Snuups

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I also have solar solar on the roof. 30 kWhp. I did not choose the power walls because they are way too expensive. We estimate the cyber truck having a 200 kWh battery. That equals 15 Powerball's. For 120.000 you can buy 2 CTs!

There is no point in buying a powerwall at all.
 

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Couple of thoughts : 1. A home with solar roof experiences moments of surplus production alternated with moments of underproduction (consumption higher than solar production) - just like any EV driving in city traffic or hills/mountains : regenerative breaking vs acceleration. So the argument that using a car's battery as house storage / backup would destroy the AV battery is a bit moot. Manufacturers worried about their battery warranty should simply measure the total amount of charging and discharging in a way that is indicative of the battery's wear and use that a the basis for their warranty.
2. If your car spends most of it's days on the road or on parking lots away from home, it is not too useful as storage / backup for your house. On the other hand, my car is parked at home 95% of the time and it feels silly not to use it for day-to-evening energy shifting.
3. Seems silly to burden the car with the cost and weight of a powerful DC/AC inverter for feeding the house, so that converter should be stationary, using the DC connector of the car for charge/discharge. The stationary part should monitor the house/grid balance and decide when to charge and when to request energy from the EV. The EV of course decided when and how much current to accept or supply to keep the SOC within parameters set by the user (and ultimately the manufacturer).
4. I have 6kW solar on Enphase micro inverters and the Envoy monitoring device shows me exactly my production and consumption and the frequent unbalance between them (both ways). By optimizing my energy consumption, I managed to reach about 50% grid reduction, but the other half is mainly during the evening/night. I will use a "virtual battery" service, basically a savings account for kWh, that fills during summer and empties during winter (I'm at 44 degrees North), but while that stored energy is free to mee, the grid transfer take almost 60% of the normal tariff, so *not* using the virtual battery is still worthwhile, even if it is not enough to invest in a PowerWall or similar. Using 10-15 kWh of the 70+ kWh battery in my future Model Y would suit me well.
 

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Couple of thoughts : 1. A home with solar roof experiences moments of surplus production alternated with moments of underproduction (consumption higher than solar production) - just like any EV driving in city traffic or hills/mountains : regenerative breaking vs acceleration. So the argument that using a car's battery as house storage / backup would destroy the AV battery is a bit moot.
No it isn't. In a previous post I cited the 20% reduction in battery capacity warranted by Tesla for 7 years. Assuming the average 10,000 miles driven per year that means, in a Model X using about 300 Wh/mi, consumption of 7*10000*300 = 2.1E7 round trip watt hours before the battery degrades 20 percent or 20/2.1E7 = 9.5E-7 percent per round trip Wh. I then went on to make some assumptions about what the load leveling demand might be for a reasonable load crest factor and found that it could easily double that round trip energy thus doubling the rate at which the battery ages. Noting that BEV owners really want to minimize that loss of range I opined that many would not want to undertake such a scheme. Those unaware of this potential or using V2G in ways that don't result in this round trip load (i.e. don't use it for load leveling but just occasional backup) might not care.

So no, stating that the car already sends power to and from the battery does not moot the argument any more than claiming that a car that has 200,000 mi on its odometer is as good as one with 2,000 because the car is designed to put miles on the OD. What would moot the argument is a battery that doesn't degrade at 9.5E-7 percent per round trip mile but at a rate an order of magnitude less than that (9.5E-8). Such a battery would degrade not 20% in 7 years of normal driving but only 2% at which level I don't think most people woulds be bothered if using the car battery for load leveling doubled that to 4%, Of course this is the "million mile battery" we are all hoping for.

Seems silly to burden the car with the cost and weight of a powerful DC/AC inverter for feeding the house, so that converter should be stationary, using the DC connector of the car for charge/discharge. The stationary part should monitor the house/grid balance and decide when to charge and when to request energy from the EV.
The rectifier is part of the design of the truck as is. There is also going to be a pretty hefty inverter in the truck perhaps as big as 30 A but, nevertheless, the EVSE (the part external to the truck) will probably be in charge for regulatory reasons and will probably connect to the battery via DC. Thus is would be a bidirectional interface between the battery and the mains. This is not that difficult to implement. Control and monitoring to protect vehicle and grid are where the challenges lie.

