Magic Matt
Enlightened
Every time I post these, I'm sure I can hear some of the more learned members chuckling to themselves. Yes, it's me again, and I've done yet more searching and reading, and could do with a sanity check for my plan.
Posting in the batteries section because I think this is more a battery questionn than anything else... feel free to whack me with the n00b-stick if not.
I think the hipCC controller (link below) seems like the best suited to what I want to do, which is drive the P7 at various levels via PWM. I don't know if I'll try to build my own controller, or buy one (the hipFlex is slightly too large to fit into my donor body).
I intend to build myself some sort of 6P AA holder to fit in a 2D space. Here's my thinking that I think needs checking... would somebody mind getting the red teachers pen out?
What I don't understand is where the safe maximum is. Obviously at 4.5A that's basically short circuiting the cells, and all the power would be expelled from the battery as heat ...
Am I ok to pull 2.8A from the cells without damaging them? To clarify, I intend to do this under a "turbo" scenario in burst of a few minutes, but I don't want to damage anything if it were to be left on turbo until the cells are flat.
Assuming it's ok, is there a way to work out how hot they will get, and how long they will actually last compared to a theoretical time span (2.8A @ 2Ah = about 43 mins)?
Is there a 'low voltage' beyond which you shouldn't discharge an NiMH, like there is with Li-ion cells?
Posting in the batteries section because I think this is more a battery questionn than anything else... feel free to whack me with the n00b-stick if not.
I think the hipCC controller (link below) seems like the best suited to what I want to do, which is drive the P7 at various levels via PWM. I don't know if I'll try to build my own controller, or buy one (the hipFlex is slightly too large to fit into my donor body).
I intend to build myself some sort of 6P AA holder to fit in a 2D space. Here's my thinking that I think needs checking... would somebody mind getting the red teachers pen out?
- 6P AA NiMH cells, at 0.1ohm internal resistance gives me a total resistance of 0.6ohm for the cells.
- Each cell has 1.25V (avg) to 1.4V (max) meaning the total voltage will be between 7.5V and 8.4V
- I'm intending to use Eneloops which means that my capacity will be 2000mAh because they're connected in series.
- I = V/R so my theoretical maximum current is going to be (8.4V * 0.6 ohm) = 5.04Amp and my maximum current during the life of the battery will be (7.5V * 0.6 ohm) = 4.5A
What I don't understand is where the safe maximum is. Obviously at 4.5A that's basically short circuiting the cells, and all the power would be expelled from the battery as heat ...
Am I ok to pull 2.8A from the cells without damaging them? To clarify, I intend to do this under a "turbo" scenario in burst of a few minutes, but I don't want to damage anything if it were to be left on turbo until the cells are flat.
Assuming it's ok, is there a way to work out how hot they will get, and how long they will actually last compared to a theoretical time span (2.8A @ 2Ah = about 43 mins)?
Is there a 'low voltage' beyond which you shouldn't discharge an NiMH, like there is with Li-ion cells?
