My small power cart (4.8 kWh.)

Four Battle Born's (2S2P) matched at the factory for series operation. (Six would be better. But no room.) Victron Multiplus 24/3000, Victron SmartSolar 150/35 (there's a story behind that choice. I would buy a different flavor if I could do it over again.) On a Harbor Freight Push Cart.

A digital timer turns on AC to the Multiplus overnight (at non-peak hours) and if the Mulitplus thinks that the batteries are too low, then the Multiplus charges them up to 50% SOC for the next day's use. Otherwise, I let the sun charge the batteries.

I plan to add my cheapo SOK Coulomb meter tonight to get a better read on what's really going on, SOC-wise. (And to see if the SOK meter works.)

Currently (pun intended), I am using the cart to power a mother-in-law suite (200 W average, almost continuous) as an experiment, to gain experience with the realities of night, when there's no sun to charge batteries.

The main purpose of the cart is to survive long-term power outages - especially during the hot Phoenix summers - when, among other things, a window AC will be needed to keep us alive. (600 W unit, plus 240W of freezer and fridge, all intermittent loads. No idea if this will get us through a night when it's 100 degrees out (at night).)

I should take some flat straps and contain the wires so that I move the cart through the house in the dark without snagging on anything.

Very nice.

I have lived in the same area for 10 years. Not once has the power even flickered. As the POCOs APS and SRP continue to shut dirty coal burning plants down without replacing them, and our population keeps growing, I feel brown outs are coming.

Do you own the AC for your project yet?

I have a small solar generator, but mostly for charging cell phones. If it came to needing AC, out comes the generators. Of course I don't have the AC yet. Those 100 degree nights are horrible. I went camping in one of those. Definitely not glamping when the outside temp is 100. At least with the dry climate, I did not worry about insects as in other places I was at.

Another forum member said the same. But our APS power went out for a few hours this past Sunday. (They said a "major" power line.) Before that, it went out at the end of last summer for an evening, due to lightning. I had a smaller version of this cart at the time and rolled it to the house CB box to plug our freezer and fridge in. My 2000 W Gandiel worked okay in the heat, but didn't give me confidence. That's why I upped to the Multiplus. (Which derates to 2400 W in our summer heat.)

A year or two before that, APS went down for a few days in our sector. We had to drive 10 miles to buy dry ice to keep our freezer and fridge cold. Put most of our food in coolers and took them to daughter's house, 10 miles in the other direction.

So the power has not been very reliable in our old (50 year old) neighborhood.

As the infrastructure becomes older, as the war on the economy/environment ramp up, as foreign enemies try to hack our infrastructure, as inflation comes, I'm expecting worse.

I bought two AC units, one which I might use in a van/camper conversion if things ever turn around. It is a 12,000 BTU portable unit. But they derate it to 7500 because portable units heat up the house while they're cooling the house. I keep the output tube short and wrap it in reflectix, and that helps increase its efficiency. (I also pour a cup of water into the drain. Drops the output by 5 degrees.) But it draws 11 Amps while running. Just too much for my dinky battery capacity and my dinky solar capacity.

So I bought a super quiet 5000 BTU window unit from Lowe's over the winter. It's a 600 W unit and should keep our "bug out" room cool (although western exposure on the room). I plan to do some real world testing come July and August - if the power company doesn't do it for me first.

P.S. I am waiting for Lowe's to have a sale on the inverter generator that I want. BUT - while I've stocked up a whopping 5 gallons of gas, if the stuff hits the fan and the grid goes down, I won't be able to buy gas, let alone get it to the house. So at best a few days (nights?) worth of generator power.

So I keep wrestling with whether I should buy a generator or spend the money on more batteries or panels.

Nice setup. And similar to mine. I have same inverter/charger, and same battery capacity but I built my battery from 200aH cells. I thought about putting it on a cart, but hung it all up on the wall in my laundry room instead and ran a couple of new circuits to my fridge and computer stuff. The Victron is pretty amazing.

My system can maintain critical loads for about 24 hours with no charging. That gives me time to drag out the generator if needed once things settle down. The batteries can be recharged in 3 or 4 hours depending on how hard I want to push the little generator.

I keep wondering if I should have built my own battery bank (am an MSEE, Ham, etc. and build a (real) plane). Would have been cheaper, and for the same cost, I could have 7.2Kwh.

