Power tool lithium battery brand comparison

All the cordless power tools today are using lithium battery packs, replacing the old nicad batteries used in the past.

I have a variety of brands of cordless tools, including at lot of random junk of course, and I’ve been comparing the design of the different brands of lithium battery packs, so I can adapt batteries across different brands of tools.

Ryobi Ridgid Dewalt Bosch Black&Decker, Porter-Cable, Stanley Fatmax, Craftsman 20V Makita Milwaukee
Product line One+ 18v 18v Lithium  20V Max XR 18V Lithium 20V Lithium LXT M18
Personally inspected Yes Yes Yes Yes No No No
Charge over-voltage protection Pack Pack Charger Charger Charger Charger? ?
Discharge under-voltage protection Pack Pack Tool Tool Tool Tool? Tool
Cell balancing In pack In pack In charger None  In pack None in older LXT packs; unsure about newer ?
Physical attachment Neck Flat  Flat Flat Flat Flat Flat
Other notes Fits all Ryobi 18v tools, including older Nicad line Fits older 18v Nicad tools Adapter available to use on older 18v Nicad tools Brands almost identical but not quite; can be interchanged by trimming plastic notches or tabs

Nicad batteries are simple. You just need two wires from the pack to power the tool, run the tool until it got too slow or weak, then recharge the battery. But the batteries were heavy, and voltage (and tool speed and power) drops rather quickly as the charge is depleted.

Lithium batteries provide better results in the tools, but need protection circuitry to prevent over-charging (which can start a fire) or over-discharging (which can permanently damage the battery cells).

Battery packs with built-in protection circuits inside the pack are easier to retrofit to tools originally designed for nicads.  Ryobi and Ridgid have even kept the same battery connection from their older 18 volt nicad tool line into their newer lithium line of tools.  Dewalt changed battery connections, but also supplies an adapter (DCA1820) to use the newer XR lithium packs with the older 18v nicad XRP line of tools.  Other brands like Makita, Black&Decker, Porter-Cable provide no backwards compatibility.

Note that all of the brands advertised as 18v, 20v, or 20v Max, all operate at the same voltage and power.  All are made up of 5 lithium cells in series that measure about 20v fully charged, then drop quickly to an average of 18v in use.  20v battery packs and product lines do NOT have more power than 18v packs and product lines; it is just marketing spin.

Power tool lithium battery test jig

I got a pile of dead or questionable 18-volt power tool lithium battery packs on EBay for $1; just the right price for my hobby budget!  They need to be load tested, to determine how much usable capacity they have. Here’s my jig for that.

The battery powers a 120-volt inverter, which runs a wall clock.  I set the clock to noon (or midnight, whichever you prefer) and connect a fully-charged battery.  The voltage drops as the lithium battery pack discharges, and the internal protection circuit cuts out the battery when it gets to 15v, and the clock stops there.  That tells me the working time of the battery pack at 32 watts, without needing to watch it the entire time.  I just come back later and see how long the clock ran.  Et voila!  Easy and reasonable capacity measurement.

The inverter didn’t like being powered directly by the 18v battery.   It was designed to work with 12v automotive power and shuts off if the input power is over 15 volts.  So I added a cheap DC-DC converter to step down the battery voltage from 18v to 13v.

The inverter and clock draw about 4 watts, and there is also a 28-watt LED lamp for extra load.  A voltmeter/ammeter tells me that I’m drawing 32 watts with the lamp, inverter, and clock. It remains pretty linear; as battery voltage drops from 20v to 15v, the amperage goes from about 1.5 to 2.

I first tested my new, known-good battery packs, and found that I get about 30 minutes of run time for each rated amp-hour on the pack.   For example, a 1.5ah battery ran for 44 minutes, a 2.0ah ran for 59 minutes, and a 4.0ah pack ran for 118 minutes. Rather surprisingly consistent!  I got the same results with Ryobi, Dewalt, Bosch, and Ridgid packs.  That makes sense since they are all using common 18650 lithium cells internally, from reputable lithium cell manufacturers that rate their cell capacities the same way.

Ryobi and Ridgid packs have internal protection circuits that cut off when voltage drops to 15v.  Dewalt and Bosch lithium-powered tools don’t have protection circuits inside the battery pack; they put it in the tools and chargers.  Dewalt “20V Max” batteries provide all cell connections on the pack, so I was able to use an external lithium 5S alarm board that beeped at me when it got down to 15v.  Bosch 18v lithium packs don’t have internal protection, and they don’t expose the cell balancing connections to allow a common lithium alarm board either, so I just had to watch the voltmeter for when it dropped to 15v.  I think Bosch has a poor design, because the packs cannot be cell balance monitored or charged at all.

