Maximum PV for Battery

[WorldwideDave]

I want to use the maximum amount of energy from my battery as safely as I can, maybe for 3-4 days a week.

It is a Chins 2560 Watt hour deep cycle LiFePO4 at 12.8V at 200 Amp hours. From battery maker web site:

Standard charge current: 50A
Charging time: Approximately 5 hours
Max continuous charge current: 100A
Max continuous discharge current: 200A
Peak discharge current: 600A (Duration: less than 3 seconds).

So to be safe, no more than 200 Amps out (discharge?) which is a lot I think?

I was leaning towards a 2200 watt inverter from Giandel. Open to suggestions. Although it has its own solar charge controller, I was going to do something else.

I see that the battery can support up to 100 amp max continuous charge. 100 amps at 12.8V is 1,280 watts.

I am seeking a recommendation on solar panels and a solar charge controller. I understand for example if I did 320 watt panels and 4 of them in parallel I might be able to get 100 amps but the solar charge controller for that would be stupid expensive. I believe I could find 2 solar charge controllers that do 50 amps each and run both solar charge controllers to the battery buss.

However I am also concerned that there aren't any 320 watt panels that work in that max 24v range for a solar charge controller.

I am open to all thoughts and suggestions.

Of course, I could add a second LiFePO4 battery and do this all 24 volt and have greater benefit, but for now looking to see what I can do for the setup I have.

Loads right now are just running a home office. Ran a desk fan today and that was great. However I will be wanting to do things like an efficient electric ceramic heater or a refrigerator or possibly a portable air conditioner or window air conditioner or mini-split in the not too distant future. But for now, just lights, laptop, desk fan, etc. Thanks.

If you have specific name brands and the model name (example: Renogy Rover 40A) or links to those on amazon or elsewhere, that would greatly help too.

Love this forum!

 

[Ampster]

If you expect to get 2200 Watts out of that inverter at 12 volts you are going to need at leat 183 Amps. If you have a good southern exposure you can probably get by with 2kW of solar panels depending how much you deplete the batteries overnight. Run a scenerio in PVWatts to see if that will be enough in the winter.

 

[WorldwideDave]

If you expect to get 2200 Watts out of that inverter at 12 volts you are going to need at leat 183 Amps. If you have a good southern exposure you can probably get by with 2kW of solar panels depending how much you deplete the batteries overnight. Run a scenerio in PVWatts to see if that will be enough in the winter.

I forgot - I guess I could do something like:
one MPPT rated at 50 amps or 60 amps
four 320 Watt panels
Connect panels in 2 series, 2 parallel to cut down amps.
However, I think the solar charge controller, while it could handle the PV input, would never output close to 100 amps, so I would be in a situation where 50 amps max would come out of my PV.

I appreciate your reply very much.

I am in southern california. The site for NREL?

 

[WorldwideDave]

Lat, Lng: 33.85, -118.38
1.2 mi
that is close to where the installation would be. I have 300w panels (200+100 in parallel) there today.

 

[WorldwideDave]

Also for the record I don't know that I need to get 2200 watts out of the inverter...what I need is the ability to do that for several hours a day, but not all day. I want to have the capability to do so, but that doesn't mean I will for a while. I just don't want to do what so many people do: Buy a setup for 'now' and not plan for 'later'.

 

[Ampster]

You really need to calculate your loads and divide them into daytime and evening. The evening loads are how much battery capacity you will need. The daytime load plus charging the battery for the evening loads is how much solar you will need. Yes PVWatts in the calculator on the NREL site. I am familiar with that zip. I used to live there, and south of there for close to sixty years.

 

[WorldwideDave]

Hi then, former neighbor
Okay - here goes:
200 watts in use from 8AM until 4 PM. That's 8 hours at 200 or 1,600 watts 'morning'.
1500 watts A/C starting at 4 PM, ending at 10 PM. it will cycle on and off for sure, but let's say 1200 watts for 4 hours, or 4,800 watts. Haven't decided on A/C device yet, just estimating.
So 6,400 total. With a 2560 Watt Hour battery
Obliviously, I will need more capacity for those cloudy days, and I can always add batteries. But for now, the priority is figuring out the MPPT/SCC, the paneling (250 watt panels times 8 panels for 2000 watts is intriguing, but I would prefer fewer panels at same price if possible).

 

[Ampster]

.....I will need more capacity for those cloudy days,

You will need more battery capacity just to get through the evenings. I would consider larger panels also because they are less per Watt and less racking per Watt. You can always use several MPPT charge controllers. You will want to match their specs with the panels. Voltage is the critical number not to exceed on the charge controller. The controller will only pull the current that it needs to charge your batteries. You may want to consider 24 volt or 48 volt batteries, which will give you more options in inverters, batteries and charge controllers.

 

[WorldwideDave]

For now, trying to get the most out of what I have. So if that means I find 400watt panels first, then Solar Charge Controller that supports 12v (many do 48v/36v/24v/12v combo) then I can go that way. I can add a second battery at some point but for now need to use what I have.