steven.b.watts
100 W
Hello,
Does anyone here have hands on experience using RC batteries on ebikes? How important is the 'C' rating?
Does anyone here have hands on experience using RC batteries on ebikes? How important is the 'C' rating?
RC battery 'C' rating
- Thread starter steven.b.watts
- Start date
greg_p
100 mW
C rating indicated how many ampere you can pull out a battery. It"s a multiplicator or the capacity in Ah.
Ex: a lipo (whatever s) of 8ah that has a C rating of 10 can be pulled out (10x8=)80 amperes. Check if the C rating is for continous or peak discharge.
Ex: a lipo (whatever s) of 8ah that has a C rating of 10 can be pulled out (10x8=)80 amperes. Check if the C rating is for continous or peak discharge.
If you want to occasionally pull high amps from a small battery pack, you definitely need a high C-rate. If you have a physically large battery pack with a high Amp-hour (Ah) size, it becomes a little less important.
steven.b.watts
100 W
I suppose it all depends on the controller then? If my battery can only pull out 'x' amps max and my battery can provide 'x+y' amps (or 'C'? Clearly related) then i have wasted 'y', and have no need for this excess 'C'?
I have a castle creations Phoenix edge HV 120. It says 12s lipo max and 120 amps max here
Does this mean I can't run 4 6s RC packs? That seems weird, because the previous owner did. Also, what would be my max 'C' rating I could run on these 6s packs (they're likely going to be between 5Ah and 8Ah each, and somewhere between 40c and 65c continuous, between 60c and 135c bursts depending on what battery I get, which depends on what is possible).
If my controller is 120a max:
my battery is 5ah, then 120a/5ah=24c, if i grt a 5ah battery i should stick to 24c continuous (can do more, but no point).
Another:
My battery is 8ah, then 120a/8ah=15c, if i get an 8ah battery i should stick to 15c continuous.
Are these calculations correct? I suppose the more ah, the less 'C' I need? Why would I get more C and less ah, any ideas? Would I get a high ah battery, like the second example above, if I wanted more range with less "torque" at any given speed, or a lower ah battery with higher c rating if I wanted more torque (therefore giving up range)?
I have a castle creations Phoenix edge HV 120. It says 12s lipo max and 120 amps max here
Does this mean I can't run 4 6s RC packs? That seems weird, because the previous owner did. Also, what would be my max 'C' rating I could run on these 6s packs (they're likely going to be between 5Ah and 8Ah each, and somewhere between 40c and 65c continuous, between 60c and 135c bursts depending on what battery I get, which depends on what is possible).
If my controller is 120a max:
my battery is 5ah, then 120a/5ah=24c, if i grt a 5ah battery i should stick to 24c continuous (can do more, but no point).
Another:
My battery is 8ah, then 120a/8ah=15c, if i get an 8ah battery i should stick to 15c continuous.
Are these calculations correct? I suppose the more ah, the less 'C' I need? Why would I get more C and less ah, any ideas? Would I get a high ah battery, like the second example above, if I wanted more range with less "torque" at any given speed, or a lower ah battery with higher c rating if I wanted more torque (therefore giving up range)?
nutnspecial
10 MW
Is this for that custom mid drive originally from england? Really cool bike and deal!
Sounds like 4x 6s 30c packs would work nice if they're about 8ah and 30c.
A good rule of thumb is to cut max cont C rates by 2/3 - 3/4. 30c would be 7-10c.
Two 6s serial cell packs, series those for 12s.
Make two identical 12s sets, then parallel those sets for 12s 2p and double the AH, range, and discharge.
You now have 12s 2p, and used 4 packs of 6s.
If they're 8ah 30c cells, you'd have 16ah because of the parallel set. Times the 16ah by the reduced c rate for your safe cont discharge. 30c = 7-10c, so 16ah of 30c = 112 -160 safe discharge.
Hope that helps!
Sounds like 4x 6s 30c packs would work nice if they're about 8ah and 30c.
A good rule of thumb is to cut max cont C rates by 2/3 - 3/4. 30c would be 7-10c.
Two 6s serial cell packs, series those for 12s.
Make two identical 12s sets, then parallel those sets for 12s 2p and double the AH, range, and discharge.
