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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Howard Rush on August 27, 2014, 02:43:01 PM
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Will, what are those cool power supplies you showed me at the Nats?
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Howard,
For a battery charger or your airplane?
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Check your PM.
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Will
I may be looking for an upgrade from my current (no pun intended) 24 volt version soon. What power supplies are you endorsing ? :)
Dan
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What, Will? Is it a secret?
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WHAT A TEASE #^ come on let us in on it y1
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No secret they are really all over the RC Boards and I had 2 at the Nats. One used by me and the other by Joe Parisi(first prototype) which is now owned by Bob Hunt. I have not offered them openly for sale but I have 3 orders almost ready to ship. The reason I have not offered them or written about them until now is that I have had a few 24V versions fail immediately or within 24 hours. It was always DC grounded unit that failed. When repaired I have abused these things silly with NO failures to date. Mine has charged hundreds of batteries since March. Attached is a picture. The smaller one measures 7.5 inches long x3.25" high x 3.25" wide. That one produces 24V 75Amps when pushed to the max which would be almost impossible for any of us to do. (The larger is 24V 76 Amps just for comparison.) Its quiet but spools up when it gets hot, so the fans aren't always running fast. It EASY TO TRANSPORT almost anywhere because of its small size. It will also run on 240V so you can take it overseas. It also uses standard PC power cords which means no power cord mods. REMEMBER THESE ARE REPUROPSED SERVER POWER SUPPLIES THEREFORE ANY WARRENTIES WILL NOT APPLY!!!Here is the link to the instruction's. SEE NO SECRETS!!! http://www.rchelination.com/setting-hp-dps-1200fb-power-supply/?doing_wp_cron=1383225207.4715270996093750000000 These are the part numbers HP Power Supplies 440785-001 441830-001> These are available from many internet sources. Make these and use these at your own risk!! I am not going to be responsible for any of these failing or anyone being electrocuted. They can be regularly found on the RC boards already made up for some pretty good prices. If you want me to make them up you can contact me, but keep in mind I WILL NOT match the prices of the guys on the RC boards.
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I have a WDM power supply and my son has one as well. Both perform flawlessly.
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I recently discovered some interesting things about the HP DPS-1200FB power supply. First, instructions on the famous http://www.rchelination.com/setting-hp-dps-1200fb-power-supply/ say to use a 330 ohm to 1K ohm resistor between pins 33 and 36. Sometimes this works and sometimes it doesn't. One of mine worked for awhile, then didn't. I found another source which said to put a (zero ohm) jumper between those pins. That works. I suspect that the person recommending the resistor did so out of caution to prevent a problem when the user soldered it to the wrong pins. If the fan comes on, but electricity doesn't come out of the power supply, consider changing the resistor to a jumper.
Another interesting thing is that it when you connect two of them in series for 24V and only one is working (because of the aforementioned jumper issue or because the power cord isn't sufficiently plugged in), the power supply pair will continue to power the chargers at 12V less a diode drop. I can turn one of the series power supplies off and on and my chargers keep charging, seemingly oblivious to the change. Chargers (mine, anyhow) have a display view that tells you wht the charger input voltage is. You might take a peek at it from time to time to ensure you're getting the expected 24V from two power supplies in series.
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Howard,
I recently built up 3, 24V supplies. Two used the DPS600 supplies and one used the DPS1200. For the 1200 supplies I used a 1K ohm resistor on the #33 and #36 pins. I also found that the easiest way to disconnect the DC ground on one of the supplies was to remove the board and simply use a 6-32 tap on the existing hold down screw holes. I bought a box of 6-32 X 3/8" nylon screws and # 6 washers at a local electronic parts store. The #6 washers have to have the holes opened to approx. .150" to slip over the two standoffs on the output side. The back standoff was ground down slightly with the dremel tool to make sure the board didn't set too high in the case. After hooking everything up I let the supply run for about 36 hours. Think it will be alright. Will told me there was some issues with the durability with the unit made up with the DPS 1200 supplies. The units made up with the DPS 600 supplies seem to be a bit more robust but only put out 47A as opposed to 75A for the DPS1200 units.
Alan
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This may be a dumb question, but am I correct to assume that the reason for getting 24v input power to a charger is to get double the capability in charge amperage to the batteries?
So, now I am assuming you guys are using a parallel board to charge multiple drained batteries at once?
If I have all of the above correct, I have two questions-
1. How is balancing handled?
2. Do most chargers handle 24v vs 12v input power, or only certain models/brands?
Thanks. Very intriguing.
