I had a nice adventure recently. You see I have one bad battery out of the Volt pack I acquired. This 48v battery has one cell at 3.62 while all the other cells come in at 3.83.
What to do?
Well. I went to see John. The rocket scientist. He's a tech from back in the day, when Canada's NRC was launching rockets into space.
Beasties
Now he's this pushing 80, fit and full of laughter, single fella with his dog. He supplements his pension by fixing radios. Old radios. Radios the size of apartment fridges with fancy wood cabinets and tubes. Radios so old they were made in places like London Ontario or Utica NY.
So who better to call on to see about this wonky celled battery?
In the meantime I had received my "cell log 8M." This contraption lets me measure 8 of 12 cells at a time.
And it shows I don't have one wonky cell. But 3. Yikes.
It also shows that the cells aren't losing power. They are as stable as all the other cells. It's just that they're exactly .2v lower than the other cells.
Huh?
I won't go on and on with the details
. Suffice it to say that John and I start out with a small constant current power supply. Hooked it up to wonky cell 1 and 2. 7.45v. And set it to 2.5 amps.
Well. Two hours and supper and lawn mowing and ... later. The battery cells had risen from 3.62 to 3.75. A bit more than 1/2 way.
Well this won't do.
So John dusts off the beast. A huge ancient unregulated power supply capable of kicking out 20 amps.
He asks me, do you think the battery can handle it?
Yup I say. Pretty sure. Theoretically I should be able to charge at 45 amps safely. And 135 amps if I'm feeling lucky.
Then he gets out this lovely long piece of plastic. We'll put this .5 ohm load in between the charger and the battery for safety. He says.
You can see it on the table in the photo. It's the long white bar
wrapped with ni-cor wire. Or more commonly known as the wire that your toaster uses to burn your toast.
I'm supressing laughter already when we get all hooked up. Only one sparkle event as the attachment clips are so big. Pieces of wood are found to use to insulate between cells.
Alright says John. Here we go. Click. Nothing. He turns the dial and spins the knob. Nope. Nothing.
A short (heh heh) examination of the beastie reveals that the knob screws are loose. So some tightening goes on. Then, as seen in the pic, the "warning light" falls off.
Now that is funny. And we share a chuckle.
Finally, drum roll please, the switch is flicked. The knob is dialed up. Success. The light on the resistor goes on and the cell log begins to show power climbing in cell 3.
So. Long story short. The charge up of the cells 1, 2 and 3 (according to the cell log) is complete. After 3 days the voltage remains stable. I will try charging the whole battery now. Early impressions are that the battery is stable and the problem lay elsewhere.
Which is great 2.125kw news. The cause of the low cell voltage is a mystery. Bad BMS?
It was a most pleasurable adventure. With drama. Things fixed. Ancient equipment dusted off and put to good service.
Oh. And John shared with me pics from our rocketry program circa 1968. Very cool. There's a good one of him assembling a silver zinc battery. Which he discharged to 0 before charging to the specified voltage (2.something). And used potassium hydroxide for the electrolyte.
Neat.