I really must ask ..??????

[Maine Sail]

In recent weeks the topic of folks frying alternators has been quite common place. I just can't understand how or why folks feel the need to switch from their start bank to the house constantly or even think that they actually need to use a dedicated start battery to actually start the motor!

For a long time I have wondered why folks insist on using their starting battery for starting their engine then they switch back to the house bank? There is ABSOLUTELY NO NEED to do this, with a good house bank of deep cycles, and only serves to increase the odds that you will inadvertently forget to switch back to "house" or hit the "off" position while switching and FRY your alternator diodes as quite a few have already done this season on this and other forums.

I like to think of my starting battery as a "EMERGENCY battery" instead of a "starting battery" and use my house bank for everything including starting even after discharging it on the rare occasion to 40% of total capacity!

The idea/myth that a deep cycle battery does not have enough MCA's or even CCA's to start an aux sailboat engine is just that a total myth.

ANY sufficiently sized house bank has ample capacity, deep cycle or not, to start a teeny tiny marine aux engine!!!!

So why do folks switch back and forth and back and forth????? You DON'T need a starting battery to start a sailboat aux engine and if you do your house bank, terminations or wiring are TOAST!

I do exercise my starting battery once every two weeks or so when I vacuum the interior of my boat with the inverter and my Royal Dirt Devil sucking amp hours out. I then let my solar panel and ACR relay charge it back up for an emergency.

As an example my 44hp 4 cylinder Westerbeke requires 160 cranking amps. Even the smallest PERSONAL WATER CRAFT battery listed in the West Marine catalog puts out 375 marine cranking amps! MCA is rated for a 30 seconds draw at 32 degrees F. CCA or cold cranking amps is 30 seconds at 0f.



Even the SMALLEST group 24 DEEP CYCLE battery will produce 625 MCA's...!!!! Just ONE group 24 deep cycle battery will put out nearly 4 times what my 44hp four cylinder engine requires for cranking amps!!! Yes, even two 6V deep cycles combined for 12V (GC-2 size) will do well over 500 cranking amps.

My batt switch NEVER sees position 2/emergency/start except when exercising my start battery every other week or so. The rest of the time it is in position #1 or HOUSE..??

You DO NOT need a dedicated "cranking" battery to start a sailboat AUX engine unless you have a 450hp Detroit Diesel and a 70+ footer..



Just thinking out loud.....

[Stillraining]

Your mode of thinking about this has always been how Iv done it....Iv just keep quite about it so I wasent presumed to be ignorant or something...

Glad to hear Im OK after all...and I will be sure my wife hears that too..

[denby]

Good thinking out loud hal. I all ways put the selector switch to all unless I'm at anchor then I select one battery.

[Maine Sail]

Originally Posted by denby

I all ways put the selector switch to all unless I'm at anchor then I select one battery.

Den,

I hope you only utilize the ALL mode when the motor is actively charging? I am guessing, as most boats do, you have two different types of batteries or size banks in your boat that were likely purchased at different times? If you do and combine them when not charging this is not a good idea...

Getting in the habit of using "ALL" can be dangerous as it can potentially leave you with "ALL" batteries dead!!

Remember ALL can = ALL batteries dead

[sailingdog]

I use a BlueSea Dual Circuit Plus battery switch. The boat's main DC panel runs off the house bank, the engine starts off the starter bank. An ACR battery combiner connects the two banks if either bank has a charging source. IN an emergency, I could combine the banks if necessary...but I could also hand start the 20 HP outboard.

[brak]

I have the same system as sailingdog's. I always wondered about these two-bank selector switch arrangements, and when I finally found the BlueSea dual circuit switch - it was like the light turned on, here it is - that's the way to do it.

That said, it does mean I have a separate starting battery - why not, it does not cost much, everything gets "magically" charged and used, and I don't have to think twice about the switch.

Perhaps one useful aspect of this system is that if, inadvertently, something draws down one bank, the other will still be available.

[Pamlicotraveler]

Halekai...You hit on something that I have been trying to figure out with our boat. I have two banks and I always leave it on BOTH (or all). I thought that was what I was supposed to do. Each bank is 2 Group 27 AGMs. I don't have anything that keeps the batteries from going dead (that I am aware of) so I just keep an eye on the voltage. Should we have an isolator or something to prevent the full discharge of one of the batteries? I don't think we have it.

My back up plan has been to use the little West Marine emergency battery if we discharged all of the batteries by mistake. I charge it regularly.


The other thing I could do in a pinch is bring the bow thruster battery back to the engine area, but that would be a pain.

So how should we handle it? I used to think in terms of house and start batteries on our boats, but I thought that now the idea was to discharge and charge all batteries in the banks at the same time and just watch the voltage.

[therapy23]

I have often wondered about this standard setup myself.

I can see having two banks in case a DUH moment happens and one is killed (could be pretty hard to do) but why that starting only battery?

It seems to me that two or three house batteries, mostly discharged, could start an engine. Am I wrong?

[nk235]

I actually have a question in regards to this. The boat I just bought, a 1983 Morgan 323 has 3 group 27 gel cells for the house bank and 1 group 27 gel cell for a starter/emergency battery. 90% of the time I just start the 20hp Yanmar 3GMD with the house bank because I figure its best to let that one charge up.

A problem I have been having is that after spending a weekend on the boat running the refridgeration, fans, stereo, etc. (Never let the house bank get below 12.15 volts though) I cannot start the engine up off the house bank without some trouble. It starts up absolutely fine, and I even increase the rpms to about 1100 but as the charging volts increase, the warning light and horn sounds on the Yanmar panel and I hear a squeaking sound from what is probably the alternator belt. I shut down the motor, restart it and let it run on the sole starter battery and then after about 5 mins I shut it down restart it on the house bank, bring the rpms up even higher temporarily and then once it shows that is charging at 14.10 volts I know I am fine and bring the rpms back down to around 1100 again. I have a 20hp Yanmar 3GMD with an 80 amp Balmar Alternator. My guess is that the alternator starts putting too much of a strain on the engine as it trys to charge the 3 low gel cell batteries? I know once I start the engine and I look at the volt meter, the voltage charge goes up slowy from 12.8 all the way up to 14.10. I usually get the alarm and squeeking sound after about 15 seconds and when it is around 13.40 volts.

Anyway sorry for a long post but if someone more knowledgeable about this can confirm that is in fact what is happeneing or if it is somthing else.

Thanks

[sailingdog]

Nk235-

The load is probably as you guessed, caused by the alternator trying to fill up the three discharged gel batteries.