Put the Solar to the test.

[Vintage465]

So just a bit of back ground. I tried to dig up my original post for a reference but failed to find it. So the long and the short of it is: I bought a 20fq Creek Side and had 300w of solar installed controlled by a Samlex Controller. It feeds to 6v interstate batteries in series. I was able to go to the the Mojave Desert where it was less than 30 degrees at night, run the forced air furnace to keep the trailer @ 60 degrees each night for a week and the lowest voltage I woke up to was 11v(kept it at 65deg. that night). Most mornings I woke up to 12v or better. Then the solar would charge it up during the day and I would go to bed with 12.6v. Went on and on like that for a week. I consider this a win as we can keep the trailer warm enough for out tastes and there is no generator running to charge things up.

[RJsfishin]

If batteries were down to 11 volts under zero load, you would know it, because the water pump would probably hardly run, and the lites would go out when the pump tried to start. 11 no load volts is a dead battery.
Here is a "no load" chart

[All_I_could_aff]

I'm a little confused by the "major watts like 80 -90 and serious amps like 24-30"

[Vintage465]

Well, I will have to do a little more testing and documenting things like "under load" or not. I don't remember right now if the 11v episode was under load or not. I do know she was pushing out major watts like 80-90 and some serious amps like 24-30 when the sun started hitting the panels. The best thing is comparing it to the past when I would arrive at the desert on Saturday and by Wednesday things were starting to get dim without even running a furnace! I would have to start the tow rig and plug in to charge the batteries. This time we ran the furnace every night and the solar did all the work and we just stayed toasty warm.

[2oldman]

rjxj wrote:
.. wonder what the conversion loss is when going from 48 back to 12.

I don't know.. so far it's so small I haven't noticed a thing.

CA Traveler wrote:
...what is your analysis/summary/expectation of your setup?

The smaller wire is of course a real benefit. A/c runs no problem.

There's one thing I didn't even think about..the inverter idle draw. The specs say less than one amp AT 48V. Well.. that's 4 amps @ 12v. So, there's a definite disadvantage there. But with 640ah of batteries, it doesn't make a whole lot of difference. It might matter more to someone else.

It's very likely I'll have a 50% off sale on some 24v system stuff..soon.

[CA_Traveler]

2oldman wrote:

CA Traveler wrote:
Plus all the bucks you're spending on 24V and now 48V. :S

ouch

Yes but I have and do read all of your posts with interest.

Now that away from the Q solar dealers and have your new voltmeters what is your analysis/summary/expectation of your setup?

[azrving]

2oldman wrote:

CA Traveler wrote:
Plus all the bucks you're spending on 24V and now 48V. :S

ouch

I see mention of your 48 volts and it reminds me of that pile of 80 volt max to 13 v converters I had laying around somewhere. Makes me wonder what the conversion loss is when going from 48 back to 12. I have one on my 48 volt pontoon boat that powers the 12 volt accessories.

[2oldman]

CA Traveler wrote:
Plus all the bucks you're spending on 24V and now 48V. :S

ouch

[CA_Traveler]

2oldman wrote:

smkettner wrote:
Nothing wrong with voltage dropping into the elevens periodically while under load. The battery is supposed to work for you, not you working for the battery.

Good point. I suppose I could make batteries last many more years if I didn't use them!

You can certainly do better that that. Just don't buy them to begin with. Plus all the bucks you're spending on 24V and now 48V. :S

[2oldman]

smkettner wrote:
Nothing wrong with voltage dropping into the elevens periodically while under load. The battery is supposed to work for you, not you working for the battery.

Good point. I suppose I could make batteries last many more years if I didn't use them!

[azrving]

10:00 am
Two 130 w panels are putting out 17.4 A, 16.1 A hitting batteries, down 46 ah with 32 ah having been replaced. 13.6 volts, 15 Celsius & windy. Tilted.

[tpi]

I have similar system 300W solar w/ 300 AH of AGM batteries. I run the furnace at 60-64 degrees (my furnace draws less than 4 amps when running). All LED, and all electronics are modern and efficient. No battery usage for heating water, cooking etc-all propane for that.

Usually 12.5 ish when I get up (and nothing's on). Usually up to the 14.4 volt regulation point by 11 or 12 AM.

A few days of cloudy cold weather could throw this for a loop-with the furnace running 24 hrs and little recharge-but there is the generator. In general my off grid trips are a week or less and if there is a deficit, the solar can handle it later.

[time2roll]

scrubjaysnest wrote:
This chart is only ball park and isn't correct for many batteries.
For my Exides 90% is 12.7 for an example and 50% is 12.4 volts.
Best to check the manufactures website for your specific battery.

Resting or under load?

The chart is for about 5 to 25 amp load like when the furnace is running.

[time2roll]

Nothing wrong with voltage dropping into the elevens periodically while under load. The battery is supposed to work for you, not you working for the battery. Your system seems to working very well for you and will serve well for a long time.

[Vintage465]

Well, I have to say it didn't realize that 11v was "dangerously" low. I also didn't realize that 12v systems dropped such high percentage points for such low decimel drop. Most mornings it was around 11.9-12v. Just the one morning that we had a visitor that has a bad back so we kept the trailer at 65 degrees. I don't see me going to a different type of heat. I am aware and have been for many years that the forced air type heat in an RV is super parasitic on the batteries but there is not room in this rig for a catalytic type heater and it's not my thought that we will be in weather colder that 20 degrees, at least not for any length of time. I will likely install two more 6v batteries to keep things happy. I just love posting a thread like this and getting all this great information!