I'm in the process of installing a LiFePo4 battery that will be separate from the starter battery, only connected through the DC/DC charger.
I need to know where the alternator power goes when it exits the alternator. Does it first go to the charger or the 1,2,both,Off switch? I will be putting the Li battery on its own on/off switch to separate it from the starter circuit. So i will lead the alternator output to the DC/DC charger as in the diagram attached.
Please let me know if you have any info that may help me.
Thanks,
Ed
altenator power out route?
Moderator: KenKrawford
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elk
- Posts: 112
- Joined: Tue May 01, 2012 12:56 pm
altenator power out route?
Ed Kruzel
S/V Emily
Hull #399, 2006 C350
Cataumet, MA
S/V Emily
Hull #399, 2006 C350
Cataumet, MA
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wolfe10
- Posts: 632
- Joined: Mon Dec 11, 2006 2:58 pm
- Location: Ft Myers Florida
Re: altenator power out route?
IMO the most important question is where are you going to locate the Li battery bank.
You can connect the new switch for "Li batteries only" at any connection on the large-gauge cable from the alternator to master battery switch that is convenient since you will wire it through a separate on-off switch.
Certainly, if DC-DC charger is sized to run the alternator at 50+% of output, closer to alternator and larger gauge cable will give less voltage drop.
I don't remember if there is a connection from alternator to starter. If so, the starter would be another place to connect if, say the Li battery bank is in a rear locker, under aft berth, etc.
You can connect the new switch for "Li batteries only" at any connection on the large-gauge cable from the alternator to master battery switch that is convenient since you will wire it through a separate on-off switch.
Certainly, if DC-DC charger is sized to run the alternator at 50+% of output, closer to alternator and larger gauge cable will give less voltage drop.
I don't remember if there is a connection from alternator to starter. If so, the starter would be another place to connect if, say the Li battery bank is in a rear locker, under aft berth, etc.
Brett Wolfe
C350 #180
"Vindaloo"
Ft Myers FL
C350 #180
"Vindaloo"
Ft Myers FL
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MikeGovern
- Posts: 4
- Joined: Mon Mar 23, 2026 4:57 pm
Re: altenator power out route?
In our 2006 350, the alternator positive is wired directly to the ON/Off Switch. My LiPo battery easily fit where the AGMs were--under the seat next to the Nav table.
Marine-How-To recommends you wire the alternator direct to the starter battery to protect the diodes from any inadvertent switch errors. Attached is a basic drawing I initially used to understand/map out the DC engine/battery wiring system. My objectives were to 1) Put in a 300 AMP LiPo house battery, 2) Protect the alternator 3) Leave as much as the original wiring in place as possible.
This setup allows me to use the Both1/2 switch to connect the Starter and House battery by selecting "Both". It allows me the option to start the engine if the starter battery fails. If you do wire the alternator direct to the starter battery, place a placard in the engine compartment so anyone working on the engine is aware the alternator is "hot" despite the position of the ON/OFF switch.
Marine-How-To recommends you wire the alternator direct to the starter battery to protect the diodes from any inadvertent switch errors. Attached is a basic drawing I initially used to understand/map out the DC engine/battery wiring system. My objectives were to 1) Put in a 300 AMP LiPo house battery, 2) Protect the alternator 3) Leave as much as the original wiring in place as possible.
This setup allows me to use the Both1/2 switch to connect the Starter and House battery by selecting "Both". It allows me the option to start the engine if the starter battery fails. If you do wire the alternator direct to the starter battery, place a placard in the engine compartment so anyone working on the engine is aware the alternator is "hot" despite the position of the ON/OFF switch.
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