# My DIY Power Monitor for my DIY Power Well



## Back Pack Hack (Sep 15, 2016)

I've been hankering for another upgrade to my ongoing DIY Power Well project. Yeah, I have a portable 100w folding solar panel now to charge it with, but it would be nice to know how well it truly performs (as well as any other method I can use to charge the batteries).

So a couple weeks ago I ordered a digital meter that can display voltage, current, power (watts) and total energy (kW). I had to wait until I received it before I could determine what I'll need to complete the project. After getting it, taking some measurements and hitting the innernets, the final piece arrived in the mail this morning... the plastic project box. First, I needed to make sure it will all fit in the box.









So after doing some noggin-scratching, I headed to the local hardware store and bought the few pieces I needed to git-er-done.

Display panel and shunt bar are along the top. 2-wire connector, project box, bolts & nuts, nylon bolts and screws for the box are on the bottom.









Now, I normally would use the metal bolts to mount the shunt bar, but that's out of the question as the bolts would then be part of the circuit. If there was any conductive path between the two ends, it would scew the measurements. So I retasked the low-current screws in the bar to mount it with, using the nylon screws.

My first task with the box was to shave off the three nubbins on the bottom so the bar will fit as close to the edge of the box as possible.









This will make it easy for the large bolts to rest against the edge of the box. Eyeballing the small screw holes in the bar, I mark the box and head off to the drill press.


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## Back Pack Hack (Sep 15, 2016)

It's very close to the seam of the two halves of the box, but there's not much I can do about it. The 'bottom' half of the box is going to  have 80% of the hole, the upper half 20%. I figure I can tighten the nylon bolts enough to assemble the box, then give them a bit more to tighten it more securely once it's all assembled.

Now, the nylon screws I bought were much too long for the task as the threads of the holes in the shunt bar don't go all the way through. So, I need to lop off the nylon screws. Using a micrometer, I measure the excess distance between the box and the head of the screw, then transfer that measurement to the other end. A quick lop with my diagonals, and the nylon screws are cut to length, ready to hold the shunt bar in place.









Now the time-consuming and nerve-wracking part; cutting out the square opening for the display panel. I measure once, twice, three times. I eyeball it. Check it again. Double-check it again.









Once I'm 99% sure I've got the box marked so the panel will clear everything, I head off to the drill press again to mil out the opening.









It took a few more trips to the drill press, as well as some fine handwork with a utility knife, but the opening came out square with the box, and all my clearances are met.


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## Back Pack Hack (Sep 15, 2016)

Not to start wiring it. First are the input and output connectors. These are the same connectors I have between my charge controller and the Power Well. I drill a couple holes, thread them through, and use the mounting screw stand-offs and strain reliefs.









Using the wiring diagram on the back of the display, I start making up all the wiring connections, temporary as they are, to make sure it's wired correctly.









Once I check and double-check my connections, I use my benchtop power supply to verify it's all correct.









With the connections correct, I mark all the wires and the two ends of the shunt bar with colored tapes, then make all the permanent connections with a yellow ring terminal. Bolt everything together, put the bar in and snug it in place with the nylon screws, flip the display into place and install the 4 screws.


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## Back Pack Hack (Sep 15, 2016)

OK, it looks pretty.... but does it WORK?

Hook the input back up to the power supply, and my trusty, dusty Fluke 87 to the output, and............









Kinda nice the $24 meter isn't far off my my Fluke!

Time for some finishing touches... including painting the positive terminals red,









as well as labeling the input and output sides.









I did put a label on the bottom with "6.5-100vDC, 25a MAX." on the bottom. Although the shunt bar can handle 100a, the wiring I used won't. So I will limit myself to 25 amps. I doubt I'll ever see that much for my uses anyway.

So here she is, all ready for action:









Now, I know it's not much to look at, but this was still about a 3-hour project. Now whenever I want to, I can install it in line between my solar cells and my battery bank to see how well my Power Well is charging.


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