DIY build my own E-bike battery - tips?

[harryS]

if it shorts like this - does the battery simple fail to run? and fail to charge?

There is a test standard that says a cell must not start a fire if you short circuit it. Quality cells have pressure sensitive circuit breakers inside that are intended to break the circuit. They also have vents that blow if the pressure gets too high. The same standard says you can overcharge a cell and it must not start a fire. But ... the unexpected happens in real life.

Nonetheless, we battery hobbyists should use the washers, They cost like a penny. All of my commercial ebike batteries use them. When you pay someone $8K a year in China to spot weld batteries by hand, they're going to miss a few welds in a day,

 

[Gionnirocket]

When you pay someone $8K a year in China to spot weld batteries by hand, they're going to miss a few welds in a day,

That's why a good line manager keeps a stiff rod handy for knuckle raps and to maintain quality control.

 

[Emsflea]

That's why a good line manager keeps a stiff rod handy for knuckle wraps and to maintain quality control.
View attachment 198783

I agree beat them harder.

 

[Slaphappygamer]

I agree beat them harder.

Morale shall improve!

 

[PCeBiker]

You guys have me feeling inspired to connect my 6 amp car battery charger up to my battery pack and see if it will take a full charge?

It is a 4S4P cell pack, so I shouldn't get any overcharged cells at a ~13.8 VDC input with no BMS.

I better use my 3A charger that's regulated to 13.8VDC?,..
The 6 amp charger puts over 16VDC with no load. It ain't regulated.

 

[Slaphappygamer]

But could the cells handle charging at 8A? And what is the charge port rated at?

Common 5.5*2.1 ports have a 5A max charge rating.

YOLO

 

[PCeBiker]

But could the cells handle charging at 8A?

Naa,.. the cells are shot.
They won't pull 8 amps unless I crank the voltage up to like Fiddy Volts.

And what is the charge port rated at?

Enough to start a car if the engine is already warmed up.

 

[Chazmo]

But could the cells handle charging at 8A?

Depends how hard knuckles were rapped during assembly. Spare the rod, spoil the battery.

 

[PCeBiker]

View attachment 198783

 

[Gionnirocket]

You guys have me feeling inspired to connect my 6 amp car battery charger up to my battery pack and see if it will take a full charge?

It is a 4S4P cell pack, so I shouldn't get any overcharged cells at a ~13.8 VDC input with no BMS.

I better use my 3A charger that's regulated to 13.8VDC?,..
The 6 amp charger puts over 16VDC with no load. It ain't regulated.

View attachment 198786View attachment 198787

Obviously you did not read the cautions on the back panel!

 

[Slaphappygamer]

Obviously you did not read the cautions on the back panel!

See what happens when you don’t use hands.

 

[PCeBiker]

See what happens

I found the soldered bolt lugs and checked the voltage,..

I'm getting 3¾ volts on the pack,

Then I plugged in my charger.
It did draw almost 4 amps when I plugged it in,..

The pack charged to 13.13 Vdc when it ominously shut down.
Voltage stuck.
No more current flow.

I put it on the bench charger and cranked it up to 60 Volts, but still no current flow??

But I'm still reading about 13VDC as an output voltage ??

I assume that a popped a fuse, but shouldn't I read 0 Volts if I have an open circuit ??

I don’t know what's going on??

 

[Gionnirocket]

Typically if it stops charging it's best to submerge it in gasoline for a few hours

 

[PCeBiker]

Typically if it stops charging it's best to submerge it in gasoline for a few hours

I've got gasoline, propane, MAP gas, and double boiled linseed oil that burns up real nice,..

That aughta get that damn battery going.

 

[6zfshdb]

I found the soldered bolt lugs and checked the voltage,..

View attachment 198794

I'm getting 3¾ volts on the pack,

View attachment 198795

Then I plugged in my charger.
It did draw almost 4 amps when I plugged it in,..

View attachment 198796


The pack charged to 13.13 Vdc when it ominously shut down.
Voltage stuck.
No more current flow.

View attachment 198797

I put it on the bench charger and cranked it up to 60 Volts, but still no current flow??


View attachment 198798

But I'm still reading about 13VDC as an output voltage ??

I assume that a popped a fuse, but shouldn't I read 0 Volts if I have an open circuit ??

I don’t know what's going on??

I hope that's a fireproof carpet.

 

[harryS]

I put it on the bench charger and cranked it up to 60 Volts, but still no current flow??

Looks like a 4S-4P. Should hit 16.8V if the cells were good, Stuck at 13V. You might have all four groups at 3.5V, or more likely, some at 4V and the others at 2V, ANyway, for the time being, neither the car charger or the bench supply can force enough current to go much higher.

No worries. If you leave them connected long enough, I am sure the cell chemistry will slowly absorb energy, go higher in voltage and get hotter, Should catch on fire eventually if that's what you wanted. Maybe vent if their safeties still work,

 

[PCeBiker]

,.. Should catch on fire eventually if that's what you wanted.

Lol.

I was just curious and wanted to see if it would take a charge.
The whole experiment lasted less than 5 minutes.
I was right there watching the whole time. I'm sure that I would have seen, heard or smelt something if it was ready to pop ?

I finished the experiment by shorting out the positive and negative terminals.
No spark, no pop, no smoke, nothing, except the voltage dropped to 0.

The cells were probably already dead when I put the pack on the shelf over 10 years ago.