Replaced a weak cell

August 21st, 2014

I’ve been wondering why the BMS light will partially light up for the last few months. I’ve been busy, so I didn’t follow up on it.  However, when driving home last week, the BMS alarm went off just before I was about to get on the freeway.  I pulled off to a side-street, and called for a tow truck.  While I was waiting, I started checking batteries, and sure enough – one was sitting at 2.94v, when the others were almost all a 3.3v.

Over the weekend I replaced the battery and now I don’t have the partial warning from the BMS.  (The partial warning is where the BMS warning light just barely glows – it is a standard incandescent bulb. The full warning is when the light is full on and the audible alarm goes off).

DC-DC Converter upgrade

May 31st, 2014

The old DC-DC converter was only producing 12.5v – not adequate for a normal charging system.  After asking around, I ended up buying 2 Meanwell PSP-600-13.5 converters.  These are great little boxes, in that they are designed to work in parallel. This also means that with two boxes, I now have 1200 watts of power to drive whatever I want – such as a new stereo.

The old DC-DC converter.

The old DC-DC converter.


The new DC-DC converters.

The new DC-DC converters.




Charger needs maintenance now

November 17th, 2013

Hmmm, so I got the new 12v battery installed with no trouble.  Plugged it in, and it is now fully charged.

Time to charge the main pack.  I plug in the pack, turn on the charger, and now it is making an odd hissing noise.  I’ve contacted the factory to see what they want me to do.  Meanwhile, the car is not a daily driver at all.  *sigh*

New 12v Battery

November 16th, 2013

Well, the old 12v gel battery has finally died.  I tried a whole day charging it, but nope, wasn’t taking in current.  So I ordered and received a new Odyssey PC925 battery.  I’ll get it charging up today, and should be able to install it tomorrow.

Of course, I still have issues with either a few batteries being soft or some BMS boards being bad.  Not sure which.  I’ll try to determine tomorrow.  Turns out there is a new version of the miniBMS that has a 30 minute memory of good/bad/over/under.  Would be nice to get, but then I’d have to spend another $1500 to do that.  If it turns out that I do have some bad BMS boards, I’ll re-evaluate the whole BMS market.

Cold Batteries

February 28th, 2013

Living in San Diego I didn’t expect to have to deal with cold batteries.  Turns out the CALBs do not like getting under 45F – they really can’t produce the current I need to drive the car – setting off the miniBMS alarm.

I’m working with a machinist to come up with some insulation for the rear pack, and adding some heating to the packs.  Simplest solution is to use plant seedling mats – they heat up whenever the temp drops below 74F.  However, I couldn’t use mats due to the criss-cross of support beams.  Solution:  use soil heating cable.  The cable I bought has a built-in thermostat and can cover up to 10 square feet.  So now, all I’ll have to do is plug in the car each night – something I already do.  :)

So when you design your pack, make sure you add in the heating lines for cold weather, as well as the necessary insulation.

Balancing the Batteries

November 27th, 2012

I was able to replace the failed battery without trouble, however, due to that misbehaving battery, the rest of the batteries were no longer in sync – meaning some had a lot more charge than others.  I tried bringing the new battery down to the rest of the pack level using a 0.4 ohm resistor (50 feet of 16 gauge wire) – doing this for 5 minutes at a time.  It came close, but when charging, the rear half of the pack reached top charge before the top half.

So, after some consultation with battery experts at work, I realized that if I did a REALLY slow charge (2.3A at 110v), then the resistors on the BMS would be able to discharge as fast as I was charging, thus allowing ALL cells to reach that same point.  Please note that I have 108 cells, so I had to do some math.  2.3A * 110v = 253W.  108*3.4 = 367v.  253W / 367v = 0.69A.  So I’m pushing 0.69A through the pack…ok, resistors can handle that…  V = I*R, or I = V / R.  Resistor on the BMS is 4.7 ohm.  3.4 / 4.7 = 0.723A.  Easy.  :)