The EV of course decided when and how much current to accept or supply to keep the SOC within parameters set by the user (and ultimately the manufacturer).
The car will tell the EVSE how much it wants to charge and the EVSE will tell the car how much it can have. The EVSE will tell the car how much it wants to send to the grid and the car will tell it how much it can have. In short the EVSE will behave like a PowerWall.
 
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Hi ajdelange, thank you for challenging me!
I did some calculations: A car driving in the city might do 0 to 50 to 0 (km/h) every 5 km. If it fully recuperates the kinetic energy, it recharges 50 Wh per cycle. After 100 000 km of city life, that would be a bit over 1 000 kWh or about 4% extra charging (compared to 30 000 kWh normal charging).
For up and downhill, the numbers are more impressive: 2.8 kWh for a 500 meter descend. If a car drives only in the hills/mountains, worst case it runs half the time down, so after 100 000 km, it has descended 50 000 km. For a slope of 5%, that is a vertical distance of 2.500 km, recharging 14 000 kWh or almost 50% extra.
Conclusion: start-stop doesn’t move the needle, but driving in the mountains full time makes a difference.
I get it that manufacturers want to base their warranties on the distance driven, but it would be more meaningful to base the battery warranty on the total charge, maybe counting high speed charging extra.
 

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I'm not really challenging you. Just trying to point out a few things that you might want to think about.

When driving in the city or suburbs the largest load on the battery is the inertial load (acceleration/deceleration) whereas on the freeway, in light traffic and at high speed drag becomes dominant. And, of course, if driving in hilly terrain, the gravitational load becomes large. The following picture shows what happens in a typical metropolitan area drive on both suburban and highway. Note that there is lots and lots of acceleration and deceleration and that current is flowing into the battery quite often. Thus the inertial load is, in this case, doubtless the biggest of the loads.
Drive4.jpeg


But the point isn't that there is extra round trip current from the inertial (and gravittional) loads so much as that using the car battery for load leveling adds appreciably to the round trip current and, with battery technology where it is today, that will age it noticeably faster. This is the first point made in the video which opens this thread. Newer battery technology strives to reduce this sensitivity to round trip current and when batteries are 10 times better in this regard we can stop worrying about that aspect of V2G.
 

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Based on this video there are some questions that need answering

1. tesla semi battery size . with the semi having a possible 1 MWh battery pack for the 500mi range and the cyber truck having the same range in the tri-motor config but not carrying as much weight, so assuming the semi is double stacking the same dimensions as the cyber truck skateboard area for the semi. we maybe looking at a 500 kwh battery pack based on 18650, I am sure the 1 million mile battery is in play here and that's on the new maxwell platform so battery size will shrink but will also grow in capacity. so using the shrink from model S > model 3 pack size of 100 kwh > 72 kwh for the same range (forgetting the weight) you have a 28% reduction but we will use 25% so that 1 MWh is now down to 750 KWh based on 2170 cells but with maxwell dry cell tech we have 20% reduction says we are now at 650 kwh and based on 4 feed lines for a mega charger 162.5 kwh per bank to charge which makes me think cyber truck has a 325 kwh 2 bank system.

2. chargers and sockets
based on the mega charger having 4 feed lines for their 650 kwh pack(estimate) you then have to ask will we see a V4 charger (500kw per line) and 1 extra type of charger called an extreme charger(my idea) between a SuperCharger<>(Extreme Charger)<>Mega Charger. so S/C 1 feed , E/C 2 feeds , M/C 4 feeds. Now since most countries are coming out with the priority tesla charge socket and a type 2 for the model 3 we may see a combo socket on the cybertruck with 2 on board chargers sockets a type 2 and a tesla socket to feed the 2 battery packs.

