Fechter's Mini Meanwell Limiter V.3

[fechter]

You may be the first to try on one of these. Supplies with linear current limiting will have hefty shunts somewhere on the board. Hiccup only versions don't have the output side shunts.

I'm sure the limiter board will work if you can find the right OVP spot.

[Degull]

Just assembled one of Fechter's V3 boards and it was a piece of cake. You have to read Fechter's instructions and follow the pics. He has taken the time to make this easy for all. It was a straight forward and logical build, perfect for a newbie like me! There are about 20 boards left, get them while you can!

[nicobie]

I just put my board together and like Degull said, "it was a piece of cake" The directions are clear and easy to follow.

I think I'm going to buy another to control 2 - 36V power supplies in series. Do you pick the proper current resistor by total voltage of the 2 supplies or the voltage of just one of the supplies?

Thanks for making these boards available again.

Nick

[JohnC]

Received today in Florida-Thanks

[999zip999]

JohnC Good to hear your son has an interest.

[fechter]

I just put my board together and like Degull said, "it was a piece of cake" The directions are clear and easy to follow.

I think I'm going to buy another to control 2 - 36V power supplies in series. Do you pick the proper current resistor by total voltage of the 2 supplies or the voltage of just one of the supplies?

Thanks for making these boards available again.

Nick

With two supplies in series, the current will be the same in both. The board should only be installed on one supply, so pick the zener (or jumper) to match the supply it's used on.

[hjns]

I want one. I sent Degull some money. Hope that there is still one left?

[fechter]

Don't worry. If he runs out, we can do another batch.

[hjns]

Don't worry. If he runs out, we can do another batch.

Cool! Thanks!

[Degull]

I want one. I sent Degull some money. Hope that there is still one left?

Still have about 20 boards left.

You sent me the payment but there is no address in the PayPal invoice! Let me know your address as soon as possible and I will get one in the mail to you. Thanks.

[Andje]

Just making sure, but for a 168v Meanwell setup, you would need a 135v zener to drop it down to under 35v?

[fechter]

Just making sure, but for a 168v Meanwell setup, you would need a 135v zener to drop it down to under 35v?

168V?

I don't think they make one that goes that high do they?

If you are planning to put several supplies in series to make 168V, then the zener should be sized for the single supply that it will be attached to. For more than 3 supplies in series, you may need to put limiter boards on more than one supply. One limiter for every two supplies in series should give enough compliance range to avoid problems.

If they DO make a supply that goes that high, the zener will need to dissipate quite a bit of heat, so 1W may not be enough.

Let me know your configuration.

[Andje]

Ok, I see, I was certainly confused. I will be using 48v MW in series, so I only need that size zener, I see. I have two boards coming, and will end up using 3-4 mw, so if I need two for the 4 in series I am covered. Thanks Fechter.

[fechter]

Ok, I see, I was certainly confused. I will be using 48v MW in series, so I only need that size zener, I see. I have two boards coming, and will end up using 3-4 mw, so if I need two for the 4 in series I am covered. Thanks Fechter.

I think you got it. Two boards should be good, and each one should have zeners for 48v.
Normally, I would expect only one board to do most of the limiting. This is normal. Since the supplies are in series, the current in each one (and therefore the power) will be equal. If the one doing the limiting runs out of compliance (like a really drained pack), then the second one may kick in during the first part of the charge until the pack voltage rises. It should not make any difference what order you place the supplies in series.

[nicobie]

Thanks Fechter. I think I finally got it.

Nick

[Degull]

Just to put my OCD to rest, the voltage for the diode selection, do you use the rated voltage of the power supply or the actual maximum output voltage measured with a DMM?

[Andje]

You use the actual output of the psu that you attach the board too. Then you add a zener to get the voltage down to 35v or under. So if you were using a "48v" supply tuned to 51v or something, 51-35=16v zener at least. If you were using 4 of those same supplies in series but tuned down to say 42v each to make 168v in total (40s), you would use a 42-35=7v zener at least. You would also probably need two boards when going beyond 2-3 psu in series.

Correct me if I'm wrong?

[fechter]

You use the actual output of the psu that you attach the board too. Then you add a zener to get the voltage down to 35v or under. So if you were using a "48v" supply tuned to 51v or something, 51-35=16v zener at least. If you were using 4 of those same supplies in series but tuned down to say 42v each to make 168v in total (40s), you would use a 42-35=7v zener at least. You would also probably need two boards when going beyond 2-3 psu in series.

