e-bike: battery build, part 1 of 3

Started assembling the battery pack.. I might do an Instructables about the process, since I've not been able to find any clear "how to" info online about putting together one of these Headway battery kits.

CAUTION
The batteries come already charged, so keep in mind that you're working with large live sources of electrons.  Be careful!


Tools Required

1. Phillips Screwdriver
2. Work Gloves (the plastic spacer blocks have sharp edges)

Step 1
Get two of the batteries and two of the block spacers.

Step 2
Insert the batteries into one of the spacers, making sure you have one positive end (the shiny silver end with venting holes) up and one negative end (the one with a ring of black lacquer) up.  Note:  Be very careful with the negative end, as if you crack the lacquer the electrolyte will leak.  Don't knock it against anything and do NOT over tighten the screw!

Step 3
Press the other spacer on top of the batteries, making certain that you have the tabbed edge and the slotted edge matching on the top and bottom spacers.  Then slide the tabs of a new spacer into the slots on the bottom spacer, making a space to insert the next pair of batteries.

Step 4
When you insert the next pair of batteries, alternate the positive and negative from the first set.

Step 5
Line up the tabs and slots of the next top spacer and press it down into place.  Gloves are very useful for this, and you can also press on the corners of the spacer using the handle of your screw driver.  Be careful not to damage the batteries.  Don't hammer on anything.. just press until it fits.

Step 6
Add another spacer, two more batteries, alternating the positive and negative.

Step 7
When pressing the top spacer into place you can also flip the pack upside-down and press down, gently, on the whole pack to help press the spacer into place.

Step 8
Keep adding batteries and spacers.

Step 9
Until you're finished putting the batteries together.  I went for a simple vertical stack, but I'm sure you could arrange the batteries into other shapes.  My pack needs to fit into a vertical space on the bike, and a vertical stack keeps things simple.  I like simple. :)

Step 10
Now things get a little more complicated with putting the bridging plates between the batteries.

The idea here is to bridge the cells in series, so that the 3.3v individual cells combine into a 52.8v apx. battery pack.  (16 cells x 3.3v apx. per cell)  Then the Battery Management System (BMS) will convert that into the 48v that my e-bike uses.

To bridge the cells into series, here's the pattern I attached the plates in.  The plates up on top of tea candles are for the top of the battery pack, and the other ones are for the bottom side.

The idea is that I'll connect the positive of a cell at one end of the pack, and the negative of a cell at the other end to the charger when charging pack and to the e-bike when discharging the pack.. well.. with the BMS in there to keep things from running wild and blowing things up.

The pattern of bridging plates inbetween the positive and negative connection points of the pack will complete the circuit by linking the positive and negative ends of the individual cells within the pack.

That's the theory anyway.  Time to attach the bridging plates and see the reality.

Step 11
Remove all of the end cap screws from the top of the battery, and loosely screw on the bridging plates.  I'm not screwing them all the way in as I will need to come back and make some changes later when I hook up the BMS, so just enough to make sure the batteries are securely connected is good enough for now.

Step 12
Now remove the screws from the other side, all except the positive and negative which will be used to connect the battery to the charger & bike.  You can roughly see where each of the metal plates will go.

CAUTION
At this point in the construction the risk of accidentally shorting out two or more of the batteries is very high! Be careful when placing the bridging plates!  I let one slip and it landed between the battery ends, briefly shorting them out, sparking a bit and starting to weld itself in place, before I was able to snatch it back out again.. burning my fingers to do it.

Fortunately the batteries don't appear to have been damaged.  The didn't heat up, nothing has cracked, nothing is leaking, the magic smoke didn't escape.  Whew!

Step 13
As a precaution against accidental shorts, briefly hold one of the bridging plates against the battery ends that you intend to attach it between.  This way you can quickly test that there isn't an unexpected short before you start trying to screw it in place.

Step 14
I decided to screw the plates down, lightly not all the way, one side of the battery pack, and then down the other side, to try and reduce the risk of accidental shorts.

Step 15
Check that the batteries are working in series with a multimeter.  53v is pretty close to what I was expecting, so everything looks good.

The next stage will involve hooking the battery pack up to the BMS and charger so that I can top them up, then I plan to connect the pack up to my e-bike and see how she runs.  First I need to make a trip to Sayal to buy some different connectors from the ones that came with the battery pack kit.  They just seem kind of cheap and I'd rather not rely on them.