Oh #%@!! What did I do to my SMC Lipos?
07-21-2009, 10:07 AM
#61
Wow so many good points. I am bookmarking this. It seems there are a couple different thoughts but this is still helpfull as a new person to lipos. Thanks for the formulas and real life experiences. Again thanks for the info
One question though if your running to 80 percent that doesn't seem like much runtime. It just weird when they say this battery last for so many min. Like 45 min then you onle really can run it for 10. Am I off and not understanding. I have the stampeve xl which doesn't take lipos and as soon as it doesn't go as fast I call it quits. I will definately use this advice I am just confused why they advertise long run times when you can't.
Thanks
One question though if your running to 80 percent that doesn't seem like much runtime. It just weird when they say this battery last for so many min. Like 45 min then you onle really can run it for 10. Am I off and not understanding. I have the stampeve xl which doesn't take lipos and as soon as it doesn't go as fast I call it quits. I will definately use this advice I am just confused why they advertise long run times when you can't.
Thanks
Last edited by rcmonster77; 07-21-2009 at 11:30 AM. Reason: One question
07-21-2009, 01:17 PM
#62
I run my Flux on 2S 25C 5000mah Neuenergy lipos. I get 22-25min runtime before I notice its starting to sag and quit. This is before the lvc hits (mines set at 3.2v/c).
Lipos usually take 3200-3400mah on charge. Thats about 70% capacity and I've not seen any change in charging character, so thats telling me I'm treating them ok.
If run time is that important, get the 9000s.
Lipos usually take 3200-3400mah on charge. Thats about 70% capacity and I've not seen any change in charging character, so thats telling me I'm treating them ok.
If run time is that important, get the 9000s.
07-21-2009, 01:25 PM
#63
Ok alot of you are seeming to forget that the LVC's trip while the battery is under Load. Meaning that the 3.4vper cell isnt really the actuall voltage.If you check your battery after the LVC trips it doesnt read 6.8v, but more like 7.0v or more.Why? because the system was under load when the LVC did what it was supposed to do.All this " you should never run a li-po to the lvc point" is garbage. If it is fact then why have all the battery manufacturers communicated to the speed control manufacturers that the safety zone for under load cut-off is in the 3.0-3.4v per cell range??
Man i have 6- elcheapo yeah packs that my 13 yr. old runs to the lvc almost every run. Guess what? they are 1 yr. and a half old and have hundreds of cycles on them and show no sign of fade.They get balanced about every 10th charge, and none of those el cheapo packs have puffed. I do have 1 SMC 5200 24c battery that has about 15 cycles on it that gets balanced EVERY charge and the performance is for lack of a better word disapointing for the 85.00 it costed compared to a 35.00 yeah racing 3200 pack. Do you think maybe there is a problem there other than the LVC??
Man i have 6- elcheapo yeah packs that my 13 yr. old runs to the lvc almost every run. Guess what? they are 1 yr. and a half old and have hundreds of cycles on them and show no sign of fade.They get balanced about every 10th charge, and none of those el cheapo packs have puffed. I do have 1 SMC 5200 24c battery that has about 15 cycles on it that gets balanced EVERY charge and the performance is for lack of a better word disapointing for the 85.00 it costed compared to a 35.00 yeah racing 3200 pack. Do you think maybe there is a problem there other than the LVC??
As for run time, I ran my Flux easily half an hour on a charge with these same batteries, without the LVC kicking in. That's a long time for an electric...it's probably not real healthy for the motor to go longer, anyway.
07-21-2009, 01:25 PM
#64
Wow so many good points. I am bookmarking this. It seems there are a couple different thoughts but this is still helpfull as a new person to lipos. Thanks for the formulas and real life experiences. Again thanks for the info
One question though if your running to 80 percent that doesn't seem like much runtime. It just weird when they say this battery last for so many min. Like 45 min then you onle really can run it for 10. Am I off and not understanding. I have the stampeve xl which doesn't take lipos and as soon as it doesn't go as fast I call it quits. I will definately use this advice I am just confused why they advertise long run times when you can't.
Thanks
One question though if your running to 80 percent that doesn't seem like much runtime. It just weird when they say this battery last for so many min. Like 45 min then you onle really can run it for 10. Am I off and not understanding. I have the stampeve xl which doesn't take lipos and as soon as it doesn't go as fast I call it quits. I will definately use this advice I am just confused why they advertise long run times when you can't.
Thanks
07-21-2009, 02:33 PM
#65
Lol I am not good at math. 
