discharge "C" and duration of battery?

[carcueza]

Hello. My doubt is that a battery with more "C" of discharge has more "acceleration", that is, more "punch" but......the duration of the battery is less that the same battery with less "C" of discharge?

Thank you!!!!

[Johnnysplits]

True, more C rating does give more punch, but doesn't effect the duration. The mah rating does. More mah, more runtime.

[Cmarcan167]

The higher "C" rating makes the battery less likely to puff under hard continuos demands.

[Odd-M]

One thing to consider, if you're not running motors that draw huge amperage numbers you do not need these high "C" ratings. I'm running cheap 3S 2200mah 30C battery in my Wrath with a brushed 35t. 2,2A x 30C = 66A capacity. It's more than enough, allthough it's fairly small and weak. It would be totaly different if you race onroad with looow turn motors. I would say that 2S 5000mah, which most people tend to use in this type of rigs, don't need more than regular 20C. Yes I do have both regular batteries and more expensive with a lot of capacity, 2S 5000mah 55C and 2S 6600mah 65C for instance, but I've yet to experience any of my cars to demand such numbers. Nor have I experienced any benefits in performance from them, so I only buy regular cheap batteries from now on.

[wings_of_fire]

carcueza,

Consider two water tanks with equal capacity of 1000 liter water in them. Both the tanks have taps fitted on them. First tank has a smaller tap and the second tank has a bigger tap. Now both these taps are opened at the same time. Which tank will run out of water first?

[sniper101]

Originally Posted by wings_of_fire

carcueza,

Consider two water tanks with equal capacity of 1000 liter water in them. Both the tanks have taps fitted on them. First tank has a smaller tap and the second tank has a bigger tap. Now both these taps are opened at the same time. Which tank will run out of water first?

I'm no expert, but I would say that is highly inaccurate way of looking at it.

The ESC/motor draw determines total amperage draw (rate of discharge). The higher C is capable of discharging (providing higher amperage output) faster than a lower C battery.

Using the water tank metaphor, if both tanks(batteries) were the same size, and both had spray nozzle(motor) was capable of flowing 10 gallons per minute, one had a larger hose capable of 15gpm, and the other a hose capable of only 8gpm. Emptying at or less than 8gpm they would both drain at the same rate. Squeeze the spray nozzle harder and the smaller hose won't flow any more, but the bigger hose will drain even more water faster, at a higher volume.

[Corrupt]

Originally Posted by sniper101

I'm no expert, but I would say that is highly inaccurate way of looking at it.

The ESC/motor draw determines total amperage draw (rate of discharge). The higher C is capable of discharging (providing higher amperage output) faster than a lower C battery.

Using the water tank metaphor, if both tanks(batteries) were the same size, and both had spray nozzle(motor) was capable of flowing 10 gallons per minute, one had a larger hose capable of 15gpm, and the other a hose capable of only 8gpm. Emptying at or less than 8gpm they would both drain at the same rate. Squeeze the spray nozzle harder and the smaller hose won't flow any more, but the bigger hose will drain even more water faster, at a higher volume.

+1. It is ALWAYS a good idea to get higher C rated packs, if you can afford them. Higher C does NOT mean it discharges FASTER than a lower rated C pack. It simply means that the higher the C rating the pack has, the more amps it can provide IF the motor demands it.

Why is it a good idea to get higher rated C packs, even when you don't need it? Simple, you will work the battery a lot less than you would a low C rated pack. Plus, if you DID want to upgrade to a STRONGER system in the near future, you will quickly see the low rated C packs have a hard time sustaining the amperage demands that the stronger system demands. If you got higher rated C packs to begin with though, you'll be much more flexible in what applications your batteries can appropriately power.

I generally like to look at 30c or higher packs. But, keep in mind, many, many manufacturers lie about C ratings. Some claim to have "60c" or even "100c". Sometimes it's true, most of the time its not. Just keep that in mind.



-Corrupt

[Odd-M]

You can't look at C ratings alone. Given a 1000mah 30C against a 5000mah 30C against each other, the bigger battery should theoreticaly endure 5 times more amperage draw than the smaller one. The other fact is that none esc provided for 1/10 scale is able of even going close to the borders of what most batterys are able to provide. Manufacturers aslo tend to boost their ratings as a marketing thing. There's no norm for how they calculate this. Look at Traxxas VXL, 100A continous and 360A burst. Riiiight....

If you're racing onroad with a 4,5 turn motor at a track which makes for a lot of trottle, yes you will most likely need a lot of juice from you're battery. But for trailing and crawling, or general bashing, it's pretty useless from my point of view.

The 2S battery than pulls hardest on my basher is actually rated with far lower ratings than my more expensive ones.

[Corrupt]

Originally Posted by Odd-M

You can't look at C ratings alone. Given a 1000mah 30C against a 5000mah 30C against each other, the bigger battery should theoreticaly endure 5 times more amperage draw than the smaller one. The other fact is that none esc provided for 1/10 scale is able of even going close to the borders of what most batterys are able to provide. Manufacturers aslo tend to boost their ratings as a marketing thing. There's no norm for how they calculate this. Look at Traxxas VXL, 100A continous and 360A burst. Riiiight....

If you're racing onroad with a 4,5 turn motor at a track which makes for a lot of trottle, yes you will most likely need a lot of juice from you're battery. But for trailing and crawling, or general bashing, it's pretty useless from my point of view.

The 2S battery than pulls hardest on my basher is actually rated with far lower ratings than my more expensive ones.

That is very true. Expensive batteries aren't always the best though.. consider SPC lipos. Those are great lipos, for great prices. If you can get a 5000 20c or a 40c for a few bucks more, you should absolutely get a 40c. Your packs will last longer since you are not working them hard. You won't see a difference if your system is pulling like 20 or 30 amps. But I'd think that crawlers tend to have a fluctuating graph of amp draws as you get harder climbs, wheels in a bind, wheel spin etc.

-Corrupt

[Odd-M]

I agree, more C most certainly do not hurt. One brand I like a lot is Haiyin. They are fairly priced, gives good power to the wheels and cells seem to have pretty equal voltage at lipo-cut. Can't say that last thing about all my packs...

I'read that some cheaper brands have higher internal resitance, making them very hot and sucks the juice out of them under heavy loads. Even if they are rated as state of the art. As with all sort of things, you tend to get what you pay for.

[Corrupt]

Yes, you do get what you pay for when it comes to lipos (most of the time).

-Corrupt

[wings_of_fire]

sniper101,

I had not finished explaining it completely. I was waiting for an answer from carcueza.

[Olle P]

I see it this way:

Assume you use two batteries the same voltage and capacity.
One has a C-rating (continuos/peak) of 20/30 and the other 30/50.
Your actual use in the crawler is 5/20C.

Will you notice a difference? Most likely not.
Will there be a difference? I think the higher rated battery will survive more cycles (charge/discharge) before losing to much capacity.

[Corrupt]

Originally Posted by Olle P

Will you notice a difference? Most likely not.
Will there be a difference? I think the higher rated battery will survive more cycles (charge/discharge) before losing to much capacity.

Precisely.

-Corrupt

[carcueza]

Hello. Thank you very much to everybody!!!!!
But there is one thing that I don't understand completely....
If I have two batteries of the same mAh but different C (20/30 one and the other 40/90) Theoretically the duration will be the same, but if my motor need, in one moment, more "punch" the second battery could give my this "extra punch" because it has more C.....but when the battery gives more punch and the battery spend more mAh so the duration of second battery, with more C, will less than de first battery (with less C).

Thank you!!

[Johnnysplits]

Originally Posted by carcueza

Hello. Thank you very much to everybody!!!!!
But there is one thing that I don't understand completely....
If I have two batteries of the same mAh but different C (20/30 one and the other 40/90) Theoretically the duration will be the same, but if my motor need, in one moment, more "punch" the second battery could give my this "extra punch" because it has more C.....but when the battery gives more punch and the battery spend more mAh so the duration of second battery, with more C, will less than de first battery (with less C).

Thank you!!

No. The higher C will deliver more amps with less voltage sag than the lesser C rated battery under equal load. The lesser C rated battery would also develop more heat under the same load. However, they would still have the same duration at the same mah.

[Corrupt]

Originally Posted by Johnnysplits

No. The higher C will deliver more amps with less voltage sag than the lesser C rated battery under equal load. The lesser C rated battery would also develop more heat under the same load. However, they would still have the same duration at the same mah.

This.

When your battery cant handle it, you'll know. Things like excessive heat, very fast voltage drop and puffing of the lipo will occur.

Think of C as a straw in a water bottle. The amount of water in the bottle is the batterie's MAH and the C rating is the thickness of the straw. Now, lets take bottle 1 as 20c and bottle 2 as 40c. If you (the motor) try to demand a lot of water from that water bottle, then you'll easily meet that demand with the larger straw from the 40c bottle #2. Bottle #1 with the 20c rating and the smaller straw will struggle to deliver the water (amps) the motor is demanding.

Now, if you go and actually run those two lipos, with the 20c not being up to the task and the 40c being up to the task, you'll actually get less safe runtime becasue the voltage on the 20c lipo will drop quickly, triggering LVC.

-Corrupt

[Olle P]

What Corrupt says applies primarily to high power usages, such as racing.

A slow crawler is just unlikely to hit the battery's limit in the first place, and if it does it's only for a short while.
The battery won't get hot and it's typically just not a problem!

Where the C-rating does matter for a crawler is when you use small batteries, typically with capacity <1,000 mAh.
If you combine this battery with a "hungry" motor you might end up demanding >50A peak and thus need a battery with an appropriate peak rating.
The typical current consumption will stay <4A and is not an issue.