Help needed

[hummingbirdbassist]

Went to see boat this weekend and found and fixed a few things but here is my question?
Took 2 batteries down with me, when in bank I realized there is a +/- post and and a extra red(+) where does it go? And explain to me the red pinwheel stating, 1 ,2 both how does it work? And if both batts are hooked up how long can I expect them to stay charged or do I need a connector switch to flip on or off when not in use.
Sorry to sound like a real novice with questions and terminology but I am.

 

[Paul F]

Welcome to the site. You will get a lot of answers to your questions. If you have two 12 volt batteries, you can hook each red positive to the red pinwheel switch. One battery to the number 1 and the other to number 2. When you take the pinwheel switch apart you will find three posts. 1,2 and a middle one to carry the current on to your applications. O.K. so far? You can now use one battery to start the engine. This keeps one battery in reserve. After the engine is started you can place the switch to the both setting and charge both batteries at the same time. Most of us buy a combiner a little smart connection that connects both batteries together when one of them is charged to 13.5 volts. When you have a combiner there is no need to worry about moving the switch to both as the batteries will be connected for charging when one of them is charged.

On my first boat we used the number 1 on odd days and the 2 on even days so that the batteries were used evenly. Kind of a set for the day and forget system. If you get another battery so that you have three batteries a starter and a "house bank" of two batteries then there is more.

For this the addition of another switch works best for me. This new switch is on/off and is dedicated to a single starter battery wired through the switch to the starter motor. The red pinwheel 1,2,Both switch is then used to control the "house" battery bank. I wire this bank to number 2 on the switch. The number one is wired to the starter. When the new on/off switch is on and the pinwheel switch is on Both all batteries send power to the starter. The same combiner is used to keep the batteries charged connecting the starter battery to the "house" bank of two batteries. Don't worry about this now, just hook up the two batteries as first suggested and everything will work fine.

 

[tomgrigsby]

As Paul said above, you should have 2 red battery leads and 2 black battery leads. Put a red and a black to each battery. The "pinwheel" switch is your battery selector so that you can choose to run everything from battery #1, or Battery#2, or both. Normally the battery on the Port side is #1 and the Battery on the Stbd side is #2, but you'll have to check to see which is which, especially if the cables aren't labelled and you can't determine by length which one goes to which battery.

 

[Bill Roosa]

Ditto Tom and Paul.
On the subject of how long will they stay charged, well that kinda depends on how much stuff you try running with them. As a general rule you can ignore navigation equipment and the VHF and stereo radios. Lights are medium draw devices. The more you have on the more load and the longer you leave them on the more you draw from the batteries. Anything that moves heat around (reefer, hot water heat, A/C) are very high draw devices and you WILL have to understand how much current they draw to estimate how long you can go before you need to recharge. If you have a volt meter (and it reads correctly)(check it against a probing of the batteries at the batteries with a multimeter) you should keep an eye on it as you are out sailing. Any time the voltage drops near 12.0 volts you are entering dangerous territory, start turning off stuff or start the motor.
You will hear the term amp-hour (AH) used a lot in reference to loads and batteries and charging. It is a measure of energy where you make the assumpton the the system voltage is always the same. 1 AH = 1 Amp for 1 hour, 7 AH=7 amps for 1 hour or 1 amp for 7 hours or...... any combination of amps times hours that equals 7. If you know the amp draw and the time (in hours not minutes!) the load or charger is on you can estimete the AH used or put back. Unfortunately there are numerous charging, discharging, was it absorption or bulk or a float charge....... engineer stuff to get a "real good understanding" of what is going on. Which is why many will tell you to get a battery monitor. you can keep your self out of trouble with a volt meter though for the most part with this document and a pair of reading glasses.
http://www.scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf