RCCrawler Forums

Pappy · 12-18-2009, 03:42 PM

Is there a spec. or a definitive way to guage how much amperage a motor can use? I run Berg axles with Novak 45T's (Two of course) and I'm looking to get some more punch with lipos with better discharge capabilies. But how much can they actually benifit from? I see 50C's putting out around 63 amps, and figure only a good handwound could use that, correct?

squatch71 · 12-18-2009, 04:51 PM

I have wondered that same question, but didn't know how to word it.

thanks Pappy...

JohnRobHolmes · 12-18-2009, 05:16 PM

The higher the discharge rate, the higher the voltage will be under load. It NEVER hurts to use a better battery. Even if the motors don't need all the amperage that the battery can dish out, you can get more punch from the higher voltage.

Pappy · 12-18-2009, 05:52 PM

I was looking to jump from a 20C to something like a MaxAmps 50C pack....Just didn't want to waste money if there in no noticable gains.

Team X · 12-18-2009, 06:34 PM

You can use this:
http://www.powerwerx.com/tools-meter...dc-inline.html

or you can do some math to get a aprox avg amp load

if you have a 2000mha bettery and time how long it takes you to kill the battery when driving that will give you a idea of what your amp load is

EX

it will take a 2 amp load one hour to drain a 2000mah battery
it will take a 1 amp load one hour to drain a 1000mah battery
ect..

so if you have a 1500mah battery and you battery dies after 30 min's then the avag amp load is 3 amps (beacuse it would take a 1 amp load to drain the battery in one hour)

oldhippie · 12-18-2009, 07:45 PM

Average load means nothing!:? What ya want to know is the highest burst load. Ya need a big battery or power supply, an amp meter hooked in line, stall the motor and read the amps. Then get a battery with at least that discharge ability. Since I don't have all that stuff I try and find a battery with something near 40amps constant discharge rate.
mah x C divided by 1000 = amps 1100mah x 35c / 1000 = 38.5 amps 850 x 45c / 1000 = 38.25 amps 1500 X 20c / 1000 = 30amps

And yes I can tell the difference.

JohnRobHolmes · 12-18-2009, 08:48 PM

Quote:

Originally Posted by Pappy

I was looking to jump from a 20C to something like a MaxAmps 50C pack....Just didn't want to waste money if there in no noticable gains.

The gains may not be noticeable- depending on your current battery. It depends on the gearing and vehicle weight, motor condition and build, tire diameter, traction, old battery condition, and probably 100 more variables too.

So what battery are you currently running? That is the only way to know if the "gain" will be noticeable.

Pappy · 12-18-2009, 09:05 PM

Quote:

Originally Posted by JohnRobHolmes

The gains may not be noticeable- depending on your current battery. It depends on the gearing and vehicle weight, motor condition and build, tire diameter, traction, old battery condition, and probably 100 more variables too.

So what battery are you currently running? That is the only way to know if the "gain" will be noticeable.

CKRC 3S 11.1V 1290mah 20C.....Tekin FXR's(2)....Castle BEC........Novak 45T's (2)

I'd like to possibly get a MaxAmps of similar physical size with alot more punch if possible.

oldhippie · 12-18-2009, 09:30 PM

The maxamps 1290 (or any of them) doesn't list a "constant" C #, only a burst #. I would guess the ckrc 20c is a constant #. I would also guess it has something around 40c burst so I'm not sure ya would see a big difference. But without real #s, Who knows?

Pappy · 12-19-2009, 01:25 AM

Quote:

Originally Posted by oldhippie

The maxamps 1290 (or any of them) doesn't list a "constant" C #, only a burst #. I would guess the ckrc 20c is a constant #. I would also guess it has something around 40c burst so I'm not sure ya would see a big difference. But without real #s, Who knows?

Does this help? Got this off of the detailed description at Max Amps.

1290mah Capacity

11.1 Volts
30mm X 49mm X 37mm
50C - 710 surge watts(64.5 amps)

111 grams
5C Fast Charge Capable

JohnRobHolmes · 12-19-2009, 06:19 AM

5c charge rate, they are probably 25c constant cells.

Pappy · 12-19-2009, 11:31 AM

Quote:

Originally Posted by JohnRobHolmes

5c charge rate, they are probably 25c constant cells.