Correct me if I'm wrong?

You are correct.
The zener should be selected for the maximum voltage the supply will actually run at, not the rated voltage. It should be OK if the zener is a little higher, but not lower (so the 7812 never gets over 35v).

[fechter]

I added a diagram of series connected supplies on page 1 at the end of the build pictures. A picture is worth a thousand words.

[megacycle]

Hey Fechter, got a opposite problem to most, where i'm wanting to limit around 130+ amps on a RSP3000/24V.
Was thinking i might need to seperate the circuit board from the shunt/s, or is there another way.
From from your design too, i think i'll be running shunt power of a halogen lamp unless
can i change the shunt value down to say 1 milliohm ?

[fechter]

It sound like modding the existing circuit will be a better option. Something like the R33 mod.

Otherwise, they do make 100+A shunts (for meters) but they are huge. Other than the shunt, the rest of the circuit would be OK.
Here's a 200A shunt: http://www.allelectronics.com/make-a-store/item/SNT-200/200-AMP-SHUNT-50MV-200-AMPS/1.html



They also have a 100A version.

To use one of these monster shunts, leave the little 20A shunt out of the circuit and use a pair of wires (they can be small) from the small screws on the monster shunt to the limiter board. The terminals on the limiter board might not fit the terminals on the supply, but you can just solder a couple of wires onto the board to make the connections.

[cor]

Hey Fechter, got a opposite problem to most, where i'm wanting to limit around 130+ amps on a RSP3000/24V.
Was thinking i might need to seperate the circuit board from the shunt/s....

Hi Megacycle,
I think you have the right solution - you can't send 130A through the traces of the current limiter board.
You can still use the board if it fits on your power supply (or connect it with short wires to it)
and use an external shunt like Fechter showed.
If you build this charger fixed into your vehicle, then you may already have a shunt that you use to measure
the current that your controller draws from your batteries.
You might be able (if this shunt is accessible) to attach two wires to it, twist them together if they need to
travel some distance as they carry a low voltage through a harsh environment, and connect them to the
current limiter board at the positions where the shunt would attach. That way you do get the measurement
without adding yet another shunt. Take care of the correct polarity of the shunt - during charging the
current is opposite to the polarity during discharge...
You could also inspect your 130A power supply to see if it has a built-in current limit that you could modify
to the value you want.

[megacycle]

Thanks guys for sureing me up and the added info on the parts, appreciate. Have to re-read R33 mod info again Fech.
Cor, thats a top idea with the controller shunt, i'm just about how the shunt is connected when say the charger is using it and the controller electronics is still connected to it and not in use.
I suppose because it's not in use and it's only sense circuitry it won't interfere with fechter's current limiter

Hey if i did go with a shunt, do you think this will do for the shunt, it's a strange looking peice of kit,
salvaged two from an electronic 240V/100A ac meter.
A lot of meters are rated 0.5S, which means they don't mind running at 2x for a while.
It's strange because the shunt looks like a peice of copper,welded to the tinned bars.
If the value was different should still be ok, just need circuit component value changes
If they are no good and i cant use them for the controller, could be useful to someone on the pm.
Cheers.

[cor]

Hi Megacycle, did you measure its resistance?
(easy to do with the 4-point connection method of sending a known current, for example 10A, through it
and use a milliVolt meter to measure how much voltage drop that 10A gives, each 10mV is 1 mOhm)
I am concerned that this AC circuit part does not have a precise resistance, because in a kWh meter,
it is the field strength, not the voltage drop, that gives the meter reading.
You know, 200A 75mV shunts are common and cheap: $5.79 with free shipping:
http://www.ebay.com/itm/DC-200A-75mV-/230755898583
so if you want to be sure and have accurate readings, then it is recommended to use
a shunt appropriate for the application.
Success!

[megacycle]

It looks to be about 0.3milliohms cor, not got a lab only had 2.76A constant and a calibrated DVM, measured 0.812mV.

Looking for the latest on the R33 and associated, its like a maze of info.Type in R33 in index and get nothing.
Can anyone point me to the latest thread phew, thanks in advance.