Transition from existing 24V system to new 48V Inverter for complete off grid system

[JenLangan]

Hiya solar folks!

My Magna Sine MS4024PAE from Magnum Energy has failed and I’m in the market for a split phase 120 VAC/240 VAC 48V inverter. PV is 1.8 kw and I have four 12V agm 200ah batteries. Looking for an inverter that can handle inductive loads (washer, blender), access to data logs, ability to connect with wifi. I was looking into Outback Radian GS 4048, Schneider SW 4048, but it has 3800 watt output. Growing the system in the future, I would be interested in 4000-5000 watt output inverter. I want to use all my existing components. Starting off with the new inverter, I would setup my four agm 200ah batteries in series (48V 200amps) with incoming PV energy of ~65-70watts going into Midnite CC 150, also AC input from generator to inverter. Would this setup be enough to keep the system balanced? Do I run any risks of frying the batteries or inverter?

[MichaelK!]

I have the SW4024 in my workshop, and it runs all my power tools without complaint, including a 1.6hp air compressor. So, I don't think it's brother, the 4048, wouldn't handle the loads you mention. Have you ever done a power audit to itemize what it is you power? What would an audit of the future look like? More freezers? Air-conditioning?

For my cabin though I have Schneider's XW+, which runs my 1hp well-pump. That also handles all loads without blinking.

I do think though that 200Ah is a bit small for the size range you are talking about. Not knowing the max discharge rate of your particular battery, I'd say go by the max charge rate, which most likely is 1/5th of C, or 0.2C. That works out to be less than a 2000W load. I think you are better balanced with at least a 400Ah battery for the loads you think about. Both Trojan and Rolls make L-16 sized AGMs in that Ah capacity.

But, why AGM? Overpriced for less capacity, with a shorter lifespan. I'd say unless you have a compelling reason to keep AGM you should go with flooded lead-acid.

You should also be increasing your solar array. 1800W is really too small for a 48V battery. Assuming you only get 85% of nameplate output in real-world conditions, that means (1800W/50V charging) X 85% = 30.6A. Assuming your Classic150 can handle 83A with a 48V system, that works out to be (83A X 50Vcharging)/85% = 4480W of panels.

Assuming a L-16 in the 400Ah range wants charging in the 50A range, then what you really need is (50A X 50Vcharging)/85% = 2940W, not quite double what you have now. I myself like to overpanel, so for my 48V L-16 bank, I started out with 4500W of solar.

[jflorey2]

I have the SW4024 in my workshop, and it runs all my power tools without complaint, including a 1.6hp air compressor. So, I don't think it's brother, the 4048, wouldn't handle the loads you mention.

The SW series is a great inverter. However they are not 240V.

I'd say unless you have a compelling reason to keep AGM you should go with flooded lead-acid.

If his battery bank is inside, AGM or gel are better choices than flooded.

[jflorey2]

I was looking into Outback Radian GS 4048, Schneider SW 4048, but it has 3800 watt output.

Both of those are hybrid inverters, intended for both grid tie and backup. If you don't need hybrid I'd avoid those since they add cost.

I have had good luck with the Renogy 3500 all-in-one but it is only 3500 watts. You might consider the EG4 6500EX-48 - it will have power to spare, and has two solar MPPT channels so you can handle the inputs from two disparate arrays (different S/P arrangement, different manufacturers, different orientations.) With your Midnite you'll have three MPPT channels available.

Your batteries will be fried (or not) depending primarily on how low you take them. You have, realistically, 8kwhr of batteries if they are somewhat used, so as long as you don't use more than 4kwhr a day - and as long as you fully charge them every day - you should be OK, and could get a few years out of them. With 1.8kw of solar, in the summer you should be fine. In the winter you may want to add panels or run your generator regularly.