Large Model Association Forum

I thought that I would be the first to start this forum!
For the last few months I have been obtaining some facts on AA size cells that are over 2000mAh NiMh. You may have read in the latest BMFA News that you have to check this type of cells better than we had to with Nicads. If you had problems with this type of cell please email me at hayesflyer@yahoo.co.uk
Keep the watts up! Robert Mahoney

[quote="robertmahoney"]
For the last few months I have been obtaining some facts on AA size cells that are over 2000mAh NiMh.

Interested to read of your conclusions with AA cells versus sub C, Robert.
I've always assumed sub C's are able to deliver higher current flow than the same capacity double A's.
So while a double A might be OK in a sedate K8, sub C's would be eminently more suitable in say an aerobatic model pulling large currents over a shorter time period. Is that a correct assumption?

Hi Dave, you are correct in getting more amperage out of sub C cells! I would never use AA cells as a main power source as the insulator is very thin. I am investigating there use in transmitter and receiver packs! In the good old days of nicad cells you could come home after a good days flying plug in the charger that came with the set i.e. a slow charge. Some time later (could be a couple of days) you remember that you haven’t unplugged the charger from the mains, well we knew that nicads could that the abuse! Now we have NiMh’s, they cannot take that type of abuse because of the very thin insulator they use. Over 2000mah the insulator is so thin it has been known that a cell has started on runaway cycle with so much heat that it set other cells to explode, this happened to me last year! Another fault is you think the pack is charged Ok but after a few minuets of use you get the warning bleeps that the voltage is very low, this happened this year to one of my club member! To end this, I have been testing about 20 types of cells and up to now it seams to only happen to cell that are over 2000mah. I have been in touch with the BMFA and some manufactures about this and I will not comment yet to what they said as there is more investigation to be done!
This is why I need flyers help.
Regards Robert Mahoney
BEFA Chairman

P.S How many of you have a 3cell 11.1v Lipoly in the transmitter instead of a 9.6v pack?

I hope all the positive advertising, by Sanyo, regarding the new Sanyo Eneloop 2000mah batteries isn't a load of eye-wash as I've just started using them !!

Hi Ron, the latest Sanyo cell and others like them i.e. that come ready charged are the best that I tested to date. They are constructed like the old Nicad’s we used before!

Regards Robert Mahoney

Thanks for that Robert, they are still to have their first flight in a Tangent Flamingo serving six servos and the Rx.
Rgds,Ron.

robertmahoney wrote:.........I have been obtaining some facts on AA size cells that are over 2000mAh NiMh................If you had problems with this type of cell please email me...........

Hi Robert,
There have been other discussions on this and other websites about the use of "consumer" NiMh's.
Don't use them.....Mr Shultze "of charger fame" says so, and he knows much more than we do!
What is more he has some things to say about charging NiMh's that will surprise many modellers who have been brought up with Nicads and have been fed wrong information about NiMh's like......"you have to slow charge them"......"they are free of memory problems".

I urge you to read his exhaustive battery care advice which includes every single type of rechargeable battery as well as NiMh's.
You will find the advice on his company website contained in a section repeated within all of the individual instructions for his various chargers.

http://schulze-elektronik-gmbh.de/index_uk.htm

Edit
Look for Instructions Download then scroll down to ISL 6-Series 8.41 Nov 2005.
If you can't find it let me know and I'll send you the pdf.

Thanks Rob for the information, I spoke Matthias in 2004 at York WC about this when he repaired my charger on the field (how that for service) so it not a new problem!
The problem I have now found that some slow chargers could be a fault as well!

Regards Robert Mahoney
BEFA Chairman

Hi all,
You may like to know that Bob Smith and myself were at the BMFA safety revue meeting in October and the problem of NiMhs was talked about in great lengths. Bob has writing an article on AA size NiMh and will be published in the BMFA news soon! If anyone has more info re failures please email at robert@rlmahoney.co.uk not the yahoo address as in early post.

Regards Robert Mahoney