Author Archives: Jay

How I melted my ANOVA Precision cooker

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anova_melted3

anova_melted2

I purchased an ANOVA precision cooker (a Sous-vide immersion heater) via their Kickstarter almost a year ago and have been having fun cooking things in water baths. (It makes cooking salmon so very easy….)

My wife told me about a recipe where you simmer a can of sweetened condensed milk in near boiling water for three hours to make Carmel. After my initial “But won’t it explode?” questions were answered (don’t use a pop top can and you are supposedly explosion safe…) I checked my ANOVA’s manual, and sure enough, it listed the Max temperature at 99 C, perfect for keeping water at a very low simmer without having to keep an eye on the range…[1].

Little did I know, the ANOVA can’t actually take being exposed to steaming water for 3 hours. Continue reading →

Original Pebble Review + Application / Watchface Recommendations

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pebble_jet_black
I finally jumped on the “SmartWatch” bandwagon (after the CST – “World’s Thinest Watch” Kickstarter I’d been waiting on for two years finally gave up the ghost) purchasing a refurbished (Jet Black, original plastic) Pebble for $60 from Meh.com.

I can’t imagine paying $300+ for an Android Wear or apple Smartwatch when you can get the original Pebble’s new on ebay and discount websites for $50-$60. It does everything you really want a smart watch to do, at a fraction of the price.
Built in features I use and love:
Continue reading →

Lines appearing on the display of my Pebble

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pebble_screen_corruption_issue2
My original Pebble smart watch (purchased refurbished) started to have a problem where the display would get corrupted. It mostly only occurred when I was pushing a button to change the display, or when my stopwatch/timer was running (updating the display continuously). For day to day use of just wearing the watch, the screen would be normal much of the time.

I thought at first that something was just corrupted in software, so I removed all of my applications, but that didn’t fix it. Then I reset the watch, and that didn’t fix it. Then I rebooted the watch, and that didn’t fix it. Then I reset the watch to the factory default settings with a super hard reboot and reinstall (removing the custom firmware I had installed), and that didn’t fix it. So, I admitted that it was probably a hardware issue, and found this page on the pebble website that talked about “screen issues”.

pebble_screen_corruption_issue

I’ve found lots of information on the Internet that tells me this is a problem with the internal ribbon/zebra cable connector not staying connected properly.

I found this video that tells how to fix the ribbon/zebra cable connection issue by adding toilet paper in the back of the watch to hold it down.

If you don’t like opening your watch, and trust that it is actually water resistant, I also found this youtube video how to try and fix it by putting it into hot and cold water (but that doesn’t fix it permanently).

Luckily for me, I was apparently still within my 90 day refurbished watch guarantee, and Pebble is swapping out my watch for a replacement, so I don’t need to stuff toilet paper in the back of my watch. If you experience this type of issue you should report it to Pebble quickly. It appears to especially plague early Pebble / Pebble Steel watches, I presume they have changed their manufacturing process to keep it from happening to the later ones.

How to build a 16 volt battery module from six Nissan Leaf cells

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I am building 16 volt batteries using six Nissan Leaf LiIon cell modules. (A Nissan Leaf battery has 48 modules, supplying the construction of 8 of my “batteries”.) My Battery is arranged in a 3P2S (two sets of 3 parallel modules in series), giving a 180 Ah capacity and nominally 16 volts (each module from a Nissan Leaf has 2S2P cells inside, so the module goes up to 8.4 volts maximum at 60AH).

This video (playing at 4x-16x speed) shows all of the work that goes into building a battery. Directions with more information are below.

To build a battery, here are the parts you need:

  • Two end plates, made from steel or plywood.
  • Six nissan Leaf modules, sandwiched between the end plates.
  • Four pieces of threaded rod, 10.5 inches in length, with the following hardware for each rod:
    • Two nuts
    • Two lock washers
    • Two fender washers
  • One 7.5″ x 1″ x 0.25″ copper bus bar (to make the series)
  • Two 3.5″ x 1″ copper bus bars (to join the sense terminals) I used 0.25″ thick so that I could source it from the same copper as the series busbar above, but this is overkill, you could use 0.125 or even smaller.
  • Two 3.5″ x 2.5″ x 0.25″ copper bus bars (to be the + and – terminals of the main battery).
  • 12 M6 bolts (can re-use the ones that came with the leaf modules)
  • 12 M6 Locking washers (I used Belleville Spring lock washers)
  • six M4x16 machine screws for the sense terminal bus bars
  • six M4 locking washers (I used Belleville spring lock washers)
  • three M4x8 machine screws for the BMS terminals + 5 more lock washers
  • Two 5/16th bolts (1″ or 0.75″) for the + and – terminals. (could substitute 1/4″ or metric bolts, I used 5/16th because that is what golf cart batteries use.)
  • (very optional) one more 5/16th bolt for the series bus bar if you want to attach a 5/16 ring terminal from an existing battery monitoring system to each “8 volt” half of your battery.
  • 12×12″ acrylic sheet to laser cut battery cover from.

Continue reading →

Laser cut acrylic terminal covers

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cover_with_bms_topview

I laser cut some covers that place an acrylic wall between each of the busbars of my battery, as well as covering the top. They are designed to keep a falling screwdriver, wrench, or bolt from bridging the bussbars and causing “excitement”. I have a lot of air holes to try and allow a normal amount of air flow, as well as exposing the bolts and screws for occasional tightness checks.

busbar_layout

You can download the textual openscad design file here:
battery_shield.scad

Or, you can just download the PDF files if you want to laser cut them exactly as they are:
battery_shield
battery_shield_reversed

A “how to assemble” video is here:

Youtube Video link

Acrylic could be a bit brittle for this application, and using 3mm craft plywood could provide a bit more impact resistance. However, the covers are inside the “sidewalls”, plus the batteries will be mounted sideways and the current “top” will be mostly protected by insulating foam in my battery boxes,so I chose to go with the less smoky option. (Plus, I think the semi-transparent nature of the acrylic just looks cooler.)

EVSE Install: JuiceBox Pro 40

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JuiceboxInstalled

This is my new J1772 EVSE, a JuiceBox Pro 40 (Amp) unit. Georgia Power is offering a $250 rebate for installing a Level 2 EVSE with dedicated circuit this year. I already had the dedicated NEMA 14-50 (50 Amp) circuit previously installed for electric truck charging, and since the JuiceBox plugs into a NEMA 14-50 outlet, installation was as simple as anchoring it to the brick wall of the garage (with concrete screws) and plugging it in.

I especially like the small plastic cable and “gun end” management system which is screwed to the wall above the JuiceBox. Continue reading →

Leaf battery module differences – 36 “normal” and 12 “special”

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The 2013 Nissan Leaf battery pack that I disassembled had 48 battery modules in it. Previously, I had separated the modules that were in the front half of the pack, packed in stacks of 2 or 4 “flat packed”. However, I had only removed the 24 modules are located in the back of the pack (under the passenger seat) as a unit, and had not unpacked them yet. When I unpacked them, I discovered that 12 of the modules (every other one) had some differences from what I consider to be the “normal” modules (the other 36).

module_differences_mounting_plate4
In the picture above, a “normal” module is at the top, while one of the 12 “special” modules that supports the mounting brackets is on the bottom, with the removed mounting bracket. Note how the tin plate sticks out a little bit more on the “normal” module, taking up the same amount of space as the steel mounting bracket on the “special” module.

The “special” modules have small metal plates that mount to the top and bottom of the modules. These metal plates then bolt into support brackets, which allows this set of 24 modules to be supported “sideways”. I started to worry that these extra pieces of metal would change the spacing of the modules (from my previously measured 1.3333 inches per module), but as it turns out they don’t. The modules themselves are shaped slightly differently (just a bit narrower at the top and bottom) to allow for the extra width of the steel mounting brackets. The main body of the modules should still be compressed to 1.333 inches in size.

Looking inside, the pouch cells extend up past the main body just slightly, so I decided to leave the steel plates on as shims, but cut off the bolts as they would get in the way of my busbars. The bottom of the pouch cells don’t extend appreciably past the main body on the bottom, so I’ll be leaving the bottom steel plates off.

module_differences_mounting_plate3

The metal plates have circular tube like supports that reach inside the holes on the modules, supporting them, and are also spot welded to the thin “tin” outsides of the modules. They can be pried off with a flat bladed screwdriver, popping the spot welds out and leaving small holes in the tin plates.

I just used a cut off blade on an angle grinder to cut off the parts of the brackets that I don’t want hanging out on the top of my battery.
modified_steel_panel
screwtops_cut_off

Battery Bay Plan: Nissan Leaf Cells six group

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SixGroup

This is my current CAD mockup of how I will package a group of six Nissan Leaf modules. I have 48 total modules from a Leaf battery, so I will have eight of them to distribute throughout my truck’s battery bays. I also have a CAD model of that:
batteryBays

Unfortunately, my existing Lead Acid (golf cart battery) bays are not tall enough to mount them vertically, so I am having to lay them sideways. This results in terminals being relatively close together in the two side bays. (I’ll probably slide a sheet of plastic between the two batteries after I get them installed to make it more difficult to drop a wrench down there and short things out. It’s only 32 volts total potential, but a lot of Amps!)

If you would like to know the specifications of a single module (and some people have asked) here is what I know:

From: http://www.electricvehiclewiki.com/?title=Battery_specs
Confirmed by Jay with a 2013 Nissan Leaf module.

lm_width=223; // mm – 8.7795 inches (measured 222 – 8.75 inches)
lm_length = 303; // mm – 11.9291 inches (measured 298.45 or 11.75 inches)
lm_thickness = 34; // mm – 1.3779 inches (measured 34- 1.3333 when compressed)
lm_weight = 3.8; // kGrams, or 8.3775 lbs

The power “bolt blocks” are 20×20 mm in size, and I modeled them around 1 inch in height. But, this height includes the space for a bolt head and a busbar on the top. In the CAD model I made them one inch tall, but in real life they are slightly shorter than that. The “bolt blocks” for the sense terminals in the middle are slightly smaller (18×18 mm) but the same height. So if you download my CAD model (link below) keep in mind that the top of the bolt blocks on the module includes a little extra wiggle room. The CAD software I use is OpenSCAD, which you can download for free. The file itself is human readable text.

BatteryPacks.scad (You may have to rename it from BatteryPacks.scad.txt to BatteryPacks.scad )

Building a battery from Leaf Modules – The Plan

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I am in the process of replacing the twenty (20) six volt lead acid golf cart batteries that power my electric pickup truck with 48 Nissan Leaf battery modules. Because the battery bays in the truck are specificity designed to hold 20 golf cart batteries (and the Leaf modules have a different form factor), it’s not a straight-forward drop in replacement.

My initial design (not showing the compression plates that hold the six modules together in compression):
sixGroup
In the image above, the black bar is negative, Continue reading →