# Can you help me high current charger basic?



## Genius Pooh (Dec 23, 2011)

hello

my dear friends..

I try to make quick charger for E bicycle.

I try to charge it as balanced method so I need 3.4v and over 100A..

But I don't know how to without transformer. 

I search Texas instrument web site..

Their IC is just support below 100v ..but Korea and Europe is 220 AC..

How can I transform 220 ac to 3.4v and over 100A ?

I need starting point Thanks


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## major (Apr 4, 2008)

Genius Pooh said:


> How can I transform 220 ac to 3.4v and over 100A ?


Get a battery charger or a power supply.

http://www.sorensen.com/products/XFR/XFR_Specifications.htm 

The model XFR 7.5-300 will get you 0 to 7.5 VDC and 0 to 300 Amps output from 220 VAC.


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## Genius Pooh (Dec 23, 2011)

major said:


> Get a battery charger or a power supply.
> 
> http://www.sorensen.com/products/XFR/XFR_Specifications.htm
> 
> The model XFR 7.5-300 will get you 0 to 7.5 VDC and 0 to 300 Amps output from 220 VAC.


Thank you major 

But I want to know about charger from basic 

Do you know about IGBT?

I think it's key source of it.

and why there is very small transitor looking one and very big box one?

Can you tell me difference of it?


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## Siwastaja (Aug 1, 2012)

Google for switch mode power supply design.

It will be a forward converter or some other switch mode PSU design. Mains rectification, driver (usually with MOSFETs, but IGBT's also a possibilty, no big difference), a transformer, rectification, and an inductor and capacitor for filtration. And a controller chip to adjust duty cycle of the transformer driver (feedback from both current sensor and output voltage measurement to get proper CC/CV charger action)

For usable efficiency (>60%) at voltage that low and current that high, it needs to have synchronous rectification in the output stage to avoid diode drop. This makes it a bit more complicated.

Nothing special in theory, but it's some serious design work to get it right.


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## Genius Pooh (Dec 23, 2011)

Siwastaja said:


> Google for switch mode power supply design.
> 
> It will be a forward converter or some other switch mode PSU design. Mains rectification, driver (usually with MOSFETs, but IGBT's also a possibilty, no big difference), a transformer, rectification, and an inductor and capacitor for filtration. And a controller chip to adjust duty cycle of the transformer driver (feedback from both current sensor and output voltage measurement to get proper CC/CV charger action)
> 
> ...


 
Wow Thank so much I must google it.. I breifly know about switching..


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## Genius Pooh (Dec 23, 2011)

I found this circuit on google..

I think what I try to do is very same as normal welder. ( Am I right?)

but in this circuit still have transformer - I know it can be smaller- 

so last coil must handle 100A so it must so big!! T_T 

What other method can solve size problem? 100A wire is too Thick for winding


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## Siwastaja (Aug 1, 2012)

That picture looks like a so called "forward converter" topology with "full-bridge" drive for the transformer. It's a typical one for higher power SMPS's. It does NOT have synchronous rectification, so, as such, it's only practical for higher output voltages, say more than 12-24V.

Again, Google gives you information on different topologies:
http://en.wikipedia.org/wiki/Switched-mode_power_supply
http://www.smps.us/topologies.html
http://ww1.microchip.com/downloads/en/AppNotes/01114A.pdf
http://ww1.microchip.com/downloads/en/AppNotes/01207B.pdf

But, in order to actually design it, you will need a lot of experience in electronics and knowledge in electronic design overall. 

However, you may be able to find DIY friendly instructions to build a PSU someone has designed, built and tested. Good luck.


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## PStechPaul (May 1, 2012)

I question why you need a 3.4V 100A supply for quick charging a battery for a bicycle. It is inefficient and tedious to charge several cells individually, and there are no motors that run on a single cell. If you do want to charge a single cell, you can find 5V 500W switching supplies for less than $100 that can be adjusted to 3.4V, but I think you really need more like 3.7V and you should have some series resistance or an active current limiter.

It would seem to be much better to keep the battery pack in series and use a full voltage charger with a BMS charge controller. You could probably adapt a welder but they are usually liited to 20-30 volts and they are designed for intermittent duty.

If you are using LiFePO4 cells, you should be able to get a professionally designed charger for about 1/10 the cost of the cells, and it would be an excellent asset to protect your investment.


