Running on solar

[72dan]

I have wired up 800 watts of flexible solar panels.
The panels are 100 watts each, about 20 volts open voltage, I run 4 in series, i.e. 80 volts input.
I have my 12 volt stuff charging, but want to use 48 volt lithium batteries and two inverters to run my 110 volt stuff.

Anybody have experience doing this?
Any professionals recommended in the Los Angeles area?

[Ohiobrits]

A couple of observations:-

Running the panels in series will give you a bit more power due to reduced cable losses (higher voltage) but will seriously reduce output if any of the panels in the string are shaded, even if one or two are in full sun and just a few of the cells on another are shaded you will only get a fraction of the potential power. Maybe a consideration if you camp in wooded areas much. If you are in full sun most of the time your setup will work very well.

If I understand what you are asking correctly you want to use the current 12V house batteries for normal 12V users and then have a separate 48V lithium setup for AC power. This would make sense, a 48V DC system will drastically reduce current draw into the inverter when compared to 12 V DC and hence reduce the wire sizes required and potentially losses in your system.

If you do want to go this route you will probably need 2 solar charge controllers, one for 12V and one for the 48V system. Most charge controllers need the battery voltage set. In addition the charge profile and voltages are different for lithium v lead acid. In this configuration you would need to allocate a few solar panels to the 12V and the rest to the lithiums. Another consideration is that inverters are typically available for 12V and 24V (not 48 V).

You would probably retain the factory converter/charger to charge the 12V battery when on AC and use your larger inverter (charger) for the lithiums.

Another potential option to enable use of just one solar charge controller might be to use one of the Victron BlueSolar MPPT solar charge controllers - most sense battery voltage so you might be able to use one charge controllers and have a 100A changeover switch to toggle between batteries. BlueSea makes changeover switches to swap between 2 battery banks that should be sufficiently rated. You would need to decide on a charge profile and stick with it (probably setup for Lithium). Almost certainly will not be the optimal voltages / charge stage duration for your lead acid batteries. Check your lead acid battery manufacturers recommendations for the correct values.

If you want to get very fancy with the above solution, you could probably automate changeover using contractors and relays driven by a Victron BMV 702. It can monitor 2 batteries and has a relay output that could be configured based on voltages (I think &#128578 - I.e when the house battery is at x V switch to charging the lithiums and then back as voltage drops.

I think a 2 battery system is probably too complex to be worth it in my opinion. If you do decide to go this route though, post your results.

[dhroberts]

Originally Posted by Ohiobrits

A couple of observations:-

Running the panels in series will give you a bit more power due to reduced cable losses (higher voltage) but will seriously reduce output if any of the panels in the string are shaded, even if one or two are in full sun and just a few of the cells on another are shaded you will only get a fraction of the potential power. Maybe a consideration if you camp in wooded areas much. If you are in full sun most of the time your setup will work very well.

If I understand what you are asking correctly you want to use the current 12V house batteries for normal 12V users and then have a separate 48V lithium setup for AC power. This would make sense, a 48V DC system will drastically reduce current draw into the inverter when compared to 12 V DC and hence reduce the wire sizes required and potentially losses in your system.

If you do want to go this route you will probably need 2 solar charge controllers, one for 12V and one for the 48V system. Most charge controllers need the battery voltage set. In addition the charge profile and voltages are different for lithium v lead acid. In this configuration you would need to allocate a few solar panels to the 12V and the rest to the lithiums. Another consideration is that inverters are typically available for 12V and 24V (not 48 V).

You would probably retain the factory converter/charger to charge the 12V battery when on AC and use your larger inverter (charger) for the lithiums.

Another potential option to enable use of just one solar charge controller might be to use one of the Victron BlueSolar MPPT solar charge controllers - most sense battery voltage so you might be able to use one charge controllers and have a 100A changeover switch to toggle between batteries. BlueSea makes changeover switches to swap between 2 battery banks that should be sufficiently rated. You would need to decide on a charge profile and stick with it (probably setup for Lithium). Almost certainly will not be the optimal voltages / charge stage duration for your lead acid batteries. Check your lead acid battery manufacturers recommendations for the correct values.

