Hybrid Ouback Skybox with Nissan Leaf batteries

[Ampster]

Right. So your payback time has to include regular battery replacements.

Agreed. But:

1) is a money issue. This system will not save you money due to battery cost.
2) and 3) are for backup power and your needs will be better served by a generator. (That's why pretty much every off-grid system has a generator; it's the reliable backup for the less reliable solar system.)

I have a feeling that you just really, really want to build a solar battery system, even if it isn't cost effective. If so, that's fine - it's your money. But let's state that up front.............

I really want to build a solar battery system even if it isn't cost effective.

I have had a deposit on a Tesla Powerwall fo a year and no delivery date is in sight. After rebates and tax credits the Powerwall was going to cost $4,000. It would have allowed me to reach my goals cost effectively but I am tired of waiting. My Skybox project will give me several additional advantages over the Powerwall. With the Skybox I can incrementally add solar. I can also incrementally add more battery capacity at $200/kWh.

I completely understand why an off grid system would have a generator. When the sun doesn't shine there is no power. In a grid tie system when the grid is down there is a high probability that there is sunshine. I also don't want a generator making noise and taking up space. I don't want to maintain the generator and store the fuel to keep it running. I can think of many other reasons that I don't want a generator. The concept is free will.

@jflory2, if you really want to help, tell me how to break up a quote on this forum so I can interlineate my answers like you do.

[Ampster]

........
That works as long as you always charge at full power. Will your solar array always provide full power?
.......

Are you defining full power as 1C? Then the answer is no I do not want to charge at full power. Initially I will not have solar on this inverter. I will be charging from the grid or loosely AC coupled to my grid tie inverter. I will choose when I charge and I will choose how much power I charge at based on my battery capacity. I have a dream that by nursing my battery pack, I can get 8 years out of it.

[Ampster]

.....
I didn't think the Skybox had a current shunt. I could be wrong.

It can measure current on the ports. I don't know of it uses a shunt, hall effect sensor or a CT. You may be wrong. RTFM

[Ampster]

..........
The battery has to have the right BMS to be able to communicate with the Skybox. I have no doubt you could spoof it by telling it (for example) that it's a lead acid battery or something, but per Outback the way it's supposed to be used is with a battery that can communicate with the Skybox.

The chemistry itself doesn't matter. The fact that lithium chemistries need BMSes is what matters. If people had sodium-sulfur batteries that needed a BMS the same comment would apply.

I assume what you mean is a BMS that can be programmed. I am using an Orion Jr which I have left over from another project. It can only shunt a small current but I am less concerned about balancing currents. I want to adjust the parameters to send alarms as well as monitor and control charging.
I am not sure I understand to which device your example of spoofing applies. I don't know why I would tell either of those devices that I was using lead acid. Are you familiar with the Orion?
Also please explain what you mean when you say, "per Outback the way it's supposed to be used is with a battery that can communicate with the Skybox." Are you talking about CAN bus communication. That is an area where I could use some help from someone knowledgeable with the CAN bus communication. I used contact closures and relays to control my previous Radian system.

[Sunking]

I completely understand why an off grid system would have a generator. When the sun doesn't shine there is no power. In a grid tie system when the grid is down there is a high probability that there is sunshine. I also don't want a generator making noise and taking up space. I don't want to maintain the generator and store the fuel to keep it running.

OK then you need to stop. A generator is mandatory equipment.

[Sunking]

How long have yours lasted?

Model year was 2014, I bought them in 2016 and they were at roughly 90% rated capacity. Today, two years later at 75% capacity and ready to be replaced. Once the batteries hit the magic 80% capacity the ride to to 0 is very fast. So if it takes say 4 years to 80%, you have less than a year until unusable if you are lucky. Sort of like when you turn 55 to 60 years old, you slow down, and then aging accelerates very quickly.

[Mike90250]

@jflory2, if you really want to help, tell me how to break up a quote on this forum so I can interlineate my answers like you do.

When editing the reply , you manually insert the square brackets [ ] and QUOTE /QUOTE so that the desired quoted content is between the fields.
You have to read between the lines here, for the example , otherwise it will display as quoted

You may

have to

turn on the advanced editing

[jflorey2]

I really want to build a solar battery system even if it isn't cost effective.

OK thanks. That makes it easier to give advice.

I have had a deposit on a Tesla Powerwall fo a year and no delivery date is in sight. After rebates and tax credits the Powerwall was going to cost $4,000. It would have allowed me to reach my goals cost effectively but I am tired of waiting. My Skybox project will give me several additional advantages over the Powerwall. With the Skybox I can incrementally add solar. I can also incrementally add more battery capacity at $200/kWh.

