Fun with 48V solar and battery project

Been dreaming about building a 48VDC solar array, battery, inverter and charger for a few years. After a few PM's with HarryN, I started collecting the bits and pieces. The breakers, fuses and switches would need to be rated for the higher voltage of the new system; most of my spares were rated for 32V maximum. The series C Blue Sea toggle breakers are rated higher than the others. The Midnight Solar MNEDC series breakers are rated for even greater voltages than the Blue Sea series C. They all cost about the same.

The 48V lithium battery needs to be charged-to and maintained at 56V, which means selecting solar panel(s) able to produce enough voltage to activate a 48V Victron MPPT 150/35 controller. From the Victron owners manual, I understand this voltage must be at least 5-volts greater than the charge setting of 56V. In other words, the array must produce at least 61 volts for the controller to “wake up”.

I had wanted to try a single 48-volt Panasonic HIT 330W panel with an optimum power voltage of 58V but worried the single panel might not produce the needed voltage to activate the MPPT. Right or wrong, selected four 12-volt 100W Renogy Esclipse panels for a series connection, which would theoretically provide a series-combined optimum operating voltage of 70.8V. The rationale for four panels: if I fail to make the Eclipses work in 48V setup, I can still parallel the panels and go with a 12V house battery system.

Assembly of the array required three pairs of Hein's 8020 crossbar tower kits, two of Hein's 8020 46-inch cross bars and some of his panel mounting tabs. The center cross bar was special-ordered from 8020 (1503-LS-Black-FB x 46 inches with two end taps p/n 27060).

Youngest son provided much need muscle to hoist the array up onto the roof without any personal injury or property damage. A quick check indicated a series open circuit voltage of 81V (in the shade). Decided to drill a new 1-inch hole in the roof and pull the pair of 10AWG cables through a 6" x 6" x 4"H NEMA 4X box from Home Depot. Used elastic co-polymer tape to attach box. Each cable runs through a 0.08" - 0.24" Range 3/8" NPT Black Nylon Dome/Liquid Tight Cable Strain Relief Fitting. I ordered these from McMaster Carr but they are readily available from several mail order places, including Fastenal.

Need to install a 10A fuse on the positive side of the array (must be rated for voltage). After reading a few solar blogs, I have decided to install Midnight Solar MNEDC 10A disconnect breakers on both legs of the solar array before connecting to the MPPT controller.

Will test the MPPT controller in a few days and update this post.

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MMMMM...SOLAR! Details on the battery you are going to use?

Looks good. Glad to see another 48 volt system on the forum.

I belief that too much hair also has a 48 volt based setup.

You are right about the need for the Vbat + ~ 5 volts for the Vmp minimum. It is an annoying "feature" that many solar charge controllers share.

OffroadHamster said:

S
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MMMMM...SOLAR! Details on the battery you are going to use?

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Single 48V commercial lithium battery block (no longer manufactured) with on-board BMS. Rated 77Ah @ 8 hours @ 25C. It's been in my office backing-up my network for two years. Will eventually be switching-over to a 48V sodium battery, when I receive the loaner from the factory.
Have been selling batteries since 1993 (primarily nickel cadmium, sodium and lithium chemistry(s)). The business changes rapidly; difficult to keep-up with technology.

HarryN said:

You are right about the need for the Vbat + ~ 5 volts for the Vmp minimum. It is an annoying "feature" that many solar charge controllers share.

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I have a 24v system and that one caught me as well. I have three panels that I had to rewire from parallel series to get over that +5v threshold and wake up the charge controller.

Closeup on the Midnight Solar MNEDC breakers with larger 1/4" studs and beefier plastic case. They are rated 150VDC. As you can see, they fit perfectly into the Blue Sea panel and will serve to disconnect solar array from MPPT.

The output of MPPT will run back through the 40A "Battery" disconnect breaker. The safest charge rate for my 48V lithium battery is 40A (although fused for 60A internally).

With exception of solar array, the smaller 48V system components will be mostly pre-wired inside the wooden box to allow me to remove it from the van in about five minutes. The ventilated birch wooden boxes with handles are Ikea Ombyte 23331 - sold as stackable pair.

The Sterling 48V-12A charger, attached to the left side of box, requires 120VAC shore power. The grey/blue box on the right is the 48V lithium battery. The bright blue box is Victron 48V/1200W inverter. These will be hidden inside bench seat cabinet.

Next step is to install and program the Victron 702 battery monitor and Victron 48V Battery Protect and fusing

48V is not high voltage with regards to enclosures, but it is high enough, that you may consider adding plastic finger guards over the exposed conductors in the enclosures. Its a bit uncomfortable to make good contact with a 48V circuit while grounded. I on occasion find myself manually checking voltages and visually inspection components though.

