Dumb sas question ⁉️

[Blackgolem]

Greetings EBR I have a stupid question I've built a 14s battery with 2.55 10a Max discharge output 18650 cells. Not the problem what is and don't laugh, I have a 350w brushless motor was the a max of 12a in a 12.5" hub. I'm using a 1000w 38a 60-120° 38a max controller. Should I use the 15a max BMS or the 35a one I'm thinking about. Will the motor only call for what it can handle?

 

[rich c]

No the motor will not call for anything. It's just a simple device, the controller sends the current you program it to send.

 

[Blackgolem]

Thanks for responding so if my motor says it has a 12a max that won't be n play?

 

[Blackgolem]

What's been happening Rich c is I give throttle and hit lvc it makes an awful noise any idea why. I had put a 20a BMS on it and went from twist throttle to a thumb 13s is 4p everything was fine before the BMS switch. What you think should power this scooter

 

[AHicks]

Thanks for responding so if my motor says it has a 12a max that won't be n play?

That 12a motor will take anything you feed it. They get REAL sporty at that point! BIG, very noticeable performance increases possible. The issue is how long will it last prior to overheating/smoking! Unless you get carried away, over powering it (for a few seconds) won't hurt a thing.

I believe the issue you're going to run into is with the BMS shutting the power down as it approaches/exceeds it's capacity. To avoid/prevent that, you will probably want to turn the controller down so it will only pass the amount of power that will keep everybody happy/playing well together. That's one of the big reasons better controllers allow you to do that.

 

[Blackgolem]

Sounds good AHicks how do I do that in layman's terms you know step by step?

 

[Blackgolem]

That 12a motor will take anything you feed it. They get REAL sporty at that point! BIG, very noticeable performance increases possible. The issue is how long will it last prior to overheating/smoking! Unless you get carried away, over powering it (for a few seconds) won't hurt a thing.

I believe the issue you're going to run into is with the BMS shutting the power down as it approaches/exceeds it's capacity. To avoid/prevent that, you will probably want to turn the controller down so it will only pass the amount of power that will keep everybody happy/playing well together. That's one of the big reasons better controllers allow you to do that.

Oh so I know from the internet that if you shunt the controller you get.more amps but how would I limit the amps?

 

[harryS]

If you hit LVC when you twist the throttle, I think the battery is too small for the current demanded by the throttle. Maybe crack throttle just a little.

Have you always used this controller? Or is it a new battery. What kind of cells did you use? 2.55AH cells with a 10A peak current in a 14S-4p is what I read. New or salvage cells? Brand? Spot welded or soldered?

 

[Blackgolem]

Salvaged cells from 36v led light packs bought 160 for a Benny they look genuine double ring at top Had a mixed batch of cells before thinking different max output probably was wrong to do. These are all the same being rated at 2.55 mah when tested they run about 2778mah and 9780mwh I'm thinking these are close to a 3c rating maybe a 6p would be better.

 

[Blackgolem]

Salvaged cells from 36v led light packs bought 160 for a Benny they look genuine double ring at top Had a mixed batch of cells before thinking different max output probably was wrong to do. These are all the same being rated at 2.55 mah when tested they run about 2778mah and 9780mwh I'm thinking these are close to a 3c rating maybe a 6p would be better.

Oh spot welding all I think you hit the nail though because I had 3000mah cells with 2500mah cells in a 4p pack. Always have had these 1000w controllers for a year now no real problem. Should my BMS be rated higher than 15a?

 

[AHicks]

I think the answer to that question is going to be about your expectations?

Are you after reliability, or reliability be damned, I want to see how fast I can make it?

Are you OK with the idea there's a good chance that if you play to hard with this motor you could smoke it?

Is your controller output NOT able to be configured? Do you have/have you looked at the manual for the controller?

 

[harryS]

The label say ICR1865026V cells. I found this data sheet from secondlifestorage.com and also a manufacturers data sheet.
Max discharge is indeed 3C, or 7.6A, but your cells are used and who knows what the internal resistance is. It seems high enough to wipe out 16 volts if your display shows LVC on full throttle. I assume you can watch the voltage in real time.

I think you need to try 8P. That would halve the voltage sag if IR is the problem. How good are the welds, by the way.

I bought a toy welder ($40) and it was Ok to repair a battery, For building, the internal battery lost too much power after two dozen welds, and they were weak. I took a 10S-2P and made it 10S-4P, and the welds on two groups lifted. so it was still a 2P battery. I fixed that, but I also used cheap cells, and I will never use unknown cells again. I'm also out of the spot welding game until I get a tool I can rely on.

 

[Blackgolem]

I think the answer to that question is going to be about your expectations?

Are you after reliability, or reliability be damned, I want to see how fast I can make it?

Are you OK with the idea there's a good chance that if you play to hard with this motor you could smoke it?

Is your controller output NOT able to be configured? Do you have/have you looked at the manual for the controller?

Will have to look in the morning I don't think it's adjustable but will check it I just use to run to store less than a mile away trying all wheel drive to lessen burden on motor. I don't think these xbrain controllers are configurable.

 

[Blackgolem]

The label say ICR1865026V cells. I found this data sheet from secondlifestorage.com and also a manufacturers data sheet.
Max discharge is indeed 3C, or 7.6A, but your cells are used and who knows what the internal resistance is. It seems high enough to wipe out 16 volts if your display shows LVC on full throttle. I assume you can watch the voltage in real time.

I think you need to try 8P. That would halve the voltage sag if IR is the problem. How good are the welds, by the way.

I bought a toy welder ($40) and it was Ok to repair a battery, For building, the internal battery lost too much power after two dozen welds, and they were weak. I took a 10S-2P and made it 10S-4P, and the welds on two groups lifted. so it was still a 2P battery. I fixed that, but I also used cheap cells, and I will never use unknown cells again. I'm also out of the spot welding game until I get a tool I can rely on.

No I can't monitor in real time unless you consider the digital thumb throttle display of voltage. I hate when tabs lift I diy'ed 1 of those MOT spot welders, I can't tear off cells easily but it took some time to dial it in. Now don't ask delay time b'cause I can't say at any rate I will use all this info thanks I will.come back and let you know what happened. Thanks for the info bro

 

[harryS]

The digital thumb display is good enough, as it's all relative. I have a little digital readout on a few of my bikes too. I use then to watch voltage sag. I might get 4-5 volts pulling 20-25A on those bikes.

If you're seeing a drop from the 58-59 volt of a fully charged 14S down to 44 V, that's a pretty weak battery,

 

[Boynextdoor]

The label say ICR1865026V cells. I found this data sheet from secondlifestorage.com and also a manufacturers data sheet.
Max discharge is indeed 3C, or 7.6A, but your cells are used and who knows what the internal resistance is. It seems high enough to wipe out 16 volts if your display shows LVC on full throttle. I assume you can watch the voltage in real time.

I think you need to try 8P. That would halve the voltage sag if IR is the problem. How good are the welds, by the way.

I bought a toy welder ($40) and it was Ok to repair a battery, For building, the internal battery lost too much power after two dozen welds, and they were weak. I took a 10S-2P and made it 10S-4P, and the welds on two groups lifted. so it was still a 2P battery. I fixed that, but I also used cheap cells, and I will never use unknown cells again. I'm also out of the spot welding game until I get a tool I can rely on.

Thx for sharing. But what is the minimum allowable welder suitable here instead of a toy welder(MIG welders reviewed)? It's risky to my mind

 

[harryS]

Let's take the welding out of the problem. The problem is you have 64 cent used cells, and not enough of them. Bypass the BMS temporarily for a test run, you'll see the same behavior.