Lipo C rating question

[papabash]

I have been under the understanding that with crawlers there was no need for high C ratings on the lipos, since we are not running them fast enough to need the higher discharge. I run 25-30 C lipos on my 2.2 and have had no problems doing so. I have noticed, though, on the1.9s that a lot of people seem to be running 45C batteries. Is this because these little guys run harder/faster due to their size, or ????? Is it necessary to run higher C rated lipos on 1.9s? I am currently running a Mongoose system, as is my son, but I have a 17t Crawler Mafia motor/Mamba micro pro coming, so need to know for both systems.
Thanks!

 

[JeremyH]

It all depends on the mAh of the battery. I have run a 20C/40C 250mAh on my MRC (with CM 17T motor) and quickly killed them (puffed and hissing). Switched to a 325 45/90C and they perform nicely.

 

[rock hard]

A larger mAh battery will last longer.
I have a 20c 800 mAh pack that I can run 4 courses [5 gates]with no worries.
But its kinda long and doesnt fit well.

The T.Power 325's are super small,and I can get 2 courses with one battery [5 gate courses]

It is my opinion though that you need to balance a smaller mAh battery more often.
I usually dont on my 1,000 3s or 800 2s
But my 500 3s and my 325 2s seem to get a gap decent gap in voltage between cells after each use.So I balance every other charge to keep them close.My large mAh I would balance much less often as they stayed fairly close cell to cell.

 

[tommygunzgrafix]

If I remember right the C discharge rate times the mah than divide by 1000 is how many amps you can draw from the pack without damage. So like Rock Hard said we tend to run smaller mah batteries due to the size so would need to run a higher C rating. So a 500mah (20c) battery would have a 10amp continuous discharge, but a 1000mah 20c would be at 20amps continuous. So to achieve this same discharge rating you would need a 40C on the 500mah where as 20c (10 amp draw limit continuous) might be too low. Anyone please correct me if I am wrong.

Now I have not tested my system on the MRC (novak mongoose 18.5) to see how much the amp draw is on it. But I would think if you get bound up between rocks you could put a strain on the battery and it might go bad if you put too much of a load (can be avoided by letting off the throttle though). If someone has tested or can view the info on their computer this might shed some light on how much draw we put on these things. I mean 10amps continuous might be enough but with the weighted tires and going up an incline I just don't know how many amps the esc is pulling under that kind of load. It could be very little but I have not tried to test it.

Personally I have a 900mah 15c that I run on the back axle so going by above thats 13.5 amps continous. Works good and get lots of runtime. I am looking for some 3s 500mah now. So looking for at least a 25C or higher.

 

[tommygunzgrafix]

I have been under the understanding that with crawlers there was no need for high C ratings on the lipos, since we are not running them fast enough to need the higher discharge. I run 25-30 C lipos on my 2.2 and have had no problems doing so. I have noticed, though, on the1.9s that a lot of people seem to be running 45C batteries. Is this because these little guys run harder/faster due to their size, or ????? Is it necessary to run higher C rated lipos on 1.9s? I am currently running a Mongoose system, as is my son, but I have a 17t Crawler Mafia motor/Mamba micro pro coming, so need to know for both systems.
Thanks!

With your 25-30C batteries how many Mah are they. I know on my onroad/drift car I run 25C 4000mah batteries. It can run a continuous 100amp draw. With my drift tires on I am only hitting about 30-40 amps continuous but if I put rubber back on it jumps up to like 80 amps or so. If you are running a 2000mah battery thats 25C you can run a 50 amp draw continuous and never have problems. Which might be why its fine on your 2.2.

 

[papabash]

With your 25-30C batteries how many Mah are they. I know on my onroad/drift car I run 25C 4000mah batteries. It can run a continuous 100amp draw. With my drift tires on I am only hitting about 30-40 amps continuous but if I put rubber back on it jumps up to like 80 amps or so. If you are running a 2000mah battery thats 25C you can run a 50 amp draw continuous and never have problems. Which might be why its fine on your 2.2.

