Author Topic: Battery settings when away from your boat.....  (Read 2981 times)

Brett

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Battery settings when away from your boat.....
« on: April 12, 2015, 06:25:51 PM »
Hello all,  we have been experimenting with different switch setups for our batteries when we leave the boat for a month or so.  I was initially told it was a good idea to leave the start battery isolated but every time I have done that when we get back it is low/dead.  It is a deep cycle group 31 marine starting battery.  I am guessing that is because it is isolated from shore/solar charging and the bilge pump may be running a little while we are gone.  Also probably some of the self discharge involved also.  When we return, realize it won't start the diesel and I switch the barrel switch back to "all" after five minutes or so it is charged enough to start the diesel and I can switch back to just the start battery and fire the diesel up.  "All" setting ties our ten house batteries in (Trojan T105's).  House batteries are <6months old, start battery Cells are always full of water and battery is <10 months old and has been tested for bad cells.  I am curious what others do? Leave all batteries connected via the barrel switch or other method to keep start battery charge level up then switch it back before firing up the diesel or am I missing something?

Peter Roach

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Re: Battery settings when away from your boat.....
« Reply #1 on: April 13, 2015, 08:10:08 AM »
I have two banks of batteries on Grace. Each one is about 500 Amp hours. when I leave the boat I leave one of these battery banks active. It is charged by the solar panels and is responsible for the bilge pump. it sounds like you have a vampire draw on your start battery. I would try to find a vampire draw and remove it from the start battery and move it to house battery.if you want to keep a separate start battery. I've never seen the need for only a start battery that is why I have to house banks.

Warning this topic will get you a lot of different ways to wire a boat. It seems to be only limited by your imagination.
I tried having a bad day once but I did not like it

Brett

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Re: Battery settings when away from your boat.....
« Reply #2 on: April 13, 2015, 09:07:52 AM »
the only draw on the start battery "should" be the bilge pump.....but the house banks don't have enough cranking power to start the diesel on their own it seems even when on a full float charge.....granted I'm no battery expert ....our house battery set up is ten paired 6V flooded lead acid batteries with 225ah each which would seem to me on the surface to be sufficient but it just doesn't get the job done.....perhaps it is a matter of cranking amperage as opposed to amp hours ?  both house banks in conjunction with  the start battery will start the diesel though...this whole setup was supposed to be done in conformity with Nigel Calder's recommendations in his "Boatowner's Mechanical and Electrical Manual".....but I guess there's always room for error....are your house batteries 6V or 12V ?

Soggy Paws

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Re: Battery settings when away from your boat.....
« Reply #3 on: April 13, 2015, 06:53:41 PM »
Brett,

You are probably right that with no charging source to your start battery over a month of bilge pump use the start battery may not be able to start your engine.  Your golf cart house bank should easily start your engine, though.  Check all your connections and switches for heat from the batteries to the starter.  There is probably something amiss there. 

You are right that the start battery should be  isolated from the house bank at all times except in an emergency so that you will not lose both battery sets in the case of a shorted cell or some other battery drain issue.  We use an inexpensive automotive 650 CCA 12v battery to start our Perkins 4154.  It is has plenty of cranking amps and lasts about 3-4 years if kept charged. 

The house bank is your back up in case the start battery fails.  The reason you want all your house batteries in one bank is that your charging sources can charge a large bank more efficiently than a bank half that size, ie two banks.  So it will take you more charging time to charge two banks half the size of one.  If you use your engine or a generator to charge your batteries, this makes considerable  difference in charging time.  The old way was to have two isolated house banks and rotate days of use. 

There is an inexpensive simple way to isolate the two battery sets and charge both at the same time involving a thermal circuit breaker and Shotsky diode.  You will never again have to fiddle with your battery selector switch to charge batteries except in an emergency to start the engine.  You can read more about this on our website under Workshop/Electrical.  This will always get you home in case of either bank's failure.  Be sure to use big fuses within 18" of all your battery banks to prevent a fire in case of a shorted cell.

Dave
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Brett

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Re: Battery settings when away from your boat.....
« Reply #4 on: April 13, 2015, 10:29:08 PM »
Dave,
We are kinda stuck with the setup we have due to space limitations, we have two banks, one of six and one of four.  The house batteries definitely won't start our diesel even when fully charged, I've tried that several times with the old and new batteries. They will top off the starting battery and then it will start the diesel.  I can't find any heat in the connections or switches so far.  We do have large fuses close to battery banks though.  I'm thinking I'll keep the batteries switched together so the charging apparatus can keep the starting battery full then switch just to starting battery when ready to fire up the diesel.

Our last starting battery lasted about five years based on dates we got from Jack. 

I'll research the thermal breaker and diode option....maybe Jack installed those and I just haven't run across them yet. He said he went strictly by Calder's methods when rewiring the boat. 

