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Building a full-time vanlife retired-ambulance — 48V system for mini-split, induction cooktop, Starlink, hot water, TV — looking for advice :)

robby said:
The Passive Balancer in the Eco Worthy BMS actually works very well while the Eg4 sucks.
The Cells in the Eco Worthy stay well balanced while the EG4 drift all over the place.
I have both in use right now and there is no comparison.
Click to expand...
Thank you for the lived experience, I think I’m going Eco worth then
 
Some thoughts. Insulate well, and then you need a lot less A/C. Solar panels, as much as you can. A couple of folding 200w panels and another MPPT you can plug them into while parked doesn't take up THAT much space, compared to what the extra batteries that might represent could be, and then you also have less worries about where you park, because you can drag the panels into the sun and park in the shade and still be getting 300-400w charging much of the day (probably an extra 1-2kwh a day). Light colors for the ambulance paint! White roof helps a ton. Both reducing solar gain, and also if you use bifacial solar panels on the roof, you'll get another 10-20% of solar power out of them.

For a water heater, look at a marine diesel water heater that also takes a 300w heating element. You can use the electric heating element as a dump zone once the batteries are fully charge, and run it off diesel otherwise. That would likely save you 1-2kwh on battery load. Diesel is a lot more energy dense than batteries are, so a gallon fuel tank for the diesel heater is going to represent 5-10kwh worth of batteries, easy. Or since it is a diesel truck anyway, tap the fuel tank and then you don't need to take up space with a propane tank, or diesel tank for a water heater.

Consider looking at a DC powered minisplit. Running your A/C inverter all day long, just to provide power for your A/C is going to kill .5-1kwh per day (1-2kwh per 48hrs). AND you are losing efficiency converting DC to AC, and then likely back into DC in the minisplit (assuming an inverter based minisplit). There you are talking probably 10-15% efficiency losses versus a straight DC mini-split. So overall, if you are talking 48hrs of use, no charging at all, figure a loss of 3-4kwh by going with an A/C mini-split.

Solar panels weigh more than the batteries you could have, but do not take up space inside, and frankly, 100-140lbs of panels on the roof isn't all that much extra weight, even up high. Extra insulation isn't going to take up much space inside, compared to the efficiency gains you'd get. Light color paint adds a bunch more. Going with a DC based A/C is going to add a ton of efficiencies. A diesel water heater a bunch more too.

Overall, you can easily shave half the size/capacity/weight of your batteries. Even if you are sticking to hot and humid environments for ambulance life, you could likely get away with 10kwh all day long (and the next too) with that approach.

I am still a few years away from something like this myself (though going transit route) and doing as much research as I can, I am personally looking at around a 500-600ah 12v system, approximately 1000w on the roof, a 30a DC-DC charger, Victron system, 3000va Multiplus II, diesel marine water heater with 300w heating element, DC 12v ductless mini-split, very well insulated. I WILL likely either tote my Sportsmans 1000i suitcase inverter generator, or just as likely I'll look for a new 1200-1400w suitcase generator. That Sportsmans 1000i can probably get the job done, but figuring in losses and 75% max load, that is really only maybe 550w into the batteries. 10-12hrs to recharge the bank from 0 is a mighty long time if I am trying to do it off that generator (worse off the DC-DC charger, but that DC-DC charger is as much just to HELP keep things charged up). A 1400w suitcase generator at 1000w is more like 6-7hrs to charge the battery bank up from zero, which is a lot better. Oh, and 1-2 200-220w folding panels. That should be a day of very heavy AC use with minimal solar power. With good solar in a day, that'll keep everything charged up. At worst, parking in the shade or overcast and hot, A/C use would go down some, but little recharging there. I can always break out the generator once a day for a few hours.
 
azazel1024 said:
Some thoughts. Insulate well, and then you need a lot less A/C. Solar panels, as much as you can. A couple of folding 200w panels and another MPPT you can plug them into while parked doesn't take up THAT much space, compared to what the extra batteries that might represent could be, and then you also have less worries about where you park, because you can drag the panels into the sun and park in the shade and still be getting 300-400w charging much of the day (probably an extra 1-2kwh a day). Light colors for the ambulance paint! White roof helps a ton. Both reducing solar gain, and also if you use bifacial solar panels on the roof, you'll get another 10-20% of solar power out of them.

For a water heater, look at a marine diesel water heater that also takes a 300w heating element. You can use the electric heating element as a dump zone once the batteries are fully charge, and run it off diesel otherwise. That would likely save you 1-2kwh on battery load. Diesel is a lot more energy dense than batteries are, so a gallon fuel tank for the diesel heater is going to represent 5-10kwh worth of batteries, easy. Or since it is a diesel truck anyway, tap the fuel tank and then you don't need to take up space with a propane tank, or diesel tank for a water heater.

