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Starting your engine on "dead" batteries.

Oct 26, 2010
1,065
Hunter 40.5 Beaufort, SC
Jumper cables that I kept on board for just such an occasion worked for me when the starter battery died. Jumped from the house bank.
I installed a "house bank - starter bank crossconnect" per Mainsails instructions that allows me to start the engine from the house bank if necessary or run the dc electrical system from the starter battery if the house battery dies. Comforting to know you can do this easily with just the flip of a couple switches.
 
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Tom J

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Sep 30, 2008
1,630
Catalina 310 Quincy, MA
Jumper cables that I kept on board for just such an occasion worked for me when the starter battery died. Jumped from the house bank.
Couldn't you select "Both" on the battery switch?
 

SG

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Feb 11, 2017
1,669
J/Boat J/160 Annapolis
If you have a small diesel engine, maybe this discussion has meaning. I had a friend years ago with an O'Day 30 and 2 cylinder diesel engine. It wouldn't start once and she asked if I'd try to start it with a hand crank. I couldn't even get the handle into a position where that would have been conceivable -- the configuration of the engine compartment, pulleys, and belt made it a joke (that's before I ever tried to release the compression valve).

I think for a small tractor, or a generator, maybe.

Who has really done this in the real world?
 
Jun 15, 2012
532
Hunter 50 AC Greenport, NY
Talking about cranks, check this out on Amazon!
High-Power Hand-Cranked Generator Household Portable Generator Disaster Emergency Camping Survival Outdoor Multifunction Tool
 
Dec 25, 2000
4,412
Hunter Passage 42 Shelter Bay, WA
Couldn't you select "Both" on the battery switch?
Since we've owned the boat, our battery switch has always been and remains on "Both". I suspect the isolation transformer was doing its job by keeping the house bank separate from the starter bank. To me the jumper cables were a simpler solution to the off chance that the starter battery decided to give up the ghost. I suppose there is an electrical; solution to adding this switch or that to activate the house bank, but that was eight years ago of those switches sitting idle waiting for the call to duty.

We purchased Belle-Vie, a 1991 P42 in 2002 with a starter battery of unknown age, but gave up the ghost in 2012. Hopefully, the Group 24 that we have should be good for another couple of years before it needs to be replaced. Meanwhile, time to go for a sail.
 
Nov 13, 2013
539
Catalina 34 Tacoma
Since we've owned the boat, our battery switch has always been and remains on "Both". I suspect the isolation transformer was doing its job by keeping the house bank separate from the starter bank.
An isolation transformer does not isolate the house bank from the start bank. Do you mean ACR (automatic charging relay)? Both usually means both banks. Your running everything off both banks until there's no juice left, then your stuck.
 

dLj

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Mar 23, 2017
1,125
Hunter 30 Snug Harbor, Lake Champlain
If you have a small diesel engine, maybe this discussion has meaning. I had a friend years ago with an O'Day 30 and 2 cylinder diesel engine. It wouldn't start once and she asked if I'd try to start it with a hand crank. I couldn't even get the handle into a position where that would have been conceivable -- the configuration of the engine compartment, pulleys, and belt made it a joke (that's before I ever tried to release the compression valve).

I think for a small tractor, or a generator, maybe.

Who has really done this in the real world?
The old volvo's (1, 2, 3 and 4 cylinder engines) used to be easy to hand crank in a sailboat. A sailboat I used to own I would start sometimes with the crank. My current Yanmar will also start by hand, but is difficult to do given the interior layout and the position of the decompression lever, but if I had to I could. Not as easily as my old volvo though, for sure. Fired of mine had a boat with an old Vetus that also hand cranked easily by hand. Those engines are hard to find now though.

dj
 
Jan 7, 2014
131
Beneteau 45F5 51551 Port Jefferson
I leave a set of Harbor Freight Jumper cables in the battery compartment so I can Jump off the house bank. And then there's always seatow or my little Honda EU2000 to charge the batteries if all else fails.
 

SG

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Feb 11, 2017
1,669
J/Boat J/160 Annapolis
I think that the wisdom of the approach to shifting the switch to "BOTH" (or interconnecting the batteries) is dependent on how bad the depletion of the first battery is compared to the juice in the second battery (bank). It also would be dependent on how quickly you try to start the engine.

I believe if you simply place the batteries on "both" (or interconnect the batteries), then you start basically i) start discharging the battery that has the lower amount of "juice in it" and sending it to one which is discharged; ii) when you then hit the charger, ii) then when you engage the starter, you are not getting the full benefit for the "good" battery (or batteries), you are only getting some it -- the good is being sapped by the bad.

Of course the magnitude of the effect is dependent on relative size of the discharged battery vs. the "better" battery bank. Then you have the non-linear power drain down curve of voltage vs. amps capacity.

I would suspect that the safer approach is i) turn-off the bad battery, ii) put a jumper cable on starter from the "good" battery to the engine, iii) start the engine, iv) turn-on the switch to the bad battery, and v) disconnect the jumper cable from the "good" battery. You need to always have a battery load on the alternator or you'll fry its diodes.

