Ok to have bms of max 35amps if my controller is max current 35a?
- Thread starter Cyclomania
- Start date
The BMS protects the battery, so it should be sized lower than the continuous discharge rating of the pack to account for cell degradation over time. The battery, not the BMS, should have a greater continuous current rating of the controller.
What battery are you using ? I mean what chemistry and or the name of the cell and the model number of the cell ? As there are many packs made with cells made for a laptop and you are 200 lb with bike and motor and if you're going up hills that's harder is it flatland ?
Anyway before you buy the battery they should tell you what sells are inside or else they're basically generic Chinese cells.
For 40 amps I want my battery to be able to deliver 60 amps or more. And and let her go there a 40 amp BMS
But there are a lot of different 40 amp BMS and their Max amps it's in the print but you got to do some reading on the one you buy or are looking at.
I have one of those controllers it gave up the ghost, but even with that same manufacture with that same sticker the controller is not always the same inside amp demands. So go with the strong enough battery to start with.
Anyway before you buy the battery they should tell you what sells are inside or else they're basically generic Chinese cells.
For 40 amps I want my battery to be able to deliver 60 amps or more. And and let her go there a 40 amp BMS
But there are a lot of different 40 amp BMS and their Max amps it's in the print but you got to do some reading on the one you buy or are looking at.
I have one of those controllers it gave up the ghost, but even with that same manufacture with that same sticker the controller is not always the same inside amp demands. So go with the strong enough battery to start with.
Cyclomania
10 kW
Yes I know the cells can handle it. I wonder if the controller should be set lower or if the max current of the controller and bms can be the same number? Or would this trigger the bms if the controller is running at max current? So 35a bms might be too low ?
Cyclomania
10 kW
I have used the same battery before with the controller but the old bms went berserk for some reason. I have slightly unbalanced cell groups(but have balanced them with an active balancer now). So I am switching to another bms. Thing is I am not sure what the max current of the old bms was because there is no label on it. But I am going to try and see how the battery will receive a new bms.
We did conclude that it is probably the bms that is faulty in the chain, in the other thread where I am talking about this battery.
Anyway I opened this thread because I cannot remember if it is ok to have the same max current for bms as you have for the controller. I am going to change bms but do not want to pick the wrong max current.
Here's a 30 amp BMS but look how it reads out
Lithium ion and polymer settings
Overcharge voltage per cell: 4.2
Overdischarge voltage per cell: 2.8
Discharge Continuous Amps: 30
10 second Discharge Burst: 60a
Charge Continuous Amps: 30a
Balancing Current: 50mA
This is a $11 BMS from battery hookup USA
From xiaoxiang or something.
Lithium Iron Phosphate (Lifepo4) settings
Overcharge voltage per cell: 3.65
Overdischarge voltage per cell: 2.5
Discharge Continuous Amps: 30
10 second Discharge Burst: 60a
Charge Continuous Amps: 30a
Balancing Current: 50mA
I have a Bluetooth BMS and I like it I don't have the programming cable.
Lithium ion and polymer settings
Overcharge voltage per cell: 4.2
Overdischarge voltage per cell: 2.8
Discharge Continuous Amps: 30
10 second Discharge Burst: 60a
Charge Continuous Amps: 30a
Balancing Current: 50mA
This is a $11 BMS from battery hookup USA
From xiaoxiang or something.
Lithium Iron Phosphate (Lifepo4) settings
Overcharge voltage per cell: 3.65
Overdischarge voltage per cell: 2.5
Discharge Continuous Amps: 30
10 second Discharge Burst: 60a
Charge Continuous Amps: 30a
Balancing Current: 50mA
I have a Bluetooth BMS and I like it I don't have the programming cable.
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The controllers current limit protects the controller, and the motor, so adjust accordingly.
Choose a BMS that protects your battery. If it were me, I’d size the BMS conservatively based on the battery’s capability. Otherwise, if you have a future upgrade, you don’t have to replace it again.
Cyclomania
10 kW
Ok so I guess what you are saying it would work as long as the cells can handle it right?
The thing I cannot get my head around is if the max current of the controller. Let's for example say it is at 50 amps. And the bms is at 40 amps. This would fry the bms correct? If I have 50 amps controller it would trigger a bms of 40?
This is what I am trying to get at. I have learned this in the past but cannot remember.
Cyclomania
10 kW
I think perhaps I should wait fo a higher rated bms. The thing with this controller from CSC is that they say the max current is 70a. Rated current is actually closer to 35. Can this really be the case? What do you guys think? It is this one:
Attachments
Like those spec sheets on the BMS I showed you.
It's 30 amps continuous 10sec 60 amp burst.
Where is the spec sheet on the BMS that you want ?
Okay lay all your cards on the table.
What battery are we talking about ? Do you have a link ?
What motor are you going to use what turn a 3t motor will suck a lot more amps a lot faster and demand more than a 5T motor will saturate faster won't take anymore. Watts.
We need more info to answer your question. You're asking for a Pacific answer and you're giving us general information.
Plus what do you have ? And what you need to purchase?
Talk to text.
It's 30 amps continuous 10sec 60 amp burst.
Where is the spec sheet on the BMS that you want ?
Okay lay all your cards on the table.
What battery are we talking about ? Do you have a link ?
