Such a thing as too much solar power?

[Bumps]

I typically turn off my converter when plugged into shore power, and let the solar system do all the battery charging. It's greener, and my Morningstar solar controller is a much better charger than my simple converter.

X2!

[Gocoffeer]

Bigmess: There is a point to where too much solar can harm system components. If you buy a solar charge converter that was designed to handle 45 amps and you have more panels than it can handle....you can damage the charge converter. Wire sizing is a key in this too....if you have a large amount of panels that have more amperage than the wiring can handle...there is another gotcha type situation. So the benefit to designing a system with use and growth in the decision will save you hassles later.

Someone offered you the VSHEETZ design....I used that excellent layout for my RV solar install and the end result is a very hearty system with growth and integrity at every portion of the install.

[Reed Cundiff]

Gocoffeer

As you note "... If you buy a solar charge converter that was designed to handle 45 amps and you have more panels than it can handle....you can damage the charge converter. Wire sizing is a key in this too....if you have a large amount of panels that have more amperage than the wiring can handle..."

So you have to go with a different design criterion.

Larger arrays are generally set to be in series at higher voltage. We have six solar panels for a total of 1.4 kW. These panels are each 235 W @ 30 V. Our panels are set in two parallel sets of 3 each in series or 90 V to Morningstar MPPT-45. We have had a maximum of 1330 W at mid-summer (max of around 900 in mid-December and 400 today withheavy overcast in southern NM). This is only 14 amps at 90 V. It would 110 amps at 12 V.

Higher voltage and lower amperage means you can use a lot smaller wiring.

Our battery bank of LFP (9.6 kW) is 48 V nominal (son designs and fabricates systems for power companies and businesses and works at higher voltage due to longer transmission distances between panels and battery banks in these uses). The battery bank is four Manzanita Micro 180 A-hr at 12 V nominal. Each battery is 4 x 180 A-hr CALB (Chinese Aviation Lithium Battery) cells.

Reed and Elaine

[Reed Cundiff]

Forgot to turn off Dometic on AC last night and were down -3.2 kW-hrs this morning. It was rather overcast at 8 am and so, o' the disgrace, I plugged the battery chargers (1.5 kW total) to daughter's line power). This gave 1.5 kW and the sun wasn't bad this morning and that added another 0.8 kW) and the LFP battery bank was fully charged (on absorb) in 1.5 hours.

First time we have plugged into line/generator power since August (and that was for one day when it was 100 in Spokane and we were in full shade).

Reed and Elaine

[Smitty77]

Originally Posted by Reed Cundiff

Forgot to turn off Dometic on AC last night and were down -3.2 kW-hrs this morning. It was rather overcast at 8 am and so, o' the disgrace, I plugged the battery chargers (1.5 kW total) to daughter's line power). This gave 1.5 kW and the sun wasn't bad this morning and that added another 0.8 kW) and the LFP battery bank was fully charged (on absorb) in 1.5 hours.

First time we have plugged into line/generator power since August (and that was for one day when it was 100 in Spokane and we were in full shade).

Reed and Elaine

LOL! With 'robust' SP's and controllers, even feeding slower charging AGM's - it is easy to get used to no need for external power!!

Impressive how fast the LFP's were charged...

Best,
Smitty

[twinboat]

I built an AC relay, controled by a Yandina battery combiner, to shut off the AC to the refrig., once volts drop below 13.5. Now I don`t need to remember.

[Reed Cundiff]

Smitty

LFP can supposedly be charged at C/1 or 9.6 kW in our case. I would be afraid to do this just on general nervousness. We were charging at C/0.2 which I think is quite enough. The linear charge rate for LFP is one of the selling points for this battery type. I remember charging our glass mats from generator. It would get to 90% SOC and just sit there. The general belief is that it is good to get LFP down to 60 or 70% SOC fairly often.

We have gotten up to 1330 W to the controller at mid-day summer, but I think we have only gotten about 19 amps battery bank charging at 54 V nominal since their are inefficiences/power losses going through controller. That was still over 1000 W charging.

