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Will going 48v be worth my while


Camel
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Hi All,

 

Need some advise please, Very new at this so please bear with me here.....

 

Current set up

 

8 by J305 6V in 2 strings of 24v 620AH

3KVA 24v Axpert Plus

4 by 300watt panels, adding 2 more in the next few days.Panels in strings of 2 

2 by Victron energy Bmv702

 

Max Amps pulled by the next morning is 125AH of the 620AH I have.

The washing machine, tumble dryer and dish washer still on Eskom.

 

If i just chanced the Axpert to 48v, my battiery bank would drop to 310AH, would my Amp drop in half to 62,5AMP in the morning? or am looking at this all wrong. Could I keep my panels connect the same way as i am only getting around 60V.

 

Would going 48V benefit me in any way???

 

cheer

 

 

 

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If i just chanced the Axpert to 48v, my battiery bank would drop to 310AH, would my Amp drop in half to 62,5AMP in the morning? or am looking at this all wrong. Could I keep my panels connect the same way as i am only getting around 60V.

 

Would going 48V benefit me in any way???

 

cheer

Hi Camel

 

Welcome to the forum.

 

You are correct your 620Ah battery bank would be

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Thanks Chris, ok that is making more sense. If I had to go 48V my batteries would charge quicker as I would have only used 60 odd Amp compared to 120 odd Amp to put back? Is this correct? If so I could maybe add more load on the system?

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. If I had to go 48V my batteries would charge quicker as I would have only used 60 odd Amp compared to 120 odd Amp to put back? Is this correct? If so I could maybe add more load on the system?

 

You would now need a higher voltage to charge your batteries .  Power (Watts) = Volts x current (Amp). So your Volts go up current comes down and you still have the same amount of power.

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Charge should take the same amount of time. You may charge at half the current, but at double the voltage, and P=VI. You're putting P back into the system, at half the I, but double the V, so there should be no change in overall P.

 

Another way to look at it, in 24V configuration you have 620Ah, or 14880Wh. In 48V configuration, you have 310Ah for the same 14880Wh. So no change.

 

Your question reminds me of the April fools joke. We were going to get some engineers from America to convert the grid in South Africa to 110V. That would double our capacity and we'd have no more load shedding... :-P

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Ok cool, I seem to be understanding it a bit more now,thank you guy's. but what is confusing me is, currently I am putting in 60 odd volts from the panels and 30 odd Amp per hour at peak. Now if I changed the Axpert to 48v and batteries whould I still get 30 odd amps per hour at peak from the panels?

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I assume you have an MPPT charge controller, or your inverter does. An MPPT charge controller uses a Buck Converter to step the voltage down efficiently. In stepping the voltage down, it steps the current up. Efficiency is usually above 80%, for really good converters it is above 90%. So if you have 60V and 12A on the input side of the Charge Controller, you will get 60*12 = 720W, say 90% is preserved, so you have 650W on the output side, at 24V, that's 27A. So 12A on the input, 27A on the output.

 

Now with a 48V system, you still start with 650W, but you only get 650/48 = 13A.

 

From another thread here, it seems the Axpert inverter reports the OUTPUT amps of the charge controller as "PV current", so what will likely happen is when you go up to 48V, you should see the 30A drop to 15A.

 

Law of preservation of energy. Ain't no blank cheques here... :-)

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