Start battery dead?

[Maine Sail]

Originally Posted by svlamorocha

Maine Sail and Don

Now the follow-on question for you... How does OP make sure that the alternator is sensing voltage from the right battery when uncombined?

Or do you presume that ACR is working in auto mode, hence:

- in uncombined state means voltage in BOTH batteries is below 13.X volts, hence you do not care about which one is being sensed; and

- in combined state then both batteries have the same voltage, hence it does not matter which one you are sensing from?

Thanks in advance for the wisdom..

Any time one moves the alternator output from one bank to another care needs to be taken to also assure the volt sensing is moved along with it. If it is a typical stock alternator than simply moving the alternator B+ usually suffices as they are self sensed. If the boat has an external regulator or a stock alt with an external volt sense wire then the volt sensing wires, along with the B+, both need to go to the same bank.

[a64pilot]

Silly question,
Why not just run the alt to one bank, and combine the banks for charging with the battery selector switch?

[svlamorocha]

Originally Posted by Maine Sail

Any time one moves the alternator output from one bank to another care needs to be taken to also assure the volt sensing is moved along with it. If it is a typical stock alternator than simply moving the alternator B+ usually suffices as they are self sensed. If the boat has an external regulator or a stock alt with an external volt sense wire then the volt sensing wires, along with the B+, both need to go to the same bank.

Many thanks for that. I do appreciate your wisdom based on clear thinking AND looking at lots of boats.

Then the trick is how to easily move the voltage sense to the house bank in those boats (say Beneteaus with 80A Yanmar alternators and Moorings-modified wiring with various Bosch relays and cheap combiner relay driven by ignition) in which the sense wire comes from the engine panel but it is also used for something else (have not looked at one recently). I am yet to find a simple way to accomplish that. I will appreciate your wisdom.



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[Maine Sail]

Originally Posted by a64pilot

Silly question,
Why not just run the alt to one bank, and combine the banks for charging with the battery selector switch?

You can, it is essentially the same thing, with the exception of HEF (human error factor)...

I have had four customers this summer alone who forgot and left banks combined and killed every battery on the boat. I have also had three alternator rebuilds in the last 7 weeks due to switching errors and the resulting blown the alternator diodes from passing through OFF while charging. Running the alt direct to a bank, rather than the switch, fixes this. Using a combiner/VSR or other B2B devices fixes HEF....

A combiner/VSR does not forget to isolate the banks on discharge, or charge, like a human can...

Combiner/VSR's, Echo Chargers, Duo Chargers and B2B's (battery to battery chargers) are all charge management devices that simply automate the process of charging both banks, or even multiple banks, with no need to move switches or to make sticky notes in order to do so...

[a64pilot]

I ask as right now my alt is connected directly to the start bank, if I need or want to charge the house bank from the alt, I use the ALL selection of the battery selector, of course it means I need to select the house bank only if I think I may be running the bank low at night, but I think I may keep them combined making one 660 amp hour bank. I think my bank will last longer pulling 100+amp hours nightly out of a 660 amp hour bank as opposed to 440?
To me managing a battery bank is identical to managing fuel, in other words it's just not that hard to do, or hasn't been so far anyway

[Stu Jackson]

Originally Posted by svlamorocha

Maine Sail and Don

Now the follow-on question for you... How does OP make sure that the alternator is sensing voltage from the right battery when uncombined?

Or do you presume that ACR is working in auto mode, hence:

- in uncombined state means voltage in BOTH batteries is below 13.X volts, hence you do not care about which one is being sensed; and

- in combined state then both batteries have the same voltage, hence it does not matter which one you are sensing from?

Thanks in advance for the wisdom..

The battery sense wire should be connected to the house bank. It is CRITICAL to have the battery sense connected to the bank that the alternator is charging. Also be aware that long wires can induce voltage drop, so the battery sense lead should go to the battery bank, not to the back of the alternator - which is allowed in the MC-612 instruction manual - NOT a good idea. BTDT.

[Stu Jackson]

Originally Posted by mariner36bob

Swapped wires to feed house bank first, as instructed above, and after 1 hour motoring today the house bank charged up into mid 13's, combiner opened, start bank quickly topped off as well.

Electrically, it CLOSED.

[mariner36bob]

Yup. Closed.
And no cycling as before.

House charged over 13.2, relay closed, both charged into the mid-upper 13volts when I had to shut it down and go back to work.
Simple fix and much appreciated.


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[skipmac]

Originally Posted by a64pilot

To me managing a battery bank is identical to managing fuel, in other words it's just not that hard to do, or hasn't been so far anyway

In theory I agree and most of my previous boats were set up with two banks and a 1/2/Both switch to manage the charging. Never blew an alternator but did leave myself dead a couple of times when I forgot to switch from Both after a long day, late arrival or other distractions got to me.

Just love the foolproof setup with charging going to the house bank and charge to the start battery controlled by one of the automatic combiners. One less thing to deal with.

[svlamorocha]

Originally Posted by mariner36bob

Yup. Closed.
And no cycling as before.

House charged over 13.2, relay closed, both charged into the mid-upper 13volts when I had to shut it down and go back to work.
Simple fix and much appreciated.


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Now that the alternator output aka AO wire is connected to the house bank positive (or the house terminal of the conbiner): Are you sure that your alternator voltage sense wire was not left connected to the engine battery (or engine side of the combiner)?

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[mariner36bob]

Thank you, yes. 100% positive based on battery monitor showing voltage increasing on house bank, then combiner closes and monitor shows voltage on start bank rising also.

Also it was as simple as moving starter wire from start bank to house bank. I have an old school alternator which feeds through the starter and the same wire is sensing wire.

Alternator upgrade is on a long list of improvements to make so until then I think I'm good to go.

Thanks for checking up.


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[smac999]

Originally Posted by svlamorocha

Now that the alternator output aka AO wire is connected to the house bank positive (or the house terminal of the conbiner): Are you sure that your alternator voltage sense wire was not left connected to the engine battery (or engine side of the combiner)?

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a lot of alts don't even have a sense wire and just use the pos battery wire. so when you move one you move both.