New owner of Vintage Bus 1980

[freds]

Huh, what?

Ok I plugged the dam thing in!!!

In finishing out the kitchen with running the power inverter for extended periods of time and experimenting with the climate control for the bus with my home automation system. I was severely behind the power curve (aviation term for your just about to hit the ground in a non-survivable manner, unless you get your head out of your @$#, right now...), I managed to flat-line the house battery system. Danger, Danger Will Robinson!!!!



Ok this post is going to cover a lot of ground so it will be broken up into multiple parts.

One of the major challenges is how do you recharge your solar house battery pack when the sun hasn’t been shining for multiple days and you have run it down into the ground?

Just to give an example, I have 3.7KW with ten solar panels that are flat mounted on the roof of my bus.

Given my high latitude (almost in Canada) they are not at the correct angled to harvest the most power.

As an example, a recent day with a bit of mixed sunshine they generated 5.1KW of solar production, however the same panels only generated around 0.1KW of power while it was gloomy rainy day!!!

Prior to getting all ten panels mounted, a couple panels worked almost as good leaned up against the side of the bus pointed at the sun (closer to the correct angle) when the sun appears in soggy Seattle in the winter!!!

Hey, I should be in Arizona this time of the year!!! I am definitely behind schedule right now and can sort of blame it on Covid…

Anyway, as part of a typical solar configuration you generally have:

1. Solar panels
2. Solar charge controllers of which the best is the MPTT types.
3. House battery system
4. Inverter/charger

For the solar charge controllers, I absolutely love, love Victron products, because of the quality of that product line and the free intrinsic cloud data services you get from using their products. (See my sort of fake power production image above)

However, while I am willing to pay a premium for their solar charge controllers, not so much for their inverter/chargers.

Victron is a global company and they fairly much package their product line for that target audience and
this leads to a bit of disconnect in the America market.

In Europe they have three phase power and here in the US most homes have what we call split phase 240V power.

So, Victron’s solution is hey buy three inverters for Europe and two for the US, unless your power needs are low in which case you can buy just one for 120V or 208V power.

Sort of if you want it, just pay for it!!!

In my motorhome I decide to go with a 240V split phase inverter that was compatible with my choice to reuse Tesla car battery modules (could have been the more standard LifePO4 batteries).

Hey, I do own a Tesla Model S P85 in which you are always a couple ounces of foot pressure away from releasing your inter demon (very quietly/civilized, just instant raw acceleration whenever you desire it.) …

So my battery choice was a couple of recycled Tesla battery modules, from some poor sucker who totaled their Tesla...

Given this choice and the technical difference between LifePO4 batteries and Tesla battery modules, my choice narrowed down to a Sigineer inverter/charger; which is a 6KW split phase true sine wave inverter that can surge to 18KW for short time periods. Given this I can fairly much run anything that I would normally run when hooked up to 50AMP service with my motor home/bus conversion while off grid.

Note the Sigineer inverter/charger works with both LifePO4 batteries and Tesla Battery modules, something you can not say for other brands.

Sigineer marketing material indicates that it can cover several applications including RV usage.

However, I do find the Sigineer to be a bit limited in a couple of aspects for RV usage and must consider that it was originally designed to be a UPS device in commercial service. These limitations are:

1. Charger circuitry only works with 240V input source.
2. Inverter/Charger can only do one function at a time.

This works well as a backup UPS power source where when the power returns it bypasses the new power feed to the target load and recharges the battery pack. However, it sucks when you consider a couple of typical scenarios’ that you encounter as a RV’er.

1. Mooch-docking in a friend’s driveway with a simple extension cord.
2. Campground with 30AMP 120V service.

This is where the Victron inverter/chargers really shine in that they allow the 120V though in passthrough mode and do a power assist mode in the case you need to run an air conditioner and microwave at the same time. Where the extra temporary extra power need comes from your house battery bank, without tripping your friend's circuit breaker.

However, a Victron 3KW power inverter costs about the same as a single 6KW split phase Sigineer inverter; where with the Victron product line you would need two inverters to cover the same functionality for your motor home.

So how did I choose to work around this flaw/limitation with the Sigineer product line?

Standby for part two!!!

[freds]

The answer to my dilemma is inexpensive surplus HP server power supplies!!!

HP for over a decade has had standardized redundant power supplies in their server product line.

As these server’s age; they get recycled for new more powerful servers in data centers and then get stripped for parts to sell.

Given this these power supplies get sold for around $20.00 apiece. The primary market for these recycled power supplies is to power GPU’s for Bitcoin miners.

Another is for radio-controlled (RC) hobbyist to power lithium battery charge controllers to charge multiple batteries for model airplanes and helicopters.

One of the limitations of these power supplies is that the 12V output is tied to a common ground so if you want to use multiple power supplies in series for more voltage; you need to convert them to floating ground so they don’t short out when connected together.

