NEW PROJECT - 1974 Volkswagen BeetleI was looking through eBay for electric vehicle conversions and first I came across a 911 cabriolet. I bid but didn't win. Then I found a 1974 VW Beetle in Albuquerque, NM which had been converted. It had high end components with a lithium ion battery pack with BMS, a Elcon charger and a Kostov 10" motor. I bought the car and had it shipped to NJ.
Unfortunately, things were not functioning properly. The batteries were GBS 100 ah lithium iron phosphate. Half of them were half dead. I couldn't get them to charge to the same voltage. The pack sagged really badly when accelerating. I spent $1500 on new batteries and still wasn't happy because the cells wouldn't charge properly. The weaker cells would charge first and stop the charging process before everything was fully charged.
|GBS Cells with sense boards in rear compartment|
|Elite Power Solutions BMS display|
|Elite Power Solutions BMS|
|Shop press squeezing GBS cells to fit in pack|
After all that, my brother was using the car and forgot to disconnect the batteries and ran them down. The electronics were set up to constantly draw the main battery pack to keep the DC/DC converter on. This basically killed 1/2 of the batteries that were not replaced. This forced my hand. I was really unhappy with the performance of the GBS cells anyway. I decided to buy another Chevy volt battery pack and reconfigure the electronics. The Elite Power BMS is specific to the GBS cells and would have to be discarded. The charger also wouldn't work with the voltage of the Chevy volt pack so it also can't be used. Luckily the Soliton controller is rated for high voltage. Hopefully we can sell the good GBS cells and the Elcon charger to recoup some of the cost.
As far as BMS, I was hoping to re-use the OEM Chevy Volt BMS. The volt batteries would have to be cut down to fit in the area where the GBS cells were. My preferred configuration is to use the chevy volt pack in two halves paralleled together to make a 180 volt nominal 90 ah pack.
We found a 2015 pack from a salvage yard and had it shipped for $1650 total.
|2015 Chevy Volt battery pack|
|Chevy volt cells taken out of the pack|
|Chevy volt cells cut on tablesaw|
We used 1/8"x5/8" copper bus bar to connect the two rows of battery cells together in parallel. I wanted to prevent corrosion of the contacts so I decided to electroplate the ends of the copper with tin. This is a surprisingly easy process. I first experimented with using electrical lead free solder as the metal. It worked but did not have the right finish. I then ordered pure tin ingot and tried again with a 3.6 volt battery and used some sugar as a brightener and no salt to limit current. This came out really nice.
|First try electroplating with solder|
|Video of electroplating. You can see the metal coating the copper and bubbles of gas.|
|End result after scraping with a wire brush. Not optimal.|
|Bending and twisting copper bus bars with vice|
|Finished product before tinning|
|After electroplating tin plating, look at that shine!|
To be continued ...