electric moped fault

[billyboya]

I think you paid approx. £90 for the liitokala, we said at the time it will be fake or poor cells used. It may be the cheap electronics used otherwise known as the bms, pay cheap pay twice.
My next battery build is a simple 12s 2p build with 21700 cells, 24 of them are £106 on there own and are one of the best cells avialable.

You maybe thinking when I had an electric bike which I sold now. As I also bought a lithium battery from same place

No I paid about £170 or near as for this battery. I will try to find out as it came from AliExpress site it’s only 9 months old but can’t see the seller doing anything about it.

Yes I knew it was about £170.

 

[Nealh]

Ok so it is a bit more pricier but still very cheap for 78 x 21700 cells, a bms , welding, shrink and wiring up. Not inc the postage £158 is dirt cheap.

 

[soundwave]

surprised it lasted that long tbh but when you buy things like this from china you have no idea what crap they have used it is just not worth the hassle.

jimmy is not cheap but you get what you pay cell wise for and warranty.

 

[billyboya]

Ok so it is a bit more pricier but still very cheap for 78 x 21700 cells, a bms , welding, shrink and wiring up. Not inc the postage £158 is dirt cheap.

When I get time I will remove the blue shrink wrap from battery and then get back here for help. But Im a bit busy with other things so I will let you know when it’s ready

 

[Nealh]

Just paid £119 for 24 x 21700 moli P42A and cell holders.

 

[Nealh]

Carefull opening the shrink if using any thing metal, one simply doesn't know if or what inulation has been used on the pack.

 

[billyboya]

Just paid £119 for 24 x 21700 moli P42A and cell holders.

Wow that’s good

 

[billyboya]

Carefull opening the shrink if using any thing metal, one simply doesn't know if or what inulation has been used on the pack.

Yeah I will as I expect wires there etc so will make a small cut 1st then use something plastic to lift away as I cut

 

[Nealh]

Only really one cell better then the P42A and that is Sam 50S if one can get them, they are 3X the price though but a 5000mah 25a cell.

 

[billyboya]

Only really one cell better then the P42A and that is Sam 50S if one can get them, they are 3X the price though but a 5000mah 25a cell.

Im a bit confused now about battery, as I was telling a friend about the battery wont charge up. and when I told him, its at 49.7V he said its because its full thats why, as its a 48v battery and you say its now at 49.7 well its over 48v then. so can you explain why it has to say 54.6v or 54v to make it full. is the battery bad then. he said you have a moped which needs 48V to run it well he said then you ok. try running battery down a bit.

But I cant explain to him, that it has to be 54.6v I think to run the motor. so can you explain things .

 

[Nealh]

Your friend knows bugger all about lithium batteries and like wise you yourself haven't grasped the knowledge of the cell technology.
It's a good job you didn't turn to your friend originally when your bike didn't work.

A lithium cell is 3.6/3.7v nominal voltage, this is its 50% rating. It will charge to a max of 4.2v.
It generally has a voltage range of 3.2v - 4.2v for practical capacity usage and life cycle.

Your battery is 48v nominal, it has 13 cells in series or 13s. 13 x 3.7 = a tad over 48v.
At full charge 13 x 4.2 = 54.6v, the max charge can very depending on the bms balance spec's. Some bms stop charge and balance at a lowere voltage so 4.15v per cell or nearly 54v max charge.

Simpy put if you battery doesn't achieve a charge between 54v - 54.6v then it is either knackered or the bms is at fault. One should periodically check the charger output to ensure it is correct.

 

[Nealh]

Your motor will work as long as it sees approx. 43v - 54.6v, though at the lower voltage the controller may cut power due to low voltage or voltage sag.
The motor will run with a 36v battery if the controller was 36v rated as well, but at a much slower speed.

 

[billyboya]

Your friend knows bugger all about lithium batteries and like wise you yourself haven't grasped the knowledge of the cell technology.
A lithium cell is 3.6/3.7 nominal voltage, this is its 50% rating. It will charge to a max of 4.2v.
It generally has a voltage range of 3.2v - 4.2v for capacity and life cycle.

Your battery is 48v nominal, it has 13 cells in series or 13s. 13 x 3.7 = a tad over 48v.
At full charge 13 x 4.2 = 54.6v, the max charge can very depending on the bms balance spec's. Some bms stop charge and balance at a lowere voltage so 4.15v per cell or nearly 54v max charge.

Simpy put if you battery doesn't achieve a charge between 54v - 54.6v then it is either knackered or the bms is at fault. One should periodically check the charger output to ensure it is correct.

