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Re: Hatched a Tesla

Posted: Tue May 16, 2017 2:10 am
by JoeS
Been on the road again for the past few days, taking a longer scenic route through the Sierras between home and Medford, Oregon. Just returned home, keeping Tesia down to 66mph because I wanted to see just how good my overall mileage would be for the 1101-mile round trip: 283Wh/mile, battery-to-wheels. The highest altitude during this trip was only around 5500ft. I keep the SoC between 80% and 20%, although on the outbound trip up into the mountains I regretted not having charged up higher as we took a scenic detour, but found an unplanned accommodating RV campground with a NEMA 6-50 outlet so still didn't drop below 20%. I got sloppy and didn't do a detailed trip pre-plan with contingencies, and only lined up one RV campground ahead of time as it was critical. Still never ever charged the Tesla to 100%, with lots of conflicting information in the Tesla community about pack balancing.

For those of you wanting to compare long-distance travel to an ICE vehicle, I returned home on Monday doing the 406-mile trip from Medford with three SuperCharger stops at 20 minutes each and one quick rest stop break, and did it in almost exactly eight hours total (including all the stops). Had breakfast at the first charge spot and a snack at the second.

During this trip I picked up a couple of nice used Tesla wheels with almost-new tires at $100 each, so now finally after >25K miles of ownership I have a spare for some peace-of-mind. Now to find an ultra-light jack... I thought of an air bladder jack, but they're expensive. :cry:

Re: Hatched a Tesla

Posted: Tue May 16, 2017 5:24 am
by siai47
I think you should consider charging to 100% at least once a month to let the pack balance. It's the only time it will enter into the balance mode just like the I-MiEV. With the high number of cells in parallel in the Tesla (if I remember something like 74) it is harder to get the pack out of balance due to one or two "lazy" cells. This is unlike the I-MiEV which doesn't have any cells in parallel. The Tesla at 100% charge is very close to 4.2 volts per cell which is far higher charge level than the I-MiEV and with the extra range of the Tesla, there is no reason to go to 100% except for a long trip---or to balance the pack. So, sometime when you are planning a trip, charge to 100%. As the charge is nearing completion, the current will taper off to a very low level. This is the only time the Tesla will balance the pack (applies to the I-MiEV also). The only way you can tell how far the pack is out of balance is by how long the car continues to charge after reaching this lower current level. If the pack is in balance, it may only be there for a few minutes but it could run for a couple of hours if the pack is severely out of balance. It needs to run to completion before disconnecting the EVSE. I used to run at 80% charge limit on the slider but once a month I would go to 100% just to be sure of the balance.

Everyone has an opinion about battery maintenance, however a balanced pack is a happy pack.

Re: Hatched a Tesla

Posted: Tue May 16, 2017 6:48 am
by Aerowhatt
siai47 wrote:Everyone has an opinion about battery maintenance, however a balanced pack is a happy pack.

I agree! A pack should be balanced periodically. Monthly is a good rule of thumb. And since the balancing can't always complete because the highest cell often triggers the end of charging. I think it is a very good practice to do the 100% balance charges in consecutive pairs. Charge to 100% twice (back to back) once a month.

The cells which need pulled up during balancing are the lowest before charging and are getting the most stress when cycling because of this. So without balancing they degrade faster than others. Now, it can be argued that the difference is usually incremental and therefore the stress on those cells is only slightly worse. True perhaps, but it's that way on every cycle, many, many cycles and it adds up. If one thinks of it in the terms, that the lowest cells are already less efficient at cycling. And, then they are subjected to a lower discharge on every cycle (without balancing) it seems like the adding insult to injury.

Plus with the "i" the cells are at different temperatures most all of the time, which significantly compounds the tendency towards imbalance. Tesla really got this right with their battery temperature management system being active and fluid based.


Re: Hatched a Tesla

Posted: Tue May 16, 2017 8:32 am
by JoeS
siai47 and Aerowhatt, I am in complete agreement that cell balancing should be performed periodically.

There are three techniques for cell balancing:

* Top balance (like the i-MiEV)
* Bottom balance (let's not go there)
* Continuous balance

For years I'd been using my PowerLab8 charger (designed for radio-control battery charging) to charge my 2P8S pack on my scooter and my two larger 4P8S Headway (LiFEPO4) packs for my electric outboard and standby power system. The PowerLab8 uses a continuous balancing technique with a wonderful graphic display showing the voltage level of each paralleled cell group, how much current is being bypassed for each cell group, and how it changes over time as the pack is charged. Great multi-colored cellvoltage vs. time graph display on the PC showing how the diverged pack voltages gradually converge during the charging cycle, and this now-single graph continuing to rise to the programmed voltage level (fully selectable) and decaying current over time.

There are some massive threads discussing this topic on the Tesla Motors Club forum, with the leading expert (who disassembled the Tesla pack and performed a whole bunch of measurements) stating that a brick doesn't start balancing until it reaches 93%. I buy that. If anyone is interested in what the Tesla pack looks like, here's the link:

On the other hand, when charging at the various Tesla Service Centers around the country, I've been asking this same question and have been repeatedly told (if the person I was talking to understood the question) by the service people that the Tesla continuously balances the pack, with no need to fully charge it to obtain that benefit.

