Guidance for HYBRID LV5048 Split Phase 120V/240V output 5kW 48V system

OK, so I made a mistake and bought some equipment before I had any understanding of what the heck I was getting into. I don't want to send anything back as I think we will eventually grow into this system by next summer. Right now we are living in an RV in Colorado while we build, and will be in the RV over winter. I want to get enough solar and storage going to make sure we can run the propane heater in the RV every night.

This is a place to put down notes as I learn and hopefully get some feedback if I am making egregious errors.

I have purchased the following:
(1) LV5048 5kW 48V Inverter
(4) 24V A123 LFP Battery Box w/ BMS

The manual for the inverter suggests at least 200aH of battery storage, and the battery bank needs to be 48V. My batteries are rated at 24V 92.8aH. So I need to connect (2) 24V batteries in series to get to 48V. Doing this with my 4 batteries now gives me (2) 48V 92.8aH packs. Putting these in parallel would give me 48V at 185.6aH. This falls below the recommended 200aH for the inverter. What are the drawbacks of only using 185.6aH? Need to research more about that. The solution would be to buy (2) more of the batteries, wire them in series and then add them in parallel, which would give me 278.4aH at 48V. But that means another $1800.

For panels, I am looking at the following panels:
Used 250W 24V 60 Cell Poly Solar Panels

The manual for the inverter states that the maximum PV array open circuit voltage is 145Vdc. This means I need panels that will stay under 145Vdc open circuit voltage? The listed open circuit voltage for the panels I am looking at is listed at 37.6V. This is obviously well under the inverter maximum. However, for solar panels to be able to charge batteries, the voltage of the panels needs to be higher than the voltage of the batteries. Since my batteries are 48V, the voltage of my solar panels needs to be higher.

Single panels in parallel will not give me high enough voltage. For the panels I am looking at to work, I would need to wire two in series. That would give me250W 75.2VOC on the panels. I think this VOC is high enough to charge the batteries but low enough to not damage the inverter.

In the video I watched about the LV5048, it was mentioned that only 400W at a time can be added in solar panels. Since the panels I am looking at are 250W, I am not sure how to proceed. I need to learn more about this.

There are two issues with smaller battery capacity. First is obvious you cannot draw more then battery capacity without any PV suppliment. A secondary part of this is maximum peak wattage you should allow. In parallel there will not likely be perfect current distribution balance so a good assumption is to treat 185 AH as if it was about 160 AH. This is not a problem as it is still more then inverter power rating. You're going to have about 7-7.5 kWH usable. Only you can judge if that is sufficient for your useage over given time without charging suppliment.

Second part, not well known, is what you pump through inverter with PV power. Some people put massive PV array with minimal battery capacity thinking they don't need the battery capacity because they have a lot of PV power. There is two problems with this.

PV puts out illumination variable but smooth DC current. Single phase AC is half sine wave shaped current profile at 120 Hz repetition rate for 60 Hz single phase. The panels should not see the AC power ripple as it will reduce their effective output. The averaging of the AC profile is usually done by batteries in a hybrid inverter. They are effectively a large filter capacitor for the PV power to AC power conversion. This creates a large ripple current on batteries. If batteries are not large enough to handle the ripple current it can degrade batteries. LPF batteries are better at taking this ripple current because they relatively low series resistance.

Second part of the large PV power / small battery issue is when a cloud goes by and much of the PV power drops outs. If you have a heavy AC load the batteries have to be able to, at lease during the drop in PV power output time, be able to take the heavy AC load power.

Get a good battery monitor that can keep track of the goes-in-to versus goes-out-off battery, charge-discharge tally. This will help keep you from overdischarging batteries. With random PV power suppliment and AC loading it is impossible to keep tabs without a good battery monitor.

I compliment you for at least reading the manual first and detecting the 200 AH minimum recommendation.

I am wondering if it might be better for now to buy an all in one 24V inverter that will get me through the winter. that would give me close to 400aH in storage and I could buy fewer panels.

jimjones26 said:

I am wondering if it might be better for now to buy an all in one 24V inverter that will get me through the winter. that would give me close to 400aH in storage and I could buy fewer panels.

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Not sure what your thinking is here. 24v 400AH is same as 48v 200 AH. Just maybe a bit worse inverter efficiency and more cable loss due to the higher current on 24v system for same AC power output.

RCinFLA said:

Not sure what your thinking is here. 24v 400AH is same as 48v 200 AH. Just maybe a bit worse inverter efficiency and more cable loss due to the higher current on 24v system for same AC power output.

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I'm not sure what I am thinking either.

So if I stick with what I have, how much solar input should I go for to make sure I am taking it easy on the batteries? We can limit our usage until I can buy more batteries and panels.