Core RC 5000mah Lipos...
12-07-2007, 12:10 PM
#241
That's the only one I've looked at so far.
12-07-2007, 04:50 PM
#242
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]
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]
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.
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.
12-09-2007, 07:49 AM
#243
Shawn, can the remaining capacity be estimated after a run buy measuring the voltage of the pack?
i.e. running 19t in the wet today the charger said it was putting 1280mAh back into the pack after a run. The voltage of the pack right now is 7.96V
What would the voltage be if the pack was at 80%, 50% etc? is there a common set of 'rules' for all LiPo's?
Thanks
Skiddins
i.e. running 19t in the wet today the charger said it was putting 1280mAh back into the pack after a run. The voltage of the pack right now is 7.96V
What would the voltage be if the pack was at 80%, 50% etc? is there a common set of 'rules' for all LiPo's?
Thanks
Skiddins
12-10-2007, 04:01 AM
#244
Tech Master
iTrader: (5)
hey guys looking for a new charger, i want to do lipo and nimh iowned and ice and found a few flaws.
it doesnt have the peak sensitivity i found my ep4200 cells would temp cut 46'c at 3 mv most times.
doesnt tell u time since peak eleapsed.
and lipo charge at 1c. though shawn made some points that this doesnt make much difference but say u have a 3200 pack and charge at 5 amps wont it take on more mah in 15 min than 3.2 amps or does the cc/cv cancel this out?
just trying to get some opinions on a good alround charger.
cheers
it doesnt have the peak sensitivity i found my ep4200 cells would temp cut 46'c at 3 mv most times.
doesnt tell u time since peak eleapsed.
and lipo charge at 1c. though shawn made some points that this doesnt make much difference but say u have a 3200 pack and charge at 5 amps wont it take on more mah in 15 min than 3.2 amps or does the cc/cv cancel this out?
just trying to get some opinions on a good alround charger.
cheers
12-10-2007, 06:58 AM
#245
Skiddins:
Remaining capacity and resting voltage do have a loose relationship, but it's a little different among each brand and size of pack.
From fully discharged going "up":
6.6-7.0v = basically empty. The voltage difference between 5% full (~7.0v)and 0% full (6.0v) is pretty dramatic.
7.5-7.75 = the "middle area" of anywhere between 20% and 70% full
7.75-8.0 = about 80-90% full
Anything over 8.0 = 90% or more full.
Again - loose rules here, and each type and capacity of pack will be a little different.
aus jd:
5A charge rate on a 3200 pack:
The charge time/rate are both slaves to the CC/CV lipo charging parameters. Once the pack voltage gets to 8.4v, the current ramps down to maintain 8.4v and no higher. So if you started with a 1/2 charged pack, you'd be charging at some figure over 3.2A for maybe 5 or 6 minutes.
From fully empty, you'd be able to be above 3.2A for about 15 min yes. And yes, it would be taking in more Mah than if it was set for 3.2A, but the reduction in charge time would be small. Maybe 5-8mins less.
So again - you're trading a few minutes faster charge time for an overall reduction in cycle life/performance of the pack. In my opinion, that's just not a trade I'm willing to make.
Remaining capacity and resting voltage do have a loose relationship, but it's a little different among each brand and size of pack.
From fully discharged going "up":
6.6-7.0v = basically empty. The voltage difference between 5% full (~7.0v)and 0% full (6.0v) is pretty dramatic.
7.5-7.75 = the "middle area" of anywhere between 20% and 70% full
7.75-8.0 = about 80-90% full
Anything over 8.0 = 90% or more full.
Again - loose rules here, and each type and capacity of pack will be a little different.
aus jd:
5A charge rate on a 3200 pack:
The charge time/rate are both slaves to the CC/CV lipo charging parameters. Once the pack voltage gets to 8.4v, the current ramps down to maintain 8.4v and no higher. So if you started with a 1/2 charged pack, you'd be charging at some figure over 3.2A for maybe 5 or 6 minutes.
From fully empty, you'd be able to be above 3.2A for about 15 min yes. And yes, it would be taking in more Mah than if it was set for 3.2A, but the reduction in charge time would be small. Maybe 5-8mins less.
