Check my facts and my math- 48V system in a van for under $3K ?

I'm doing a Sprinter conversion and I live in the South- I must have air conditioning. I looked at a lot of options including generators but i think i have arrived a the right plan.
Will Prowse endorses a 48V 100amp rack battery from Trophy for around $1900 delivered.

A decent 2000 watt inverter is $400.
The cool part is charging- 13 amp Li 48V golfcart charger is cheap and will return about 650 watts per hour, off the alternator through a 12V inverter. I may drop down to an 8 amp charger to keep the strain off the alternator but that's still a lot of watts.

Solar will be part of the equation eventually but right now this vehicle needs to drive all day, and keep my family cool all night.

I'm fluent in ohms law but this is new to me, do i have this right ?

hertfordnc said:

I'm doing a Sprinter conversion and I live in the South- I must have air conditioning.

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Can you quantify this load? How many amps does it pull on a hot day? How many hours a day do you want to run it?

Understand the load and all else falls into place.

Also - very important! What are the Locked Rotor Amps needed to start the A/C. You will probably need to install a SoftStart type device.

Leeds said:

Can you quantify this load? How many amps does it pull on a hot day? How many hours a day do you want to run it?

Understand the load and all else falls into place.

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The load is a Midea U-shaped window unit that will be mounted on the rear door. It draws 800 watts running at full power. The van will be well insulated and we'll only need AC for sleeping and when we leave the dog. So i'm thinking on a hot night it will run at full power for a couple hours and then drop to 400-500 watts. for a total of 4600 watts. I think that's worst case. Camping in florida in summer with a tent trailer the AC did shut during the night.

Rocketman said:

Also - very important! What are the Locked Rotor Amps needed to start the A/C. You will probably need to install a SoftStart type device.

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Probably not- 8000 btu AC pulling 800 watts, i can't imagine the startup load to be more than 12 amps- it's plugs into a 15 amp outlet. The battery and a 2000 watt inverter should be able to handle it.

It appears that you have done your research and have a basic understanding of the components needed for your van's 48V electrical system. However, to ensure the accuracy of your calculations and to ensure that your system will meet your needs and expectations, I would suggest consulting with an experienced electrical professional or further researching the components and specifications of the specific items you plan to use. Some factors that may affect your calculations and overall system performance include the power consumption of your air conditioning unit, the power output of your alternator, the capacity and voltage of your battery, and the compatibility and efficiency of your charging components. Additionally, factors such as local regulations, safety considerations, and the durability of your components should also be taken into account when planning your electrical system.

hertfordnc said:

I'm doing a Sprinter conversion and I live in the South- I must have air conditioning. I looked at a lot of options including generators but i think i have arrived a the right plan.
Will Prowse endorses a 48V 100amp rack battery from Trophy for around $1900 delivered.

A decent 2000 watt inverter is $400.
The cool part is charging- 13 amp Li 48V golfcart charger is cheap and will return about 650 watts per hour, off the alternator through a 12V inverter. I may drop down to an 8 amp charger to keep the strain off the alternator but that's still a lot of watts.

Solar will be part of the equation eventually but right now this vehicle needs to drive all day, and keep my family cool all night.

I'm fluent in ohms law but this is new to me, do i have this right ?

Click to expand...

You'd be better off with a 12v or 24v battery, 3kw inverter charger, and a dc-dc charger IMO. That being said there's no reason what you proposed won't work, but you're locking yourself into a really convoluted setup with that 48v battery. I went 48v on my class C as well, but I didn't even consider alternator charging. If I were relying on alternator charging I would go 12v or 24v.

Scar said:

You'd be better off with a 12v or 24v battery, 3kw inverter charger, and a dc-dc charger IMO. That being said there's no reason what you proposed won't work, but you're locking yourself into a really convoluted setup with that 48v battery. I went 48v on my class C as well, but I didn't even consider alternator charging. If I were relying on alternator charging I would go 12v or 24v.

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You might be right. 24V might be better. I was really attracted to the Trophy server rack battery and Will Prowse gushing over it. Alternator charging is critical to this plan. In my mind a 48V charger at 8 amps is better than a 12V charger at 32 amps. But 24V at 16 amps might be a good compromise.

To answer one possible question in the simplest way possible:

YES, you can absolutely air condition the interior of an (insulated..) Sprinter van during the no-sun hours, with 5kwh of battery. I am able to air condition my house bedroom with that same Midea on less than 2kwh per night even during the Texas Summer. I am able to air condition my 23' RV overnight with a regular 5000btu window unit with 5kwh of battery, don't know what i use but probably similar ~2kwh.

So yes i've done almost the exact thing you're talking about and it will work.

Voltage and capacity are different things. You can have 5kwh of battery at 12v if you choose to. That's what i have in my RV. It does simplify some things, especially 'alternator charging'. If the Midea is your biggest AC load you will not need a particularly large inverter or cabling. 48v generally only justifies itself when it requires large cable sizing or multiple parallel battery strings to support a given wattage of load on a smaller voltage, and being able to put more batteries in series and shrink your wiring ends up saving a ton of money and hassle. I don't see a need for 48v specifically in your case. 12 or 24 would be fine.

Vigo said:

I don't see a need for 48v specifically in your case. 12 or 24 would be fine.

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Yeah, I'm coming around to that. At 12V I have the option of a 40 amp DC-DC charger.

Thanks for confirming my hunch on the Midea.