Cool. Thanks much!

Ramsey

I used the CH-910 extensively for 4 or 5 years and the discharge is equal to about the time of two fully charged batteries. They charge the batteries separately and discharge them separately. I have been told this by Canon reps many times of the years.

<<<-- Originally posted by Jeff Donald : I used the CH-910 extensively for 4 or 5 years and the discharge is equal to about the time of two fully charged batteries. They charge the batteries separately and discharge them separately. I have been told this by Canon reps many times of the years. -->>>

Me too! But hoping that there is some truth to the other statements made here.

Not in my experience with Canon batteries and third party batteries from Lenmar. My batteries last about 5 years with no refrigeration. I try to store lithium batteries charged, but at times I forget and store them in a partial state of discharge. I never drain lithium batteries completely. I have several sources that say draining lithium batteries is not recommended.

I hate to keep plugging them, because I must seem like a shill for the company but I've shot over 8 hours on a single Anton/Bauer Dionic 90....

Matt

Jeff, yes, I'm aware that there are many recommendations, and this is precisely why I was interested hearing your experience. In fact, contradictory recommendations are maybe due to the fact that all Li-ion are not of the same type.

About CH-910, with new batteries it's clear that the holder doubles only the shooting time of a single battery. But, once the batteries become old, the internal resistance increases, and then having two in parallel implies that the shooting time may extend that of two single batteries. And this is what my experience also seems to suggest.

Simplified example: Say, in case of single old battery, 80% of the power is wasted in heat losses inside the battery, and 20% is what is exploited by the camcorder. Connecting two in parallel means the current is halved and heat losses are 1/4 of that in case of a single battery. This implies the ratio between power used by the camcorder and the power wasted in losses improves significantly. (To say accurately what really happens is rather difficult for the internal resistance needs not to be a constant. That's why my explanation is a simplification.)

Now, the reason why Canon reps say CH-910 is just a holder running the batteries sequentially may well be their conclusion from the fact that with new batteries it just doubles the shooting time. However, the real advantage of parallel connection is likely to show up only with aged batteries.

It's a pity that companies like Canon, Sony etc. do not make such their specs clearly available. So much time and effort is wasted in speculations and guessing what they may have done. Wish this forum, and people like Chris, could convince Canon to give their users proper and accurate information of their technical solutions within their products.

Dual Battery Holder CH-900
 

Finally found the manual, and it clearly states:

As you use the camcorder, power is taken equally from both battery packs.

So, at least we know now that not all reps are that reliable.

While I buy the explanation of why paralleling is advantageous in theory if you stick a couple of numbers into it the conclusion is not so clear. The XL2 requires 7.1 watts and the batteries are 7.2 volt batteries. Current demand is thus very close to 1 amp. The internal impedance of the batteries has got to be low enough that the voltage drop across it is small. Lets say that is a volt so that the camera actually has 6.2 volts across it's terminals and must, thus draw 1.15 amps from the battery (to get 7.1 watts). This makes the battery internal impedance 1/1.15 = 0.9 Ohm and (1.1)*(1.1)*(0.9) = 1 watt is dissipated in this impedance with 7.1 being consumed by the camera. The battery is 100*7.1/6.1 = 87% efficient. Paralleling two of these batteries results in each supplying half the current but the current demand is a little less than half that required from the single battery i.e. about 0.527 amp so the dissipation in a single battery's internal impedance is (0.9)*(0.527)*(0.527) = 0.25 watt for a total dissipation of 0.5 watt and the overall efficiency is 100*7.1/7.6 = 93%. This is an improvement but not a doubling!

A.J.

How long do batteries last on the XL2?

On my recent trip to Mexico with the camera I'd mount a fully charged third party (Power2000 - got it from B&H) substitute for the BP-945 (rated 6000 mAh or twice that of the BP930) each morning. In the course of a day I'd shoot perhaps 3/4 of an hour of video and never pay a lot of attention as to whether the camera was on standby or not. At the end of the day there was plenty of juice left to rewind the tape and play it back for review. The battery was still not exhausted (indicator did not show full) but how much was left I couldn't say.

Note that while this is a 3rd party battery pack it's a good bet that if I cracked it open I'd find the same cells that Canon puts in their packs as there are a limited number of manufacturers of these.

It's interesting that the camera manual states that the 945 with it's double capacity relative to the 930 is only supposed to give 50% more recording time.

A.J.

No one is checking my math! That should be 100*7.1/8.1 = 87% (OK, it's tecnically a typo, not a math error).

A.J.

NP1 Batteries to power XL2?
 

Hello all.

I need to invest in an NP-1 battery for a camera stabilizer and was wondering if these batteries can power an XL2 (and for how long). If that's the case, I have no problem doing so as the batteries can serve double duty as I was planning on getting a longer life battery anyhow.

If I can use the NP1s, what'll I need to use them to power the XL2.

Thanks!
Sal

The NP1 batteries are 12-13V, while the XL-1/XL2 cameras use 7-8V. You need to use a DC voltage converter to "step down" the voltage.
HTH
Alex Dolgin

It is true, that reducing the load current from a battery increases its effective capacity somewhat. There are graphs provided by the cell vendors, showing the difference depending on the load current. Changing the current from 1 A to .5 A might increase the the effective capacity by 10-20% at most. BUT - it is in theory. Practically there is no way to benefit from it as there is absolutely no way to parallel the batteries using direct connection. If a charged battery wired directly to a discharged one, the discharged battery would start sucking in a lot of uncontrolled current from a charged one, causing irreversible damage to itself, and possibly to the charged one. The only way to parallel them is by using 2 diodes in "Y" configuration, as the diodes would prevent the current back flow. But using the diodes would cause other unpleasant effects, as they would have voltage drop on them, and heating losses as a result. Most probably the Canon dual battery piece has a low loss switch (solid state), that selects a battery at a time.
As far as Li-Ion cells aging, they loose about 10%/year regardless of use. In addition to that, they age as they are being used. Discharging them outside normal use would only wear them down faster. A new battery has a certain cycle life to it, say 500 full discharge cycles. If it is discharged 50% every time, it would deliver 1000 shallow cycles. So adding extra discharge to them would just reduce its usefull service life.
HTH
Alex

Ok, now this is a experimental fact: I put one of my seven year old BP-930 batteries to the camcorder and in max there is not enough power after 15 minutes of recording. But, if I put two of such batteries to the CH-910 dual holder, I can power the camcorder to record a full 60 minute tape. I guess we do not have enough information to fully understand the reason.