What motor are you going to use what turn a 3t motor will suck a lot more amps a lot faster and demand more than a 5T motor will saturate faster won't take anymore. Watts.
We need more info to answer your question. You're asking for a Pacific answer and you're giving us general information.
Plus what do you have ? And what you need to purchase?
Talk to text.
Ok I have an em3ev 36-72v controller with a 72v battery with mxus 4t d.d. hub. It's surprises me that it will continually give 40 amps I would thought it would saturate at a certain speed or after a while and lower amps .But No it's 40amps much much longer than other controllers. So I guess it's also the mapping of the controller. As not all controllers even from the same Chinese company at the same. So you need headroom.
40 amp controller 60 amp bms a battery that can produce 80amps.
I would over build the battery yes.
40 amp controller 60 amp bms a battery that can produce 80amps.
I would over build the battery yes.
Cyclomania
10 kW
Yeah I will post a bit later. Just wait for it. Have to examine and stuff. The cells I checked but I am going to check them again.
Cyclomania
10 kW
Well. So the cells are basically called ROOFER or something. Some type of China cell I guess. Looks like these and are 2500 mAh I guess. Five in parallell.
I guess the dude I got this from many years ago lied to me too haha. Because he said it was 18ah. But I guess this would make it a 12ah battery correct?
I guess the dude I got this from many years ago lied to me too haha. Because he said it was 18ah. But I guess this would make it a 12ah battery correct?
Attachments
docw009
1 MW
This is the battery that has been giving you grief for the past few weeks?
It was a 48V12.5Ah per the cell labels.
The nickel is nothing special though, constricting the full current thru two 8 mm wide strips at each series connect.. That width typically is rated for around 8A. so for optimum use that's 16A. Higher currents are going to cause voltage sag,
If you want to put on a 35A BMS and run it there, go ahead, but I wouldn't.
It was a 48V12.5Ah per the cell labels.
The nickel is nothing special though, constricting the full current thru two 8 mm wide strips at each series connect.. That width typically is rated for around 8A. so for optimum use that's 16A. Higher currents are going to cause voltage sag,
If you want to put on a 35A BMS and run it there, go ahead, but I wouldn't.
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Well do you still think the cells can “handle it”. What I see is a pack that could barely provide 25A on a good day, when new.
Cyclomania
10 kW
How do you calculate that? No, I was basically calculating based on how well it was working on this bike before. I had not checked the actual cells. But then better to use this battery for another bike then? Since this one has a rather powerful controller.
I have learned that calculation som time in the past but cannot remember how it went. I know that a low AH for individual cells usually corresponds with being able to handle higher current. Why that is I am not sure, but maybe you can answer that.
These cells individually have a quite low AH it seems to me, so should be able to handle a bit of current? And please elaborate on how you do the calculation since that is the whole purpose of this thread. You have now said A and I hope you are also going to say B and not leave me in the dark here
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docw009
1 MW
The discharge current for a cell is not a calculation. You find that information in the data sheet. The discharge current for a battery is calculated from the P number x cell discharge current,
The Roofer data is in this alibaba listing. Discharge current is listed as 3C, To get that in amperes. multiply the Ah rating by the C number. In this case, 2500 x 3. Now multiply it by 5P and it could be a 36A battery, but who ever built it used 20A nickel,
The Roofer data is in this alibaba listing. Discharge current is listed as 3C, To get that in amperes. multiply the Ah rating by the C number. In this case, 2500 x 3. Now multiply it by 5P and it could be a 36A battery, but who ever built it used 20A nickel,
There's some documentation about these Roofer cells, it says they can provide 5A discharge current. So the whole battery will be capable of ~ 25A. I wouldn't count on it doing 40A.
PS the data sheet i found: https://e-foton.pl/userdata/public/assets/Testy_ogniw/Roofer-INR18650EC.pdf - so it's actually 7.5A max, not 5A.
PS the data sheet i found: https://e-foton.pl/userdata/public/assets/Testy_ogniw/Roofer-INR18650EC.pdf - so it's actually 7.5A max, not 5A.
Cyclomania
10 kW
Ah you think it would be a good idea to fortify it with some more nickel perhaps? I have it at home
Cyclomania
10 kW
Hmm thanks man. Maybe 35amps then with some stronger nickel? What do you think? 7,5*5=37,5. If correct
docw009
1 MW
Usually when old or undersized batteries get down to half charge, the voltage sag with high current shuts them off.
It doesn't sound good though, Start with an inexpensive 20-25A ebike pack. It stopped working either due to broken BMS or unbalanced cells, It's old. Now you're going to put a 35A BMS on it and run a 35A controller? It's fine if you have the time to experiment and gain experience.
It doesn't sound good though, Start with an inexpensive 20-25A ebike pack. It stopped working either due to broken BMS or unbalanced cells, It's old. Now you're going to put a 35A BMS on it and run a 35A controller? It's fine if you have the time to experiment and gain experience.
Cyclomania
10 kW
Hmm thanks man. For the input. I think I will wait for the 40a bms I just ordered. See if it works. Yeah I can play around. I think it is interesting. To a point of course.
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Cyclomania
10 kW
I think I am going to solder on the 40 bms when it arrives. And fortify the nickel as well. Give it a shot. If it comes alive I will ride it. If it dies after that it goes to battery graveyard.
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