have anyone here hacked their camera/camecorder...etc batteries?

Please comment about repacking a 2 cell camera battery with 2 unprotected 18650 cells, what is the worst case scenario here


I replaced 2 prismatic cells inside a counterfeit canon 7.4V LPE8 battery with 2 raw panasonic 3100mah 18650 , get truckload of shots everycharge.

I omitted the whole protection PCB, which has 4 electrodes: +,balance,10Kohm & -output.
The SLR battery cabin has 3 electrodes: +, [space], 10Kohm, -

In order to prevent disasters fromshort circuits, I have installed a 2 amp fuse near the 18650 and it should cutoff. Those oversized cells are stored outside the camera, on the carry-belt.

It appears that Canon's SLR has a built-in voltage guage and when the voltage drops to 6.4V=2 x 3.2V, the camera will report 'flat battery' and turns off, thus overdischarge is not an issue here.

I charge them with a xtar WP2II so both cells be reasonably balanced.

Worst case is one cell loses capacity, just because™, and 6.4V ends up being 4.2v and 2.2v, and the repeated overdischarging of the 2nd cell makes it worse, and it vents with flame because of the charging the overdischarged cell. The violence of the venting causes parts to be throw from the camera and injures you, some kittens and puppies, while setting your face on fire, and making you breath some lovely hydrofluoric acid fumes.


Thats just worse case though, since you asked

If you get a small mulitmeter even one of the cheapies from radio shack that are pocket sized, and meter the cells when they come out, and the voltages are roughly the same (dont overly concern yourself with the absolute value, as the accuracy of an el-cheapo multimeter will be poor, but the precision should be good enough), you should be fairly safe.

Now, if you were charging in the camera, I would say you definitely need the thermistor (the 10k ohm) working, but with an external charger, you should be fine.

As CKOD said, if the cells discharge at the same rate and retain the same voltage during all stages of discharge, it may work. The biggest problem is that the camera's circuitry has no clue as to what the voltage of each individual cell is during discharge. This can lead to a problem, if one cell falls significantly lower in voltage than the other. This is also why the original pack has more than two leads, in part, so as to monitor the individual cells during discharge.

Also, charging your two cells on the WP II will not provide balanced cells. Li-Ion cell balancing can only be accomplished by balance charging, another reason the original pack has balance contacts.

If it were me, and someday I'm likely to try this myself, I would incorporate the PCB from the old pack. At the very least, if I didn't, I would use protected cells.

Unfortunately in most cases, when people try to build their own replacement packs, performance and/or safety takes a hit. Usually the better option is to just bite the bullet and buy a a replacement OEM battery pack.:sigh:

Dave

CKOD said:

Worst case is one cell loses capacity, just because™, and 6.4V ends up being 4.2v and 2.2v.................................

Now, if you were charging in the camera, I would say you definitely need the thermistor (the 10k ohm) working, but with an external charger, you should be fine.

Click to expand...

fortunately, my 6.4V consists of two nicely matched 3.2V cells
and EOS600D has no charge function built-in

45/70 said:

As CKOD said, if the cells discharge at the same rate and retain the same voltage during all stages of discharge, it may work. The biggest problem is that the camera's circuitry has no clue as to what the voltage of each individual cell is during discharge. This can lead to a problem, if one cell falls significantly lower in voltage than the other. This is also why the original pack has more than two leads, in part, so as to monitor the individual cells during discharge.

Also, charging your two cells on the WP II will not provide balanced cells. Li-Ion cell balancing can only be accomplished by balance charging, another reason the original pack has balance contacts.

If it were me, and someday I'm likely to try this myself, I would incorporate the PCB from the old pack. At the very least, if I didn't, I would use protected cells.

Unfortunately in most cases, when people try to build their own replacement packs, performance and/or safety takes a hit. Usually the better option is to just bite the bullet and buy a a replacement OEM battery pack.:sigh:

Dave

Click to expand...

Can someone clarify the definition of 'balancing'? it it just voltage matching?

"Balancing" is used to describe a the use of a electronic circuit to ensure that all cells in the pack are receiving an equal charge.

Otherwise you could end up with an unbalanced pack which increases your chances of a having it go BOOM (due to reverse charging) in your camera that you may be holding next to your face.

Hi best. "Balancing charging" is as Dr Jekell described. When cells are balance charged, for example using a hobby charger, all cells being charged are monitored individually, during the charge process. Towards the end of the charging process, cells that are at a higher voltage than others are actually discharged a bit, so as to let the cells with lower voltage "catch up".

Since this balancing process affects all of the cells being charged at the same time, the cells are effectively balance charged. If you charge two, or more cells separately, in a multiple channel charger, or one after the other in a single channel charger, for example, the cells are not really balanced. In this situation, all you accomplish is fully charging each cell. Due to differences in charging bays, the time interval between charges, temperature during charge and other factors, the cells will not really be balanced.

Also, do not confuse "balance charging" with "matching cells'. These have two different meanings. To properly balance charge a set of cells in series for use in a device, the cells must first be "matched". Matching cells involves discharging each cell individually to determine capacity, and then matching up cells with similar capacities. This is primarily, what ensures that individual cells within a "pack" will not be over discharged, or reverse charged during use, causing potential problems. Of course, balance charging a matched set of cells ensures that the cells are equally charged so that they will likely remain "matched".

So while you may balance charge cells, they will not necessarily be matched. For example, it would be possible (although this is never done in series, nor is it advisable to do so) to balance charge a 10440 cell along with an 18650 cell. The result would be a balanced pair of cells, but they would be far from "matched".

