Originally Posted by groundpounder
This subject is also about space, that is getting the biggest amount of total power possible.
Not knowing every RV model, but guessing now they provide a larger space than a standard 12 v car battery. I have what looks like space for 2 regular sized car batteries but installed are 2 6v batteries.
As stated before do not parallel batteries, it is not safe to do that without isolators.
So work from your dimensions and find the biggest batteries that will fit. There are differences in amount of power for the same size. Basically the more they cost the higher power (more lead plate).
Math is math - Total voltage (adding batteries together) times the amp hours of (one battery) when in series gives you the watts (work).
Now another piece of battery 101
Batteries will deliver more total power when discharged slowly. The difference is big.
Also never use a battery below 75% as now you start to cause life limiting damage. Some 12 volt equipment will not operate at low voltages.
Last never leave a battery mostly discharged, charge it right away.
So for you inverter people to do it right you need LOTS of power to avoid deep discharging the battery at a rapid rate.
My suggestion is to have a 24v inverter with charger and 4 - 6v batteries just to operate the inverter.
Originally Posted by gmc
I'm sorry - but there is nothing wrong with running batteries in parallel... Many of our rigs are supplied that way - and it works fine when the batteries are cared for.
It is recommended to parallel identical (in age/specs) batteries for best life - but there is nothing 'dangerous' about a mismatch... It can hurt the life of the pair if one degrades - but that is about it...
Even mismatched in capacity batteries CAN be charged in parallel... I wouldn't view it as a best practice - but it can be done. Each battery will absorb what it needs.
Can 2 six volts in series outperform 2 12v in parallel? Sure - given the right batteries - but that isn't always the practical answer... Space and money and usage requirements can dictate what needs to be used...
Not a bad suggestion as the higher voltage would cut the amps required from the battery source in half... but likely not practical in many cases to carry 4 additional batteries just for the inverter.
Now I know Chance would like to see a 24V RV...
Groundpounder: Every place you said "Power" you should have said "Energy". If you're gonna lecture "Battery 101" you need to get yor terms right.
And as GMC said there is no danger to connecting batteries in parallel. How many 100s of thousands of motorhomes have 2 batteries in parallel without an isolator? How many battery powered toys have batteries in parallel? Danger is not a concern for parallel batteries.