Solar panel

[MattandNaomisRV]

Recommendations on solar panels for my RV

[pianotuna]

Hi BFL13,

60 volts on my Blue Sky 3024di as well. It is MPPT because at the time I purchased it panels were $5.50 per watt (not including delivery).

[BFL13]

pianotuna wrote:
Hi BFL13,

PWM operate at the battery voltage--so they can work with a 24 volt panel--just that it is highly inefficient to do so as lots of energy is being wasted.

Have to watch out for the controller's Voc input limit though. Ordinary PWMs are under 60v ISTR. MY still good Eco-Worthy MPPT is low on that too, so it is not just PWMs that have Voc input limits.

[pianotuna]

Itinerate1,

What is psoc?

Thanks for the data.

[pianotuna]

Hi BFL13,

PWM operate at the battery voltage--so they can work with a 24 volt panel--just that it is highly inefficient to do so as lots of energy is being wasted.

[BFL13]

You can use MPPT with 12-12. It has a buck converter in it, so all it needs is for the input to be at least one or two volts above output.

Possibly people get confused over those PWM controllers that are "12/24". They don't realize that the 24 is for 24-24 and you can't do 24-12 with them.

[Gdetrailer]

samimiles wrote:
Choosing what type of solar is very complex. So many types of panels! Microinverters? Solar optimizers?

No, actually buying "solar" is not all that "complex".

There are folks who wish to squeeze out every little microwatt out of what they bought making this a very confusing and over the top complex thing.

Think of Solar is just a way of adding a extra "charger" to your batteries which only works when there is enough sun and the panels generate enough voltage to overcome the battery voltage.

So, to get your feet wet in solar, you need a panel that is capable of 16V-17V in full sun and a charge controller.

Charge controller prevents the panel from overcharging the batteries and prevents the battery from being discharged by the panels during cloudy days and at night.

Charge controller comes in two "flavors", the old school method is called PWM (Pulse Width Modulated), is the lowest cost controller and can work well for most folks.

The new kid on the block is MPPT (Maximum Power Point Tracking) which requires min panel voltage to be twice of the output (30V for 12V battery) and it can squeeze a bit more efficiency out of the panels by allowing a bit longer charging when the sun is not as strong.

Solar panels and PWM controllers are pretty inexpensive now days and if you are wanting to try, pick out a 100W panel and a PWM controller (go with 30A controller so you can add a few more panels later).

Amazon has lots of choices in 100W panels and some are as low as $80 and PWM controllers around $20 so for $100 you can get your feet wet with solar and get about 6A of charging capacity which can extend time between running a gen..

Add a second 100W panel and you can get about 12A of charging..

[Itinerant1]

pianotuna wrote:
Hi,

The point everyone is missing is that lead acid need to be charged to 100% as often as is humanly possible (without generator use).

Li has no such constraints--so a couple of days of bad weather don't matter. Of course the battery management system might leave you "hi and dry" (which is a good thing given the price) as Li hates being taken to zero volts.

The same is true of SiO2--and as I'm very much part time again--I'll go for a 600 amp-hour bank and probably never need a generator again. The two advantages of SiO2 over Li are cold and zero volts without much damage.

BFL13 is a master of recovering flooded Lead Acid batteries--but he did not have much luck with AGM.

Here is an example of this month from solar, just the beginning of my psoc use for winter. Dec, Jan & Feb the periods of psoc can extend out to 21+ days before a string of poor solar days force a 2 hour generator run give the batteries a couple hundred ah boost. 40 days was my longest of psoc use. This will be the 5th winter of this kind of use.

[BFL13]

"Faster" means restoring the same AH in less time. Since H is shorter, A must be higher to get the same AH.

The scenario has to be where A is higher than it would be charging ordinary batteries over that shorter time period. Plus as mentioned, you have to specify the SOC range.

It can be no faster doing a 50-80, but faster doing a 50-90 due to the 80-90 being still at max amps in one but tapering amps in the other.

Amps can't be higher if the charger is current limited at its max amps over the SOC range in the scenario for the ordinary batteries just by switching to the Li. You can add amps if you have more chargers, where the ordinary batts won't accept more but the Li will.

[KLYoung]

I would recommend Hightec solar panels. You can get them from Continuous Resources.

[pianotuna]

Hi,

The point everyone is missing is that lead acid need to be charged to 100% as often as is humanly possible (without generator use).

Li has no such constraints--so a couple of days of bad weather don't matter. Of course the battery management system might leave you "hi and dry" (which is a good thing given the price) as Li hates being taken to zero volts.

The same is true of SiO2--and as I'm very much part time again--I'll go for a 600 amp-hour bank and probably never need a generator again. The two advantages of SiO2 over Li are cold and zero volts without much damage.

BFL13 is a master of recovering flooded Lead Acid batteries--but he did not have much luck with AGM.

[Itinerant1]

That's not even figuring in watching tv or using microwave and other things during that period of time while it's charging.

[2oldman]

Itinerant1 wrote:
I can throw at it to 98-99% SOC where your lead slows way down much earlier in its SOC trying to absorb the charge. Isn't that faster?.

Yes it is. It's near impossible, or at least I found it so, to charge acid to 100% while boondocking. Seems like that takes 24 hours of steady shore charging.

[Itinerant1]

BFL13 wrote:
An Li does not charge "faster" unless the Li will accept the charger's max amps, but the ordinary battery bank of the same AH size won't. Solar is generally a low amp business, with all day to recharge.

So any so-called "faster charging with Li" is not going to be realized with solar recharging. You would need a much higher amp recharge scenario to get any of that. A pair of flooded batts at 200AH at 50% can accept 60 amps no sweat. 60 amps means a lot of solar and would probably be at 60 only around lunchtime anyway.

There can be good reasons to have Li, but the "faster charging" claim needs to be very scenario specific.

If there is just one scenario that fits the bill of lfp being able to "faster charging " then it charges faster. I won't bother with my scenarios that would fill the batteries "faster" but then I'll take what ever charge the panels will produce but as fulltime boondocker living off of lfp & solar and being able to charge to 14.1v absorb instead of 14.6 or more that lead needs make a difference or accepting everything I can throw at it to 98-99% SOC where your lead slows way down much earlier in its SOC trying to absorb the charge. Isn't that faster?

One more thing I thought about is if I had to use the generator and solar to charge for fast charging which I have done once the batteries were being charged at 175a, that makes for a fast charge off grid.

[2oldman]

I hope the OP is getting some help from all this.