Diversion Controller with LiFePo batteries

[ericmwalsh]

I have been doing solar designs for quite a long time and I am wondering if an old tech is now the best new tech.

I feel like a diversion load controller will offer a lot of advantages to a LiFePo battery set up, reducing cost and adding capacity.

I am up north, so a resistive air heater would work as a diversion load, but I'd imagine if I moved to a warmer climate I'd rather use water as the dump load, and further south an AC unit could potentially be a dump load - but I haven't put any work into that.

You should be able to get away with a 1600W solar array controlled by a cheap Tri-star-60 allowing you to use all the power from sun while keeping your batteries perfectly content.

And once you have the system for solar, you could use disgustingly cheap wind turbines or home made dc sources from a generator and let the TS-60 do the real battery battery management.

If you've done it I'd like to hear about problems you encountered. If you want to do it I'd be happy to help you with the design.

 

[Daddy Tanuki]

I am in the process of trying to do what you are more or less talking about. currently I am using the MPPT version of the TS-60 but was considering buying the none Mppt TS-60 for load diversion. the issues I had after reading the manual on morningstars website was can you set a custom charge setpoint and still do load diversion? you have to set the dipswitch one way for load diversion and the opposite way to enable a custom charge setpoint.... no were in the manual did it discuss this that I could see.

 

[Phil.g00]

The Tristar documentation is out there, I have seen it.
Alternatively, the Outback MPPT's have a PWM output, possibly Midnite Solar as well, it's been a long time since I researched this.
I have never got around to using this function, but I came away with the opinion that the tristar models were a less expensive solution, but the dump load had to be spec'd so as not to exceed 45A or 60A, depending on the Tristar model chosen.
I also think you had to dedicate the controller to only this diversion function.
Hugh Piggot's wind turbine blog shows how it's used.

As I recall the Outback flexmax controller was more flexible. It could still perform as an MPPT, and a PWM output could be set at a set battery voltage, which in turn could drive an SSR which could any rating.
As I say I looked into it a while back, so do your own checking.

 

[Frick]

Diversion is why I went with an electrodacus setup. My loads are going to be 2 hot water tanks with replaced elements. Mostly I think our power usage will be much smaller than capacity, and by that most of the collected solar energy (and hydro I’m developing) will go towards water heating. There is a propane instantaneous water heater inline in case of excess demand or very dark days.

 

[Daddy Tanuki]

Diversion is why I went with an electrodacus setup. My loads are going to be 2 hot water tanks with replaced elements. Mostly I think our power usage will be much smaller than capacity, and by that most of the collected solar energy (and hydro I’m developing) will go towards water heating. There is a propane instantaneous water heater inline in case of excess demand or very dark days.

I came across this but he no longer sells the whiz bang version from what I understand. My diversion tank would be a 4-6k gallon insulated tanker truck tank buried next to my shop, that or with an insulated shed built over it. my thought's were to let it run a year or so and then use it for hot water and even forced air heaters using smallish radiators.

 

[Frick]

He made a mppt thermal controller, but the newer DSSR20 with diversion largely replaces it which is what I bought a bunch of.

While some argue an mppt controller is more efficient (other show proof it isn’t), for me that extra few percent is moot since it would be batteries full by 11am with or 11:20 without, then the rest of the day the panels are switched off losing the bulk of their capacity.
If you do an underground tank, there will be significant losses to the earth. You might consider spraying the tank with foam and then concrete before burying it to stop that. the tank would provide you with a stable hydronic heating source, being constantly replenished by panels. I would hesitate on using it for potable water though, as large tanks like that kept warm tend to go funky.

i saw a neat video of a guy in the north US heat underground greenhouses year round by burying 8” flexi drain pipe 6’ deep a few hundred feet away and back and just flowing air through it. Cools in summer, heats in winter. grows tropical fruits and citrus and such year round.

