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Charging Battery from 50V 5A Transformer.

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SalmanR1

New Member










Noob here!
hi, I wanted to charge my E-bike batteries from a 50V 5 amp transformer.
12S6p (48v, 12ah) = 12 batteries in Series, 6 in every pack.

Transformer specs
50 to 60 Hz
Input: 200 to 230v
Output : 6v , 55v , 65v , 85V
resistance : I don't know!
Nothing else I know about it ,

I do have a 6s charger but dismantling battery every time kills me.
I got this made on order, to charge my 50v battery on my Ebike, but whenever I connect it to the battery the amp Draw is 12A and the diodes are instantly hot as well as the Transformer.

I have not installed any capacitor in it, which I will tomorrow, Just want to know what wrong I am doing here. can I limit the current draw here?





 
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MikeMl

Well-Known Member
Most Helpful Member
What chemistry are the EBike batteries? With most modern batteries, you need an electronic charger circuit whose design is specific to the battery type.
 

SalmanR1

New Member
Lithium Phosphate (lipo)
you right about chargers, they require specific chargers,
I just want to try this method, which is used by few, while administered charging is used,
 

Musicmanager

Active Member
Hi Salman

I'm a long way from being an expert, but I do want to express a big caution ... ...

1. A little googling suggests your batteries might be Lithium, which I think requires a particular charging system to be safe

2. The spec of your Transformer would suggest the output is AC not DC which your batteries require and this might explain why the diodes are getting over hot.


I may be completely wrong , often am, but until someone who knows better jumps in and gives some good advice, please be careful because I think what your doing at best, will damage your batteries; at worst, will cause an explosion !


S
 

SalmanR1

New Member
Hi Salman

I'm a long way from being an expert, but I do want to express a big caution ... ...

1. A little googling suggests your batteries might be Lithium, which I think requires a particular charging system to be safe

2. The spec of your Transformer would suggest the output is AC not DC which your batteries require and this might explain why the diodes are getting over hot.


I may be completely wrong , often am, but until someone who knows better jumps in and gives some good advice, please be careful because I think what your doing at best, will damage your batteries; at worst, will cause an explosion !


S
Thank you for your reply,

as the voltages are under safe zone I can charge them this way. under my supervision.
that's what I think, as the Transformer is 5a, and the diodes are 6a why the drain is of 12a?
 

Musicmanager

Active Member
OK .. ..

So you have a bridge rectifier connected to the transformer .. ..

What are the diodes 1N ????? and which output are you connected to ?
 

audioguru

Well-Known Member
Most Helpful Member
Your circuit is not a proper battery charger. Its current is infinite because nothing limits the current except the overloaded transformer and diodes. Also there is nothing to detect a full charge so the battery might be charging so long that it boils, explodes or it catches on fire. A Lithium battery must be charged with a balanced charger that has a separate wire to detect and control the voltage and current of each cell.

You said your battery has 12 cells in series and it is lithium then its fully charged voltage must not be higher than 12 x 4.2V= 50.4V so you are lucky that the battery did not explode (yet). It is very difficult to extinguish a lithium fire because water will make its white-hot flame burn hotter.

Each of the 6 battery packs must be charged separately and it is too bad that the bike manufacturer did not make a charger that charges all packs at the same time.
 

tcmtech

Banned
Most Helpful Member
Given the type of cells you have you need to add a cell voltage balancer circuit system between each cell set to keep its individual charging voltage under ~ 4.1 - 4.25 volts peak which would mean you would need the transformer to put out at most ~ 49 - 52 volts at whatever current limit it or the battery packs are rated to handle.

To do that you would need the AC output to be between ~36 - 37 volts AC at whatever taper charge point current the battery sets need.

The closest configuration you will get with your transformer in stock setup to that voltage would be to pull the secondary power off the 55 and 85 volt taps while having your 240 VAC input running to the 200 VAc input. Not perfect but that's as close as that transformer will get to doing what you want with some degree of safety and control and even then I would be very hesitant to use it indoors unsupervised and without a way to get the battery pack outside in a hurry if it decided to go up on flames.

Personally I would just spend the money and buy a proper charging system for the battery even if it requires having to have two or three lower voltage charges running in series each handling only a few cells of the whole setup.
 

SalmanR1

New Member
I have used 230v input on the transformer and connected it to the 210Vac, that's how the volt output from the transformer dropped to 48~49V.

How can I restrict the Current now. to 4 amps??

Diodes are 6A10 MIC.
 

audioguru

Well-Known Member
Most Helpful Member
I think this thread should be closed because you are tying to charge an extremely dangerous lithium battery that needs a safe complicated balanced charger with a simple charger that was used for an old lead-acid car battery.
 

audioguru

Well-Known Member
Most Helpful Member
An overloaded transformer makes a poor current limiter and maybe will catch on fire.
 

Colin

Active Member
You can try a 12v 100w car headlamp in series with the rectifier and see what current flows. But how will you know when the battery is charged??????
 

Colin

Active Member
How could the transformer be made especially for you when the output voltages are completely incorrect ?????
 

Colin

Active Member
The simplest thing to do is take the insulation off and unwind the 65v to 85v winding and then the 55v to 65v winding and then start to unwind some of the 65v winding.
During this time, work out the turns per volt.
 

crutschow

Well-Known Member
Most Helpful Member
I trust your health, death benefit, and fire insurance is up to date if you insist on continuing with this extremely dangerous experiment. :eek:
This is what happens when the small battery in an e-cigarette explodes.
Imagine what will happen when your large array of batteries does the same.
 
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