Consider looking at a DC powered minisplit. Running your A/C inverter all day long, just to provide power for your A/C is going to kill .5-1kwh per day (1-2kwh per 48hrs). AND you are losing efficiency converting DC to AC, and then likely back into DC in the minisplit (assuming an inverter based minisplit). There you are talking probably 10-15% efficiency losses versus a straight DC mini-split. So overall, if you are talking 48hrs of use, no charging at all, figure a loss of 3-4kwh by going with an A/C mini-split.

Solar panels weigh more than the batteries you could have, but do not take up space inside, and frankly, 100-140lbs of panels on the roof isn't all that much extra weight, even up high. Extra insulation isn't going to take up much space inside, compared to the efficiency gains you'd get. Light color paint adds a bunch more. Going with a DC based A/C is going to add a ton of efficiencies. A diesel water heater a bunch more too.

Overall, you can easily shave half the size/capacity/weight of your batteries. Even if you are sticking to hot and humid environments for ambulance life, you could likely get away with 10kwh all day long (and the next too) with that approach.

I am still a few years away from something like this myself (though going transit route) and doing as much research as I can, I am personally looking at around a 500-600ah 12v system, approximately 1000w on the roof, a 30a DC-DC charger, Victron system, 3000va Multiplus II, diesel marine water heater with 300w heating element, DC 12v ductless mini-split, very well insulated. I WILL likely either tote my Sportsmans 1000i suitcase inverter generator, or just as likely I'll look for a new 1200-1400w suitcase generator. That Sportsmans 1000i can probably get the job done, but figuring in losses and 75% max load, that is really only maybe 550w into the batteries. 10-12hrs to recharge the bank from 0 is a mighty long time if I am trying to do it off that generator (worse off the DC-DC charger, but that DC-DC charger is as much just to HELP keep things charged up). A 1400w suitcase generator at 1000w is more like 6-7hrs to charge the battery bank up from zero, which is a lot better. Oh, and 1-2 200-220w folding panels. That should be a day of very heavy AC use with minimal solar power. With good solar in a day, that'll keep everything charged up. At worst, parking in the shade or overcast and hot, A/C use would go down some, but little recharging there. I can always break out the generator once a day for a few hours.
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Thankfully the ambulance is really well insulated sprayed , i am looking into a mini-split if you have any recommendations?
I think I’m going to hold off on the solar for now and try to recharge off alternator and shore power I wish they had a system that would allow to recharge off the Tesla stations .
So far I’ve started to install battery bank then going to work from there .
I really appreciate your input , thank you so much .
 

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So, one thought while holding off on solar mounts on the vehicle, you can still pretty easily do portable solar. A Victron 100/20 is pretty low cost, add in a couple of 220w portable panels which don't take up all that much space. Now, that is not going to handle your electrical needs, but it'll offset some of your power use. And you can continue using it in the future, even once you do get PV on the roof of the camper. Or you could go with even bigger portable panels, but that could be kind of unwieldy, and take up a fair amount of storage in an ambulance.

How much power do you need? What are you powering? I have a soft spot for Victron stuff. The Multiplus II 3000 might be what you need, or if you need more power than that, than the Multiplus II 5000 might be the way to go. That gets you 2400w or 4000w of power for 120v.

If you can find a 48v DC minisplit, I'd go that direction, over an AC powered one. It would be more efficient. You could also do a 12v DC minisplit and use a 48v to 12v DC-DC, though that would be less efficient. There are a number of 48v DC rooftop and mini-split options out there. I can't particularly recommend anything, only because I have not researched them at all. Also going DC powered, lightens your AC load.

If you are only doing DC-DC charging while driving or shore power to recharge your battery bank, I'd look more at the Multiplus II 5000, because of the higher amperage battery charging capability it has. That said, it also has slightly higher idle power draw over the 3000, though the difference is pretty minor.

A last note, DC-DC charging off the alternator is going to greatly reduce your fuel milage of the ambulance. No free lunches. If you add an alternator, that is additional parasitic drag and drag when it is pulling current. Pulling off the existing alternator might over tax it, so you may need to look into a larger alternator. I know nothing about the power train and alternator in that rig, so I can't speculate as to what the alternator could handle. Most, even in passenger cars would be just fine supplying 20 amps at 12v, probably even 30 amps at 12v. Many might start struggling at more than that at idle. And you'd need a 12v to 48v (or 24 to 48v? Is that a 24v vehicle system in the ambulance?) DC-DC charger, or install a 48v alternator.