Interesting result: doing the math, the run times are about 90% of the stated capacity of the battery packs.  I believe there are two reasons for that.  First, I suspect the watt-hour capacity of the pack as published by the manufacturer is slightly exaggerated.  It assumes 18v for the entire capacity (2.0 amp-hour pack says 36 watt-hours), but the working voltage actually ranges from 18v down to 16v during battery depletion.  Second, the lithium protection circuit stops the current flow before battery is fully depleted, to avoid damaging the lithium cells.  Assuming the discrepancy is mostly due to the cell protection, a 10% safety margin is good.

Now it’s time to test the questionable packs and see what I can salvage!


Refrigerator went to beauty salon

Well sort of.

Here is why I broke the trim on the refrigerator.  Or rather, here is what I was doing when I broke the trim on the refrigerator.  Why I broke it is, well, ok, where was I?

The white trim on the white fridge had yellowed over the last 10 years.  I happened to have read in the past about people restoring old ABS computer cases and video game consoles with some sort of bleaching process involving a “RetroBright” glop product, or a hydrogen peroxide and who-knows-what lethal concoction you can make in your own science lab at home.  (You know those nerds and their projects!  Heh heh!  Ahem.)  Which of course I could do, but I was feeling lazy and I wanted instant gratification.

Fortunately, Dr. Youtube quickly educated me that in these modern times all I really need is some hair bleaching peroxide cream and UV light.   I already had my UV light source ready at hand, powered by my fusion reactor conveniently stored at a safe distance of 93 million miles, readily available now that IT’S FINALLY FREAKIN’ AUGUST ALREADY!! ABOUT TIME WE GOT SOME SUNSHINE!! GOSH!!   Sorry, a little Seasonal Affective Disorder lag in the Pacific Northwest; now back to the story.

A short trip to Sally Beauty Supply store and $3 got me a bottle of “40 volume peroxide cream 12%” and now I’m beautiful!  Er, I mean, now the trim on the fridge is beautiful again.

Slop on the peroxide cream with a brush, put it in a clear plastic bag, and sit it in the sun for a few hours.  Et voila!  It worked.  One of the pieces was ABS, and one was polypropylene.  The bleaching process worked best on the ABS, but the polypropylene worked pretty well also.

One theory is that the bromine added as a flame retardant is what turns the plastic yellow.  Something sure was retardant.  But regardless of the cause, the bleaching worked and it looks much better now.  Just a few more trim pieces to break off, I mean remove carefully, and the fridge will look good as new.  And stylin’ with its new ‘do !

I just won’t use the hammer and block of wood to remove the other trim pieces like I did the first ones.  Hey, Dr. Youtube showed me how to easily slide them off.  Mine was just a little stuck.  Where’s that bigger hammer? The doc just didn’t clarify it was for a different model.  Hmmph!

Anyways, if you have any white plastic that has yellowed over time, this really did work well to restore it; give it a try!

Oh, and the broken trim pieces?  Fixed with spin welding!

Plastic spin welding fixed fridge

I took a piece of plastic trim off of the refrigerator door, and the snap tabs broke right off. Dang it!

The piece was marked PP, polypropylene, which just can’t be glued.  So I used spin welding to reattach them.

I cut a thin strip from a plastic lid marked PP and chucked it in the Dremel. Spun it up and worked it into the fillets. Friction melted it right in there, welding the tabs back on.

I put it back on the door and the tabs are holding on tight.  Perfect!



Enable Memcache for Owncloud 8.2 on Ubuntu 14.04

Supposedly you can improve Owncloud performance by adding a memory caching module into your web server software (Apache). Or at least the Owncloud admin page says so, and complains if you don’t have one.

If you are running Owncloud 8.2 on Ubuntu 14.04, you likely have PHP version 5.5. Owncloud recommends “APCu” caching software version 4.0.6 or higher, but the version in the Ubuntu 14.04 repositories is too old (4.0.2).

This is a known issue with workaround instructions to install a newer version using dpkg. I found version 4.0.7 in the Ubuntu repositories and installed it using the instructions on the issue page. It eliminated the Owncloud admin warning.