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Yes, you can get more amperage output and yes to parallel charging. The chargers also may work and heat less as the voltage step up to 18 - 24v is not being done on a board in the charger. No, not all chargers accept 24 volts.
A couple good chargers to look at when considering parallel charging where the charger will need substantial amperage/wattage output are the ichargers such as i306b and the Cellpro Powerlab 6 or 8.
ProgressiveRC has been a good source of chargers and information.
A couple of reads for beginning parallel charging
http://www.tjinguytech.com/charging-how-tos/parallel-charging
http://www.rchelicopterfun.com/parallel-lipo-charging.html
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I also found that the easiest way to disconnect the DC ground on one of the supplies was to remove the board and simply use a 6-32 tap on the existing hold down screw holes. I bought a box of 6-32 X 3/8" nylon screws and # 6 washers at a local electronic parts store. The #6 washers have to have the holes opened to approx. .150" to slip over the two standoffs on the output side. The back standoff was ground down slightly with the dremel tool to make sure the board didn't set too high in the case.
Alan
Alan,
I have done a couple of these as well and did similar with the 6/32 nylon screws. On the DC end I ground off the shoulder of the stand off so that the washer fit, removing the portion that inset into the board - if that description makes sense. I am not sure what you meant on the back standoff. If I understand correctly, that standoff is a redundant
AC ground along with the wire ground. Assuming that "back" standoff means on the fan/switch end, it can be left and reattached normally with the metal screw in reassembly. It certainly works fine either way, but can be left intact and then no height concern.
Fred
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Fred,
You're right about the rear standoff. Once I had the board out I just figured I'd tap the hole for the 6-32 and use the nylon bolt. I ground the standoff slightly as I used a washer under it and was worried about clearance in the case. I knew there was no connection to the case from that hold down but just felt like tapping another hole.
Have you had any issues with durability with the DPS1200 units?
Alan
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Thank you, Fred. H^^
Since I don't yet have my first E-powered U/C plane airworthy (but I will soon), I'll stick to what I know. I have a 4 port 320W charger at home that I use, mostly because I fly RC and charge different types of packs simultaneously.
I can easily see that 4 packs of 4S 2500-3000ma if paralleled would require more grunt to even charge at a 1C rate than our average charger puts out. So if I get bit hard by this facet of the hobby, I may have to upgrade.
I assume the balance question will be answered in the links you provided and will sponge the info out of them when I have time.
Thanks again,
Chris
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Alan,
No issues with the power supplies. I read a fair amount on the RC forums and saw where one fellow built and sold supplies. He had some problems and then changed suppliers and no further problems. I used one of the large Texas suppliers, Garland if I recall correctly, that had great reviews. I suspect that since they are all used/abused prior to our use, that quality can vary. It may depend on who pulls them and what parameters they use or their specific environment before our use. Like you, I tested them first. I clamped on the resistor and made sure that they worked before any soldering. I even clamped on a mild charger load. I build two sets, the first with a vertical stack and the next side by side. I used the vertical for a few months and now use side by side in a "box." I was tired of using a cardboard box with power supplies and charger(s) and batteries. My supplies are buried and hopefully will continue to work. I got ideas from Progressive RC and some RC forums.
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We made a power supply out of a PC power supply. It serves our purpose for now. Got the instructions from someone here, but can't remember who :-[
BIG Bear
RNMM/AMM
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Chris,
If I understand your charger correctly, you can charge 4 packs at once on individual outputs. Of course you can balance each pack individually, not like parallel. If your 320 watt charger puts out, not intakes 320, then you can charge 4x4s packs at 80 watts each. Round numbers 15 volts at about 5 amps each pack or more than 1C, total 15v x 5 amp x 4 or 300 watts. That is a slow field charge when you are waiting from full flight discharge, but not so bad in the morning at home if you start from storage charge of about 50%. If you need about 1500 mah input for each, perhaps with the end slow charging, say 30 minutes for all 4.
With parallel, you don't see the individual packs. For a 3000 mah pack x 4, the charger sees a 4 cell 12 amp pack. It still sees cell 1-4 on the balance port, but those cells are each 4 actual cells. You may need to use a cell checker to look at individual cells or occasionally check the individual packs/cells with the charger. Better chargers also look at internal resistance, another good measure of how the cell is doing.
Hope that helps and does not confuse the issue.
Fred
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Thanks, Fred.
I think I have a grasp of what you all are doing.
Yep, for my current situation, I am good to go. I'll investigate the idea of 24v vice 12v in the future if I get a little more "all in"
Thanks for the explanations. ;)
R,
Chris