Plan: Off grid solar with a Model S battery pack at the heart

[wycolo]

'MMP' gets tossed around a lot. As far as Magnum, Inc is concerned it apparently is: "mini-magnum panel", so this would presuppose prior knowledge of what a the 'magnum panel' was all about. Does it have a more general meaning?

In any event setting up an off-grid system should be simpler, not cheaper, but certainly simpler to understand and implement than a grid-tied system. And with a Tesla or two acting as an almost unlimited on-site energy dump, the need for expensive storage batteries can be minimized or eliminated entirely. That is with NO household being connected, just the EVs.
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[wk057]

I plan to do some testing to see if the Model S complies with the J1772 protocol and adjusts current up and down as the pilot duty cycle changes on the EVSE.

If it works, I'll be replacing the digital guts of the HPWCs with something smarter so that I can control charging rates as needed to dump power when excess is available, and at rates that make sense.

Anyone know if the Model S will adjust properly in this fashion on J1772? I have a feeling it will adjust downward but not adjust upward :-\

 

[FlasherZ]

I plan to do some testing to see if the Model S complies with the J1772 protocol and adjusts current up and down as the pilot duty cycle changes on the EVSE.

If it works, I'll be replacing the digital guts of the HPWCs with something smarter so that I can control charging rates as needed to dump power when excess is available, and at rates that make sense.

Anyone know if the Model S will adjust properly in this fashion on J1772? I have a feeling it will adjust downward but not adjust upward :-\

I believe it will adjust upward to the maximum configured current for that location on the car. There is a downside, though - you have to be careful not to change the maximum while it is at a lower pilot current, which will keep the maximum at that level (at least on older software versions it did this). For example, at one point I noticed that the car had downshifted its current to 30A, and in an attempt to increase it, I played with the current, setting it down to 25, then back up to 30 where it wouldn't increase any more. When I reconnected the charge cord, the 40A pilot showed up but the car defaulted to 30A for that location.

As I understand it, some have observed different behavior with charging lately, and so experimentation is likely required again to reconfirm.

 

[wk057]

Yeah, I plan on playing around with it, documenting the behavior (likely here) and then writing my software to work accordingly. Preferably I'd like to be able to start and stop the charging and adjust the current completely with my own software. I'd like to be able to do all of that with the EVSE, but I'll settle for utilizing the mobile API for the starting and stopping if needed.

 

[AudubonB]

'MMP' gets tossed around a lot. As far as Magnum, Inc is concerned it apparently is: "mini-magnum panel", so this would presuppose prior knowledge of what a the 'magnum panel' was all about. Does it have a more general meaning?

I'm wondering if someone hadn't meant to write MPP, which is a part of MPPT. Maximum Power Point (Tracking) - adjusting resistance so as to get maximum power as a function of the differing insolation on different PV cells. Any PV array is best served in this age by ensuring the charge controller is an MPPT-setup. And wk057's MidNite controllers are definitely of that ilk.

 

[lolachampcar]

wk,
The OpenEVSE board may be a good place to start I've been using it for a few years now and it has been flawless. The code was reasonably clean as well making it easy to insert your logic.

 

[wk057]

wk,
The OpenEVSE board may be a good place to start I've been using it for a few years now and it has been flawless. The code was reasonably clean as well making it easy to insert your logic.

Yeah, I had whipped up an openEVSE-inspired EVSE for my Volt a while back from scratch. Worked perfectly. Probably will start there again.

 

[bluetinc]

wk057, This info is a couple of years out of date now, but back then I was able to have the EVSE control the start of car charging, stop of car charging, and ramp down the charge current (by changing the pwm %). I wasn't able to have the car ramp the current back up by raising the pwm %, but I'd be very curious what the current software versions on the car do!

Peter

 

[wk057]

... I wasn't able to have the car ramp the current back up by raising the pwm %...

