Stock AGM House Batteries

The stock house batteries of the Solis consists of two 105ah AGM batteries totaling 210ah.  It is important to understand what amp hours (ah) means.   Amp hours are the amount of time a 100% charged battery can provide 1 amp of power.  There isn’t any electrical item that uses exactly 1 amp in the Solis, but the main overhead lights are close.  For a 210ah system, the batteries should be able to keep those lights on for approx 210hours.  There are a lot of caveats and nuances to this though.

AGM batteries are not very efficient and in order to keep them healthy, they should never be run below 20-30% of a full charge*.  This has been simplified in many places to 50% or “Just don’t run the batteries down to 50%” which is a reasonable rule to follow.   Which of course means that the original 210ah only has 105ah of usable power.

Here are a few examples of devices and their approx ah usage.  These are all very approximate and can vary widely.

Approximate amperage for stock Solis devices

Using the example chart above, if the lights are on and the fridge is cold there is (0.8ah + 2.5ah) 3.3ah being used. Fully charged stock batteries could run those devices for 105/3.3 ~ 26 hours before the batteries are starting to get into the dangerous <50% charge status.

Couple of things to keep in mind about AGM batteries:

• AGM batteries can be depleted to 20-30% and fully recharged around 800 times. If the batteries fall below 20-30%, that approx 800 charges starts to drop. There are way too many variables to say by how much or to predict the actual life span. Completely depleting the batteries to 0% a few times probably won’t kill them, but consistently doing it will reduce the total ah the batteries can hold. This is a exponential affect, so the more “damage” you do the batteries, the less and less and less charge they can hold.
• AGM batteries when fully charged will show a resting voltage of approx 12.7v. When at 50% charge they will show approx 11.9v. This doesn’t mean anything for your devices, as most 12v devices will work the same with anything from 9v to 14v.
• Typically the State Of Charge (SOC) SOC  is calculated by the resting voltage of the battery. Resting voltage just means the voltage of the batteries that haven’t been charged within 2-4 hours. 11.9v is 50% and 12.7 is 100%
• AGM batteries are heavy, 50-80lbs

Now in real world RV usage the batteries are used a little and recharged very often from driving, solar or shore power. So the 800 isn’t really a practical number. With what the RV industry calls “average” usage, AGM batteries should last 3-5 years depending on how well they were maintained.