Your choice of powder scale?

My power supply for the Chargemaster says it is 9volts. They may do fine with 12 volts, but then again....

A diode drops about 0.6 volts; if you rigged up about 4 or 5 diodes in series, you would have a nice 9 volts from a 12 volt battery. My power supplly said it was 1 Amp, so 1 AMp diodes from radio shack would probably work. If not, 3 Amp ones would work fine.

They sell 400V 1Amp diodes for fairly cheap. Because there is a motor inside, there is always the chance that the diodes would blow, but then you could just short them out. One reverse diode would prevent any risk at all.

I'm at work and don't have any way to put up a schematic.

There are also fancy 3 terminal regulators, but for such a simple drop, diodes are much easier.

(I was a EE in my former life)
 
I just ordered a sealed lead/acid battery and charger from batteryspace.com. The battery is 12V 12AH and is about 6" X 4" X 4".

http://www.batteryspace.com/sealedleadacidbattery12v12ah144whforupsseascootere-bikes.aspx

They have smaller sizes.

Sealed Lead Acid Battery: 12V 12AH (144 Wh) for UPS, Seascooter / E-bike (S) LA-12V12 1 $26.95
Lead Acid Smart Charger (3.0 A) for 12V Lead Acid Battery 3 stages floating for Worldwide, UL/CE Listed CH-UNLA1230UL 1 $20.95

I have a small Coleman 400 watt inverter that I'll connect to the battery and plug the Chargemaster into the inverter. This is the setup that Glen Oakes used at Tomball.

DSCN0877.jpg
 
Docsleepy,

How many mA does your Chargemaster draw both when idle and when measuring powder? Also, what is the capacity of a 8 D cell battery pack in mAh? About how much measuring time is involved in loading say, 200 30 gr. loads (generous amount for a weekend match)? Might as well put that EE experience to work. ;) I think you fellers are swatting a gnat with a sledgehammer. I hasten to point out that a will kill a gnat every time, its just that it takes a lot more effort to swing than a flyswatter.:D
 
Boyd Allen said:
Docsleepy,

How many mA does your Chargemaster draw both when idle and when measuring powder? Also, what is the capacity of a 8 D cell battery pack in mAh? About how much measuring time is involved in loading say, 200 30 gr. loads (generous amount for a weekend match)? Might as well put that EE experience to work. ;) I think you fellers are swatting a gnat with a sledgehammer. I hasten to point out that a will kill a gnat every time, its just that it takes a lot more effort to swing than a flyswatter.:D
Click to expand...


DC Current draw: I don't know for certain, haven't measured it. [didn't see answer on a quick internet search] But I think you are right on, because from the sound, and work that the little motor is doing, it ain't much -- certainly the motor in there is in the same ballpark as a child's toy race car (most run off C or AA cells!). The digital SCALE of course runs all the time, but it is probably equal or less draw.

Measuring Time: Mine takes just about 20 seconds to deliver 25-27 grains, so we are talking 30 seconds for 30, or 100 minutes total (for the weekend) which is under two hours.

D cells are funny; alkalines are 12 Amp-hour or so, but I've seen some cheap rechargeables in my day that were actually tiny cells in a "large case". REgular RayoVac or Eveready or Duracell alkalines are probably 12 Amp hour or more.

I would bet you could run it just fine off D cells (6 in series to make about 9 volts). It might go multiple weekends! Keep some spares with you. If cost is a factor, rechargeable D would be useful. Or a 12 volt, 7 amp-hour sealed lead acid [that's what is in my home burglar alarm: you can get them at Tractor Supply Company for $21.00; they sell them to run people's electric fences] and use the diode trick I suggested above. If cost isn't a factor, the D cells should work fine.

Certainly doesn't need a car battery.
I'm at work, but will take a look next time I'm home and awake.
I've been hauling an extension cord to the range with mine. This discussion might convince me to get some batteries and make my effort easier.
 
adamsgt said:
I just ordered a sealed lead/acid battery and charger from batteryspace.com. The battery is 12V 12AH and is about 6" X 4" X 4".

I have a small Coleman 400 watt inverter that I'll connect to the battery and plug the Chargemaster into the inverter. This is the setup that Glen Oakes used at Tomball.
QUOTE]

Very slick system.

I just want to suggest that taking 12V dc and making 120 switched-square-wave AC out of it with an inverter and then using a wall wort transformer to make it back into DC for Chargemaster does have some inefficiencies...feel that wall wort transformer on a warm day and be certain that it doesn't get too hot from the unusual waveform it is having to work with (might be fine, I dunno). Also, on a project I did to provide solar power for a group in Africa, I learned that the larger off-the-shelf inverters have a fairly high resting (wasted) current. I got the lowest battery drain by going to the smallest inverter that would work -- a 50 or 75 watt version for my particular application. If a smaller inverter would work, you might get better battery life out of it (if that is a problem; I dunno).

The only think I might add if I were going to power the Chargemaster off a DC battrery (directly, without the inverter), beyond some form of voltage drop to 9 volts (e.g., diodes) is maybe an inline fuse at 1 or 2 amps. An automotive type blade fuse device (walmart) would work fine. Batteries can deliver pretty high peak currents (way way more than the RCBS wall charger) and if something went wrong inside the chargemaster (they ARE loaded with gunpowder, right?) I would want to avoid a fire...
Click to expand...
 
docsleepy said:
I just want to suggest that taking 12V dc and making 120 switched-square-wave AC out of it with an inverter and then using a wall wort transformer to make it back into DC for Chargemaster does have some inefficiencies...feel that wall wort transformer on a warm day and be certain that it doesn't get too hot from the unusual waveform it is having to work with (might be fine, I dunno). QUOTE]

I was also dubious about going from DC to AC to DC. But it seemed a simple if kludgey solution. Glen said it seems to work fine so I decided to give it a whirl. My last electronics training was in 1960 when I was going through Aviation Cadet training as a navigator. Hopefully, some of the more knowledgeable EE's among this group can offer a more elegant solution. :)
Click to expand...
 