This would be my concern :-\

 

[Fuzzylogic]

They fixed that at software version 5.6 if i remember correctly. Now it works fine.
I made a EVSE that dynamically changes the pwm % depending on the power the rest of our house uses.
And both the Roadster and Model S follow (up and down) the signal the EVSE sends.

Great project btw!!

 

[wk057]

They fixed that at software version 5.6 if i remember correctly. Now it works fine.
I made a EVSE that dynamically changes the pwm % depending on the power the rest of our house uses.
And both the Roadster and Model S follow (up and down) the signal the EVSE sends.

Great project btw!!

This is great news

Thanks

 

[wk057]

Finally finished wiring all of the AC output stuff from the inverters to the distribution block to the transfer switches.

Also finished most of the DC wiring for the charge controllers on the input and output side. Inputs just run to a junction box where they can be tied to the PV stuff later.

(Pics are a little fuzzy because the light for the room is right there by the junction box...)

So... many... wires....

When I'm done with phase 2, I'm going to figure out how many miles of wire I have installed since phase 1, as in miles of single copper conductors. Also going to calculate out the copper weight. Should be fun. Might need to do a betting pool on it or something... lol

 

[Gerardf]

I plan to do some testing to see if the Model S complies with the J1772 protocol and adjusts current up and down as the pilot duty cycle changes on the EVSE.

If it works, I'll be replacing the digital guts of the HPWCs with something smarter so that I can control charging rates as needed to dump power when excess is available, and at rates that make sense.

Anyone know if the Model S will adjust properly in this fashion on J1772? I have a feeling it will adjust downward but not adjust upward :-\

I bought one of the modules developed by FuzzyLogic and actively use his SmartEVSE for almost a year now and I can confirm it works fne. Next to the module it only needs the contactor and a small serial interface module to interface to the currrent sensor(s). In my case 3 sensors in 3 phase mode were the module adapts charge current to the highest current of the three phases. But will also work for single phase. Very elegany solution, surprisingly low costs for the module and other parts. I am very happy with it.

 

[wycolo]

Power Dumping:

Solar panels themselves don't need any load.
MPPT charge controllers - may need a dump load for themselves (minimal?).



Dedicated Solar System for EV charging (off grid):

Charges during sunlight when car finds voltage sufficient for charging.
- EVSE ideally needs to be able to turn itself ON. Manual turn on if necessary.
Stops charging under clouds - car/evse suspends charging. Who is first?
Full sun returns - car/evse resumes charging by itself (?).
Day ends - car/evse cycle OFF - which one is first?


Anyone studied this scenario, perhaps just re power line dropouts? I'm guessing there will be lockouts requiring human intervention at at least one step, in addition to Start of Day turn on. With a 50A 240v Variac I could induce these steps, mimicking a typical solar day's events. Get this to work *before* building the solar system*. Eureka. :smile:

* Might need FuzzyLogic's module(s) here.
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[nwdiver]

MPPT charge controllers - may need a dump load for themselves (minimal?).
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As far as I'm aware MPPT charge controllers don't need any dump load; If they want to lower current to ZERO amps they simply keep raising input voltage until they reach open circuit voltage and current flow stops.

 

[InTheShadows]

As far as I'm aware MPPT charge controllers don't need any dump load; If they want to lower current to ZERO amps they simply keep raising input voltage until they reach open circuit voltage and current flow stops.

Correct. Dump loads are not needed for solar. The newer charge controllers are really smart.

We visited an off grid home we installed a system on this week that had 4 inches of snow on the panels. Went into the basement and the midnite Classic was charging the 48v battery bank with the 43 volts coming from the panels.

 

[nwdiver]

Correct. Dump loads are not needed for solar. The newer charge controllers are really smart.

We visited an off grid home we installed a system on this week that had 4 inches of snow on the panels. Went into the basement and the midnite Classic was charging the 48v battery bank with the 43 volts coming from the panels.

WOW; that's impressive... my 24v MPPT charger controler can't step up voltage. If array voltage < battery voltage it won't work.