Rewrite MEID on Galaxy S2 Epic 4G Touch

I bought another Android smart phone on EBay to use on Ting Mobile. This one was a Samsung Galaxy S2 “Epic 4G Touch” SPH-D710. All excited, I looked in the phone information screen to get the MEID serial number, and entered it into the new phone activation screen on the Ting website. Ting told me it couldn’t activate a Boost Mobile clam shell phone. What the phreak?!?!

I looked at the phone’s label in the battery compartment. The MEID was different there. Ting told me that number was good, and belonged to this model. Argh. Somebody changed the serial number programmed into the phone. As far as the radio signals go, the cell tower thought this WAS a Boost Mobile clamshell phone talking to it.

Apparently someone previously had a Boost Mobile account with a cheap phone, and wanted to use this Galaxy S2 instead without changing their account, so they programmed the Boost Mobile phone’s MEID into the S2. (Strictly speaking, this is considered a no-no by the big carriers. They feel they have the right to charge you more for service on a fancier phone, for features you don’t use. If you don’t like that, you can use the old cruddy phone. If you don’t like it, use two tin cans and some string, as fas as they care.) I don’t have a problem with someone doing this number swap for themselves, but when you later go to sell the phone you should at least put it back to its original configuration so you don’t mess up the buyer. Like me. Grumble…

Ting runs on the Sprint network, and Sprint doesn’t allow Ting to activate phones from Sprint’s subsidiaries like Boost Mobile. I could not activate the Boost Mobile MEID on Ting, so I had two choices: ship the phone back to the EBay seller, or reprogram the MEID back to a usable one. I decided to try reprogramming it.

Lots of people put new versions of the software on their Android phone, also known as “flashing a new ROM”. Many people consider this to be obscure phone magic best left to hardcore nerds, even though it is usually easy to find the information for common phone models. The ebay seller of this phone had indicated it was flashed with alternate software, and I was fine with that. I knew I would have no problem with that, since I could reflash it back to the stock Samsung/Sprint software with no trouble if needed.

However, it gets much more complex when you change settings buried deep in the phone, such as radio controls or the MEID. The phone carriers and manufacturers as a rule do not want phone owners to change these values. Independent cell phone repair shops often have the software and expertise to do this, but at the individual or hobbyist level it is rather uncommon.

Fortunately, though, it is not impossible or unavailable; just difficult because of obscurity. The knowledge is scattered among many different Internet forum postings and bits and pieces of software notes. The details and techniques are different for every phone make, model, carrier, and software version. It takes a lot of digging and persistence. You have to be tenacious. Or just plain cheap and stubborn. (You already know where I fall on that spectrum.)

Sprint (and Verizon, and a few other minor carriers) use the CDMA radio system instead of the more-common GSM. The primary tool for changing the settings in Sprint phones is “CDMA Workshop”. I couldn’t get the free demo version to work, so I had to dig around to find other software. I could have spent $600 for the paid unlocked version of CDMA Workshop, but I didn’t find that to be a good value for fixing a phone worth less than $100, cheapskate that I am.

I found two pieces of software that would talk to my phone:

I also found that there were not one, but TWO passwords required to reprogram my phone. Drat and double-drat!

The first password needed is a six-digit number, called either the SPC or MSL code. I found some documentation that said they are the same, and other docs saying they are different. The various software programs call it the SPC, but seem to work correctly using the MSL value there. OK, whatever.

The normal situation with CDMA carriers like Sprint and Verizon is that they are the only ones who know your phone’s MSL code, and will not give it out willingly to you. That’s justified if they subsidized a portion of the cost of the phone, which is the case with most phone contracts in the US. But once you’ve fully paid for it and they still won’t give it out, they’re just being greedy corporate jerks. Enlightened, customer-friendly carriers like Ting will happily give it to their customers. Unfortunately, I could not get the MSL from Ting until I activated the phone, and I couldn’t activate the phone without reprogramming it, and I couldn’t reprogram it without the MSL password. Catch-22. Dang!

Fortunately, the first program cdmaDevTerm showed me that my SPC/MSL code had been reprogrammed into the phone to “000000”. This was the only convenient side effect of the earlier owner’s reprogramming. Apparently changing the SPC/MSL code to all zeroes is a common part of making these changes, which makes sense in retrospect. cdmaDevTerm tried it as a default action and it just happened to work.

cdmaDevTerm does not support the feature of reprogramming the MEID, but DFS Tool does. That’s when I discovered the second password requirement: an additional 16-digit password. Oh no.