. Thanks I infestsnd now. You guys are awedsome and have patience for a beginner like me. Thanks again
. Thanks I infestsnd now. You guys are awedsome and have patience for a beginner like me. Thanks again
07-21-2009, 02:39 PM
#66
Lol I wasn't understanding and it did seem odd running only 20 percent. . Thanks I understand now. You guys are awesome and you have patience for a beginner like me. Thanks again
Also I was reading an article in rc car action. Sept 09 the language of electronics. And one of the terms was lvc. It said if your speed control doesn't have lvc you can get a external cutoff.
As I am new I know not of this. Any comments on that ie its great or just go with the above tips and don't over run it.
Thanks
Sorry for prior post. Not sure how I double posted. I am posting from phone. Out camping and runnin the pede.
. Thanks I understand now. You guys are awesome and you have patience for a beginner like me. Thanks again Also I was reading an article in rc car action. Sept 09 the language of electronics. And one of the terms was lvc. It said if your speed control doesn't have lvc you can get a external cutoff.
As I am new I know not of this. Any comments on that ie its great or just go with the above tips and don't over run it.
Thanks
Sorry for prior post. Not sure how I double posted. I am posting from phone. Out camping and runnin the pede.
Last edited by rcmonster77; 07-21-2009 at 02:47 PM. Reason: Edit
07-21-2009, 03:27 PM
#67
Considering that Danny is the owner of SMC, the OP was giving him a hard time by instantly assuming the batteries were at fault and not responding to his email immediatly. Maybe I'm wrong? 
I'd also be interested in the voltage reading of each individual cell. Freezebyte, can you check the voltage of each cell at the balance plug?
I'd also be interested in the voltage reading of each individual cell. Freezebyte, can you check the voltage of each cell at the balance plug?
Sorry I was meaning by name, not business.
07-21-2009, 05:30 PM
#68
Ok alot of you are seeming to forget that the LVC's trip while the battery is under Load. Meaning that the 3.4vper cell isnt really the actuall voltage.If you check your battery after the LVC trips it doesnt read 6.8v, but more like 7.0v or more.Why? because the system was under load when the LVC did what it was supposed to do.All this " you should never run a li-po to the lvc point" is garbage. If it is fact then why have all the battery manufacturers communicated to the speed control manufacturers that the safety zone for under load cut-off is in the 3.0-3.4v per cell range??
Man i have 6- elcheapo yeah packs that my 13 yr. old runs to the lvc almost every run. Guess what? they are 1 yr. and a half old and have hundreds of cycles on them and show no sign of fade.They get balanced about every 10th charge, and none of those el cheapo packs have puffed. I do have 1 SMC 5200 24c battery that has about 15 cycles on it that gets balanced EVERY charge and the performance is for lack of a better word disapointing for the 85.00 it costed compared to a 35.00 yeah racing 3200 pack. Do you think maybe there is a problem there other than the LVC??
Man i have 6- elcheapo yeah packs that my 13 yr. old runs to the lvc almost every run. Guess what? they are 1 yr. and a half old and have hundreds of cycles on them and show no sign of fade.They get balanced about every 10th charge, and none of those el cheapo packs have puffed. I do have 1 SMC 5200 24c battery that has about 15 cycles on it that gets balanced EVERY charge and the performance is for lack of a better word disapointing for the 85.00 it costed compared to a 35.00 yeah racing 3200 pack. Do you think maybe there is a problem there other than the LVC??
I had my MMM set at a 3.2v/cell lipo cut off, however I was curious as to the packs behaviour so I put on a data logger:
Under load the pack frequently drops below 3.2v/cell before the LVC kicks in, the sampling rate of the LVC is such that it's really based on the packs resting voltage (which stayed over 3.2) not the underload voltage.
Lipos can rebound from amp draw a lot quicker than Nimh, hence a Nimh will trigger a LVC wheras a Lipo may recover before the LVC takes the next sample (sampling rate), My logger was set to take 100 samples a second which was obviously quicker than that of the LVC as it easily showed the packs dropping below what I had the LVC set at. And remember EVERY drop below 2.7-3v a cell does damage to some extent.
Also the drop off is quite noticable when the packs resting voltage drops below 3.5v/cell which is why I have chosen to set my LVC at this point.
Going by your assertions the pack drops frequently below 3v/cell before the LVC kicks in. Obviously this has the potential to cause damage to Lipos over the longer term and as Freezebyte has said he ran to LVC, I think that's a contributing factor, the packs got overly discharged (albeit under load) until one day they gave up.
