Logged in users > User Diaries

Shunt Equalizer Test.

<< < (4/4)

SparWeb:

--- Quote ---If the intercell connectors are removable is it possible to rewire 7 or 8 to a different position?
--- End quote ---

Photo from a previous installation, but the batteries are stacked in the same order.



There's a thought... I crimp two jumpers, remove the bars from 5-6 and 7-8 and use the jumpers to connect from 5 to 7 and from 6 to 8.

waitatian:
Or balance leads from 6-7 and 5-8?
It would be interesting to know the results if you try a zener/resistor shunt.

SparWeb:
Just for a first try, I did a temporary setup today.  I clamped a single resistor across cell #7 with the tap on the resistor set to about 1 ohm.  A fairly constant 2A was bypassed as a result.  The resistor was on for about 6 hours.  I didn't include the zener because I planned to remove everything.

Very windy all day, and still breezy even now.
Turbine was producing about 10A with peaks 20A when I started.  When finished wind was giving me 5A with peaks 10A.

When I started, string voltage was about 27.2V, and the diversion load was activating fairly frequently when the peaks would push it up to 27.6V.  Inside its insulated case the batteries were warmed up to over 20C (despite it being below zero C outside) so I could categorically say the stack is "full".

The cells 7 through 12 started with readings about 2.28, 2.25, 2.27, 2.27, 2.27, 2.26.  This varies all over the place as the wind fluctuates.
With a load clipped directly across the terminals of cell 7, its voltage dropped immediately to 2.26 and when I came back later it was down a bit more.  Equal to cell 8 in fact.  I removed the resistor and it immediately began to climb back up.  A few minutes later its usual situation was restored.

To have diverted 2A for 6 hours is only 12 amp-hours.  Taken from a cell that has 400 amp-hour nameplate rating this is just a drop in the bucket I realize.  Also at the same time there was at least 3A still passing through cell 7, so in its full state of charge it was still just producing heat.  To have any long-term effect this will have to be installed for a significant period of time.

It's been an opportunity to witness the effect and measure it.  With a zener I could have left it on overnight. 
I'm really tempted to try switching the cells with the jumpers, though.  I've got them ready to try.

SparWeb:
Of course I took a picture.  Soon after clipping the resistor to cell #7.

waitatian:
It looks like 8 has got a bit more charge. If it does pick up condition the bypass current needed to match the two should go down.

Navigation

[0] Message Index

[*] Previous page