voo2doo

Hi ya bud
Ya said ya got a battery pack off the Net! Where did ya go (cant find the post) I have got AAA X5 in mine i was wondering I was wondering if the car can take Sub-C's?Running 2X 1/4 scale servos and a 150 Oz throttle/brake servo with a JR XR3 FM reciver.How many Milli-amps can ya go up to (3300 would be nice)
Cheers bud.
Vo0[&:]

ibstar

try here http://www.modelpower.co.uk/
he will make you what ever you want with whatever connectors you want

Jared1106

Voo
I got my 3300 mAH 5 Sub-C pack at cheapbatterypacks.com
It is an excellant site, you custom choose what you want from # of cells, to the mAH's, to the wire size right down to the color of the shrink wrap!
I got mine with the Hi-Tec connector so it will plug right into my on/off switch that goes to my receiver, but I had him add a Tamayia end also so I can do quick charges (due to the Hi-Tec ends only come in 1 standard wire size).
I ordered mine on a Friday AM, it was here Monday AM. I am sure he (Mike) will ship to you in the UK..
I was using AAA before that, didnt last very long, this pack is great, of coarse I got the black shrink wrap and is fits right into the battery strip nicly!
Good Luck!!

CowboyBob

I ordered mine from VS Modelsports (in California). They custom-make their own batteries and they told me that the one I ordered is the same one that all the 1/5th scale guys on the west coast run. Its a 3300 maH 5-cell, sub-C pack and its NiMH instead if Ni-cd (this makes it nice since the NiMh doesn't hold a memory and you don't have to discharge the battery like Ni-cd).

I think I paid somewhere around $30.00 for it and it has the receiver lead and the Tamiya lead for charging.

CowboyBob

Jared1106

Mine is NiMH also. It was around 34.00 shipped.

randyg-rcu

Total bull, sadly. Far, far more packs are ruined by people discharging them for no reason than have developed memory in the entire history of the nicd.

Memory can only develop with very exact charge/discharge cycles and no overcharge, meaning discharged slowly for exactly the same rate and period of time, then charged incompletely, again the exact same amount and same time. This does not happen with r/c usage. And, even if by some amazing chance you do experience memory, a couple full cycles will always completely restore the pack.

Now let's consider the process of discharging a pack for no reason. First, if you discharge a pack completely, you _will_ destroy the pack in short order (assuming your pack cost less than $100). What happens is the cells all have very slightly different capacities (unless you buy an expensive matched pack), and one cell will go dead before the others. This cell then gets charged in reverse, which is very, very bad for the cell. The words "may burst or explode if put into charger backwards" come to mind, but usually all that happens is the cell is damaged, lowering its capacity. which then causes it to die sooner. which then causes it to spend more time at opposite polarity. etc. repeat until pack becomes paperweight, very few cycles later.

The solution to the above is to stop discharge before any of the cells fully die. A good approximation for this stopping point is 1V/cell, which assuming reasonably healthy cells, shouldn't discharge any of them excessively.

But, that's not the only problem. nicds (like all other cell types) have a finite cycle lifetime. cycling them further for no reason just wears the cell out sooner.

Things commonly mistaken for memory:

One or more shorted or otherwise damaged cells. Frequently caused by overdischarging the pack in an effort to prevent memory. Symptoms typically are a pack that works at full performance for a period of time, then has a sudden drop in output voltage as the bad cells go dead first. A pack with severely shorted cells will never reach full voltage when charging, or might have very high self-discharge.

Dendrite shorts. A dendrite short is caused by crystal structures forming which puncture the separator between the plates. The typical cause is allowing batteries to self-discharge, which should never, ever be done. nicd packs should be stored discharged down to 1.0V/cell. A dendrite shorted cell can temporarily be fixed by a very large current surge (I throw a large capacitor bank across the cell with a knife switch), but it will fail again, typically as soon as the pack is fully discharged. Dendrite shorts cause cells to rapidly self-discharge, resulting in one cell going dead sooner (as mentioned above), and may seem like memory. Completely shorted cells will not charge at all, as the discharge rate exceeds the charge rate.

Dried out cells. Typically green and fuzzy. Caused by over-temperature forcing the cells to vent, or chronic overcharging, typically by means of a trickle charger. Cell is missing electrolyte and/or the electrolyte has turned to powder, resuling in greatly increased internal resistance and reduced capacity.

Voltage depression. Caused by chronic overcharging/trickle charging. Causes a lower output voltage for the full length of the discharge cycle, frequently .1 to .2 v/cell. Cell capacity remains mostly unaffected. Depending on the exact cause and its effect on the cell, may be reversable, may not be. If it is reversable, a couple full cycles (not below 1.0V/cell) will fix it. Not to be mistaken for a dried out cell.

Operator error. Let's say you use your cordless phone to call someone for one hour every day. Over time the battery wears out or fails for other reasons, and its capacity reduces. Eventually you're using the entire capacity of the cell to make than one hour call. Then one day you try to make a one and a half hour call, and an hour and 5 minutes into the call the battery dies. Most people will now shout "MEMORY! MEMORY!", while the real cause is just the user not noticing the gradual loss of capacity.

This is not to say that nicds should never be cycled; a cycling can frequently be beneficial to nicds (not below 1.0V/cell!), as it fixes most of the common problems. A properly done discharge (down to 1.0V/cell, at a rate of about 0.5-1C), followed by a proper slow charge (C/10 for 14), will evenly reform the crystal layer. A nicd that has been sitting for a while will frequently benefit greatly from being cycled, as will ones suffering from many of the things listed above.

A better approach would be to only cycle cells when a performance problem becomes apparent, making sure to terminate the discharge properly, as well as give it a standard slow charge to a bit above the cell's capacity (cell should be allowed to warm to the touch, then not charged further). maybe also if you're about to enter a big race and really want every mAh of capacity. But not more often, and NEVER by the cheap resistor dischargers built into crap chargers. I've heard experts quote that a full cycle of a pack every 6 months is a good number, as unless you're doing something severely wrong, they won't develop problems nearly that quickly.

A _cell_ can be discharged down to 0v with no ill effects. A _pack_ should never be discharged below 1.0 V/cell, unless you have a way of monitoring each cell individually to immediately terminate the discharge when any one of them gets to 0V.


As to care and feeding of nicds... use a good charger (not a crap timer one), never trickle charge, don't excessively overcharge, never, ever let a nicd pack self-discharge, don't cycle a pack without a reason, don't abuse the cells (if they're too hot to touch, you're doing something wrong), don't overdischarge (once any cell drops to 0v, or the pack voltage drops below 1.0V/cell, stop using the pack), such as happens with an electric car if you keep driving it even as the pack is dying, don't use a nicd fast charger with nimh cells, and don't use any charger made by radio shack.


Hmm, now I'm ranting, aren't I? I'll stop now.


I wish I could find my graphs... somewhere I have charts of nicd discharge curves showing every problem mentioned above. I made them a while ago when giving talks on this exact subject. too bad I can't find them... grr. They were all very pretty to us EE nerds.


--Randy
(NEVER DRAIN PACKS ALL THE WAY TO 0V!)

voo2doo

Thanx for the reply fellas most appreciated. Thanx Randy but all i wanted to know was were to buy Sub :C:s,[&:] but thanx for the info.
Thanx again fellas
Vo0