I wouldn't say that dump loads aren't needed for solar... It would be useful for my AC coupled system, without a dump load or the grid I have no way to regulate the charge rate for the batteries. That's fine for emergency use a few times a year but it would quickly trash the batteries if I did that everyday.

But I agree there's no benefit if you're using a DC-DC MPPT charge controller.

 

[wk057]

So, made some progress. Since my last update:

• All charge controller wiring is done
  • Output DC wiring to load centers
  • Input DC PV wiring to a junction box for connection in the near future
  • Low voltage communication wiring all done
    • Ethernet for each of the 17 charge controllers
    • Two RJ11 connections per charge controller to daisy chain them for syncing
• All inverter low voltage communication/sync wiring complete (Outback HUB10)
• All AC output wiring from the inverters to the distribution block and transfer switches is complete (pic earlier in the thread)
• All AC input wiring to the inverters from the grid are complete
  • For charging the batteries off of the grid when insufficient solar is available (should be less than 1% of the time)
  • No feeding *into* the grid here (for now anyway, we'll see how much excess I end up with in the summer)
• All inverter load centers ready for DC wiring to the battery bank
• Installed dedicated ethernet switch for the charge controllers and inverter controller for monitoring and easily tying to my network
• Crimped ~50 RJ45 CAT6 ends and ~35 RJ11 ends (hands are sore...)

Still some things to do before I get to the batteries.

Tonight I'm going to install the covers on all of the charge controllers temporarily (will need to remove for inspection probably in a few weeks when everything is done for phase 2) and wire all of the DC +/- bus bars in the load centers to a heavy duty 48V power supply (not isolated, so fed by a small generator).

I plan to fire up each inverter and test functionality individually. Then I will sync them all with their HUB and make sure all of the AC output wiring syncs up properly. I'll then test that AC input pass through syncs up. Hopefully all goes well. I *think* the inverters need a firmware update, but I'm not going to do that while running from a power supply. They won't sync if they are on differing firmwares, so I may hook up a pair of mostly-charged battery modules to power them one at a time and do updates if needed. I don't trust the power supply and generator to not fail during the update process and end up bricking my inverters...

Assuming the inverters check out, I'll start powering on charge controllers without PV input. This should let me configure them all, test that they're connected properly with their LV daisy chain, give them IPs on my network, etc.

When that all goes well, I'll start installation of the large + and - battery bank copper bus bars and completing the inverter load center side of that wiring. Then, I'll run another test, this time feeding the bus bars with my power supply.

After everything checks out it'll finally be time to start installing the battery bank.

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Wired charge controllers without covers.

Charge controllers and some inverters.

Inverters!

Outback HUB10 (inverter sync)

Cheap ethernet switch for all of this equipment.

 

[wycolo]

> MPPT charge controllers don't need any dump load; [nwdiver]

Yet they are there on the diagram you posted. That's why I guessed they may be rather minimal and just for circuit stability.


> Dump loads are not needed for solar. The newer charge controllers are really smart.
We visited an off grid home we installed a system on this week that had 4 inches of snow on the panels. Went into the basement and the midnite Classic was charging the 48v battery bank with the 43 volts coming from the panels. [Theshadows]

Could we have a description of how this neat trick is done? And with a 48v bank what is the nominal or max voltage of the panels setup? Probably an important rule-of-thumb here.
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[InTheShadows]

> MPPT charge controllers don't need any dump load; [nwdiver]

Yet they are there on the diagram you posted. That's why I guessed they may be rather minimal and just for circuit stability.


> Dump loads are not needed for solar. The newer charge controllers are really smart.
We visited an off grid home we installed a system on this week that had 4 inches of snow on the panels. Went into the basement and the midnite Classic was charging the 48v battery bank with the 43 volts coming from the panels. [Theshadows]

Could we have a description of how this neat trick is done? And with a 48v bank what is the nominal or max voltage of the panels setup? Probably an important rule-of-thumb here.
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The 4" of snow did the trick. I did not know the charge controllers could do this (step up). I wish I had taken a picture of it. Below is the voltage setup.