Hope this helps.

Dave

45/70 said:

Hi best. "Balancing charging" is as Dr Jekell described. When cells are balance charged, for example using a hobby charger, all cells being charged are monitored individually, during the charge process. Towards the end of the charging process, cells that are at a higher voltage than others are actually discharged a bit, so as to let the cells with lower voltage "catch up"................

Dave

Click to expand...

Thanks a lot

Somehow, I managed to charge them and their final voltage, which were measured after 10 hours of room temp storage (took them off from the charger, put them in the 18650 plastic box)
Guess what? my DMM shown a wonderful agreement of 2mV (4.143V & 4.145 V)
am I doing the right thing or just lucky?

bestsystem said:

am I doing the right thing or just lucky?

Click to expand...

That is very good. Many balancing chargers will not get the cells that close. My point was though, that what you have is two cells that are at the same voltage, they haven't been balance charged. Yes, the difference may seem insignificant, but nonetheless, there is a difference.

In addition to the cells being charged at the same time, under the exact same conditions, balance charging multiple cells in series has one other advantage. During the charging process it is possible to see which cells are lagging behind others. If these same cells are consistently behind when charging, their performance might be considered questionable, and further testing can be done. When cells are charged independently, this information is unavailable.

And again, while balance charging ensures that cells in a series pack start out at the same level of charge, it has little effect on whether cells will maintain similar voltage (SOC) during discharge. It only helps, by starting the cells out at the same level. During actual discharge, the cells may not maintain the same level of charge. This is where carefully matching cell discharge behavior/capacity is important.

Dave

Then can I check their performance by doing this voltage difference check at different SoCs (by shooting 100, 200,400 pictures)?

Anyway, after today's event, with over 150 shots, some with speed-lights and other power hungry manipulations,

the voltage difference is 0.00V (3.80V and 3.80V). I then do a differential voltage different check by connecting both (-) terminal together and measure voltage difference with mV scale, the answer is 0.9mV

too good to be true?


In order to ensure my DMM is working properly, I tested it with other voltage sources like phone battery and 1.5 V zinc carbon cells, all readings made sense.

Sounds good to me, best. I like my cells to stay within 10-20mV down to 3.80 Volts. Below that the voltages will spread out more, but your nearing the end of the discharge anyway. Actually that is where I prefer to stop discharge of LiCo cells, either in "packs" or individually. It doesn't always work out that way, but if stopped at 3.80 Volts, the cycle life of the cells will be significantly improved, over discharging farther.

Dave

45/70 said:

Sounds good to me, best. I like my cells to stay within 10-20mV down to 3.80 Volts. Below that the voltages will spread out more, but your nearing the end of the discharge anyway. Actually that is where I prefer to stop discharge of LiCo cells, either in "packs" or individually. It doesn't always work out that way, but if stopped at 3.80 Volts, the cycle life of the cells will be significantly improved, over discharging farther.

Dave

Click to expand...

Just to clarify that the battery hasn't stopped discharging, just the photo shoot finished.

The canon 600D has a 3 level :scowl: battery indicator, and is still full at 3.8+3.8=7.6V
will see more after more shots

idle the battery @ 3.8V for a few days will not kill them instantly, many people will damn fully charge li-ions right after use:shrug:

bestsystem said:

idle the battery @ 3.8V for a few days will not kill them instantly, many people will damn fully charge li-ions right after use:shrug:

Click to expand...

This is true. Actually, if you store Li-Ion cells, it is best if the voltage is between 3.75 and 3.85 Volts, for LiCo cells. In addition, I store my cells that are not in service, in my fridge at 35-40F. Storing cells at about a 40% SOC level at cooler than room temperature has a significant effect on Li-Ion cell longevity. Table 3, on this This page from Battery University deals with the effects of both temperature and SOC when storing Li-Ion cells at various charge levels and temperatures.

One additional advantage to stopping discharge of LiCo cells at ~3.80 Volts, is that they can then be returned to storage, without any maintenance. That, and the extended cycle life achievable by not deeply discharging cells each use, has a very positive combined effect on cell longevity.

Dave

45/70 said:

This is true. Actually, if you store Li-Ion cells, it is best if the voltage is between 3.75 and 3.85 Volts, for LiCo cells. In addition, I store my cells that are not in service, in my fridge at 35-40F. Storing cells at about a 40% SOC level at cooler than room temperature has a significant effect on Li-Ion cell longevity. Table 3, on this This page from Battery University deals with the effects of both temperature and SOC when storing Li-Ion cells at various charge levels and temperatures.

One additional advantage to stopping discharge of LiCo cells at ~3.80 Volts, is that they can then be returned to storage, without any maintenance. That, and the extended cycle life achievable by not deeply discharging cells each use, has a very positive combined effect on cell longevity.

Dave

Click to expand...

nice, but I dont bother to put them in a fridge, others people will have too much opinions.

I am not meaning to stop using the battery when it drops to 3.8V, I will continue to use them without charging it, and the 'battery exhausted ' message popup at 6.4V (ideally 3.2V x2 cells), then time to top them up to 3.7-3.8V.

And charge them to 4.14V using my WP2 II before shoot:duh2:

After observing my HP Battery Check program (netbook, 6 Korean cells in Feb 2011 , 5100mah, a few millivolt inter-cell difference), the 100% charge is at 4.16-17V, and it quits at 3.0ish V, thus I believe my method is not too different from the 'trusted' HP OEM one in terms of voltage:thumbsup: