Separating House and Start/Windlass cicuits

sailman

Super Anarchist
8,325
438
Portsmouth, RI
Current setup is all lead-acid batteries.  Two Group 27 (Start and Windlass).  One 4D for House load.  All three on a shared charge controller, the start and house are on a 1 - Both - 2 - Off battery switch.  I have solar charging, engine charging and 120VAC charging when plugged in dock side. 

Is it possible to connect the Start and Windlass to the 1 - Both - 2 - Off battery switch and get rid of the 4d to be replaced with a LiPo of the same capacity for the house loads?  To manage the charge of the LiPo I would have a separate controller that would take input from the current charging circuit.  The final system would have the house load separate from the starting and windlass batteries but each would share the charging circuit. 

Is this possible?  Wildly expensive?

 

sailman

Super Anarchist
8,325
438
Portsmouth, RI
I suggest the first thing you do is make two drawings - before and after.

It sounds reasonable, but the devil's in the details.
Here is a quick sketch of what I think would happen with the wiring.  The input for charging the LiPo would have to be controlled differently than the current setup.  I would also have to run a set of properly sized cables to the windlass battery to be able to have the combining capability with the starter battery.

View attachment Mystere Battery Upgrade.pdf

 

SimonGH

Member
410
89
Westbrook CT
What are you trying to accomplish?

When you say LiPo I assume you really mean LiFePo4 (Lithium Iron Phosphate)?

If you're trying to just replace your house battery with LiFePo4, then I think you can just swap it out as-is (and don't change anything else).  I would verify the charge profiles of your charger and solar charge controller, but if they can handle AGM then it will be close enough for LiFePo4, especially as you still have FLA in the mix.  I think the biggest thing you need to check is the alternator - the rate at which the LiFePo can "absorb" energy may cause your alternator to overheat (it basically will be pumping out too much current too fast).  An external regulator (like Balmar) would be needed, but will be ok to charge everything in the system (so it would just go between the alternator and the charge divider)

 

sailman

Super Anarchist
8,325
438
Portsmouth, RI
What are you trying to accomplish?

When you say LiPo I assume you really mean LiFePo4 (Lithium Iron Phosphate)?

If you're trying to just replace your house battery with LiFePo4, then I think you can just swap it out as-is (and don't change anything else).  I would verify the charge profiles of your charger and solar charge controller, but if they can handle AGM then it will be close enough for LiFePo4, especially as you still have FLA in the mix.  I think the biggest thing you need to check is the alternator - the rate at which the LiFePo can "absorb" energy may cause your alternator to overheat (it basically will be pumping out too much current too fast).  An external regulator (like Balmar) would be needed, but will be ok to charge everything in the system (so it would just go between the alternator and the charge divider)
I am trying to come up with a better capacity and smaller size for my house battery.  Yes, I am talking about a LiFePo battery.  
With regards to the alternator issue, will a dedicated controller for the LiFePo battery solve that issue or do I still need to check for a regulator on the alternator?

 

SimonGH

Member
410
89
Westbrook CT
Yes, that would work - you can do it pretty simply, you don't need to change a lot there - see pic

You would be limiting your recharge to 20A - theoretically you can charge faster if you went up - 40A or 60A

You may even consider eliminating the charge divider, I believe you can put this between the batteries and have the chargers go directly to the Start battery...?

Screen Shot 2021-10-14 at 4.29.26 PM.png

 
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See Level

Working to overcome my inner peace
Common on battery switch is not the ground, it's the common output/input for a chosen battery/batteries. 

You would create a direct short of the battery when you turned on the switch.

Blue_Sea_6007_Circuit_Diagram.jpg

 

El Borracho

Verified User
6,687
2,656
Pacific Rim
Y'all would be much more successful with your schematics, and less Ibuprofin for me, if you drew them smarter. Positive busses horizontal along the top. Negative (ground?) busses horizontal along the bottom. Current sources and loads vertical between the two. These are more like wiring diagrams, which don't inform about design failures (smoke and flame).

 

2airishuman

The Loyal Opposition
Current setup is all lead-acid batteries.  Two Group 27 (Start and Windlass).  One 4D for House load.  All three on a shared charge controller, the start and house are on a 1 - Both - 2 - Off battery switch.  I have solar charging, engine charging and 120VAC charging when plugged in dock side. 

Is it possible to connect the Start and Windlass to the 1 - Both - 2 - Off battery switch and get rid of the 4d to be replaced with a LiPo of the same capacity for the house loads?  To manage the charge of the LiPo I would have a separate controller that would take input from the current charging circuit.  The final system would have the house load separate from the starting and windlass batteries but each would share the charging circuit. 

Is this possible?  Wildly expensive?
1) Replacing the 4D with a LiFePO4 will require extra steps to protect the battery from overcharge, undercharge, and operation at temperatures that are too high or too low.  Some LiFePO4 batteries have some of this built in, others do not. 

2) Relay/contactor-based battery combiners (which I believe is what you are calling a "charge combiner") are unreliable and create problems that are hard to diagnose.  Design your system in such a way that you don't need one

3) I am not sure what you are trying to accomplish with the 1-both-2-off switch

4) I recommend getting in-person qualified help

 

solosailor

Super Anarchist
4,066
816
San Francisco Bay
The house bank (larger) gets charged from the alternator (with a programmable regulator) and then you use a start/aux trickle charger regulator to have the house bank fill the starting battery, etc.

 

Will1073

Anarchist
744
140
Check out Pacific Yacht Systems on YouTube — they have a great website as well. You need to do a lot more research/education before setting out on this endeavour.

Do you have enough height for golf cart batteries? While heavy, they will simplify (and save a lot of money) the charging and management of your banks (single chemistry).

 
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sailman

Super Anarchist
8,325
438
Portsmouth, RI
1) Replacing the 4D with a LiFePO4 will require extra steps to protect the battery from overcharge, undercharge, and operation at temperatures that are too high or too low.  Some LiFePO4 batteries have some of this built in, others do not. 

2) Relay/contactor-based battery combiners (which I believe is what you are calling a "charge combiner") are unreliable and create problems that are hard to diagnose.  Design your system in such a way that you don't need one

3) I am not sure what you are trying to accomplish with the 1-both-2-off switch

4) I recommend getting in-person qualified help
If I do this I am definitely getting a Marine Electrician to layout the system and parts needed.  I am trying to wrap my head around it to see if my concept is feasible.  To address your points:

  1. My thought was that there would be a dedicated charge controller for that battery
  2. That would be where the Marine Electrician comes in
  3. The 1-Both-2-Off switch would be for the two like batteries (Starter and Windlass)
  4. Yes
 

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