2200 watts of solar on the roof?

[dreadlocks]

lol I got a lil acronym happy there did'nt I.. Verk has the correct decoder ring.

EasySolar is a bunch of their standalone components pre-wired into a larger chassis, its still modular as far as component replacement/upgrade.. but Victron neglects 60Hz 120v power sources, they barely support it as an inverter output and none of their decently sized AC chargers accept worldwide voltages for some reason... so the EasySolar only works with 50Hz 220v AC inputs and outputs.

 

[MTVR]

Is there a difference between battery types as far as how fast you can pull power out of them? For example, if we become partially shaded during the day and the A/C system suddenly finds itself running off the house battery bank (hopefully only for a short period of time), is it safe for the batteries to discharge at the rate that the A/C is asking of them?

I looked at a Panasonic 12,000 BTU mini-split last night with a 19 SEER rating. The specs seem to indicate that it draws just under 9 amps at 115VAC, which would be about 85 amps at 12VDC, or 42.5 amps at 24VDC (a little over 1,000 watts). When sizing an inverter for the mini-split, would a 1,500 watt inverter be appropriate? Is it a good idea to run inverters at close to their maximum capacity, or is it better to "supersize" the inverter so that it's just loafing along when the mini-split kicks on?

 

[dreadlocks]

Lead based batteries (FLA/AGM/Gel/etc) are all subject to Peukert's law: https://en.wikipedia.org/wiki/Peukert's_law that basically states the bigger the load, the less capacity you have..

Starter Batteries are obviously designed to output high amps, Deep Cycle batteries not so much.. but even then your AC is less amps than a Diesel Starter motor and 42A out of a multi battery 24v bank is well within any ratings.

Lithium chemistry can dump a buttload of amps on demand, and Peukert's law is not in play.. but your usually limited by its BMS on amp output, a single BattleBorn style battery for example is limited to 100A constant, and 200A surge.. well below most lead batteries, but enough it can still output what you need.. If your building your own pack you'd pick a BMS that meets your current needs and then some.

 

[MTVR]

Excellent. Thank you...

Another question- what about an automatic starter for the truck's engine, triggered off a predetermined low voltage point on the house battery bank?

I'm assuming that there is a way to shut down the electrical system once the house bank is depleted to a certain point, but what about using an automatic starter to fire up the truck's engine at that point? We've got a large-case 150-amp 24VDC alternator, that I'm assuming would have no problem powering the mini-split by shuffling electrons through a DC-DC charger. How would we do that? Does the inverter automatically shut down at low voltages? Do we need a seperate device to trigger the engine auto-start? Will a DC-DC charger handle loads that large?

 

[MTVR]

And what about my question on inverter sizing? We are considering running at least two inverters- a large one to run the mini-split (and/or any other high-power needs), and a smaller one to run the rest of the lights, water pump, power for cell phones and laptops, etc....

 

[dreadlocks]

Victrons fancy controllers like Venus or CCGX have support for Engine Start/Stop: https://www.victronenergy.com/panel-systems-remote-monitoring

they can be configured to start an engine once the SOC reaches a pre-defined threshold, and then stop it once the bank is full.. the trick is going to be getting the vehicle to start/stop off a simple signal wire, but I doubt your big military rig has an immobilizer or any of that fancy stuff so it should be doable, basically setting up a push button start/stop and wiring it to the Victron instead of a button.. kinda like a remote start would be wired up.

 

[dreadlocks]

Your inverter loads should be minimal IMO, all your lights/pumps/cellphone chargers should be direct DC.. Laptop Chargers and TV's that are DC are silly expensive, many people run those off small inverters.. but now that USB-C charging for laptop is the standard I'd suggest a high wattage USB-C PD plug that goes right to DC for laptop needs.

The reason for the smaller inverter is because of efficency ratings, a small inverter at 80% load is going to be like >90% efficent.. a big inverter at like 10% load is going to be like 75%+ efficent.. so for something like a TV thats on for many hours a day having its own inverter appropriately sized for just the TV will use less power than trying to run it off a big 2k watt inverter.

I dont run a TV or any of that, so I'm fine with my big 1200VA inverter just fine.. none of my smaller loads run all day long and I'm not sweating a few extra AH.. but if your full timing with constant low wattage AC running then having a dedicated lil inverter for those loads does make sense.

 

[MTVR]

Yeah, sorry, that other stuff would be run directly off DC- haven't had my morning coffee yet...

