Can I change the master battery switch from 1 or 2 to both while the engine is running? If one battery is very low, it shouldn't be in the circuit when starting. Or does the engine charge both batteries no matter which battery is selected?
Switching batteries while engine running
- Thread starter Terrel01
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The charging circuits from the shore power charger on a C-320 are direct wired to the batteries, bypassing the a-b switch. I've been told that the alternator is wired directly as well and that switching will not harm diode's. However, I have not verified that and I never switch while the engine is running.
Unless you are absolutely certain that a dealer/prior owner has not altered the factory wiring, you are must check out the wiring on your boat as you can't rely on what we post here about the original wiring.
Unless you are absolutely certain that a dealer/prior owner has not altered the factory wiring, you are must check out the wiring on your boat as you can't rely on what we post here about the original wiring.
Catalina's factory wiring is for the alternator to run through the Perkins 1/2/Both/Off switch at the battery panel. Thus the switch becomes a use and charge selection switch. That being said, the Perkins switch (double check that this is what you have) can be switched between 1-2-Both but never to off. That will ruin the diodes in the alternator. Look for printing directly on the switch that will tell you this. Mainesail has pointed out that this type of switch is called a "make before break".
Mainesail has put together a very extensive post on this here: http://forums.sbo.sailboatowners.com/showthread.php?t=137615
I followed Mainesail's advice and did a upgrade to my Catalina 310 (very similar to your boat in this manner). I blogged about it here: http://svsmitty.wordpress.com/2013/03/04/electrical-charging-system-upgrade-mostly-complete/
I went for a moderately high end fix based on our intended use of the boat (cruising the Caribbean). You could do this in a much cheaper manner. Mainesail has some good suggestions on his musings page.
Good luck and fair winds,
Jesse
Mainesail has put together a very extensive post on this here: http://forums.sbo.sailboatowners.com/showthread.php?t=137615
I followed Mainesail's advice and did a upgrade to my Catalina 310 (very similar to your boat in this manner). I blogged about it here: http://svsmitty.wordpress.com/2013/03/04/electrical-charging-system-upgrade-mostly-complete/
I went for a moderately high end fix based on our intended use of the boat (cruising the Caribbean). You could do this in a much cheaper manner. Mainesail has some good suggestions on his musings page.
Good luck and fair winds,
Jesse
You may change from one to two or both, but NEVER go through the OFF position...or you may damage your alternator/voltage regulator.
Unless you have other supporting equipment, the engine when running will only charge the selected battery. Avoid using "both" unless each battery is too weak to start the engine.
We use one battery to start the engine, and switch to the other battery when sailing to always maintain a fully charged battery to again start the engine
I've not found it necessary because I switch to both before starting the engine so both charge, then switch to 1 or 2 while sailing or moored. I've gone 3-4 days on the hook with a 4D battery without it's voltage getting too low to start on it's own. It really doesn't require that huge battery to start a 24 hp diesel.
Chris & Jesse are right. It all depends on how it's wired. Don't assume anything, go find out.
Here's some more reading material for you, includes the link previously provided.
Good luck. BTW, we're all "been there, done that" and have developed these ideas to help all skippers try to understand boat electrical systems.
Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html
Here's some more reading material for you, includes the link previously provided.
Good luck. BTW, we're all "been there, done that" and have developed these ideas to help all skippers try to understand boat electrical systems.
Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html
That is risky because as soon as you hit "both" the charge equalizes between the two. That could leave you without enough charge to start.
I totally agree with this. Switching to "both" (or all) just before starting is the way to go. The engine will draw the power from the strongest battery. Leave it on "both" while the engine is running. Just remember to switch to 1 or 2 after you kill the engine.
As for the original question, besides the fact that you shouldn't need to switch away from "both" while the engine is running, just make sure the dial doesn't go through "off" along the way.
This is incorrect (unless you have installed some kind of aftermarket relay). Once you switch to both/all the batteries are then in series and the charge is equalized between the two. If one battery is very low, you could leave yourself with two discharged batteries that can't start your engine.
Do some searching on this forum. MaineSail has pointed this out before.
This would only happen if one bank were completely dead and the other bank in marginal condition.
I generally suggest not to use "BOTH" in an emergency when the usually significantly larger house bank has been drawn so low that it can't crank the motor. If you are just leaving a dock there is no problem using BOTH, except that it can tend to mask a failing battery if BOTH is used regularly...
I actually did this once with my jump pack. Customer killed house bank then used BOTH. He left it on BOTH for a little while before he tried to crank and when he did the start battery did not have the ooomph left.
When I got to his boat with my jump pack it was late and I stupidly connected it to the dead house bank of AGM's sitting at 8V. By the time I got to the starter button the jump pack was toasted. Came back the next day and re-connected to the start battery, much smaller, and it fired right up...
Sorry, but this is wrong. First, when on "both" the batteries are in parallel, not in series. Second, for batteries in parallel to equalize takes hours, certainly a lot longer than the few seconds from setting the battery selector to "both" and pressing the ignition. Third, if one battery were completely dead it may now be damaged (one or more individual cells in the battery may have permanently reversed polarity) which would require replacement.
As cut and pasted from West Marine's "West Advisor":
Most single engine boats built in the last 40 years are equipped with two nearly identical (and undersized) marine batteries, used interchangeably for starting or house loads. Prior to starting the engine, the operator would turn the OFF-1-2-BOTH battery switch to the BOTH position to have both batteries’ full cranking power. With the engine now running, the switch would stay in the BOTH setting, and both batteries would be charged while powering to the day’s destination.
Once the engine was turned off (while anchored or under sail) the operator would (in theory) return the switch to the 1 or 2 position, and reserve a battery for starting. When it was time to crank the engine again, the battery switch would be turned to BOTH, or possibly to the reserve battery, and the engine would be started.
Once the engine was turned off (while anchored or under sail) the operator would (in theory) return the switch to the 1 or 2 position, and reserve a battery for starting. When it was time to crank the engine again, the battery switch would be turned to BOTH, or possibly to the reserve battery, and the engine would be started.
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