Unboxing the Beasts

The Winston Battery cells are expensive. This lot of 8 cost me an eye-watering €4096 which translated into £3540 including 20% VAT 2% credit card payment surcharge, 2.5% currency exchange charge (from VISA as it was in Euros to Pounds) and TNT overland shipping (quite quick at 3 days from Prague).  At least when I put the payment in it was the week when all the Euro countries got their credit ratings downgraded and the Euro slumped against Sterling.

Pretty steep, but actually a lot cheaper than good OPz solar cells.  A quick check on the Tanya battery web site shows "12 OPzV 1400 Sonnenschein A600 Solar Battery" cells of 1,400Ah (C100) would cost £822 each (inc VAT but excluding delivery). That's £9,864 for 12 cells to make an equivalent 24V sealed type of lead acid battery pack that might last 10 years and be usable indoors (not a flooded fork lift type battery).

Even the Deka Solar gel batteries were quoted to me at £250 each - £1,000 for 180Ah (C5).  And they only lasted 850 cycles or 2.5 years (although they were 2nd hand when I got them for £50 each, so I can't complain).

Then there's the problem of weight... the A600 bank of cells weigh 97kg each... 1,164kg in total. By comparison, the Winston Battery cells only weigh 14kg for a total pack weight of 112kg.  Even boxed as a whole pack it would be an easy two-man lift.

Just starting to play around with the video recording on my Samsung Galaxy SII phone. So, here's my first video blog entry for this lithium battery project... Enjoy!

Each cell has a factory date code and serial number printed on it.  All the cells I have are in serial number order from 6288-6295 and were all made in October 2011.

I ordered some cell connecting straps with the cells that come with the A2 grade stainless steel M14 2.0mm pitch thread terminal bolts.  You have to order the straps as the cells don't come with bolts.  The sets also include a stainless steel washer and a spring washer.

I only ordered 7 straps (as that's all you need to connect together 8 cells) but the kit rather unhelpfully doesn't include the two additional bolts you need to make the end plus and minus terminal connections.  So I had to source these from a fastening specialist in the UK (Westfield Fasteners).

I ordered:
2x A2_Screwbolt_HexHd_M14_20_THRfull (M14 x2.0 x 20mm fully threaded hex head set screw bolt)
2x A2_Washer_FormA_M14 (large diameter M14 washer - there are 3 kinds of washer)
2x A2_Washer_SprgSq_M14 (a square profile spring washer)

This was £8.75 delivered.

The cell straps themselves are a bit comedy.  They're made from multiple copper plates that have been stamped out and then tied together with heat shrink tube.

 The other thing I ordered was a Junsi CellLog8 cell logger.  This is a tiny device that is designed specifically for monitoring of multi-cell battery packs.  It can do lead, NiCd, NiMH, and all the various types of lithium cells.

What it does is monitor the individual Voltage of each of up to 8 cells (handy as I've got just that number of cells) and then you can set alarms for over, under, and differential Voltage limits on each cell and the pack as a whole.  It will beep on some / any of these conditions and also drive an open collector transistor output for a relay or whatever (either NO or NC mode).  This is going to be one of the key battery protection elements of my plan.