My 2.2 batteries are 1500mah, waaaaaay bigger than I intend to run next year, but they were what I had on hand this season. With your above formula, that would explain why they were okay with the lower rating.

 

[rock hard]

papa,I know that me and 2 other drivers in our club,all running 17t mafia's ar having good results with the 325 45/90c thunder power.

and 2 drivers in the south tx club also like that battery.
you should be good to go. I would get one bettery for each course.
Thats the best way to do it IMO.

 

[papabash]

A larger mAh battery will last longer.
I have a 20c 800 mAh pack that I can run 4 courses [5 gates]with no worries.
But its kinda long and doesnt fit well.

The T.Power 325's are super small,and I can get 2 courses with one battery [5 gate courses]

It is my opinion though that you need to balance a smaller mAh battery more often.
I usually dont on my 1,000 3s or 800 2s
But my 500 3s and my 325 2s seem to get a gap decent gap in voltage between cells after each use.So I balance every other charge to keep them close.My large mAh I would balance much less often as they stayed fairly close cell to cell.

I understand the mah/run times, it's the discharge rate I'm trying to figure out. I did not know that lower mah packs needed to be balanced more often, though. I normally balance my comp packs every time they're charged, so that's not a problem, but good info anyway. In your experience, what is the minimum C rating I can get by with running your 17t motor? I want to stay in the 325-500mah range.

 

[papabash]

If I remember right the C discharge rate times the mah than divide by 1000 is how many amps you can draw from the pack without damage. So like Rock Hard said we tend to run smaller mah batteries due to the size so would need to run a higher C rating. So a 500mah (20c) battery would have a 10amp continuous discharge, but a 1000mah 20c would be at 20amps continuous. So to achieve this same discharge rating you would need a 40C on the 500mah where as 20c (10 amp draw limit continuous) might be too low. Anyone please correct me if I am wrong.

Good info here, thanks! I wasn't aware of this formula, what you are saying makes sense. I have some 500mah 20c lipos (both 2s and 3s) that I was hoping to run, but maybe that isn't such a good idea now.

 

[papabash]

I have run a 20C/40C 250mAh on my MRC (with CM 17T motor) and quickly killed them (puffed and hissing). Switched to a 325 45/90C and they perform nicely.

That's a pretty convincing reason to run higher discharge rates!

 

[papabash]

papa,I know that me and 2 other drivers in our club,all running 17t mafia's ar having good results with the 325 45/90c thunder power.

and 2 drivers in the south tx club also like that battery.
you should be good to go. I would get one bettery for each course.
Thats the best way to do it IMO.

Good enough for me, I'll get some ordered! "thumbsup"

 

[tommygunzgrafix]

Ya the lower your MAH is the higher your C rating needs to be. Those packs that are Rock Hard is talking about is around 14 amps continuous and a burst of 28 amps by my formula. I am thinking over 13 amps is where you want to be or a good starting point. My battery I run is just over 13 but I am also running full brushless which might have a lower draw. So just need to figure out how many MAH of a pack your going to run than work the formula to find the C rate to get you in the 13-14 rate. Of course the higher the better.

You can try your 500mah 20c but thats only 10 amps continuous so could go either way, Try at your own risk lol. The 20c 250mah is only a 5 amp continuous and most likely the reason for the quick puffing.

 

[papabash]

You can try your 500mah 20c but thats only 10 amps continuous so could go either way, Try at your own risk lol.

Think I may shoot an email to Novak about that first! If they will work, I'll give them to my son to run till he can upgrade later.

 

[JeremyH]

That's a pretty convincing reason to run higher discharge rates!

Yep, agreed! Those smaller, lower discharge packs were only putting out about 10A max. These 45/90C 325mAh TPs, put out about 30A max.

 

[skid]

Also keep in mind what your servo draws. I know my old hitec 5995 had a note it can draw up to 5 amps. So add that to the mix when bound up