# Cheapest charger on forum



## TEV (Nov 25, 2011)

Those chargers are named "Bad Boy"


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## cts_casemod (Aug 23, 2012)

TEV said:


> Those chargers are named "Bad Boy"


I am getting into your idea about the faster charger lol. 
It has been quite reliable, I keep a close supervision to make sure the voltages are okay and there is a 175V zenner set up in a way to burn the fuse if I fall asleep and the voltage goes past 175V.

Hopefully this will be the next thing to automate with current reduction and auto shutdown at a given voltage. I should soon have an amp meter on my batteries for supervision, since the charger is built in.


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## PStechPaul (May 1, 2012)

You could use the voltage relay that I designed and described in another thread. Here is the schematic. I can supply PIC source code and BOM upon request. I will be making the PCB soon and you are welcome to use the Gerber files or I could send you a board and a kit of parts but you can build it on a small perf board as I did for the prototype.


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## cts_casemod (Aug 23, 2012)

PStechPaul said:


> You could use the voltage relay that I designed and described in another thread. Here is the schematic. I can supply PIC source code and BOM upon request. I will be making the PCB soon and you are welcome to use the Gerber files or I could send you a board and a kit of parts but you can build it on a small perf board as I did for the prototype.


Thanks Paul,

I did something similar using analogue electronics with some old parts I had arround.

The charger output power was doubled to 800Watt (5Amps @ 160V) and I have added a 250Watt low charge setting to charge overnight. With the fast charge I can now charge a dead battery in 4 hours, usually it takes half.

I use a Class V efficiency power supply from a netbook modified to output 12V to power the electronics from the battery. Its a bit overkill but smaller adaptors would use twice as much energy due to low efficiency, providing power for the voltmeter, ampmeter and energy logger I will install. Just this circuit draws 9mA from the pack, I expect, with the remaining instruments, to use about 20mA. They can be disabled, but the idea is to be on at all times.






































The circuit is based on a LM393 dual comparator. First comparator reads battery voltages and disables the charger relay once the pack reaches 165V. The charge is resumed if the battery goes below 161V. This can be changed with one resistor for batteries that have a higher voltage sag.

Second comparator is an alarm, set to 167V in case someting fails.
A 0.1R resistor limits AC inrush current from the capacitors to avoid burning the relay contacts. At 5Amps dissipates 2.5Watt.

A 10 to 100Ohm resistor acts as a protection between HV and LV grounds needed to be able to power the circuit from a low source PS.

The optocouplers were used as I did not had any PNP transitors at hand.

So now I just set charge rate (Fast or slow) and wait for the charge to complete.


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## PStechPaul (May 1, 2012)

Looks pretty good. Another idea may be to use some zeners in series with the input of a $0.50 opto-triac, so the circuit will draw essentially zero current until the zeners conduct, and then 3 mA will be enough to trigger the triac and turn off the charger. You would have to add hysteresis so the charger won't cycle off and on, but this can be done with a latch circuit on the AC side, so you need to push a button to latch ON and then the monitor turns it off when charging is complete. 

Cost of this system, about $5.


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## DDDvvv (Apr 2, 2012)

About the 500w server power supply, I thought about replacing the voltage divider and current limit resistors with a pair of digital pots, and then controlling them with a microcontroller.

That is, if you can code a micro, and tolerate the 256 positions on the digital pots.


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## Siwastaja (Aug 1, 2012)

DDDvvv said:


> About the 500w server power supply, I thought about replacing the voltage divider and current limit resistors with a pair of digital pots, and then controlling them with a microcontroller.
> 
> That is, if you can code a micro, and tolerate the 256 positions on the digital pots.


If you are able to do that, you could be able to salvage the transformer and power stage and just do the SMPS control by yourself. It's just measuring the voltage and current and adjusting PWM duty cycle to get where you want to in a simple PI loop. So The Real Thing may be easier than the kludge to control the PWM controller chip.


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## cts_casemod (Aug 23, 2012)

PStechPaul said:


> Looks pretty good. Another idea may be to use some zeners in series with the input of a $0.50 opto-triac, so the circuit will draw essentially zero current until the zeners conduct, and then 3 mA will be enough to trigger the triac and turn off the charger. You would have to add hysteresis so the charger won't cycle off and on, but this can be done with a latch circuit on the AC side, so you need to push a button to latch ON and then the monitor turns it off when charging is complete.
> 
> Cost of this system, about $5.