 

[dreadlocks]

almost all electronics run off DC internally, Ive converted many "AC" house appliances to DC by simply reading the specs on the power bricks and giving em the same.. If your laptop says it wants like 18v @ 3A, just go get a 24v to 18v dc converter rated for like at least 3A and put the same plug on it.. bam, made it direct DC without a $100 car charger.

If the device dont have an external power brick, its just built in.. you can crack many TVs open, figure out what its power supply is outputting and wire up a DC converter in its place in parallel and now its an AC/DC TV that didnt cost >$500 for a 20in... this is what most people living full time off the grid do, converting AC appliances to DC is often a fraction of the cost of buying one that already runs off DC directly.

Now things with motors and heating elements are more difficult to convert to DC, you have to replace more components than just the power supply.

 

[MTVR]

So just spit-balling here, but a pair of 100Ah Battleborns in series for 24VDC, Nine Panasonic HIT N250 panels on the roof, and a fan-cooled electronic warfare cabinet containing MPPT solar charge controller(s) to be determined, a 24VDC-24VDC charger from the truck's alternator, maybe a 120VAC to 24VDC shore power charger for the rare occasion that we can sneak up on an electrical outlet, and something like this to run the mini-split?

 

[MTVR]

We're not planning a TV- just cell phones and laptops, that already run off DC...

 

[Alloy]

So just spit-balling here, but a pair of 100Ah Battleborns in series for 24VDC, Nine Panasonic HIT N250 panels, MPPT solar charge controller(s) to be determined, a 24VDC-24VDC charger from the truck's alternator, maybe a 120VAC to 24VDC shore power charger for the rare occasion that we can sneak up on an electrical outlet, and something like this to run the mini-split?View attachment 585019

Haven't run the number but you'll need to look at which solar controllers works. Our Panasonic panels are rated at 70VDC (I've seen it higher). Two 2 -70V panels in parallel will need a controller with a input voltage greater than 150V. A series/parallel setup with 9 panels may not work.

For the AC inverter load assuming 15' of pos and 15' of neg wire
85A @ 12V would need 2ga wire
42.5A @ 24V would need 8ga wire
& 22A @ 48V would 12ga wire........common for off grid homes

 

[dreadlocks]

it sounds like your not expecting any constant low wattage AC loads, so you can forgo a smaller inverter out the gate.. might keep it in your head tho down the road, mebe you get an e-bike or you use a bunch of battery powered tools and always have a pack getting charged up at 100W.. you dont want to build yourself into a corner and make it unnecessarily hard to put a low wattage outlet in later.

Key metrics I looked at when shopping for an inverter were its efficiency rating, you want at least 90%, that should be easy to obtain @ 24v.. and its idle power consumption, this is how much energy it takes when nothings running. Many big inverters have absolutely absurd idle power consumptions so you'll want to avoid those, and is another reason why you dont greatly oversize your inverters when you dont need it..

 

[Alloy]

The reason for the smaller inverter is because of efficency ratings, a small inverter at 80% load is going to be like >90% efficent.. a big inverter at like 10% load is going to be like 75%+ efficent.. so for something like a TV thats on for many hours a day having its own inverter appropriately sized for just the TV will use less power than trying to run it off a big 2k watt inverter.

We run a 600w and a 3000w in an attempt to have the inverters running in the 20% to 60% range. The other factor is standby power the 600W uses 0.5A while the 3000w is around 4A. We leave the 600w on 80% of the time.

 

[dreadlocks]

in my experience with most power conversion schemes it seems like most of the time 80% is the sweet spot in efficiency, if you look at most spec sheets for power supplies of various types the vast majority of em seem to hit their peak efficiency ratings, which is what they of course advertise, when at 80% load.

so I'd bump that 60% up to 80% just cuz thats likely to be even better unless of course you got a manufacturer spec sheet that says otherwise.

My Victron 1200VA inverter is 91% Efficient and uses 0.6A idle in normal mode, and 0.08A idle in Eco Mode.. I keep it on all the time in Eco mode and trick it to come on if something dont work in eco mode.. its specs are nice enough a smaller inverter seems pointless.. but this is the biggest inverter victron makes for 120VAC@60Hz AFIK.. I'd love to see an 1800VA w/LFP @ 24v.

Could go the other way, setup a AC only inverter @ 80% size.. wire em up to a AC-ON switch that turns em both on at same time.. and then use something like the Victron 1200VA on all the time on all your house outlets.. its limited to max 1000w but could efficiently take care of most everything on outlets if you do like I did and get a 700W dorm microwave and a 600W travel coffee maker.