But as I get older, the possibility of me dropping a wrench on some terminals and shorting out 100 Amps in my face is becoming more real. And, although I've watched the videos about balancing, the thought of running through the top off/balancing stuff seems like too much trouble for me.

And the "state of the art" - about what components to buy - seems to be constantly changing. Even some of Will's links are out of date.

So I would always be wondering if I optimized my buying choices. Or if I screwed up somewhere when I need power.

BTW, and related to best components: I know Will likes the SOK's - and they're certainly cheaper that the Battle Born's - but I got some inside info that they won't do well when taken below 20% consistently. On the assumption that the Battle Born's will handle less than 20% okay, I suppose I'm paying for that last electron when the stuff hits the fan. (Although I might buy a pair of SOK's and use them as a "reserve" bank with my Giandel.)

It would be nice to have some dedicated wiring for the freezer and fridge. For now I'm toying with the idea of mounting a sub panel outside the house and moving the freezer & fridge to it, powered by the Mutli in its UPS mode. That would only require a few feet of new wire to bring the existing wire to the sub panel.

I am doing something similar to what you did only on a 12 volt system. I put mine on a hand truck so its easy to move up/downstairs. 3 - 200 watt panels and a HF 3500 watt generator as back up. Living in upstate NY AC is a rare issue, however, we are the 8th cloudiest place in the US. Currently looking at 2 - 300 Ah batteries.

What would you do different for the Victron SmartSolar 150/35? I've got the 150/50.

How about battery terminal protectors to cover the terminals? Should help decrease the risk of something getting shorted out (sparking and arcing).

The victron should be able to be configured to connect to AC only when needed (e.g. at a certain SoC, voltage, or load). That's how mine works. You wouldn't need an external device to connect the AC.

cinergi said:

The victron should be able to be configured to connect to AC only when needed (e.g. at a certain SoC, voltage, or load). That's how mine works. You wouldn't need an external device to connect the AC.

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You are correct, and I have mine set to charge from the grid if the battery gets low, but I have not yet figured out how to make the Victron connect only during certain parts of the day. So I also have mine connected to grid through a timer. With the low voltage connect setting and the timer, the battery can charge from grid if the voltage drops too low during the night.

I am always making adjustments so that could change tomorrow, but it is working fine so far.

Q-Dog said:

You are correct, and I have mine set to charge from the grid if the battery gets low, but I have not yet figured out how to make the Victron connect only during certain parts of the day. So I also have mine connected to grid through a timer. With the low voltage connect setting and the timer, the battery can charge from grid if the voltage drops too low during the night.

I am always making adjustments so that could change tomorrow, but it is working fine so far.

Click to expand...

Ahh, gotcha. I wonder if the Cerbo/VenusOS (possibly with Node Red) could do it.

Q-Dog said:

You are correct, and I have mine set to charge from the grid if the battery gets low, but I have not yet figured out how to make the Victron connect only during certain parts of the day

Click to expand...

I am wondering for ideas like this, there’s so few of us that want it, that Vcitron won’t include it in their firmware, but if they released the code, we could probably put these ideas into action.

My particular thing I would like the Victron to do is to set a limit for Charge current with multiple controllers. It comes so you can set an indidual SCCs unit, but with more than one SCC, you can’t choose a total limit. I could put in code and logic what I want to limit SCC1 + SCC2 + SCC3 < 60 amps, but Victron would need to open source its code for me to program that. To top that off, I’d like to only limit the charge to less than 60 when the SOC is less than 100%. THat way once fully charged, I can push a little extra amps into my high amperage devices when those come on.

I did look at an article, and someone loaded the firmware on a Rasberry Pi, but it took him a year. I’m sure he’s a much better coder than I would be. https://www.victronenergy.com/blog/2017/09/06/raspberry-pi-running-victrons-venus-firmware/

cinergi said:

Ahh, gotcha. I wonder if the Cerbo/VenusOS (possibly with Node Red) could do it.

Click to expand...

I don't know. I may eventually get a Cerbo, or Venus on Rasb Pi look interesting ( my wife has a couple of Pi that she plays with, so she would like to deal with that). I just don't need that kind of connectivity right now when I rarely leave the house.

chrisski said:

I am wondering for ideas like this, there’s so few of us that want it, that Vcitron won’t include it in their firmware, but if they released the code, we could probably put these ideas into action.

