While trying to find what looks like an open interlock circuit, I used my cell phone camera to look under the high voltage box behind the Dolphin. Here is the video.

While determining which of these 4 relays performed what functions, I found 2 of them with rusted tabs. This told me that they were plated steel, not brass as so many of these sized relays are. Here is the video of what I found.

I’m working on a USE Prism. It’s previous owner was frustrated after spending years of time and thousands of dollars to try and get it running. Below is the initial video for this electric car project.

The new size of this 18650 module design is 13.0″ x 8.6″. I added another row of cells to make the number of bus bars came out even so one bus bar will fit down each row. This prevents leaving any orphaned cells. Also added fuse wire jumpers and spot welds for detail.

The size of this module is 12.2″ x 8.2″. It holds 150 18650 lithium cells. These are common size of cells in laptop batteries. By making my own module plates, the cost of making the module is greatly reduced compared to these modular cell holders purchased from several sources. Here is the cad file.

Today I opened my first crowd funding request for funds to support my solar project for my camp at BurningMan. Here is the link.


New cylindrical pneumatic vibrator/stimulator design! It has a very linear and repeatable response curve! Frequency range is 45 to 100 hz. Amplitude is also adjustable. Comes with a control unit which can be actuated by a standard DAC module (National Instruments, etc) or any simple 5v source.

Can be purchased through Hybridmojo.com

Today I took this Dolphin water plate cover and cleaned off all of the old epoxy sealer. I’ve scraped off several by hand in the past. The cnc made it an easy chore. Sprayed dust all over the shop. The panel was large enough that I had to do half of it at a time. The tiny remaining epoxy around the perimeter came off with my hand scraper. A few nicks were debured with a flat file. Next silicone sealer gets used to glue it back on. First I need to make sure the tiny flat head screws and holes are ok.

Yesterday Mike Bennett and I worked on a load tester for my nicad pack in my shop. It loads each cell one at a time with around 40 amps. Which is 1C. The goal is to find bad or failing cells when the pack is discharged down to the first drop in pack voltage. This occurs around the 5 mile mark. So I know many cells are croaking at that point.

We bought a 100 amp, 12v lead acid load tester from Harbor Freight for $25 on sale. We ended up using bailing wire as an additional load element. I’ve used bailing wire before for discharging cells. It works fine. It’s a soft wire that when it turns red, it still soft. So it stays consistent. We did some empirical testing to see how much bailing wire we would need to add to get 40 amps at around .6 volts. We came up with two 11″ pieces in parallel. We crimped on 1/4″ yellow lugs and bolted them to the large copper crimps already in the load tester. That worked great!

The meter ranges from 0-16v. As it turns out it was fairly accurate around the .5-1.5 volt range. But that was too small of a needle swing for me. So at a later date I will recalibrate the meter by 10x. It will then read 0-1.6v. Perfect for nicad testing. It has a 51 ohm 1/8 watt resistor across the meter movement. So that needs to be changed to a 470 ohm pot so it can be calibrated nicely.

We load tested a couple of cells continuously to see if the bailing wire would fail. It got hot, but never glowed. So I think the only weak link is the rocker switch moving 40 amps through it. Since having a rocker switch would require 2 hands to operate the load tester, I may very well bypass the switch. Then the load tester can just be rocked only the 2 cell terminals and that will activate the load tester. There are 250 cells to test. So speed is everything!!

This load tester could be tweaked for use on lithium too.

Yin wrote me today to let me know that I saved him $1230 in repair bills on his THS720 scope. He had the same problem that mine had back in 2009. He found this blog with the repair entry through Google. It felt great to hear that my work helped someone else! Then he went and bought my other THS720 scope! Thanks Yin!

Next Page »