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Old 11-08-2007, 11:09 AM   #16
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Originally Posted by HappyHippo View Post
Well 6 cell and brushless 3,5 or 4 turn on carpet the cars are balistic and hard to control we have tried that, and the problem then is that speedos and motors get to hot and break
Which is the reason 5cell was introduced, too many failures during racing (motors and ESC's etc, not the batteries)

As for temp cutoff's, if the cells were not being monitored individually you will always get one or more cells that get hotter than the others, if the probe is in the wrong place it would never 'see' this.

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HI all ,just wondering why the shift to 5 cells is there any benefit also i take it receiver packs would need to be fitted as well for the bECs? just more work to do anyway happy racing.

Cheers Flashgordon
The benefit is improved efficiency and reliability of the motors etc. as there is a lot less strain on them. (Raced at UK nationals all last year and I don't think there was a single motor failure)
The reduced weight of the cars allows for better handling.
This also means the cars are just as fast despite the reduced power, just take a look at my thread for BRCA videos and see the mod final!

No, you don't need a receiver pack as the voltage is 6V, the same as the BEC on any good ESC.

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Old 11-08-2007, 11:11 AM   #17
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Norway use Sorex 28R
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Old 11-08-2007, 11:13 AM   #18
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This is rediculous.

I charge at 10 amps and aim my battery's at Seaball.
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Old 11-08-2007, 11:13 AM   #19
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I believe that if people want to stay with NiMh the rules should change to 6 cells urgently.
What on earth would that achieve?

The problems with the cells always occur while charging, or just after charging

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Old 11-08-2007, 11:23 AM   #20
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HappyHippo of course the cars are dificult to drive with 3,5 or 4T motors with 6 cells. you will find out that you drive faster with a less powerful motor, because you will not have so much wheel spin.

If you change to a less powerful motor you will have less stress on batteries and you will drive longer. In indoor, duration is problably not an issue but if you are driving in a 1:8 scale track you will experience that is dificult to make the 5 minutes unless you have new batteries all the time and be gentle with your finger.

Races here are looking like 5 minutes endurance races as some pilots can not make to the final with 5 cells.

And more, one of this days you will have the some problem with power even with 5 cells because now you have 2,5T brushless motors but in the future perhaps one 2T or 1,5T allways with a lot more of stress on batteries.

Perhaps I am wrong...but perhaps not.
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Old 11-08-2007, 11:29 AM   #21
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Originally Posted by PDM View Post
HappyHippo of course the cars are dificult to drive with 3,5 or 4T motors with 6 cells. you will find out that you drive faster with a less powerful motor, because you will not have so much wheel spin.

If you change to a less powerful motor you will have less stress on batteries and you will drive longer. In indoor, duration is problably not an issue but if you are driving in a 1:8 scale track you will experience that is dificult to make the 5 minutes unless you have new batteries all the time and be gentle with your finger.

Races here are looking like 5 minutes endurance races as some pilots can not make to the final with 5 cells.

And more, one of this days you will have the some problem with power even with 5 cells because now you have 2,5T brushless motors but in the future perhaps one 2T or 1,5T allways with a lot more of stress on batteries.

Perhaps I am wrong...but perhaps not.
I've don't have any problems with that, I run 4 or 4,5 turn and the tracks we race on here are big, just a few racers use 3,5t here
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Old 11-08-2007, 11:36 AM   #22
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of course Skiddins the cells grow a lot of internal resistance, an then the harder you push them (charging or discharging) the worst they will be.

A higher internal resistance cell should be charged with a lower current (some will make the charger stop) but people keep putting 5 or 6 Amp in the charger and problably they should be putting half of that in those cells.

Look, i am not an expert in this matters I see it as comum sense.

You can look at the electric pylon racing planes foruns and you will find out that their Zapped and Matched cells (the sames that we use in cars) if they try to use the cells a second time (very high discharge rate in the first one) a lot of explosions happens.

What we are experiencing with the cars is the some problem but in a slower rate (it will not happen on the second use but problably on the 20th or so).

By the way, the solution for that problem they were trying to find it allowing the lipo cells. For some monthes now that I dont look at those foruns but I remember this.
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Old 11-08-2007, 11:50 AM   #23
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Quote:
Originally Posted by PDM View Post
of course Skiddins the cells grow a lot of internal resistance, an then the harder you push them (charging or discharging) the worst they will be.

A higher internal resistance cell should be charged with a lower current (some will make the charger stop) but people keep putting 5 or 6 Amp in the charger and problably they should be putting half of that in those cells.