3. bi-directional charging and V2G(h)
since I have bought up that maybe 2 packs for the cybertruck and tesla not talking about V2G(h) vehicle2grid(home) this may change here with chademo and ccs2 having many companies talking about V2G on these types of interfaces tesla may allow 1 pack to be used as a V2G pack and keep the other pack just for the vehicles driving battery and give a full 1 million mile warranty on this pack and give a 500, 000 mile warranty based on the pack being used for a V2G option because it is using more cycles than just the driving cycles. so i am also assuming that you may have a 1 way battery isolation valve between bank 1 and bank 2 if using a v4 Extreme Charger can give to both banks INWARD only at 500 kw per bank but isolate bank 1 during OUTWARD OPERATIONS (V2G)

4. possible quad motor design
since we have the semi using 4 motors 2 different types for front and rear we may actually see a quad motor cybertruck which in turn offers functions
a) security as long as you have 1 motor you are still moving
b) range extension, if you can use 1 or 2 motors you then less power being used for motors not need powering i.e. going from 4wd > 2wd mode
c)locking hub sync situation, 4 motors 2 different ratios front to rear equals 2 different speeds left<>right and front<>rear
d)model 3 motors with model S plaid motors, the speed from plaid and efficient from 3 or plaid for crawling modes and 3 for range (high speed dirt)

I want peoples thoughts on this
1. am i crazy
2. is it possible
3. am i missing anything
Bidirectional would be great! Should allow use of the full battery in case of sustained grid failure -- the controller would enable you to decide how much to reserve for driving the CT. Tesla would have to sell a suitable controller for that, beyond what's currently available with Powerwalls, since we'd be looking at vastly larger capacity.

As to charging, older long-range versions of Model S had twin chargers, capable of handling 80A/240V sustained -- that's why the original version of Tesla's HPWC is rated for 100A connection, 80A steady-state. So no reason not to do the same again, all the more if the 200KWh (the most likely number, unless Tesla is on the edge of a huge jump in efficiency) battery is partitioned into two 100KWh units. Better use higher current, at least matching the 11.5KW capability of current models. Charging at 23KW (96A) total would require a 120A connection, but could charge the CT from empty to full overnight. Since the new (Gen 3) HPWCs are not so H any more, maxing out at just 48A steady-state, I don't see using two of those for the CT -- cumbersome -- so we would most likely see a new charger, like the Gen 2 HPWC, but more powerful. Whether it would use a different plug is hard to say.

And 200KWh in case of grid failure would power most houses for 5 days in style and for >10 days with only minimal precautions ;-) Plus, you could use it for load-shifting, sending power back to the grid in the evening if your truck is plugged in.

This would be quite easy for Tesla to do, although each utility/state would then determine how you are allowed to use it.
So I don't think you're crazy at all on that -- in fact, I would be disappointed if it's not coming.

No comment on Super/Duper/Mega chargers -- I have never used any and don't expect ever to use one: living on the Big Island of Hawaii with a car that easily does over 350mi on a full charge (first-production LR RWD Model 3, 18" Aero wheels), I can reach anywhere and get back home on one charge and so I charge exclusively at home, using solar panels.

I doubt Tesla will go to 4 motors -- the only rationale would be fully independent computer control of each wheel, which might be great for track racing, but seems like overkill even for racing at Baja ;-) If any vehicle would justify it, it would be the new Roadster. (The Semi is in a class of its own -- it probably really needs 4 motors to get enough torque and power for towing 60'000lbs.)

Given how extremely reliable Tesla motors are, the trimotor version should get you home even after 500K miles of use w/o maintenance ;-) And range extension by reducing the number of motors in play is more cost-effective (and probably more efficient) on the tri- or bi-motor than on a quad-motor -- just use a motor that drives an axle, no need for additional mechanisms. Not sure how much difference it would make: when the AWD LR Model 3 first came out, its range was significantly lower than that of the RWD LR, but by now the reduction seems to be closer to 5% than 10%.
 

