Gatsby
Enlightened
If you have a protected cell, is it better to run it to shutoff and recharge, or try to "top off" batteries when they start to visibly dim?
Protected Cells - run to shutoff or top off?
- Thread starter Gatsby
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SilverFox
Flashaholic
Hello Gatsby,
Top them off...
Tom
Top them off...
Tom
DM51
Flashaholic
It is much better to charge them before they reach the low-voltage cut-off. You don't have to wait for the light to dim, either. You can top them up as often as you like - this is better for them.
Don't let them go below 3.5V resting. For even longer life, don't charge them to the full 4.2V. Charging to 4.1V is ~90%, and this will more than double their cycle life.
There is an interesting recent report that 4.1V is the maximum that should be used outside in cold weather.
EDIT: Beaten to it by a much more succinct post, which really says all you need to know!
Don't let them go below 3.5V resting. For even longer life, don't charge them to the full 4.2V. Charging to 4.1V is ~90%, and this will more than double their cycle life.
There is an interesting recent report that 4.1V is the maximum that should be used outside in cold weather.
EDIT: Beaten to it by a much more succinct post, which really says all you need to know!
Last edited:
mdocod
Flashaholic
it's why I love li-ion, no messing with cycling to keep performance up, no self discharge, and I can top off whenever I want to.
winston
Enlightened
Silverfox, Mdocod, and DM51 = Triumverate of rechargable lithium knowledge
Li-ionumverate, Li-iumverate, I'll keep working on it.
-Winston
DM51
Flashaholic
Lol, not me, I learned what I know from the other 2 (and I'm still learning).
Bushman5
Enlightened
- Joined
- Sep 8, 2007
- Messages
- 977
how do you know when they have reached 3.5V? do i have to remove the batts from my lights every 5 minutes and check them with a multimeter? 
whats the runtime of a RCR123 in a P1D-CE, before i have to pull the batts? 5 minutes, 10?
seriously considering ditching this RCR123 format and going back to USER FRIENDLY nimh AA's or even nicads......
whats the runtime of a RCR123 in a P1D-CE, before i have to pull the batts? 5 minutes, 10?
seriously considering ditching this RCR123 format and going back to USER FRIENDLY nimh AA's or even nicads......
SilverFox
Flashaholic
Hello Bushman,
You need to do a couple of tests...
The first test is to start with a fully charged cell and turn the light on to a level that you use the most and time how long it takes to start to dim. At that point, remove the cell, let it rest for 15 minutes, then measure the voltage.
This first test will give you an idea of how far the light drains the battery, and you now have an idea of constant on runtime.
The next test is a little more involved.
It is very difficult to keep track of "on" time, so I usually recommend that you use your light, "normally," for a week. At the end of the week remove the battery and measure the voltage. If you do a search, you should be able to come up with Li-Ion resting voltage verses percentage of charge, and from that you will have an idea of how much capacity you used during the week.
Armed with the results of these two tests, you now can set up a charging schedule that is easy on your cells, and insures that you have your light always ready to go with enough charge to meet your needs.
For example: Let's say you get 1 hour of constant on runtime. When you remove the battery and let it rest, it comes up to around 3.0 volts. That is a bit of a deep discharge, but it is not the end of the world. If you need to run your light all the way to dim, you can do it, but don't wait an extended period of time to get the battery on the charger afterward. Over discharging damage comes from both over discharge, and remaining in an over discharged state for an extended period of time (like overnight). Of the two, remaining in an over discharged state does more damage.
Now you understand how your light performs under constant use.
Let's say that you check the voltage of your cell after a week of "normal" use and find that the voltage is 3.85 volts. If you started at 4.2 volts, this means that you used around 40% of your cells capacity during the week. At this point, you can decide to recharge, or not. If you anticipate another "normal" week of use, you can extend your recharge time to every two weeks. At this rate you will end up with a cell that is left with around 20% of its capacity in reserve after two weeks of use. This is a reasonable safety factor.
A lot of Li-Ion life cycle testing is done with 80% discharges, so you are right in there with your cell.
Now, if you decide to charge after one week, you can expect extended cycle life. Shallow discharges lead to extended cycle life.
By the way, this same method is used to determine when to recharge NiMh and NiCd batteries. However, you also have to factor in the cells self discharge rate. NiMh and NiCd cells are also affected by over discharge, but the damage is less violent upon re-charging... Also, NiCd cells tend to handle over discharge much better than NiMh cells.
If your concern is with over discharge damage, by all means move to NiCd cells. Then your concern will change to self discharge rate, and poor runtime...
Tom
You need to do a couple of tests...
The first test is to start with a fully charged cell and turn the light on to a level that you use the most and time how long it takes to start to dim. At that point, remove the cell, let it rest for 15 minutes, then measure the voltage.
This first test will give you an idea of how far the light drains the battery, and you now have an idea of constant on runtime.
The next test is a little more involved.
It is very difficult to keep track of "on" time, so I usually recommend that you use your light, "normally," for a week. At the end of the week remove the battery and measure the voltage. If you do a search, you should be able to come up with Li-Ion resting voltage verses percentage of charge, and from that you will have an idea of how much capacity you used during the week.
Armed with the results of these two tests, you now can set up a charging schedule that is easy on your cells, and insures that you have your light always ready to go with enough charge to meet your needs.
For example: Let's say you get 1 hour of constant on runtime. When you remove the battery and let it rest, it comes up to around 3.0 volts. That is a bit of a deep discharge, but it is not the end of the world. If you need to run your light all the way to dim, you can do it, but don't wait an extended period of time to get the battery on the charger afterward. Over discharging damage comes from both over discharge, and remaining in an over discharged state for an extended period of time (like overnight). Of the two, remaining in an over discharged state does more damage.
Now you understand how your light performs under constant use.
Let's say that you check the voltage of your cell after a week of "normal" use and find that the voltage is 3.85 volts. If you started at 4.2 volts, this means that you used around 40% of your cells capacity during the week. At this point, you can decide to recharge, or not. If you anticipate another "normal" week of use, you can extend your recharge time to every two weeks. At this rate you will end up with a cell that is left with around 20% of its capacity in reserve after two weeks of use. This is a reasonable safety factor.
A lot of Li-Ion life cycle testing is done with 80% discharges, so you are right in there with your cell.
Now, if you decide to charge after one week, you can expect extended cycle life. Shallow discharges lead to extended cycle life.
By the way, this same method is used to determine when to recharge NiMh and NiCd batteries. However, you also have to factor in the cells self discharge rate. NiMh and NiCd cells are also affected by over discharge, but the damage is less violent upon re-charging... Also, NiCd cells tend to handle over discharge much better than NiMh cells.
If your concern is with over discharge damage, by all means move to NiCd cells. Then your concern will change to self discharge rate, and poor runtime...
Tom
mdocod
Flashaholic
Actually, it aint me either, All roads lead to Silverfox, I'm just attempting to accurately regurgitate his teachings around here.. lol...
winston
Enlightened
So it's a Li-isosceles Li-iumverate. I never specifically Li-indicated it was Li-iquilateral. Spelling like this is getting Li-irritating.
-Winston
Illum
Flashaholic
running it to shutoff before recharging constitutes as deep cycling...and I heard this kills the cell rather quickly
DSD charges my AWs to 4.2V then I run it down to 3V before I recharge it...
and for storage I was informed my AW via PM that its best to store them at 3.8V and the IC's thermal threshold is 60C
DSD charges my AWs to 4.2V then I run it down to 3V before I recharge it...
and for storage I was informed my AW via PM that its best to store them at 3.8V and the IC's thermal threshold is 60C