If the "bad" battery (or engine start battery) is just too low, but not shot, and the "Good" battery (or house bank) is strong and big enough, then simply lining them together usually works. I wouldn't leave them interconnected very long without the engine running, because you're only draining the good to the bad.
 
Jan 19, 2010
8,306
Hunter 26 Charleston
If you have a switch, you don't need to jump the dead battery with the good one. Just switch to the good bank, start your engine and alternator and motor off.
 
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capta

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Jun 4, 2009
3,753
Pearson 530 Admiralty Bay, Bequia SVG
I guess it wouldn't be a problem for dock queens, but why in the world would anybody else keep the battery switch on both at all times? That means they have only one battery bank and no back up at all. Anyone doing this should keep a few dimes around!
 
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Dec 25, 2000
4,412
Hunter Passage 42 Shelter Bay, WA
Your running everything off both banks until there's no juice left, then your stuck.
While the battery switch remains on both, that seems to have little effect on whether the house bank is down and the starter battery unaffected. Unsure how Hunter wired this complex electrical beast, but whatever they did, keeps the two separate. Maybe, as you say, the ACR keeps the two banks separate, assuming the boat has one. Either way, when the house bank draws down to 12.0v, starter bank remains at 12.6-7v. Been this way ever since we owned the boat. No plan to change the arrangement unless something breaks.

That means they have only one battery bank and no back up at all.
Not so in the case of our boat, Capta. I suspect that Hunter wired both house bank batteries to the battery switch one and two, and kept the starter battery a separate bank.
 

capta

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Jun 4, 2009
3,753
Pearson 530 Admiralty Bay, Bequia SVG
While the battery switch remains on both, that seems to have little effect on whether the house bank is down and the starter battery unaffected. Unsure how Hunter wired this complex electrical beast, but whatever they did, keeps the two separate. Maybe, as you say, the ACR keeps the two banks separate, assuming the boat has one. Either way, when the house bank draws down to 12.0v, starter bank remains at 12.6-7v. Been this way ever since we owned the boat. No plan to change the arrangement unless something breaks.



Not so in the case of our boat, Capta. I suspect that Hunter wired both house bank batteries to the battery switch one and two, and kept the starter battery a separate bank.
This would be most unusual and unorthodox. Normally, in a standard US wiring configuration, a boat (sail boat, motor boat or fishing boat, both pleasure and commercial, in my experience) has a house bank and an engine start bank, labeled #1 and #2. Combining the two (#1 and #2) as you say your system does gives one one larger bank, but no back up. I see no need for two house banks. If it was my boat I would just combine them into a larger bank (#1), make the start bank #2 and make sure I had a (several) proper charging system(s) to maintain both banks.
Just a question, if the starter bank is not wired into either house bank, how would you use the house bank if the starter bank was dead? Would you have to get out a set of jumper cables? That would mean when you hook up the jumpers to the dead battery, you were depleting the house bank, which would try to equalize with the dead bank, before you began to start the engine, a very inefficient way to do this. Normally one would just switch the selector switch and start the engine with the house bank. Then put the switch back to whatever it is normally set on and your batteries will charge up as needed.
 
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Nov 13, 2013
539
Catalina 34 Tacoma
Either way, when the house bank draws down to 12.0v, starter bank remains at 12.6-7v. Been this way ever since we owned the boat. No plan to change the arrangement unless something breaks.
If true, you should have no trouble starting on the start battery only. Move your switch to position #2 and see what happens.
 
May 1, 2011
1,359
Pearson 37 Lusby MD
I have two, two-battery house banks. They are connected by a 1-2-Both switch, and I normally leave that in the Both position for a single, large house bank. I have a separate start bank. There's an emergency parallel switch that allows me to connect the house to the starter circuit.
 

capta

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Jun 4, 2009
3,753
Pearson 530 Admiralty Bay, Bequia SVG
I have two, two-battery house banks. They are connected by a 1-2-Both switch, and I normally leave that in the Both position for a single, large house bank. I have a separate start bank. There's an emergency parallel switch that allows me to connect the house to the starter circuit.
Again, why would you want all that extra wiring and two house banks? What's the point if you keep the switch on both? I'm of the KISS school of marine systems, especially on the electrical side.
 
Dec 25, 2000
4,412
Hunter Passage 42 Shelter Bay, WA
I see no need for two house banks.
Our boat has one house bank with two batteries. No plan to make any changes as the one we have seems to work just fine and has over the years. I figure Hunter knew what they were doing when they designed the electrical system for this model. Our power panel has a selector switch that displays DC voltage for each battery; the two house and one starter. That gives me the voltage state of each one.
 
May 1, 2011
1,359
Pearson 37 Lusby MD
Again, why would you want all that extra wiring and two house banks? What's the point if you keep the switch on both? I'm of the KISS school of marine systems, especially on the electrical side.
Boat came that way. One house bank is under the v-berth for the windlass, and the other is under the quarter-berth.:beer: