House battery system too low to charge

[hickleyboy]

Need thoughts/advice please
- Boat is parked at a friend's dock while my dock slip is getting serviced. Went for a cruise on a Saturday, docked the boat, shut down all AC systems and just left minimum systems on like bilge etc. A partner was supposed to check on the boat after 48 hours and run genset in order to keep all batteries charged etc. That didn't happen.... Boat sat for 6 nights, not plugged into power. The draw on the battery system was more than expected, apparently.

So we get to the boat after 6 nights. Partner started the boat but not sure what other systems he tried to power up. Engines are on a separate starter battery system and isolated from all other electronics. Apparently no other devices come on line. I get to the boat, I see electrical panel is registering 15.5V There is a 24V house and a 12V house joined by a Vanner equalization system. I go to inverter display to see if current coming from alternators into the inverter/charger to give the house bank some juice. Nothing feeding inverter/charger on the display. I try Genset (separate battery) - starts up and typically it would start feeding AC current into inverter/charger and then charge battery bank. Again nothing.

Then the inverter display goes blank and the last of any battery power dies, still no electronics etc. no charge going to house system.
I check battery banks with voltmeter - 24V system reads 15.5v and 12v system reads 6.5. I am in disbelief how that can be.

All are lifeline AGM batteries - 3 years old. 12V is 440 ah. I've plugged in an outside charger to try and bring the voltage in the battery banks up. Its been 48 hours and not making any progress on getting volts into the battery bank. It is a 25 amp charger, but the run of extension cords are about 150 feet.

Any other thoughts or should I just replace all house batteries? Maybe let it charge for a few more days so the housebank can get enough volts so the alternator or generator will notice they exist?

Other ideas how to get some juice in the battery banks?

thanks!!

PM

 

[SteveK]

Vanner equalization system.
This is something new to me, I have not heard of this before, so I read the manual.

Something drained the batteries and once the 24v battery dropped below 16v and or either battery dropped below 8v, the Vanner auto shut off and will not turn on until voltage is above the cutoff. Disconnect all loads and charge both batteries above 8 volts before trying to start engine. You would have to charge with a 12v charger on the 12v battery. Your 25A charger is not getting through the Vanner to charge the 12v battery. Wait, what charger 12v or 24v

There, I learnt something new today.

 

[dvarholy]

You may need to isolate the banks and charge individually in order to bring the batteries back up. Many modern chargers will not recover if the voltage is badly run down. Is there no way to "cross tie" the start or generator banks with one of the house banks? Your main engine alternators should be able to handle this alone. Is there no separate 12 or 24 volt charger that can be connected to the generator AC output? Unless you have huge 8D batteries, a 25 amp charger may be limited to one battery at a time.

Daniel

'89 Tradewinds 43' MY

 

[Pete Meisinger]

You can sometimes "trick" your charger into delivering a charge to dead batteries by hooking a jump box or good battery to the dead ones. The charger reads the voltage and might start charging.

pete

 

[Figment]

The batteries should still be well within their service life once recharged. Your real mission should be finding the cause of the discharge, no?

 

[hickleyboy]

Thanks for the replies. So I disconnected the link between the 24V and 12V system at the Vanner box. I have a separate 24V charger plugged in charging just the 24V system and separate 12V charging that house bank. All DC and Inverter is disconnected so batteries should be isolated and have zero draw right now.
They have been charging for about 12 hours. I'll check back tonight to see if they have some more voltage.

 

[BruceK]

A charger serving AGMs should put out 10-20% of the total capacity of batteries being charged. No doubt you are using what was readily at hand, but 25Amps charge into 440Amps of battery isn`t enough, being just over half the recommended minimum. Will it work over time, I hope so, but it may not. Good luck with recovering them.

 

[High Wire]

Don’t give up. Isolating the banks from loads and charging separately is crucial. It will take time. Obviously there was a load left powered otherwise the banks would stay charged for months.
Big loads: refrigeration. Small persistent loads: the inverter itself, boat electronics, any lights like in a closet or engine room. Buy a DC clamp on ammeter and track it down.
My guess it was the Vanner system. Unless the system shuts down to zero draw at some point, it would drag the supply battery flat eventually.

 

[jgwinks]

You can sometimes "trick" your charger into delivering a charge to dead batteries by hooking a jump box or good battery to the dead ones. The charger reads the voltage and might start charging.

pete

A set of car jumper cables should be able to do that from one of the good batts to the dead 12v bank. It might work with the 24v bank too. I carry a set in my boat in case it all goes south, I should be able to start the mains off the generator battery which is not connected to anything else.

 

[hickleyboy]

I checked the 24v and 12v system. Both banks registered over 24V and 12V respectively, so the charger worked. Reconnected battery banks to Vanner. All systems started to come alive. panel box showed power, inverter showed power.
I then switched on starter battery and stared engines.

After a few minutes seeing the starting batteries recharge i checked the inverter/charger to see if house banks would start getting juice.
Nothing into the the inverter/charger from engines.
Started generator and the inverter/charger showed power to the house banks, they were now in bulk charge.

So the good news is the two house banks are charged as generator charges them, but now it looks like dead 24v alternator. The engines have a 12V and 24V alternator, so 12V charging start battery but 24v alternator not charging 24V system.
Now I need to trouble shoot if alternator somehow got fried by trying to send a charge to very low voltage battery or maybe regulator is fried too?

Any easy tests I can do?

 

[dvarholy]

I suggest properly recovering any badly discharged batteries prior to troubleshooting the charging system. Deep discharge is a less than healthy state and can shorten overall battery service life. Always be sure of polarity, voltage, and proper charge rate and profile when connecting a portable charger. Never assume a red cable really is positive or black negative.

Once charged, the 24 volt system should show at least 25.2 DC with the charging source disconnected. Let the battery or bank sit an hour to clear any "surface charge". The charge should eventually settle around 25.2 DC. Check any inline fuse or circuit breaker and the wiring itself between the alternator and the battery or bank. Resistance from the positive battery terminal to the alternator lug should be very close to zero ohms. Then check the negative battery terminal from the alternator body to the engine block and on to the negative battery terminal which should also be at or near zero ohms.

Alternator charging output can be roughly checked by disconnecting any charging source such as a portable or onboard charger. Monitor the voltage across the battery terminals. Start up one main engine. Wait a few minutes. The voltage across the battery will begin to rise if the alternator is charging. Somewhere above 27 volts is typical. Remember, this is just a basic function test. Many repair shops and some auto parts stores will test the alternator and or regulator if it is carried in.

Daniel

'89 Tradewinds 43' MY

 

[Darlin]

If you have a smart charger recommend you "recondition" batteries with shore power. This will charge the batteries with higher voltage to return the batteries to their peak operating efficiency.

 

[Iggy]

Did a fuse blow? When voltage goes down, amps go up.

Just a thought...

 

[hickleyboy]

Everything is working now. Not sure why alternators weren't charging but they look to be working properly now.
No fuses were tripped.

Batteries all charged, inverter working, charges working.
I am sure I took some life out of the house bank but I think I git lucky with not having to replace anything.... yet.

thanks
pm