Lithium Ion Battery Problem On Oset 20 2014

[scottk]

hi guys, the battery has a bms. It runs constant 54v so a little high, the result is it makes the bike fly. I haven't checked amps but will do tomorrow.

When I put the lead acids in the bike behaved normally, so I am convinced its not the motor but a power delivery problem that the oset controller is not dealing with.

I have spoken with Kelly and they have a controller that you can program via a PC. You can set the slow speed and high speed for both ACCELERTION and DECELERATION. I'm thinking that by modifying this low speed DECELRATION it may stop the cut out then cut back in again when you are doing throttle off, throttle on trials.

Cost is $150 USD so not a major.

 

Here is the info sent from Kelly, appreciate your feedback

In this case,I will suggest you use our SPM48151 controller for this motor.

The SPM controller can provide smooth control.

You can adjust the acceleration or deceleration rate in the user program of the controller.

We added smooth control in the user program.
It is used to set up the throttle map by customers.
The deflection point will divide the low speed and high speed on the throttle map.
We added the smooth control parameters in the user program.
When you enable the smooth functions,you will see five more parameters.
You can adjust the low speed acceleration and deceleration rate,and high speed acceleration and deceleration rate in the user program.
The inflection point is at the joint of low speed and high speed.
But this new software version needs the new firmware and hardware to support.

Usually you can set deflection point at 10.
Low Acc rate is 100
Low Dec rate is 127
High Acc rate is 100
High Dec rate is 127

The deflection is used to define the point for low speed and high speed.We assume the max inflection point is MAX.
For example,if we set up the inflection point at 10,we think the range below 10/MAX point is low speed area,the high speed range is above 10/MAX.
When you adjust the inflection value,you can determine which point is the joint for low speed and high speed range.
Different motor or motorcycle will affect the value of MAX.I can not let you know the accurate rate.

So we can accelerate and decelerate the motor at low speed range and high speed range.

Low Acc rate is Low speed range acceleration performance rate.If the value is high,that is to say,the controller will accelerate the motor very fast at low speed range.If the value is low,the acceleration is slow or gradual.
Low Dec rate is Low speed range deceleration performance rate.If the value is high,that is to say,the controller will decelerate the motor fast,the motor will stop quickly after throttle is released.

High Acc rate is High speed range acceleration rate.
High Dec rate is High speed range deceleration rate.
The explanation is the similar as above.They only just located on high speed range.
You can assume the value is just the response time.There is no unit for the value.Sorry for that.
Different motor,cars will provide different results under the same value.
You need to tune up the parameters according to every vehicle data in real testing.

　

[gwhy]

54v is about right.. and no more than a sla 48v should be when fully charged which are around 56v hot off the charger. Ok my guess is that its the bms and that it can not supply the needed current to the motor... its nothing to do with the controller, motor or throttle if the bike is 100% fine on the sla's..

 

what is the spec of your battery/bms , peak and constant current. 

 

because the battery chemistry is better than sla the voltage will not sag so much and this in turn means it can deliver a lot more watts/power to the motor and this increase in power is tripping the over current shutdown on the bms

 

a decelerate function on any controller is not a good thing as this in it self cause a lag between throttle movements . 

 

 

[scottk]

Over current is 10amps. Battery guy said if it trips then bike will shut down.

He feels that controller is not up to the instant power and on off nature of lithiums.

I'll run some tests with battery tomorrow and check amps and volts out of controller.

One thing we saw was that there was an instant supply of volts on and then off with Li vs much slower with sla

[scottk]

Question. What is the current needed for the motor?

[gwhy]

peak current would be around 40A (min )  and upto the current limit of the controller.. some test I done with the 20 controller peaked at well over 140A but this was a maxed out controller.

 

so if your bms is only rated at 10A then this would explain why its cutting out.

 

trust me the controller is more than capable..

[scottk]

Hi GUDAH and GWHY

 

more info on the battery. Its lithium ion, 48v 20 AH. Discharge after testing is constant 54v and 60amp with a maximum amp cut out of 100amps. I cant ride it on full power without flipping it.

This should be more than enough, perhaps to much for the OSET controller but we haven't had a cut out yet. So its not an underpowered problem I believe.

 

I'm trying to find out if the EM throttle would be a good starting point to get rid of the dead spot (my EM throttle is so smooth) and then looking at a throttle response option with a Kelly controller that is usb programmable

 

I wont look at the motor until we go down that route unless you have any other ideas? The oset guys said they could put a 2015 map on my 2014 controller but I reckon I might be better to just put in a Kelly at $159 usd that I can map myself

 

love to hear your thoughts......

[gwhy]

if the em throttle is a pot throttle and you are using the original oset controller then it will create a bigger dead spot ( there are ways around this.. PM me )..

 

the oset controller can and do cope with a lot more current than your bms can supply .. 

 

do you know what the current limit is set to on your controller ?

 

I would say that a cont of 60A and peak of only 100A is very borderline to be able to deliver enough power to your motor. 

as I have said the oset 20" controllers can do more than 140A peak so you need a bms that can match this to be sure that the bms is not tripping. a 100A max is not ideal on a 20"  would be fine on a 16" tho

 

a different controller will not solve your problem ( if it is the bms tripping ) unless you turn the power down on the controller ( not speed ).

 

 

[scottk]

The bms is not tripping. If it does battery dies and key needs to be turned off.

As the controller is rated for 20 - 100 watts (Oset doc) im surprised you say 60 amp continuous isnt enough?

60 amp x 54 v = 3 kW to a 1200w motor. Peak over 5 kW at 100 amp less system loss.

Seems a heap for a rider and bike weight combined of 60kgs.

[gudah]

Not sure if i remember it right but my teacher used to tell us that electric motors can pull six times the nominal amps at startup, so always keep that in mind designing circuitry and fusing.

(This is why they have a massive torque at start i suppose, Tesla, anyone?..).

Sometimes i wonder if huge capacitors in parallell with the batteries would help, the car-audio guys used 1F caps to help carbatteries produce tons of watts in the ninetys cranking-competitions and ghat was plenty of power during some hundreds of milliseconds.

As soon as a dc-motor starts turning the worst hunger for amps goes down a bit but they surely

Can whoopass with petrolengines when it comes to torque, i discoverwd the other day after installing brand new slas in my 20" resulting in a 180 backwardflip feeling schtupid on the asphalt..

[gwhy]

the 20" controller can do at least 7.5kw ... tested.. thats not saying that the motor can push out that much but thats what the controller can deliver

 

so 100w must be a typo

 

some bms has two stage protection, it has a hard cut off and a over current trip and depends on bms design to how it handles these 2 errors

you could even have a weak cell in your battery causing it to cut out. As you say it works 100% with the sla's the the only thing it can be is your new battery/bms.

The oset hardware is able to handle nearly double what your bms is rated for but your oset controller may not have such a high current limit than the one i was playing with so you really need to know what is the current limit on your controller to move forward .. from the info you have given then i would strongly suspect the battery/bms   im not saying that it is not functioning correctly it just may not be up for the job. 

60A cont for a controller that has a current limit of more than 60A then the bms will trip under certain conditions .. and 60A is not that high on a low voltage system. 

 

get your battery guy to disable the bms just to test  or see if you can borrow another Li battery that dont have a bms ( most 20" users use Li )..

 

 

Motors will pull as much current initially as it can and normally the controller will limit the current,, a stalled motor will have very,very low resistance , even if it was as high as 0.5ohm  you can see how much current it will pull if it was allowed to by using simple ohms law  i.e 50v/0.5ohms= 100A but in reality motor are normally well below 0.5ohms, some of the motors i play with have a resistance of 0.01ohm so a stalled current would be 50/0.01=5kA  the controller/bms needs to be able to limit this initial current and if the bms is hitting its limit before the controller then the bms will shut the controller down. 

 

These sort of problems are very difficult to pinpoint as its a chain reaction and sometimes the only way to find the problem is to use a data logger and get real time volt/current/throttle readings .. 

 

If it was not for the fact that you said it works 100% with the sla's then I would still be looking at the motor/throttle and connections

 

 

[scottk]

Hi. I meant 100 amps sorry. At full power from a start with me on it won't cut out. In fact I can't keep the wheel down.

The cut out is not under power just when you back off the throttle. No demand for power = instant kill of supply. That's with the throttle on the stop.

When you throttle on again it engaged fine. However engagement speed is lower than rolling speed hence the bike brakes like engine braking.

What this means is if your not gassing the bike then it's jerky at low speeds.

[gwhy]

do it do this with the wheel off the ground?

 

if I didn't know you have a new battery then from what you have described above then I would go back to the original thing to check which is the motor and brushes..

 

but as it don't happen with the sla's then that makes it harder pinpoint the problem, the only thing I can thing of as to why it does it with your new battery ( if it is the problem ) the higher current/heat/arcing through the brushes may be making them stick in the holders and sticky/worn brushes can cause these symptoms 

 

 

[scottk]

I didn't manage to do amp testing today, as sparky was closed but heres an email I've sent to Oset, based on the fact I'm using both Lithium ion, LIPO and SLA in diff bikes I can rule out the battery I think. Bikes are EM 5.7, Oset 20 eco 2014, Oset 16r 2014, Oset 16 2012 (eco)

 

start email

 

I did some more testing on all the bikes today up on stands.

EM - smooth progressive acceleration, smooth deceleration
Oset 16 2012/ china smooth progressive acceleration, smoothish deceleration

BUT.....

Oset 16R 2014 - smooth acceleration but when you back off throttle, it doesn't stop the wheel spinning, it continues flying until you get the throttle back to zero and then boom, its stops (this has a lithium battery)

Oset 20 eco 2014 - using lead acids, same throttle response as the 16R.

This is why it is jerking so badly as effectively there is no deceleration from the controller or the throttle, the kids have to back it right off to slow down, which kills the power completely to the motor, then reengage.

I was curious to why the wee boy on the 16r kept jerking the throttle of and on and not being smooth with it. now I know.

Does this sound like a faulty controller or throttle you either of you?

[gwhy]

 

Oset 16R 2014 - smooth acceleration but when you back off throttle, it doesn't stop the wheel spinning, it continues flying until you get the throttle back to zero and then boom, its stops (this has a lithium battery)

 

 

this points to the throttle .. but it would do this with sla's 

 

when you start to back off the throttle ( back wheel off the ground ) you say it do not slow down until you hit the zero stop on the throttle ?  is the wheel still being powered or is it coasting until zero stop ?

 

if the motor is still being powered as you wind down the throttle then its not the motor and still points to the throttle.. or its a torque only controller 

 

as the bike behaves with the sla's the im sure that its nothing to do with the controller .. I would defo get a replacement throttle first ( unless you know how to test its function using a voltmeter, its pretty easy to do ) but other than that it must be to do with controller,, but cant see why as there are a lot of people using the same setup as you ( Li on the 20" ) without issue so its all a bit odd... 

 

the only real difference between sla and li is the internal resistance of the battery so it could be that the controller sees this lower resistance as a fault but as i said lots of others are using Li setups without a problem.

 

the controllers may be torque control controllers not speed based controllers and this will have very odd effects on the stand as there needs to be a load on the wheel for the controller to work correctly , but again it will be identical if using sla's. I know the EM has a torque base controller but it is set up for 50/50 i.e a torque/ speed setup

There are many control methods and lots of different ways that they are implemented which all adds to the confusion when trying to find a problem.   

[gudah]

Does any of you know what the controller does with the energy from the motor at deceleration?

Does it open circuit, quench, or send the energy from the generator(motor) back to the batteries?

(A li battery compared to a sla is a bit like compairing a 1600cc Fiat turboengine to an old chevy 5700 cc smallblock V8 putting out 180 bhp each but in two totally different manors, due to their difference cc/in internal resistance).

In your case having several biles at hand, i'd try one of the other bikes throttles if possible to rule out errers on that part.

Sorry for spellings, just as drunk as yesterday:-