Monday, June 19, 2017

DIY Tin Plating / Electroplating of Copper Bus Bars or Terminals

I was able to tin plate some of the bus bars and connectors for use in my electrical projects. Copper is an excellent conductor, however, copper connections are prone to oxidation and can become high resistance areas in the circuit over time, especially when exposed to the elements. This results in poor performance and possibly failure. Commercial products often use tin plated contacts and connectors to provide corrosion resistance. Tin is a cheap metal that maintains conductivity over time even when exposed to the elements. It covers and protects the copper. Gold plating or silver plating are other options which are more expensive.

Electroplating works by dipping the material to be plated in a solution and running electricity through the solution to move metal to coat the material. To tin plate copper, the positive terminal of the battery is connected to the tin and the negative is connected to the copper. The solution has tin dissolved in it. Sugar is added as a brightener.

Note: Caution must be taken when handling acid and when working with electricity. Wear protective equipment (such as gloves, goggles, respirator, etc. and use care in handling materials. Vapors may be harmful as well so avoid inhaling vapors and only work in an environment with good ventilation.

This is how I did it. Follow at your own risk.

Steps:

Materials: pure tin (ingot or solder), an acid, alligator leads, sugar, a battery, a non-conductive container, and the material to be plated - copper bus bar or connectors.


1. I dissolved some shavings of the tin in muriatic acid (hydrochloric acid). I only used 2 ounces of acid. I let it sit for an hour. It started bubbling immediately. The fumes smelled bad possibly toxic.
2. I added distilled water approx 5 parts to 1 part of the solution from previous step.
3. I Added some sugar to the solution as a brightener. I used about a tablespoon for a 2 cup glass.
4. I Attached the positive terminal of the battery to the tin and placed on one side of a glass container containing the solution. 2 D cell batteries connected is series makes 3 volts.
Positive terminal connected to tin ingot in solution
5. I Placed the copper bus bar into the container (not in contact with the tin). The part that is submerged was to be plated. The copper to be plated has to be perfectly clean - i scrubbed it with a scouring pad and washed with soap and water and avoided handling with my fingers to prevent skin oils.
6. Attached the negative terminal to the copper bus bar using alligator clip leads. Once this was connected, the circuit was complete and electroplating started and noticed bubbles.
video

7. After a couple of minutes, I removed the copper and rinsed it off. Then removed some scale from the plated area. Then plated the area a second time.


Here is the end result, tin plated bus bars
Links to sources of information:

http://transistor-man.com/electroplating_busbar.html
http://hackaday.com/2012/10/14/diy-tin-plating-for-bus-bars/
http://www.sharrettsplating.com/blog/the-tin-plating-process-a-step-by-step-guide/


Re-using Chevy Volt OEM BMS for EV Conversion

I decided to try to use the Chevy Volt BMS to manage the Chevy Volt battery pack used in the VW (Volkswagen) Beetle Electric Vehicle. Since all of the batteries are in one area, connecting the factory BMS harness was simple.
The entire Volt battery pack reconfigured into two rows fit into the area behind the rear seats of the VW. The original BMS units and wiring harness is easily connected. The batteries are strapped together.

The OEM BMS consists of a head unit (K16 Battery Energy Control Module - BECM) connected to multiple slave units (Battery Interface Control Modules - BICM) using the X2 connector, which are directly monitoring the voltage and temperature of the batteries. The units communicate with each other over a CAN network. There is an inductive current sensor and some contractors also connected to the system. The head unit (BECM) controls the balancing functionality and communicates with the vehicle over a separate high speed CAN network on the X1 connector.

A copy of the Chevy Volt Service Manual (PDF) is needed to understand the wiring connections. Here is a link to a thread about the manual. Other copies could be found with an internet search for "2012 Chevrolet Volt Opel Ampera Service Manual".
This is where the BECM is found. It is where the battery control center is and where it is connected to the automobile systems. This needs to be disassembled to remove the BECM.

BMS harness connection X2 to K16 BECM. 
BECM unit K16. The port on the left is X2 connecting to the BMS wiring harness. The port on the right is X1 is connected to power through red and orange and ground through black as shown.

The head unit (K16 BECM) is supplied with 12 volt vehicle power (X1 connector pin 2 RD) and an ignition-on 12 volt signal (X1 connector pin 15 OG/YE).  Ground is connected to pin 1 BK Ground on the X1. It then turns on the slave units (BICM) by creating a regulated 5 volt signal (X2 connector pin 9 GY/RD). This is the bare minimum to turn on the system. The system should manage and balance the batteries as long as it is on. The problem is that I can't tell if it is working or what the status of the cells is without doing additional work to analyze the CAN communication data.

The X1 connector communicates with the vehicle. The CAN communication can be picked up from the X1 connector. On the X1 connector, Pin 3 WH/BK is CAN- and pin 4 L-BU is CAN+. I am hoping that I can analyze the CAN communications using a OBDII USB interface. There are many threads that use Arduino to access/analyze the data. This thread is very informative: http://www.diyelectriccar.com/forums/showthread.php/attempting-hack-chevy-volt-drivetrain-107946.html .

Friday, June 16, 2017

New Project - 1974 VW Beetle previously converted to electric vehicle

NEW PROJECT - 1974 Volkswagen Beetle
I 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
I learned from this experience that it is much easier of all the cells are the same age and have the same characteristics. Too much difference causes the BMS to be unable to balance the cells. It is very difficult to keep adding cells and testing the system until it works properly. Also, these cells are bundled in groups of 4. Every time you change a cell, you have to undo the bundle and recompress them to get them to fit. The cells swell over time and often are not easy to get them back in. We bought a shop press to help squeeze the cells together.
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
Luckily the pack was good. All cells functioning properly and no damage. We went ahead and disassembled it. This is my second chevy volt pack so it took less than an hour.
Chevy volt cells taken out of the pack
We the proceeded to cut them down to rectangular shapes. This involved removing the side portions where the coolant normally circulates. This is dangerous and difficult. It is the only way to fit the cells in the space available. This has been done before, we researched. See project by Kraig Schultz.
Chevy volt cells cut on tablesaw
Once the sides are cut off, there is no way to fasten the cells together since the holes for the threaded rods are also removed. The cells need to be banded together with something. We bought Nifty Products SPSPKIT 252 Piece Polypropylene Portable Strapping Kit, 3000' Length x 1/2" Width Coil, Black from amazon.

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 ...