Bike electrics cutting out

[jic]

Very good.
Connecting a volt meter during a ride or hobby watt meter as Harry suggested can help with diagnosis. My Fluke meter has a Min/Max function that allows me to view and record voltage drops and with an audible tone to alert me of a new low reading. The hobby watt meter is a lot more affordable if you have neither. To really know what's going on you need to know what the voltage is just prior to time of shutdown and how deep any battery sag is. Does your display provide a voltage reading?
Since you have the new controller and don't seem happy with the current one anyway you might as well change it as you say.

I've just got a throttle with a voltage output. But that shuts off too.
I have a decent multimeter but nothing like that im afraid. Ill connect it up and see what happens.
May get this watt meter you're talking about aswell.
Thanks!

 

[Gionnirocket]

I believe this is similar to what @harryS uses. WattMeter
I think it'll provide you with the a recorded low voltage

 

[K PierreR]

Yeah i get a full charge at 58.8V. The bike will restart and the power comes back on but i don't get very far before it shuts off again.
Thanks for the info. I've just got the new controller so will see how it goes. If that shuts off then I can be sure it's battery.

With this sentence you problem is 100% battery sag. The cells you are using might be okay but most of the 2,500 mah cells that I am aware of do not have a low C rating. On top of that 12.5 amp hour is just not enough battery for those cells. Your battery is probably cutting out around 42-43 volts and then recovering to 48-49 before you can measure them. It takes a much bigger battery to get the full amp hours out of it to power a bike.
Even with a 14 amp hour 14s-p4 battery capable of delivering the amps I needed continuously, I could seldom get more than 490 watt hours out of a 725 watt hour battery unless I drastically reduced the power.
Your battery is probably fine. Its just not up to the task you are asking it to do. I got tired of it. Now I have a 14S-14P, 49amp hour battery and don't sweat it. I still experience some battery sag but not enough to cut out before I drop to 46 volts were I stop it.

 

[Gionnirocket]

With this sentence you problem is 100% battery sag. The cells you are using might be okay but most of the 2,500 mah cells that I am aware of do not have a low C rating. On top of that 12.5 amp hour is just not enough battery for those cells. Your battery is probably cutting out around 42-43 volts and then recovering to 48-49 before you can measure them. It takes a much bigger battery to get the full amp hours out of it to power a bike.
Even with a 14 amp hour 14s-p4 battery capable of delivering the amps I needed continuously, I could seldom get more than 490 watt hours out of a 725 watt hour battery unless I drastically reduced the power.
Your battery is probably fine. Its just not up to the task you are asking it to do. I got tired of it. Now I have a 14S-14P, 49amp hour battery and don't sweat it. I still experience some battery sag but not enough to cut out before I drop to 46 volts were I stop it.

This is why I prefer increasing capacity over voltage in the 48v/52v battery debate. Using better quality cells with a minimum of 3500mah makes for a better build as well...

 

[K PierreR]

This is why I prefer increasing capacity over voltage in the 48v/52v battery debate. Using better quality cells with a minimum of 3500mah makes for a better build as well...

Give me 52Volts. Its only a few more 18650 cells. Theoretically you can pull 10 amps per cell so a 4P should yield 40 amps but don't try it for long. You pull 10 amps total, 2.5 amps per cell and you will not get anywhere near the watt hours advertised in a GA cell battery. My present battery has 14 cells and I have pulled 8 amps continuous and still noticed some sag in the numbers.

 

[Gionnirocket]

Give me 52Volts. Its only a few more 18650 cells. Theoretically you can pull 10 amps per cell so a 4P should yield 40 amps but don't try it for long. You pull 10 amps total, 2.5 amps per cell and you will not get anywhere near the watt hours advertised in a GA cell battery. My present battery has 14 cells and I have pulled 8 amps continuous and still noticed some sag in the numbers.

Well then you just proved my point.
All battery packs will have sag.
If your goal is high performance short rides... By all means go 52v. But after you've dropped from 58v to 54v you've burned through any extra performance
But for the average user who only requires normal performance and longer rides.. the cells are better off configured in 48v and with more groups in parallel.

 

[Davie]

I too h have had problems with an 13s6p it starts off fine,but if I try to push it at higher levels after a dozen kilometres it stops if I wait 5 minutes it starts again and then after a minute it stops again, am I trying to much on my 500w ebike engwe ep2. Is the battery to big can someone please advise.as it is distance over speed I require is 13s6p wrong for my 48v controller, please advise

 

[harryS]

Davie, is it this 20" Engwe folding fat bike? It's sold with a 12aH battery.

From a performance point of view, the battery is never too big. If you can have more AH, you're better off. From a physical view, bigger batteries may not fit in the bike. I didn't think those enclosed frame bikes would have room for a 13s6P.

Without any other info, a quality 6P battery should be capable of 18Ah. Your symptoms are battery sag. Pack may be too small. If so, they lied about the 6P. If not, then they used cheap cells or some cells are unbalanced.

