48 Volt Off Grid Solar Panel System For Travel Trailer

[MD2020]

Working on installing a off grid solar panel system on a travel trailer. I would like to have about 4000 watts available at the circuit panel to be able to run the toaster and microwave at the same time. At other times it will be the refrigerator, tv, and hair dryer. Also estimating about 7kWh/day max usage.

I'm looking to install (4 qty) LG solar panels.
LG NeORN-LG
360Q1C-A5 Mono
(360 watts, 36.5 volts, 9.87 amps) per panel x 4 panels. About 1440 watts total.

The plan is to connect 2 panels in series and each set in parallel. Each set will run 73 volts and 4.94 amps.

The battery will be a 48 volt 200 amp LiFePo4 lithium battery. Nominal voltage 51.2 and charge voltage 58.4. May add another battery in parallel later.

1. Any advice on the proper Victron inverter and MPPT solar charge controller sizing for this setup would be greatly appreciated.

2. Is there any benefit to using two 24 volt 200 amp batteries in series vice one 48 volt 200 amp battery?

Thx,
MD2020

[Mike90250]

Running the toaster AND microwave at the same time is certainly doable. It's only going to cost twice as much. The batteries have to be much larger to power a sustained heavy load. If you had the discipline to only run 1 high power device, you could save a lot of money.

7kwh daily is as much as my house consumes. Have you sized and priced the batteries needed to supply 7kwh ?
[ 7kwh / 48V = 145ah consumed. ] So your battery needs to be able to provide that much without hitting it's upper and lower safety limits

your 1400w pv array will NOT be able to harvest 7kwh daily. I have a 5kw array and in winter often struggle to keep batteries up. I added 2kw a few years ago, my original 3kw was unable to keep up in the winter months.

[MD2020]

Running the toaster AND microwave at the same time is certainly doable. It's only going to cost twice as much. The batteries have to be much larger to power a sustained heavy load. If you had the discipline to only run 1 high power device, you could save a lot of money.

7kwh daily is as much as my house consumes. Have you sized and priced the batteries needed to supply 7kwh ?
[ 7kwh / 48V = 145ah consumed. ] So your battery needs to be able to provide that much without hitting it's upper and lower safety limits

your 1400w pv array will NOT be able to harvest 7kwh daily. I have a 5kw array and in winter often struggle to keep batteries up. I added 2kw a few years ago, my original 3kw was unable to keep up in the winter months.

Mike,

The 7kWh is not sustained throughout the day. Toaster, hair dryer, microwave, tv, and refrigerator will be hit and miss, off and on throughout the day. Toaster may run 5 minutes in a 24 hour period. The hair dryer, maybe 10 minutes, the microwave 15 minutes, and the tv might be 4 hours per day. In all, I expect to use about 3.5kWh to 4kWh/day on avg. The 7kWh per day includes 3.5kWh buffer for weather conditions and latitude location.

Yes, a 48 volt 200 amp hr LiFePo4 runs about $10,000.

As for harvesting 7kWh from the solar panels, I'm cautiously optimistic that high efficiency LG mono panels in series linked to a Victron MPPT charge controller and a LiFePo4 lithium battery bank will have a edge on faster overall solar charging capability. That being said, if I average 3.5 to 4.0kWh of usage per day, I should be on the cusp of being able to maintain the charge on this system.

Any insight on proper sizing of the Victron MPPT and inverter for this system setup would be much appreciated.

Also is there any benefit to using two 24 volt batteries vice one 48 volt battery?

Thx,
MD2020

[Mike90250]

Batteries are not magic. They have limits and specifications. Violate them and you have a blowtorch instead of a Li Battery. FLA is pretty darn forgiving, Li, not much at all.

> be able to run the toaster and microwave at the same time.

Toaster 1,000w, microwave 1,200w Total load 2,200w including inverter losses, you will pull 55A from your 48V battery for the duration of the load. (load + 20% inverter overhead)
That's .25C Are your batteries rated for that ?

