Battery Drain whilst isolators are off

[Bill Lee]

Hi,
I have a Marlin 300, 2007 model.
Recently one bank of batteries has been draining very low/dead whilst both isolators have been turned off.
Here is where I need some experienced help, I am thinking that the only electrics remaining live whilst the isolators are off might be the bilge level sensor and the bilge pump??
Is there other live electrics direct to the battery that might be draining one battery bank?
I am keen to compile a list of electrical items to then go and check for shorting out.
Is there a page in the electrical diagrams that would display “direct to battery” electrics?

Thanks

Mark

 

[wspitler]

Most VHF-FM Tranceivers are hard wired past the BATT switches as are stereo memory. The electrical schematics will only show GW standard items such as bilge pumps, stereo, carbon monoxide detector, etc. not electronics installed by dealers etc.

 

[Bill Lee]

OK, thats helpful.
I will check those electronics with the isolators off.
Thanks

 

[Nachtweih]

I recently had this same experience and found the Battery Charger was charging Bank 1 at 17-18 volts, which boiled the batteries. Replaced Charger and Bank 1 batteries.

 

[Sardinia306Canyon]

Installing two Victron SmartShunt i found 3 cables hardwired to the house and stbd engine battery bank.
As it's a rather new boat to me in this moment i have no idea what their purpose are but wi will verify that (and put some Dyno Labels on them as soon i have time. One of them is most likely the Fusion stereo memory the others i need to verify by trial and error with the help of a buddy.
I also disconnected the Victron 1800W inverter what had a always hot remote On/Off cable and pulled the Victron SmartCharger as i don't have shore power in the marina.
However, my batteries had no issues and there was no drain.

I will check those electronics with the isolators off.

You should pull the battery switch box to see behind what is connected directly and thats usually the bilge pumps and then check the batteries if there are some cables directly wired to the posts or a thicker cable going to a bus bar where the other always hot cables go.
Fastest is to have a helper who check on the dash what is not working anymore after you disconnect the always hot cables one by one , that reduces time as you don't have to walk always back and forth. If you have a Brother or Dyno Label Writer the use it and put a label on the cables and eventually the bus bars, it will come handy again sooner or later.

When your problem happened suddenly then i would check first

• bilge pumps running too often what would point to a water leak, either saltwater or rain water if it rained in the meantime.
• one/both batteries of the bank went bad and can't hold the charge, as Nachtweih mentioned, a bad charger may killed the
• Mouse/rat entered the boat and ate a part of the cable isolation and the damaged cable leaks stray current

If you don't added any electronics i would first check other things than the radio memory or other small devices

Should you know how to use a Amp Meter then you could check that by your self disconnecting one cable after the other while watching the amp meter.

A old school round needle type amp meter or the Victron SmartShunt are a good way to see what is going on with the batteries, the SmartShunt tracks how much Amp's are going in and out and show also actual voltage.

Chris

 

[drbatts]

How long does it take for the battery to sit before it becomes low/dead? How old are the battery's? check your carbon monoxide sensor, if it expires or needs to be replaced it will beep intermittently.

 

[DennisG01]

-- Do an amp draw test to see if you ACTUALLY have excessive current draw
-- If you find excessive draw, simply pull one fuse/breaker at a time while monitoring your DMM
-- Check the fluid level and fully charge the battery... then load test it. The problem could just as easily be a bad battery (regardless of age)

 

[Johnny Dollar]

I also had an electrical issue ended up being a bad ground
test your grounds

 

[Hookup1]

As Dennis said - use a digital multimeter to check amperage draw. Stay by taking the negative off the battery and insert multimeter there. You can do this with positive terminal too but there is usually less stuff connected to negative. Then start turning battery switches off, checking devices and pulling some fuses/breakers.

Also batteries don't last forever (max 5 years). Make sure it's charging properly. 12.8 VDC all chargers off and 13.1 VDC when charging (engine or charger). Older battery chargers have a tendency to overcharge and "cook" batteries. Make sure tops are clean of dirt and water and connections are good.