Solark 15K Using 2 Different Types of Batteries at once

[XILLA]

Noobie Q: I have a Solark 15K, currently powered with only 6K of PV, and charging 25Kw worth of EG4 Lifepo4 Batteries. I am in AZ with a large all electric home (two 3 ton HVAC (Both with MicroAir easy starts), Oven, stove, well pump, booster pump, 40,000 gallon swimming pool, separate spa, washer, dryer, and dishwasher.)

Currently the Solark is set up to run a sub-panel which only powers my 110v loads and the well pump and booster pump. I do have it set up as "Limited Power to Home" and since I don't have an interconnection agreement with APS, I installed CT's and am able to almost completely zero out my meter through careful daily management of my loads (for example the bedroom HVAC runs at night and shuts off during the day, the spa only runs during solar hours, the pool only runs during solar hours, we only use the dryer during solar hours, etc.)

From October to April in AZ, and during the hours of 10am to 3pm the per Kwh charge is less than $.04/kw, so we only use the grid to bring the batteries up to 75% during this time frame as it is ultra cheap. I have cut my bill from around $190/mo this time of year to around $35!

So far so good, but summer is coming and I don't think my battery bank will not get me through the night with even just the bedroom AC circulating on/off all night long. My plan is to add another 6kw to 12kw worth of panels (I will do this in stages adding 6kw in the next month or two and then adding the last 6kw next year)
, but to get me through the summer nights I am wanting to also upgrade my battery bank. Last August and September I consumed about 101kw worth of electricity per day ... since we are now more conscientious about how and when we run loads, I don't think we will be that high, but am still thinking we will consume around 75 to 90kw per day.

Currently my installer only has the 25kw worth of batteries hooked up to one of the two battery terminals inside the Solark. I am thinking of instead of adding another server rack array, to go with two of the EG4 power pro wall mounted batteries run in parallel. This will give me about 28kw worth of extra storage. My question is this, since I currently have only about 25kw worth of storage going into one of the Solark battery terminals, can I add the extra 28kw worth of EG4 Power Pro to the other terminals and will this cause any sort of issues with the Solark and/or the charging ability of the inverter? Or is it better/safer to just build another EG4 Lifepower 4 rack of batteries in the same 25kw configuration as my current battery bank?

The manual does not seem clear to me on this.

 

[Quattrohead]

Either way will work fine.
However, if you want to maintain communications between your inverter and all the batteries then all the batteries need to be the same type or have the same BMS, some of the EG4 LL batteries have the same BMS as the PowerPro battery I think, you will need to double check what you have and confirm with EG4 that it is okay to mix the two different capacities.
Or you can just communicate with only one set of batteries and the other set will lug along in dumb mode and this is fine too.

 

[XILLA]

Thank you for the reply!

 

[hwy17]

You can also just have comms to one battery, or one battery bank, and then add more non communicating batteries. Since they're all the same chemistry, the communicating battery's instructions will probably be good enough to satisfy the non communicating battery's needs.

 

[gotbeans]

Yea keep the wire length the same to each battery

 

[XILLA]

So, just to be clear, even though I am going into two different battery terminals and each battery bank is a different size, because they are the same chemistry the Soler will charge them the same? Is that correct?

 

[gotbeans]

Yea the voltage tries to even out. So as long as your batteries are connected with same length to a bus bar or something then that goes to the inverters they'll always try to maintain the same exact voltage
You should have breakers / fuse between all the batteries of course

When the solar charges the batteries, it will send a higher voltage than the batteries to the bus bars. The electricity will then flow to both batteries from those connection points. If the wires are the same exact length to each battery it'll be the best as the flow is "the same distance"

it's easiest to think of this as if it were water. Just imagine the batteries as jugs of water or whatever and the wires as pipes. same deal

 

[XILLA]

My plan was just to parallel the two new eg4 pro’s together and then come off one of them into the inverter, but instead i think you are saying I should use a bus bar to parallel them together and then use the same wire length I used from the original battery array to go from the bus bar to the inverter … correct?

 

[gotbeans]

My plan was just to parallel the two new eg4 pro’s together and then come off one of them into the inverter, but instead i think you are saying I should use a bus bar to parallel them together and then use the same wire length I used from the original battery array to go from the bus bar to the inverter … correct?

yea I'd avoid daisy chaining them like that.
Just get a fat bus bar like this
then in the future when you go for more batteries, it'll be there waiting
and when you get more inverters, it'll be there waiting.
Connect the batteries to the bus bar using the same length of wire to each battery

your wire lengths aren't correct not sure what you're talking about there.
The batteries should have the same length of wire to each of them and to the bus bar

 

[Quattrohead]

The battery connection terminals inside the inverter are a bus bar
Get a parallel kit with the batteries and you will have everything you need.

 

[gotbeans]

The battery connection terminals inside the inverter are a bus bar
Get a parallel kit with the batteries and you will have everything you need.

that doesn't support a growing system

 

[Quattrohead]

I am pretty sure you would be into a second inverter by the time you've reached the limit of this setup.

 

[XILLA]

Much appreciated to all! Thank you.