Fortunately, more forum browsing indicated that there is just one of these 16-digit passwords per phone model (not per individual phone like the MSL). The password might possibly change with new software versions for the phone, but still all phones of the same model and software version would have the same passwords. I eventually found 16 Digit Password Issue in 4.1.2 Update – anyone else? which said that the password for my phone with the “Jelly Bean” software version is 2012112120131219. A forum poster said it worked for them on their Epic 4G Touch with Samsung ROM version GB27, which is what I was using.

Success! With that password, I was able to reprogram the MEID in the phone back to the proper one from the phone’s label. The phone activated immediately on Ting, and has been working fine for a week now. A bit of an ordeal, but a satisfying success in the end.

Android Root on Epic 4G

I got a Samsung Galaxy S Epic 4G SPH-D710 (Android smart phone) to use on Ting Mobile, a Sprint MVNO reseller with excellent service and prices. (Get $25 off using my referral code.)

There are a number of methods for getting root access into the phone documented on the Web, because the specific method changed over time during the popular life of the phone. Of course, I bought it for cheap after its useful life expectancy was past, so I’m documenting the final method that applies, as of December 2013.

The final ROM version released by Samsung for this phone is Gingerbread 2.3.6 FC09. Here is how I did it.

  • Reference instructions:
    1. XDA forum post Epic 4g [ROOT][FC09]
    2. Youtube video How to Root the Samsung Epic 4G on FC09 with step-by-step walkthrough.
  • Copy pre-rooted Epic ROM image onto SDCARD: Deodexed-FC09-BML.zip
  • Use Odin3 v1.85 to install ClockworkMod Recovery ROM: cwm-
    • Boot into download: keyboard “1” key plus power button
  • Boot CWM and install the ROM file from SDCARD (Deodexed-FC09-BML.zip)
    • Boot into CWM recovery: volume down key plus camera button plus power button

Ting Notes:
I rooted the phone and even tried out CyanogenMod 10.1 (Android 4.1 Jellybean) before I activated the phone on Ting. Everything worked as expected, playing with Android apps on Wifi.

I was not able to activate the phone on Ting service while it had any variant ROM installed. I had to go back to the stock Samsung FC09 ROM to get activation to work. Ting’s help system says this is common for Android phones. After activation, I was able to use the phone with both FC09 rooted and Cyanogen 10.1 ROMs.

When I tried CyanogenMod 10.1, most features worked consistently, reliably. The Android apps and customization enhancements all worked excellently. Voice calling, SMS text and WIFI all worked with no problems, but mobile data was inconsistent. Usually 3G (slow) would work, while 4G WiMax only worked occaisionally. After a while, 3G, WiMax, and bluetooth all stopped working, for no apparent reason. I was only able to get them working again by returning to stock FC09 ROM.

It is possible that it has something to do with Ting needing settings that vary from the Sprint standard settings.

Air Compressor Tanks

Expansion air tanks and manifold

I don’t have a very big air compressor. Actually, I have two small air compressors, with not very much power or air capacity. I came across two other air tanks, each slightly larger than the tanks on my existing little compressors. So I figured, what better way to make things work, than a Frankenstein agglomeration of miscellaneous parts? Don’t ask why I figure things that way; I don’t know myself.

One of the extra tanks I bought at a garage sale for $20 (which just about blew my whole project budget right there), and the other I got free from my buddy Rex (who got it from Joe, who got it from somebody else tossing it out I think). The basic idea was to feed both compressors into the pair of tanks, all connected together so that the system would have the combined capacity of all parts. As the philosophers say, “the whole is greater than some of the parts” (or some metaphysical mumbo-jumbo like that; I don’t recall exactly).

Tank You Very Much

Both tanks were originally sold as temporary/portable air storage: fill up at a compressor, then take somewhere else to use for inflating tires or basketballs or blowing pinwheels or whatever. They were made to lay horizontally with welded-on feet to keep them from rolling over. They are not quite the same size as each other but are close; each is a little over 2ft / 60cm long and perhaps 12in / 30cm diameter. The freebie tank came without any fittings, while the garage sale tank came with an air pressure gauge and over-pressure relief valve.