Hi I would rather trust you than this friend, and yes he dont know bugger all. he thinks he does. But I just wanted to know more on these batteries. Im not very good myself at all this. But Im taking notice of you not my friend. its no good me trying to explain to him either. as he has never had a electric bike or experience with lithium batteries like yourself. its fine I will go ahead soon and check my battery.

You have been 100% helping me so far so I think I trust you more than this friend. I even said to him on old charger green light never came on until it got to 53.9v or 54V so your are right

 

[Nealh]

Until you cut the shrinkwrap and expose the BMS muliti wire connector there is liitle you can do.
A 24v /7s lithium battery charges to 29.4v max.
28v/8s to 33.6v max.
32v/9s to 37.8v max.
36v/10s to 42v max.
40v/11s to 46.2v max.
44v/12s to 50.4max.
48v/13s to 54.6max.
52v/14s to 58.8v max.
56v/15s to 63v max.
For every extra cell added in series the max charge increases by 4.2v.

 

[billyboya]

Until you cut the shrinkwrap and expose the BMS muliti wire connector there is liitle you can do.
A 24v /7s lithium battery charges to 29.4v max.
28v/8s to 33.6v max.
32v/9s to 37.8v max.
36v/10s to 42v max.
40v/11s to 46.2v max.
44v/12s to 50.4max.
48v/13s to 54.6max.
52v/14s to 58.8v max.
56v/15s to 63v max.
For every extra cell added in series the max charge increases by 4.2v.

Well I never knew all this, But I suppose if you have been doing this for a good while you should know much more than my friend. I never took much notice of him really anyway, as he thinks he knows but he don't I know more than him. But let him think he is better LOL.

I'm hoping it will just be a new BMS like you say about £15 to £25 But if its like cells or duff ones I wont be replacing those as not experienced enough for that Plus not spending Loads more on moped. so fingers crossed its the BMS

I wont be looking at inside battery just yet as got other stuff to do, But soon as I have I will let you know.

And I know I have said this many times, But I really do appreciate all your help. its been a long journey But I have just about rebuilt this Moped. But its too heavy for me. if I ever broke down miles away. Plus that time, when cable twisted and broke. well then of course the Phase wires to motor was touching so made moped feel like brakes was sticking as I found out that's how you test phase wires. by touching 2 together. soon as you release then wheel turns ok. so you can imagine how hard it was to push home when that happened. But I was lucky again then as was just a short way from home.

 

[billyboya]

Ok I have now managed to cut off top of battery the shrinkwrap. and its encased in a plastic box it seems I do believe this is the BMS arrowed is there any way I can lift that out with out sparking anything. I think I can but just need to know if you can say disable the battery while doing this



OK Ive managed to get to view the BMS

 

[soundwave]

you need to disconnect the balance cable and use a meter to test the cell bank voltages.

dont short the probes.

 

[billyboya]

you need to disconnect the balance cable and use a meter to test the cell bank voltages.

dont short the probes.

Well I won’t have a clue where the balance cable is. And about testing cell bank voltages I did do one on the original battery. But can’t remember how I did it now. But can’t remember disconnecting any cables. I know it’s very hard to check all the pins as so close together. And meter probes seem too thick You need a thin needle probe

 

[soundwave]

the white connector at the top of the bms is the balance/ sense cable you just need to unplug it and test every cell bank one buy one like in the video.

if one or more cell banks show lower voltage that's your problem and why it wont fully charge but it could be just a broken spot weld to that bank of cells so check all of those and make sure every cell is connected on the spot welds

 

[Nealh]

Pull out the White jst connector ( with the Yellow/Red and single Black wire).
You will need two needles/pins or some pcb strip pins.
Place one needle in the Black wire pin location and the other in the Yellow next to it, set your meter to 20v and write down the voltage as #1. (Black probe on Black and Red probe on Yel).
For #2 simply move the needle from Black pin to the first Red one and take a reading. (Black probe on Yel and Red probe on Red)
For #3 the needle in Yel moves to the next Yel for a reading ( the Balck probe always on the first needle as yuo move along and the Red probe always on the second needle).
For #4 the needle in the Red moves to the next Red and one takes a readiing, alternate the pin each time along the line until you have done so thirteen time to get thirteen individual voltage readings.
Once done post the results for us to see.

If you don't like the fact the needles are close together, take the readings as accumaltive ones and write them down (set the meter to 200v).
Once you have done the first cell reading as above, leave the needle in the Black pin out location all the time and only move the second needle along one pin at a time.
You will see readings like 3.8, 7.6, 11.4, 15.2 etc, etc until you have thirteen with the last being approx. 49.7.

Once we can see the results we can see if their is a balance issue or whether the non charging may simply be a bms issue.