Ok, I'm confused.......I thought the 50C meant 50 amp constant????? And then 64.5 watts burst. Right? I'm trying to figure this all out.....Sorry for all of the questions.:?

JohnRobHolmes · 12-19-2009, 12:09 PM

No, maxamps doesn't go with the industry standard ratings. They use burst (surge) amperage as the only rating, and don't list continuous duty or time of surge.

oldhippie · 12-19-2009, 05:06 PM

Quote:

Originally Posted by Pappy

Ok, I'm confused.......I thought the 50C meant 50 amp constant????? And then 64.5 watts burst. Right? I'm trying to figure this all out.....Sorry for all of the questions.:?

No 50c is a Burst surge number like it says (50C - 710 surge watts(64.5 amps))
1290mah x 50c / 1000 = 64.5 amps
65.5 amps x 11.1 volts = 710.95 watts
That is what the battery can supply for a short burst (I bet nano sec short) at maximum output. It really doesn't mean much because there is no standard test for it that I'm aware of. What ya really want to know is the constant C # that does have a standard test. The burst # will be much higher than the constant #. Max amps doesn't list constant #s so there is really no way to compare their batteries to those that do list constant #s. I'm not saying maxamps aren't good batteries because I really have no idea.

Pappy · 12-19-2009, 06:05 PM

So who offers good easy to use ratings on their batteries?:?

clockworks · 12-20-2009, 01:16 AM

Quote:

Originally Posted by Pappy

So who offers good easy to use ratings on their batteries?:?

Some manufacturers label their packs with two "C" numbers - continuous and burst, while some just give one number. If just one number is on the label, assume that it's the burst rating.

The thing is, some of these ratings seem to be totally made up.
I fly electric planes, where the aim is usually to get the maximum power for the minimum weight. Power (watts) is amps times volts, so I need to use packs that will supply the right amount of current, without the voltage sagging under load.
I test all the electronics under load, using a watt meter.

By varying the propellor size, I can alter the amp draw at full throttle. For a 10C 800mAH 2s pack, I find a prop that pulls 8amps.
With some packs, the voltage drops below 7v. With others, it stays above the nominal 7.4v.
Same amps, less voltage, means less power.

It seems that some manufacturers (should that be resellers?) rate their packs for the discharge rate at the low voltage cutoff (3.2v) , while others rate them at nominal voltage (3.7v).

Two brands that rate their packs correctly are Hyperion and LoongMax.

Manning · 12-20-2009, 07:42 AM

Quote:

Originally Posted by clockworks

.....

The thing is, some of these ratings seem to be totally made up.
......

So true.

Basically, don't buy used or old batteries (even if unused), and don't buy the cheapest batteries, and you'll be fine.

KBrog · 12-20-2009, 09:15 AM

Quote:

Originally Posted by JohnRobHolmes

No, maxamps doesn't go with the industry standard ratings. They use burst (surge) amperage as the only rating, and don't list continuous duty or time of surge.

Thats good to know. Not that I was in the market for a ( cost so much Id have to get a loan ) Maxamps battery anyway, but if I were to buy form them I know not to trust the numbers. I bought a 20c battery from integy and when I opened it up, It said 20c burst, 15c cont.,,, I was pissed. Ill just keep buying from hobbyking, when you order a 20c,,,,,you get a 20c. I know all this sounds negative. I dont like it when a company lists a product as something its not.

JohnRobHolmes · 12-20-2009, 09:22 AM

Most companies do list the continous as the rating. I wasn't aware that integy did not. I stopped listing my burst rates because it depends so much on tempurature. In a crawler the cells don't get warm enough to be able to hit the burst amperages without the voltage sagging hard. Best temp is around 110 to 120f for lipo.

nismotuningrocks · 12-20-2009, 09:26 AM

Quote:

Originally Posted by KBrog

Thats good to know. Not that I was in the market for a ( cost so much Id have to get a loan ) Maxamps battery anyway, but if I were to buy form them I know not to trust the numbers. I bought a 20c battery from integy and when I opened it up, It said 20c burst, 15c cont.,,, I was pissed. Ill just keep buying from hobbyking, when you order a 20c,,,,,you get a 20c. I know all this sounds negative. I dont like it when a company lists a product as something its not.