So again - you're trading a few minutes faster charge time for an overall reduction in cycle life/performance of the pack. In my opinion, that's just not a trade I'm willing to make.
12-10-2007, 11:04 AM
#246
Thanks
Used my Core 5000 for the first time in anger today in 19t and was very pleased.
Car was as fast as the NiMh's in a straight line but I couldn't get my setup right (it was cold, wet and slippery all day)
After each 5 minute run it only needed 1280mAh to fill the pack back up.
It will be interesting to see how much more power I use when it's dry.
Skiddins
Used my Core 5000 for the first time in anger today in 19t and was very pleased.
Car was as fast as the NiMh's in a straight line but I couldn't get my setup right (it was cold, wet and slippery all day)
After each 5 minute run it only needed 1280mAh to fill the pack back up.
It will be interesting to see how much more power I use when it's dry.
Skiddins
12-11-2007, 10:25 PM
#247
I doubt it'll be much more even under dry conditions. Most of us running stock 13.5t with them here are charging back 1100-1400mah after a 5 min run.
12-12-2007, 04:41 AM
#249
Anyone else done any 'real world' comparisons between NiMH and their LiPo's.
I.e. is one or the other noticabvly faster?
Skiddins
I.e. is one or the other noticabvly faster?
Skiddins
12-12-2007, 06:01 AM
#250
heavy:
Not much if any at all, but check your lap times to be sure :-)
Not much if any at all, but check your lap times to be sure :-)
12-14-2007, 09:13 PM
#251
Shawn,
Since you like Hyperion chargers do you know about this one...
EOS 0610i NET
What does this mean...the 300mA balance thing. Also to plane/heli guys not discharge much. I don't see any discharge feature on some of these or they are low like 1amp :P
'Built-in Hyperion LBA10/300 Balancer with 10A max rating and 300mA max balance rate per cell."
===
Was looking at some of the chargers you mentioned or just an ICE for the Core 5000.
Since you like Hyperion chargers do you know about this one...
EOS 0610i NET
What does this mean...the 300mA balance thing. Also to plane/heli guys not discharge much. I don't see any discharge feature on some of these or they are low like 1amp :P
'Built-in Hyperion LBA10/300 Balancer with 10A max rating and 300mA max balance rate per cell."
===
Was looking at some of the chargers you mentioned or just an ICE for the Core 5000.
12-14-2007, 11:43 PM
#252
Depends what you mean by noticeably. From what I have seen when fresh NiMh's with good #'s are compared to the Orion 4800, the NiMh has up to 3 tenths a lap on the Lipo. We haven't had enough track time with the Core or any of these other new high capapcity/hard cased lipos to know much. I am hoping they show a little better performance than the Orions.
12-15-2007, 01:12 AM
#253
Shawn,
Since you like Hyperion chargers do you know about this one...
EOS 0610i NET
What does this mean...the 300mA balance thing. Also to plane/heli guys not discharge much. I don't see any discharge feature on some of these or they are low like 1amp :P
'Built-in Hyperion LBA10/300 Balancer with 10A max rating and 300mA max balance rate per cell."
===
Was looking at some of the chargers you mentioned or just an ICE for the Core 5000.
Since you like Hyperion chargers do you know about this one...
EOS 0610i NET
What does this mean...the 300mA balance thing. Also to plane/heli guys not discharge much. I don't see any discharge feature on some of these or they are low like 1amp :P
'Built-in Hyperion LBA10/300 Balancer with 10A max rating and 300mA max balance rate per cell."
===
Was looking at some of the chargers you mentioned or just an ICE for the Core 5000.
I could try and explain the 300mA balancing rate thing but I'd get my thoughts all wrapped around each other and wouldn't make a damn bit of sense
IMO though, it's an important feature in a balancer. Shawn chime in anytime......
12-15-2007, 02:38 AM
#254
Put my Core lipo on a balancer yesterday after running it for about 6 meetings, it was still that well balanced that the balancer didn't even need to kick in.