If you want to get very fancy with the above solution, you could probably automate changeover using contractors and relays driven by a Victron BMV 702. It can monitor 2 batteries and has a relay output that could be configured based on voltages (I think &#128578 - I.e when the house battery is at x V switch to charging the lithiums and then back as voltage drops.

I think a 2 battery system is probably too complex to be worth it in my opinion. If you do decide to go this route though, post your results.

Ohiobrits,

I have a question regarding your unit's solar panel / lithium bank configuration. I am new to this whole RV scene, have a 2016 30' Classic and am about to have a 900W / 600 amp hour lithium bank installed.

I believe I understand that you have a 600W panels / 864 Amp hour hour lithium system. Your lithium bank size seems quite robust in comparison to the 600W panels. What were your design thoughts? Did the 27' length of your AS limit you to the 600W of panels?

Thanks for your consideration. Any advice is appreciated. Dennis

[72dan]

Originally Posted by dhroberts

Ohiobrits,

I have a question regarding your unit's solar panel / lithium bank configuration. I am new to this whole RV scene, have a 2016 30' Classic and am about to have a 900W / 600 amp hour lithium bank installed.

I believe I understand that you have a 600W panels / 864 Amp hour hour lithium system. Your lithium bank size seems quite robust in comparison to the 600W panels. What were your design thoughts? Did the 27' length of your AS limit you to the 600W of panels?

Thanks for your consideration. Any advice is appreciated. Dennis

I have 800 watts on the RV, currently they are just charging a couple 12 volt batteries.
I have a 48 volt lithium battery, the type used in the 2015 Chevy Volt, sitting waiting to be installed. It is 48 volt, 50 amp hours.

You mention watts but it doesn't make sense.
If you have a 12 volt battery and it is 100 amp hours, that means the battery can supply 1200 watts (12 X 100) for one hour. But lead acid batteries can only be drained 50%, lithium about 80%.

I have to inverters that I have partially installed, both will connect to the 48 volt battery (eventually I will put more batteries), and each inverter is capable of putting out 3,600 watts.

It is necessary to have two inverters to tie to the grid for two reasons
1) each air conditioner (I have two) will take 3,000 watts to start and without a second inverter I will fry an inverter
2) the shore power is 220 volt so there are two hot wires, each is 110 volts, so one hot to each inverter as the inverters are 110 volts each.

I have a separate solar array on my truck 220 watts, with a 12 volt 100 amp hour lithium pack. I have a connector on the back of my truck and 4 gauge cables so I can connect that to the RV as well.

[72dan]

Originally Posted by Ohiobrits

A couple of observations:-

Running the panels in series will give you a bit more power due to reduced cable losses (higher voltage) but will seriously reduce output if any of the panels in the string are shaded, even if one or two are in full sun and just a few of the cells on another are shaded you will only get a fraction of the potential power. Maybe a consideration if you camp in wooded areas much. If you are in full sun most of the time your setup will work very well.

If I understand what you are asking correctly you want to use the current 12V house batteries for normal 12V users and then have a separate 48V lithium setup for AC power. This would make sense, a 48V DC system will drastically reduce current draw into the inverter when compared to 12 V DC and hence reduce the wire sizes required and potentially losses in your system.

If you do want to go this route you will probably need 2 solar charge controllers, one for 12V and one for the 48V system. Most charge controllers need the battery voltage set. In addition the charge profile and voltages are different for lithium v lead acid. In this configuration you would need to allocate a few solar panels to the 12V and the rest to the lithiums. Another consideration is that inverters are typically available for 12V and 24V (not 48 V).