You now have 12s 2p, and used 4 packs of 6s.
If they're 8ah 30c cells, you'd have 16ah because of the parallel set. Times the 16ah by the reduced c rate for your safe cont discharge. 30c = 7-10c, so 16ah of 30c = 112 -160 safe discharge.
Hope that helps!
nutnspecial
10 MW
Yes, but the C rate should be de-rated. You might want 3p (15ah) of 30c 5ah cells for 120a. Or 2p of 30c 8ah.
Yes
Smaller pack, but notice the prices rise as the C rate rises.
A bigger pack can get away with cheaper lower 'c' cells for the same discharge, and bonus range, but at the cost of weight/size.
My 2p pack of 5.8ah 30c cells = 11.6 ah, and can discharge towards 100a if I don't mind pushing them.
I wouldn't dare discharge 30x that 11.6ah.
steven.b.watts
100 W
Thanks for the help!
I thought I may have, but honestly, I don't have enough room for 4x 8ah packs
I guess I'll have to go with 4x 6ah with 40c continuous.
I.e. (.25x40c) -> (.33x40c) = 10 -> 13.2 c on a 12Ah pack = 120 -> 132a safe discharge (which makes sense as my controller is 120a max)
I thought I may have, but honestly, I don't have enough room for 4x 8ah packs
I guess I'll have to go with 4x 6ah with 40c continuous.I.e. (.25x40c) -> (.33x40c) = 10 -> 13.2 c on a 12Ah pack = 120 -> 132a safe discharge (which makes sense as my controller is 120a max)
nutnspecial
10 MW
The 1/4 -1/3 rule is what I've heard on here and has worked for me. My batteries didn't like drawing 1/2 their C. Depends on the setup and riding style too. My single reduction mid is maybe harder on batteries than a multispeed, because I'm trying to make up for lack of gears with power.
The 2p of 6ah packs should be reasonable in cost and range. You might want to also parallel packs in both groups thru their balance connectors for best results. 30 or 40c won't make a huge diff when derating /3 or /4.
If you're new to rc, I'd get 2 battery medics from HK/ebay, and some parallel 6s 'balance' harnesses from ebay, HK, or buddyRC. Get lipos you can serial one to the other, with the male/female bullets. Then get a back of those same (usual 5.5mm) bullets from HK/aliex and make the 2 little parallel leads for mains. Or icecube57 or other places probably sell those for the mains.
I like the look of the flightmax 6s 8ah 30c for 60$. If they're too physically big, there are these 5ah 4 same $:
http://www.hobbyking.com/hobbyking/store/__10308__Turnigy_5000mAh_6S_40C_Lipo_Pack.html
The 10ah should be good for 10-20mi depending on how vicious you are with that 120a lol
The 2p of 6ah packs should be reasonable in cost and range. You might want to also parallel packs in both groups thru their balance connectors for best results. 30 or 40c won't make a huge diff when derating /3 or /4.
If you're new to rc, I'd get 2 battery medics from HK/ebay, and some parallel 6s 'balance' harnesses from ebay, HK, or buddyRC. Get lipos you can serial one to the other, with the male/female bullets. Then get a back of those same (usual 5.5mm) bullets from HK/aliex and make the 2 little parallel leads for mains. Or icecube57 or other places probably sell those for the mains.
I like the look of the flightmax 6s 8ah 30c for 60$. If they're too physically big, there are these 5ah 4 same $:
http://www.hobbyking.com/hobbyking/store/__10308__Turnigy_5000mAh_6S_40C_Lipo_Pack.html
The 10ah should be good for 10-20mi depending on how vicious you are with that 120a lol
wesnewell
100 GW
Just one question. Why the heck are you using a helicopter/fixed wing plane 120A ESC on an ebike? They don't have the proper controls you need and they are voltage limited. Get a proper controller for a lot lot less money. C rates are easy as stated before. C rate times AH rating gives max rated amp draw from any battery. Exp: 20C times 10AH pack = 200A. What is the watt rating of the motor you want to use? BTW, I've been using rc battery packs exclusively for over 5 years on ebikes.
steven.b.watts
100 W
What do I set my Accucel 6 charger Amps charge rate to while charging 12s2p 30c 11.6Ah battery 44.4v?