Like I said, lots of discussion on the TMC forum, with very little brick voltage drift being noted.

For myself, just before my next Tesla trip I do indeed intend to perform a carefully-timed very long slow (using 120vac) charge to 100%, thus ensuring a balanced pack no matter what. First, I'd like to obtain the hardware and software (like CaniOn and LeafSpy) which shows individual brick voltages so I can see what's going on inside.

In the meantime, the Tesla is back in the garage under its cover sitting unplugged at 40%SoC with a float charger hooked onto its 12v battery, while I enjoy driving my i-MiEV around town. Like I said before, best of both worlds!

Re: Hatched a Tesla

Posted: Tue May 16, 2017 11:21 am
by jray3
JoeS wrote: Now to find an ultra-light jack... I thought of an air bladder jack, but they're expensive. :cry:

You might find one cheap on a 4x4 forum. A recent review of a spendy exhaust airbag jack (Car and Driver IIRC) found the wait exhausting and resorted to a traditional mechanical jack.

With low clearance and a lot of flat underbody structure, the TESLA oughtta be well suited to faster airbag action, esp. if your air suspension compressor has an accessory outlet.

Plus, here's an extremely low profile, lightweight jack with great reviews.

Re: Hatched a Tesla

Posted: Tue Jul 11, 2017 1:52 pm
by sandange
Glad you've been enjoying your Tesla Joe and getting some miles down.

i'm getting pretty excited about the model 3 we reserved and been spending some time over on the Model 3 owners club forum.

The subject of recording the total energy required, including vampire loss from idling systems , etc came up.

Since my experience has left me with little faith in MPG on board guages or ratings or EMPG figures.
This reminded me of your wall to wheels approach .

I was wondering if you have recorded your power usage
Wall to Wheels for your M S

So I'll be looking for a kw meter to install before my EVSE to record my consumption. Any meter recommendation?

Re: Hatched a Tesla

Posted: Tue Jul 11, 2017 3:10 pm
by JoeS
Hi sandange, That Model 3 sure looks nice! Anxious to see if it lives up to all our expectations. I have a number of friends who have now bought the BoltEV and really love it...

After realizing the tremendous variability in wall-to-wheels consumption, especially as it's affected by the heater and not just driving efficiency, I've given up tracking that number and simply haven't bothered doing that with the Tesla since so much of my charging is on the road at Superchargers. On the Tesla I have kept my 'Trip B' intact from the day I bought the car when I reset it, so at least I know what my personal lifetime ownership efficiency is battery-to-wheels (hovering around 297Wh/mile overall).

To answer your question, here's the link to my original mechanical wattmeter:

Nowadays there are many more options for monitoring one's home power and energy with WiFi-connected apps. I'd look into these first as manually recording data is a PIA - the granddaddy of the modern ones is TED, but I found it susceptible to noise from other sources. Individual powerline monitors can be easily installed on the line feeding the car.

Regarding vampire losses, Tesla has managed to dramatically reduce the power draw on the 12v battery and I now measure about 400ma going in from my Battery Tender, with the car never waking up any more to recharge that 12v battery. This results in main battery pack SoC not gradually dropping over time. Edit: when I remove the 12v Battery Tender smart float charger, the main battery pack loses about 1%/day simply keeping the 12v battery charged - that's also tough on the 12v AGM, as it is constantly being discharged and then recharged when the dc-dc wakes up.

Re: Hatched a Tesla

Posted: Tue Jul 11, 2017 3:33 pm
by sandange
Thanks for the feed back . I suspected you didn't track the Tesla due to the long distance travel and supercharging involved.
Good point on the meter, I think I'll keep an eye out for a meter that's is more automated .
My brother is out your way and traded his I 3 rex for a Bolt,
loves it so far.

Re: Hatched a Tesla

Posted: Thu Jul 13, 2017 4:30 am
by PV1
I've been spending my time watching the Model 3 sighting threads (people are spotting the test cars all over the place). Elon shared pictures of production #1 the other day. I guess the Handover Party set fot the 28th is going to mostly be specs and details as the reveal, and then hand over keys to ~30 cars.

As for metering, this is the one I use. It measures both 240 volt and 120 volt charging, but it has to have 240 volts to power it (neutral wire bypasses the meter). It's similar to ones meant for sub-metering like in an apartment building (they have similar models that are certified for revenue). It keeps a tally through power outages and has a .00 kWh resolution with an LED that blinks for every 1.25 Wh (800/kWh, why they didn't make it 1,000/kWh is beyond me). ... 5ids.html#

Re: Hatched a Tesla

Posted: Thu Jul 13, 2017 5:33 am
by sandange
Very exciting times for us , anticipating more information, ( final pricing and specs ) as we were line waiters and reserved the M 3 site unseen. We're hoping for delivery date in early 2018
Thanks PV1, the EKM is one I've been looking at, and Teslaliving on the tesla forum has installed.
Still evaluating at this point.