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Old 09-26-2017, 02:35 AM   #21
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Originally Posted by pengyou View Post
If you can take the leaf's battery apart, can you reconfigure it to be 48v? Just change a lot of the serial circuits into parallel?
Yes, it's more or less that simple. Each module is 4 cells, 2 parallel 2 series. There are 48 modules, or 2 parallel 96 parallel cells in the pack. Nominally 360V, and can put out 500A plus. Wiring the modules somewhere between 6 parallel 8 series, and 8 parallel 6 series will give a pack in the neighborhood of 48V, with a current capacity somewhere in the neighborhood of 3,000 to 4,000A. Good fuses are important ;) 100A to drive a 5kW inverter will be downright boring for the pack.

6 series is technically enough, but at 42-48V it's on the low end. On a lead pack float charge is probably around 56V, and 42V is where some inverters start cutting out. Any voltage sags due to surge current losses could push you into shutdown at lower state of charge. 7 series is probably ideal, but would end up wasting modules as it doesn't divide the 48 modules evenly. 8 series is on the high side at 56 to 64V. Both the inverter/charger and charge controller I'm looking at can be programmed that high though.

Quote:
Originally Posted by Rusty View Post
Rob-

Check out military gensets- diesel and 3-phase. MEP 003 might be good choice. I've got one of those and the bigger MEP 004. Heavy and built for continuos use, unlike disposable BigBox gensets.

Attachment 16103

maybe even a MEP002 5 Kw (underated by 50%)

Attachment 16104
Very cool, thanks for the heads up.

On the totally off the deep end range of options, I do have the Leaf motor sitting in the garage. Which is an 80kW Permenant Magnet AC unit which only weighs 200Lbs..... Assuming I could couple the power it would double as a ~100hp engine retarder. And of course if you can use it in regen, you might as well use it for drive power as well. Now we are talking hybrid Skoolie

Coming back down to earth I did find that most Prestolite/Leece alternators seem to have isolated negative terminals, and they seem to make quite a few 24V models. Some also have adjustable regulators, which could be handy for tuning the voltage to a safe range for the Li pack.
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Old 09-26-2017, 02:42 AM   #22
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Solar Hybrid Electric Skoolie Adventure Begins!

That microturbine though....

In the last video it was just idling at ~45,000 rpm. Here's one running up to 30kW at 95,000 rpm!

https://youtu.be/_-hTEb-nsJw




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Old 09-26-2017, 06:36 AM   #23
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Yes. So to repeat what is said. Each physical block of the leaf battery has two cells in series. At a full charge that is about 8 volt.
The definition of full is more ambiguous then with lead. They are not self regulating as lead that will deal with overcharging by just " boiling" the water away. Lithium will self destruct. You will need better chargers.

3 leaf cell can give 24 volt and 6 give then 48 volt.
The average lead acid battery would be charged with voltages about 15 30 or 60 volt . ( depending on temperature and type..gel or flooded.)

So for a 24 volt system it would be better and safer to use 4 leaf units and for 48 volt 7 or 8 units.

The currents are very high so you want good fuses that can handle the higher DC voltages.

Later j
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Old 11-22-2017, 04:24 PM   #24
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Getting closer to a plan, so here's an update. Some things still in flux, but the basic idea and main equipment selection is getting pretty solid. Leaving out the charging from the bus option at the moment, as still don't have a workable solution. Would be nice for running AC while driving, but if the sun is out the solar should also be producing so maybe its not that critical. Also don't have a specific solution for charging the starter battery off the house batteries, but worst case this can be a bog standard battery charger running off the inverter. Lastly, haven't found an affordable option for a true balancing BMS that I like yet. For now just planning on a basic SOC monitor and cell voltage monitors to give us a heads up if we are getting into trouble.


Note this is still mostly a conceptual drawing, not a real wiring diagram with all components.

I've mostly been hunting for a good deal on panels that are well matched to the controller. I still have to close the deal, but I'm talking to someone local about some new surplus Silevo Triex U300 panels. These are a little bit unusual in that they are a 96 cell panel that is higher voltage / lower current, a bit more power dense (higher efficiency), and a bit squarer than a typical 60 or 72 cell panel. This would allow me to run two strings of 6 panels without exceeding the current input spec on the controller, and hit the max 3600w (60A into 60V) charge capability without exceeding max Voc when cold or getting too low in Vmp at lower illumination.