You would probably retain the factory converter/charger to charge the 12V battery when on AC and use your larger inverter (charger) for the lithiums.

Another potential option to enable use of just one solar charge controller might be to use one of the Victron BlueSolar MPPT solar charge controllers - most sense battery voltage so you might be able to use one charge controllers and have a 100A changeover switch to toggle between batteries. BlueSea makes changeover switches to swap between 2 battery banks that should be sufficiently rated. You would need to decide on a charge profile and stick with it (probably setup for Lithium). Almost certainly will not be the optimal voltages / charge stage duration for your lead acid batteries. Check your lead acid battery manufacturers recommendations for the correct values.

If you want to get very fancy with the above solution, you could probably automate changeover using contractors and relays driven by a Victron BMV 702. It can monitor 2 batteries and has a relay output that could be configured based on voltages (I think &#128578 - I.e when the house battery is at x V switch to charging the lithiums and then back as voltage drops.

I think a 2 battery system is probably too complex to be worth it in my opinion. If you do decide to go this route though, post your results.

I have two charge controllers, both Outback Flexmax 80's.
I know it gets complicated but it is necessary. It makes it more complicated as the Outback Mate 3 controller will not work with two separate voltage batteries.

But to try and run a 3000 watt air conditioner off a 12 volt battery at 250 amps is incredibly inefficient. Plus the drain on the batteries to discharge at that high of an amperage for a long period can shorten the battery life.
Any time you charge/discharge at more than 1C it is not as efficient.

On a 12 volt 100 amp hour pack 1C is charging or discharging at 100 amps.


I fly carbon fiber model airplanes with Lithium cobalt batteries. I have planes that will burst at 4000 or more watts for a few seconds.
I have to set my electronic speed control for on/off only and no partial throttle because I am at 250 amps and part throttle and the speed control catches on fire. I run the batteries at 100C or more discharge and a battery pack may last 50 flights.

Often we go from a 4 cell pack to a 6 cell or 8 cell to increase voltage and drop amps so things run more efficiently.

Likely I will have two arrays on the RV, the 800 watts I have on the curved front now and 1000-1500 watts on the roof. Each to a separate charge controller.
I will have to see where I am deficient, in 12 volt or 48 volt power or maybe just run a 48 vdc to 12 vdc converter.

Yes a different charge profile for Lithium. I had the 12 volt pack in my truck for about a year and just dropped a cell. It is a CALB pack which I have to built and mount the cell balancing boards. It is 4 cells each with a max capacity of 3.65 volts. I am dealing with CALB on it now and possibly will reduce my max charge voltage from 14.6 volts (3.65 volts x 4 cells) to 14.2-14.4 volts.

I will not have any lead acid in the RV when I am done. Both 48 volt (really 58.4 volts, 16 cells X 3.65 volts per cell) and the 12 volt (14.6 volts) will be lithium but still to switch voltages requires reprogramming the charge controller each time.

On my truck I am using the Blue Sky 3000i charge controller, it isn't as sophisticated as the Outback FlexMax 80 and can't run as many watts but a fraction of the size and it is fully programmable for the charge profile.

[72dan]

By the way I have photos and video here. At first my link didn't show.
http://www.airforums.com/forums/f448...ar-156393.html

The RV is Axxess which is now a sister company to Airstream under the same ownership.
The only way to get a true toy hauler until Airstream makes a Panamerica again.

I just don't understand it. The Panamerica is so sought after, it is like finding a classic Ferrari and they sell now for what they cost new but yet Airstream will not make a true toy hauler.

The Axxess shares the aluminum construction but the interior is sparse and nothing near the caliber of Airstream.

[Trnpk Crsr]

Have you thought about powering your existing 12 volt loads using a 48 volt to 12 volt converter? That way, your would only need one 48volt charging system and one 48 volt battery bank. There would be no need for a 12 volt battery. You could install a 48vdc inverter/charger to handle your AC loads when you are away from shore power.

