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Old 06-01-2012
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Battery Charging Assistance

Hello all,

I have a question concerning the best way to charge/maintain batteries. I recently purchased a 1998 Catalina 28, which has Battery 1 as the house battery (deep cycle) and battery 2 as the starting battery. When reading the material that came with the boat (i.e. Catalina manual), it says to leave the selector switch on Combine pretty much all the time...when charging, and when starting if both batteries are full or low. However, I have also heard to switch between batteries...moving the selector to a certain battery (2 maybe?) for starting, and once started to move to combine to charge both batteries.

What is the best solution to preserve/maintain battery charge? Keeping on combine all the time (starting, charging, using DC power at night) or switching back and forth between 1, 2, or combine? Both batteries seem to maintain a full charge and appear to be in good shape.

Thanks,
Brian
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Old 06-01-2012
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Re: Battery Charging Assistance

We need more information.

First, while you have 2 battery banks, can you go over the individual structure of each bank? Is it simply 2 individual batteries that are the same (ie one group 27 that is starting/engine bank and one that is house bank?). Or is it where you have a single battery for starting/engine bank and a much larger array for house bank (ie multiple golf cart batteries set in series/parallel).

Second, it would be good to know how your boat is kept when it is not in use? Is it on shorepower? Are you on a mooring with alternative energy for top-up (solar)?

Lastly, it would be good to know how you use the boat. Do you daysail? Do you weekend? Do you go extended cruising?


I am assuming you are in a marina with shorepower and your boat has a good 3 or 4 stage charger. I assume also that you have a very simple 2 bank system...with bank 1 being a single battery for engine starting (marine starting, not deep cycle group 27), and bank 2 being your house battery (marine deep cycle, group 27). I am assuming also, that you are a weekender...so you come to the boat on Friday afternoons, make ready....and spend the weekend sailing about away from shorepower, using the engine alternator to top off the bank when it gets low. Given those assumptions, here is how I would run my battery setup.

While the boat is on shorepower at the marina, I would leave the bank in "All" mode (combined), ensuring that both batteries are kept fully topped up by the charger. When I arrive at the boat and make ready to start the engine, I would unplug from shorepower and check the voltage available and make sure it is above/around 13v...then start the boat up with the bank combined. Since you're going to have the alternator take over for the shorepower, it doesn't really matter that you're starting with both banks when they're both fully topped up. If your voltage reads significantly below 13 volts, then something is wrong with your charger, your wiring, or your batteries and your weekend is likely shot because you'll spend the rest of it fixing the issue

Once you've navigated the marina, gotten out of the channel and are getting ready to sail and have turned the key to cut off the engine, here is where I would make my first change. I would take the selector and set it to bank 2 (house) only. I turn off my engine bank while sailing to isolate it so that I dont accidentally run it down using my electronic toys when underway (ie plotter, fridge, radar, etc). You'd be surprised how quickly all those things gobble up amps...especially fridge!

When you're ready to manuever to anchor (assuming you're not being all cool and sailing into anchorage), do a quick check of the voltage level of bank 2. If it is high enough that combining bank 1 + bank 2 wouldn't result in bank 1 (engine) discharging below the voltage required to start the engine...then go to "all"/combine in order to crank up the engine. If bank 2 is very low voltage (below 12.2 is my personal benchmark, then I would set the battery selector to bank 1 (engine) ONLY and ensure that bank 2 cannot leech the juice from bank 1. Then I would crank up the engine off bank 1 alone. Once the engine is started, I would shift the battery selector to "All" to combine the banks and allow the engine alternator to charge both batteries to full...especially the depleted house bank (from all your sailing).

When the hook is set (I have a windlass), batteries toppped off, and I've cut the engine off to enjoy my time at anchor, I would again return the battery to bank 2 (house). From then on, I do periodic checks of bank 2 (house) voltage to ensure I do not go below 12.2V because that represents 60% state of charge because my floooded deep cycles dont like getting deeply discharged. If I get close to that level, its time to run the generator (Honda EU2000), or to run the engine. If you have solar panels, then I would periodically adjust which bank the current flows into to make sure everything stays fully topped up. It takes hours and you may never get 100% SOC on cloudy days.

When you're ready to move off anchorage, I typically start off of bank 1 exclusively since it is likely still fully charged since you isolated it and used bank 2 for your anchorage activities. Once the engine cranks up off of bank 1, then I would combine batteries to allow the alternator to charge up both banks while you return to your marina slip. Assume no wind, so you're motoring back to the marina (isn't it always that way?) Dock your boat, kill the engine, plug in the shorepower and leave things combined to charge up to 100% while you're back at work dreaming about your next trip.

I'm sure this procedure will get criticized....and I'm open to the feedback because I'd love to know if I could do something better
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Last edited by night0wl; 06-01-2012 at 10:08 AM.
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Old 06-01-2012
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Re: Battery Charging Assistance

NightOwl,

Thanks for the extensive response...when I first started reading I wasn't sure I could provide all the requested information...but all of your assumptions were correct!

I think switching to the house battery while out makes good sense, and combinging when charging/plugged into shore power. A silly question: is the starting battery usually bank 1, or does it not matter, configuration wise, if it's 1 or 2? I will need to confirm, but I seem to recall the Catalina literature indicating bank 1 was house, bank 2 was starting. Didn't know if there was a general rule of thumb, and if I'm backward, would indicate re-wiring, etc, by a previous owner.

Thanks again for your post!

Brian
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Re: Battery Charging Assistance

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Originally Posted by nolesailor View Post
NightOwl,

Thanks for the extensive response...when I first started reading I wasn't sure I could provide all the requested information...but all of your assumptions were correct!

I think switching to the house battery while out makes good sense, and combinging when charging/plugged into shore power. A silly question: is the starting battery usually bank 1, or does it not matter, configuration wise, if it's 1 or 2? I will need to confirm, but I seem to recall the Catalina literature indicating bank 1 was house, bank 2 was starting. Didn't know if there was a general rule of thumb, and if I'm backward, would indicate re-wiring, etc, by a previous owner.

Thanks again for your post!

Brian
Doesn't matter...manufacturers wire boats differently. Actually, I should may dealers wire them differently since batteries are installed at dealer prep.

For Beneteau (my manuf), we dont even have the traditional dial based battery combiner. Instead, Beneteau currently uses a set of 3 twisting knobs. The first is a common negative, the second is engine bank, the second is house bank. Same concept though...various combinations of pegs in the vertical position activate and combine the battery banks.

But the concepts still hold. When charging, combine....when on shorepower, doesn't matter, and isolate your engine bank in order to be able to start the boat in case you run down your house bank too low!
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Re: Battery Charging Assistance

That all sounds good to me. I think the easiest way to sum things up is to say that the batteries should only be on All or Both when they are charging. Any other time combining dissimilar batteries means that one battery will end up charging the other. This just wears them both down over time. It's probably ok to start from all/both only if you're trying to save time or avoid forgetting to switch to all/both after the engine is running. But it's probably ideal to avoid combining batteries until after the engine is running.

That said, dealing with the switching is a big pain. A great upgrade is a battery combining relay, or an echo charger (I just installed a relay). Lots have been written about them here. Both serve to effectively combine the batteries automatically when the alternator is running. This means that if you can start off the house bank (you nearly always can) then you can avoid switching at all. