Motor wants to much amp while pulling up

[bendeman]

Hello,

I have a 2000watt 72v elecktric scooter.
i have build a 30ah 70v 18650 batery pack.

but when i pull up with the scooter it wants to much amps so the voltage drops to 50v and the motor shuts off. ( protection mode or something )

when i slowly pull up there is no problem.

is there a way to make the scooter go slower on full trotje at the beginning?

thanks

sorry for my english.

 

[amberwolf]

Don't use full throttle.

or

Program the controller (if possible) to a lower wattage setting. This will affect *all* usage of it, so you will no longer have the power you had before.


What you really need to do is rebuild the battery so it can support what the scooter requires for power, without so much sag, and that goes up to the right voltage.

A 72v scooter, if it originally came with SLA, would be closer to 80v fully charged, and would be made to expect a lot of sag, down to possibly 60v or further at high current.

If the pack you've built is 70v nominal, rather than fully charged, then it, too should be close to what the scooter expects for full charge. But if it is only 70v when fully charged, then it's not enough, if the pack sags a lot (like yours does).



Which cells did you use, and from what source?

How are they hooked up? (how many series and how many parallel)

There are different kinds of 18650s and some can handle higher current than others. If they are recycled from other sources then you would have to test them all to see what they can handle (there are numerous threads about that if you look around), and use only the ones that can do what you want, and use enough of them in parallel to handle the current needed.

 

[Sunder]

If your battery is sagging more than 22v on drawing less than 1C, it's junk. Sorry, no point beating around the bush. 2000w/72v = 27.8a. That's less than 1C.

If you have a look at a reputable manufacturer, like Panasonic, a 1C discharge sags the voltage about 5% at full, and 10% near empty:

https://endless-sphere.com/forums/download/file.php?id=85060

I'd say there's several possibilities here:

1. The seller has lied to you about the capacity
2. The seller has lied to you about the power density
3. A large percentage of the cells are faulty
4. The controller is permitted to over-draw current and 2000w is a soft limit (E.g. It could have a 4kw limit for 3 seconds to start the bike)
5. Any combination and all of the above

 

[bendeman]

hello,

the 18650 cells ar rated at 5a. 2400mah. the are new and come from a good celler.

its 13s 18p or the other way around, 18x4.2 to get the 74v.

and yes its fully charged 74v so that is a bit low indeed.

but still i do not want to make the pack bigger.

i just want to get slower when i give full trotle.

i also think the previous owner did someting to the scooter,
so mayby it can drain more then the 27amps at the beginning. the scooter has a lot of power.

mayby a special trotle or a pot meter in the trotle?

thanks

 

[amberwolf]

If you're changing the throttle signal by changing the throttle itself, or adding a pot to it, then don't waste the time and energy--just don't use full throttle if you don't want to use full power. Altering the throttle is doing exactly that anyway.

If you want to change how much power is actually being supplied by the controller to the motor, and how much the controller pulls from the batteries, you have to change the controller itself--either it's settings (if possible) or physically alter it's shunt or other electronics to prevent it pulling as much power.

Or just get a different one that can be programmed (either via it's own on-scooter control panel / LCD, or via USB or serial from a computer), and replace the original controller with it.



By far the simplest way to deal with your problem is just not to use full throttle when you know it is going to cause too much power to be drawn from the battery.



But the best way is to fix the pack so it can provide the power the scooter is asking for, once you have measured how much current it is actually drawing.

 

[bendeman]

Hello,

I can just dont use al the trotle. But the problem is that my girlfriend also wants to use the scooter.
And well, she is a girl so its to dificult for her....
Its a chinees scooter so its not programmable.
Putting a shunt somewhere is a option but i dont know where.
Is there a picture ore somting?
I can also make a picture of the controller if that is what you wnat.

Thanks

 

[spdas]

If you are fully convinced the amps\volts controller are correct, in spite of the suggestion above.
And
Not able to limit your wrist action to 1/2 twist on the throttle

Then you will need to:

Get a Cycle Analyst to program your wattage
or
fashion a stopper or some block on your throttle to limit to half throttle until you or your GF can judge the proper take-off throttle twist.

francis

 

[Sunder]

I'm pretty sure making modifications to the throttle or controller may be masking a problem.

A 74v (18S battery) sagging to 50v? That's a 33% voltage sag. If those cells were genuinely 2C rated (Less than 5% sag at 2C), then he's got to be drawing way more than 60A out of that battery, or 4.4kw.

The maths just doesn't add up.

You might say that the seller is reputable, but even reputable sellers have faulty goods - it's the way they handle it that makes it the difference. And if you're talking Ebay\Other online market feedback, check out this guy:

100% Positive, 5 Star feedback on 9800mah 18650s. Just a hint. When the best battery manufacturers in the world, Panasonic, Samsung, Sony, LG etc. Can't get 4000mah into a 18650 on $20 a pop cells, these no-name Chinese manufacturers must be working miracles to not only get nearly triple the best batteries on the market, but also do it at half the price and throw in a charger as well.

https://www.aliexpress.com/item/Original-GTF-2-pcs-18650-battery-3-7V-9800mAh-rechargeable-li-ion-battery-one-charger-for/32564598413.html?spm=2114.01010208.3.9.k1QcNt&ws_ab_test=searchweb201556_0,searchweb201602_5_10057_10056_10065_10068_10055_10054_10069_10059_10058_418_10073_10017_10070_10060_10061_10052_10062_10053_10050_10051,searchweb201603_7&btsid=f266c527-3f40-49c1-844a-fb6f8f7b8c6b

 

[bendeman]

hello,

i dit not buy then on ebay. i got them from a store in the netherlands.
i wil test 1 batery when im back at the shop draw 1 amp and see what it does.
if it stays at 4v then the scooter is just to powerful and maby the previeous owner did someting to it.

is it a idee to get rid of some mosfets in the scooter controler?

thanks

 

[Sunder]

hello,

i dit not buy then on ebay. i got them from a store in the netherlands.
i wil test 1 batery when im back at the shop draw 1 amp and see what it does.
if it stays at 4v then the scooter is just to powerful and maby the previeous owner did someting to it.

is it a idee to get rid of some mosfets in the scooter controler?

thanks

Since you have a 13p battery, running it at 2amp would be the most realistic comparison.

Most people file the shunt rather than remove some of the mosfets to reduce power. I actually have no idea what removing a mosfet would do.

 

[cell_man]

You said the pack is 18S, but that is only 64.8V nominal. I'm guessing the LVC on that 72V scooter will be around 60V, or maybe even a bit higher. I could see the complete pack, possibly hitting 60V and tripping the LVC. You really need to be running a 20S pack on that bike, 18S is not enough. If a cell is 2C rated (cell rating from factory), they can sag quite a lot, even at 1C.

Connect a multi-meter to the battery supply leads and see what happens when you accelerate hard. You can also get current meters, that just have a clamp that goes around a conductor. If you had 1 of those, you could measure the current that your controller is really pulling. Better still, just buy a cycle analyst with the external shunt, they are very useful to have. Then you can see exactly what is going on with the battery, how many Ah you are using and even limit the current if you wish.

 

[izeman]

100% Positive, 5 Star feedback on 9800mah 18650s. Just a hint. When the best battery manufacturers in the world, Panasonic, Samsung, Sony, LG etc. Can't get 4000mah into a 18650 on $20 a pop cells, these no-name Chinese manufacturers must be working miracles to not only get nearly triple the best batteries on the market, but also do it at half the price and throw in a charger as well.

you missed one important thing: the printing on the battery says: EXPERT!! so this is a very special battery. :wink:
it has 3x the quantity of grade-a top brand cell. and NOONE seems to have measured the real capacity.
ppl that know a tiny little bit about this stuff would a) never order from those guys b) if they did request a FULL refund because of fraud.
btw: i DID order this stuff some years ago. so i guess everyone has to learn. now i order my batteries from paul em3ev or maddin.

 

[bendeman]

This has nothing tondo with the problem.

 

[izeman]

This has nothing tondo with the problem.

correct. more or less, but it proofs the old saying "you can't judge a book by it's cover" and i guess you already got all information you need?!
what else do you need?

