inverter selection

[wired]

I am looking for a 10k (give or take) inverter, with the following characteristics. Any suggestions? I want to be able to pull power from the grid, but do NOT want (and never will want) to send power back to the grid. 3 mppt connections minimum (2 strings needed now). I don't need stackability if at least 10k AC output. I will have a battery bank, so need a charge controller built-in. The solar array will be 5k, with possible expansion to about 7.5k in future. I'd prefer for it to be battery agnostic (I've seen some inverters with good price, but then they require very pricey batteries).

My preference would be for it to have a backup generator hookup as well, so if the grid is down it can auto start a gas-powered backup generator -- so far I've only seen this with higher priced inverters that have options I don't want. I can live with having my installer use another method to hook up a backup generator, but would like at least the potential to do this in some way.

 

[Zapper77]

I am looking for a 10k (give or take) inverter, with the following characteristics. Any suggestions? I want to be able to pull power from the grid, but do NOT want (and never will want) to send power back to the grid. 3 mppt connections minimum (2 strings needed now). I don't need stackability if at least 10k AC output. I will have a battery bank, so need a charge controller built-in. The solar array will be 5k, with possible expansion to about 7.5k in future. I'd prefer for it to be battery agnostic (I've seen some inverters with good price, but then they require very pricey batteries).

My preference would be for it to have a backup generator hookup as well, so if the grid is down it can auto start a gas-powered backup generator -- so far I've only seen this with higher priced inverters that have options I don't want. I can live with having my installer use another method to hook up a backup generator, but would like at least the potential to do this in some way.

Price point?
Space restrictions?
UL, NEC or Permits?
Willing to DIY a generator relay?
Open to manually controlling a few features?

 

[DIYrich]

Off-Grid inverter will do what you want. You will need a Transfer Switch to change between Grid and Generator for AC Input.
If you buy a Chargeverter, you can charge the batteries directly from the Generator, and avoid the cost of a Transfer Switch (but you may still need a disconnect switch).

 

[Mattb4]

Finding one with 3 SCC-MPPT is the hard part. There are many with 2. You might consider simply adding an additional separate SCC feeding from its own array (Note: an array can consist of multiple strings but only one SCC) to your battery bank. You did not mention your voltage needs whether you need 240vAC split phase or something else.

Auto starting a generator can be difficult since the generator must be setup to handle it. Almost all your off grid AIO's these days provide a set of Dry contacts (2 wire) to give the signal.

 

[MainstreamGreen]

I am looking for a 10k (give or take) inverter, with the following characteristics. Any suggestions? I want to be able to pull power from the grid, but do NOT want (and never will want) to send power back to the grid. 3 mppt connections minimum (2 strings needed now). I don't need stackability if at least 10k AC output. I will have a battery bank, so need a charge controller built-in. The solar array will be 5k, with possible expansion to about 7.5k in future. I'd prefer for it to be battery agnostic (I've seen some inverters with good price, but then they require very pricey batteries).

My preference would be for it to have a backup generator hookup as well, so if the grid is down it can auto start a gas-powered backup generator -- so far I've only seen this with higher priced inverters that have options I don't want. I can live with having my installer use another method to hook up a backup generator, but would like at least the potential to do this in some way.

A Sol-Ark 12K would meet your requirements, and give you lots of expansion potential. Their customer service to DIY and off-grid customers is among the best I've seen in the industry. Beware of cheap imports with names you've never heard of. You may save upfront buying junk but might cost you over the long-term.

 

[MainstreamGreen]

A Sol-Ark 12K would meet your requirements, and give you lots of expansion potential. Their customer service to DIY and off-grid customers is among the best I've seen in the industry. Beware of cheap imports with names you've never heard of. You may save upfront buying junk but might cost you over the long-term.

I correct myself- if you want 3 MPPT inputs, for Sol-Arks you'd need to go to the 15KW model. May I ask why you need 3? 3 different types of panels? The Sol-Ark 12 kw can handle over 12KW of PV, but only has 2 MPPT's.

 

[wired]

Appreciate the replies. I've reviewed the recs and learned a lot since my original post. Looks like I only need two MPPT connections (one now, one for possible future expansion). I'm leaning towards Schneider's XWPro6848 and the MPPT 100 600 charge controller, and EG4 LifePower4 48V batteries. A question has come up about "unused power". The batteries need 56.2V and 30-50amps recommended to charge, so 56.2*30=1686 watts to charge. If I keep to my current planned array layout I'll have STC voltage of 307V. This implies 1686/307=5.5Amps minimum to charge the batteries (the charge controller will convert to proper voltage). At STC I can expect 15.7 amps. The 5.5 needed is 35% of the 15.7. So, I need the sun's insolation to be at least about 1/3 of the sun's full (STC) insolation in order to start charging the batteries. Am I thinking about this correctly? Does this mean that the lower 1/3 of sunshine does not get used? Is that unused power?

 

[DIYrich]

Anything at or above the MPPT's minimum voltage will start it pushing power to the battery. It may be only a few watts.

The voltage of the panels is pretty steep, so they will likely exceed the minimum voltage of the mppt pretty quickly. Again, it may not be many watts.

The batteries don't have a real minimum amps. They will gladly take 1 amp. There is a recommended charge rate that is typically around 0.3c, and a max charge rate typically 0.5c.

 

[wired]

That helps, thanks. Here's another question. I'm planning to have an MDP and a backup subpanel. When the grid is down the inverter disconnects from grid side and will solely use solar and batteries to feed the backup subpanel. In which case, the loads from the MDP don't get fed. When the grid is up those MDP loads will get fed, as well as the backup loads / batteries as needed.

But what feeds these MDP loads when the grid is up? Do the MDP loads get fed solely from the Grid power? Or, can this power also come from the solar / batteries? My hunch is the latter - that they can be fed from a mixture of grid power AND power from solar / batteries. That seems to make sense since (for our situation) the inverter's AC output will be connected supply side to a lower breaker in the MDP.

Assuming this is the case, a concern is when there is "too much" power coming from solar. Suppose the batteries are full, there are minimal loads, the sun is shining, and the solar output exceeds what is being used. Of course, if one is using net-metering or similar, one simply sends that extra power back to the grid. But what if, as is the case with us, we don't plan to sell back to the grid? (To note, I don't expect this will occur very often - my estimates show this would happen only occasionally in May and June -- for the most part our solar wont have enough power to handle our typical loads.) I'm still in the planning stages and so have a chance to 'change my mind' on plans and expectations. But what options might I have here?