Battery Bank Dying in 3 hours


S

sctttoth

Member
I have a 1999 Formula 41 PC. I have purchased three new group 31 deep cell batteries 105 amp hours each. After fully charged to 12.8 volts, it takes only 3 hours out on the water before they drop to 11.2 volts. While out on the water, I only have the stereo on, water pump, fish finder and head pump running. I don't understand how three batteries only last that long? I guess i need to buy a Victron battery management system to figure it out, but wanted to know if this is common among boaters? It seems freaking insane to me. Any recommendations would also be greatly appreciated. THank you.
 
Suggest start with getting a Clamp Meter and place on the cable feeding the house. Have everything off and turn things on, one at a time. Get the pumps cycle current on and after they shut off. Write down all readings and don't forget the Fridge if that to is used.

Assuming these are lead acid Bats and your question came on the day after the new Bats were installed.
If this is after several 3 hour Bat draining to 11.2V would have me concerned about the Bats. A deep cycle Bat should only drop below 12V rarely, and never below 11.8V because it can damage the Bat.
 
Need more details on how the battery banks are configured....

are all three tied to a single bank? so you have 315ah...or perhaps do you have (3) batteries and only one is for the house bank and the others are for starting? also more details on stereo, some pull more than others.
 
Thank you. I like the bluetooth battery monitor. I have a Pro-nautic 12-50p. 3 batteries 105 ah each are connected in parallel in one bank and yes, should be 315 amp hours. I have a rockford fosgate stereo, 6 speakers plus subwoofer. 500 watt amp I believe. no fridge, only standard bilge pump, water pump, vaccu-flush pump, no lights,
 
The 3 Bats, 300 Ah and 500 watt amp is 40 amp at 500 watts
I'm sure your not pushing the full 500 watts because that would draw 40 amps and would use the 300Ah in 7.5 hours

Add the stereo head (not much), the vacuflush draws a few amps but only for a short time, and bilge is nothing in most cases.
The Sub could be 150 to 1000 watts so this can be a large draw depending

Maybe a 4D or 8D Bat is needed
 
I bought the $40 gizmo. Should have it installed Sunday or next week. Will report back. Right now I have zero gauges on port. If it's slick, I might pickup a 2nd for strb. or throw it on my mower for fun.
 
lol...Victron gear is the best IMO....be carful its a rabbit hole says the guy with a Cerbo GX, (3) smart shunts, (3) IP65s & (4) Smart Lithium batteries.
 
I want to add the 712 to the port battery bank (3 batteries.) Any guesses where the shunt and positive battery connectors go?
 
Still working on figuring out where the shunt and positive lead goes. But, the update is that after being on shore power and charger charging the batteries. When we unplug shore power, battery voltage initially shows 12.8 volts. Within 5 minutes, it drops to 12.1 volts, on its own, no accessories turned on, and holds at 12.1 until i start switching on accessories. I am wondering if it could be an isolator? Will check that next and try to install 712.
 
I am sorry to state the obvious, but did you load test your batteries? There are good load testers (not a multimeter) but a Battery Load Tester that is great for telling you if the battery is shot, just needs charging, has a bad cell, etc. I attempt to start with the easiest solution first. Your batteries might charge up, but if they lose the charge so fast it may mean that the battery (ies) are shot. A bad battery may pull other batteries in the system down......Good luck!
 
jerybak said:
lol...Victron gear is the best IMO....be carful its a rabbit hole says the guy with a Cerbo GX, (3) smart shunts, (3) IP65s & (4) Smart Lithium batteries.
Click to expand...

Where did you end up mounting your Lifepo4 batteries? If in OEM locale, any issue to date with the engine room heat? TIA
 
I replaced all 3 batteries when i first noticed this issue. With 3 new batteries, voltage still drops to 12.1 within 8 minutes of shutting off shore power. I load tested new batteries and they are ok. I will be working on BMV 712 this weekend to try to pinpoint the parasitic issues. Normally, after turning off shore power, the batteries drain to 12.1 v then holds. This time, I turned off shore power and load tested the batteries several times. Batteries maintained 12.8. It's got to be between the battery and accessories as opposed to the charger and battery.
 
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