I'm interested in going to an enloop-style setup for ease of charging and battery care, but I've got a question that I haven't found a good answer to that you might know.
The Lipo packs peopl use usually have current ratings in the 10-50 amp range. The AA enloops appear to have them in the 2-4 amp range. Without doing a *massive* parallel pack, how do they compensate? Are the stats wrong? Sounds like you're getting decent performance, what's the deal?
Can you link batteries and a charger you'd use? Do you build packs or keep them as AA format in cell-holders?
There's more to picking a battery than it can "handle" a certain number of amps. It's not like a battery pack will work a certain way up to a certain current draw, then suddenly stop working - it's more of a continuum of gradually decreasing performance as the current draw increases. That's why discharge curves from a battery analyzer (such as the CBA IV; I have the CBA III and love it, but I don't have the time to analyze loose cells or packs right now) are so important. The discharge curve I referenced in an earlier post in this thread is really helpful because you can see how the voltage sags as the current increases.
So to answer your question, when you compare a "10-50" amp draw 2s LiPo to a 6 cell AA Eneloop self-made pack, it's not like LiPo pack will appear to be much more powerful or more durable. First of all, a pair of MTB Rhinos is not pulling as much current as you think. I don't have the specs handy, but I know the stall current per motor is about 8 amps. So the most your're going to need from your battery pack is 16 amps and that's only for a split second when the flywheels start up. When the motors are running between shots, the current will be far less, probably under 8 amps for both motors (my guesstimate).
Second of all, Eneloops can handle more than 2-4 amps. Sure, you'll get voltage sag (see the reference chart for exact numbers), but that doesn't mean they won't work. I wouldn't push Eneloops past about 10 amps, continuous, though. And don't forget that you're not running your batteries at full tilt all the time. Most matches end after 5-20 minutes (in my experience) and during that time, you're not running your flywheels at full speed (or shooting) that whole time. So even if you were pushing your Eneloops too hard (which in our case would only reduce their life from 1,000 or so cycles to a few hundred, which is still a long life), the pack has plenty of down time to cool off. And even if your game lasts much longer (like HVz), again, you're not revving your flywheels continuously.
As for the cells I use, I use the white 2,000mah Eneloop AA cells you can get from Amazon. As long as you buy them from a reputable seller, you're getting good cells (generation 3 or later). I'd avoid the black Eneloops Pros since they have higher internal resistance. Yes, the Pros have more capacity, but 2,000mah is more than enough for a day's worth of Nerfing so there's no need to boost capacity by 25% at the expense of higher internal resistance, i.e. less ability to handle higher current draws.
As for my charger, I use a peak charger that can handle a various number of nickel cells. I use this:
It's been discontinued and there are other options out there. You need to have an external power supply to use it; I use a CPU power supply.
I also build my own packs. Do not use a battery holder like you'd get from Radio Shack. Those things are very inefficient and could melt in our application. I wouldn't use those holders if I needed to pull more than a few hundred mah from my cells.
Edited by shandsgator8, 23 June 2017 - 03:07 PM.