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I got solar roof 10 years ago and Powerwalls last year. We have net metering but are paid about 1/3 for power produced and charged full price for power used. Central Hudson really has a scam going! With Powerwalls in the Summer I can charge all day and consume all night and still put a little in the grid. Hence, my summer (J,J,A,S) usage is zero. I am so happy with the Powerwalls...before and after are like night and day! However, even with 4 Powerwalls they only last about 1-2 days if there is an outage or cloudy days.
I don’t really get the advantage of trying to make the CT into home backup. Too little storage to make a difference. Seems better to just let it be a truck and power the house with it’s own batteries. Much simpler and more efficient.
Hawaii is worse: we generate twice what we consume, but we still pay our $30 montly connection fee and get nothing from the utility for the 7-8MWh our PV system generates for them each year. No big deal for us, but this kind of policy discourages wider adoption of PV systems in a state where sunshine is abundant year-round.

The CT battery completely dwarfs Powerwalls: if a CT comes with a 200KWh battery (likely for the trimotor), that's about 15 Powerwall 2s (nominal capacity 13.5KWh) ! So I am not sure what "too little storage to make a difference" refers to; if anything, it's the opposite...
 

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When the idea of V2G first came out, it was thinking about using Hybrids. That way you can leverage the energy density of Gas to turn the car into a generator for the Grid. Escape Hybrid was one being looked at. For a pure EV, IMHO, it's better served as a home generator use only. And the CT can do that. I've found that my Prius can do that nicely, for Ham Radio stuff. I could be in my car all day, doing radio for an event, like say a Marathon; and the car would only run the ICE when the Battery got too low. If instead, I do that with CT, I need to be sure my usage won't leave me stranded at the end of the day.
 

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When the idea of V2G first came out, it was thinking about using Hybrids. That way you can leverage the energy density of Gas to turn the car into a generator for the Grid. Escape Hybrid was one being looked at. For a pure EV, IMHO, it's better served as a home generator use only. And the CT can do that. I've found that my Prius can do that nicely, for Ham Radio stuff. I could be in my car all day, doing radio for an event, like say a Marathon; and the car would only run the ICE when the Battery got too low. If instead, I do that with CT, I need to be sure my usage won't leave me stranded at the end of the day.
The Automatic Cabin Cooling feature on the Model Y will not function when the battery gets to 20% remaining. I suspect it would be easy enough to ensure the 110 and 220 outlets follow the same rule.
 

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Given that the heaviest current Tesla, the X, has a range of 351 miles and a nominally 100 kWh battery its consumption is about 285 Wh/mi. Thus the CT will probably need 400 - 500 implying, with it's 500 mile range, pack capacity of 200 -250 kW.

The rectifier/converter modules Tesla is currently using charge at 11.5 kW meaning at a rate of 23 - 29 miles per hour which is 5 - 6% of a full charge per hour. That's kind of marginal IMO so I wouldn't be surprised if the vehicle had two rectifier/converter units. As the latest version of the HWPC is limited to 11.5 kW that second rectifier will probably have its own separate port as is done in the Semi (as I understand it). As a single 350 kW DC charger would completely fill even a 250 kW battery in less than an hour the second port would not be necessary at a high power SC but as I expect them to be taking this technology from the Semi it will (if it is there at all) probably be usable at a Semi charging station. How would we gain access to those?.

As to V2G - no, I don't think the CT will have it, at least not at first. First I think for many emergency preparedness means having a source of electrical energy that will endure without the grid AND a full tank of gas in case it is necessary to get out of Dodge. Using the truck to power the house obviously wipes out the second requirement. It is possible to meet both with a couple of power walls and solar and, obviously, Tesla would prefer that you buy a Tesla roof, a couple of power walls and a CT than just the CT. This, I think, is the main reason it won't be offered.

Other reasons are that there are regulatory implications in V2G. The current NEC (American electrical code), for example specifically requires that EVSE (equipment that connects the vehicle to premises wiring) have circuitry to prevent back feed from the vehicle. Standards would have to be agreed upon and the glacially slow process of approvals etc. be completed. Might be different in ROW.

Finally there is the issue of round trip current into and out of the battery. Simple calculations based on the current Tesla battery warranty and assuming that the system load leveling threshold was set at 1.5 sigmas show that the battery in the vehicle is "driven" farther in a year by load leveling than by actual use of the car. Tesla owners tend to obsess about loss of battery range and, won't, I don't think, be willing to give it up for this use. And, of course, they would be more willing to do so if the chemical aging rate is reduced to 1/4 or less of what it is now. But that kind of aging rate is currently in the lab - not on the assembly line. Occasional use of the car as a power source as during outages is a different matter. People may want that and if enough do then Tesla will probably offer it (once the regulatory requirements are tamped down).