John

[Mgieselman]

You can use a single charge controller on PV side of the batteries and a DC converter on the load side of the batteries to convert down to 12 volts. That would let you ditch the lead acid 12 volt batteries, gaining simplicity and losing weight at the same time.

Victron Energy makes all of the bits you would need, if you are handy and do a bit of research you can do it all yourself.

[Ohiobrits]

Originally Posted by 72dan

But to try and run a 3000 watt air conditioner off a 12 volt battery at 250 amps is incredibly inefficient. Plus the drain on the batteries to discharge at that high of an amperage for a long period can shorten the battery life.
Any time you charge/discharge at more than 1C it is not as efficient.

My batteries at rated discharge (0.3C) can supply 259A continuously. The A/C running pulls about 160A so no issues with battery life. Obviously for a smaller battery 200AHr this could be a concern. My battery temp rises maybe a degree C when running "hard" with the A/C on for a few hours or if charging at 100A from mains. Easy life for this battery compared to EV use or your model airplanes it would seem....

FYI - on your charge voltage - 14.2 V is the set point in the Victron software for charge voltage (Li). 14.6 V is max per CALB (3.65 *4) but is the point where my BMS will inhibit charging i.e. is a safety cutoff. Probably a bit high to be doing regularly.

Originally Posted by 72dan

It is necessary to have two inverters to tie to the grid for two reasons
1) each air conditioner (I have two) will take 3,000 watts to start and without a second inverter I will fry an inverter
2) the shore power is 220 volt so there are two hot wires, each is 110 volts, so one hot to each inverter as the inverters are 110 volts each.

I have a 50A shore power connection also. One 50A leg goes to the 3000 VA inverter charger and powers one A/C unit, all AC outlets, the inverter/charger and all the DC circuits. The second 50A leg powers the second A/C and water heater (electric element). When on shore power, everything works. When not connected I can run one AC and everything else - water heater is on propane in this scenario.

[Ohiobrits]

Originally Posted by dhroberts

Ohiobrits,

I have a question regarding your unit's solar panel / lithium bank configuration. I am new to this whole RV scene, have a 2016 30' Classic and am about to have a 900W / 600 amp hour lithium bank installed.

I believe I understand that you have a 600W panels / 864 Amp hour hour lithium system. Your lithium bank size seems quite robust in comparison to the 600W panels. What were your design thoughts? Did the 27' length of your AS limit you to the 600W of panels?

Thanks for your consideration. Any advice is appreciated. Dennis

If I could fit 400W more solar on my roof I would.... however I have no more room. I might squeeze one more up there with some rearranging but I think I would rather have 2 more panels loose for positioning in the sun if camping in the shade. With 600W of solar I get about 50A of charge to the batteries which is the equivalent of a typical charger/converter running off AC power so not too shabby. It will not, however, keep up with running A/C - that will pull 160A or so from the battery. With 900W of solar you should see about 70A of charge which is a heck of a lot of DC current if you are using just your lights, fantastic fan, furnace etc and some small AC users like TV's and intermittent microwave.

Your setup with 900W and a 600 AHr therefore should be very nice and should be pretty well balanced in terms of solar keeping up with reasonable discharge especially since you are in Texas.

In reality though, if you need to run the A/C for a prolonged period you WILL need a small generator. You will be able to get away with a 2000W unit assuming your inverter is suitably rated and can "power assist" (Magnum Hybrid or Victron units). In this case the Inverter will provide extra current for starting and then the generator will cover the A/C load completely once it is running.

If you don't plan on using the A/C (winter months) you should be pretty much self sufficient with your system assuming good sun.

Enjoy!

[Wolfe]

Have a look at DC marine AC's and DC micro wave's.
Split volt systems are a real pain, Dc to DC inverter for
lo amp 12v things, they are on E-bay low cost.
Used solid 100w on 3" stand off's they need air space for cooling
and block sun on roof.