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Old 12-06-2007, 09:48 PM   #226
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I have a good felling we'll find out in the next 72 hours

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will the SP esc have the correct lipo cut-off?
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Old 12-06-2007, 09:48 PM   #227
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JB please spare my pack and send me yours lmao

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Mine too!!
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Old 12-06-2007, 09:58 PM   #228
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I have a good felling we'll find out in the next 72 hours
let me know!!
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Old 12-07-2007, 06:30 AM   #229
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Unfortunately I've got ugly news:

When set to "Value 1: Lipo/NiMH Automatic" mode, the LRP Sphere Competition We have here in our office DOES NOT cut off correctly for Lipos. It drug a pack all the way down to 3.5v (Should cut off at 6.0v or higher) before it cut off, and after the pack rebounded to 5v it allowed the motor to run again.

Until this issue is fixed, CORE lipos will not be warranted when used with these ESCs.

I'm not sure if it's a glitch/mistake in the software, or maybe LRP doesn't know what the critical lipo cutoff voltage should be, but this could get very ugly, very expensive, and happen very fast for a whole lot of folks running them with lipos.

This was one test with one unit, but this one unit (triple checked it was on the correct setting) just killed a lipo pack dead on my bench.
I started a thread on Rcracechat in the UK about this and I hope you don't mind, I've quoted the info from you on there.

Here is a quaote of one of the replies;

Quote:
Hi guys,

Quote from Reto at Nosram/LRP on the matter:

'That is not very specific there... our LiPo shutdown function is not at a pre-given voltage, it takes currents into consideration as well because simply shutting of at 6.0V results in many false shutdowns because the packs voltage does drop below 6.0V for a very short period of time during hard acceleration even if the pack is only half empty.'

I haven't had any reports of any failures of LiPo packs when used with the Nosram speedo.

James
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Old 12-07-2007, 08:58 AM   #230
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Quote:
Originally Posted by Shawn Palmer View Post
Unfortunately I've got ugly news:

When set to "Value 1: Lipo/NiMH Automatic" mode, the LRP Sphere Competition We have here in our office DOES NOT cut off correctly for Lipos. It drug a pack all the way down to 3.5v (Should cut off at 6.0v or higher) before it cut off, and after the pack rebounded to 5v it allowed the motor to run again.

Until this issue is fixed, CORE lipos will not be warranted when used with these ESCs.

I'm not sure if it's a glitch/mistake in the software, or maybe LRP doesn't know what the critical lipo cutoff voltage should be, but this could get very ugly, very expensive, and happen very fast for a whole lot of folks running them with lipos.

This was one test with one unit, but this one unit (triple checked it was on the correct setting) just killed a lipo pack dead on my bench.


Could you be more specific on how you ran your test ?
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Old 12-07-2007, 11:00 AM   #231
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Skiddins:
Can you ask him exactly and in detail how the cutoff is supposed to work please? I'm intimately familiar with the several different voltage averaging software methods currently being used to measure on and off loaded voltage at the ESC.

ESC's are all merely "on and off switches" where the "switch" is being manipulated thousands of times per second. When the switch is "on" the ESC is drawing full throttle power, and when it's "off" it's drawing zero. At half throttle, the "on" full power pulses equal the "off" power pulses to get the observed result - half power to the car. Reto is correct in that occasionally the full power pulses under heavy accelleration loads dip the pack voltage below 6v, but the next off pulse allows it to rebound back to the point where the "average" voltage remains above 6v. The point where the pack resting voltage (motor not running) was at 5v in my test was the real killer - the ESC allowed the motor to run even when the "average" voltage was WELL under 6v!

ESC and motor were installed in my mi3 with an AstroFlight Whattmeter in line with the battery to give me real time (average) voltage between the on and off pulses of the ESC. I put the car on a slick surface and gave it varying loads from no pressure (about 5A of load) to heavy pressure (15A of load) and watched the voltage. When it came down to 6v, I released all pressure to alleviate the disparity between on and off pulses as much as possible, and in order to protect lipos from failure the ESC should have cut off at that point PERIOD. But it kept running it down to 3.5v where it simply stopped becuse of lack of voltage to the ESC - NOT because it was protecting the pack. The pack only rebounded voltage to 5v (still WAY UNDER SAFE LIPO VOLTAGE) and then the ESC allowed it to run the motor again! This behavior is unnaceptable for a "lipo safe" ESC.