Here's the result of the string calculator with these panels:


Two strings is nice as I can split them between the front and back of the bus and still get full power out of one sub-array if the other is shaded. The aspect ratio works out pretty well for two length wise rows of 6 panels and still allows enough space to open the roof hatches. Although its a bit heavy, I'm currently just looking at unistrut racking with underside mounts using stainless hardware to avoid steel / aluminum interface issues, just as I did on my home array.





So here's the equipment list so far:

Battery: Nissan Leaf battery modules harvested from a crashed / salvaged Leaf I bought at auction. Currently planning on 8s6p for the rewire for a nominal voltage of 3.75*16 = 60v. Max charge voltage will probably be 4.1V*16 = 65.6v, trying to keep the battery safe, not squeeze every last kWh out of it. With the low voltage cutout set around 3.1v/cell (49.6v) I should get around 15kWh without running out into the extremes where temperature compensation and a proper BMS become critical even with my cells being used and at about 90% of original capacity.
https://insideevs.com/dissecting-leaf-battery-wvideo/

Charge Controller: TS-MPPT-60-600V-48-DB, includes an input disconnect switch, battery breaker, and open internal DIN slots for additional accessories. 48v nominal battery voltage, but can be configured for up to 72V dc output. At the voltage / power of the array I should be running close to 98% charging efficiency.
https://www.morningstarcorp.com/prod...tar-mppt-600v/

Solar Monitor: MS TS Meter-2 600V for direct observation of current performance, plus charge controller will be connected to the system controller via modbus and/or a raspberry pi based monitor via the ethernet port for data logging.
https://www.morningstarcorp.com/prod...-meter-2-600v/

Solar Panels: Silevo Triex U-300, 96 cell 300W, 2 strings of 6s This configuration should maximize the power capability of the charge controller, and allow some shading immunity due to 2 strings without compromising low light performance due to insufficient voltage. Works out pretty nice, as 10 x 77in panels, or 12 x 63-66in panels is about the max we can fit in the area available. The best combinations I was able to come up with for 72 cell 77in panels was ~3150W in one string.
https://www.solarelectricsupply.com/...anel-wholesale

Inverter/Charger: Schneider Conext SW 4048 120/240, can only charge to 64V from grid but accepts up to 67V input for inverter. 120/240v split phase pure sine wave output, 94% efficiency, 3800w continuous, 4400w for 30 minutes, 7000w surge output. Auto AC input transfer switch (30A / 7200w), will output 120v/240v split phase from either 240 or 120v input (nice for 30A/50A shore connection compatibility), and inverter can supplement grid connection ("generator") if load exceeds shore connection capacity. 92% efficiency, 45A charger up to 64v output, will run off either 120v (at half output current) or 240v input.
https://solar.schneider-electric.com.../conext-sw-na/

Inverter Interconnect: Maybe MidNite MNE175SW for Schneider Conext SW for DC battery breaker, current shunt, ac output breaker, ac input breaker.
https://www.wholesalesolar.com/89425...ider-conext-sw

Battery Monitor: Looking at Schneider Conext Battery Monitor for starters. Not a “real” BMS, but seems like it would do the Coulomb counting to estimate SOC, and claims to speak modbus so may be able to talk to the charge controller. May also use cheap Celllogs to monitor/log individual cell voltages since we’re not using balancing. Eventually would like to upgrade to a full fancy balancing BMS and raspberry pi custom system controller.
https://solar.schneider-electric.com...ttery-monitor/
CellLog 8S - ProgressiveRC

System Monitor / Control / Logging: Looking at Schneider Conext System Control Panel and/or Com Box. Seems to have some modus functionality, but not sure how well will integrate with the Morningstar. May have to use a PC or Raspberry Pi to collect data from this and the charge controller via ethernet into a common database / display?
https://solar.schneider-electric.com...conext-combox/
https://solar.schneider-electric.com...rol-panel-scp/

Rob
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Old 11-22-2017, 04:45 PM   #25
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I don't know squat about things electrical...but whatever all that stuff above is sounds mighty expensive.
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Old 11-22-2017, 05:26 PM   #26
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Yeah, this is not exactly a budget build....