I won't comment on 4 motors. It isn't going to happen.
“I won't comment on 4 motors. It isn't going to happen.” Isn’t that a comment?😁
 

David R Kirkpatrick

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Given that the heaviest current Tesla, the X, has a range of 351 miles and a nominally 100 kWh battery its consumption is about 285 Wh/mi. Thus the CT will probably need 400 - 500 implying, with it's 500 mile range, pack capacity of 200 -250 kW.

The rectifier/converter modules Tesla is currently using charge at 11.5 kW meaning at a rate of 23 - 29 miles per hour which is 5 - 6% of a full charge per hour. That's kind of marginal IMO so I wouldn't be surprised if the vehicle had two rectifier/converter units. As the latest version of the HWPC is limited to 11.5 kW that second rectifier will probably have its own separate port as is done in the Semi (as I understand it). As a single 350 kW DC charger would completely fill even a 250 kW battery in less than an hour the second port would not be necessary at a high power SC but as I expect them to be taking this technology from the Semi it will (if it is there at all) probably be usable at a Semi charging station. How would we gain access to those?.

As to V2G - no, I don't think the CT will have it, at least not at first. First I think for many emergency preparedness means having a source of electrical energy that will endure without the grid AND a full tank of gas in case it is necessary to get out of Dodge. Using the truck to power the house obviously wipes out the second requirement. It is possible to meet both with a couple of power walls and solar and, obviously, Tesla would prefer that you buy a Tesla roof, a couple of power walls and a CT than just the CT. This, I think, is the main reason it won't be offered.

Other reasons are that there are regulatory implications in V2G. The current NEC (American electrical code), for example specifically requires that EVSE (equipment that connects the vehicle to premises wiring) have circuitry to prevent back feed from the vehicle. Standards would have to be agreed upon and the glacially slow process of approvals etc. be completed. Might be different in ROW.

Finally there is the issue of round trip current into and out of the battery. Simple calculations based on the current Tesla battery warranty and assuming that the system load leveling threshold was set at 1.5 sigmas show that the battery in the vehicle is "driven" farther in a year by load leveling than by actual use of the car. Tesla owners tend to obsess about loss of battery range and, won't, I don't think, be willing to give it up for this use. And, of course, they would be more willing to do so if the chemical aging rate is reduced to 1/4 or less of what it is now. But that kind of aging rate is currently in the lab - not on the assembly line. Occasional use of the car as a power source as during outages is a different matter. People may want that and if enough do then Tesla will probably offer it (once the regulatory requirements are tamped down).

I won't comment on 4 motors. It isn't going to happen.
I completely agree. So many issues: battery degradation, code compliance, recharging. Seems like best to let the truck be a truck, get couple of batteries for your solar system, and if you need emergency power just run an extension cord from the bed!
 

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Sounds like even current Teslas are already equipped for vehicle-to-grid and it can be enabled simply via OTA update.

Per Electrek today:

An engineer involved in a Model 3 teardown shows that Tesla's onboard charger is bi-directional charging-ready. Tesla could enable vehicle-to-grid in 100,000s of vehicles whenever.

Electrek has learned that Tesla has already prepared its onboard vehicle charger for bidirectional charging.

Marco Gaxiola, an electrical engineer who participated in a Model 3 teardown for a Tesla competitor, reverse engineered the electric car’s charger and found it to be ready for bidirectional charging.

