48v/100ah vs 12v/400ah?

Leemaisel · Apr 5, 2020

I built a solar power system for
My full time RV, built around my 1300 watts of panels, they are 48v nominal, and I setup with four 100ah batteries wired in series for 48v.

Sadly, this gives me 100ah at 48v instead of 400ah, due to my misunderstanding.

Does it really matter??

I am using a 48v to 13.8v converter for the 12v things and an inverter for 110AC.

Should I be doing this differently?

kernel · Apr 5, 2020

No, it does not matter. It is equivalent. You did better likely with a system that size to just go 48v especially if you are just going to invert your power anyhow.

Johnmahon · Apr 5, 2020

48 volt system will serve you better in long run as well. Not to mention you don't need a thick of wires for the system to operate. Thus saving cost. In this case, the "misunderstanding" was a blessing in disguise.

Here is a good article to read:

Jamestown Distributors

www.jamestowndistributors.com

In his videos, @Will Prowse actually recommends 24 or 48 volts for his viewers. It was based on his advice that I did a 24v (Two 12v batteries in series) for my system.

Just make sure your inverter is designed for a 48v system and your stepdown is specifically designed for 48-12v stepdown conversion or you may blow all your fuses and/or ruin your "12v things".

Jm

MichaelK · Apr 6, 2020

Leemaisel said:
I built a solar power system for My full time RV, built around my 1300 watts of panels, they are 48v nominal, and I setup with four 100ah batteries wired in series for 48v.

Sadly, this gives me 100ah at 48v instead of 400ah, due to my misunderstanding.

Hello Lee
First, more details? When you say your panels are 48V nominal, exactly why do you say that? Is there a sticker on the back that says Voc=48.0? If that is the case, then yes, you made a mistake. If a sticker says something like Voc=48.0 and Vmp=37.5, then what you've got is a 24V grid-tie panel. That doesn't mean it's wrong, or you can't use it, it means that the panel by itself can NOT charge a 48V battery bank.

It's all doable with the right electronics, but we need to know the individual specifications to tell you how to do things right. Most likely you'll need an MPPT controller to properlly handle the voltage.

Forbisher · Apr 6, 2020

Leemaisel said:
Sadly, this gives me 100ah at 48v instead of 400ah, due to my misunderstanding.

48v/100ah vs 12v/400ah?
48v x 100A = 4800 watt hours
12v x 400A = 4800 watt hours
So they are the same capacity.

What brand of 100Ah batteries do you have?
What brand and specs on your SolarChargeController?

A 24 volt system was another option with your 4 12v batteries.

John Frum · Apr 6, 2020

Leemaisel said:
Sadly, this gives me 100ah at 48v instead of 400ah, due to my misunderstanding.

Does it really matter??

I am using a 48v to 13.8v converter for the 12v things and an inverter for 110AC.

There are pluses and minuses.
You could have omitted the converter if your system voltage was 12 volts.
To run a 2400 watt inverter at 12 volts the wire guage is going to be 2/0 which is getting pretty big.
For the same wire guage at 48 volts you can run a 9600 watt inverter.

Leemaisel · Apr 6, 2020

Thanks to all for calming my fears! I designed the system that way for two reasons, 1, wire gauge, and 2, the panels are sun power 48v nominal (50/60v)
I’m glad it worked out.

The batteries are hitachi 100ah, and I have a 48/13.8 dc/dc converter as well as a 48v/110ac inverter

The charge controller is a Chinese MPPT at 48v nominal as well. I ruined my first set of batteries (expensive lesson) when I created a short, and the charge controller reset, and sensed 24v system, panicked and proceeded to drain the batteries because it thought they were way over voltage.

Also, being a ham radio operator, this charge controller sucks. So noisy in RF!!

evad · Apr 6, 2020

Re the RFI Palomar has a write up on how to cut down on the noise. It is written just for solar systems.

tictag · Apr 12, 2020

Leemaisel said:
Thanks to all for calming my fears! I designed the system that way for two reasons, 1, wire gauge, and 2, the panels are sun power 48v nominal (50/60v)
I’m glad it worked out.

When using an MPPT charger it doesn't matter what voltage your panels are, only that any series strings are within your SCC's specs. Once-upon-a-time the panels's Voc matttered because MPPTs were quite expensive, meaning that a lot of people used PWM SCCs. A PWM SCC is basically just a fancy switch that connects the panel to battery, if the panel Voc wasn't higher than the battery, it wouldn't charge!

With an MPPT charge controller you can use any voltage panels, just series them all up to whatever your SCC can handle e.g. 150V/250V etc.

p.s. obviously if you're only using one, then, yes, it has to be higher than the battery voltage!

Edit: Added postscript. Corrected typo.

tictag · Apr 12, 2020

Surprised nobody has said, "Watts In = Watts Out" in this thread ... opportunity missed.

kernel · Apr 13, 2020

tictag said:
Surprised nobody has said, "Watts In = Watts Out" in this thread ... opportunity missed.

We are hoping if people are twisting wires and screwing down, pushing buttons and stuff, they get that part.

Yes, opportunity missed for sure.

48v/100ah vs 12v/400ah?

Leemaisel

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kernel

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Johnmahon

What's Your State of Charge?

Jamestown Distributors

MichaelK

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Forbisher

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John Frum

Tell me your problems

Leemaisel

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evad

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tictag

Off-Grid Enthusiast

tictag

Off-Grid Enthusiast

kernel

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