And Another Battery Question

[Katdaddy]

We just got back from our yearly trip to the Cades Cove. No hookups in the campground, so we are dry camping. I equalized the batteries right before we left and after resting overnight the batteries voltage showed 90%. We get to the campground and set up and voltage shows 70%. I have a solar panel and it would show the batteries fully charged by the end of the day, but as soon as the sun went down they went back down to 70ish%. Sams Club golf cart batteries. The temps at home before we left when I checked everything was in the 80s. Temps in the mountains were low 60s during the day and low 40s at night. I let the batteries rest overnight when we got home yesterday and voltage back to around 100%.
So, does altitude affect readings? I have a chart that I printed of web some years back that shows voltage readings according to temperature. That chart shows the 12.30 reading at the temps we were experiencing as between 90 to 100%. Is this in any way accurate?
With the solar panel we have plenty of juice, just trying to understand what is going on.
As always, thanks for all your help.

[2oldman]

Katdaddy wrote:
The solar would show the voltage up to 13.00 during the day and then it would again drop to 12.30 after dark.

What does 'the solar would show' mean? The panel on the controller? During full sun?

[pianotuna]

Katdaddy,

90% after sitting idle for 24 hours?

[Katdaddy]

I guess I didn't express my question clearly. What I am curious about is, the Sg and voltage showed around 90% charge on my batteries right before I left home. The whole time I was in the mountains the voltage read around 12.30. The solar would show the voltage up to 13.00 during the day and then it would again drop to 12.30 after dark. As soon as I got home the voltage is back up to 12.60. Where did that .30 go during my time in the mountains and why did it immediately show back up when I got home?

[Sandia_Man]

Not sure if you have an issue, too many variables but temp and altitude are not factors in this scenario. I don't fret minor DC voltage fluctuations, and I don't always rely solely on what our solar charge controller, EMS, or my multimeter indicates as it pertains to battery health at any given moment in time.

I find it prudent to have a genny when RVing off the grid, along with our fast charging smart converter I know I can restore amphours into our 12 volt reserves should the need arise. Not parking under trees, RVing in cloudy weather, or just barely using our rig's amenities to eek by are things we have long had to worry about.

[pianotuna]

More details needed.

How many 6 volt batteries?

What total capacity at 12 volts?

How did you equalize them? I.E. with a converter or?

Did you get them up to 14.8 volts during equalization?

[DrewE]

Altitude should not affect battery voltage or charge characteristics to any significant degree--probably not at all for any practical purposes. The chemistry of a lead-acid battery is not affected by ambient air pressure in any meaningful way.

Cades Cove is not at a particularly high elevation anyhow, around 1700 feet or so.

[TUCQUALA]

Having used GC2 batteries for many years, both myself and my son have seen voltages similar to yours. They seem to charge up fully, and when in use drop down in voltage to around 12.6 or so. Not much below fully charged. The biggest plus for them is that they hold the charge and last longer than most 12V batts for some reason. The real number is what your voltage is in the morning, esp if using furnace in cooler weather. Our 4-1/2 yr old 6Vs will be at 12.2 or so in the morning and recover very quickly when the sun starts shining. Sons act similar. Personally (with no actual proof!!) feel that this is a normal pattern for a true deep cycle 6V pair!!

Also, hydrometer almost always shows above 1275 when recharged!!! Never have checked in the morning, no problem, no fault!!!

[Katdaddy]

Batteries are 3 years old and we are very conservative with battery usage. The part that confuses me is the voltage is back up now that we are home. I guess I am going to have to take hydrometer next year to see what it says.

[2oldman]

Voltage alone is not a good indicator of capacity. Your batteries may be old. One solar panel is usually not enough to maintain one battery let alone several, depending on your use. Those temps should not affect things very much.