Bad Battery

November 3rd, 2012

The BMS was complaining about a battery for some time now, but when it got to the point where the complaint was EVERY morning, it was time to find out which one was bad.  This is difficult when there are 108 of them. However, there is a method to finding the bad one:

  1. Drive a few miles to drop all the batteries to normal operational voltage (3.33 for LiFePO4)
  2. Expose all the batteries so you can see the BMS chips
  3. Measure the voltage at all batteries (mark the ones that are low)
  4. Start charging.
  5. Mark the batteries that go into shunt mode first
  6. When charging is done unplug the charger and measure all the batteries.
  7. Wait 1 hour for batteries to settle and again measure voltage.

Quite likely you will have identified the bad battery in step 3, but steps 5 and 6 will clearly confirm this.

What makes a battery go bad?  If the battery is new, then it will fail within a month or less.  If the battery has been in the pack for a while, then it has received some form of trauma (such as a connector flopping on and off or been hit or something like that).

In my case, the battery had a loose connector, which caused one of the bars to bounce on and off the battery.  This is a Bad Thing ™.  To see why, check out this photo:

Bad Battery

New Foot Pedal

July 10th, 2012

Well, the old potbox was severely misbehaving, so I replaced it with a Curtis FP-6.  Very solid, very nice.  Well, it’s kinda big.  But solid.

So, I pulled out the old gas pedal, and tried placing it on the floor.  It sorta worked, but quite awkward to use.  So I took out the old floorboard behind the gas pedal, made a new one I could mount the pedal to, and it is now quite usable.  Especially when the carpet covers the wire and box.

Here’s what it looks like:

New potbox on new footboard.

Gas Gauge Working

July 1st, 2012

It took a while, but I now have an embedded computer listening to the current going in and out of the battery. It is able to calculate the state of charge (SOC) of the pack, and display that value on a LCD screen.  Simple enough, right?  Just took time and shaking rust off some very old skills (wire-wrapping and soldering).  In order to save the life of the auxillary battery, I have two power sources going into the computer.  The battery directly powers the computer, and the keyed +12v drives the display.  I’ll get some photos up later.

Not controller failure after all

June 24th, 2012

The controller is still working – the problem was in the potbox.  Apparently, the cheaper potboxes can have the rheostat inside slip.  Who knew?

I’ve replaced the old potbox with an all-in-one pedal and potbox from Curtis.  Nice solid construction, but I’ll need to work on the position of the box – the cable from the box is currently under my foot – not good.

Controller Failure

June 21st, 2012

Well, I had to get the car towed home yesterday.  Symptoms:  gradual decrease in power until the motor was no longer spinning.  Fortunately, I was in the right-hand lane of the freeway and was able to pull off on an offramp.

Lessons learned:

1) Check the batteries of your test equipment on a regular basis.  My portable voltmeter’s battery was dead.

2) Keep your towing service – you never know when your car is gonna stop working.  AAA was excellent and only took 15 minutes to arrive.

I REALLY hope the controller isn’t dead, as I didn’t want to buy a different controller just yet.  At least I’ve got a lead on a (hopefully) more reliable one.  Nothing solid yet.

New motor uses less power

May 16th, 2012

Neat.  I calculated the power / mile, and got 290 Wh/mile.  That’s less than with the smaller motor (about 300Wh/mile).  Plus, there is no regen, so *IF* I can ever get that to work with this new motor, the power usage will be even better.

Lesson learned:  larger motors can be more efficient than smaller ones.

Picture of the new rear trunk layout

May 9th, 2012

I realized when I posted the pictures of the new radiators and such that I neglected to include a picture of the new controller and wiring layout in the rear trunk.  Hopefully this will satisfy those who are curious.  :)

New controller

Noise, noise everywhere, but no data to be had

April 24th, 2012

Well, I tried two different CANBus sniffers, and there was too much noise on the line for either to work.  I’m going to see if I can isolate the noise (one guess:  the controller), but still not holding out much hope.

