG

[ QUOTE ]
gadgetnerd said:
Voodoogreg are you using protected cells? From what I've read they'll actually read 0.00 or close to it once their protection cuts in - but then they should charge up just fine.


[ QUOTE ]

This LI ion stuff is getting to be a pain.in my KL-1 it might dim just a little, but then off it goes. when i check the batt Voltage it's 00.2(one batt goes to oo.o sometimes) so I guess i have damaged my Batt's. (batt station unit's if that makes a diff)
But I have not found a reduction in runtime or charging after the few cycles i have done. (10 maybe)
I am not gonna carry a MM with me and test every five min's,
so I will just factor in new LI ion's once these start to not work. I figure if they work fine for 15-20 cycles am still money ahead.
And it seem's to be every Li ion, that has one problem or another, so i don't think it's a just quality or protection
issue, or something I can "buy" my way out of.

[/ QUOTE ]

These RCR123s sure are a lot of hard work!

Bullzeyebill and Silverfoxes advice is absolutely correct (thanks guys!) but is a bit too involved for my personal level of laziness.

Provided they don't explode and wreck my $100 flashlight I can live with killing a $20 battery after 10 charges!

[/ QUOTE ]
Since batt station has over DC protection, then sound's like everything is fine. VDG

From what was reported in other threads these cells seem to have some sort of short-circuit protection which also does duty as low voltage cutoff protection then - I have none of these (yet) but I guess you are fine with your KL1 which should be killing unprotected cells as the circuit designed for 2xAA/1x123 to 3x123 will suck cells to below 2V levels.

Having the cells read 0.0V before going back into the charger seems to be the typical behaviour when protection kicks in but the jury is still out on at what voltage point that protection kicks in - one would need to run such a cell in some monitored environment to see when the LVC really kicks in - I should have some of these cells soon and will do some testing. BTW if your cell would be **really** discharged to 0.0V for a couple of cycles I guess they would be pretty much dead already ...

Klaus

[ QUOTE ]
Klaus said:
- I should have some of these cells soon and will do some testing. BTW if your cell would be **really** discharged to 0.0V for a couple of cycles I guess they would be pretty much dead already ...

Klaus

[/ QUOTE ]

That's what i thought too Klaus. but they charge up to green light the same amount of time, and run as long as they did the first time, (maybe a little longer)
so i am pretty sold on batt station stuff for now anyway. Just wish I could run a E1e with a Li ion other then that i am happy with them. VDG

Hello Pajamas,

In your Mag85 run the light until you notice it dimming, then charge the batteries back up.

Tom