Happy to share the raw data file, and yes my MMM LVC works fine and has been tested.
But if we followed your advice, on an RC car that pulls some serious amps under load as seen below: (Same Run)
Our lipo batteries are going to amount to nothing more than a
07-21-2009, 06:04 PM
#69
No email reply from SMC either at this point
07-21-2009, 07:12 PM
#70
Sorry but I will disagree strongly on this and I can actually prove this.
I had my MMM set at a 3.2v/cell lipo cut off, however I was curious as to the packs behaviour so I put on a data logger:
Under load the pack frequently drops below 3.2v/cell before the LVC kicks in, the sampling rate of the LVC is such that it's really based on the packs resting voltage (which stayed over 3.2) not the underload voltage.
Lipos can rebound from amp draw a lot quicker than Nimh, hence a Nimh will trigger a LVC wheras a Lipo may recover before the LVC takes the next sample (sampling rate), My logger was set to take 100 samples a second which was obviously quicker than that of the LVC as it easily showed the packs dropping below what I had the LVC set at. And remember EVERY drop below 2.7-3v a cell does damage to some extent.
Also the drop off is quite noticable when the packs resting voltage drops below 3.5v/cell which is why I have chosen to set my LVC at this point.
Going by your assertions the pack drops frequently below 3v/cell before the LVC kicks in. Obviously this has the potential to cause damage to Lipos over the longer term and as Freezebyte has said he ran to LVC, I think that's a contributing factor, the packs got overly discharged (albeit under load) until one day they gave up.
Happy to share the raw data file, and yes my MMM LVC works fine and has been tested.
But if we followed your advice, on an RC car that pulls some serious amps under load as seen below: (Same Run)
Our lipo batteries are going to amount to nothing more than a
I had my MMM set at a 3.2v/cell lipo cut off, however I was curious as to the packs behaviour so I put on a data logger:
Under load the pack frequently drops below 3.2v/cell before the LVC kicks in, the sampling rate of the LVC is such that it's really based on the packs resting voltage (which stayed over 3.2) not the underload voltage.
Lipos can rebound from amp draw a lot quicker than Nimh, hence a Nimh will trigger a LVC wheras a Lipo may recover before the LVC takes the next sample (sampling rate), My logger was set to take 100 samples a second which was obviously quicker than that of the LVC as it easily showed the packs dropping below what I had the LVC set at. And remember EVERY drop below 2.7-3v a cell does damage to some extent.
Also the drop off is quite noticable when the packs resting voltage drops below 3.5v/cell which is why I have chosen to set my LVC at this point.
Going by your assertions the pack drops frequently below 3v/cell before the LVC kicks in. Obviously this has the potential to cause damage to Lipos over the longer term and as Freezebyte has said he ran to LVC, I think that's a contributing factor, the packs got overly discharged (albeit under load) until one day they gave up.
Happy to share the raw data file, and yes my MMM LVC works fine and has been tested.
But if we followed your advice, on an RC car that pulls some serious amps under load as seen below: (Same Run)
Our lipo batteries are going to amount to nothing more than a
07-21-2009, 07:17 PM
#71
lol ok basically if you set your LVC to 3.2v/cell and run to the LVC you will cause damage as under load the packs will drop beyond that and the sampling rate of the MMM LVC is not fast enough to detect this drop, so it doesn't kick in.
But using an E-Logger which has a faster sampling rate, it's fairly obvious.
But using an E-Logger which has a faster sampling rate, it's fairly obvious.
07-21-2009, 07:50 PM
#72
Again sorry for clarifying. So this means running to lvc is bad. And so running only 80 percent theory is ok? You were just providing proof running to lvc is bad then?
Thanks
Thanks
07-21-2009, 07:59 PM
#73
YES!!!!! Just like I've said before
, even though there's a LVC, you shouldn't rely on it all the time. Nexxus provided back up info. It's a failsafe. If you want to use it regularly, then you should set it very high, so that when there is an amperage draw it doesn't spike the LiPo's cell voltage to dangerous levels. Some one finally saw the light 
, even though there's a LVC, you shouldn't rely on it all the time. Nexxus provided back up info. It's a failsafe. If you want to use it regularly, then you should set it very high, so that when there is an amperage draw it doesn't spike the LiPo's cell voltage to dangerous levels. Some one finally saw the light
07-21-2009, 08:25 PM
#75
Great thanks for the explanation and taking time to do it as well