We might end up building furniture out of 2x4s and pallet wood and cooking over an open campfire venting through a hole in the roof, but the solar will be magnificent ;)

Rob
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Old 11-22-2017, 05:47 PM   #27
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I wonder how many hp/kw would be needed to keep your basic shoe box going at a steady 60 mph? And if that spare motor has that much oomph? And if you could figure out regen braking? Maybe interpose that motor where your typical retarder goes?
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Old 11-22-2017, 05:56 PM   #28
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This is a high spec build, which should be capable of running almost everything heating, cooling, cooking, hot water, etc off grid almost indefinitely. I am trying to do it as cheaply as possible though.

Panels: Current deal is $2300 for 3600w of those Silevos. Well under retail for those panels, but not stellar as they are somewhat hard to find. These are commercial panels that were not usually meant for the retail market, and of course Silevo has gone out of business (US made). Backup deal is $950 for 3100w of traditional 72 cell panels.

Charge Controller: ~$1300, a bit of a premium to use a higher voltage / higher efficiency model that can also take the Prius high voltage input. Another $100 if we want the remote display/control.

Inverter / Charger: ~$1500, a bit of a premium for the 120v/240v split phase capability, but that is a key to being able to run the highest SEER 240v mini splits. Probably add another couple hundred bucks for the remote system controller or com box.

Battery: luckily free ;) Probably around $3-4k if you had to find and buy a used one.

Likely another $1000-1500 for all the various wiring, mounting, and interconnect hardware. So I'll probably be in the $5-6k range all said and done. Not cheap, but not too shabby for the capacity I think.

Rob
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Old 11-22-2017, 07:05 PM   #29
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Quote:
Originally Posted by dan-fox View Post
I wonder how many hp/kw would be needed to keep your basic shoe box going at a steady 60 mph? And if that spare motor has that much oomph? And if you could figure out regen braking? Maybe interpose that motor where your typical retarder goes?


Believe me I’ve though about it ;). Bottom line is it would be very time consuming and difficult not to impact reliability on something that will be our full time home / transportation. If this was a weekender from a home base I’d probably be all over it.

Ultimately that’s part of the motivation to go as big on solar as possible, so our daily living is as close to zero emissions as possible to make up for the diesel we’ll be sucking down every time we move the bus


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Old 11-22-2017, 10:14 PM   #30
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I guess with that much power you wouldn't need to tilt the panels for maximum harvest, especially at lower US latitudes like Phoenix AZ, but if you drive further north you will lose some potential power, especially in winter when the sun is much lower. I can tilt my panels up to 45 degrees above horizontal, so in winter half of them are at 21 degrees down and the opposite half are raised for better solar harvest.

One other factor to consider is how to keep them clean. Flat panels will get very dirty and dusty very quickly, and then your power production will drop. That was one of several reasons I have all my panels tilted at 21 degrees down when stowed against the roof for driving - rain sluices nicely off them along with any accumulated dust/leaves/etc. And if I need to clean them, I have two quick-connect water outlets on my roof walkway that I can plug my washdown hose into, then it's a simple and safe job to clean the panels. No need to carry heavy buckets of water up onto the roof or drag hoses up there - easy!

However you plan on attaching your panels, you'd better make them VERY secure. Driving down the road at 65 or 70 MPH is the same windload on them as a Cat.1 hurricane, and you will have wind possibly trying to pull the panels up away from the roof. FYI, I have hinged each of my panels' support frames (not the panels themselves) with stainless hinges and multiple stainless bolts to the 6061 walkway, and the walkway is secured through the roof ribs with a total of thirty-six 3/8" stainless bolts and Nylok nuts; the 6061 rails for the panels' stainless lift struts are bolted through the same ribs with another thirty-six 5/16" stainless bolts. I think 72 strong bolts should do the job! Don't underestimate the wind force on the panels.

Like you, I have split my eight 255W panels into two separate strings, each feeding its own TS-MPPT-60 that charges its own bank of four golfcart or L-16 batteries. The battery banks' outputs are combined through two 250A Schottky diodes that prevent one bank back-feeding into the other, then their combined outputs feed the Magnum MS2000 inverter and the DC load center. It's not as fancy as your system, but it's basically quite simple and should work well for a long time. I've even got space left for two solar water-heating panels, each about 20 sq.ft., and they will be hinged and tiltable just like the PV panels.

I just bought two Steca Solsum 6.6F mini charge controllers for float-charging my two Group 31 start batteries during long periods of inactivity. They will be powered directly off my panels, and their output is more than enough to keep the start batteries fully charged, especially the no.1 battery that always keeps the DDEC engine computer alive.

John
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