Planning Ambulance RV solar sys. Need critique. please

[JMP]

Hello. I am planning an Ambulance RV conversion solar system that will power some high-wattage items like a 9000BTU mini-split AC and a small microwave. This is my first full solar system set up. I have some experience with automotive DC wiring, but not much with residential AC electrical. Below are the components I'm planning on using. Please let me know if I've mis-matched or made any bad choices. THANK YOU

MPP all-in-one inverter/charger. 24V 2.7kW Model

PIP 2724LV-MR 24V 2.7kW 120V Inverter, 750W Solar Input, Easy DIY, No 120V Wiring! – Watts247 Wholesale

watts247.com

4x 250W solar panels (total 1000W)
Undecided on brand/model, but I'm considering these if I can make them fit:

Used SanTan 250W Solar Panel | SanTan Solar

store.santansolar.com

1x EG4-LifePower4 Lithium Battery | 24V 200AH

EG4 LifePower4 Lithium Battery | 24V 200AH | Server Rack Battery

EG4 Lithium battery 25.6V (24V) 5.12kWh with 200AH internal BMS. Made of UL Listed Battery Cells. Off Grid Solar Batteries - Off Grid System - Solar Batteries for Home - Lithium Solar Batteries - Deep Cycle Solar Batteries - Power Reserve - Solar Panels Plus Battery - LifePo4 - LifePower4 - Life...

signaturesolar.com

A few things I have not yet learned is:
- what's the best way to tie in the 24v battery to the 12v vehicle. I know this can be done with a "step-down" unit, but is there a better method used in solar-vehicle applications?

- How do you tie in the vehicle's alternator so that it can supplement the battery charging while driving? Can this just be spliced in to the MPPT input or is additional componentry needed, like a separate DC-DC charger connected straight to the battery?

- Can the solar system also top off the vehicle's AGM starting batteries or would this require a separate charger with a different profile, etc?

Thanks for any tips/pointers/corrections on this idea!

 

[corndog]

You might be able to save some space by going with new panels, like two of their 390w could end up being about the same output as what those four used panels are putting out.

You'll need a DC-DC converter, Victon makes a nice one.

I'd keep the vehicle's 12v system separate from anything you're trying to do with your solar kit.

 

[jberger]

Do you have the bus yet?
Most of them are already wired with high output alternators, inverters, etc
So you need to figure out what you have before you invest in new gear.

Fwiw, I’ve never seen an ambulance come with a working battery bank, so don’t believe them if they tell you it works!

 

[JMP]

Do you have the bus yet?
Most of them are already wired with high output alternators, inverters, etc
So you need to figure out what you have before you invest in new gear.

Fwiw, I’ve never seen an ambulance come with a working battery bank, so don’t believe them if they tell you it works!

Thanks for the good advice. It has a high-output alternator. It has an inverter, but is only 1050W, so it will be removed. It has a couple of AGM batteries that will be replaced with Lithium. I'll be retaining the wiring, relays, etc. The seller is a close friend of mine for 15 years who runs an ambulance service back east. So, luckily I don't have any doubts about what I'm getting. I really just want to make sure the components I listed above will work together and that I've made good choices and also what other components I will need (aside from the obvious basics like busbars, fuseblocks, breakers, etc).

 

[JMP]

You might be able to save some space by going with new panels, like two of their 390w could end up being about the same output as what those four used panels are putting out.

You'll need a DC-DC converter, Victon makes a nice one.

I'd keep the vehicle's 12v system separate from anything you're trying to do with your solar kit.

Thanks, good advice on the panels. For the DC-DC charger, would I just connect it to the battery the same way that the MPPT charger is or do they interfere with one another? Do I need a switch so only one charging source runs at a time or can they both concurrently charge the batteries?

 

[corndog]

Was referring to the DC-DC converter for using a 24v battery to power your 12v devices. You connect your 24v battery to it and then power your 12v devices from it. For a DC charger, that's just done with your solar charge controller, so your solar panels connect to your charge controller, then your charge controller connects to your battery, then off of your battery you'd connect your 24v to 12v DC-DC converter. I would not mix the solar setup with the vehicle's charging system, which means I wouldn't try to use the alternator to charge the solar batteries. Just keep them separate, the vehicle has it's own battery for vehicle things, and you have your solar battery for powering things. I wouldn't try to make them into friends.