Look, i am not an expert in this matters I see it as comum sense.

You can look at the electric pylon racing planes foruns and you will find out that their Zapped and Matched cells (the sames that we use in cars) if they try to use the cells a second time (very high discharge rate in the first one) a lot of explosions happens.

What we are experiencing with the cars is the some problem but in a slower rate (it will not happen on the second use but problably on the 20th or so).
You don't understand the reasons for going to 5 cell in Europe PDM.

We changed to 5 cell because:
- The battery technology had improved much quicker than the motor technology, so the cells were giving out too much voltage for the motors to cope
- We were blowing up mod motors all the time with 6 cell, BL speedos/motors would overheat because of the high voltage from the latest cells, and 7t motors were throwing winds
- 5 cell makes the car easier to drive, more fun to drive, not as quick at accelerating but faster over a whole lap

In the UK we haven't gone to 5 cell in the 27t and 19t class because these motors weren't suffering as much with the high voltage.

If we went back to 6 cell mod, then motors and ESCs would overheat again and it would only get worse as cell technology develops (so we have even more voltage)

Everyone that has tried 5 cell mod this year in Europe has really enjoyed it, I don't think you could make anyone go back to 6 cell.
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Old 11-08-2007, 11:59 AM   #24
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The problem is that we will never have batterys that are safe enough, and no manufactor will ever give a garanty that cells will not blow up due false charging
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Old 11-08-2007, 12:13 PM   #25
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Or perhaps I understand it in a diferent way Jonny Aird. I live in Europe too.

Perhaps the problem were with the blues and red controllers. If you try a green one you will have no problem. They are holding with 4 lipo cells and with very very powerful motors in 1:8 electric off road and they are holding fine. (ok with a fan on the top of them and a lot of holes in the box but they are there.) Even the blue one from 2007 cannot hold the 2,5t brushless motor with 6 cells.

I drive with lipo with the green one and everything ok. And I find out that I do not drive faster with the more powerful motor that I have. I am not a Pro and I understand this, so why would not Pro conclude the same? Why reduce the power in the cells if I can reduce the power in the motor? I would drive longer. I agree the cars are lighter and easier to drive with five cells. but they are even lighter with lipos...so.
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Old 11-08-2007, 01:30 PM   #26
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You have to be very careful when you charge the cells now.

The cells are unstable.

I have found som thing very interesting.

I have identified all the bad cells i have
and in all cases it is the cell that is on the - side off the
battery that is bad.

The current flow are going from + to -
and if the cell is very bad, the next cell to go weak
is the cell next to it in my case cell 3

This kills the cell at the -

I have the cell this way

1 2 3 4
O O O O
+........-

This is also du to solder on the - side you get allot more heat into the cell
and you have to solder faster.

I test the discharge 10A on the bad cell
to and if got very hot about 52 degree
i then turned it down to 5A and the temp
drop to about 2 degree above the rest off
the cells, but it are very easy to understand that
this cell can blow up in the car

If you charge at 2A
and discharge at 5A when at the tray, the lower amps you charge the cell the lest is the chance is
going to blow up, and the lest mV you use the bigger is the change the the charger will stop it.

But if you have a ( 0 ) volt cell in the pack, it can go on and charge forever.

and you will have to look very careful after the temp on every cell

the best will be to have a tray with temp censor to stop the charge before it blows up

Also charge at 6A and 6mV per cell ARE WAY to HIGH (If it is per cell), temp on 43 shod be ok, but the problem is that the temp
probe is on the wrong cell what cell di blow UP the ( - ) one ? this goes to the ESC

Yes i was sitting 3 m away but i didn't look at the battery.

on the LRP Pulsar i use 5A and 5 mV peak on a 4 cell pack this is 1,25 mV per cell
on the Spintec i use 5A and 1 mV and 45 degree and the bad cells are sometime cutting
on temp and sometime on peak, but mostly it cut on temp

Be careful

Take Care

Alf
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Old 11-08-2007, 01:50 PM   #27
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Old 11-08-2007, 01:58 PM   #28
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How about the rest of the world grow some balls and stop buying from the Chinese, they are wreaking havoc with our economies...
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Old 11-08-2007, 02:42 PM   #29
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Although I think the Norwegians have caved in a bit too easily over the safety aspect, remember, this 'ban' only applies to their national events, not the average club racing.

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Old 11-08-2007, 02:55 PM   #30
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Quote:
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Although I think the Norwegians have caved in a bit too easily over the safety aspect, remember, this 'ban' only applies to their national events, not the average club racing.

Skiddins
All electric activities are baned here
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