I felt the best way to conserve shop space was to stand them up vertically, one above the other. I used my favorite steel fabrication material (scavenged scrounged repurposed bed frame angle iron) to make a tripod frame and and bolted it to the tank handles and feet, so it all stands upright. I also welded on a small 1/4 inch / 6mm thick steel plate to the bottom of each tank (in the new vertical orientation), and drilled and tapped threads into it, for a draincock valve on each tank. I put them off-center to make them easier to reach, and with the rounded tank ends, they become the low point when the whole thing is tipped forward slightly. If that doesn’t make sense, look at the photos or come over to my house and I’ll show you (assuming you’re not one of those creepy strangers from the Internet, of course).

Manifold Greatness

The central connection is a “manifold” with input ports from the compressors, input/output ports to the extra tanks, and one or more final output ports to the air hoses and tools. A manifold is just a pipe or block of metal with multiple ports in it, all connected together, and the ports are just the holes drilled or formed into it. But “manifold” and “port” are much more auspicious sounding names than “pipe” and “hole”, don’t you think? I knew you’d agree.

Dial gauges look cool, and it’s worth keeping the gauge for the geek cred practical troubleshooting value. I can’t imagine how my two little wimpy compressors could overpressure the system (they can barely make 100PSI as it is, chug squeal whine), but safety is always good, so I’ll keep the pressure relief valve too. (Maybe I can figure out how to put a whistle on it; hmm….)

Most compressed air equipment in the U.S. uses the same threaded pipe connections as plumbing pipe, known as National Pipe Tapered (NPT) threads, with pipe sizes named in fractional inches. (Like most things in our last-bastion-of-non-metric-measurement country, these nominal sizes haven’t matched any actual measurements since my grandfather learned to measure pipe diameters by the width of his pinky finger or something like that. Not that I’m bitter about the U.S. measurement system. I learned what a foot and a cup were when I was a toddler, and I still have two feet and a cupboard full of cups, so why would I stop using them now? Really, if a mile and a pound were good enough for the Romans and the Dark Ages, they’re good enough for us too. As Grandpa Simpson said, “My car gets fourty rods to the hogs-head and that’s the way I likes it”. But I digress.) Both air tank openings are 1/2 inch NPT, so it was no problem to make a manifold using off-the-shelf copper pipe plumbing fittings.

First and second generation manifolds
First and second generation manifolds

The first version of the manifold was made of a few copper pipe tees, sweat soldered together. The connections to the two tanks were on the ends of the pipe run, and the inline tees provided the two compressor inputs and one hose output (the gauge and relief valve fitting had one input off its side). The two tanks, having threaded NPT openings, presented something of a dilemma on the best way to connect the manifold piping. I could have soldered the pipe solid and spun the tanks on. That would be entertaining on the first assembly, and a royal pain on all subsequent operations. I could have threaded the fittings into the tanks and then soldered the rest together, but that would also be a pain for later disassembly, plus I might melt the teflon tape or pipe dope on the threads. I chose to use a flare nut connection on the lower tank. The manifold is spun into the top tank threads, and then the flare nut secured on the bottom.

Aluminum cast right on to copper pipe
Aluminum cast right on to copper pipe

The copper pipe manifold worked adequately, but I only made one output, and I realized I wanted two: one straight out of the tank unrestricted, and one with a pressure regulator. Since the manifold needed a change, this was of course the ideal time to make the project more complicated: instead of soldering in another copper tee, I decided to make an aluminum manifold and cast it in-place around a copper pipe. The common air hose and connector fittings use 1/4 inch NPT threads, and the pressure gauge/valve fitting is 1/2 NPT, so I planned for four of the 1/4 NPT and two of the 1/2 NPT openings.

Cast-in copper female
Cast-in copper female

I made a pattern for it with PVC pipe, and made a sand casting. I put a copper pipe right into the sand mold and poured the aluminum around it, hoping it would stick enough to be air tight. I tried two experiments for the 1/2 NPT ports to pre-make the female threads in the casting. For one, I placed a copper female fitting into the sand mold, and cast it in place alongside the central pipe (I packed the copper fitting with green sand to keep it from filling with molten aluminum). For the other, I packed a short steel 1/2 NPT pipe with green sand, and placed it into the sand mold, in an attempt to mold the threads right in the aluminum around the steel. I covered the steel threads with soot first to reduce sticking, and later managed to unscrew the steel pipe from the cooled casting. I ended up using the copper fitting (drilled through the bottom aluminum into the central pipe) for the gauge/relief valve, and left the cast-in threads for “future expansion”. For the 1/4 NPT ports, I just drilled down into the central pipe and tapped them.

