A little help on creating a simple system

[AT1(AW)]

I just splurged on what I thought was a great deal, but don't want to get ahead of my skis.
Just received 4 Power Queen 200 ah Plus (200 amp bms) Lifepo4s for about $550 ea.

While just starting into the world of solar, I do have a Rich Solar 600 watt system with 2 Weize 200ah 100amp bms batteries feeding a 2000 watt inverter running a 20 cuft. refrigerator.

I have a few questions, and also looking for suggestions. Still up in the air about what I'm going to do with the new batteries, but thinking about a 2S2P setup for them. It will be a bit before I can afford the solar/inverter system for them. I know this is a silly way to do things, but can't spend 30K on a complete roof top system.

My first question is about initial charge (I used solar for the Weize). After research I keep running into the phrase "constant voltage, constant current". A charge controller will regulate V, but not I. Will it be OK to do an initial charge with my current solar system? Or do I have to buy an AC charger, and if so how big (20A, 40A, or bigger)? I have a 4.5 amp charger, but that will take days.

Next question, 4P or 2S2P I'm just hoping to run appliances, lights and emergency backup, that should only draw about 50% of the 10 Kw available from the batteries daily. And be able to recharge daily. I live in SoCal, so get some good sunshine. I can get about 1.5 to 2 Kw this time of year out of my 600W system. Would love to put all 6 btts together, but guess that's a No No.

Looking for size and component ideas on fairly good but not to expensive solar system/inverter components.
Some of my ideas

A 2.5 to 3 Kw all in one inverter charge controller.

A complete kit from Rich Solar, Renogy, or somebody else.

This inverter https://www.amazon.com/dp/B0BXS1VGM7?tag=track-ect-usa-817885-20&linkCode=osi&tht=1

Also thinking used or refurbished panels, not looking for a lifetime system. I'm over 65 and not needing decades worth of use.

There is so much out there, hoping for ideas.

More to follow, but I will quit for now.

 

[DIYrich]

What voltage is the batteries?

If you are short on cash, panels and inverter would be the best first expenditure. They provide immediate savings you can use to reinvest in more equipment.

I assume you are grid tied? If so, you may need UL listed CA approved inverter.

 

[AT1(AW)]

The Batts are 12v and I am thinking 12 or 24 volt for the system. What I am looking at is to small for grid tie, and have a couple various thought on what I going to do with the battery power.

 

[DIYrich]

Off grid growatt is pretty good.

 

[Rednecktek]

MPP tends to be well regarded and "Just Work" and are pretty fair priced. Growatt is also a decent option.

 

[AT1(AW)]

Helpful , but right now my main question is run the 4 Batts in parallel for 12v or a 2S2P for 24v. I know total wattage will be the same, but smaller wires for 24v. I'm probably only looking at a 2 or 3kw inverter. Is one way better than the other other than that?

 

[rodrick]

Helpful , but right now my main question is run the 4 Batts in parallel for 12v or a 2S2P for 24v. I know total wattage will be the same, but smaller wires for 24v. I'm probably only looking at a 2 or 3kw inverter. Is one way better other than that?

Anything over 1500 watts is better at 24 volt and 24 is good to about 3k over that you would go 48 volt

you may also want to put a balancer unit on the 2s sets just to keep thing running smoothly if you go that way

 

[Q-Dog]

I don't like to put LiFePO4 batteries in series. If you want to build a 24 volt system use 24 volt batteries.

 

[DIYrich]

3000 watts at 12v is 250 amps. That is 1/0 to 2/0 range. At 24v, you can drop the wire size down to 4 awg range.

The specs say that up to 4 batteries in series. If you have any intention of expanding the system, I would start with a 48v system.

 

[Tomthumb62]

Not to beat a dead horse and I have no personal experience with it, but do reconsider putting those batteries in series. If you do, read up on how to maintain them. The problem is they will get out of balance over time and need to be rebalanced or you will have bigger problems and could damage the batteries. You can do the rebalancing manually but a device can do it for you (cost I think is $100-200, but don’t quote me on that). And you’ll need to confirm that the device is actually working properly. I think Victron makes one and I would tend to go with that.

Or you can save yourself some hassle a just buy a 24v battery to begin with. Or stick with a 12v system. Yes the thicker wires and cables are more expensive with 12v, but if you intend to stick with a 2500w or less inverter (or even better have multiple smaller ones), and since your system is small, you might just be better off staying 12v since you went ahead and bought all those batteries. To return them or sell them, you’ll be at a loss, financially speaking. Unless you can return them and they pay for shipping.

One advantage of multiple smaller inverters is likely you don’t need all of them running all the time. Say you only need a 1000W inverter to run your fridge, and keep that one on 24/7. But unless you power your microwave all the time, that inverter can be remotely powered on and off with a switch placed next to the microwave. But unless you have a small microwave, you WILL need a big inverter to run it. And big inverters have a very high idle draw. Idle draw is the power used just to keep the inverter powered on. Even if the inverter isn’t powering anything, it’s consuming energy to be ready to do so. An efficient 1000W inverter might have an idle draw of 7-9W, but a 3500W one might be 40-50W. 40W x 24 hours = 960 watt hours. A single 12v 100Ah lifepo4 contains 1280 watt hours, so you’ll end up using 75% of a single 100Ah battery every single day just to keep the inverter powered on. It’s essentially wasted power since you only run a microwave for a few minutes every day.

We have a very small system in our off grid camp trailer. We went from a 2000W Renogy inverter to a 1000W Victron. It’s mostly to power our fridge, so it needs to be on 24/7. Our idle draw on the Renogy was about 500Wh (about 40% of a 100Ah battery), but the Victron uses a measly 50Wh (4% of a 100Ah battery), on eco mode. If we turn off eco mode, it uses about 16% of a 100Ah battery. In our case, we realized that 2000W inverter is very much overkill for our needs. And the super beefy transformer of the 1000W Victron can power most anything the 2000w Renogy can. In fact, the Victron is actually heavier than the Renogy due to the massive transformer!

 

[AT1(AW)]

Wow, 500 Wh, glad I went with Rich Solar, my 2000 watt inverter draws a little over 150 Wh a day. I do like the idea of multiple inverters. I was thinking about a 3000 watt inverter, but maybe I'll stick with 2K. I am trying to work out a return on the PQ Batts, but if not I will figure out something.

 

[AT1(AW)]

Now the conundrum. PQ offered me a return on the batteries, but they were such a good deal I don't know whats do. Tieing into the house non grid is sketchy at best. Thinking I should just skip the whole thing and be happy with a solar powered refer and emergency backup.

 

[rodrick]

Now the conundrum. PQ offered me a return on the batteries, but they were such a good deal I don't know whats do. Tieing into the house non grid is sketchy at best. Thinking I should just skip the whole thing and be happy with a solar powered refer and emergency backup.

If you are living in housing tying in could be very problematic if you own or rent not such a problem you could have a critical loads panel running specific items with grid backup fairly easily

 

[DIYrich]

Now the conundrum. PQ offered me a return on the batteries, but they were such a good deal I don't know whats do.

For $2,100 you may be able to diy a 280ah 48v battery. The pq is a decent deal if that is what you need.