A few notes about that:
1) The Skybox has a single MPPT channel, unlike inverters like the SMA line which have multiple channels. So you have to be careful to match string lengths and orientations.
2) Incrementally adding storage can be a bit problematic, since batteries will typically share unequally. With lithium the problem is lessened, but you still won't get great sharing (i.e. some batteries will bottom out before others, currents won't go where you think they should.)

I completely understand why an off grid system would have a generator. When the sun doesn't shine there is no power. In a grid tie system when the grid is down there is a high probability that there is sunshine. I also don't want a generator making noise and taking up space. I don't want to maintain the generator and store the fuel to keep it running. I can think of many other reasons that I don't want a generator. The concept is free will.

No worries there. If you don't want to get a generator, don't get one. Just know that pretty much everyone who has tried to make a go of it off grid has wound up with a generator.

Also, a propane generator requires effectively zero maintenance or care if you never use it. And if you never use it - there's no noise. When the day comes that you really need it, you are better off trying to decide whether to make some noise or not than to not have that option.

@jflory2, if you really want to help, tell me how to break up a quote on this forum so I can interlineate my answers like you do.

As other people have mentioned, use the HTML tags to quote and unquote sections of text.

Are you defining full power as 1C? Then the answer is no I do not want to charge at full power. Initially I will not have solar on this inverter. I will be charging from the grid or loosely AC coupled to my grid tie inverter. I will choose when I charge and I will choose how much power I charge at based on my battery capacity. I have a dream that by nursing my battery pack, I can get 8 years out of it.

You can't rely on charge current declining in an AC coupled system - because the battery will go overvoltage before the charge current declines.

You won't have a problem during normal operation. During AC coupled operation (i.e. power outages) you can't use charge current to terminate. You need to use SoC.

It can measure current on the ports. I don't know of it uses a shunt, hall effect sensor or a CT. You may be wrong. RTFM

Haven't been able to get a hold of one yet. If it can determine SoC on its own, then that will work to terminate charge.

I assume what you mean is a BMS that can be programmed. I am using an Orion Jr which I have left over from another project. It can only shunt a small current but I am less concerned about balancing currents. I want to adjust the parameters to send alarms as well as monitor and control charging.
I am not sure I understand to which device your example of spoofing applies. I don't know why I would tell either of those devices that I was using lead acid. Are you familiar with the Orion?
Also please explain what you mean when you say, "per Outback the way it's supposed to be used is with a battery that can communicate with the Skybox." Are you talking about CAN bus communication. That is an area where I could use some help from someone knowledgeable with the CAN bus communication. I used contact closures and relays to control my previous Radian system.

Lead acid batteries do not use BMSes so no communication will be required. You can tell the inverter you have a lead acid battery, then set absorb and float voltages to the same value (i.e. 4.1 or 4.2 volts per cell) and the li-ions will be happy with that.

Other batteries do use BMSes. So if you set the inverter to (for example) "LG RESU10" it will look for that CAN bus communication. (There are a lot more protocols/interfaces than just CAN out there.) That's why you might have to tell it you have a lead acid battery. Or you may be able to tell it you have something like a SimpliPhi battery, since those do not have externally accessible coms either.

[Ampster]

OK thanks. That makes it easier to give advice.

A few notes about that:
1) The Skybox has a single MPPT channel, unlike inverters like the SMA line which have multiple channels. So you have to be careful to match string lengths and orientations.
2) Incrementally adding storage can be a bit problematic, since batteries will typically share unequally. With lithium the problem is lessened, but you still won't get great sharing (i.e. some batteries will bottom out before others, currents won't go where you think they should.)

1) Yes, that might be a limitation for some but I already have 5.7kW of panels on my roof and have room for 3 or 4 kW more there. Foreseably that is all I would ever need. They will all be oriented the same. To meet the minimum voltage, the minimum number of panels is about 7 or 8. That is at least six months down the line.
2) I am going to pay more attention to that before I add much more capacity. I don't have much quality control over any additional Leaf modules that I might add. I may have to do some sort of binning as I add modules to the pack. It will be 14 cells in series (7 modules).

No worries there. If you don't want to get a generator, don't get one. Just know that pretty much everyone who has tried to make a go of it off grid has wound up with a generator.

Also, a propane generator requires effectively zero maintenance or care if you never use it. And if you never use it - there's no noise. When the day comes that you really need it, you are better off trying to decide whether to make some noise or not than to not have that option.

I will look at that option when I consider an increase in battery capacity. Propane generators look attractive.

You can't rely on charge current declining in an AC coupled system - because the battery will go overvoltage before the charge current declines.

You won't have a problem during normal operation. During AC coupled operation (i.e. power outages) you can't use charge current to terminate. You need to use SoC.