Anyway, assume you are drawing about 3-4hp to idle that big engine. Putting a 1000w load on the alternator (20amps at 48v) to charge the battery bank is going to consume about 50% more idle fuel and even at highway speeds, is likely to see a 3-5% reduction in fuel economy. If you want to recharge at reasonable rates, you probably need around a 50 amp, 48v alternator at a minimum (or 200 amp 12v). At full draw that is going more than double idle fuel consumption and probably knock your highway fuel economy by 10+%.
 
azazel1024 said:
So, one thought while holding off on solar mounts on the vehicle, you can still pretty easily do portable solar. A Victron 100/20 is pretty low cost, add in a couple of 220w portable panels which don't take up all that much space. Now, that is not going to handle your electrical needs, but it'll offset some of your power use. And you can continue using it in the future, even once you do get PV on the roof of the camper. Or you could go with even bigger portable panels, but that could be kind of unwieldy, and take up a fair amount of storage in an ambulance.

How much power do you need? What are you powering? I have a soft spot for Victron stuff. The Multiplus II 3000 might be what you need, or if you need more power than that, than the Multiplus II 5000 might be the way to go. That gets you 2400w or 4000w of power for 120v.

If you can find a 48v DC minisplit, I'd go that direction, over an AC powered one. It would be more efficient. You could also do a 12v DC minisplit and use a 48v to 12v DC-DC, though that would be less efficient. There are a number of 48v DC rooftop and mini-split options out there. I can't particularly recommend anything, only because I have not researched them at all. Also going DC powered, lightens your AC load.

If you are only doing DC-DC charging while driving or shore power to recharge your battery bank, I'd look more at the Multiplus II 5000, because of the higher amperage battery charging capability it has. That said, it also has slightly higher idle power draw over the 3000, though the difference is pretty minor.

A last note, DC-DC charging off the alternator is going to greatly reduce your fuel milage of the ambulance. No free lunches. If you add an alternator, that is additional parasitic drag and drag when it is pulling current. Pulling off the existing alternator might over tax it, so you may need to look into a larger alternator. I know nothing about the power train and alternator in that rig, so I can't speculate as to what the alternator could handle. Most, even in passenger cars would be just fine supplying 20 amps at 12v, probably even 30 amps at 12v. Many might start struggling at more than that at idle. And you'd need a 12v to 48v (or 24 to 48v? Is that a 24v vehicle system in the ambulance?) DC-DC charger, or install a 48v alternator.

Anyway, assume you are drawing about 3-4hp to idle that big engine. Putting a 1000w load on the alternator (20amps at 48v) to charge the battery bank is going to consume about 50% more idle fuel and even at highway speeds, is likely to see a 3-5% reduction in fuel economy. If you want to recharge at reasonable rates, you probably need around a 50 amp, 48v alternator at a minimum (or 200 amp 12v). At full draw that is going more than double idle fuel consumption and probably knock your highway fuel economy by 10+%.
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Great ideas I never though about looking into seeing if they have a 48v mini split !
from what I’ve read victron is the way to go so you would suggest the multipllus 2 , what else should I be looking for besides the second alternator ?

I don’t need a crazy amount of power at once I was thinking more time away from charging . The A/C will be on most of the time since I live in south florida
 
I don’t recommend a 48 volt minisplit.

A quick google search reveals them to be about four times the price of a regular unit for a possible marginal savings on power.
EvergladesRoamer said:
I don’t need a crazy amount of power at once I was thinking more time away from charging . The A/C will be on most of the time since I live in south florida
Click to expand...
please look at a power requirement. I do think AC on most of the time is a crazy amount of power. I layout 900 watts of panels and it’s about 35’ x 2’. That may run your AC if you move the panels into the sun three times a day.
 
chrisski said:
I don’t recommend a 48 volt minisplit.

A quick google search reveals them to be about four times the price of a regular unit for a possible marginal savings on power.

please look at a power requirement. I do think AC on most of the time is a crazy amount of power. I layout 900 watts of panels and it’s about 35’ x 2’. That may run your AC if you move the panels into the sun
Click to expand...

chrisski said:
I don’t recommend a 48 volt minisplit.

A quick google search reveals them to be about four times the price of a regular unit for a possible marginal savings on power.

please look at a power requirement. I do think AC on most of the time is a crazy amount of power. I layout 900 watts of panels and it’s about 35’ x 2’. That may run your AC if you move the panels into the sun three times a day.
Click to expand...
Thank you , I think I will go with a regular home mini split then .
I appreciate your advice
 
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