Building a NiMh pack

Most producers of NiCd and NiMh cells advise against soldering their cells for two reasons. First you can overheat them when you make them too hot using a light soldering iron. A larger soldering iron lets you use short heating times and less risk of ruining the cells. Secondly, you can clog up the over charge vent which is usually located at the positive pole. When you ovecharge a cell, the battery will get a lot of pressure inside. If that pressure becomes too high, you risk the explosion of the cell. As the casing of the cell is made of metal, it can become a true granade!

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We start off with a 10 cell in line battery pack. They are point welded together, which is more than enough for our applications
Cut the metal plates to length. Do this carefully not to damage the cells. Use your Dremel tools to roughen up the metal plates. If you don't do this the solder will not stick.
Do the same for the positive pole. Note the over charge venting hole here. It is possible that your cells will have venting holes all around the positive pole. You don't need to worry about them as much then.
Use some good electronic solder and at least a 60W soldering iron to put a layer of solder on the positive pole. Make sure not to block the venting hole. It's better to use an 80 watt or 100 watt iron as you risk less to heat up the cell.
Do the same thing with the negative pole.
Get yourself some high quality connectors. For the ECO you need to get a 3mm gold plated kind to coop with the high currents.
Heat up one connector and let the solder flow inside. Don't fill it up completely as you still need room for the wire.
Do the same thing with the other connector.
Cut off 3mm off the insulation of some good quality silicone 2.5 square millimeter wire.
Heat up the copper and let the solder flow in the copper wire. If the copper doesn't flow, the wire isn't hot enough.
Match the right wire with the right connector. Heat up the connector. When the solder starts to flow, insert the wire. Heat up a little more to make sure the wire if firmly attached.
Do the same with the other connector.
Insert the connectors in their housing.
Cut the wires to length making sure the black one reaches the negative pole and the red one the positive pole. Trim off 6mm of the insulation and add solder to the wire.
Do the same thing for the other wire and dry test your wire length.
Put the black wire on the negative pole and heat it up with your soldering iron until the solder melts. Make sure you get a good contact.
Do the same with the positive wire making sure you dont block the venting hole.
Slide the pack in some shrink sleeve. They come in all colors. I used a transparent one.
Use an iron to schrink the ends of the sleeve around the end cells.
Heat up the whole sleeve. Because the ends were done first, the cells will be pulled together and the pack will become pretty solid.
The end result. Now slow charge the first time and go fly!