My particular thing I would like the Victron to do is to set a limit for Charge current with multiple controllers. It comes so you can set an indidual SCCs unit, but with more than one SCC, you can’t choose a total limit. I could put in code and logic what I want to limit SCC1 + SCC2 + SCC3 < 60 amps, but Victron would need to open source its code for me to program that. To top that off, I’d like to only limit the charge to less than 60 when the SOC is less than 100%. THat way once fully charged, I can push a little extra amps into my high amperage devices when those come on.

I did look at an article, and someone loaded the firmware on a Rasberry Pi, but it took him a year. I’m sure he’s a much better coder than I would be. https://www.victronenergy.com/blog/2017/09/06/raspberry-pi-running-victrons-venus-firmware/

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That's similar to a "closed loop" system - where the battery tells the system max charge amperage. That's what my system (Orion BMS) does -- it instructs the entire system (all devices) about what voltage to charge with, max charge rate, etc ... It does this over CANBUS BMS control (requires Cerbo).

pmikep said:

P.S. I am waiting for Lowe's to have a sale on the inverter generator that I want. BUT - while I've stocked up a whopping 5 gallons of gas, if the stuff hits the fan and the grid goes down, I won't be able to buy gas, let alone get it to the house. So at best a few days (nights?) worth of generator power.

So I keep wrestling with whether I should buy a generator or spend the money on more batteries or panels.

Click to expand...

This where a dual fuel genny would be a plus because propane can sit stored for a looong time with out going bad. ?

We have natural gas plumbed to the house so I've though about converting a generator over to it. But in a stuff hits the fan scenario, would natural gas be off too?

pmikep said:

We have natural gas plumbed to the house so I've though about converting a generator over to it. But in a stuff hits the fan scenario, would natural gas be off too?

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That gas is under pressure. If no power at gas company pumping station= no pressure in the line.

pmikep said:

We have natural gas plumbed to the house so I've though about converting a generator over to it. But in a stuff hits the fan scenario, would natural gas be off too?

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Of the utilities I believe the natural gas will be the last to come up short. That is assuming there is some storage vs the TX model of direct well to the consumer. Or a pipeline break due to earthquake could could stop service very quickly. Probably a 500+ gallon propane tank on site would be the most reliable if that is what you are really looking for.

My parents in Maine frequently lose power, and have a natural gas generator that kicks in automatically. At below 10 degrees outside, heat is really needed, and power has been out two days, and the natural gas generator has never failed them.

Just received our first electrical bill since running the cart consistently (in time shift mode, when necessary) using two 330 W panels on the roof.

Saved $30 from same month a year ago.

Whoo-hoo! At this rate, it'll pay for the cart in 22 years! (Assuming electricity rates stay the same. Which is very unlikely. (And assuming that I live another 22 years. Which is unlikelier.))

Maybe it'll calculate to 14 years if the cart saves us $100/mo during the summer months. The power company here really gouges us for peak usage.

But this isn't passing a Sanity Test, because, according to the MPPT stats, I've generated only 79kWh total in the past month. Which is about $8. But the bill says that we saved 232kWh compared to this month last year. Which would be $23. Which could be $30 if I had generated this power during peak.

There was a note with the bill that some bills might be in error this month. So maybe this is a fluke.

Ah, I just remembered - I was away for 3 days during the month, where I turned power off in the suite. But that's only $1.50 worth of power. Something isn't making sense here.

We'll see what next month holds, as temps are forecast to hit 90 F next week.

And I should have another 300+ watts on the roof by mid-month.

The $35 SOK coulomb meter works okay. It's a little quirky and not as customizable as the Victron 712. For example, the backlight is always on (at full bright) when there's a battery discharge. The backlight flashes (at full bright) when the battery is charging. There's no way (that I've found) to dim the backlight or to change this behavior. (Supposedly the backlight turns off when there's no activity with the battery. But how often will that ever happen? My Multiplus is always drawing some current.)

Well, at least it wouldn't be flashing at night with solar while you're trying to sleep. It drives me nuts flashing during the day as it is.

They don't give you the wire you need to power the unit.

I don't know yet how well the SOC tracks. (Am charging to Absorption tonight.)

There is no way to mount the shunt (that I can see). So it either hangs from your cables or you come up with a clever solution.

Interestingly, I do not see it for sale on their website as of this writing. (It was 6 weeks in shipping and I had to email Min (?) about the delay.)