Solar charging - what size/type inverter, etc?

[jray3]

That's right Bradford; with a grid tie PV system you can attach the i-MiEV (or any other load, within reason) with no problem. My 2.2 kW grid-tie system on a dual-axis tracker has produced more than the car has consumed over the past six months. I doubt that'll be the case through a long Seattle winter, but am currently erecting a 1.9 kW solar carport to increase production.

 

[Phximiev]

Let's see a pic of the solar array on tracker. Who installed it?

I am considering doing the same here.

 

[jray3]

Let's see a pic of the solar array on tracker. Who installed it?

Why I and my i installed, of course. MR BEAN hauled home the panels and all parts except the 20' long 8" diameter steel pole and the 54 bags of concrete mix!






(Sorry for the massive photos. I'll try to figure that out too.) In this completion photo from November, it is sunset and I was still working on the controls. Of course, the far end of our property was best for exposure; there's nothing like digging 200' of trench through glacial till! The tracker is secondhand, a discontinued WattSun AZ-125. An electrician friend had accidentally installed it too close to a property line, and had to remove it 8 years later when it was time to sell the house, so I got it cheap and had to rebuild the azimuth motor, replace the power supply, repaint and re-lube everything. I kept the original panels for an off-grid project, but maximized returns by buying new made-in-Washington modules to tap a $0.35/kWh state subsidy.

 

[pbui19]

.... In regular use I have a larger bank of mismatched used EV (no longer suitable capacity for mobile applications) AGM lead acid batteries. Any mainstream off grid solar designer would say it won't work. But I have 4 years of hard data showing that it does work and work well. Essentially my battery bank is free and will continue to be, as long as I do EV service and modifications. Some of them are orbitals that were manufactured in 2004!

The panels are 60 cell SolarWorld panels for a total of 2600 watts, The charge controllers are Morningstar 65 amp MPPT units (three paralleled). In day to day practice the panels are grid tied, but are also wired to divert the DC to the charge controllers if the grid is down. A small investment IMO to keep the food cold and our kesters warm or cool (depending on season) during a prolonged outage. Why only a 12 volt battery bank when 48V would be more efficient? It's much easier to use mismatched batteries if there are no series strings.

Also a charged iMiEV battery could keep the critical loads going for up to 4 days through the DC to DC converter in the car (12 volt output).

Aerowhatt

hi Aerowhatt - since we have been getting intermittent power outage due toEl Nino slamming CA, I am interested again to rig up a home back up system. In your quote above, about mixing 12v battery and using the iMiev aux 12v, are you also just paralleling the iMiev 12v to your pack of 12v batteries ? (fused I assume). If so, how do you limit the current ? just by default to whatever the iMiev DC/DC can put out ?

Thanks,

 

[Aerowhatt]

hi Aerowhatt - since we have been getting intermittent power outage due toEl Nino slamming CA, I am interested again to rig up a home back up system. In your quote above, about mixing 12v battery and using the iMiev aux 12v, are you also just paralleling the iMiev 12v to your pack of 12v batteries ? (fused I assume). If so, how do you limit the current ? just by default to whatever the iMiev DC/DC can put out ?

Thanks,

Sure I hope this helps. I’m not sure of your situation or if solar is part of the mix so I will try to cover either scenario.

Generally an off grid backup system uses.

Solar panels - produce power to charge the batteries

Charge controller - controls power to protect the batteries

Batteries - store power for use when needed

Inverter - converts DC to AC power suitable for standard grid run loads.

The charge controller is a critical component. El Cheapo models can cause a lot of upstream DC ripple. And also can do a poor job of taking care of your storage batteries.

More to the specifics of your question the best place to connect the jumpers from the iMiEV battery are to the charge controller inputs (Replacing the solar panels). That way if the storage batteries are very low and can draw a lot of amps the "solar" charge controller will limit them.

The cable on my iMiEV from the DC to DC is fused at 60amps at the battery terminal (it comes that way). The DC to DC is rated at 80 amps. You want a charge controller that will limit to no more than 50 amps to keep from adding Other problems to your grid power outage.

Now the DC to DC only works when the car is in ready mode or the grid is charging the car. If you leave the car in ready mode the whole time you will waste some significant power over time. The way to use it is to put it in ready mode long enough to bring your storage batteries up to 14.0 - 14.2 volts or so while charging. Then turn the car off and let the storage batteries carry the loads until they need another boost charge.

If you don’t already know a lot about using inverters to power household loads then study up on it. Safest easiest way to do it is to keep your back up system completely separate from your grid tied house distribution or service panel.

Aerowhatt

 

[JoeS]

Aerowhatt, over what range of dc voltages does your solar system operate and what charge controller are you using?

 

[databeestje]

Looking from the side view I can see where the length increase on the i in the US is coming from, the bumpers. Must be the 5 mph collision without damage rules. That makes the car just as long internally really. Still wider.

 

[Aerowhatt]

Aerowhatt, over what range of dc voltages does your solar system operate and what charge controller are you using?

I have mostly solar world panels and a mismatch of "12V" panels. What really matters is the cell count in each panel (or group of series wired panels). Since the solar world panels are 60 cells. And the "12 V" panels are 36 cells they can't be used with the same charge controller . . . unless matched or closely matched (rated wattage) "12V" are series wired in pairs which yields two panels adding up a 72 cell composite. So I have "virtual" 72 cell and actual 60 cell panels. These can be paralleled through the right MPPT charge controller with very little power loss for the disparity in panel voltage. That is what the full time off grid part of my system runs on. This works out to a nominal input voltage of ~ 35 volts at the controller.

The grid tied system is all 60 cell panels with a grid tied micro inverter for each panel. In a prolonged outage it is set up to divert the solar power to MPPT charge controllers. The panels group up into series strings of three panels each 180 cells in series or ~ 103 volts (the higher voltage allows for less wire loss, fewer wires needed, and smaller wires).

I like the charge controllers because of who makes them and how they are made. They are versatile, reliable, efficient and a good value. You can use any panel(s) voltage with them as long as it is above your battery bulk charge voltage and under 150VDC OCV. The units can seemlessly be switched from 100 volts input to the 14.4 volt output from the iMiEV without any adjustments at all.

The inverters I use are Morningstar Track Star charge controllers.

For a simple system using a grid tied charger for a backup power bank of batteries. That could also be replenished by the 'i' traction pack during medium duration outage. A much simpler less expensive PWM charge controller could be used effectively but without the flexibility that the MPPT controllers provide. I would still stick with Morningstar for such a controller.

Aerowhatt

 

[JoeS]

Aerowhatt, thank you for your comprehensive description. Interesting that your PV system brings out both DC as well as micro-invertered AC from your panels. I agree with you about Morningstar and have a TS-45 TriStar, but PWM rather than MPPT. Don't get me wrong, I'm a fan and very early adopter of MPPT, having had an old RV Products (now Blue Sky Energy) Solar Boost unit on my boat. The TS-45 had a very specialized 48v application at the time I bought it where the MPPT feature did not offer a significant advantage (input voltage was very close to output).

The problem that I have is that my grid-tied 6.6kW ground-mounted system operates at around 250vdc, with good access to that voltage, while my recent roof-mounted 4kW system has the Enphase microinverters and only brings out ac. The 250vdc is too high for all the 48v controllers I presently own, and so I'm looking for a controller that I could hook up to that 250vdc and feed my 48vdc battery bank in case of a power outage. Don't want to pay an arm and a leg for something that would be used only in an emergency.

 

[pbui19]

I like the charge controllers because of who makes them and how they are made. They are versatile, reliable, efficient and a good value. You can use any panel(s) voltage with them as long as it is above your battery bulk charge voltage and under 150VDC OCV. The units can seemlessly be switched from 100 volts input to the 14.4 volt output from the iMiEV without any adjustments at all.

The inverters I use are Morningstar Track Star charge controllers.

For a simple system using a grid tied charger for a backup power bank of batteries. That could also be replenished by the 'i' traction pack during medium duration outage. A much simpler less expensive PWM charge controller could be used effectively but without the flexibility that the MPPT controllers provide. I would still stick with Morningstar for such a controller.

Aerowhatt

that is a really good idea to feed the iMiew 14.4vdc through the charge controller. So do you tap directly to the iMiev aux battery (presumably with an Anderson disconnect of some sort) ? Which model Morningstar inverter/controller are you using that allow seamless switching between 100vdc and 14vdc ?

