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**RS_** · 06-11-2013, 09:26 AM

change the 2 47ohm resistors with 100K

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**Joster** · 06-11-2013, 09:57 AM

Great! Ask and you shall receive! I will let you know how I make out with it.

Would you recommend I build this type instead of the timing design?

**Joster** · 06-11-2013, 10:00 AM

Also, would the type, capacitance and voltage rating be of C1?

**RS_** · 06-11-2013, 12:51 PM

Originally posted by Joster View Post

Also, would the type, capacitance and voltage rating be of C1?

you need Low ESR fast discharge Caps

The Value depends on the size of energizer feeding it, and the size of battery you are charging.......
voltage rating is 35 to 50 V depending on the voltage of the charging bank.......

I like this version, Because it is self adjusting, it always fires at the same voltage on the capture cap, no matter if things change like the primary runs down, etc... the timing changes..... where a timer will fire in the same time period no matter what, but the voltage on the cap is different as things change......

Also, the above Sch was designed by JB for a 36V system, and will run a 24V system too, but will need some minor tweaking to run a 12V or smaller V system

**Joster** · 06-13-2013, 04:28 AM

Quick Check

Thanks again for the schematic. It is greatly appreciated! I have re drawn it in multisim and placed the values as best I can. Some of them were a bit blurry but I think I got everything. Just not sure if those are 1.5V or 15V Zener's. I have attached the redrawn circuit here. If you could take a quick look over the values that would be awesome!

Would the size of energizer be determined by the number of devices running? Right now, I have an 8 filar coil running 4 MJL211's (one of them is faulty). I assume the size of battery would be the Ah rating and that I could but 3 of my 12V B.B. Battery BP7.2-12's in series for a 36V bank.

In regards to finding the right capture cap,

a) Would I be looking for a 50V max voltage with a 36V system?
b) Is there a ratio to go by, say 5000mF/MJL211?
c) I have looked up a few caps and checked the ESR ratings. Is 11mOhms @120Hz considered a low ESR rating?
d) I could reduce the ESR with more caps in parallel correct?
e) The max DC surge rating on most of the caps I have looked at are only about 12Vdc. Would it not need to handle much higher pulses ?

I have also attached some pictures of my machine so far.

Thanks again, your help is greatly appreciated.

J.

Attached Files

**RS_** · 06-13-2013, 09:31 AM

Joster,

I have the full wave bridge diodes pointing in the wrong direction, even though i have it Labeled + and - on the sch, my bad, i have done this on several sch's, and was a copy paste mistake that i had not noticed for a good while, until some one pointed it out recently.

So change the diode direction on the full wave bridge, and your sim should work correctly......

the Zener reference on the comparator is 5V, the other ones are 15V

If Tom C. or John K. could post a link for their source for caps it would be great......

a) Would I be looking for a 50V max voltage with a 36V system? 50 to 75V will work for 36V
b) Is there a ratio to go by, say 5000mF/MJL211? not that i can figure, but there is a relationship....
c) I have looked up a few caps and checked the ESR ratings. Is 11mOhms @120Hz considered a low ESR rating?
d) I could reduce the ESR with more caps in parallel correct? this can help depending on what caps and values you have
e) The max DC surge rating on most of the caps I have looked at are only about 12Vdc. Would it not need to handle much higher pulses ? DC surge is a amp rating......

"Would the size of energizer be determined by the number of devices running?" yes

nice looking unit..... you want to build up a solid soldered and with solid battery connections with heavy wire unit, as soon as you feel you understand the circuit, and get rid of the alligator clips and proto board

**RS_** · 06-13-2013, 11:16 AM

Originally posted by BroMikey

RS I have a question about comparator dumps like you are working on.

Okay My mistake I see that each comparator is built for each battery bank.

#1 when the battery is dead at 12volts does the comparator start the charging pulse at 20volts? And at 14volts does it send 28volt pulses later on in the charging cycle?

Mike

No, for 12V, you want to be at about 25 to 28V to start, and then the comparator will adjust some what on how far it discharges the cap as the battery charges, and will change it's pulse timing to match that charging, while maintaining it's max Voltage setting......

**RS_** · 06-13-2013, 02:59 PM

Mikey, Mikey, Mikey,

You try to make this too hard....

the 3 major variables are the energizer's output, the capture cap value, and the size and kind of charging battery or bank of battery's,(parallel or series)

some battery's or banks (12Vin this case) like 23V pulses, at some period between discharge time with a given value cap, some like 30V pulses at some period between discharge time with a given value cap.... most are going to like about 25 to 28 volts with about 1 to 3 pulses per sec, with what ever cap value makes that happen with your energizer's output...........

balance these out, and you have a nice system. Experiment.....!!!!!!! each setup will be different.......!!!!!!!!!

JB, nor any one else, can only give you a ball park circuit, and list of parts, and size of battery's, etc, etc, etc...... It is up to you to build it and tune it to your set of parts, battery's, circumstances, etc, etc, etc.......

**Joster** · 06-13-2013, 07:53 PM

Thanks for the info. I figure something like this would be good...

SB300 BusBoard Prototype Systems | Mouser

I'll be ordering the parts for the comparator dump circuit this weekend. Looking forward to it.

Once I have it working I figure I can expect a great improvement in charging. So much so that the charge battery will charge faster than the run battery depletes. Provided I'm running batteries that are in good shape.

Does this sound right?

**John_Koorn** · 06-13-2013, 10:37 PM

Hi Joster,

If you are going to use that board I highly recommend that you use thick wires to the dump capacitor and from the dump capacitor to the MOSFET, as well as thick wires to the charge battery. There are very high current pulses in these parts of the circuit and you want to minimize the losses.

Don't just use the skinny traces on the proto board.

John K.

**osuri7** · 06-15-2013, 09:59 PM

Originally posted by John_Koorn View Post

Hi Joster,

If you are going to use that board I highly recommend that you use thick wires to the dump capacitor and from the dump capacitor to the MOSFET, as well as thick wires to the charge battery. There are very high current pulses in these parts of the circuit and you want to minimize the losses.

Don't just use the skinny traces on the proto board.

John K.

Hi John K.,

Regarding optimal connections with the MOSFETS here: I usually make the boards myself (photo etching) and then pin and solder the components on. I am working on my first MOSFET cap-dump circuit now (the same that is in the intermediate handbook from JB, Aaron and Peter). The only way I can think of to minimize impedance in the cap output lines (drain and source lines) is to make the traces on the board nice and wide (5 - 6 mm), then solder a nice thick piece of copper wire (3 - 4 mm diameter) directly on the traces making sure the ends of the copper wires are cozy with the MOSFET leads when all is said and done. Any comments?

Thanks for any help in advance.

Chris M.

**John_Koorn** · 06-16-2013, 02:32 PM

Perfect Chris

John K.

**jason mcgrath** · 10-13-2013, 06:43 PM

Can any body tell me where i can get a circuit design to make the cap dump?

**Tom C** · 10-13-2013, 07:40 PM

did u read this thread? Tom C

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Cap Dump using Comparator

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