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Old Jan 28, 2011, 01:30 AM
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Originally Posted by SAPilot View Post
I recently purchased a 3010 and I love it. However, I can not get the log files to display on the menu screen. The log files screen shows 31 h: 38 and 2016 Kb but when I press the start button the screen shows [Select 0/0] and No file find! I assume the logs are OFF but the manual doesn't specify how to reset it. Anyone knows how to correct this? Thanks,
Press and hold Inc, and it should go into a File Create screen. Press Enter to accept the log file name. Now it should say Select[1/1], and now whatever you do (for the next 31 hours of activity) should be logged.

This is on page 26 of the manual, but can be a bit hard to follow!
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Old Jan 28, 2011, 02:04 AM
Joe
Bend, OR
Joined Jun 2010
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Originally Posted by eecs View Post
I have a 206B that I bought mainly to use with some larger capacity (over 1000Wh) batteries. The 20A charge rate is fine; however, when I want to measure capacity, the 206B's 20W internal limit means they would take over two entire days to discharge! I needed something faster than that.

I really like the idea of the regenerative discharge, but I don't have any large batteries that I can afford to leave sitting around dead flat waiting for when I want to discharge something.

I looked at the external expanding discharge mode, but as far as I could see it needed a different high-power resistor for each different battery voltage and discharge current that I wanted to use. I wanted to be able to choose any current I pleased, with any battery I wanted to discharge, and always use the same power sink.

So I went back to thinking about the regenerative discharge mode, and realized that achieving what I wanted was rather simple. Here is my circuit:
Attachment 3759206

I used an old CPU cooler, and mounted a P-channel MOSFET that I had in my junk box. [I actually used a lower-powered (and much cheaper) MOSFET; the one shown in the circuit should be good for 300W discharge given an adequate heatsink.]

I used a low-power 12V supply just to start the discharge (something has to power the 206B until I press the "go" button).

I used a cheap diode to prevent the power supply being driven by the iCharger (note that a higher current diode would be needed if I wanted to leave the discharger connected during charging).

I chose a P-channel MOSFET rather than a cheaper N-channel one because I wanted to be able to join it to an earthed heatsink without losing thermal efficiency on an isolating washer.

The 100nF ceramic capacitor prevents high-frequency ringing. The discharger actually seemed to work OK without this, but my multimeter couldn't make sense of the voltage or current.

The fan serves as a load to make sure the power supply voltage does not rise above its specified voltage. It should be replaced by some kind of resistor if a passive heatsink is used.

The MOSFET turns on enough to carry 20A with a GS voltage of about 5V. The voltage at the iCharger is therefore limited to about 17V. 20A * 17V is over 300W, so this is not a limiting factor.

If the fan fails then there is nothing to stop the MOSFET cooking itself, and I don't know how it fails: flames, or just a puff of smoke? Connecting the iCharger's temperature sensor to the heatsink, and enabling termination at some suitable temperature, would probably be wise.

Hope this is of interest to someone!
This is a great solution, I'm interested in building one, but I need your advice on the components to use that will suit my needs. I understand (from your post) that the specified MOSFET will handle 300W, which is way more than I need. I use a 106b+ which appears to be limited to only 7A discharge, and is fine for my needs.

So... what would you suggest for a MOSFET, given some headroom? One other thing you mentioned is that in order to keep the discharger inline during charging I would need to use a high power diode. The 106 is limited to 10A and it's unlikely I'll ever charge more than 4S packs, so I'm only pushing the charger 150W, and given the 11+ volts under load, have rarely seen more than 15A on the supply. Can you recommend a diode that would handle the charge load?

I'd really like to end the constant swapping between PS and Pb depending on whether I need to charge/discharge, and this appears to be the perfect solution! I'd just like to do it cost effectively. Thanks for your help. --Joe
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Old Jan 28, 2011, 03:08 AM
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Originally Posted by jrej View Post
This is a great solution, I'm interested in building one, but I need your advice on the components to use that will suit my needs. I understand (from your post) that the specified MOSFET will handle 300W, which is way more than I need. I use a 106b+ which appears to be limited to only 7A discharge, and is fine for my needs.

