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diy solar

Horsefly's New 160Ah Build

FWIW I use small ceramic fuses (3 amps) for the line that feeds the BMS and contactor; ceramic for the AIC rating. I believe I got them from digikey/mouser/equivalent.
 
Have you looked at McMaster Carr for the bits and pieces, you need rather than Amazon?
They are a premier Industrial supply , I have used them for forty years.
 
Question - why the disconnect before the class-T? I've always been "fuse closest to battery terminal" thinking but you obviously did differently.
 
Have you looked at McMaster Carr for the bits and pieces, you need rather than Amazon?
They are a premier Industrial supply , I have used them for forty years.
I'm aware of McMaster-Carr, and I think I do buy things from them now and then. I buy mostly from Amazon if I can't find something locally, for two reasons: (1) There are several fulfillment centers near me, and as a result much of what I order show up at my door the next day, and (2) I own a fair amount of Amazon stock. ;) Most of the time I've owned it, I've been happy I had it. Today (down about 12%), not so much.
Question - why the disconnect before the class-T? I've always been "fuse closest to battery terminal" thinking but you obviously did differently.
No particular reason why I did what I did, but to me what is important is to fuse before connections to longer runs of wire and any external (to the battery) devices.
 
Just finished my second LiFePO4 battery build. Actually this one is my fourth one, but two the previous two were not for me and so I didn't have as much latitude for the design.

My previous build (discussed here) is for our mountain cabin, and had lots of emphasis on insulation, heating elements and controls for them, and likely unattended operation for months at a time. That was was a 8S 230Ah battery.

This new one is in part just to have it, but also may be hooked in parallel to the cabin battery for heavy usage periods. It also is 8S, but this one is 160Ah cells that I bought from Jenny Wu @ Docan.

Here's a view of the box from the top on the black / negative side. The box made of 3/4" plywood is 20" (51cm) long and 8.5" (22cm) wide, not counting all the stuff mounted on the outside. All-in it weighs 66 lbs (30kg). I can carry it, but I would rather not make a habit of it.
View attachment 91646

I used the JK BMS this time (B2A8S20P). Thanks to other folks on this forum (especially @upnorthandpersonal) the transition after using JBD on the previous 3 builds was easy.


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Here's the red / positive side of the box, including the fuse and disconnect switch, with a 10 ohm, 25 watt pre-charge resistor on the switch:

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Someone else here had suggested using the toolbox liner foam (sorry I don't remember who) so I used that between the cells and on the ends of the pack. On one end I also capped the stack off with a piece of sheet metal, and used four 1/4" x 1" bolts to put just enough compression to keep the cells from shifting around in the box. The bolts are actually not quite finger tight. I'm not a fan of "compression fixtures" so I really just want to restrict movement.

I also topped the box with a 1/8" piece of Lexan to protect the cells from me dropping my wrench across cell terminals.

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I put a 175A Anderson connector on to finish it off. I then have the corresponding 175A connectors on my cabin battery box, my bench power supply (for charging), and the small 24V inverter I have here at home.

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All in all I think it turned out well.
Hi Horsefly, I need some advice. I’m currently making a very similar build to yours (Also got my 160’s from Jenny – Great service!). I'd be very happy if my results looked even half as good as yours. My woodworking skills are considerably worse than my soldering skills ? and I’ve never worked with plywood. I’m concerned about the strength of the bottom of my battery box which I’ve yet to build. I would hate for the bottom to fall out while lugging it around. I’m a tad embarrassed to ask, but how did you attach the bottom to the side walls to the bottom of your box? Biscuit joints, T&G, screwed from the side, Screwed from the underside, Dovetail? …..any comments or advice would be welcome. Thanks.
 
Hi Horsefly, I need some advice. I’m currently making a very similar build to yours (Also got my 160’s from Jenny – Great service!). I'd be very happy if my results looked even half as good as yours. My woodworking skills are considerably worse than my soldering skills ? and I’ve never worked with plywood. I’m concerned about the strength of the bottom of my battery box which I’ve yet to build. I would hate for the bottom to fall out while lugging it around. I’m a tad embarrassed to ask, but how did you attach the bottom to the side walls to the bottom of your box? Biscuit joints, T&G, screwed from the side, Screwed from the underside, Dovetail? …..any comments or advice would be welcome. Thanks.
I'm currently in Europe but will take some more photos and post details when I get back in about a week.

The short story is: no joints, just pocket screws. You can Google pocket screws and get lots of help. I did mine so they are mostly hidden, but a pic of the bottom will tell a story. Pocket screws are pretty easy with a jig, but takes a bit of practice on some scrap wood.
 
Thanks for getting back to me so quickly.....especially while traveling. I'll do my homework on pocket screws in prep for your photos.

Happy travels.
 
Here's the bottom of the box, and you can see the pocket screws.

IMG_20220608_195948897_HDR.jpg

The jig makes it easy to drill the hole at the right angle and to the right depth. I've got two different pocket hole jigs. Can't remember why. I've built a few things now, and they are all rock solid joints. For some I used glue and pocket hole screws, but for some I only used the screws.
 
Here's the bottom of the box, and you can see the pocket screws.

View attachment 97861

The jig makes it easy to drill the hole at the right angle and to the right depth. I've got two different pocket hole jigs. Can't remember why. I've built a few things now, and they are all rock solid joints. For some I used glue and pocket hole screws, but for some I only used the screws.
Thanks for the photo. Having not used pocket screws before, I was curious if you mounted from the walls or from the base (underside or topside) Your photo makes it very clear. (y)
 
Thanks for the photo. Having not used pocket screws before, I was curious if you mounted from the walls or from the base (underside or topside) Your photo makes it very clear. (y)
What you can't see is that there are also screws on the inside of the box, attaching the end pieces to the sides and the bottom. I intentionally put those where the pockets would be hidden by the cells once the box was done. I don't remember for sure now, but I think I put two screws on each end of the bottom into the end piece, and two on each end of both sides.
 
What you can't see is that there are also screws on the inside of the box, attaching the end pieces to the sides and the bottom. I intentionally put those where the pockets would be hidden by the cells once the box was done. I don't remember for sure now, but I think I put two screws on each end of the bottom into the end piece, and two on each end of both sides.
Understood. Probably more the merrier, considering the cells would come in at around 24Kg
 
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