Do I set it to 11.6? I think my charger says max 6a..
Do I set it to 11.6? I think my charger says max 6a..
FluxZoom
100 W
Does anyone even bother searching anymore? Even just like one search on a question before asking?
steven.b.watts
100 W
I don't know why everyone is so anal about searching. In the amount of time it took you to complain someone could have typed up an answer. Some people enjoy talking and sharing information, collaborating, it make them feel smart, because they are.
FluxZoom
100 W
steven.b.watts said:
Collaboration is -very- different than what you are doing. Asking for a definition to a static singular idea and a simple one is just a weak ass "gimmie", you want to be spoon fed information instead of seek it out. You'll just become a dependent spammer that doesn't know how to find their own ass let alone the answer to many elementary questions. There is no ambiguity or collaboration on the idea of a C rating, it's known, it's been written on this forum and elsewhere before now, many times.
In the amount of time it took you to submit your thread you could have found your answer in a search.
I am not perfect, I don't expect you to be perfect, but we both know you didn't do a single search and the notion that you disregard the effort of others in answering your questions is frankly completely asinine.
Grizzl-E
100 W
FluxZoom said:
Thank you! I am not allowed to say these things at work so I love seeing someone get told what a leech they are being.
Im seriously saving this somewhere so I can look at it on those days when I want to turn off my phone before I tear a strip off the next guy who picks up his phone before he uses his brain or does a little research.
Hillhater
100 TW
You cannot charge a 12s pack with that charger.steven.b.watts said:
The most it can do is 6s (22v), so you will have to split the packs up for charging.
Set it to 6 amps, but it may not be able to push that many amps even into a 6s pack....it will regulate its own output.
steven.b.watts
100 W
Hillhater said:
I suppose if I'm charging at 2c I could try that, but if 6a is my max I might as well charge at 1c and set to 5.8a because each pack is 5800mah, is that correct?
Also, which of these is correct:
Hillhater
100 TW
None of your diagrams are correct and either will cause you big problems if you try to use them.
You seem to have a critical case of. "Ambition exceeding Ability" syndrome.
You should go back to the Battery Basics" and "Charging Lipo" threads before you go any further !
You seem to have a critical case of. "Ambition exceeding Ability" syndrome.
You should go back to the Battery Basics" and "Charging Lipo" threads before you go any further !
steven.b.watts
100 W
Hillhater said:
I think you are mistaken.
I have been searching these kind of threads, as everyone recommended, for about 4 hours yesterday and 4 hours today for many different things, including the issue at hand, and these are the only two diagrams I could find (the ones above) found here and here.
The only reason I have brought my question here is, unfortunately, I found diagrams that are different for the same configuration. So I would like to know if either; one of them is wrong, or both would work the same. You obviously have a reputation on this site, so maybe you could tell me why, after doing all this searching everyone recommends, I still end up with a question.
I bought this bike second hand, and the previous owner has a 12s2p configuration. I have also heard of many people running 12s2p configuration, they are all alive and well and so are their packs. So I do believe it is possible, despite your implications.
The only thing I could imagine is that you are implying, when saying "either will cause you big problems", that I am trying to charge my batteries this way. That is NOT the case. I know I need to charge them separately. I am referring to the 12s2p config to operate, not charge
I found a LiPo RC wiring calulation website as well, that seems to agree with the first img:
Grizzl-E
100 W
The lower diagram is correct for discharging the batteries 12s 2p. I think hillhater is simply expressing the same concern I have. If you have to ask about such basics, your going to vaporize your connectors if not your fingertips at some point.
However I applaud your efforts to learn. Hope It goes well.
Sent from my iPhone using Tapatalk
However I applaud your efforts to learn. Hope It goes well.
Sent from my iPhone using Tapatalk
steven.b.watts
100 W
I built some complicated drift cars, but this is my first ebike. Needless to say, despite my long standing history in mechanics, i have never had to connect more than one battery together. It is quite daunting. This is why i am asking so many questions.
