Battery questions

[Gradywhite3535]

How many days would a battery that is say 80% stay charged enough to start after it sits without being used? My battery died after sitting is why I ask. It didn't use the boat for a few weeks or months...also I have dual batteries and I have a dual battery switch which has 1,2,all and both. What's the best way to use the switch so that the batteries stay charged and if the starter battery dies I can use the house? When starting the boat keep it on the starter battery=1 then once I stop put it to the house battery=2 and then when I restart put it back to 1? Is that the best way of going about that? What would you use all for? Thank you

 

[alldodge]

If there is nothing causing a drain on the bat it should last several weeks without issue. Things that can cause a drain are many but one which can do it and need repair is the alternator. If the ALT regulator has an issue it will keep the bats changed but can also cause a drain. Other things are clocks, bilge pumps and many others.

Three stage 2-bank bat charger is best when not in use

If the boat is trailered, turn bat switch to OFF when pulled out.
Switch to bat 1 when starting, once running switch to both.
When stopped for floating switch to bat 2 if you use stereo and other stuff

If you install an ACR (automatic charge relay) then just leave it on bat 1 always unless needed to use to start.

 

[dingbat]

A flood acid battery self discharges @ 5% a month. More when warmer, less when colder.

I got tired of playing the 1-2-both-off game a while ago.

I troll hours on end with a lot of electronics. Battery management becomes a concern.

Installed an ACR and never looked back.

Both for cold start in the morning then flip to 1 for the rest of the day. Off at the end of the day. Plug the onboard charger (starting battery) in for the night every couple of trips.

Works like a charm. One of my better boat related investments

 

[thunder550]

The advice I've seen is to use either 1 or 2, maybe alternate on trips out or set up a system where you use battery 1 on odd numbered days and 2 on even. Only time to use the ALL selection is when neither battery had enough juice to crank your engine by itself, then as a last ditch effort set to All to get whatever cranking power is left in both batteries combined.

 

[Silvertip]

Battery switches seem to cause more confusion than benefit. It is not rocket science and only you can determine the best way to use it. It is a very versatile accessory. Here is how it works (provided it is wired as intended). OFF turns off all power to the boat and engine except for any accessory that is wired directly to either of the batteries. "1" selects whatever battery that position is connected to but it is typically the START battery. In that position you start the engine and all accessories powered from that battery and the engine charging system charges ONLY that battery. It is like that's the only battery in the boat. "2" is the very same thing except you have selected the other battery -- commonly called the HOUSE battery. Again -- start, charge, and accessories are all powered from that battery. BOTH should be self explanatory - but yes, you are using both batteries, charging both batteries and running accessories from both batteries. If you don't intend to sit for hours running a radio or other accessory then just leave the switch on BAT 1. There is no need to switch back and forth unless there is a chance you run down the START battery. If that chance exists you could switch to BAT 2 before you even leave the dock. Then you don't have to switch when you get where you're going and that battery would likely be relatively topped off unless the jaunt only took 10 minutes. For charging purposes select the battery that needs the most charge. And remember, a dead battery will not be fully charged in a 10 minute run to the next spot or back to the dock.