Dual Switch- One Battery Drains the Other

[CatawbaRinker]

I have a 1995 Rinker Fiesta Vee 265 with a 5.7L Mercruiser Bravo 3 outdrive. It's been a long couple of seasons with engine issues, but we have appeared to put those in the past and the boat is running/performing great. However the tech that originally installed a rebuilt engine is no longer around for me to address a likely battery/wiring issue so I'm looking for suggestions.

I have a dual battery setup with 1 starting battery and 1 deep cycle, both 27's. All starting functions + an automatic bilge is wired to the starting battery while electronics + a separate automatic bilge is wired to the deep cycle battery. The problem I'm having is that when the boat is running, if I have the battery switch to either 1 or 2, the alternator is attempting to charge whichever battery the switch is turned to, but the other battery is getting drained. If the switch is set to 1 (Starter) and the boat is running, the multimeter reads 14v on this battery, but on the deep cycle the volts drop continuously. I discovered this while hooking up my multimeter. If I turn the switch to "both" the alternator charges both batteries, the voltage for both batteries reads around 14v, but what I find is that there is some sort of significant draw on both batteries. While the multimeter reads 14v while the boat is in motion, it drains the batteries to a point where when I turn the boat off I have to wait 10 minutes or so to start the boat back up. I got through last season just carrying a jumper pack. When the boat is off there is no drain on the batteries. Both batteries are new as of last season.

Before I go further looking for a bad connection or ground I wanted to see if there was perhaps anything else that I should be looking at first. The alternator seems to be charging fine as battery it is switched to will show at least 14v when in idle or motion, but the other battery is draining.

Starter relay maybe? I've replaced unfortunately which keeps leading me to a possible wiring issue (ugh!).

Thanks in advance.

 

[alldodge]

With Bat switch OFF (both Bats disconnected) do both Bats stay charged for hours, maybe over night?

 

[CatawbaRinker]

With Bat switch OFF (both Bats disconnected) do both Bats stay charged for hours, maybe over night?

Yes if the switch is off or if the switch is on and the boat is not running the batteries stay charged just fine. I've gone up after a week of the boat not running and they still have near a full charge.

 

[alldodge]

installed a rebuilt engine

If I turn the switch to "both" the alternator charges both batteries, the voltage for both batteries reads around 14v, but what I find is that there is some sort of significant draw on both batteries. While the multimeter reads 14v while the boat is in motion, it drains the batteries to a point where when I turn the boat off I have to wait 10 minutes or so to start the boat back up. I got through last season just carrying a jumper pack.

Check to see if the Alternator orange wire is connected to the 90 amp fuse, and the fuse is connected to the starter post.

I'm thinking the ALT wire is not connected correctly

Assuming there is no ACR or isolator

 

[alldodge]

Also make sure the 90 fuse is not blown

 

[dingbat]

The problem I'm having is that when the boat is running, if I have the battery switch to either 1 or 2, the alternator is attempting to charge whichever battery the switch is turned to, but the other battery is getting drained.

As I would expect when you remove the charge source from a battery

I discovered this while hooking up my multimeter. If I turn the switch to "both" the alternator charges both batteries, the voltage for both batteries reads around 14v, but what I find is that there is some sort of significant draw on both batteries.

As I would expect when you both batteries tied together and remove the common charge source.

While the multimeter reads 14v while the boat is in motion, it drains the batteries to a point where when I turn the boat off I have to wait 10 minutes or so to start the boat back up.

Supposedly "dead" batteries don't self rejuvenate in 10 minutes or so?

Starter relay maybe? I've replaced unfortunately which keeps leading me to a possible wiring issue (ugh!).

Pretty typical failure mode for a starter on the way out.
Had to replace the starter in my truck last summer with the same symptoms.

Start the motor then pull the cable off the starter. See if the discharge problem goes away

 

[Grub54891]

One more thing to note is a bad diode in the alternator will cause a battery to go dead sitting. But that's not your issue, I think. A bad starter as stated will fail to crank when hot. You can install an acr, then both batts will charge no matter where you have the switch.

 

[Bob Sander]

I have a 1995 Rinker Fiesta Vee 265 with a 5.7L Mercruiser Bravo 3 outdrive. It's been a long couple of seasons with engine issues, but we have appeared to put those in the past and the boat is running/performing great. However the tech that originally installed a rebuilt engine is no longer around for me to address a likely battery/wiring issue so I'm looking for suggestions.

I have a dual battery setup with 1 starting battery and 1 deep cycle, both 27's. All starting functions + an automatic bilge is wired to the starting battery while electronics + a separate automatic bilge is wired to the deep cycle battery. The problem I'm having is that when the boat is running, if I have the battery switch to either 1 or 2, the alternator is attempting to charge whichever battery the switch is turned to, but the other battery is getting drained. If the switch is set to 1 (Starter) and the boat is running, the multimeter reads 14v on this battery, but on the deep cycle the volts drop continuously. I discovered this while hooking up my multimeter. If I turn the switch to "both" the alternator charges both batteries, the voltage for both batteries reads around 14v, but what I find is that there is some sort of significant draw on both batteries. While the multimeter reads 14v while the boat is in motion, it drains the batteries to a point where when I turn the boat off I have to wait 10 minutes or so to start the boat back up. I got through last season just carrying a jumper pack. When the boat is off there is no drain on the batteries. Both batteries are new as of last season.

Before I go further looking for a bad connection or ground I wanted to see if there was perhaps anything else that I should be looking at first. The alternator seems to be charging fine as battery it is switched to will show at least 14v when in idle or motion, but the other battery is draining.

Starter relay maybe? I've replaced unfortunately which keeps leading me to a possible wiring issue (ugh!).

Thanks in advance.

The norm when the boat is starting you should be on start battery only. Once running both batteries need to be on. When the boat is off, the starter battery needs to be off and isolated so you don't accidentally drain. When the boat is moored both batteries are off (unless you need the elctronics).

Don't turn both batteries on until you have it started. If the other battery is low because of extended electronics use, it will be a drain on the start battery the instant it is turned on. You don't want unnecessary drains on the start battery, at least until the motor is up and running.

If the voltage at the battery is 14 volts when the engine is running then it is not "draining" It is charging. If you are having trouble starting a hot motor with a known good battery then most likely it's the starter (or starter solenoid) which is failing.

 

[Buzzsaw420]

One more thing to note is a bad diode in the alternator will cause a battery to go dead sitting. But that's not your issue, I think. A bad starter as stated will fail to crank when hot. You can install an acr, then both batts will charge no matter where you have the switch.

What is an acr? Thanks

 

[dingbat]

What is an acr? Thanks

Automatic charge relay

 

[Buzzsaw420]

Automatic charge relay

Cheers.

 

[bruceb58]

First thing I would be doing is to see how much current is being drawn with parasitic draws. Take off a battery terminal and put your multimeter measuring current between the battery lead and the battery.

If your boat is setup with separate house and engine circuits you have the wrong type of switch. You don't use a 1/2/Both switch...you use one of these.

https://www.bluesea.com/products/5511e/e-Series_Dual_Circuit_Plus_Battery_Switch

It let's you combine the two batteries when needed but keeps them seperate at all other times, each powering their own loads.

With a switch like this, you also want an ACR so the engine can still charge the house battery.

https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A