On the good news:  I’m in touch with Paul of fame.  They have a beta AC controller designed, and I think I will give it a shot.  Certainly better than nothing.

Update and some Pictures

April 16th, 2012

Ok, car seems to be running ok now.  I have a loose battery connection somewhere that I need to tighten, so that will be my task for the next few nights.

Got the embeded computer installed, and of course, the data coming from the motor is nonsense.  Speed is reported from 0 (although it says 768 at rest) up to 55k RPM.  Temp ranges from 16 to 32K.  So it is obvious that the serial comm is not up to the task.

Since there was a request for a picture of the radiators, here is a picture:


Also a picture of the lousy connectors that I had to replace:

The connector that is circled was smashed during shipment, and the others had wires that would just pop out.

Update on the motor

April 9th, 2012

Ok, so I got the cooling working – had to reseat the pump, as the o-ring has come loose somehow.

So I still have problems with the controller.  However, no way to know what is up without the RS232 hookup.  Well, I spent about 5 hours on Sunday getting the comm to work.  Sort of.  First off, the wires out of the controller are backwards.  Secondly, the controller itself keeps getting confused.

Example:  turn on the controller, listen to the RS232, status is ok.  Spin the motor a bit, and the motor thinks it is in overtemp.  Spin it again, and the overtemp goes away.

Example:  motor speed is a 16-bit value. This value NEVER goes below 762.

Example:  voltage is a 16-bit value. This value ranges from 700 to 20,000.  Never stable.

Next stop is CANBus to see if that is any better.

So far, this controller is rating a C (or maybe C-).  Or for those of the digital persuasion:  4/10.

Oh – and still haven’t gotten regen to work – no clue why not.

Motor works!

April 1st, 2012

So I was right – it was the cracked/cheap/broken connectors to the motor controller.  I replaced all of the connectors on the controller, and the motor now works VERY well.  I really can’t use first gear anymore.

However, I discovered that I mounted the water pump in a bad position.  According to some sites, I’m not supposed to put the inlet of the pump in a vertical position.  Will keep you appraised of that.

Meanwhile, the new motor is just awesome.  Once I get more comfortable with it, I just might burn rubber.  O_O


Motor is running – sort of.

March 23rd, 2012

I took the car for a brief drive up and down the block.  Really sad performance – I need to find out what is wrong, as this is not how it should perform.

Will keep you posted.

More progress

March 17th, 2012

Ok, so the cooling system is all in place now – no leaks.  I’ve got the pump hooked up to run whenever the key is on.  Makes a small gurgle noise, so there is still some air in the system.

Hints:  when installing new hoses, stretch the new hose where it will go over the barbs – makes life a LOT easier for the installer.  Also, make sure the fittings are snug – otherwise, while the hose might be water-tight, the fitting could leak.

I was hoping to bring the car off the jackstands this weekend, but with the rain coming through, it is not very likely.  Really don’t want to mix rain and electrical parts – especially since I haven’t re-installed the rear trunk lid.

I’ll post a picture of the radiators later.

Progress on Motor Adaptor!

March 9th, 2012

Ok, the adaptor is complete, and ready to install.  We’ve made a few attempts to put it in, but had a problem with the spacing around the clutch.  This has been resolved by allowing the pressure plate to move back 0.2″.  During the wait, I’ve rewired the relays, added in a pump and resevoir, and a third brake light.  Hope to have the motor and transmission installed on Sunday.

The brake light is a strip of weatherproof side-facing LEDs from The wires are hidden behind the chrome.

Since both the motor and the controller use liquid cooling, I had to add in a pump and reservoir.  I’ll be running coolant lines from the pump to the controller to the motor to the radiators and back.


Hoist for the motor and transmission.

The new motor is heavy – 98kg! (216lb). So we have to use this hoist to get the motor and transmission into the car.


Motor hanging on a chain

The new motor is significantly larger than the old one.  The gap between the new motor and the battery rack is about 6mm (1/4″).