NEED HELP ON SXT 1000W 36V E-Scooter

[iacei]

Hi Folks,

I have bought a SXT 1000W like scooter (actually mine is called E-flux Vision)

It works with 3 SLA Batterys = 36V and this kind of Speed controller:

To stay on the safe side I replaced the SLA with a Liion battery of the same voltage:

I had to disable the 20A fuse because it was too low and I kept a 30A fuse just for safety. I changed the connector also.


On the Speed controller I made just a simple shunt mod.

It kinda works but after 10mn the scooter runs very slow and a on and off with the key does not change anything. If I replace the battery with the sla, it's working again.

What am I missing? Is it linked to the "out of control" mode?

 

[iacei]

Ok... After blowing up the fuse with the standard fresh charged SLA battery I bypassed it and reworked a bit my shunt mod (only solder, no extra copper wire)

Now I can't reproduce the issue with both batteries....strange.....

I monitored the liion battery voltage under max load: 34V

 

[Ykick]

Can you insert a power meter between battery-controller? That would best help determine what's happening?

You mention after modding the shunt, it does (or doesn't) do the same on original SLA? Is that same riding about 10 minutes and then shuts off? I'm having a hard time following you there....

35A rated controller may just be hammering the shit out of the batteries and especially after soldering the shunt?

New lithium pack shutting down 34V could be the pack BMS? What is that pack when fully charged? 40-42V? You have fully charged it, yes?

SLA may just be hitting the 31V controller LVC after the shunt mod?

 

[iacei]

Some extra Infos:

Liion fully charged is 42V

I opened the Liion and there is NO BMS

I never Had Problems with the SLA, only 30A Fuse blown up due to the shunt mod which allows more current.

here pictures of the inside of the controller with old shunt mod

shunt mod rework

 

[Ykick]

Now I can't reproduce the issue with both batteries....

So, is there a problem?

Sorry I'm not following things better here...

 

[amberwolf]

I monitored the liion battery voltage under max load: 34V

Sounds like the battery is unbalanced (not all cells the same voltage/charge level), so the controller is cutting out due to the voltage sagging too low, or some cells could actually even be reversing (which could cause a fire); without a BMS you would want to manually monitor individual voltages while under load to see what's happening.

If this is the case, since there is no BMS to balance them, you'd have to manually balance each cell to match all the others. This might fix the problem, at least for a while. (if cells are actually bad then it won't stay fixed).

Or, the battery could simply be unable to supply the current needed, which because of the shunt mod is essentially unregulated. Not all batteries are created equal; some are built to supply more current, while others are made for more capacity (and may not be able to handle higher currents).

If the 20A fuse was in the new battery itself, then that means that battery is only supposed to be used with loads less than 20A, and if you use it at higher loads the results will not be as desired, as it isn't made to handle that.

 

[iacei]

Now I can't reproduce the issue with both batteries....

So, is there a problem?



Sorry I'm not following things better here...

No Currently I have no more problems. The only thing that bothers me is the voltage sag on my liion (34V) and the fact that I think the Liion I bought is crap (it was "only" 275$ for 36V 15Ah)



I think that it won't let me do more than 5kms, after that the voltage will drop too low to be usable. I think my liion sucks and cannot handle the Amps. I was disappointed when I opened it up and saw no BMS and no 18650 cells.



Where can I get good 18650 cells shipped to EU?

Alternatively I could buy lipos 2x5s but will have to change the esc to handle the current. Any suggestion?

 

[Ykick]

Ok, understand.

That does sound like a disappointing pack.

I don’t think you’d need to change ESC current parameters for 10S1P (2x5S) RC Lipo battery pack. The sensible voltage range would be roughly 35-42V. Although it should be able to go 31 LVC that could be a little risky depending on how out of balance the RC Lipo becomes?

But honestly, 31-35V from 10S RC Lipo is about the length of a football field in real world use with that chemistry.

 

[iacei]

How to be sure that with the shunt mod and rc Iipos I won t go over 35A the limit of the esc?

Because rc lipos can deliver a huge load of amps

 

[Ykick]

True, good health RC Lipo can often deliver solid/stiff power but 10S is still within reasonable voltage range for your controller. You can also remove the solder you added or perhaps partially "cut" the shunt a small amount?

But the best way to qualify such modification is by inserting a power meter. Plenty affordable RC industry choices out there - I’m happy with most of the G.T. Power meters eBay under $20USD shipped.

Of course, the 2nd part using power meter will be good solid connections and wiring. Automotive stuff really isn’t up to the task. But the RC world can offer many fine solutions for this type of need as well.

 

[iacei]

Power meter ordered

Next Step Buy Lipos and an upgraded ESC like this one

Not sure if it will be needed but with the shunt mod the 35A one might blow up.

 

[Ykick]

Spare controller is always good. You're on a good path.

 

[iacei]

Could someone point me to an alternative 36V 40A controller? I cannot find one on ebay...

 

[iacei]

Here the batteries I just ordered:

2 x 5s 10000mAh = 2 x 90$ shipping included

http://www.banggood.com/ZOP-Power-1...60-Plug-p-1021730.html?p=A720061271257201502N

If I get a big Voltage sag, I might replace a 5S with a 6s because they have the same 10000mah in 6S

8% coupon ToysHo at this time!

I will do a post on why I choose to order on this website.