 

[Aerowhatt]

Don't want to pay an arm and a leg for something that would be used only in an emergency.

Yes, I hear you on the cost issue. But for many what is keeping your pipes from freezing and/or most of your food from spoiling in an emergency worth?

Morningstar has a MPPT charge controller the that will convert voltages as high as 600 volts efficiently down to charge your batteries at 48 volt. I haven't priced it recently, when it first came out it was kind of high IMO. But then again components that run at those voltages are pricy too. If memory serves it's low end voltage was 150VDC so it would work for your system.

Aerowhatt

 

[Aerowhatt]

So do you tap directly to the iMiev aux battery (presumably with an Anderson disconnect of some sort) ? Which model Morningstar inverter/controller are you using that allow seamless switching between 100vdc and 14vdc ?

Andersons should work well. I went more universal though for reasons I will point out. Basically, my solar panel wires come in to a DC circuit breaker panel/combiner box. Connected to the same breaker box (independent breakers) are two wires which run out to two well labeled posts mounted about 12 inches apart securely mounted on a insulating surface. With this connection method. I can use any car and any (long enough) good quality jumper cables to connect the battery to my wall mounted "battery" posts. If it is an ICE I just would use the shop vac hose to run the exhaust outside. By using a universal connection method you keep your options open. I can certainly envision an emergency situation where the capacity of the 'i' plus a full tank of gas in an ICE car would be cutting it close to get one through without loosing power completely (Assuming complete overcast, or unavailable solar for some other reason).

If you are mixing this kind of system with solar (operating at higher voltage) you must consider all contingencies and circumvent any possible scenario that would expose the higher voltage to the wall mounted terminal posts (and by default the cars electrical system). However accomplishing that is not difficult or expensive but it is a long description/discussion.

If I were doing this setup without solar included in the mix I would use this one for cost savings:

http://www.solar-electric.com/inverters-controllers-accessories/chco/mochco/stpwmchco/trts12vochco.html

If solar were included or might be in the future I would use this one (the one that I do use for this purpose):

http://www.solar-electric.com/inverters-controllers-accessories/chco/mochco/admpchco/motr45ampmps.html

Aerowhatt

 

[JoeS]

Don't want to pay an arm and a leg for something that would be used only in an emergency.

Yes, I hear you on the cost issue. But for many what is keeping your pipes from freezing and/or most of your food from spoiling in an emergency worth?
Morningstar has a MPPT charge controller the that will convert voltages as high as 600 volts efficiently down to charge your batteries at 48 volt. I haven't priced it recently, when it first came out it was kind of high IMO. But then again components that run at those voltages are pricy too. If memory serves it's low end voltage was 150VDC so it would work for your system.

Thanks for the lead - Morningstar TriStar MPPT 600V. $1300 for bottom-of-line unit that handles between 100v and 525v, so that would work on my 250v system. Needs custom PC software to program the custom output profile I'd need for my lithiums.

I'm not worried about short-term outages, as I have plenty of capacity to keep things like the fridge running for weeks by simply plugging a 12v inverter into the half-dozen EVs around here as well as all the loose AGM batteries which I keep fully charged.

My desire is to be able to solar recharge a fairly large 48v battery bank so I could recharge my BEVs in case of an extended outage. For example, my power was out for a week after the 1988 Loma Prieta earthquake ... but if that were the same case today then I'd simply drive down into town and plug in there as city-dwellers had their power restored quickly. Don't want to get too paranoid with self-sufficiency - it's not like being on a boat in the middle of the ocean where system redundancy is rather important (been there, done that).

 

[pbui19]

I can certainly envision an emergency situation where the capacity of the 'i' plus a full tank of gas in an ICE car would be cutting it close to get one through without loosing power completely (Assuming complete overcast, or unavailable solar for some other reason).

Aerowhatt

You are effectively using the i traction pack as your backup and solar storage, albeit in a cache mode with a lower current capacity. The i 12v can feed your external backup pack, and when the sun is shining and your external pack is full, you can charge the i traction pack via L1. In my case, a L3 charger is 12 miles down the hill; so I can replenish for those extended outage cloudy days. I like it.