Cast-in 1/2 NPT threads
Cast-in 1/2 NPT threads
Tapping 1/4 NPT threads
Tapping 1/4 NPT threads

The Pressure Is On

Soap bubble test
Soap bubble test

I soldered the central pipe to its end fittings for the tanks, plugged up the ports with air connectors, and tried my first pressure test. I tested for leaks by spraying soapy water on everything, looking for bubbles. I got more than I expected. The manifold leaked out each end around the copper pipe. Not only that, it also leaked right out the middle of the casting! Something bubbled up and left some air pockets in the aluminum when it was poured and then cooled. I’ve seen porosity in cast aluminum before, but usually just individual bubbles here and there, not a complete little tunnel.

First pressure test
First pressure test
Porous casting leaking air
Porous casting leaking air

The air leaks around the pipe on each end were interesting also. I didn’t expect the aluminum to fuse with the copper, but I did think it would be gripped tight. That was indeed true; I could not pull the copper pipe from the aluminum casting with any amount of force I had at hand. But it wasn’t quite air tight. I don’t know exactly why, but I know I did not scrub the pipe completely clean or preheat it first. I figure that the hot aluminum hit the cold copper and made it expand slightly, then the aluminum cooled and froze, then the copper cooled and retracted away slightly. It doesn’t take much for air to leak, so that’s my best guess.

Final manifold and pipes, polished
Final manifold and pipes, polished

The good thing about hobby aluminum sand casting is that nothing is ever a total loss; you can always melt down a bad piece and recast it. But in this case I tried patching it first, just to experiment. I have some “Alumiweld” zinc-based brazing rod which actually works pretty well for soldering aluminum, and it worked properly to fill the porous leak in the center of the casting. I did not have any luck using it to seal the ends of the casting around the copper pipe, which I assume is because I couldn’t get the copper clean enough down in the crack. So I cut off the ends of the pipe, and drilled and tapped 1/2 NPT threads. I made a new elbow for the top tank connection by annealing a piece of 1/2-inch copper pipe (heat to red hot with propane torch), bending it to 90 degrees using coil springs inside and out, and sweat soldering it into two male 1/2 NPT copper fittings. I re-used the lower pipe connection, adding a male 1/2 NPT fitting to thread into the bottom of the manifold.

Spray Paint For The Paint Sprayer

Painted inside and out
Painted inside and out

The garage-sale tank was scratched and rusty, and the freebie tank had one or two minor scratches, so they needed a little improvement. I painted them with blue oil paint using my trusty “Critter” siphon spray gun

See “Critter” siphon spray gun at Amazon.com

. I love that thing. Fortunately the little compressor put out enough air for it without these tanks; that could have been and interesting bootstrapping dilemma. The Critter works great to spray the used oil paint I got for $1 from the Habitat For Humanity ReStore. I’m sure it works great with better paints, too; I don’t know, I haven’t tried that yet.

Rex, being a smarty-pants, asked if I had painted the insides of the tanks too, to keep rust at bay. And being just as big a smarty-pants as Rex, I thought hey, why not? He had a great list of B.S. creative ways that the insides could be coated with paint. All of them came down to pouring paint in the hole, rotating and swishing around somehow, and dumping the excess. Which is exactly what I did. I skipped the more creative methods suggested by him (such as the motorized gyroscopic rotational assemblage, or airtank inside giant rubber ball bouncing down a hill), and just held each tank and turned it around and over for a few minutes to swish the paint around inside, then poured out the excess. I let the tanks stand on their ends, to let all the excess paint drip down to the drainage hole. After a day they stopped dripping. Then I picked them up and found I did not have the drainage holes at the very bottom and there was still wet paint pooled inside; guess how I found that out? So I leaned them over a little farther and let them finish dripping for an additional day. That worked.

Once no more paint dripped out, it was simlply a matter of attaching the manifold on to them. I blew air through the tanks, in the manifold and out the draincock valves, for a few hours, to vent out the paint fumes.

Final Assembly

The final assembly consisted of installing the petcock drain valves, and adding the connectors on the manifold. I put two one-way check valves on the inputs of the manifold, so neither compressor can be a leakage point, and added quick-connect fittings for the output side. I did a final soap-bubble leakage test, and everything looked good. Success!

Air purge
Air purge
Manifold greatness
Manifold greatness