I know not to allow, in any circumstance, the two opposing forcing of a single battery to touch. However, I know you can do this with two different batteries (called series wiring, as we all know). I just didn't know if connecting these +/- bridges together would somehow reverse the effect back to the principal of not connecting +/- of a single battery. Again, I've never had to deal with more than one battery (on cars). I am getting slack because of the very reason I am asking. I.e. you're saying I'm having a hard time getting an answer because no one wants me to burn my fingers off, yet this is the very same reason I am asking the question in the first place, to avoid the exact same thing.
What I am asking likely seems obvious to many people on here but hey, we all start somewhere, I'm just trying to stay safe. I just hope you guys aren't like this to everyone trying to enter the industry, because if you do, you're certainly not helping the industry grow. A lot of people with a weak stomach will just get upset about large barriers to entry and turn to another hobby with less arrogance
I know not to allow, in any circumstance, the two opposing forcing of a single battery to touch. However, I know you can do this with two different batteries (called series wiring, as we all know). I just didn't know if connecting these +/- bridges together would somehow reverse the effect back to the principal of not connecting +/- of a single battery. Again, I've never had to deal with more than one battery (on cars). I am getting slack because of the very reason I am asking. I.e. you're saying I'm having a hard time getting an answer because no one wants me to burn my fingers off, yet this is the very same reason I am asking the question in the first place, to avoid the exact same thing.
What I am asking likely seems obvious to many people on here but hey, we all start somewhere, I'm just trying to stay safe. I just hope you guys aren't like this to everyone trying to enter the industry, because if you do, you're certainly not helping the industry grow. A lot of people with a weak stomach will just get upset about large barriers to entry and turn to another hobby with less arrogance
Hillhater
100 TW
Yes, you were asking about charging in that post.
nutnspecial
10 MW
Both diagrams are correct while the lower is simpler and more to my taste with series then parallel connections. Yes, for 12s 2p.
If using a 6s charger, you could charge all 24 cells at once as 6s 4p (23.2ah).
Obviously 6amps is one quarter C of that ~23ah, and those cells are probably rated 2c charge.
So instead of the possible 1/2 hour charge, it will take ~4hr to charge.
And you'll have to reconfigure every charge/discharge. (which I can confirm sucks)
I have some of the hrp meanwells to deliver 14amps at 6-22s (21-90v). They'd give you a decent 45min full charge but you'll have to set them up and should always monitor charging. That also goes for 4hrs on a balance charger though too imo, so the faster bulk charge makes more sense for me, and others.
Teslanv MW HRP https://endless-sphere.com/forums/viewtopic.php?f=31&t=68195&hilit=+hrp&start=75
I also like the gophert adjustible power supply for the digital readout and easy integrated current and voltage controls. It's not necessary to have, but can be in series with hrps for more voltage/control, power a balancer, charge a car battery, or fine tune a weak cell/cell group in leu of a balancer and pack teardown, as I did yesterday. It's a 'entry' true 'power supply'.
Gophert PS https://endless-sphere.com/forums/viewtopic.php?f=14&t=69195&hilit=+meanwell
Keep up the positive, inquisitive, and helpful attitude and action Mr Watts, we should all always strive for such and even continued improvement.
If using a 6s charger, you could charge all 24 cells at once as 6s 4p (23.2ah).
Obviously 6amps is one quarter C of that ~23ah, and those cells are probably rated 2c charge.
So instead of the possible 1/2 hour charge, it will take ~4hr to charge.
And you'll have to reconfigure every charge/discharge. (which I can confirm sucks)
I have some of the hrp meanwells to deliver 14amps at 6-22s (21-90v). They'd give you a decent 45min full charge but you'll have to set them up and should always monitor charging. That also goes for 4hrs on a balance charger though too imo, so the faster bulk charge makes more sense for me, and others.
Teslanv MW HRP https://endless-sphere.com/forums/viewtopic.php?f=31&t=68195&hilit=+hrp&start=75
I also like the gophert adjustible power supply for the digital readout and easy integrated current and voltage controls. It's not necessary to have, but can be in series with hrps for more voltage/control, power a balancer, charge a car battery, or fine tune a weak cell/cell group in leu of a balancer and pack teardown, as I did yesterday. It's a 'entry' true 'power supply'.
Gophert PS https://endless-sphere.com/forums/viewtopic.php?f=14&t=69195&hilit=+meanwell
Keep up the positive, inquisitive, and helpful attitude and action Mr Watts, we should all always strive for such and even continued improvement.