The following link gives background and technical details for how you do this by drilling out a couple of ground studs and replacing with them with nylon bolts.

https://www.youtube.com/watch?v=_2QFBE6ZFF0&t=459s

However, when you are talking drilling with electronics, the resulting metal fragments and electricity that run on; doesn’t mix too well; so you must be very, very careful and understand what you are doing!!!!

Back to your solar charge controllers which you will use as a smart interface to your house battery system.

These controllers generally need an input source that is at least a few volts higher than the voltage of your house batteries. Their primary function is to convert power from a higher voltage source down to the house battery voltage. So to reach the voltage level of a typical solar panel you will need multiple supplies.

In my case I have a couple of Victron 150/70 MPPT charge controller which mean they can handle up to 150 volts input and output up to 70 AMP’s out to the 24V house battery bank. (Note I will use four 12V power supplies which I will explain later.)

Given clouds, time of day. The input voltage can vary, hence the advanced (MPPTT) multiple power point tracking functionality of the solar charge controllers.

Ok, how do you process these multiple power supplies to floating ground without drilling them as it shows in the video?

I came up with a much simple procedure using a rivnut tool, so it only takes about five minutes for each power supply conversion without the need to do any drilling!!!

More to come and hey I am spending a lot more time describing this to you, than it actually took to do!!!

[freds]

Here's my simpler no drill method of converting HP server power supplies to floating ground operation.

Steps:

1. Remove the top off of the power supply (four Phillip's head screws).
2. At the back of the power supply remove the two circuit board mounting/case grounding screws.
3. Turn the power supply over and screw the rivnut tool shank through a drill stop ring and pull the nut stud out of the case for both screws.
4. Replace the original metal screws with nylon parts and put the top back on the power supply.

Nylon parts that I used:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

Though when I do it again, I may just use the spacer and some hot glue as the head of the nylon bolt sticks out too much.



The rivnut tool that can handle the small metric screw size that is used in the power supply is:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

And after we have removed the embedded nut that acted as the grounding post.




Generally on an RV you wire up all your solar panels in parallel so if one panel is shaded it doesn't affect other panels.

Each panel includes a DC blocking diode as part of it's construction so that current can only flow one way.



In our world a battery isolator performs the same functionality as it has DC blocking diodes as part of it's construction. Though they are more higher amperage then a typical solar panel diode.



In the above picture you see the metal bracket that I bent up to mount my four converted HP power supplies to the roof of my battery bay.

The power supplies are wired in series and the output runs to a battery isolator which is then wired in parallel with the solar panels on the roof of my bus. I selected the solar charge controller that had the fewest panels connected to it.

The reason that I used four power supplies is to have a higher total voltage then my solar panels put out. By using the battery isolator the charge controller will see whichever device is producing the most power.

A quick note about these power supplies their maximum output is 900watts on 120volts and 1200watts when fed 240V.

The maximum power that you can draw from a 120v circuit is around 1800 watts.

Both the HP power supplies and the solar charge controllers are about 90% efficient.

My solar charge controller output is 70AMP's at 24 volts which is 1680 watts. However back to the efficacy of both devices we talking an input power requirement of over 2000 watts to deliver that much power, which will trip either a circuit breaker or overheat the extension cord.

There is also another rule that should be paid attention too; is that for continuous loads you should not draw more than 80 percent of available power. This works out to an extension cord load of around 1440 watts.

So after working all these numbers I changed the maximum amperage on the solar charge controller from 70 amps to 50 amps. Which is about a 1200 watt charge rate to the batteries.

I purchase my HP power supplies from eBay.

https://www.ebay.com/itm/DPS-1200FB-...72.m2749.l2649

I also purchased adapter boards that fake the power supply into automatically turning on and breaks out the DC voltage to a terminal strip, as this greatly simplified the conversion process that was in the original video that I gave a link too.

https://www.ebay.com/itm/DPS-1200-12...72.m2749.l2649

Note the terminal screws on this boards terminal strip are small; so use multiple (fine wire flexible) wires to carry the load.

[Joe Camper]

Explain what uve built in another way. Based on early results, in your opinion, once u get way down south and head out into the wide open spaces of a spot like Quartzsite. Im assuming spring and fall were bigger constant HVAC loads aren't nessessary im thinking u could go indefinatly without supplementing the panels for power.? Yes?

Next question. If heat is needed at night or AC during the day in your estimation how many hours a day do u think u could support an air conditioner or heater and still not need to supplement the panels on the average mostly sunny day? 2 or 3 hr or will it be more or less?

I know when I'm in the infield at the race track living off inverter I need about 4 hr of gen time when I'm not needing HVAC and I go 2 in the morn and 2 in the evening resulting in about 10bucks a day in fuel. Not counting the inverters or batts or hardware that we all already have but just the panels and charging controllers how much did u put into just those items?

Possibly a ridiculous question. In intense boondocking circles do u know if there r portable wind generators out there that have any value?

[Gil_J]

More great info! A 2 alternator, one battery battery isolator would be perfect, if you want to use diodes. A better option might be an automatic charge relay. High current and NO Voltage loss, like a diode.

