Mosc_007

Not wrong. I am almost too scared to try it. Although the temperature sensor will stop the charge if the cell temperature gets too high.

Just in case anyone doubts what Sanyo have said. Here is the RC3600HV Data sheet.

Have a look in the small box for the Charge and Discharge Curves.


Charles

Mosc_007

Obviously you have not looked at the IB4200 Data sheet from Intellect. They DO state the Maximum Charge current is 1C. Also, GP Data sheets say the same thing. Max Charge current of 1C...... I have done my homework. After buying two matched sets that were destroyed I started looking real hard at Data sheets to see what I wanted to use.

I can post the Data sheets if you would like to see them.

It's the battery Matchers that are telling you to charge at 6 amps. NOT the manufacturer.


Charles

Mosc_007

Exactly. Imagine the damage that is done to the cell at 35 Amps continious discharge. From what I have read 80 Degrees C starts to damage the cell.

Maybe this is why Cells from several years ago were always ok after matching. They only used a 20 Amp discharge to Match them.


Obviously during racing the current can reach MUCH higer. But it's only short bursts. Not continious.


Charles

Mosc_007

It's not normal according to the Data sheet on the Intellect 4200 Battery. They say Minimum 4200 and Typical 4200.

And looking at the discharge curves. At 840mA discharge it is about 4620. At 4200mA,12600mA and 30000mA it is about 4200. And at 60000mA it is about 3150 mA.

Obviously the 60 Amp discharge destroyed the cell.


At 30 Amp discharge it is almost completly under 1.2 volts over the whole discharge cycle. Even 12600mA discharge is almost always under the 1.2 volts. It's only when it drops to 4200mA that it starts to stay above the 1.2 volts untill about %80 discharged.


Charles

mangoman

iTrader: (11)

Well if you say thats the case thats fair enuff, the battery manufacturer will err on the side of caution to protect their reputation.

Back 2 years ago people charging at over 5A were looked at as crazy or rich (cause they could afford to buy new batteries on a regular basis). If you want to be competitive today then you will have to charge 4200s at 5.5 to 6 Amps (especially in on-road).

If you want to have slower equipment then that is your perogative, although i forgot that you are using the older 3600s and i suspect charging at 5Amps would be about the limit anyway. Back 2 years ago if you charged over 5 Amps you were considered crazy or rich.

Mosc_007

This is the strange thing. Back when I used Sanyo RC3000 Cells I charged them at 5 Amps. And they were NEVER harmed and Never got too hot.

It seems like it's these NEW, Cheap Chinese cells that are heating up a lot quicker during charging and being damaged at high charge currents. Like I said I had to drop the GP's and IB's to 0.75C to stop them cutting out on over temperature during charging.

Thats why I was surprised that the RC3600HV were only 47 Degrees at a 1C charge. After charging GP3700 and IB4200 at 1C they got too hot and cut out from over temperature during charging.


Charles

Mosc_007

Thats what I dont understand. Why take a high risk of damaging the cells when you can charge them safely and just use a slightly higher Gear Ratio to componsate for slightly lower cell voltage. The end result is the same speed. And since the cells are such high in capacity these days you wont risk flattening them by increasing Gear Ratio and drawing more current from the battery. I guess the side effect of that is the Motor now starts to heat up more. But whats cheaper. A new motor or new Cells ?


The Onroad track I am considering getting back into has a Max cell Capacity of 3800 anyway. So the 4200's are not legal to run with on that track. I wonder what the reason behind this is...... Maybe it's to stop the people who can afford new batteries regular from dominating the race ?... Obviously from what people say the Matched 4200's do perform very well. But it seems not for a large number of races.


Charles

Mosc_007

Another piece of information I have seen for NiMH batteries is a graph showing the Life of the battery against the Discharge voltage.

It starts off around 1000 charges when only discharged to 1.2 Volts per cell. And when you discharge down to 0.9 Volts per cell it drops to around 200 charge cycles.


Charles

waOscar

This is my take on WHY?

You buy fast motors, you look after them for maximum performance.
You buy high number cells, you pump every last drop into them.
You gear the car to the edge.
or you don't compete at the pointy end of stock class.

You buy from local hobby shop, when it shits itself you ask politly if there is some kind of warranty.

I have had a higher number of cell failure with 4200 batteries, but it is no problem, because my local hobby shop stocks Harris RC cells and has always replaced dead cells.

Birky

iTrader: (1)

Have you really done your homework because the datasheet for the latest GP cells (4300s) states that Fast Charge of between 2 and 6 amps.

Available here: http://www.gpbatteries.com.hk/pic/43...RS5050rev2.pdf

Mosc_007

Ok, You got me on that one.

When I downloaded the data sheets from GP the 4300's were not available. The IB4200 Definatly says 1C. And the GP3700 also says 1C.


Charles.

Mosc_007

Most of the Racers local to me are 540 class. That means a $20 Motor.

What about if they die after say only 10 races ?. Do they still replace them ?


Charles

Mosc_007

I just did my first 10 Amp discharge test on my "Untouched" RC3600HV's.

I was expecting them to have a higher average voltage than the "Untouched" GP3700's during the discharge but I certainly was not expecting them to be higher than the "Untouched" IB4200's I have. Usualy a higer capacity cell will always have a higher average voltage at the 'same' discharge current.

I have 2 "Untouched" IB4200 Stick packs.

The "Untouched" RC3600HV cells at a 10 amp discharge had a higher average voltage than One of my "Untouched" IB4200's and lower than the other untouched one.

I was expecting them to be slightly higher than what I achieved. But I noticed on Sanyo's data sheet that they let the cells sit for 1 Hour before their discharge test. This would explain why they were slightly lower than Sanyo's figures.

I know this will cause a great deal of Argument but its a FACT that NiMH cells have a Higher Cell voltage at Lower Temperatures. I did the 10 Amp discharge test a few minets after charging. Thus the pack was Hot.

I Know that all the experts say you should run a HOT pack that is peaked just before the race starts. But their is a GOOD reason why they say that.

When a pack is just removed from the charger the terminal voltage is quite High. That means you get a real BIG kick off the start line.

BUT, What it also means is since the cells are Hot the average voltage thruout the whole race will be lower.

You get a BIG punch for about the first 30 seconds untill the cells stabalise then the average voltage is lower because of the higer cell temperature.


Another thing I noticed about my 2 "Untouched" IB4200 Stick packs. One has a slightly lower capacity than the other. I dont understand why but the lower capacity cell has the higher average voltage during discharge....


I know this is probably all useless information for anyone that uses Zapped and Matched Cells. But it does show the quality of the cell. Even though the Sanyo doesn't compete with Zapped and Matched IB4200's you will find it will be a far better battery as time goes by.

As I found with my RC3000's they were always at Max capacity and never failed. And they were Zapped and matched sets. Matched at 20 Amps though.


Charles

Mosc_007

A small peice of evidence that most people can understand that supports the fact that NiMH and NiCD cells have a Lower cell voltage at higher temperatures is the exact reason why -ve Delta V detection on chargers work.

The reason a Cells voltage drops when its fully charged is because the Cell starts to get HOT. And this increase in temperature is what cause the terminal voltage to fall which is how the -ve Delta V detection works.


Charles

Z-Mann

check out the data on cell 6, is this normal ????