Shawn182 said:

I have a 24v system and that one caught me as well. I have three panels that I had to rewire from parallel series to get over that +5v threshold and wake up the charge controller.

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The other option is to use a PWM controller - example bogart engineering.

On many days, the actual operating Vpanel isn't all that much higher than the battery peak charge voltage.

you may consider adding plastic finger guards over the exposed conductors

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Good points: The wooden enclosure has a nicely-fitted cover. The bus bars and bolts will have covers.

Can never be too careful around these projects. Always remove rings and bracelets.

Story: While I was witnessing a factory battery technician commission a system, a metallic wrench fell off the top-tier of the battery rack and dropped directly onto my wedding ring and the other end across the terminal of a single 1.4V 250Ah high-rate nickel cadmium cell, simultaneously. No sparks but the gold ring became super-heated and seared into my finger in a fraction of a second. I stuck my hand into the tech's Dr. Pepper "big gulp" cup but it was too late. The ring burned to the tendons and my skin was charred.

This happened over a dozen years ago. The ring was repaired by a jeweler but I still have a scar around that wedding finger. I'm still married. I still feel like an idiot for leaning on the battery rack and forgetting to remove the ring.

These days, battery wrenches are insulated.

Good thing I finished dinner. Thanks for sharing your insight and sorry about how you got hurt.

I reminds me of a guy who ran our machine shop. He posted pictures of common injuries next to each machine. HR made him take them down. They were very graphic. No one got injured on his watch though.

I am very careful. If I remove a battery lug, it immediately gets covered by a vinyl end cap:

https://www.amazon.com/N1ChainPads-Large-Push-Pliable-Vinyl/dp/B07PRCGBBH

I'm working on 3D printed enclosures for my terminal blocks.

Regards,

Mark

As of today, Victron does not offer a stand-alone 48VDC/120VAC 60Hz inverter larger than 1200VA. I purchased the 48/1200 Phoenix Inverter VE.Direct with Bluetooth, which allows operator to use a cell phone to set the preferred "battery low voltage shutdown" to prevent over-discharging the battery.

Began the testing of small kitchen appliances to determine which would work with this new 48V system, without tripping-out the inverter.

Results from the indoors bench testing:

1) Cuisinart drip coffee maker. Success making 10 cups. Although, we will never use it in the van. More likely, will use hot water to "pour-over" or French-press. Coffee maker appears to use 1100W.

2) Tramontina induction cook top. Success boiling four cups water in less than two minutes on 1300 setting. I used the Tramontina pans that came with the $99 kit. Cooktop appeared to use 1150W in this setting. I did not try 1500 setting. Making sauces or oatmeal ought to be simple.

3) Vitamix blender. Success making extra-large smoothie with lots of frozen berries and some ice. This was a pleasant surprise as I expected the frozen berries would cause the Vitamix to trip the inverter.

4) Hot water kettle. FAIL. Although labelled 1500W, it pulled 1600W and tripped the inverter in less than 10secs. I see that Hein used an 800w slicone hot water kettle. I may by one of these 800W kettles.

5) LG LMC0975 microwave. Partial success. Tried to boil 16oz water in large ceramic mug. Full power tripped inverter. Retested at 80% power. Boiled water in 60secs.

My summary: This Victron inverter is rated conservatively @ 1000W @ 25C (77F). I watched it support 1300W for 5 mins. My 48V lithium battery is rated 77Ah. I used 18" inches of 6AWG for the battery connection. Each of my tests used 2% of battery capacity according to Victron BMV-712 Smart. I did not use the 400W solar array in this testing.

dynaco1 said:

...I stuck my hand into the tech's Dr. Pepper "big gulp" cup but it was too late. The ring burned to the tendons and my skin was charred.

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That is one ugly picture.

Not to hijack the thread. I think the safety aspect is important.

We had a guy lose much of his hand when he grabbed a crane power rail. He probably still would have injuries, but I'm convinced that his wedding ring made it all worse.

Back in the day, before the crane power rail incident, I saw a picture of the result of a ring finger staying behind when a guy jumped off of a stake body truck. The ring hooked on something. He not only lost the finger. The associated 18 inches of ligaments and tendons were hanging off the finger. Really ugly.

I stopped wearing my wedding ring or any other jewelry right after that. My wife at first protested. I told her that with the dangers associated with my electrical and maintenance work she needed to get past it.

I echo MWD's caution about 48 VDC being dangerous. Some of our remote substations had 48 VDC station batteries. 48 VDC is much nastier than the 12 volt vehicle system most are familiar with.

Back to topic.

Nice work and Write-up!

vic

I have had a few people ask me about sourcing the Midnite Solar DC breakers rated 150VDC