 

[Ampster]

I checked if this was in the off grid section. Since it is not, I thought I would mention that my diversion load is the grid. I do try to use a heat pump water heater to store some energy in addition to my LFP pack.

 

[Daddy Tanuki]

He made a mppt thermal controller, but the newer DSSR20 with diversion largely replaces it which is what I bought a bunch of.

While some argue an mppt controller is more efficient (other show proof it isn’t), for me that extra few percent is moot since it would be batteries full by 11am with or 11:20 without, then the rest of the day the panels are switched off losing the bulk of their capacity.
If you do an underground tank, there will be significant losses to the earth. You might consider spraying the tank with foam and then concrete before burying it to stop that. the tank would provide you with a stable hydronic heating source, being constantly replenished by panels. I would hesitate on using it for potable water though, as large tanks like that kept warm tend to go funky.

i saw a neat video of a guy in the north US heat underground greenhouses year round by burying 8” flexi drain pipe 6’ deep a few hundred feet away and back and just flowing air through it. Cools in summer, heats in winter. grows tropical fruits and citrus and such year round.

sorry I did not explain myself well, when I said insulated This was in reference to the tank and the idea was to spray foam the exterior to a depth of about 4 inches. Then bury it with concrete caps on either end for service purposes and or semi bury it and build a low shed over it to cover the top.

run stainless tubing inside it as a heat exchanger for the potable water as well as shower bath water and then straight from the tank to force air fan radiators for the heating of the cabin. The idea was to fill the tank with a 70/30 mix of LLC and water and then let it heat up for how ever long it takes to get to temp. obviously I would place temperature and pressure probes (I work with both in my actual job) along with a pop off pressure valve for safety sake.

R/

Ken

 

[Daddy Tanuki]

I checked if this was in the off grid section. Since it is not, I thought I would mention that my diversion load is the grid. I do try to use a heat pump water heater to store some energy in addition to my LFP pack.

unfortunately japan is a PITA when dealing with electric companies the government for all intents and purposes allows the electric companies to create the regulations and rules and then rubber stamps them into law.

you cannot grid tie unless the entire system is installed by one of their (electric companies) preferred installers. so any sort of DIY has to be entirely offgrid. makes no difference if you have an electrical engineering degree or are a rank beginner. My primary house has 8Kw of sharp panels on it and it is a grid tie system. 8 years ago it cost me 35k USD I could have done the same job for about 1/3 of that with the major cost being buying the required japanese grid tie inverter. It was all installed by one of the preferred companies (read company that jams you and gives kickbacks to the power company head honcho.)

The cabin had access to the grid, but we lost that last year as the costs for maintaining power lines in our area have steadily increased over the years due to the customer base declining as the old folks pass away and youngsters have no desire to live or have a cabin in the boonies. TEPCO sent notice that anybody more than a mile off of the main power lines would have to start paying for maintenance and repairs themselves. TEPCO will do the work, you just have to pay 100% of the bill in regards to that. when our power line got knocked down during a typhoon and they quoted me at 10K to fix and rehang the line I told them politely no thank you and unhooked.

currently I heat the house with a wood stove where I gather and cut all of my own firewood. Hot water for the indoor bathtub is an on demand propane water heater and for the outdoor tub I use a small water heater than I made that will burn wood, coal or even kerosene. I am a fabricator and mechanical repair guy by trade) so making things like a wood stove or a wood burning water heater come easy to me.

The current setup is fine as its a weekend thing only, but when I retire in in a bout 12 years I would prefer to use wood heating more for the ambiance than as the primary heat source. hence my weird idea about diverting excess to heat a huge honking tank.

R/

Ken

 

[Frick]

Yes, that would work nicely. Thanks for painting the picture better, sounds like a lovely setup. The small forced fan radiators work very well, probably good for 30k btu per sq ft of radiator at a 100 degree delta as a guess. Burying pex in the floor Is also nice, warm but not stuffy.