I will make a note about this when I get to AC coupled operation. That will be when the firmware is out sometime in 2019. This is an area where I may need some help down the line.

......
Lead acid batteries do not use BMSes so no communication will be required. You can tell the inverter you have a lead acid battery, then set absorb and float voltages to the same value (i.e. 4.1 or 4.2 volts per cell) and the li-ions will be happy with that.

Other batteries do use BMSes. So if you set the inverter to (for example) "LG RESU10" it will look for that CAN bus communication. (There are a lot more protocols/interfaces than just CAN out there.) That's why you might have to tell it you have a lead acid battery. Or you may be able to tell it you have something like a SimpliPhi battery, since those do not have externally accessible coms either.

My Orion BMS uses CAN so I want to try that. You raise an interesting point about SOC. My BMS would normally keep track of that but when I used it with the Radian the EMF was so bad the Orion shunt wouldn't register. That and the various cell max settings will be what I will be focusing on adjusting during my setup phase.

[Ampster]

.......... A generator is mandatory equipment.

Not according to the Sonoma County building department or the LG Chem or Tesla Powerall installations that I am aware of. I understand that you feel it is mandatory.

[J.P.M.]

Not according to the Sonoma County building department or the LG Chem or Tesla Powerall installations that I am aware of. I understand that you feel it is mandatory.

The AHJ is mostly concerned about safety, not convenience.

As for peddlers, why would they have any interest in selling or creating a need for equipment they do not peddle that will only make an install more costly and also point out shortcomings in their product ?

Maybe the difference lies in the definition/context of "mandatory". I can sail/operate a boat without an anchor or spare sails, but those things come in handy. Most off grid and otherwise fit for purpose systems can be safely operated w/out an aux. generator but many/most experienced off grid users seem to feel a pressing need for them usually sooner rather than later, sometimes in short order based on experience.

Perhaps they know something you haven't discovered yet.

Many users on and off grid break their ass getting some types of rather sophisticated monitoring they seem to not be able to live without (or have been brainwashed into believing it's essential). To them, such information is "mandatory" even though they haven't a clue of the difference between a watt and a kWh much less what much if any of their monitored output means.

Definitions of conditions such as mandatory and essential are often more situation variable than preferences often more user specific and not as mandated as sometimes thought.

[Ampster]

...... Most off grid and otherwise fit for purpose systems can be safely operated w/out an aux. generator but many/most experienced off grid users seem to feel a pressing need for them usually sooner rather than later, sometimes in short order based on experience.

Perhaps they know something you haven't discovered yet.

No doubt they do know someting I don't because their circumstances are different than mine. I completely understand why they would want a backup for their primary source of energy. However my primary source of energy is the grid and the subject of this thread is my hybrid system to complement my grid tied system. That hybrid system doubles as backup and I don't really feel the need initially for a backup for my backup. Down the line it is possible. The Skybox has a generator input and I have priced propane generators. I am going to focus on finding the right balance between more batteries for load shifting and more solar panels for reducing my purchase of power from the grid.

This is the Hybrid , Grid Tied With Batteries section of this forum correct? If I had wanted advice on an off grid system I would have posted in the off grid section of this forum.

[Sunking]

Not according to the Sonoma County building department or the LG Chem or Tesla Powerall installations that I am aware of.

Duh! They are not going to say that. If they told the truth, they would scare customers away and loose business.

[Ampster]

I prefer vendors who give me what I want, rather than try to sell me a back up for a backup on a grid tied system that has a fair amount of uptime. By fair amount I mean one or two outages a year lasting two or three hours.
All of the battery systems I referred to qualified for the California Self Generation Incentive Program for grid tied systems. Does anybody here know if the additional expense of a generator even qualifies for SGIP funds? I do know it does not qualify for Federal Investment Tax Credit.

[Ampster]

.........

Many users on and off grid break their ass getting some types of rather sophisticated monitoring they seem to not be able to live without (or have been brainwashed into believing it's essential). To them, such information is "mandatory" even though they haven't a clue of the difference between a watt and a kWh much less what much if any of their monitored output means.

Definitions of conditions such as mandatory and essential are often more situation variable than preferences often more user specific and not as mandated as sometimes thought.

..........
Yes, that describes one of my friends who recently installed two Powerwalls. He is on grid, has PV solar panels on his entire roof and shade structure. He is on California NEM 1.0 and has a substantial credit each year at true up. Every time I see him he shows me his Tesla app on his phone and the nice graph showing the power he has stored.

i agree with your last paragraph that definitions are situation variable and user specific. That would be my situation. I chose a hybrid inverter to complement my existing grid tie system because of the risks I wanted to mitigate.