6cells into 4cells, and back again (NiMH)

[dhutch]

I have two cars, a 4cell 12th scale and a 6cell 10th, i race the 12th indoors, over winter and then i'll swap the 10th mid march.

So what i plan to do is turn 3*4cells into 2*6cells, becuase otherwise they wont get used for half the year and will end up old and out of date before the've been used much.

So my question is, when should i remake them, when there fully charged, or when the fully flat? - or somewhere inbetween (but all at the same voltage!!)

- or should i dissasembe them, do a cycal with them totaly induvidually, on my "domestic" NiMH charge, and them reassemble them


daniel

[newracer]

it is best to dis-assemble and assemble packs when fully discharged to .9v/cell.

[dhutch]

ok, thanks

[RCHavok797]

You definately do not want to be messing around with fully charged cells when you are assembling them.

[Mike01]

A cell discharged to .9V is not fully discharged. If you short such a cell, it will spark and may burn you.

[4W Guy]

A cell discharged to .9V is not fully discharged. If you short such a cell, it will spark and may burn you.

Discharge to .09V. Then do your solder work. Or if you can afford new batteries, buy new for your 6 cell packs and just leave the 4 cell for next season. Cycle them once a month and they should be good to go. I did this and all my 4 cell packs were ready to race with a fresh cycle on race day. I am not the best racer and don't have the best batteries but the charge numbers seemed to be just a good doing this.

[highroller]

Problem you may run into when taking a 6cell pack then making 4cell pack is the cells may not be tightly matched, also the cells do pick up a type of memory and perform the way they are used. So switching back to 6cells they may have a tendancy to perform when used in 1/12th racing, it may take a couple of cycles for cells to eventually used to being used under another type of racing like stock offroad.
To reassemble them back from one configuration to another discharge the pack, using an equalizing tray to further discharge each cell before taking it apart and rebuilding it. It also helps to label each cell so you have an idea which cells came from each 6cell pack when building it back and forth, that's if the cells are matched.
If these are the GP3300 cells you can store them one of two ways depending on what they are being used for and the level of racing you do. Personally I find it best for purchased packs for their intended purpose rather than mixing them up for different types of racing. High voltage/runtime mostly 4cells are used for oval mod and 19turn with prices $42-59 for 420/1.17+, mid level runtime/voltage 400/1.16 are mostly for offroad and touring car racing. For storage the packs are just put away at .90 volts per cell, stock cells are dead shorted. Packs have been stored up to 6 months untouched, but 2weeks or so before I race or season starts each pack is cycle and compare with it's previous numbers (a log is kept on each pack with peak voltage, mah rating, runtime at discharge load, average voltage, mah at discharge). If numbers are low or inconsistant the pack is cycled 2 or 3 times until numbers are more consistant. I try to allow 2-3 days between the cycles and race day. Those packs that show really big decline may get rebuilt into 6cell or practice packs and get replaced with new packs. The cells I've bought so far have remained pretty consistant that I only need to purchase new packs usually 2 each once every 6-8months or maybe 3 or 4 if I attend a really big race.