I don't have any particular deep expertise to offer on this so take it for what it's worth. Inexpensive inverters don't possess true RMS sine wave output but have modified square wave outputs that are filtered to reduce harmonics. Many members on this forum report their scale's sensitivity to RFI from flourescent lights or cell phones. It seems to me that nothing has a cleaner power output than a battery. So why do we use a battery to drive an inverter to drive an ac power supply to in turn power a digital scale? Simpler is often superior to more complex. Denver says scales drift with changes in DC voltage but it seems to me that a 5 or 10 amp/hour sealed wet cell battery isn't going to drop much over even extended periods of loading or load development. I'll try it and report back.

Greg
 
DC batteries / gel type can be purchased from hunting supply
companies in nearly any voltage, complete with charger.
Can't think of a simpler way
 
Bob Kingsbury said:
DC batteries / gel type can be purchased from hunting supply
companies in nearly any voltage, complete with charger.
Can't think of a simpler way
Click to expand...

So far I haven't come across any sealed lead/acid batteries in 9V. However my web search hasn't been real aggressive yet. :)
 
CM transformer output

docsleepy,

For what its worth; the output of my CM transformer actually measured closer to 12 volts than 9 volts, with no load.

Brian
 
Rcbs

adamsgt,

I did. Understandably, they would not recommend any method of running the CM off of direct DC. Could be that they may be studying about coming out with a "portable" Chargemaster. Could be, the rep. that I spoke with had no knowledge of the electronics involved.

Brian
 
admsgt

I just checked some industrial sources for your 9 volt sealed lead acid batteries and the 9 volt just doesn't seem to be the most popular. McMaster Carr, MSC, Grainger, and Batteries.com don't show a 9 volt SLA battery.
Possibly the 12v with the diodes are a better idea as the 12 volt batteries come in all sizes and Ah.
It might be out there but not as a popular item. Let me know if you hear of a site.
Centerfire
 
Centerfire said:
I just checked some industrial sources for your 9 volt sealed lead acid batteries and the 9 volt just doesn't seem to be the most popular. McMaster Carr, MSC, Grainger, and Batteries.com don't show a 9 volt SLA battery.
Possibly the 12v with the diodes are a better idea as the 12 volt batteries come in all sizes and Ah.
It might be out there but not as a popular item. Let me know if you hear of a site.
Centerfire
Click to expand...

I think we need docsleepy to come up with a design we can cobble together quickly. At one time I had built nearly every piece of electronic test equipment in the Heathkit catalog. Got pretty good with a soldering iron. Still have them. Also, maybe there's a business opportunity here for someone that has more energy than me. :p
 
Lead acid cells produce 2 volts so a lead acid battery will always produce voltage that is an even number (2 X number of cells in series). Other battery types have their own voltages.
 
I guess I assumed that everyone knows that 8 D cells, in series, gives 12 volts , and as I posted earlier Jerry Hensler has been running that setup to power his Chargemaster, for some time, with no problems. He figures that the drain is so small that it should last him a year of match use, before the batteries need replacing.
 
Hi,

I cut one of the wires and measured the current drain on my chargemaster.

Interesting point, just connected, but OFF, it pulls 15 mA (.015 Amp) -- so put in a switch! (I had a boat where the radios did the same thing, killing batteries routinely, until I figured it out)

Once turned ON, the digital scale etc pull 50 mA (.050 Amps).

When dispensing, it had the expected initial surge to get the motor going, and then leveled out around 200 mA (.200 Amps)

One dispensing of 25-30 grains will be 30 seconds @ 0.200 Amps = 0.0016 amp-hours.

If we conservatively assume 10 Amp Hours in D-cells, then you could charge 6000 cases before the batteries were completely done--if you had no time spent jusb being "on". (Wikipedia says alkalines are closer to 20 Amp Hours, so this is way conservative)

If you are going to JUST leave it 'on', it would go for 200 hours.

200 loads (one weekend) = 0.33 amp hours (3% of battery capacity)
12 hours of ON time (one weekend?) = 0.6 amp hours (6% of battery capacity)

Hence you should be able to do about 10 weekends on one set of batteries.
This is sounding very successful to me.

I would recommend 6 [9 volts) or 7 [10.5 volts] "D" alkaline (NOT carbon-zinc cheapies!) in series, a switch [or else disconnect when not using], and maybe a 2amp inline fuse (just to covery my liabilities).

Obviously the fellow you talked to is correct -- this is a good solution and will go a long while. I think I'm going to pick up a battery holder or so and rig this up for myself. If you just do the D cells, you should not need any voltage regulation, or diodes.

I didn't measure the voltage of my supply (pretty hurried) but I'll look into that. It is specified as 9V, but that may have been at a much larger load, so it may well be 11 or more at this light load -- so the folks running them directly off 12V gell-cells may be fine. But no promises from ME! on that one!
 
Also, Boyd, 8 batteries may be perfectly safe. I just cant swear to it, since I don't have the internal schematics to look at to see how they are doing internal voltage regulation. You can bet that they have a 5V regulator inside there. (so I really wouldn't worry much about small changes in the battery voltages as they get weaker) It may or may not do OK on 12 volt input -- problem might occur in Texas in the summer, and might do fine in Minnesota for the whole year. I just can't say with any certainty. And I doubt you'll get the manufacturer to agree to anything, due to liability concerns.
 
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