Are all 7.2 Batteries Created Equal?

[rjeffers]

I'm curious to know, what are the best type of 7.2 batteries to run in a starter box? (Brand, etc.).

Thanks.

[MattHiggins]

You'll be fine with any name brand stick packs. Get some NiMH packs and just don't store them with no charge or over heat them when charging and they'll last a long time.

[rjeffers]

Matt, thanks for responding. One last question, I've searched some stick packs and I see 3000 - 3800 mah ratings. Does the higher number mean more run time / power?

Thanks again.

[Slammed94]

Yes, the higher the number the more run time you get.

[evst 360]

One last question, I've searched some stick packs and I see 3000 - 3800 mah ratings. Does the higher number mean more run time / power?

Thanks again.
yes. The higher the mah, the higher the capacity of the pack is. Packs with a higher mah will also have higher discharge rates, allowing you to pull more juice out of them faster. You may not feel much of a difference in a starter box, but in car applications you get more punch with higher mah packs. :cool:

[josh222]

for a starter box a 12V gellcell battery would work great, they last a really long time

[rjeffers]

yes. The higher the mah, the higher the capacity of the pack is. Packs with a higher mah will also have higher discharge rates, allowing you to pull more juice out of them faster. You may not feel much of a difference in a starter box, but in car applications you get more punch with higher mah packs. :cool:

I am using the box to start a 1/8 on-road engine. I could certainly use as much punch as I can get. Can you recommend a good pack for this application?

[rjeffers]

for a starter box a 12V gellcell battery would work great, they last a really long time

Unfortunately I have a mugen pro RII starter box and the 12v gel cell battery won't fit...I know cause I have tried. :(

[evst 360]

I am using the box to start a 1/8 on-road engine. I could certainly use as much punch as I can get. Can you recommend a good pack for this application?
this (http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLWR4) would be a good pack. its 3900 mah, good quality GP cells, and its only $30. :cool:

[rjeffers]

I just picked up a couple stick packs for my box. Thanks for the info guys. One last thing, what's the max amp you recommend to charge the battery. Btw, I'm using a hobbico quick field charger.

Thanks.

[Dagger Thrasher]

It's usually fine to charge at 1C for Sub-Cs...so if you have a 3800mAh pack, charge at 3.8A. 4200, charge at 4.2A. You can of course charge at higher rates, but 1C will result in a longer lifetime for the cells, and a slightly better capacity.

[Shazz1234]

I just picked myself up a 4600mah NiMH Venom Racing pack and even when I've got it sitting on the desk it feels powerful lol. I've only just recently made the switch from my stock 1900mah NiCd packs and the difference is quite insane.

If you charge at a higher rate then basically you'll get a quicker charge time (derr) but you'll also get more heat in the pack. I'm no expert but I've heard that the lower Amps you charge at the increased lifetime and full charge capacity of the pack?

Is 1C a good base to start with right? Would I be able to charge my 1900 packs at 5A safely?

[SS Pede]

1C will be fine. And yes, 5A will be fine for your 1900 packs. A lower charge rate is obviously easier on the cell, and you also get slightly longer run times. A higher charge rate gives a bit more power.

[evst 360]

If you charge at a higher rate then basically you'll get a quicker charge time (derr) but you'll also get more heat in the pack. I'm no expert but I've heard that the lower Amps you charge at the increased lifetime and full charge capacity of the pack?

Is 1C a good base to start with right? Would I be able to charge my 1900 packs at 5A safely?
any charge rate that is 1C or lower will not affect the lifetime of the pack very much. Charge rates above 1C will begin to shorten the life more noticeably. The only exception would be the high-$$$ competition Ib cells that are said to be ok with a 6a charge, but IMO that is too high.

1C is a good base charge rate, and is the highest charge rate I will charge my nimh batteries at. NiCads can be charged at a higher rate I think, but probably not at 5a for a 1900, maybe more like 2.5-3a for a 1900. :cool:

[Shazz1234]

So How come I see all these chargers out there that have charge rates of 8,9,10+ Amps? Isn't that kind of pointless if you sohuldnt charge them above 1C? Another question (sorry if you feel this thread has been hijacked)... but what about discharge rates? WHats a good C rating to discharge packs at?

[rjeffers]

So How come I see all these chargers out there that have charge rates of 8,9,10+ Amps? Isn't that kind of pointless if you sohuldnt charge them above 1C? Another question (sorry if you feel this thread has been hijacked)... but what about discharge rates? WHats a good C rating to discharge packs at?


ha. I don't feel like it's been hijacked at all. You guys are just answering my future questions. :p

[SS Pede]

Racers may charge their NiMH packs at more than 1C to get a bit of extra power during a race. They sacrifice some pack life for performance. 8, 9, 10 amps is often excessive, but people like to experiment. Very high charge rates are possible, just not ideal for the average person. Also, if you've got a high capacity LiPo pack you can charge it at 1C, which for an 8000 mAh pack would be 8 amps.

You can discharge at all sorts of different rates. 20 or 30 amps will kind of simulate race conditions. I tend to discharge my packs by running them in my truck. It's not really required, but it can be useful for conditioning your packs.