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## Genius Pooh (Dec 23, 2011)

PStechPaul said:


> I question why you need a 3.4V 100A supply for quick charging a battery for a bicycle. It is inefficient and tedious to charge several cells individually, and there are no motors that run on a single cell. If you do want to charge a single cell, you can find 5V 500W switching supplies for less than $100 that can be adjusted to 3.4V, but I think you really need more like 3.7V and you should have some series resistance or an active current limiter.
> 
> It would seem to be much better to keep the battery pack in series and use a full voltage charger with a BMS charge controller. You could probably adapt a welder but they are usually liited to 20-30 volts and they are designed for intermittent duty.
> 
> If you are using LiFePO4 cells, you should be able to get a professionally designed charger for about 1/10 the cost of the cells, and it would be an excellent asset to protect your investment.


 
Thank you so much my friend 

I try to make my own charging system.. hohoh 

I preparing e-bicycle battery business 

very super quick charging one. It's so fun.. in Korea 24v 10ah battery pack is 300$ over.but I can sell nearly half price

as all we know It's cost just under 120$ 

hohoh This is what I try to do this business not make me rich but make my life funnier


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## Genius Pooh (Dec 23, 2011)

Siwastaja said:


> That picture looks like a so called "forward converter" topology with "full-bridge" drive for the transformer. It's a typical one for higher power SMPS's. It does NOT have synchronous rectification, so, as such, it's only practical for higher output voltages, say more than 12-24V.
> 
> Again, Google gives you information on different topologies:
> http://en.wikipedia.org/wiki/Switched-mode_power_supply
> ...


 
Wow thank you so much.. I print all your document  hohoho

yeah you are right  I must study it but after that I must ask other to design circuit for it hohoho Thanks


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## Hollie Maea (Dec 9, 2009)

The speed at which you can charge your batteries is limited by the C rate of the cells. It doesn't make any difference how big or how small the pack is.


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## Genius Pooh (Dec 23, 2011)

Hollie Maea said:


> The speed at which you can charge your batteries is limited by the C rate of the cells. It doesn't make any difference how big or how small the pack is.


 
yes sure but mostly every charger don't fulfill battery's full c-rate..

most charger are suck 

hohoho


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## PStechPaul (May 1, 2012)

As I understand it, higher charging rates shorten cycle life. And also the charge current needs to be tapered toward end of charge because of the internal resistance of the cells. If a cell has 5 mOhms resistance and you are charging at 100 amps, there will be an additional 0.5 volt, so if your charger is set at 3.8 volts it will turn off at an actual charge of 3.3 volts. You also need to measure the cell voltage right at the terminals, as even a few feet of #4 AWG cable will have one or two mOhms resistance and will affect the voltage by 0.1-0.2 volts, which is very significant. Battery charging is NOT trivial, and a simple charger that does not do a full charge, or worse, damages the battery and shortens cycle life, will not be well received by customers.


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## Hollie Maea (Dec 9, 2009)

Genius Pooh said:


> yes sure but mostly every charger don't fulfill battery's full c-rate..
> 
> most charger are suck
> 
> hohoho


Charge C rates are way lower than discharge. Charge your batteries faster than 2C (30 minute charge time) and find out what are suck. hohoho....


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## Genius Pooh (Dec 23, 2011)

PStechPaul said:


> As I understand it, higher charging rates shorten cycle life. And also the charge current needs to be tapered toward end of charge because of the internal resistance of the cells. If a cell has 5 mOhms resistance and you are charging at 100 amps, there will be an additional 0.5 volt, so if your charger is set at 3.8 volts it will turn off at an actual charge of 3.3 volts. You also need to measure the cell voltage right at the terminals, as even a few feet of #4 AWG cable will have one or two mOhms resistance and will affect the voltage by 0.1-0.2 volts, which is very significant. Battery charging is NOT trivial, and a simple charger that does not do a full charge, or worse, damages the battery and shortens cycle life, will not be well received by customers.


Oh great words thanks so much..

I must study hard about charging system and voltage..

Thanks


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## Genius Pooh (Dec 23, 2011)

Hollie Maea said:


> Charge C rates are way lower than discharge. Charge your batteries faster than 2C (30 minute charge time) and find out what are suck. hohoho....


 
Nice to meet you 

hohohoh

But headway's red battery's charging rate is 5-10c? I can't remember now


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## Siwastaja (Aug 1, 2012)

Genius Pooh said:


> hohohoh


https://www.youtube.com/watch?v=slnvTv1edmk


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## PStechPaul (May 1, 2012)

My dog's name is Muttley :
www.muttleydog.com


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## Genius Pooh (Dec 23, 2011)

Siwastaja said:


> https://www.youtube.com/watch?v=slnvTv1edmk


 
hahahhahahah so fun you make me laugh!! LOL hohoho


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