Fast battery discharge

[colld0114]

A new to me 2017 fb with roof go power Solar. In storage for over two years and used infrequently before never dry camping. I replaced the 5 year old interstates and set out for 5 nites of dry camping.
The batteries drained fast with only a few lights on, no inverter, furnace before sunrise to-get chill off.
Day 2,3 and 4 similar
5 pm sunset 12.7
8 pm 12.6
5 am 12.4
Furnace on
Furnace off 12.1
Sunrise
7.15 am 12.3
11 am 12.9
2 pm 13.3
Sunset 12.6
Repeat
Find it hard to believe for 50% to 90% charge in a few hours before the strong sun.
I was hoping for bad batteries but they check out in good working order.
I’m thinking maybe the converter.
Any ideas.
Thanks
Doug
Fresno

[n2916s]

So, the converter takes 110vac shore power and makes 12VDC for battery charging and lights, fans… Boondocking, the converter doesn’t do anything (unless you run a generator).

The solar controller is what takes the output of your solar panels and provides it to the 12vdc system.

What size and how many solar panels do you have?

[Wazbro]

Is that no inverter at all or you didn't use it?
If it is you didn't use it was it actually turned off?
When on and not being used some inverters use over 1 amp.

Was fridge in propane mode or 12v?
If in 12v it will drain power quickly.

[Rolind]

Do you have a battery monitor or shunt like a victron 712 or a victron smart shunt? If no, and you are using voltage to determine state of charge, you are going to have a very hard time sorting things out. Other info may be helpful such as how large is your solar array needed your battery bank and the power source of your fridge as suggested above.

[colld0114]

I have the factory go power with their PWM monitor. On the roof are two flexible 100 watt. Not enough for a rapid charge.

The frig has run on propane

Never used the inverter, will check if off.

Thanks and will advise about inverter.

[richard5933]

First - converter has nothing to do with the equation when dry camping. It will just sit there and only the solar charge controller has the ability to put juice back in the batteries.

If you have the standard pair of Interstate lead acid batteries, you have a combined total of about 160Ah of capacity if they are both charged to 100%. From that 160Ah, you only have about 80Ah which is actually useable since you don't want to run lead acid batteries below 50% SOC.

80Ah is not that much and can be used up faster than you'd expect, especially if those few lights you're running are incandescent and not LED. Don't forget that you were likely also using your water pump, and don't underestimate the amount of power that the blower in the furnace can consume. Some people have trouble making it through one night if they have to run the furnace at night.

Another thing to keep in mind is that the voltage showing while you run the furnace (and for a short time after) doesn't accurately reflect the batteries' state of charge. To get an accurate voltage reading you have to shut off all loads and wait 15-30 minutes for the voltage to even out again. Really difficult to do if you're trying to warm up a cold trailer in the morning.

As mentioned earlier, a shunt based battery monitor will be a great help here. It will count the amps in/out of your batteries and give you a true picture of how much each device draws down your batteries. With that information you can better decide how to fine tune your use to lengthen the time you can go between charging. Otherwise you're just making an educated guess.

[Wazbro]

Originally Posted by richard5933

If you have the standard pair of Interstate lead acid batteries, you have a combined total of about 160Ah of capacity if they are both charged to 100%. From that 160Ah, you only have about 80Ah which is actually useable since you don't want to run lead acid batteries below 50% SOC.

One thing not mentioned here is that in cold weather the battery capacity is reduced. Is that by 5, 10, 20, or 30 amp hours? That depends on how cold it is and how fast you draw power from the batteries. Also there is the issue of temp compensation while charging, battery voltage verses charge percentage changes with temp.

[StevenD]

Greetings. My guess is that the 13.3 volts at 2pm was an input voltage from the solar controller, not the battery voltage. The 12.6 volts at sunset likely is the battery condition at the end of your solar day. So the solar panels are not getting you back up to a full charge.
Steve

[colld0114]

new operator error. I left overnight with the frig in off position.
Inverter and water pump off. 7am 12.7 still full charge, problem found.
I am assuming the auto/lp switch was on auto and draining batteries. Thanks for the response. This is a new to me airstream used a handful of times and stored for past three years. Glad it was me and not the airstream
Doug