Alternator only charges 'Start' battery not house bank. How to add them?

[SteelCruiser]

The alternator on my Lister STW3 connects to and thus charges ONLY the 'start' battery.
.
There are three other batteries onboard, wired completely separately from that 'start' battery.
.
My question, how to ' join that alternator' to the house system?
Any suggestions, "watch out for" comments?

( In the hand drawn picture attached , the big "brick wall lines" attempt to describe the separation ).


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[a64pilot]

Is there a battery switch? Does it have the word Both on it?
If so then just select both, that gangs all the batteries together, so all will charge, but also all will discharge, so some will select house when engine off.
There are other ways of course, but this is I think the simplest.


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[jstevens]

A battery combiner or echo charger are commonly used to allow an alternator with a single output to charge multiple battery banks. One can easily be connected between the positive terminal on the start battery to the other bank.
However, it would be more effective to have the alternator charge the house bank (assuming those other batteries are a house bank), and then have the combiner/echo charger pass the charging current to the start battery. There have been a number of threads on the use of combiners and echo chargers. You can also learn more from the manufacturers' website. Blue Sea is probably the main manufacturer of combiners and the Echo Charger is, I believe, a Xantrex product.

John

[Reefmagnet]

A dual battery voltage sensitive relay will do the job with regular flooded lead acids. You won't need to make modifications to your existing wiring and the relay is cheap and easy to install.

E.g.
http://enerdrive.com.au/product/140a...nsitive-relay/


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[Lepke]

The easiest way is install a multi battery isolator. See picture. Pictured is for 3 batteries. One terminal goes to the alternator (in place of the wire going to the single battery) and the other three to batteries. Your solar charge controller may need to be isolated, too.
If you know what you're doing, you can make your own with diodes and a heat sink.
Another way is manually with switches heavy enough for charging amp flow.

[AnchorageGuy]

Originally Posted by jstevens

A battery combiner or echo charger are commonly used to allow an alternator with a single output to charge multiple battery banks. One can easily be connected between the positive terminal on the start battery to the other bank.
However, it would be more effective to have the alternator charge the house bank (assuming those other batteries are a house bank), and then have the combiner/echo charger pass the charging current to the start battery. There have been a number of threads on the use of combiners and echo chargers. You can also learn more from the manufacturers' website. Blue Sea is probably the main manufacturer of combiners and the Echo Charger is, I believe, a Xantrex product.

John

This is the simplest, least expensive and most efficient means to accomplish what you want. We have used this method for 25 years on two boats while doing extensive cruising. It works, you don't have to remember to change switches, and you don't have a lot of potential points of failure. We use the Xantrex Echo Charger, the ONLY Xantrex product I will use. Chuck

[IRG]

Avoid diode-based battery isolators LIKE THE PLAGUE, they are the devil's own work. They drop your charge voltage by 0.6 which is critical to getting a full charge. It's possible to boost some alternator outputs to compensate but you have to know what you're doing. I endorse the relay-based option mentioned above.

[a64pilot]

What's wrong with Both on the battery switch?
Works for me and doesn't cost anything


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[kas_1611]

Look into the Sterling Power range of charging gizmos. I use a ProSplitR to divide the alternator charge between my Starter, House and Thruster batteries with zero volt drop (excluding any drop over the cable run). You can also use their Alternator to Battery charger (A2B) and Battery to Battery charger (B2B) to increase both the scope and efficiency of the charging circuit.

Don't forget fuses and wire sizes plus have a blocking diode/charge controller between your solar panels and batteries. No need to add a 1/2/Both/Off switch as all 3 of my batteries are independantly wired and not interconnected in any way.

Other similar systems are available but I found Sterling to be the simplest to understand and use plus good customer service.

Keiron

[Starblossom]

Look at the Sterling alternator to battery charger
Alternator to device- senses requirements of both banks
device output to house bank - approx 50 minutes per hour
device- output to starter battery- approx 10 minutes per hour
adjustable for battery type and size
trouble free and easy to install
Solved my problem of the alternator being sensed by the starter instead of the house bank.
Good Luck

[Martkimwat]

I have Merlin products Smart Bank Lite installed on my Parker 27, works like a charm. When the engine starts charging, it initially charges up the start battery so that it's ready for the next start, as soon as the Smart Bank senses the start battery is full, it closes a relay and starts charging the house battery as well. It also works in reverse. I have my solar panels feeding the house batteries , as soon as they are full it again closes the relay and charges the start battery as well. It's simple, inexpensive and works. I don't have a 1-2-both switch, just two simple red plastic key type switches, again simple, efficient and unambiguous. I put them both on when I'm on the boat and the Smart Bank takes care of everything. If I need to supplement either battery with the other battery, there is a momentary action switch which I can press which will connect both batteries together for a (programmable) amount of time which will close the relay for additional power to either start the engine or make an emergency call for example. I have isolator type battery terminals so that I can isolate either battery bank and still use the momentary pairing switch if either of the banks develop a dead short. I have a simple Nasa Marine battery monitor for the House bank as well as a simple two position battery voltage meter for both banks.

[Training Wheels]

+1 on the combiner. Our alternator is wired directly to our house bank, with a combiner to the starting battery. No matter what you do with the battery switches, there is zero chance of messing up your alternator.

[skipmac]

Originally Posted by Lepke

The easiest way is install a multi battery isolator. See picture. Pictured is for 3 batteries. One terminal goes to the alternator (in place of the wire going to the single battery) and the other three to batteries. Your solar charge controller may need to be isolated, too.
If you know what you're doing, you can make your own with diodes and a heat sink.
Another way is manually with switches heavy enough for charging amp flow.

Using a diode isolator is quick and simple but standard silicon diodes drop 0.7V so you're losing some of your charging voltage. A Schottky diode is lower but still 0.3V. Either way you will reduce the rate of charge. Better to go with one of the battery combiner options.

[skipmac]

Originally Posted by a64pilot

What's wrong with Both on the battery switch?
Works for me and doesn't cost anything

The problem with using the Both position on a battery switch to combine house and start batteries for charging and daily use is some people forget.

Forget to switch to Both when charging and end up not charging one bank or the other. Worse, forget to switch away from Both at anchor and you discharge all the batteries so you have no way to crank the engine.

It only takes once to leave you stranded in the middle of nowhere.

You can guess how I know this.

I like the idiot proof, tired in the middle of the night proof, guest on board proof automatic battery combiner system.

[skipmac]

Originally Posted by Training Wheels

+1 on the combiner. Our alternator is wired directly to our house bank, with a combiner to the starting battery. No matter what you do with the battery switches, there is zero chance of messing up your alternator.

My preferred setup.