Originally Posted by abdabbs
I am looking to do a simple setup with regular batteries to achieve longer elctrical usage will stationary/partying/tailgating. I have located wires from a bus in a salvage yard here in town so I can relocate my batteries to one of my midship storage compartments. Im sure this is somewhat simple but have not seen any schematics that I can find to help me along. What I want is a setup with a switch so, in say, position [l] it runs of the 'starter' battery, in position [ll] it will charge all batteries from the alternator, and in position [lll], while stationary/partying/tailgating/camping, the electrical runs off the other batteries. Im looking for cost effectiveness so deep cycles are probably out. Would 3/4 batteries be good enough? Does anyone have a schematic or such to help me out?
Any and all help is appreciated !!!
TonyC in IOWA
There is no cost effectiveness in using regular vs. deep cycle batteries. You're going to kill 'standard' car batteries so fast that they'll actually cost you more. The thin plates in starting/car batteries are only designed to be drawn down a little bit (usally in the 10% range and always less than 20%) and asking for more will physically damage the plates.
You don't have to go nuts on deep cycle batteries; you'll probably be able to pick up some fairly inexpensive models at Walmart or maybe TSC but they'll sure hold up a lot longer.
For switching what you're asking for is a Battery Switch as used in marine applications. Lets call your starting battery #1 and the house battery (batteries) #2; with the swtich you can run things on Battery 1 or Battery 2 or both. When the engine is running (ie, your alternator is producing power) the switch dictates which battery (batteries) get charged. When the engine is not running (no power from the alternator) the switch lets you choose which battery (batteries) is (are) supplying power.
I don't recommend an isolator; there is too much voltage drop across it and your 'isolated' battery never gets fully charged. Remember, there's only about .7 of a volt difference at the battery between fully charged and 50% discharged.
The manual switch is a pretty inexpensive way to get the job done but you need to be especially careful that you don't leave the switch in the "ALL" or "BOTH" position when the engine is shut down; otherwise whatever loads you're running could kill your starting battery too.
The better solution (in my not so humble opinion ;-0) is to use a 'battery combiner". This is a fully electronic device that is installed between the positive terminals of each set of batteries; that is, between Bank 1 (or Battery 1) and Bank 2 (or Battery 2). Once you start your engine and the voltage comes up to 13.7 volts on the starting battery the electronic switch cuts in and starts charging your house battery (batteries); if the voltage on the starting battery drops to 12.8 volts the VSR (Voltage Sensing Relay) cuts out and protects the starting battery from discharge. If you went with a Battery Combiner you'd have the engine connected directly to the starting battery as normal; all the loads for the rest of the bus would come directly from the 'house' battery (batteries); no battery switch involved. The only connection between the starting battery and the house batteries would be the Battery Combiner between the positive posts. Some of them have a manual overide that lets you connect the two batteries for an emergency start (like the starting battery is dead but the house battery is still ok).
Hope this helps!