We are taking off for a week tomorrow and I wanted the battery bank up to 100% before we left.

Will be leaving rig at son's place at 7500' in northern NM when we take off for three months in Ecuador and Peru in Feb. There is a lot of talk on various fora that LFP can not be charged at temperatures below freezing point (may have written on this forum about this but not sure) but the fabricator, Manzanita Micro, said this is nonsense, the physics of the cells means that they are far more inefficient at lower temperatures. So we shall let it sit there and do its daily cycle. There is plenty of energy stored so that even if there are heavy snows, it should last for several weeks without much discharge.

Reed and Elaine

[Bumps]

...In other words, is the controller being damaged because it has to get rid of excess energy that the PVs are sending to the batteries as heat or ??? IOW, as long as the various other components are rated to handle the amount of power that the PVs can produce, but the batteries fully charge while the PVs are still making peak or near peak output, does this potentially cause harm to any system components?

At least for MorningStar, according to their website:

"You can size Morningstar’s MPPT controllers well above the Maximum Nominal Solar PV Input rating without damaging the controller and without the charging current exceeding the maximum output current rating. The controller can limit output current and will run at 100% of rated current output and not higher."

Trying to get better output in low light situations, I have exceeded the nominal wattage for my MorningStar MPPT60 by 200 watts. So far so good.

So to answer the OP's question, at least for MorningStar, at least according to my research and usage, I don't think you would "...cause harm to any system components."

\ken

[Reed Cundiff]

As noted, we have a 48 V battery bank so that our amperage from the MPPT-45 is 27 amps, It is only 14 amps in the wire from the panels (1300 W maximum recorded) to the MPPT.
Reed and Elaine

[BatteryPro]

Originally Posted by nothermark

FWIW if you go all solar and only solar it's a question of a good controller and a big enough inverter. The point I wish to bring up is to understand your usage. If you want all solar that is a lot of batteries and a lot of PV.....

There is no relationship between battery bank size and the PV solar system size. You can have a single 12 volt battery and 1000 Watts of solar power. What is important is having enough solar power to replace what you consume each day. The more you can afford and have the room for, the better. It is very comfortable living with more than enough power. With undersized charging system you will be fretting over it. Remember, the PV solar system you install today will still be making power 3 decades from now. That's a great investment if you spend lots of time boondocking.

Larry

[nothermark]

Originally Posted by BatteryPro

There is no relationship between battery bank size and the PV solar system size. You can have a single 12 volt battery and 1000 Watts of solar power. What is important is having enough solar power to replace what you consume each day. The more you can afford and have the room for, the better. It is very comfortable living with more than enough power. With undersized charging system you will be fretting over it. Remember, the PV solar system you install today will still be making power 3 decades from now. That's a great investment if you spend lots of time boondocking.

Larry

What do you do when the sun is not available?

[BatteryPro]

What do you do when the sun is not available?

northmark,

(just in case this was a serious question) If the sun is obscured, you use another source to charge your battery like a generator or shore power or alternator or wind turbine.

[Reed Cundiff]

If the sun is not shining, then you are in the wrong place. We spent a week in the Olympic Peninsula Rain Forest. We just changed our energy management and turned off inverter when not in use.

It is advisible to choose your camp site so that you will have enough solar to charge batteries. I wrote on another sub-fora here that we called a National Park CG in Olympia National Forest about a spot for solar and was mildly chided, "Sir, this is a rain forest, your solar panels will not do well!"

In high summer and camped in wooded areas, we try to site so that we have sun in the morning and the shade in the afternoon.

We can still charge at around 300 W with overcast skies.

A backup generator to charge batteries is advisable. We have a 1 kW Honda. This will charge the LFP at about 800+ W..

Reed and Elaine

[jackfish]

It has to be a virtual black, rainy overcast for my system to not put out any power. I always get a surprising amount of energy even on cloudy days. As Reed says, you get used to adjusting your energy usage based on conditions, but there are other options to compensate for any shortcomings.