Saturday, February 18, 2012

...And We're Back On!

And so the initial charging comes to a conclusion (finally!) and it was time to put the battery pack together in its new home, behind the sofa :D

Here's the video.
Not many photos, as I got carried away with video recording each step.

First problem was to fix the M14 cable lugs on the positive and negative battery pack flier leads that would go to the existing M8 stud terminal block.

Without the aid of a £200 industrial crimper to crimp the 120mm2 lug on to the 35mm2 cable, I resorted to using one claw hammer as an anvil and another to beat the sleeve flat on the copper.  I folded the end of the cable over in two, so that it was chunky enough to fit snugly in the sleeve.  Then I used my plumbers Pipemaster soldering iron to heat the sleeve up and silver solder the cable in place to guarantee a good connection.

I also soldered a couple of small wires into the lugs to use for the Smartgauge, the charge controller remote Voltage sensor and the CellLog8s logger.

Then it was just a case of using a bit of fine wet and dry sanding paper to clean off the oxides on the cell terminals and the copper link straps and bolt the thing up.  I held the wrench close to the socket so that it wasn't possible to apply too much force and only really tightened the bolts to the point where the spring washer was sitting flat and gripping the straps.  It's not like this pack will be bouncing down the road in the boot of an electric car, so there's no worry about vibration loosening the terminals.

I was more tense than usual when doing this bolting up.  These cells can muster 2,400A output without really blinking.  A ring or watch strap or 1/2" socket wrench with no insulation on it could make for some impressive fireworks.  Be afraid...  Be very afraid.  It's not the Volts that kill you, it's the Amps.

And so a while later... Actually, a lot later, because my mate James came round for the afternoon, I got round to finishing up the sanding, bolting up and wiring.  Here she is:
And a close up of the terminal block with the addition of the old home made shunt in the negative battery leg (the horseshoe shaped bit of 35mm2 cable).
The shunt is pretty accurate (well good enough to see what's going on) and using an extra 8mm stud gives me the flexibility to change the shunt for something else... Maybe a real shunt for a proper amp-hour counter or just a better home made shunt (now that I have an 80,000 count DVM to calibrate it with).

Just clipped the CellLog8s on the battery pack plus and minus to see what it would do with the full 27V on it.  Tomorrow I'll make up the special 9 pin lead to connect it to the individual cells.

I also programmed the two Morningstar charge controllers with my custom settings for charging this unusual battery bank.  More on that later...

The battery was at a high state of static charge after its initial charge.  It sat at 27.59V with no loads on it yet.  Turning on the inverter and loading it up to 35A briefly, brought the pack Voltage tumbling down to a steady 26.53V.  Releasing the load saw it recover to about 26.75V.  I make that about 6 milli-Ohms for the whole pack, including the cell straps terminal connections!

1 comment:

  1. Pretty funky seeing it just laying behind the couch. Perhaps a nice carpenter in the neighborhood could build you a fancy box? With a clear lid of course to peer. :)