[Demon-TC3]

if your charging cheaper cells you cant charge them at 6+ amps because the IR of the cells is too high and hence they overheat and false peak, the "Top brand" race cells are made in such a way (or modified by the matching companies) to have much much lower Internal resistance than the basic packs and hence can be charged safely at much higher rates.

AS for reducing life of the pack, it is kinda true, heat is obviously not good, but if your charging at 5A with no great heat buildup then its not really going to do much, good battery maintenance (I.e orderly discharging / equalising) is far more important...to an extent.

I am using waht would be considered as "pro" cells which i charge at 5A but top up pre-race at 7A just to give them a little extra kick. cells never get hot, never even too warm.

[Shazz1234]

I think I'll just stick to the 1C that everyone else seems to be charging at... seems to be a good base to stay at...

I picked up a 4600 pack at my LHS and by the sounds of it thats a VERY high capacity pack... seeing as everyone else is talking about 3300mah packs etc... What is the highest capacity NiMH pack on the market atm?

[Demon-TC3]

sorry to break this to you but venom SAY its 4600 when in actual fact i HIGHLY doubt its even close. since they dont produce the proffessional stuff i think they do what some of the "sport" manufacturers do and state the very very maximum the cell capacity could possibly be, a company called Vapextech made some "4000mah" cells not so long ago, but after repeated customer complaints they re-labeled to 3800 and i think then to 3700 or 3600.
Just because the sticker says its 4600, dont beleive it...

Now thats not to say they are bad cells, im not sure how much they cost and as a bashers pack they are probably pretty good.

If anyone else out there wants very high capacity NIMH cells, one place i know that DO NOT lie about the cells is MAXAMPS, 4.4k (4400) cells, they are very good cells, very high voltage and really are 4400mah cells! (priced at $40.00 a pack they are an very well priced!)

[Shazz1234]

Thats false advertising then isn't it? If a pack says 4600 mah then it should hold 4600mah...

[Demon-TC3]

Nope, the manufacturer doesnt state that it WILL hold 4600, it could state the maximum possible capacity of the pack which in an unlikely situation COULD be 4600mah. that is the MAX capacity that that type of cell may possibly reach, what it actually reaches....who knows.

as i said, Vapex had 4000mah on the cells and when customers complained they said "4000 is the max the cells can hold" whereas the average was arround 3700.

[GSMnow]

Good quality cells like the IB4200's and GP-4300's will all hold more than the cell label if charged and discharged at less than the 1C rate (4.2 or 4.3 amps) The big surprise is when you get a team quality matched pack, and they exceed the cell rating when discharged at 35 amps. My ProMatch IB4200's do 435 seconds at 35 amps. That works out to 4229 mah. Even my ancient Sanyo 1200 SCR's were more like 1500 mah when new. The cell manufacturers don't lie, they rate them as nominal. Bulk packs will be close to label rating, could be a little under or over. Hand selected matched ones will be the top of the heap. At 1C they could be well over rating.

[Demon-TC3]

yea my matched IB3800's peak at 4200+ at 5A charge. Awesome cells!

[Shazz1234]

I just cycled my Venom 4600 pack at 4.6 A (1C) and managed to get a peak of 4100mah which isn't all that bad considering I was thinking it would hold 4600, but hey whatcha gonna do?

[Demon-TC3]

yea its not bad and remember it will increase by...if your lucky 200Mah as you use it...

[Shazz1234]

I'm still VERY happy with the performance of the pack, just having a quick session on my driveway I immediatly heard and felt the difference in the power oi the motor. Cant wait to give it a proper run later...

I never really thought that having a better pack would instantly increase the power of the motor but I know I'm definatly wrong now... yet again.

[GSMnow]

The ultimate power you can make in any electric car is limited by the batteries. The hotter the motor and ESC you try to run, the harder the batteries need to work, so differences in cells show up bigger and bigger. Running an old stock motor, you may not see much difference, but with a low turn mod or a serious brushless setup, the battery can be the difference between blazing speed, and barely moving. I tried one of my old "practice packs" on my new Mamba Max 5700, and fresh off the charger it could not go up the slope of my driveway without tripping the low voltage cut off I had set at 5.0 volts. That same pack ran my Novak T4 ESC with a CO27 stock motor for about 3 minutes in race trim. The IB4200's not only run the CO27 stock motor setup for well over 12 minutes, they launch the car with the Mamba Max with the tires spinning, slipper slipping, and front tires hopping off of the ground for over 8 minutes. Also running the CO27 (it sucks 13.5 amps no load) right off of a battery (no esc) you can really hear how much higher the rpm is on the IB4200's vs all the other packs I have, even matched RC2400's, Orion 2400 NiCd's, and a set of Panasonic 3000 NiMh cells. An old set of Sanyo N1200-SCR actually come the closest, but are still lower revs and don't run very long at all.

[Demon-TC3]

yea, i just went to new cells about 2 weeks ago, my old cells where still very good cells but these new ones where "Rated" cells...just plain wow