Thanks,

Soggy Paws

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Re: Battery settings when away from your boat.....
« Reply #5 on: April 14, 2015, 01:30:31 AM »
Hi Brett,

If you have 10 ea T105 golf cart batteries, they are wired together in one bank, and they are in reasonably good condition/charge, they should have no problem starting your diesel, especially since you have proved the starter/regulator are fine by starting it with the much smaller start battery.

If you have any doubts you could do a rough check of your battery condition by watching a voltmeter attached to the battery bank while you try to start the engine.  The voltage should not drop below about 10 volts.  Details on this in Calder's book.   You could also check the specific gravity of all the cells in all the batteries after they have been fully charged and allowed to rest for at least an hour.  They all should read about 1.260 or better.  Any below about 1.230 means that battery needs equalizing.  You could take that battery and one other out of the system and try again, but in order not to be able to start the engine you would probably need at least to have 8 of those batteries very weak.

Assuming the starter and batteries are fine, the problem must be in the wiring or a connection or switch between the two.  There are several ways to trouble shoot that.  One quick way is feeling with your fingers along the entire wiring run between the batteries and starter for hot spots immediately after trying to start the engine.  To be more precise you can look for a significant voltage drop along the connections with a volt meter as you try to start the engine.   But I would start by taking all your connections apart, clean them with sand paper, coat them with a bit of Vaseline and put them back together tightly.  Look for any green corrosion or loose fittings.

I am having a similar problem and think it is one of my Hella disconnect switches.  My engine won't start with the starter battery but will start with the big house bank tied in with it.  I have taken it apart and the contacts are quite pitted so I have a new one to install.

The problem with charging both the house and start batteries together is that the typical charging source can sense only from one battery set, and that sense wire is normally on the house bank.  So if your house batteries need charging, by switching to Both, you properly charge the house bank but overcharge the much smaller starter battery.  That is why the diode and TCB system is useful.  All your charging sources are connected only to the house bank, and the starter battery  is isolated from any loads except the starter.  It is trickle charged through the diode and TCB when ever the house bank voltage is greater than .5v above that of the start battery.  Inexpensive, simple and effective. 

Jack was aware of this setup and you could email him to find out what he has done.

Let us know when you find the problem.

Dave


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Brett

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Re: Battery settings when away from your boat.....
« Reply #6 on: April 16, 2015, 09:14:29 AM »
I spoke to Trojan.  They say two T-105's should be enough to start the diesel.  So, there is some serious trouble shooting to be done.  When we tried to start using just the house banks the voltage on the display dropped from 13.5 to 12.9 then 12.6 pretty quickly so there is some issue.  I'm not sure  why new batteries would do that.  The ten batteries are in two banks.  I think I am just having trouble believing it is the wiring since once the start battery tops off after the isolation switch being turned to "all" it runs up and starts the diesel easily.  If the diesel is run regularly there aren't any issues either.   If there was a wiring problem wouldn't that attempt to top off the start battery fail also ?  I can't seem to get a response from Jack about the Shottky diodes so when I get back I will have to look for them and test them or install them.
It has been really stressful and financially draining the last 16 months getting things up to speed on KH.  At times it has felt like we aren't going to make it before we run out of money to fund the dream. Or once we get out full time the persistent issues will end the cruise prematurely.

Matthew Balch

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Re: Battery settings when away from your boat.....
« Reply #7 on: April 17, 2015, 07:05:43 AM »
Brett,  I had a similar issue a couple years ago.  It was very frustrating, and I even removed the starter and had it tested at a shop.  I ended up inspecting wires and cleaning every connection in the starter and battery circuits, like Dave mentioned, and that surely was the best thing to do.  Pay particular attention to the negative side which is sometimes overlooked.  I finally traced the problem down to the battery switch which appeared fine, but tested out with high resistance.  One last thought: shouldn't you move the bilge pump wiring over from the start battery to the house banks?  That would remove some of the draw-down on your start battery.  Matthew

Brett

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Re: Battery settings when away from your boat.....
« Reply #8 on: April 17, 2015, 08:50:49 AM »
Brett,  I had a similar issue a couple years ago.  It was very frustrating, and I even removed the starter and had it tested at a shop.  I ended up inspecting wires and cleaning every connection in the starter and battery circuits, like Dave mentioned, and that surely was the best thing to do.  Pay particular attention to the negative side which is sometimes overlooked.  I finally traced the problem down to the battery switch which appeared fine, but tested out with high resistance.  One last thought: shouldn't you move the bilge pump wiring over from the start battery to the house banks?  That would remove some of the draw-down on your start battery.  Matthew

I think I have a long weekend of full wiring and switch inspection in my near future.  Ugh.....If I recall correctlly, our secondary pump is wired to our house bank.