If someone in a technical dpt. @ LRP would like to contact me and discuss, please feel free:
813-889-9691
[email protected]
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Old 12-07-2007, 11:05 AM   #232
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As a side note:
We learned very quickly at Castle that a correct and safe lipo cutoff automatically makes the use of a 6cell Nimh pack with that same cutoff impossible. I should have known right from the start when a 6 cell NiMH pack and a 2 cell lipo pack were using the same cutoff level in the instructions.
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Old 12-07-2007, 11:07 AM   #233
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Do the SP ESCs have correct cutoffs:
I'll know tonight, and report accordingly if we need them to do some software work in order to be 100% safe w/lipo
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Old 12-07-2007, 11:22 AM   #234
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Originally Posted by JayBee View Post
What!!! I was just talkin' to Ritchie about our LRP's. We have TC Spec though...hmmm, I wonder Thanks for that bit of info Shawn The effort is definitely appreciated. Boy, I'm glad I just picked up (2) Novak lipo cut-off devices....
Jb

This is bad info ...
The lrp will cut off around 6 volts ...

if you decide to try to go as low as 6 volts the car won`t even be crawling back to you !!

doubt even you would dump a pack as low as this guy claims .....
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Old 12-07-2007, 12:04 PM   #235
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Quote:
Originally Posted by Shawn Palmer View Post
Skiddins:
Can you ask him exactly and in detail how the cutoff is supposed to work please? I'm intimately familiar with the several different voltage averaging software methods currently being used to measure on and off loaded voltage at the ESC.

ESC's are all merely "on and off switches" where the "switch" is being manipulated thousands of times per second. When the switch is "on" the ESC is drawing full throttle power, and when it's "off" it's drawing zero. At half throttle, the "on" full power pulses equal the "off" power pulses to get the observed result - half power to the car. Reto is correct in that occasionally the full power pulses under heavy accelleration loads dip the pack voltage below 6v, but the next off pulse allows it to rebound back to the point where the "average" voltage remains above 6v. The point where the pack resting voltage (motor not running) was at 5v in my test was the real killer - the ESC allowed the motor to run even when the "average" voltage was WELL under 6v!

ESC and motor were installed in my mi3 with an AstroFlight Whattmeter in line with the battery to give me real time (average) voltage between the on and off pulses of the ESC. I put the car on a slick surface and gave it varying loads from no pressure (about 5A of load) to heavy pressure (15A of load) and watched the voltage. When it came down to 6v, I released all pressure to alleviate the disparity between on and off pulses as much as possible, and in order to protect lipos from failure the ESC should have cut off at that point PERIOD. But it kept running it down to 3.5v where it simply stopped becuse of lack of voltage to the ESC - NOT because it was protecting the pack. The pack only rebounded voltage to 5v (still WAY UNDER SAFE LIPO VOLTAGE) and then the ESC allowed it to run the motor again! This behavior is unnaceptable for a "lipo safe" ESC.

If someone in a technical dpt. @ LRP would like to contact me and discuss, please feel free:
813-889-9691
[email protected]


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Old 12-07-2007, 12:09 PM   #236
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Reto from LRP PM'd me, and asked me to keep our discussion private. I've emailed him back my questions and am eagerly awaiting the answers.

Meanwhile I'll be looking at the SP ESCs
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Old 12-07-2007, 12:16 PM   #237
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Shawn
Take a battery , any kind will do ...

Discharge it to 6.25 Volts

Then put it in a car with the Lrp and tell us just how far the car went before the cut-off activated.....



A true test .....
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Old 12-07-2007, 12:24 PM   #238
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Uh, that's pretty much what I did last night Cherry.

Anyways - if you're lipo's are at 6.25v resting, they've already been too low when driving in the car. They should be at 6.6v resting or above AFTER the car no longer moves. If you see 6.0-6.2v after the first "slowdown" is noticed, you've already damaged the pack.

Testing will be ongoing.
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Old 12-07-2007, 12:40 PM   #239
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Test #2 just complete:

Ran the car with Whattmeter attached to keep track of voltage.

When the resting voltage came all the way down to 6.0 (already too far) that's when the power reduction came in (from just the pack being depleted, or software on the ESC???). If you run it this far on a lipo, you've just damaged it.

The car would still run until the under load voltage started to flirt with 4.5V. MAJOR lipo damage happening at this level. The ESC stopped the motor, the pack rebounded to 5.5v, and it allowed the car to run again for a few seconds.

So the results are not as bleak as last night, but still the same - the voltage threshold is TOO LOW to be safe for lipos if you run all the way to the "slowdown point".

Still more to do.
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Old 12-07-2007, 12:55 PM   #240
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This problem with the cutoff voltage only happrns with the LRP tc?
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