We are heading to where it’s always a nice temp, no heating or cooling needed but hot water is the definition of civilization to us so that’s important. Another stack of panels is slated for the hot tub I will build, maybe 4kw worth, those are going to be direct dc heated with a digital controller.

 

[Daddy Tanuki]

i saw a neat video of a guy in the north US heat underground greenhouses year round by burying 8” flexi drain pipe 6’ deep a few hundred feet away and back and just flowing air through it. Cools in summer, heats in winter. grows tropical fruits and citrus and such year round.

I just reread this last part. thats pretty smooth actually kind of like a geothermal heat pump where you bury the pipe at a depth of 6 feet and run water through it to a heat pump using the constant temp below the frost line to raise the temp to 65 or so.

 

[HammaMan]

unfortunately japan is a PITA when dealing with electric companies the government for all intents and purposes allows the electric companies to create the regulations and rules and then rubber stamps them into law.

you cannot grid tie unless the entire system is installed by one of their (electric companies) preferred installers. so any sort of DIY has to be entirely offgrid.

To get around such things, just call the associated companies once installed if it's actually done professionally and basically pay them to claim the install. I installed a $30k mitsu mini split system with multiple indoor and outdoor units and then found a local installer to "claim" the install. I had them do the full pressure test / leak down and coolant release, and they claimed the install so that the full 10 year warranty would be in effect. They commented that it was done better than most pro installs and were happy to be able to provide warranty services in the future if it needed it.


I believe it'd be easy to get a company to do the same on an install so long as they were compensated to do a full inspection of the system. The alternative is to do the whole home on solar with grid to simply supplement it as needed. Typically if an extension cord is used it's not considered "permanent". Thus run the whole home off solar setup with a ~50a plug connected to the electricity service.

 

[Daddy Tanuki]

To get around such things, just call the associated companies once installed if it's actually done professionally and basically pay them to claim the install. I installed a $30k mitsu mini split system with multiple indoor and outdoor units and then found a local installer to "claim" the install. I had them do the full pressure test / leak down and coolant release, and they claimed the install so that the full 10 year warranty would be in effect. They commented that it was done better than most pro installs and were happy to be able to provide warranty services in the future if it needed it.


I believe it'd be easy to get a company to do the same on an install so long as they were compensated to do a full inspection of the system. The alternative is to do the whole home on solar with grid to simply supplement it as needed. Typically if an extension cord is used it's not considered "permanent". Thus run the whole home off solar setup with a ~50a plug connected to the electricity service.

i would love it if Japan was a logical as this. Let me explain how it works here... you study say building a small garage, go to the local government construction approval office, learn all the requirements, put in your permits, start construction and half way through the building of your garage, they come down inspect you and tell you the only way that you will get your compliance is if you pay one of the 10-15 companies that are authorized to do this type of work and certification to finish it. I have a friend who is Japanese, has all the correct government licenses and he could not certify my garage in Yokosuka because the local city decided if you did not have an office in the local city and were not paying the city taxes you could not operate here... regardless of what licenses you hold at the national level. that's how screwed up the Japanese government is... so no building your own and getting a company to sign off on it will not work here... if they are not taking their full pound of flesh from you they will just ignore you until you pay.... the frame for my garage, which meets all requirements is still in front of my house... a skeleton frame of steel beams..no roof, no walls...no garage... its what prompted me 10 years ago to buy a second house in fuji where the rules are somewhat less restrictive due to the fact the area is unincorporated. but any company that has the full backing of the government via TEPCO is not going to take a partial payment when they can tell you to bugger off and wait until you fold. BTW I built that framework of "I" beams for my garage 10 years ago... I am a licensed welder in both Japan and the US. I weld on Navy ships and fabricate parts for them... It matters not my engineering prowess or lack of it... all that matters is who is getting paid off. I tired of that game several years ago. off grid is out of their jurisdiction... i do what the heck I want without their permission.