3 batteries to 2

[family affair]

Long story short - I have not. I was able to revive my lead acid batteries with a new smart charger, but will likely need to make a change at the end of this season.
I've researched extensively issue #1. Food for thought: if your starboard engine battery bank is setting off low voltage alarms, it is possible those 2 batteries can draw more current than your alternator is capable of producing like that of a LiPo. Ive asked several reputable sources about outboard alternators having the ability to run at max output while current limiting and the answer was yes. In case they were wrong, having the DC to DC chargers would be nice insurance.
At this point the way I would incorporate LiPo would be by having a lead acid starting battery for each engine. They are dirt cheap these days and proven. I would isolate the 3rd battery for the house with a 125 ah Ionic LiPo and use the auxiliary charging leads off each engine to a DC to DC charger. However, I haven't spent the time to understand how to change the wiring to make this work.
Please let me know what you end up doing. I hope to make the change in the future.
Oh and for issue #2, I haven't read anything about that one. Please share a link to the info if you have one.

 

[Sardinia306Canyon]

Dang, i hoped i could lern from your installation
I am still unsure to pull all 3 AGM, use them in my farming equipment and install 3 LiFePo or just pull the second Starbord AGM,
change the electrical system to triple battery setup (what i have in this moment absolutely no idea how to do that on a GW) and use the biggest LiFePo i can fit in the space of the AGM.

Not sure if the auxilary charge cable from both motors will work and be useful
1° you will make a bridge between both outboards, not sure if thats good (except the charger has 2 galvanic isolated inputs)
2° not sure if when they are connected to 2 inputs and f.e. send 10A per engine when trolling if the DC-DC charger will transform it to 20A (what would obiviously a good thing).
The charging lead from only one engine is probably better and safer,
but i'm not 100% sure about that as i never run in this problem.
All my boats had either 1 engine, one or two batteries, or then 2 engines and 4 batteries (2 x engine and 2 x house)

Issue #2 BMS Shutoff
Cheap House LiFePo batteries have the BMS to switch the battery off if something is pulling more than nnn Amps, thats why you can't use them to start the engine or other applications where power draw is above 50 or 100A
LiFePo Starter Batteries have same BMS, but they switch off at much higher loads, 200 or 300A
Now, i am not absolutely sure about that but i guess it can be a issue:
Lets imagine that both Lead-Acid starter batteries die suddenly and you turn the parallel switch to get extra power from the LiFePo house battery.
Honestly i have no idea how much my F300 starter pull when cranking but i can imagine it's more than 100A (even for a short time). This 100+A would make the BMS to switch off the Battery to protect the LiFePo cells from overload (what is correct) but then the parallel would not work. If one starter battery from either outboard is ok and can start one outboard then it could be used in parallel to crank the other outboard with the dead battery.

Just to exclude this hypothesis i would buy and install a starter LiFePo who is able to deliver enough amps to crank the outboard.

Chris

 

[family affair]

1⁰ I have not investigated if that can be an issue. I thought I read about this being ok in another thread on a different forum.
BMS cut off is a non issue on the Ionic dual purpose battery. It is a 125ah starting battery.

 

[SkunkBoat]

I have been using both Aux charging cables to a separate House Bank of two 24DC since 2018. This was with Yammies OX66 and now Zuke DF200APs.
The leads go to one positive and negative point as they are parallel and technically ONE battery.
The motors each have their own 24M starting battery.
The ProMariner 3 bank charger keeps them all winter. I don't use the charger in water unless I am not using the boat...which is never...

A parallel pair of 24DC lead batteries runs my VHF,MFD,sonar, nav lights, LED spreaders and LED UW from dusk to dawn, engines off, 100 miles out.
Stereos with amps are battery killers. Listen to the waves and the pilot whales blowing...

You mentioned things blipping when starting. You should separate the House from the Starboard Starting Battery.
Also check for green corroded connections from the battery all the way to the power plugs on electronics.
Especially blade fuses and fuseholders. AND the House red button breaker...which you should throw away and replace with a switchable MRCB when you isolate the House from start.

https://www.greatgrady.com/threads/new-battery-config-for-265.25744/

 

[Sardinia306Canyon]

BMS cut off is a non issue on the Ionic dual purpose battery. It is a 125ah starting battery.

Good, then it should work

The leads go to one positive and negative point as they are parallel and technically ONE battery.

Yeah, you are right and it should not matter if there is one or two batteries as they are parallel.

Well, then i guess one of this Starter batteries with charge limiter i found online would do the trick without the DC DC charger.

Anyone has a idea how i can eliminate the house +12V from the starboard twin battery bank and attach it to the "new" single house battery, whatever battery it is. Just moving the cable going to the house bus bars or something more complicated?

I guess i have to pull new Aux wires from both engines to the battery as they are not needed in the current GW setup.

Forgive me the questions but this boat has a lot of cables as it has a lot of electronics, including a Victron 3 bank charger (but only 2 banks connected) and a huge Victron 1800W 220V Inverter the old owner had installed to feed a capsule coffee machine and sandwich maker sitting on the small "desk" on the side of the toilet.
As i don't have shore power on my slip and don't need 220V for coffee and/or sandwich maker probably just eliminate it.
Also, as the space on the wall above the batteries is occupied by the inverter, but i believe i could use it to mount my GSD26 Blackbox.

Chris

 

[SkunkBoat]

I am not looking at your manual but probably there is a 6 gauge red wire from the House red button breaker to the FEED terminal of the Stbd battery switch.
That wire gets removed from the starboard switch and goes to the new House bank. Replace the red button with an MRCB so you can turn off the house.
The 6 gauge black wire needs to move to the House bank too. Then you need to provide charging to th house via Aux cables or ACR.

Your boat may have a different original setup than mine. Possibly multiple red buttons and switches right next to each other.
It may have a DC distribution panel with breakers?

 

[Sardinia306Canyon]

Thanks SB
I will check next time and make some photos of the battery compartment with all cables and stuff ex owner installed there.

I will probably not touch the GW Battery Panel on the transom and install a additional house battery and parallel switch in the battery compartment under the dash. Or a hidden electronic battery switch.

Chris