.) measure
.) measure
.) measure

if measurement is correct:

.) get a decent battery
.) get a new controller
.) get a CA
.) teach your gf how to ride an inappropriately powered scooter

 

[bendeman]

Hello,

I put 1 amp load on 1 batery.
It drops from 4,2 tot 3,75

So how bad is it?
I think the cells arw not 2c eating as the say they are.
But still, they ar knew and only cost 2 dollar a pop. And they do have 2400mah

 

[danielrlee]

Your cells are clearly junk. You have three options:

1) Continue as you are with the existing problem.
2) Accept that they are junk and modify your controller to pull less current to keep your battery happy.
3) Accept that they are junk and build a new battery that can supply the current that you want.

There no way these cells are capable of supplying 2400mAh at 2C, or even 1C by the sound of things.

Do yourself a favour, take the cells back to where you bought them from and demand a refund.

 

[izeman]

I put 1 amp load on 1 batery.
It drops from 4,2 tot 3,75
So how bad is it?

i just tested a 25r cell @2.5A discharge (1C) and it sags from 4.09V to 4.06V. so judge by yourself ...
those cells are IN NOW WAY appropriate for ebike use. they may be ok for low power laptops or stuff, but not for high power applications. there are valueable sellers of high quality, geniune brand cells. but you will be in the +/- 4€ range per cell.

 

[Ykick]

Hello,

I put 1 amp load on 1 batery.
It drops from 4,2 tot 3,75

So how bad is it?
I think the cells arw not 2c eating as the say they are.
But still, they ar knew and only cost 2 dollar a pop. And they do have 2400mah

You have the information to calculate cell IR (internal resistance).

Subtract loaded voltage from resting voltage - 0.45V drop on 1A load applied = 450mOhm (milli-Ohm) which is very sad battery cell IR.

Good RC Lipo measures 4.5mOhm so those cells you’re working with are 100x worse in current handling (Amperes) performance.

Even Izeman’s “good” 18650 delivers only 12mOhm IR per cell.

I generally stop using RC Lipo cells when the IR creeps up over 20mOhm.

 

[bendeman]

Oke thanks for letting me know.
I wil contact the celler and mayby get some of the monny back.
But i dont think they will.

My scooter has a 2000w motor.
If i replace it with a 500w motor will it work then?
The scooter only has to go 30km a hour.
In the netherlands you can ride without helmet at 30km a hour.

Thanks

 

[Ykick]

Oke thanks for letting me know.
I wil contact the celler and mayby get some of the monny back.
But i dont think they will.

My scooter has a 2000w motor.
If i replace it with a 500w motor will it work then?
The scooter only has to go 30km a hour.
In the netherlands you can ride without helmet at 30km a hour.

Thanks

No, they ain't gonna power any motor, period. Maybe an LED flashlight but that's it. You got the old eBay battery cell swindle.

 

[danielrlee]

Oke thanks for letting me know.
I wil contact the celler and mayby get some of the monny back.
But i dont think they will.

My scooter has a 2000w motor.
If i replace it with a 500w motor will it work then?
The scooter only has to go 30km a hour.
In the netherlands you can ride without helmet at 30km a hour.

Thanks

No, changing the motor won't make any difference.

You can try modifying your existing controller to draw less current, or replace it with a new controller that will do the same. Both bad options of course, since the battery will still be rubbish.

 

[bendeman]

Photo of the pack i build. Sad to hear my cells suck.

 

[izeman]

these batteries are ok for powering the LIGHT of the scooter. nothing else.
EDIT: haha. i typed that while other posts came in. funny to see that others had the same suggestion 8)
they probably will be able to run a 500W motor more badly then well, but this pack IS JUNK. there is nowhere around.
you know the saying: putting lip stick on a pig?
your problem is the battery. not the motor, not the controller.
so my suggestion: the earlier you accept that you bought junk, burnt some money, the earlier you can buy a decent battery and really enjoy your scooter.
and i guess everyone here paid that money, some even more than once.

 

[bendeman]

Oke oke oke i know now haha.
Wel that was 500€.... shit.
Thanks for the responses

 

[izeman]

Photo of the pack i build. Sad to hear my cells suck.

as i said: you can't judge a book by it's cover.
you've done everything correctly. bought from a trustworthy seller, chose the correct pack size (more or less), but you simply were BETRAYED. simple as is.
ask the seller to proove that those cells are 2c cells. show them the voltage sag results. and don't let them show you a PAPER SAYING that those are 2c cells. you can't trust the writing on the battery as well (which btw was what i was saying in my, in your opinion, meaningless post :wink: )