So... what would you suggest for a MOSFET, given some headroom? One other thing you mentioned is that in order to keep the discharger inline during charging I would need to use a high power diode. The 106 is limited to 10A and it's unlikely I'll ever charge more than 4S packs, so I'm only pushing the charger 150W, and given the 11+ volts under load, have rarely seen more than 15A on the supply. Can you recommend a diode that would handle the charge load?
If you only need 150W of dissipation then you can certainly get away with a much cheaper MOSFET. The really cheap TO-220 package still won't achieve 150W, but the TO-247 should be OK. Perhaps something like the IXTH90P10P (still not cheap, but about half the price of the 300W MOSFET). Digikey sells it for $8.88. It should do over 170W, which is all the 106B+ can handle. It will conduct 10A with a Vgs of -5.25V, which means it will stay under the 106B+'s 17.5V limit even at 170W.

My error: the 106B+'s regenerative discharge limit is only 17V, which does not quite leave enough headroom for 5.25V on a 12V supply. If your supply is only 11.75V you will be OK. Otherwise, and especially if you want cheaper components, see my next posting about a circuit that uses two cheap N-channel MOSFETs instead...


If you plan to leave the discharger connected during charging then you probably want a diode with a low forward voltage (no point in wasting more power than you can help). Maybe something like the STPS20L15D (rated for 19A at only 0.41V drop). [Note for others: this diode is only rated for 15V, which is fine for the 106B+ and 1010B+, but would be too low for the other chargers.]

What will you do with the discharger cooling fan when you are charging? Just leave it running?
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Last edited by eecs; Jan 28, 2011 at 05:07 AM. Reason: 106B+ can only support 17V regenerative discharge, not 17.5V
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Old Jan 28, 2011, 04:42 AM
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Re: High power discharges

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Originally Posted by eecs View Post
Unfortunately putting the MOSFETs in parallel is not likely to be stable. Whichever MOSFET happens to have the lowest Vgs threshold will draw more than its share of the current, and therefore get hotter than the others, and therefore lower its threshold and draw an even larger share of the current and so on.
I was forgetting the obvious solution to this, which is to give each MOSFET a resistor to allow the currents to equalize. This allows any number of (smaller and cheaper) N-channel MOSFETS to be connected in parallel to achieve any desired power sink:
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Description: 1000W 6-MOSFET discharger circuit

These FDA69N25 N-channel MOSFETs will dissipate about 176W each (assuming a 60 C heatsink and good thermal grease), so 6 of them will handle 1000W.

The drains are all connected in parallel, so they can share one heatsink. However, the heatsink will still be live, so watch for shorts!

Note, if it is not clear from the diagram, that the gates are all connected to each other, but each source is only connected to its own resistor and capacitor.

For the 208B and 206B this could be scaled back to four really cheap TO-220 MOSFETS:
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Description: 350W 4-MOSFET discharger circuit

For the 106B+ it could be scaled back to two MOSFETS (logic-level ones this time, since we don't have much headroom):
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Description: 150W 4-MOSFET discharger circuit

Again I have not built any of these myself, so if anyone tries any of these circuits then please post and let us know if they work!
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Old Jan 28, 2011, 06:41 AM
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Poland
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Originally Posted by eecs View Post
The way I see it, I set the discharge rate (say to 5A for a battery that can currently deliver 12V at 5A) which means the power will be fixed (60W in my example) regardless of the voltage the iCharger has to deliver (15V at 4A or 20V at 3A or whatever) to the sink. So in that sense the iCharger "input" voltage is a function of the power.
I see. You don't use regenerative DSC settings to control your circuit.
You just set battery current letting the charger to adjust voltage and current within limits.
I'll prepare something for my 208B (350 W, limits: 20 A and 31 V). It's powered from 12 V PSU. So, ~17 V and 20 A gives ~340 W.
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Old Jan 28, 2011, 07:31 AM
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I see. You don't use regenerative DSC settings to control your circuit.
No. I could (and probably should, to protect my discharger from overload) use the regenerative DSC current limit, but using the voltage limit would be pointless: either the limit would not come into effect (if too high), or else (if set low enough to have an effect) the discharger would very quickly be unable to sink any significant current.