Hillhater
100 TW
Just a minor point..
If you read the manual for that charger, you will find that it has a max output of 50Watts.
Which basicly means that when charging a 6s pack (22.5v) can only charge at 2.2 amps maximum.....if you have a suitable power supply.
Pack charging ( even without balancing) will take you a long time (16+ hrs ?) with that charger .
friendly1uk
1 MW
I think you need help choosing the right controller and finding a battery off the shelf that suits it.
What is this motor that wants 120 amps but only 12s ?
You can't be confident telling anyone to use lipo and RC chargers. It's best avoided or there is a real chance of fire. We see it quite often. Some user here may advise you, then read your house burned down, and just change their username. It's not their problem. I've seen it happen. In reality your on an EV forum asking about RC stuff. No commercial bike uses that RC gear because it's not suitable.
Your 4 hours seems to of been wasted. Skipping forward weeks, if you really need 12s at 120A then you want a 12s bms modified with off-board fets that will take that load, with a bulk charger that just plugs in. It will be cheaper and better. Safer by a factor of hundreds. That is how a commercial standard EV is made.
Have a gander at this: https://endless-sphere.com/forums/viewtopic.php?f=14&t=56886&p=1009402&hilit=yginrut&sid=c8c46d679c533cd539b7224ddbbeea59#p1009402
It's not perfect. One or two connectors could be arranged differently but it's laid out to make sense. 12s2p with bms and bulk charger. Just needs fets to get past it's ~65A limit (once bolted down properly) Or you could be stupid and put a wire across them, making it just a charger with none of the added protection a BMS should bring. You will likely nail your pack though if you do that, or perhaps light it up in use. Just a couple of the risks RC methods expose you too though.
What is this motor that wants 120 amps but only 12s ?
You can't be confident telling anyone to use lipo and RC chargers. It's best avoided or there is a real chance of fire. We see it quite often. Some user here may advise you, then read your house burned down, and just change their username. It's not their problem. I've seen it happen. In reality your on an EV forum asking about RC stuff. No commercial bike uses that RC gear because it's not suitable.
Your 4 hours seems to of been wasted. Skipping forward weeks, if you really need 12s at 120A then you want a 12s bms modified with off-board fets that will take that load, with a bulk charger that just plugs in. It will be cheaper and better. Safer by a factor of hundreds. That is how a commercial standard EV is made.
Have a gander at this: https://endless-sphere.com/forums/viewtopic.php?f=14&t=56886&p=1009402&hilit=yginrut&sid=c8c46d679c533cd539b7224ddbbeea59#p1009402
It's not perfect. One or two connectors could be arranged differently but it's laid out to make sense. 12s2p with bms and bulk charger. Just needs fets to get past it's ~65A limit (once bolted down properly) Or you could be stupid and put a wire across them, making it just a charger with none of the added protection a BMS should bring. You will likely nail your pack though if you do that, or perhaps light it up in use. Just a couple of the risks RC methods expose you too though.
steven.b.watts
100 W
I'll be charging my batteries individually because I have read time and time again that charging lipos in parallel is when bad things start to happen, so I cannot charge them 6s4p..
Also, if you click on the link to my build in my signature below, you will see that I cannot build a pack like the one referenced in the previous post because I do not have much room to work with at all. My controller is a castle creations Phoenix. It is a small controller (again, I do not have room for anything else) made for RC stuff (like helis) so it has high amp rating, I use a gear box to leverage that power to my back wheel. Very different from the hub motors.
I cannot agree with you about the fires, because there is a huge RC community out there and their houses have not burnt down.. The only reason house that would burn down would be whoever said to charge them in parallel. Pray you never use RC batteries
Also, if you click on the link to my build in my signature below, you will see that I cannot build a pack like the one referenced in the previous post because I do not have much room to work with at all. My controller is a castle creations Phoenix. It is a small controller (again, I do not have room for anything else) made for RC stuff (like helis) so it has high amp rating, I use a gear box to leverage that power to my back wheel. Very different from the hub motors.
I cannot agree with you about the fires, because there is a huge RC community out there and their houses have not burnt down.. The only reason house that would burn down would be whoever said to charge them in parallel. Pray you never use RC batteries
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