This post was initially intended to be in this thread because I'd like to clarify some points raised in the thread. But then I thought it was deserved its own thread.
JIM D. wrote:... the 24 volt battery pack for the Roland models FR-5, 7, 7x & 8x "ARE NOT" made from the normal AA batteries that we use . The 20 batteries in these battery packs are a larger industrial size with much more capacity.
Correct. The size of the cells in the pack is actually "4/3 Fat A" (18mm diameter x 67mm height). Its storage capacity is 4,000 - 4,500mAh. You can see a listing here.
JerryPH wrote:I am willing to bet that the batteries in the Roland won't exceed the capacity of the Eneloop or PowerEx batteries.
You lost the bet, Jerry
JerryPH wrote:Something is not right, 4500 divided by 20 cells = 225mAh per each battery... that sounds super low, maybe I am just not calculating that correctly??
If I am, 20 Eneloop batteries would equal 50,000mAh... and that would be like 54,000mAh for the PowerEx batteries!
When combining batteries, you multiply the voltage (series configuration) or you multiply the current (parallel configuration). You can't do both.
Each of the cell in Roland pack is 1.2V, 4,500mAh. A pack of 20 will either has 24V, 4,500mAh, or 1.2V, 90,000mAh (there are mixed configurations but let's leave them out for now). The cells in Roland pack is in series configuration, thus 24V and 4,500mAh.
For my FR-7, I used this battery pack, which is half the size, half the weight, and half the capacity of the Roland pack. It gave me about 4hr of playing. I used packing foam in the battery compartment so that it wouldn't move around:
A friend of mine needed a spare battery pack for his FR-7x so I gave it to him.
Now I'm using this as a back-up. This (vs a dedicated 24V battery pack) is better for me because for my other hobby (photography), I have a lot of AA rechargeable battery cells, which sit idle most of the time. In the photo, one cell is removed so you can see the temperature sensor (arrow tip). The charger reads the temperature and stops charging at 60°F.
It's a tight fit in the FR-7 battery compartment:
The battery pack can be charged by the Roland charger (in the FBC-7). I prefer to use the slow charger (500mA), however:
Or in-situ with a home-made adapter:
Of course I can remove the AA cells from the pack and condition/charge them individually with my Maha charger.