 

[Davie]

Thanks for the reply,it is the 20" folding bike it comes with the 12ah battery of which I have two. At 300 euros each I decided to build a bigger battery cell hence the 13s6p. But checking on the controller which is very small hidden in the frame.the model is x008-aam003.battery v 48v, cut off point 39v,current limit 18 amps. But I think the 13s6p has to many amps at high volume so the bms switches off the power. So I think the small controller can only do a maximum of 12ah .and no more, so my next experiment will be 13s4p which will be 12ah . I will reply back again after this test. As I am a novice to battery building.and my next bike will be the mx-02s 1000w . Thank you again for your assistance.

 

[harryS]

Davie, I have to disagree with your theory. The controller is what determines the battery current. It can only pull 18A.

What kind of battery did you build? Is it spot welded pack or is it a Lego block style using plastic forms, pressure contacts, and screws? The block style work best with smaller batteries. When you make them 6P, you start getting bad contacts here and there, and you might get what you see,

 

[Davie]

Spot welded with nickle strips,so am I wrong in thinking that the 18 amp controller can not handle the 30 amp power the 13s6p is producing. And that it doesn't matter the size of controller which runs to my back rack in my holdall.

 

[JES2020]

Spot welded with nickle strips,so am I wrong in thinking that the 18 amp controller can not handle the 30 amp power the 13s6p is producing. And that it doesn't matter the size of controller which runs to my back rack in my holdall.

Your controller, if peak amps are 18, will not put out 30 amps peak to the motor.
When you say your battery is putting out 30 amps, do you mean it has 30 AH capasity?

 

[Davie]

No I think it's about 27 ah

 

[JES2020]

No I think it's about 27 ah

So if you want 30 A to the motor you will need a 30 A controller.
The controller is what determines the amps to the motor NOT the battery.
You could put a 60 A controller on a tiny battery and it would just drain it really fast.(and possible burn out your motor)

 

[Davie]

So is the 18 amp controller able to take any size battery even a 13s10p.I was thinking of using a 48v 30amp controller, then I could use a larger battery.

 

[Gionnirocket]

13s gives you your voltage and you match this to your controller and motor. 13 x 3.6v/cell = 46.8v or nominally 48v
10p or what ever *p gives you your amp/hour depending on the cells used. In a way think of this as your gas tank. It doesn't matter to a motor if you have a 10 gallon or 15 gallon tank. The bigger tank just gives you longer drive time.
The controller amp is what governs the maximum amount of power delivered to the motor. It should be matched to the motors capabilities.
That said... Larger motors coupled with the higher current controllers should be matched with greater output (more cells in parallel) batteries as they will draw more more power. 250w vs 500w
Harry's answer above is correct about your problem... Poor quality cells and/or not actually 6p.

My current battery as an example.
Battery Cell: Samsung 35ET 3500mah.
Array mode/Capacity : 13s5p: 48v / 17.5AH
I have no problem using this battery with a 750w/25a - motor/controller with minimal sag
Numbers are usually rounded up by battery builders so keep this in mind.

EDIT: One factor often overlooked is the battery Discharge Current. This is the batteries ability to deliver power continuously.

The Samsung cell is capable of delivering 8a continuously... So in a 5p battery this results in 40a continuously, hence the minimal sag. This is where many of the lower quality cells fail and why they should be avoided. You can think of this as the ability to delivery gas to an engine. Dating my self here but... a 2 barrel vs 4 barrel carburetor on 1960's cars.
When building a battery my opinion is to over build as far as capacity and current as this will keep the cells from stressing (heating up, a cells #1 enemy) and be more viable as it ages

 

[JES2020]

So is the 18 amp controller able to take any size battery even a 13s10p.I was thinking of using a 48v 30amp controller, then I could use a larger battery.

Its best to match your components voltage, 48v battery should have a 48v controller. You can over volt a motor but you need to be careful of how long you over volt it. Under volting a motor won't hurt it but you lose the full capacity.
Amps give acceleration, volts give speed, amp hours give range.

 

[Davie]

I repeat the controller box is very small has a current max of 18 amps so when I run a battery that has maybe 30 amps. Is it the controller that cant handle the input from the battery,I will test again at a lower speed pass 1 less than 20 kph. Did 10 kilometers no problem then tested for a short time. Now I am going to try again battery at 51.4 v

 

[Gionnirocket]

I repeat the controller box is very small has a current max of 18 amps so when I run a battery that has maybe 30 amps. Is it the controller that cant handle the input from the battery,I will test again at a lower speed pass 1 less than 20 kph. Did 10 kilometers no problem then tested for a short time. Now I am going to try again battery at 51.4 v

No... Not at all.
The 30 amp is the amount of power available, not delivered or forced into the motor/controller.
Not wanting to insult you... But you really should understand this and much more before building / experimenting with batteries as this is a rudimentary and essential understanding needed of what you are working with.

 

[Davie]

started at 51.4v pushed bike at pass 3. Two kilometers then died 50.8 v. Waited 2 mins started pass 1. no problem could ride 80 kilometers at low speed controller no problem,only when ask for more power at pass 3 the bike switches off.i can only think the controller cant deal with the request of more power and speed the power is there but it wont pass through the box at anything over the 18 amp cut off point. So I think its reduce the battery size or increase the controller size to handle at higher ampage