I was going to do that initially, but with a self powered relay. Once the contact was opened the power for the coil would be removed as well. A button would be used to initially close the relay, say a 230V coil. I guess the optotriac could be used to short the coil at a preset voltage.




DDDvvv said:


> About the 500w server power supply, I thought about replacing the voltage divider and current limit resistors with a pair of digital pots, and then controlling them with a microcontroller.
> 
> That is, if you can code a micro, and tolerate the 256 positions on the digital pots.


Not quite. What I would do was set the value manually (voltage divider) to whatever maximum battery voltage I wanted to and the micro, would only change the values in order to reduce the charge current, so as to act as a fail safe. I would use a PWM output. I think a digital POT is a bit overkill.

Its similar idea to what other member is using in the non isolated charger, i just have a different way of implementing it to have both pfc and higher efficiency. And of course, smaller capacity. His charger may be a great deal for those looking at a 10KW charger but if you only have 3KW available is not a good deal at all, which is a shame.

By the way the server power supply way is dead. I will resume that project at a later stage using a buck PFC controller instead.



Siwastaja said:


> If you are able to do that, you could be able to salvage the transformer and power stage and just do the SMPS control by yourself. It's just measuring the voltage and current and adjusting PWM duty cycle to get where you want to in a simple PI loop. So The Real Thing may be easier than the kludge to control the PWM controller chip.


No transformer. Just a buck (step down) converter using a PFC corrected IC that would be controlled with dedicated analog electronics or a micro to operate in a CC-CV way. I will start this from scratch at a later time. A suitable inductor would also be required.


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## KUSAW (Jul 1, 2011)

Hi,

Is it possible to upgrade output current capabilities? Such as 50A?
Thank you.....

jakarta
Indonesia


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## EVfun (Mar 14, 2010)

TEV said:


> Those chargers are named "Bad Boy"


A "bad boy" is just a bridge rectifier and extension cords to limit current. What *cts* referred to is known (amongst the ancient EVers) as an "*ugly box*" charger. I think John "PlasmaBoy" Wayland gave it that name (google "Plasma Boy's story" to learn how he got his name.)


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## jackbauer (Jan 12, 2008)

I did some experiments with the cap charger a few years back including 3 phase input and control via ssr. The best method to make it programmable is one of there :
http://www.lightobject.com/Programm...th-dual-control-Good-for-HHO-System-P407.aspx

The two control relays can be setup to switch solid states. One drops the current to the termination current and the other kills power once the cv voltage is reached the second time.


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## cts_casemod (Aug 23, 2012)

KUSAW said:


> Hi,
> 
> Is it possible to upgrade output current capabilities? Such as 50A?
> Thank you.....
> ...


I doubt either type will be suitable for what you want.

The capacitive charger is not suited for anything above 5-10Amps RMS.

The PFC charger can be made for those power levels, but I assume you know the theory behind PFC boost converters. 
The typical output voltage is 380-415V. Is this suitable for you?

If not you may want to have a look at the 12KW open source charger


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## alvin (Jul 26, 2008)

jackbauer said:


> I did some experiments with the cap charger a few years back including 3 phase input and control via ssr. The best method to make it programmable is one of there :
> http://www.lightobject.com/Programm...th-dual-control-Good-for-HHO-System-P407.aspx
> 
> The two control relays can be setup to switch solid states. One drops the current to the termination current and the other kills power once the cv voltage is reached the second time.


I watched your videos about that. Do you still use it to charge?

Alvin


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## cts_casemod (Aug 23, 2012)

jackbauer said:


> I did some experiments with the cap charger a few years back including 3 phase input and control via ssr. The best method to make it programmable is one of there :
> http://www.lightobject.com/Programm...th-dual-control-Good-for-HHO-System-P407.aspx
> 
> The two control relays can be setup to switch solid states. One drops the current to the termination current and the other kills power once the cv voltage is reached the second time.



ALWAYS USE A CONTACTOR and a good quality one.
The inductive load is enough to weld the contacts of a small relay or damage a SS switch and if this happens the charge wont stop until something burns out.

Also for someone trying this a fuse BEFORE and another one AFTER the bridge rectifier is mandatory.

Using the right inductor or a mixture of inductor/capacitors will reduce the peaks substantially


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