I'd suggest you get a inverter no larger than 3,000w (or whatever your battery spec demands) to safeguard the battery.
The larger the inverter, the larger the losses incurred keeping the transistors warm in it. Higher quality inverters have lowers losses, and have better programability. I've got no experience with the gear you are asking about. Victron is a big name, but low penetration in the USA

I'm happy you are so optimistic about your expected solar harvest.

[Ampster]

............
Yes, a 48 volt 200 amp hr LiFePo4 runs about $10,000.
.......

That would be $1000 per KWh. Is that something like a SimpliPhi?

[thastinger]

Working on installing a off grid solar panel system on a travel trailer. I would like to have about 4000 watts available at the circuit panel to be able to run the toaster and microwave at the same time. At other times it will be the refrigerator, tv, and hair dryer. Also estimating about 7kWh/day max usage.

I'm looking to install (4 qty) LG solar panels.
LG NeORN-LG
360Q1C-A5 Mono
(360 watts, 36.5 volts, 9.87 amps) per panel x 4 panels. About 1440 watts total.

The plan is to connect 2 panels in series and each set in parallel. Each set will run 73 volts and 4.94 amps.

The battery will be a 48 volt 200 amp LiFePo4 lithium battery. Nominal voltage 51.2 and charge voltage 58.4. May add another battery in parallel later.

1. Any advice on the proper Victron inverter and MPPT solar charge controller sizing for this setup would be greatly appreciated.

2. Is there any benefit to using two 24 volt 200 amp batteries in series vice one 48 volt 200 amp battery?

Thx,
MD2020

Are you dead set on the LiFePo4 battery. I love them for other uses but I would never use them in off-grid solar. You could buy 8 T-105s for an 8th the price and have 48V 225Ah capacity.
Why not put all your panels in series?

[MD2020]

Are you dead set on the LiFePo4 battery. I love them for other uses but I would never use them in off-grid solar. You could buy 8 T-105s for an 8th the price and have 48V 225Ah capacity.
Why not put all your panels in series?

Great point on the battery recommendation. I used Sunking Off Grid solar design to come up with this plan. The battery should be 400 amps and not 200 amps.

I'm not dead set on using lithium batteries. However the thought process behind LiFePo4 was the lighter weight, extensive life cycles, and depth of discharge. Travel trailers have a limited cargo weight capacity. So lighter weight is important. The disadvantage is higher cost of batteries.

Is your recommendation to not use lithium batteries for off grid systems based on cost or some other factor?

I've read somewhere that partial shade can have an adverse affect on panels connected in series. So the idea behind using 4 panels in combination between series and parallel is to balance current with the detrimental affects of partial shade. Thx.

[MD2020]

Batteries are not magic. They have limits and specifications. Violate them and you have a blowtorch instead of a Li Battery. FLA is pretty darn forgiving, Li, not much at all.

> be able to run the toaster and microwave at the same time.

Toaster 1,000w, microwave 1,200w Total load 2,200w including inverter losses, you will pull 55A from your 48V battery for the duration of the load. (load + 20% inverter overhead)
That's .25C Are your batteries rated for that ?

I'd suggest you get a inverter no larger than 3,000w (or whatever your battery spec demands) to safeguard the battery.
The larger the inverter, the larger the losses incurred keeping the transistors warm in it. Higher quality inverters have lowers losses, and have better programability. I've got no experience with the gear you are asking about. Victron is a big name, but low penetration in the USA

I'm happy you are so optimistic about your expected solar harvest.

You make some good points.

1. I'm looking at lithium batteries due to weight constraints on a travel trailer. The lithiums are about 1/3rd the weight of LFA.
2. I used Sunking's recommended Off Grid solar design post to come up with the specs. The 48V 200Amp is in error. It should be 48V 400Amp.
3. Larger losses on larger inverters is a good point. I may go with the 3000w inverter per your recommendation. Thx.