[freds]

Here's a block diagram of the installation that I just performed on my bus:



As I mentioned in my previous post these power supplies can produce 1200 watts if fed a diet of 240 volts!!!

So I will be adding another set of power supplies that are driven from my diesel generator, so in this instance the block diagram would be:



Ultimately I will have an automation that will go hey it's 7PM, how's the state of charge for the house batteries? Hey it's a little low, need to run the generator for 20 minutes...

I also found a service where you give it your geographic coordinates and it will predict your solar production for the day, based on the weather forecast and cloud based AI that uses the latest cubesat imaging.

[freds]

Explain what uve built in another way. Based on early results, in your opinion, once u get way down south and head out into the wide open spaces of a spot like Quartzsite. Im assuming spring and fall were bigger constant HVAC loads aren't nessessary im thinking u could go indefinatly without supplementing the panels for power.? Yes?

Next question. If heat is needed at night or AC during the day in your estimation how many hours a day do u think u could support an air conditioner or heater and still not need to supplement the panels on the average mostly sunny day? 2 or 3 hr or will it be more or less?

I know when I'm in the infield at the race track living off inverter I need about 4 hr of gen time when I'm not needing HVAC and I go 2 in the morn and 2 in the evening resulting in about 10bucks a day in fuel. Not counting the inverters or batts or hardware that we all already have but just the panels and charging controllers how much did u put into just those items?

Possibly a ridiculous question. In intense boondocking circles do u know if there r portable wind generators out there that have any value?

Hi Joe

Yes boondocking in Quartzsite I should not need to run the generator at all. If the batteries are totally empty I shouldn't have to run the generator for more than a couple of hours.

I really haven't seen any good feedback out there for using windmills for power production in our typical scenario's.

[freds]

Next question. If heat is needed at night or AC during the day in your estimation how many hours a day do u think u could support an air conditioner or heater and still not need to supplement the panels on the average mostly sunny day? 2 or 3 hr or will it be more or less?

I know when I'm in the infield at the race track living off inverter I need about 4 hr of gen time when I'm not needing HVAC and I go 2 in the morn and 2 in the evening resulting in about 10bucks a day in fuel. Not counting the inverters or batts or hardware that we all already have but just the panels and charging controllers how much did u put into just those items?

Hi Joe

I just realized I didn't answer all your questions...

My Tesla house battery pack if fully charged holds around 10.4KW of power, however for the longest life you generally charge to only an 80% power level so around 8KW of storage though I can elect now and then to go to a full charge.

The biggest draws are my air conditioners and when they are running flat out they draw around 2400 watts, so around three hours at that consumption level. I have no experience yet with what their duty cycle would be at say 80-90 degrees, so at this time guessing longer. During the night I could elect to just run the air conditioner that services the bedroom.

My outlay for the solar panels and solar charge controllers has been, oh shit you made me add everything up!!!

Solar panels                          $1700.00
Victron Charge controllers            $1800.00
Victron Color control computer         $510.00
Victron 24V to 12V 70 AMP converter    $141.00
Victron 24V Isolated 20 AMP DC charger $165.00
2 Tesla battery modules               $2200.00
SimpBMS for Tesla battery modules      $800.00
Signineer 6KW inverter                $1200.00
==============================================
Total                                $8,516.00

Actually this isn't bad, just 8KW of Battle Born batteries would have been close to the same amount.

DIY LifePO4 battery packs has been really dropping, if I was starting over today my totals for batteries would be around $2000.00 rather then the $3000.00 that I spent.

I am considering buying another couple of Tesla battery modules to double my storage capacity.

I could have gotten by with two solar charge controllers instead of the three that I purchased.

[Joe Camper]

Persheate that Fred. I have redundant inverters although my loads and draws r small and I only utilize 1 at a time.. Both r 2800 w and have 2 8D deca gel hooked to each one. The costs of these items were ZERO coustomers give me their old stuff all the time I've actually got enough to do another set at home and I plan on pulling all my lights and AV off the grid at some point. A little added input all 4 of my 8d Decca jell r almost 10yr old and they all still rest north of 13 volts. I love them, love to look see 13.1 with the controllers floating, gives me a warm fuzzy feeling.

So solar panels and those costs r what I'm interested in. The solar panels and costs was great info. I currently have only 1 panel attatched to each inverter and what they do is very adequate for what they r. However im often parked in a driveway sometimes on inverter and i have a trailer I pull that if I lined the entire roof with panels u wouldn't even really notice them and I probably will. Lot of your stuff is beyond my knowledge thanks for the input.

I assume the panels u r using would also be the best bang for the buck for me too? I would think I would not need the costly charge controllers u have put in and for a couple grand i could fill my trailer roof and cover a less expensive control?

I don't make the left coast too often but if God is willing ill be in Sacramento late May. If u were ready and willing to do some chassis stuff at that point bring yourself down to Norms towing and we will strip and redress your baby's underbelly.

[Gil_J]

Your 240V drawing is confusing me. First, can I assume you are talking ACV? If so, what will you do with 240VAC that's not split-phase?