Go Back   Steve's Digicams Forums > Digicam Help > Batteries or Power Packs

Reply
 
Thread Tools Search this Thread
Old Apr 2, 2007, 11:28 AM   #1
Junior Member
 
Join Date: Mar 2007
Posts: 15
Default

<deleted>

Last edited by Keoeeit; Jul 26, 2010 at 9:19 PM. Reason: Removing my participation from your forums.
Keoeeit is offline   Reply With Quote
Sponsored Links
Old Apr 13, 2007, 10:07 AM   #2
Junior Member
 
Join Date: Nov 2006
Posts: 8
Default

single cell dead short is possible as long as it's underload.

If you want to fully discharge your batteries while you store them go out and get a 1Kohm resistor and wire them to a single cell holder for each cell. This ensures no damage to the battery.

The only side effect is that chargers might have a hard time recharging the batteries if they are left low for too long.

Recently with the C9000 I ditched this idea now I just put the C9000 on discharge mode when I'm getting ready to prepare batteries for storage, maha's internal curcuit stops the discharge once the batts reach 1.1v
vortex05 is offline   Reply With Quote
Old Apr 13, 2007, 1:22 PM   #3
Senior Member
 
Join Date: Jul 2005
Posts: 358
Default

Hello Keoeeit,

What you are doing is going for a 100% depth of discharge. That is an important step in keeping NiMh and NiCd cells in good shape, however, it does not need to be done every discharge. If you do that every time, you will end up with fewer total cycles. The complete discharge us usually done once in 20 - 50 charge/discharge cycles.

The same goes for Li-Ion. Li-Ion cells work best and last the longest if you only use 80% of their capacity. A full discharge every time will have you replacing the battery in around 200-300 charge/discharge cycles. If you limit the use to 80%, you can usually get 400 - 600 cycles.

The other thing that works against the life of a Li-Ion cell is how high a voltage it is charged to.

There have been studies showing that charging a Li-Ion cell to it full charge of 4.2 volts can get you around 500 charge/discharge cycles. However, if you limit the charge to 4.1 volts, you end up with less capacity per charge, but your cycle life goes up to over 1500 charge/discharge cycles.

The reason you are noticing longer runtimes from your Li-Ion batteries, is because leaving them on the charger charges them all the way up to 4.2 volts. The runtime is great, but you end up paying for it in reduced cycle life. I usually recommend pulling the battery off the charger as soon as the green light comes on. It will be slightly undercharged, but will last a lot longer.

However, if you are headed out to the bush, let them sit on the charger for an additionalfew hoursto get the most capacity you can.

To summarize:

Both Nickle based and Li-Ion cells will last longer and perform better if you limit the depth of discharge to 80% or less.

Nickle based cells need a 100% discharge every 20 - 50 cycles. This is not recommended, nor needed, with Li-Ion cells.

To get the most life from Li-Ion cells, take them off the charger as soon as the light turns green. To get the most runtime, leave them on the charger for an additional couple of hours to get to a full charge.

There is a danger with continuously trickle charging Li-Ion cells. There is the possibility of plating out Lithium Metal on the electrodes. This can result in an explosive incident the next time the cell is charged.

For this reason, chargers that are properly designed for Li-Ion cells actually shut off the charging current at the end of the charge. There are some "cheap" chargers that do not do this, and your risk is higher using these chargers. If you pull the battery as soon as the green light comes on, there is usually no problems, however if you leave the battery on charge for a week or so, your risks go up.

Finally, never take a NiMh battery down to 0 volts. The open circuit voltage of a NiMh battery should always be above 0.9 volts per cell. The same goes for Li-Ion batteries. With Li-Ion batteries the minimum open circuit resting voltage should be above 2.5 volts per cell, but it is a lot better if it is above 3.2 volts per cell.

With NiCd cells, you can run them all the way down to 0 volts, but take care that they do not reverse charge. I don't think there is any value in going below 0.8 volts, but there have been some studies done that show that you can sometimes recover an ill performing NiCd cell by taking it down to a very low voltage.

Tom
SilverFoxCPF is offline   Reply With Quote
Old Apr 14, 2007, 8:11 AM   #4
Member
 
Join Date: Jan 2007
Posts: 76
Default

SilverFoxCPF wrote:
Quote:
What you are doing is going for a 100% depth of discharge.* That is an important step in keeping NiMh and NiCd cells in good shape, however, it does not need to be done every discharge.* If you do that every time, you will end up with fewer total cycles.* The complete discharge us usually done once in 20 - 50 charge/discharge cycles.
Silverfox,

I have a question on this... in another thread, "rules of thumb," you mentioned that it good to run a NiMh through a full discharge/charge cycle once a month to keep the batt. in top shape (but in that statement seemed to be referring more to a batt. in storage). I am finding that my Sanyo 2700s and Eneloops last so long, with me being a relatively light user, that my batteries can easily last for a month or more in my devices on a single charge.

So, for my usage pattern, would it be perferable to run the NiMhs until the devices until it shuts down, and then run my charger (a Lightning 4000N) in discharge/charge mode, each and every time (which would be around once per month)?

Lastly, would this be OK for both the Eneloops as well as the 2700s or do the low self-discharge batts have different care requirements?

Thanks.
reppans is offline   Reply With Quote
Old Apr 14, 2007, 2:00 PM   #5
Senior Member
 
Join Date: Jul 2005
Posts: 358
Default

Hello Reppans,

It sounds to me that you are "storing" your batteries in your devices. You need to get out more often and "use" them... :-)

The reason behind the monthly cycling is to keep your cells "vibrant." When cells are stored and not used, then tend to go to sleep.

If you think you will be satisfied with "drowsy" cells, stretch the cycle time to 3 or 6 months.

Then Eneloop cells fall into a different category. The purpose of cycling is to keep the crystal size within the cell uniform and small. The crystals join together during the self discharge process. When you eliminate the self discharge process from the equation, I don't think you need to worry about monthly cycling.

These new low self discharge cells are making using rechargeable cells a lot easier.

Tom
SilverFoxCPF is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 6:55 AM.