Here's a picture:

Yep.

1 Sub C battery is 55 grams (not sure if this is the one used in hump packs)
1 AA battery is 24 grams
1 CR2 battery is 11 grams

So it's shorter, yet fatter but about half the weight of an alkaline.

Just found this...

http://www.amainhobbies.com/product_...-Balancer-Plug

Don't know if this is using CR2 (doubt it) batteries but it only has 2 cells outputing 6.6v and 1700mAh... hmmm..

That's a 2s1p pack. Each cell is 3.3v, 1700mah.
It would weigh twice as much and be twice as long as 4 of your CR2's.

Others have mentioned capacity, how long the pack will last at a given discharge rate. I don't think anyone has mentioned what the discharge rate could be. I don't think you can pull very fast out of those camera batteries.

Alright. I'll be trying this mod out in the next couple days. Will keep you posted as to how it works. Thanks for your help.

One last thing...

You said that with just 2 cells I would be getting 800 mAh. Is 800 mAh not enough to run the Rx? I understand that from hump packs, mAh is generally what's used to determine the charge of the battery. I.e. a higher mAh the longer run times before recharging.

Or, is this applying to what Lords was saying about having a run away car because there isn't enough juice left to get back to the Tx/Rx...

Capacity:
An 800mah capacity pack will let you pull 800ma for one hour.
A 1600mah capacity pack can pull 800ma for 2 hours.

Rate:
A battery rated to pull 800ma can pull 800ma for an hour.
A battery rated to pull 800ma can pull 5 amps for a few minutes before overheating and puking its guts all over the receiver box.
It's probably exaggerated, but hopefully you get the idea.

My bad, you would need 4 of those small 800mah cells to make a 1600mah eq hump pac..... 2 in series to increase voltage and then those 2 in parallel to get some capacity. If you're not running high torque servos, two cells for an 800mah pac may last as long as you want it too.

If you're running high torque servos, you'll need the extra capacity paralleling would give you.

I am happy to report, I completed the mod with 4 CR2 batteries. I get, quite literally, lightning fast speed on my steering servo and throttle/brake servo. Very responsive and much better than 4 AA batteries. Not sure how much better it would be than a 5 cell NiMH hump but am more than pleased with my $4 mod.

Price-wise, it's just fine for me. 4 AA's are about $2.50 or so depending. On eBay you can find 4 CR2's for as cheap as $4. The extra $1.50 gives me more power and seems to be more responsive.

Now I just need to wait and see how long it'll last. By the way, this thing is TINY!

Thanks to everyone that replied!

Glad to hear the pack works like intended. Interested in your comments on how long this pack seems to last, seems to be the only downside with this arrangement.

NiMh self discharges and you have to maintain them or their performance suffers. Low self discharge NiMh may be an alternative like these CR2s.

These are actually not NiMH. These batteries are Lithium.

I know they're diff chemistries, all I was trying to say is LSD NiMhs have almost no self discharge. They discharge almost only what you discharge from them, so they last longer than ordinary NiMhs which self discharge just sitting. Thats the downside I see with a NiMh hump pack, it needs to be used or it needs maintenance due to this self discharging.


LSDs AAs as a hump pac would have longer life and be rechargeable so you wouldn't have to be building a new pac every so often. The thing I don't have a feel for is how often......

Indeed. I guess that's what I'm waiting for too. Which AA do people use?

For LSD NiMH AA's, can I charge it with my NiMH charger at low current? I may need to purchase some...