2019 C28 Battery Troubleshooting - Heavy thruster usage cuts house power

[GunkHoling]

I think my AGM batteries know I'm considering lithium. After some rough house battery treatment it seems when I operate the thrusters for a total 30s-45s (in bursts), I've lost house power until I flip the cross-over. I'm assuming the house batteries are shot and need replacement, but is there anything else I should be on the lookout that could be the cause?

For a little background, I believe the house batteries are original from 2019. Since I've owned the boat in the last ~year the house bank suffered 2-3 days of being deeply discharged ~3 months ago when shore power was disconnected and solar did not maintain, the fridge, wine cooler, and peplink router DC loads. The Garmin showed 9v and was power cycling when attempting to operate. More recently, our engine battery drained overnight after the ignition was left on. Attempting to cross-over with the house wouldn't start the engine, but drained the house bank to the point that instruments wouldn't turn on until we jumped the engine and used the cross over. Now I've twice had all house loads shut down after thruster operation.

I'm assuming the following is happening -
Boat plugged into shore power brings al batters up to fully charged voltage, ACRs close and batters are in parallel.
While underway, alternator maintains battery charge, ACRs remain closed.
Extended thruster operation draws current and voltage drops across the batteries. ACRs start closing, eventually house battery is isolated from engine battery as well as alternator current.
Unhealthy house batteries rapidly decrease in voltage and eventually shut down

I couldn't find any external thermal breakers in my thruster wiring that could have somehow been miss wired to the house loads. I checked the bluesea house load breaker and it didn't trip. I believe the only thermal breakers that would automatically reset would be part of the thrusters themselves and auto recover once temperature decreases.

I'll be back to the boat in a few days to troubleshoot further, but want to make sure I'm not missing any other possible causes. I do have new AGMs (Odyssey Performance ODP-ACE31M w/ bluetooth) on the way to replace the house bank. I still plan to move to lithium, but thats a much longer project than I want to start now.

 

[William Sanborn]

I think my AGM batteries know I'm considering lithium. After some rough house battery treatment it seems when I operate the thrusters for a total 30s-45s (in bursts), I've lost house power until I flip the cross-over. I'm assuming the house batteries are shot and need replacement, but is there anything else I should be on the lookout that could be the cause?

For a little background, I believe the house batteries are original from 2019. Since I've owned the boat in the last ~year the house bank suffered 2-3 days of being deeply discharged ~3 months ago when shore power was disconnected and solar did not maintain, the fridge, wine cooler, and peplink router DC loads. The Garmin showed 9v and was power cycling when attempting to operate. More recently, our engine battery drained overnight after the ignition was left on. Attempting to cross-over with the house wouldn't start the engine, but drained the house bank to the point that instruments wouldn't turn on until we jumped the engine and used the cross over. Now I've twice had all house loads shut down after thruster operation.

I'm assuming the following is happening -
Boat plugged into shore power brings al batters up to fully charged voltage, ACRs close and batters are in parallel.
While underway, alternator maintains battery charge, ACRs remain closed.
Extended thruster operation draws current and voltage drops across the batteries. ACRs start closing, eventually house battery is isolated from engine battery as well as alternator current.
Unhealthy house batteries rapidly decrease in voltage and eventually shut down

I couldn't find any external thermal breakers in my thruster wiring that could have somehow been miss wired to the house loads. I checked the bluesea house load breaker and it didn't trip. I believe the only thermal breakers that would automatically reset would be part of the thrusters themselves and auto recover once temperature decreases.

I'll be back to the boat in a few days to troubleshoot further, but want to make sure I'm not missing any other possible causes. I do have new AGMs (Odyssey Performance ODP-ACE31M w/ bluetooth) on the way to replace the house bank. I still plan to move to lithium, but thats a much longer project than I want to start now.

