How to run 12 volt on 48 volt system?

[Rednecktek]

I know this will probably get me lynched for saying on a DIY forum, but have you thought about a Pecron E-2000LFP and maybe an expansion battery or two? Smaller form factor, 2Kw inverter, all the ports, reasonable solar input, expandable, and pretty well reviewed. A bit pricier than doing a DIY setup but it's WWAAYY less complicated.

 

[Rednecktek]

Ok. So it will dictate battery, solar panels, and potentially charging from shore power, but if EG it becomes better to go to 24v for the instant pot then the buck converter does not need to be so big.

Exactly, hence the power audit to tell you what you're going to need.

 

[zanydroid]

Another thing regarding batteries is that it may not be as easy to downsize a 48V system without going to a less common cell size. EG I know 100ah cells are super common but if connected to form 48V you are forced to have a 5kWh battery.

For 24v you can have either 2.5 or 5

For 12v you can have multiples of 1.25

This is irrelevant I guess if someone weighs on saying 50ah cells are just as good but I only saw some smaller brands using them when I was shopping around.

 

[zanydroid]

I know this will probably get me lynched for saying on a DIY forum, but have you thought about a Pecron E-2000LFP and maybe an expansion battery or two? Smaller form factor, 2Kw inverter, all the ports, reasonable solar input, expandable, and pretty well reviewed. A bit pricier than doing a DIY setup but it's WWAAYY less complicated.

IMO if space or weight is at a premium then the packaging of this form factor makes sense.

 

[bgrieves1]

Okay, the Pecron E-2000 will be fine. Thank you

Another thing regarding batteries is that it may not be as easy to downsize a 48V system without going to a less common cell size. EG I know 100ah cells are super common but if connected to form 48V you are forced to have a 5kWh battery.

For 24v you can have either 2.5 or 5

For 12v you can have multiples of 1.25

This is irrelevant I guess if someone weighs on saying 50ah cells are just as good but I only saw some smaller brands using them when I was shopping around.

I dont understand this......

 

[Rednecktek]

I don't understand this......

Every cell is 3.5v so if you have a 12v battery you have to use 4 cells. A 24v battery is 8 cells, and a 48v battery is 16 cells. The most commonly used cell is 100Ah (it's pretty much the cells used in almost every pre-made battery) so if you wanted something SMALLER than a full size rack you'd have to track down smaller cells like 50Ah which are harder to find and more expensive per amp hour of capacity.

So, say you grabbed some tiny little 4Ah cells for a really small package, even a battery that tiny takes 16 of them to get to 48v which is a significant size increase. A 24v version takes up half the space and weight of a 48v version.

It's a volume & weight thing. No matter how small the battery bank, there is just the fact that a 48v battery is going to require 16 cells of whatever size. It takes less space to make a 400Ah 12v battery than a 100Ah 48v battery because you only need 1/4 the physical cells. Same watt hours of capacity, physically smaller package.

 

[zanydroid]

It takes less space to make a 400Ah 12v battery than a 100Ah 48v battery because you only need 1/4 the physical cells. Same watt hours of capacity, physically smaller package.

Not sure this is right. Doesn't the 400Ah 12V battery use the same 16 cells, just in 4p4s (or whatever) instead of 16s? This can be indirectly verified by checking the weight. Also, the same chemistry will have the same specific energy (Wh per weight).

 

[Rednecktek]

Not sure this is right. Doesn't the 400Ah 12V battery use the same 16 cells, just in 4p4s (or whatever) instead of 16s? This can be indirectly verified by checking the weight. Also, the same chemistry will have the same specific energy (Wh per weight).

400Ah cells. 4x 400ah cells takes less space and weight than 16x 100ah cells. Larger cases require more material because it's physically larger.

My numbers are for napkin math learning concepts.

 

[KITROBASKIN]

Hopefully this is a good project for you in the sense you want independence rather than being forced into it. Sounds like a fun project.

Have you purchased those 12V products yet? Can they also run on AC power (like a refrigerator)?

Do yourself a favor and use that inverter. This will allow the efficiencies of higher DC voltage to power things beyond what you are thinking now. It could very well come in handy when you possibly set down roots in a future location.

We have a 24V 1200VA (watts, sort of) inverter that runs an induction cooktop at medium high setting; plenty hot to cook quick. Had to research it but found a 1000W toaster oven that works great from this portable system in our truck. An inverter microwave would be the way to go if you like those kinds of things with the limited amount of room you will have. Seems like InstaPot may provide more flexibility than a crock pot?

Energy savings gained from using limited kinds of 12V items really won't matter if you are keeping that inverter on all the time. In fact, I would research other inverters that have a lower stand-by power drain.

 

[JBertok]

I read through the other posts and didn't see it mentioned, so I am going to say that this being a mobile application should have an inverter specifically intended to be installed in a vehicle. A wall-mounted inverter not the right choice here due to vibration, cooling, and form-factor problems. I would be looking at something intended for a long-haul semi or an RV, like a Xantrex Freedom inverter or similar. They have a built in battery charger and transfer switch, designed to accept "shore power" as available, have a low idle draw, good surge capability, are compact, and are intended to be installed in fairly inaccessible spaces with remote panel control options available. Also, these inverters are 12 Volts, as has been suggested to stick with by many already. Server-rack batteries are not built to go up and down the road either.