Re: Run a Optima AGM in Parallel With a Walmart Deep Cycle Battery?
Sigh.... NO NO NO NO NO! you can connect dissimilar capacity batteries in parallel with no problems long as they are the same voltage. I.e. both 12volt batteries. They can be different groups, sizes, capacities, colors, side terminal vs top terminal, they don't even have to like the others in-laws. In parallel they will equalize voltages and discharge at the same rate. If you have a 200 ah and a 100 ah in parallel, you now have a 300ah battery bank. They will always read the same voltage, and be at the exact same state of charge. Thus if you put a partially discharged battery in parallel with a fully charged one they will equalize some where in the middle. The larger capacity battery will take more of the load then the smaller one.
Where you may have a issue is during charging, and only because they are of dissimilar construction. AGM batteries have a different charging profile than lead acid. The proper way to charge would be to place a switch between them, and charge one on the lead acid setting of your charger then switch to the AGM and charge the other.
While were on the topic, running batteries in parallel doesn't exactly give you the amount of the two capacities added together. Due to internal resistance and some other big words I don't feel like typing out there is some loss of capacity. Installing a battery with between the two, and running one at a time will give you greater capacity, then running them in parallel.