Battery Vehicle Society

Yeah, we were thinking about the switching, the toaster was only drawing 2.5amps but still. Our main disconnect was pulling the plug on the extension lead and the toaster switch was held closed before we plugged in.
Tim said he could suffer loosing the toaster but not the kettle, I was in general agreement over that as 'the worker' are paid in tea and biscuits not toast and biscuits.

The pack all fits in the back of the van less the cells that are going in the front under the bonnet. They have all been in there so we know it all fits.

I think connecting the pack in the van will be the harder job, crawling around in the back on all those threaded studs with a box of nuts and link bars trying not to drop any, or the spanner.

Oi Tim! This is your thread! Where are you!
I have video posted of me driving my EV tractor.

It all sounds to be going well.

When I had my Bedford CF electric, the replacement sealed lead acid cells were also placed in the load carrying area. To prevent accidental shorting of the links and getting a "belt" from the 216v dc pack I laid a sheet of that double walled polycarbonate roof sheeting across the top of the whole pack, cut to size. It was great because I could continue to use the whole of the load bay and it was exceptionally tough stuff.

John

Night Train wrote:Oi Tim! This is your thread! Where are you!

Thanks for your write-up, photos and videos, Night-Train.

That was a good weekend. On Sunday, after Jon and Night-Train had gone home, Ian and I connected the BMS to the pack.

We weren't sure which way the wires went into the Hall-effect current sensor, so left that out. The cell sensing wire ring tags supplied were too small to go over the posts, so ended up clamped between washer and strap.

My BMS system uses 6 slave modules to monitor up to 10 cells each. The slave looms were fitted, then the slave modules, then the main harness to the central computer.

Switched on the computer and ... low voltage alarm. Zero volts on every cell. What had gone wrong?

Check the voltage on a random cell with a multimeter. Ow! That was hot! No, terminal is cold. Try again. Ow! Pop! That would be the 10 Amp shunt going pop because I had the red meter lead in the wrong hole. Doh! My multimeter is now a voltmeter.

Back to the BMS mystery. Yes, each cell still has 3.3v across it. We haven't destroyed the pack by leaving it connected overnight. Phew! So why no indication on the BMS? Ian wondered if the BMS understood minus voltages, so we carefully disconnected the last 3 cells, then reconnected the last cell the opposite way round. Bingo! 3.33v

When we laid out the cells on Saturday morning it took 2 or 3 goes to get the strap pattern right to connect the end-of-rows without needing wires. In doing this we had ended up with cell 1 as negative and cell 51 as positive. Then when we put the BMS loom on we followed the cell numbering, so all the slave looms were the wrong way around. To correct this, we tried to think of a short-cut, but in the end there was nothing for it but to remove the slave looms and start again. I'm glad we weren't working in the car at this point.

Plugged in the computer only to see "low voltage alarm" again, this time with a pack voltage showing of 160v. Using a different screen on the BMS, I could see that all but 2 cells had 3.3v across them. Looking better We traced the 2 low volt cells and found one badly crimped pin in a slave multiplug, and one cell on which I had got my wires crossed again. I'm really glad the failure mode for reverse connection is not dead short, or I would have had lots of melted wires that day. For installation in the car I intend every sense wire to have a fuse close to the cell terminal, but as this was a trial-run, off the car, only one fuse was fitted in the #51 sense line.

With the bad crimp temporarily pushed back into the plug, and the reversed wires corrected, we now had 168v showing on the BMS screen and no low-voltage warning. Success! It is a peculiarity of this system (but obvious when you think about it) that the pack voltage is calculated by summing the individual cells rather than a check from one end of the pack to the other. So if any of our intermediate fuses blow the BMS still shows full voltage without any continuity. In the trial set-up it would have been useful to take the sense wires the other side of the 5A fusewire, but in reality that will be a 200A fuse and if I blow that I will have other things to worry about than a bad BMS indication.

Many thanks again to Night-Train, Jon and Ian for giving up their weekend to progress this project. Next job will be trying out the balancing charger, checking what indication the BMS gives when the balancing spill loads are switched in. This will have to wait, as I am taking Mary away on holiday next week.

Coming on nicely then by the sounds of it even with the odd butt clenching moments

timpootle wrote:Check the voltage on a random cell with a multimeter. Ow! That was hot! No, terminal is cold. Try again. Ow! Pop! That would be the 10 Amp shunt going pop because I had the red meter lead in the wrong hole. Doh! My multimeter is now a voltmeter..

Ah how many times has that happened to me, although I've always found its the tracks on the PCB that die, I've repaired mine about half a dozen times now and since changing the stock fuse to a 5amp slow blow it now takes the fuse out rather than the tracks, the 15A quick blow just wasnt quick enough I found but then it does depend on the meter and even if it has a fuse, some rely on the PCB tracks

ChrisB

timpootle wrote:

Night Train wrote:Ow! Pop! That would be the 10 Amp shunt going pop because I had the red meter lead in the wrong hole. Doh!

We have all done it. Quite a while ago I managed to vaporise the probes on the multi-meter at work, weld a contactor and blow the 60A fuses on the bus bar. We swore a bit I can tell you.

I am now the proud owner of a couple of clip on DC ammeters, +-100A and +-600A so we can see what the pack is delivering at some point.

*Clamp meter thread moved here :- viewtopic.php?f=3&t=2725 * timpootle

Which BMS are you using?

retepsnikrep wrote:Which BMS are you using?

Sorry Peter, I thought I had mentioned it before.

After much deliberation I went for the Guantuo GTBMS005A-MC16. This system does the undervolt monitoring which I wanted in place before daring to wire the pack up, but does not do cell balancing. For that I intend to use the 'Intelligent charger' which HiPower supplied with the pack, but which only has effect during charging. The charger has no undervolt, overcurrent or temperature sensing.

I was impressed with this system when I saw it installed on Russ Sciville's Elise at the Electrathon last year. He imported it for me, and modified it to be mains powered during charging so as not to load up the DC/DC converter. The touch screen on mine is smaller than the one fitted to Russ' car - he likes mine better!

I have yet to see if the BMS and balancer will play nicely together. There is a lot of spaghetti on top of the pack.

Hi Tim - you got any updates on how your conversion is going?

Slowly! I have hardly touched it since our toasting weekend. Need to get back to it and

• Fill motor with oil
• Refit brushes
• Test charger and balancer
• Fit front battery box
• refit cells into car
• Drive away

However, it won't be this weekend or next as I am going to the Electrathon and then BVS AGM.