Quote:
I'll prepare something for my 208B (350 W, limits: 20 A and 31 V). It's powered from 12 V PSU. So, ~17 V and 20 A gives ~340 W.
To achieve 340W with my suggested P-channel MOSFET you would need to keep its heatsink below about 50 C.
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Old Jan 28, 2011, 07:51 AM
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United States, OR, Beaverton
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Originally Posted by eecs View Post
Again I have not built any of these myself, so if anyone tries any of these circuits then please post and let us know if they work!
Seems like prudence would dictate a little spice first.
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Old Jan 28, 2011, 08:01 AM
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Poland
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Originally Posted by eecs View Post
To achieve 340W with my suggested P-channel MOSFET you would need to keep its heatsink below about 50 C.
I'm starting to think about water cooling
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Old Jan 28, 2011, 09:23 AM
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Originally Posted by LeszekJ View Post
I'm starting to think about water cooling
A horse trough should do the trick.

If you think about the biggest uses of power in your home it doesn't take long to figure out they are heating elements (aka resistors), the oven and electric water heater (for those of us not using gas). A few years back I helped my father test a smaller Onan generator (30kW 3-phase) and for a load we used three hot water heater elements mounted in the bottom of a 5 gallon bucket of water in a delta configuration (I hope I don't need to point out the obvious hazards of heating elements next to plastic and the exposed wire terminals everywhere). It worked quite well and we had that 5 gallons of water at a boil in no time.

The real trick for you will be having a load resistance that is controllable, hence the transistors, but it is little different than how the CBA-III and CamLight CC-400 work.
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Old Jan 28, 2011, 10:57 AM
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Poland
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Originally Posted by SteveM732 View Post
A horse trough should do the trick.
Here, where I live, it's easier to be eaten by a polar bear than to get a horse trough Greetings to Oregon.

Quote:
Originally Posted by SteveM732 View Post
The real trick for you will be having a load resistance that is controllable, hence the transistors, but it is little different than how the CBA-III and CamLight CC-400 work.
That is what we are discussing. I can see a small difference: 50 bucks instead 400.
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Old Jan 28, 2011, 02:04 PM
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France
Joined May 2006
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Hello ,
For the first time is used the discharge mode on my 3S 2100mah 20-40c pack and it wont discharge at more than 1.3Amp while i asked for 4A or more even .

Why is that , and how to discharge at higher rate please ?
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Old Jan 28, 2011, 02:18 PM
Southern Pride
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Haralson County GA. USA
Joined Oct 2004
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Different iChargers have different max. internal discharge rate abilities (watts).

Example 25 watts / 12.6V (3S LiPoly) =1.98Amps.
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Old Jan 28, 2011, 03:11 PM
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ah thanks , so thats charger related , its not much rate but will do
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Old Jan 28, 2011, 11:54 PM
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Re: High power discharges

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Originally Posted by SteveM732 View Post
Seems like prudence would dictate a little spice first.
SPICE can verify the general principle. For example, here are some SPICE characteristic plots (done with similar components for which I could find SPICE models) for my 6-MOSFET parallel circuit at different temperatures:
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Description:
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Description:
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Size: 20.6 KB
Description:

However, SPICE predicts a perfect sharing of load between the MOSFETS even without any load-sharing resistors, since as far as SPICE is concerned six of the same MOSFETS are absolutely identical! My main concern is with how well the load will be shared if the MOSFETS do not have perfectly matched Vgs threshold voltages.

If we assume the hottest MOSFET junction will be 150 C, and that the heatsink is 60 C, then we can assume the coolest MOSFET junction will be at least 60 C. The SPICE model then reports a difference in Vgs of about 0.05V. If we can assume that the random variation in threshold voltages is much less than the temperature dependence, then the SPICE model predicts less than 5% possible variation between my six MOSFETs, which should be fine.

These are big assumptions, so I would still like to confirm that a real circuit actually matched the SPICE model...
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Old Jan 29, 2011, 05:23 AM
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Antony (France)
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Quote:
Originally Posted by eecs View Post
I was forgetting the obvious solution to this, which is to give each MOSFET a resistor to allow the currents to equalize. This allows any number of (smaller and cheaper) N-channel MOSFETS to be connected in parallel to achieve any desired power sink:

These FDA69N25 N-channel MOSFETs will dissipate about 176W each (assuming a 60 C heatsink and good thermal grease), so 6 of them will handle 1000W.

The drains are all connected in parallel, so they can share one heatsink. However, the heatsink will still be live, so watch for shorts!

Note, if it is not clear from the diagram, that the gates are all connected to each other, but each source is only connected to its own resistor and capacitor...

Again I have not built any of these myself, so if anyone tries any of these circuits then please post and let us know if they work!
Hi
Just a question
OR2,5W meaning ??
0.2 ohm , 5W wattage ? or ?
Louis
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