To Change or Not to Change: Oportunity to "Upgrade" from 24v to 48v ?

[Matrix]

Well after building my 24v system, I now wish I would have went 48v.

Today I found a guy who wanted an off grid system and was willing to purchase from me any parts I would sell. He was fine with a 24v system and was willing to pay me the purchase price less 5% for any pieces i wanted to part with.

So it got me thinking. I could sell he the pieces that would not make the transition to 48v and not be out that much.

My current 24v system consists of:
9 285w panels
1 Midnite Solar Classic 150
1 Schneider SW 4024 Inverter Charge
4 Trojan L16H AC 435ah batteries
And enough 4/0 cable for series connections and main connections

I could sell him the Inverter, Batteries, and cables ... and still use my panels and CC.

So wondering, would making the switch to 48v really be that big of a deal? Or am I just wasting time and money? I figure it will cost me about an additional $500 to make the swap. And it seems 48v would allow for some expansion of panels that I am currently unable to do as I have maxed out my CC.

I would get:
- Some Inverter that can do 240v split and deliver 3600 - 4000 Watts (not necessarily a Schneider SW 4048 - Suggestions? - I'll probably start a new thread if I get that far)
- 8 Trojan smaller batteries in the range of 229-260ah/20hr range. If I see things correctly, at the same daily load of Watts and Amps, a 229hr battery bank at 48v will last longer in daily discharging than my current 435ah battery bank at 24v. (Am I seeing Correctly?)

What would be the pros and cons of making this change?

[Mike90250]

the pro is you can get rid of the 4/O cable and use 1/O (2/O if you have long cable runs)
You can add more panels and not need an additional charge controller
If I was you, I would be very tempted to make a go of using 200Ah 6V golf cart batteries, 8 in series, giving you a 9600wh capacity, 4800wh usable @ 50% discharge

con :
you will will need a new inverter. I would recommend the XW series, very robust, but you do need either the SCP or Combox to make any adjustments (other house size inverters need an additional box to configure them too)

[neweclipse]

Trying to understand,, at 24V the CC is maxed for what? the string Peak Voltage? ...Not for CC Peak Wattage? Correct? What makes it Maxed Out?

Maxed out at Watts gets no change w/ doubling the voltage...it only cuts amps in half which still equals the Same Watts as before.


So being able to add panels is not "new found power from 48v", but rather a "rearrangment" to allow additional panels to utilize more of the CC's total capacity.

[Mike90250]

Trying to understand,, at 24V the CC is maxed for what? the string Peak Voltage? ...Not for CC Peak Wattage? Correct? What makes it Maxed Out?...

MPPT controllers are rated in Output Amps. The Classic is rated for about 90A in a 24V system, that could deliver a theoretical 100 amps, so that is what is maxed out at 24V

Re-wiring the PV array (hard with an odd # of panels, Matrix may want to add 3 more panels) to a 48V battery, would reduce the charge controller output amps to 50A, well under its limit

[littleharbor]

You will be able to double the size of your array when switching from 24 to 48 volts before you max out the output. Granted, you can overpanel most MPPT controllers and some people do in areas of questionable insolation. Your controller is only going to output what it's rated at. As far as voltage goes those points are not negotiable. You keep your string open circuit voltage in a safe range or kiss your controller goodbye.

[Matrix]

You will be able to double the size of your array when switching from 24 to 48 volts before you max out the output. Granted, you can overpanel most MPPT controllers and some people do in areas of questionable insolation. Your controller is only going to output what it's rated at. As far as voltage goes those points are not negotiable. You keep your string open circuit voltage in a safe range or kiss your controller goodbye.

With that said .... with an array of 2.5kw ... would I HAVE TO increase the array size if I am able to make the switch from 24v to 48v. My battery bank now is a 435ah, and if I go 24v I make do say a 220-360ah bank. Would my array need to enlarge to get fully charged in the same time period as 24v.

[littleharbor]

Say for example you had 2 strings of Golf cart batteries at 24 volts. and your array was sufficient size to properly charge you battery bank these batteries would give you around 420 to 440 amp hours. Now you combine these 8 batteries into one 48 volt string you end up with a 210 to 220 amp hour bank . You still have the same amount of watt hours, just at a different voltage. Your existing array wouldn't need to be enlarged. Your charging voltage would be double, but at half the amperage.
Given this and your scenario, I'd say no, you don't need to enlarge your array.

[Mike90250]

Array. a 48V bank needs to have about 65v available from the PV panels, to be able to properly charge

9 REC TwinPeak 2 Poly 285w modules connected 3S 3P (2,565 watts / 95.7 vmp

OK< after finding your specs, that would work, rare that folks can get by without re-wiring the array, lucky you.

Charging at 58V ( a common charging voltage ) you would get 44 amps, so that could support a 48v 400ah bank,