Have kinda the same issue.... Someone left a fan switch on for 3 or 4 days... House Batteries were at 4+ volts when I checked on the Boat, but Thruster and Start Batteries were at 12.5. Put a charger on House Batteries and they came back to 14 volts, but on this last weeks Cruise found that they had no more Stamina then my old body with out the Alternators push when the Fridge kicks in. Large Cooler on the Swim Step was a Savior.
Set up with Group 27 Flooded, but after I Load Test them plan is to replace with Group 31 Flooded, and then confirm that the Fridge is free of shorts.

Bill

 

[Cutwater28GG]

probably a couple of things

1. the house batteries are not well and need replacing.
2. the ACR's may not be protecting the house battery when the thruster is in use. (My Theory) my understanding is there is a timeout like 30 seconds on the acr's at a certain voltage before they change state of connection. if you have a massive load during that window you are essentially using the thruster and house batteries to power the thruster. if the house batteries are near end of life, this might be enough to remove any available state of charge from the house batteries and result in the experience you describe

Ive had a simialr experience with a solar charger holding volts above the threshold as the boat swings at anchor and the ACR not closing quickly enough that after a day the engine battery and house drain together. - basically making the ACR completely useless.

I swear that most boats of our don't need lithium they just need a better wiring solution without the ACR's installed in our boats.

 

[GunkHoling]

Thank you both, at least it helps confirm my suspicions and to proceed with the house battery replacement.

re: Lithium - I agree its probably not that necessary. If I didn't think I needed to replace the existing AGMs already I wouldn't have been considering it. Knowing the likely age of the batteries, and an undersized (low CCA) engine battery I figured I'd just go to lithium and not think about it again. Lithium is still last on my list post other modifications.

 

[TristenT]

probably a couple of things

1. the house batteries are not well and need replacing.
2. the ACR's may not be protecting the house battery when the thruster is in use. (My Theory) my understanding is there is a timeout like 30 seconds on the acr's at a certain voltage before they change state of connection. if you have a massive load during that window you are essentially using the thruster and house batteries to power the thruster. if the house batteries are near end of life, this might be enough to remove any available state of charge from the house batteries and result in the experience you describe

Ive had a simialr experience with a solar charger holding volts above the threshold as the boat swings at anchor and the ACR not closing quickly enough that after a day the engine battery and house drain together. - basically making the ACR completely useless.

I swear that most boats of our don't need lithium they just need a better wiring solution without the ACR's installed in our boats.

I think I had the solar do the same thing earlier this summer. I noticed my engine battery voltage drawing down a little lower than what was normal while sitting on anchor. I can’t remember if I did something or if eventually the ACRs did their job and separated the batteries. If a person really wanted they could replace the ACRs with switch or the remote switch ACR that I believe require manual switching to combine the batteries

 

[JonR]

My thruster battery is totally independent from my house and engine batteries. I'm confused (2014 C28 Cutwater). I've found that using the crossover switch to start the boat does not work well but I've actually jump started the engine battery with the thruster battery when engine battery was dead. I don't yet understand why using the crossover switch does not work when jump starting does

 

[scross]

My thruster battery is totally independent from my house and engine batteries. I'm confused (2014 C28 Cutwater). I've found that using the crossover switch to start the boat does not work well but I've actually jump started the engine battery with the thruster battery when engine battery was dead. I don't yet understand why using the crossover switch does not work when jump starting does

In the old days (2007-2015) FM had three battery banks 1. Engine 2. House 3. Thruster & Windlass.
Sometime around 2015 or 2016 the windlass was moved off the thruster+windlass battery bank and on to the house bank.
The crossover switch combines house bank with engine bank to get you started if the engine bank battery died. In the old days the windlass plus thruster battery bank had nothing to do with the crossover switch. In the newer configuration only the dedicated thruster battery is not involved when using the crossover switch.
If you are having to use the crossover switch to get the engine started in your 2014 C-28 I would recommend testing both all the batteries in the house bank and your starter battery. Some or all of those batteries may be going bad.
Since your thruster+windlass battery is effective when jumping with the engine battery to get a start, it seems to me that your windlass+thruster battery is reasonably healthy.