MaxAmps Race Edition Lipos

[sikeston34m]

The 150C rating is ludicrous considering current technology.

Let's just run some numbers. Simple Math.

We have a 150C 6500 mah Lithium Polymer cell.

At a 975 amp discharge rate, each cell is capable of 4095 watts of power.

If we discharge our fully charged cell at the 150C discharge rate, it will be fully drained in 24 seconds. (If anyone is interested in the formula for calculating any of this, I'll post them up.)

I am a Refrigeration/Maintenance Engineer for a Distribution Center here in Missouri.

It's very common for me to deal with Techs and Sales Reps from industrial battery companies such as IBP and Deka.

Batteries have always fascinated me, so I ask alot of questions and stick my head in the books.

Here is a comparison for you. The battery in question is a 36 volt 1000ah lead acid Industrial Truck battery weighing in at 2850 pounds.

Each main power lead is about as big around as a fat cigar. Cross sectional area comparable to a Nickle.

It takes a well co-ordinated forklift driver about 6 hours to drain one of these batteries. Obviously alot of energy.

The question that I posed to IBP and Deka Techs:

What is the maximum discharge rate limit before damage occurs?

Answer: Right around 750 amps. It is at this point, it blows the jumper bars off the cells.

Jumper Bars are the intercell connections. Each unit is made up of 18 - 2 volt cells connected in series. Total of 36 volts.

They use pairs of jumper bars to jump from one cells positive posts to the next neighboring set of negative posts.

EACH jumper bar is around 2" wide and 1/2" thick and about 6" long. They are made of lead.

I've witnessed several accidents where the main power leads were crush/pinched to the point where a dead short condition occured.

Never have I seen the jumper bars blow off, but a battery this size can discharge enough amps to snap 1/0 leads in a shower of sparks. I have seen this happen. It's quite scarey.

Now, back to the 150C rating. We are going to discharge a 6500mah Lipo Pack at 975 amps continuous?

How are we going to test that since the entire discharge process will only last 24 seconds?

These numbers are off the scale and highly impossible IMO.

[thzero]

Go for it. Better to be more transparent than the next guy. Formulas, unless wrong, are hard to argue with. Numbers and claims can always be manipulated.

Originally Posted by sikeston34m

If anyone is interested in the formula for calculating any of this, I'll post them up.

[sikeston34m]

Originally Posted by thzero

Go for it. Better to be more transparent than the next guy. Formulas, unless wrong, are hard to argue with. Numbers and claims can always be manipulated.

Each cell is 4.2 volts and if we discharge at 975 amps, we get 4095 watts.

4.2v X 975amps = 4095 watts (Note: this would make a 4S pack, capable of 16,380 watts of power.

1 electric horsepower = 746 watts of power

This would make a single 4S pack capable of producing 21.96 horsepower!

22 electric horsepower would not only start your car, but it would be enough to push a small car fairly well.

The Industrial Lift Trucks I mentioned earlier have a 6.6kw drive motor. That's less than 9 horsepower and the truck weighs almost 10,000lbs. Top Speed of 9.5 mph, but still ALOT of weight.

All Batteries have an amp hour rating or on the smaller types of batteries we use, a mah rating.

Mah rating is amp hours divided by 1000. Since Mili means 1000.

A 6500 mah pack can also be called 6.5 amp hours.

The "hour" term is added to show how much amp draw it can sustain in 1 hour. A 6.5 amp hour pack can hold a 6.5 amp discharge for 1 hour.

As long as we know this, we can play with the numbers and calculate how long the pack can sustain any rate of amperage discharge.

The same pack can sustain a 1 amp discharge for 6.5 hours.... and so on.

Now, how do we calculate how long it can sustain a 975 amp discharge?

6.5 amp hour pack / 975 amp discharge X 60 (discharging minutes) X 60 (discharging seconds) = How long the charge will last at that level of discharge.

6.5 / 975=.006666666666666666666666667 X 60 = 0.4 X 60 = 24 seconds

You can play with this formula any way you like, for any size pack, for any amp draw rate.

So, in conclusion. If the 6500mah of charge ONLY lasts for 24 seconds. This should change the warranty to pretty much an unconditional warranty as far as the discharge rate is concerned.

No more should anyone hear "Well your gearing was wrong and it was too much load on the pack".

Because evidently, if you don't discharge the ENTIRE charge in less than 24 seconds, you are safe within the confines of the discharge rating.

I'm very sure this kind of amperage is enough to smoke and cook every FET from the power board of ANY ESC if the esc fails and the powerboard goes into runaway meltdown.

[gixxer]

Originally Posted by sikeston34m

So, in conclusion. If the 6500mah of charge ONLY lasts for 24 seconds. This should change the warranty to pretty much an unconditional warranty as far as the discharge rate is concerned.

No more should anyone hear "Well your gearing was wrong and it was too much load on the pack".

Because evidently, if you don't discharge the ENTIRE charge in less than 24 seconds, you are safe within the confines of the discharge rating.

That is the exact point I was making on the car action site. Cant see anymore complaints about gearing.