Stuff fails I agree, what I fail to see is how adding a switch and rewiring the starter adds reliability over the standard two bank selector switch with the starter connected to common?
House Bank - 2 separate or 1 parallel
- Thread starter scherzoja
- Start date
It does not add any "reliability", no one here said it did, it adds a dedicated & isolated start bank that won't drop out electronics if the house bank is too small to start the motor, at 50% SOC......
With large house banks the easiest solution is to use the house bank for everything & the 1/2/BOTH essentially becomes an ON/OFF or OFF/#1. All you need to do is occasionally test the start battery to ensure its operational.
On larger engines, thinck sport fishing boats in the 40-70' range, dedicated start batteries are the norm because their cranking current can still cause even large banks to drop voltage during starting. Once you get to a big enough engine they no longer use 12V batteries anyway, so you need a dedicated starting battery.
That's why you select 2 if voltage on 1 is too low.
Exactly what said.
Valid then, but we are talking sailboats here with single small engines.
I hate to be a curmudgeon, but adding an extra switch for anything should be validated. Coming from aerospace I learned every connection reduces reliability, every extra component reduces reliability, every switch increases complexity. My bet is most failures are going to be caused by a connection loosening up, either at connector crimps or from loose bolts, rather then from failed batteries. Next probable cause is a switch not being in the expected position. Murphy always wins.
I prefer to use both banks for everything, starting and power. If I ever think I may use too much power overnight, I'll hold the second bank in reserve for an AM start. I carry a Honda Gen in case of anything unforeseen, otherwise I would carry a portable Battery Pack with jumpers. If all else fails I wait for wind, if that fails I call for a jump.
Just my opinion, humble or otherwise.
Lots of batteries, as they age, compounded onto small or poor ships wiring, can lead to voltage sag during starting. This sag can drop electronics and some poorly engineered electronics can be damaged. This is why people add dedicated starting circuits to isolate electronics from voltage drop outs.
Not all boats have a sufficient enough house bank that can start without equipment drop out so many owners prefer to get the starting loads off the "C" post... The usual group 24 or 27 start battery may also drop electronics if it is not in healthy shape or when compounded onto poor ships wiring..
Me, I would rather see properly sized wiring, professionally terminated lugs and a healthy house bank that won't suffer from voltage sag, but this route is considerably more expensive than a simple ON/OFF and a jumper wire at eliminating voltage drops.
Battery failures are one of the most popular failings I deal with. A properly made battery lug crimp will outlast 5+ sets of batteries and battery switches are extremely reliable devices.. I have many boats with 30+ year old battery switches still going strong. There is FAR more on boats to worry about than an extra battery switch properly installed.
If an owner is having equipment drop out issues there are many solutions but adding a simple switch to create a dedicated start bank is often the most reasonable fix that retains all the safety, isolation and redundancy...
Well, I'm ready to make my parts list and go get this job done. Thanks to Maine, Stu and everyone else who helped me understand what I need to do to get this done right.
I just have one last question: WHen topping off the water in flooded batteries does it matter if I use seawater or can i just use water out of the tap?
Just joking (distilled)!!
Cheers!
I just have one last question: WHen topping off the water in flooded batteries does it matter if I use seawater or can i just use water out of the tap?
Just joking (distilled)!!
Cheers!
Finding a spot for an additional switch is usually a bigger problem, of course if one is not a DIY, it also is not necessarily cheap if you are paying for the tech time. Perhaps a compromise is something like a Blue Seas m-Series, Dual Circuit Plus™ Battery Switch 6011, replacing the original switch, it keeps the two circuits separate but adds combining feature. If one has the room and starting droop causes a problem the the added switch, can be a solution. To me why not just add another 1-2-Both-Off switch, then either battery can start and either battery can power the bus, with one more jumper. The 4 position switch is slightly more in cost and the same physical size. Operation is then more intuitive,one switch for dc power, one switch for starting. Heck, I added one just for my inverter power.
If one bank is dead the last thing you should do is combine it with a good bank. That is a bad practice that could (and has) left people without any means of starting as the house bank, if down a ways, tries to charge the start battery.
The dual circuit switch is best used on smaller boats with equal size banks like sportfishing boats. That is what it was designed for.
If one bank is dead switch to the other bank - don't combine.
Here's why for about the thousandth time:
AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
http://forums.catalina.sailboatowners.com/showthread.php?p=848465&highlight=darn agm
It would be good time spent to read Maine Sail's portion of this website, Forums, featured contributors tab upper left.