Alternator charging

A

AKlight

.
Jun 22, 2015
15
Hunter 450 Seward, AK
All,

I have a '99 450 with the 8kw Kohler genset.

I have separate switches for my start battery for my motor and generator.

I would like to know if anyone knows (as the manual doesn't seem extremely clear) if the house bank would be charged via the alternator when the main is running.

Inverter/charger was swapped out by the PO so I don't have a ton to go on here and reading electrical diagrams is not my strong suit. I am considering swapping the house bank over to lithium (inverter/charger supports it) as the current house bank is getting a bit long in the tooth and i'm just trying to cover all my bases if you will. I would prefer to not have my lithium bms disconnect and have my alternator consume itself in the process.

Thanks!

Dan
 
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JamesG161

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,815
Hunter 430 Waveland, MS
I have an 9kw Kohler genset. I have the manuals for my old one too.

Let me know how I can help you.

Jim...
 
A

AKlight

.
Jun 22, 2015
15
Hunter 450 Seward, AK
Thanks Jim, I think I wasn't clear.

I am trying to determine if the alternator on my 4jh2 is going to charge both start and house batteries when running. I would like to isolate out the house bank i think.
 
JamesG161

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,815
Hunter 430 Waveland, MS
Yes i understood.

It depends on your Selector switches near your Engine.

Our Genset Alternator charges our Start Battery so it charges it fast.

Then we can Start the main engine, easily.
_____

Next answer with Engine Running....

If you have a special device now called a ACR.

It will charge your House Batteries.

Jim...
 
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A

AKlight

.
Jun 22, 2015
15
Hunter 450 Seward, AK
Ah. Ok, thanks Jim! So I need to figure out if I have an ACR then and i could isolate the house bank there I would assume.
 
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JamesG161

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,815
Hunter 430 Waveland, MS
It was done in my Engine Compartment, but the "Solenoid" broke when Engine Key starts.

I talked to the Guy who Wired our H430 on the phone cost me $35 for 30 minutes.

He told me that Solenoid was cheap and quit working very fast.

Mine has a HUGE heat sink on it, since a lot of AMP needed to charge Batteries.

Here is the ACR link

SI-ACR Automatic Charging Relay - 12/24V DC 120A - Blue Sea Systems

Jim...
 
Stu Jackson

Stu Jackson

.
Feb 26, 2004
23,086
Catalina 34 224 Maple Bay, BC, Canada
AKlight said:
I would like to know if anyone knows (as the manual doesn't seem extremely clear) if the house bank would be charged via the alternator when the main is running.
Click to expand
"Main" what? Do you mean "is the house bank being charged by the alternator on the boat engine when the the engine is running?"
Since you included the genset, do you mean the alternator on the genset.
Please help us to help you.

Otherwise, the answer is: It all depends on how it's wired. If you can't read diagrams, either find someone who can or learn how to do it. In either event you should still check to see what is physically installed on your boat by tracing the wiring, and not depend on a drawing alone.
 
Last edited:
BarryL

BarryL

.
May 21, 2004
1,074
Jeanneau Sun Odyssey 409 Mt. Sinai, NY
Hello,

The only way to be sure is to use a multimeter to check the voltage of the battery / batteries you are interested in. It is very simple and safe to use a Digital Multi Meter (DMM), and they are not expensive. Touch the positive lead to the positive lead on the battery and negative to the negative. the DMM will display the voltage.

To answer your charging question:
Check the voltage of your house battery bank. It should be around 12.7 volts.
Start your engine.
check the voltage again. If it's higher than it was before it is being charged from the alternator. If the voltage is the same then it is not being charged.

You can change your various battery switches (1 2 both off) and repeat the test to be 100% sure of how things are wired.

Good luck,
Barry
 
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Terry Cox

Terry Cox

.
Dec 25, 2000
5,946
Hunter Passage 42 Shelter Bay, WA
Hi Dan. Hunter wired our boat in such a way that the engine alternator does charge the house bank. Our Onan Genset has an AC alternator and charges the house bank when the Genset runs.
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,398
CAL 35 Cruiser #21 moored EVERETT WA
You have good input so far.

Since you are not the original owner of the boat when new, there is really no way any of us can give you a good answer. Once the boat left the dealership subsequent owners may have done any number of changes. To be sure, what is on your boat, you need to do the basics.
  1. Trace the primary red wire from your Alternator to the next connection point. This could be a switch, a fuse, an ACR, even the positive on the battery
  2. Continue identifying each connection till you get to the battery positive connection. Then you know which battery is being charged
  3. A switch or an ACR or even an inverter maybe in the circuit. This is a branching connection. You need to identify all the branches of the circuit
Only after you know the circuits can you begin to address the rest of your concerns.

If you think it is beyond your abilities, then please get a knowledgeable marine electrician to inspect your boat and identify your systems.

Be safe about this issue.
 
Tally Ho

Tally Ho

.
Jan 7, 2011
5,707
Oday 322 East Chicago, IN
AKlight said:
Thanks Jim, I think I wasn't clear.

I am trying to determine if the alternator on my 4jh2 is going to charge both start and house batteries when running. I would like to isolate out the house bank i think.
Click to expand
Start the engine and check the voltage at each battery….if over 13 volts, I would say it is being charged.

Sorry…repeat of @BarryL’s comment (but a good one).

greg
 
F

flightlead404

.
Apr 2, 2021
416
Hunter 38 On the move
AKlight said:
All,

I have a '99 450 with the 8kw Kohler genset.

I have separate switches for my start battery for my motor and generator.

I would like to know if anyone knows (as the manual doesn't seem extremely clear) if the house bank would be charged via the alternator when the main is running.

Inverter/charger was swapped out by the PO so I don't have a ton to go on here and reading electrical diagrams is not my strong suit. I am considering swapping the house bank over to lithium (inverter/charger supports it) as the current house bank is getting a bit long in the tooth and i'm just trying to cover all my bases if you will. I would prefer to not have my lithium bms disconnect and have my alternator consume itself in the process.

Thanks!

Dan
Click to expand
Without understanding the diagram and then checking visually and with a meter no one here can do anything but guess.

However my '07 38 was configured with the alternator wired to the start battery (from memory via the COM post on the switch on the main panel), but such that when the alternator was on, there is a 12v small gauge (12awg maybe) that energized a solenoid which paralleled the start and main.

The original solenoid failed closed by the way in '22 such that house and start were permanently paralleled - I did not know - and I had to jump from a 3rd battery as I was trashing my AGM house batteries at the time unbeknownst to me lol. A replacement source from a reputable supplier failed open weeks later - probably the common trash china counterfeit parts problem that's plaguing many industries.

When you go to lithium house you will want to remove that solenoid and replace with a DC-DC converter. You can charge either side from the alternator, but if you charge the lithium side you'll want a regulator with a lithium profile and to use an Argofet or something to protect the alternator in case of BMS disconnect. Charging the start battery directly and house by the converter and you don't need this device, but its $30 so I would not consider that a big part of the design consideration.
 
A

AKlight

.
Jun 22, 2015
15
Hunter 450 Seward, AK
Thanks for all the input everyone!

I have validated the house bank is being charged by the alternator when the engine is running. Going to work on final wire tracing and what have you in 10 days.
Everyone was super helpful and I appreciate your time.
Dan
 
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D

dlochner

.
Jan 11, 2014
13,072
Sabre 362 113 Fair Haven, NY
Let's back up here. If you are considering adding LFP batteries, there is a lot more to the installation than knowing what bank the alternator charges. Drop-in LFP batteries are drop-in in name only, meaning they built in standard physical sizes, such as Group 31, Group 24. The battery chemistry is quite different, as a result the installation needs to consider a number of important factors.

A good starting place for your education is this article by Maine Sail.

marinehowto.com

Drop-In LiFePo4- Be an Educated Consumer

Lead is Dead! (Except for Starting Batteries) Warning: This article is long and detailed—it may require two reads to fully grasp the nuances and important details. You might be wondering why I’m declaring that lead is dead. The answer is simple:
marinehowto.com
 
D

dlochner

.
Jan 11, 2014
13,072
Sabre 362 113 Fair Haven, NY
Maine Sail just posted an article on a simple LFP installation. If the LFP bank is under 400ah it should work. The key is Victron's new 50a DC to DC charger which can provide a reasonable charging current (50a) for a small to medium sized bank and is small enough to not fry stock alternators of 55a or higher.

marinehowto.com

Drop-In LiFePo4- Be an Educated Consumer

Lead is Dead! (Except for Starting Batteries) Warning: This article is long and detailed—it may require two reads to fully grasp the nuances and important details. You might be wondering why I’m declaring that lead is dead. The answer is simple:
marinehowto.com

marinehowto.com

Easy LiFePo4 Conversion - Marine How To

Easy LiFePo4 Conversion Before reading this article please read the 101 article on Drop-In's: Drop-In Batteries Be An Educated Consumer Hardly a day goes by where we don't see or hear
marinehowto.com
 
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