He told Electrek:
What I learned on reverse engineering the Model 3 charger, was that the design is fully bidirectional. This means power can be converted from AC to DC the same way as the previous example, but also power can flow in reverse direction, coming from the battery and ending up on the AC side. This is known as DC to AC inverter, and when this technology is present in a vehicle, it is known as V2G (Vehicle to Grid).
Here’s a schematic of the charger that Gaxiola produced as part of the reverse-engineering of the vehicle:

Screen-Shot-2020-05-19-at-1.58.52-PM.jpg



The engineer added about the design of Tesla’s onboard charger:
To complement this, the bidirectional design is replicated 3 times across the same PCB on the Model 3 charger. Another example of redundant design that assures a working process even if one of the circuits fails. Additionally, it is 3 phase design, so it can be used worldwide.
IMG_1152.jpg
IMG_1151.jpg



Gaxiola believes that the vehicle to grid capacity in the Model 3 could be enabled through an over-the-air software update.
 

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What that circuit shows is, from left to right a rectifier (6 transistors), inverter (4 transistors), step up transformer and rectifier (4 transistors) which is capable of turning 1 or 3 phase AC from 120 to 240 volts 400 VDC with all the controls necessary to regulate that output voltage. Do you see any difference between the circuits on either side of the transformer? Each is 4 transistors in a bridge and yet I identified one as an inverter and the other as a rectifier. What makes one an inverter and the other a rectifier? The gating of the transistors. The gating circuitry is not shown nor is the firmware that is required to properly command the gating circuits. While it is true that the circuit as shown could be the basis of a design used to pass power in either direction that's because the rectifying voltage converting regulating features of the circuit require that it use a design which is intrinsically bi directional not be cause bidirectionality is a design requirement. It's like a garden hose required to transfer water from the bib to the sprinkler. Even though that's what its for it can equally well transfer water from the sprinkler to the bib. The gating circuitry is not present (AFAIK) in the current chargers to send power in the reverse direction. Also missing is the hardware and software to manage the required safety, regulation, communications and interface features required for V2G. The "rectifier" module in the current cars is NOT capable of V2G and a software update cannot make it so.

Now there is a place in the cars where bridges do send power in either direction and that's the inverters. When driving DC is converted to AC for the motors. During regen AC is converted to DC to flow back to the battery.
 
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ajdelange

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A couple more comments on the schematic (I nerd-out on such things).

This was the old design for the S and X. It has 3 identical modules and older S and X used to offer the option of having all slots populated (my old X charged at up to 72 A). In the more recent production maximum charging rage is limited to 48 A. Don't know if the current design is still based on 24 A modules but if it is there would only be 2.

The unit in the picture would have circuitry designed to prevent feeding power back to the grid because the version of the code in effect when it was designed required that.

The newer "rectifiers" are more efficient than the old by a couple of percent. I see efficiencies of over 90% in the newer Raven X. So something is changed. I tried to point out in the last post that given the design requirements for a Level 2 charger most people would probably come up with something very close to what is in the schematic. But I do question the use of the first bridge as a rectifier. As those transistors can be switched any time I want them to why not use them as a ring modulator i.e. instead homodyning down to DC and then modulating that onto a 20 or 40 kHz (requiring the inverter) why not just modulate the carrier with the line AC. Instead of a pure sine at the transformer secondary we'd have the carrier (40 kHz) plus an assortment of 60 Hz sidebands but so what? The secondary side rectifier can turn that into DC just as well as it can a single sine. This scheme eliminated the inverter and the attendant losses of its 4 transistors. Someone who really understands this stuff might easily shoot it down but I have been wondering about it.

The place where the circuitry in the schematic (or a modernized version of it perhaps sans the 4 extra transistors) could really be used as an inverter is in the bed power supply. Note that the transformers completely isolate the three modules on A/C side. Each is a 3ø 50 or 60 Hz supply. There is lots of flexibility in how these can be connected to supply 3ø or split phase (which is just 3ø with one of the phases the neutral and the angle between the other two 180 instead of 120 °.) Thus I think the bed power in these trucks is probably going to be at least 30 A per phase and perhaps a bit more. Given all that perhaps the CT charger circuit will be the source for the bed power receptacles.

All speculation of course.
 
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I wonder if thermal management across the secondary is why they use the first bridge as a rectifier. Greater efficiency may be possible if the thermal load could be managed. Perhaps that's the reasoning. Hopefully, the truck will have a lot of usable amperage from the outlets for those times when you want to run a circular saw on your new property... or at least be able to charge up your tools for the day.
 

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