I agree with you Karl, I have noticed that some of the domestic battery makers use some tricky marketing to sell batteries, some people may not trust batteries from Hong Kong, but they can go on buying batteries that cost twice as much haha

12-18-2009, 03:42 PM	#1
Pappy Rock Crawler Join Date: Jan 2006 Location: Southwestern Pa. Posts: 866	Usable amperage...... Is there a spec. or a definitive way to guage how much amperage a motor can use? I run Berg axles with Novak 45T's (Two of course) and I'm looking to get some more punch with lipos with better discharge capabilies. But how much can they actually benifit from? I see 50C's putting out around 63 amps, and figure only a good handwound could use that, correct?

12-18-2009, 07:45 PM	#6
oldhippie I wanna be Dave Join Date: Feb 2009 Location: 20 miles southeeast of downtown Sacramento Posts: 2,373	Average load means nothing!:? What ya want to know is the highest burst load. Ya need a big battery or power supply, an amp meter hooked in line, stall the motor and read the amps. Then get a battery with at least that discharge ability. Since I don't have all that stuff I try and find a battery with something near 40amps constant discharge rate. mah x C divided by 1000 = amps 1100mah x 35c / 1000 = 38.5 amps 850 x 45c / 1000 = 38.25 amps 1500 X 20c / 1000 = 30amps And yes I can tell the difference. Last edited by oldhippie; 12-18-2009 at 07:57 PM.

12-18-2009, 09:30 PM	#9
oldhippie I wanna be Dave Join Date: Feb 2009 Location: 20 miles southeeast of downtown Sacramento Posts: 2,373	The maxamps 1290 (or any of them) doesn't list a "constant" C #, only a burst #. I would guess the ckrc 20c is a constant #. I would also guess it has something around 40c burst so I'm not sure ya would see a big difference. But without real #s, Who knows? Last edited by oldhippie; 12-18-2009 at 09:39 PM.

12-18-2009, 04:51 PM	#2
squatch71 I wanna be Dave Join Date: Sep 2008 Location: four o six Posts: 2,101	I have wondered that same question, but didn't know how to word it. thanks Pappy...

12-18-2009, 05:16 PM	#3
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	The higher the discharge rate, the higher the voltage will be under load. It NEVER hurts to use a better battery. Even if the motors don't need all the amperage that the battery can dish out, you can get more punch from the higher voltage.

12-18-2009, 05:52 PM	#4
Pappy Rock Crawler Join Date: Jan 2006 Location: Southwestern Pa. Posts: 866	I was looking to jump from a 20C to something like a MaxAmps 50C pack....Just didn't want to waste money if there in no noticable gains.

12-18-2009, 06:34 PM	#5
Team X Newbie Join Date: Mar 2006 Location: Denver Posts: 45	You can use this: http://www.powerwerx.com/tools-meter...dc-inline.html or you can do some math to get a aprox avg amp load if you have a 2000mha bettery and time how long it takes you to kill the battery when driving that will give you a idea of what your amp load is EX it will take a 2 amp load one hour to drain a 2000mah battery it will take a 1 amp load one hour to drain a 1000mah battery ect.. so if you have a 1500mah battery and you battery dies after 30 min's then the avag amp load is 3 amps (beacuse it would take a 1 amp load to drain the battery in one hour)

12-19-2009, 06:19 AM	#11
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	5c charge rate, they are probably 25c constant cells.

12-19-2009, 12:09 PM	#13
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	No, maxamps doesn't go with the industry standard ratings. They use burst (surge) amperage as the only rating, and don't list continuous duty or time of surge.

12-19-2009, 06:05 PM	#15
Pappy Rock Crawler Join Date: Jan 2006 Location: Southwestern Pa. Posts: 866	So who offers good easy to use ratings on their batteries?:?

12-20-2009, 09:22 AM	#19
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	Most companies do list the continous as the rating. I wasn't aware that integy did not. I stopped listing my burst rates because it depends so much on tempurature. In a crawler the cells don't get warm enough to be able to hit the burst amperages without the voltage sagging hard. Best temp is around 110 to 120f for lipo.

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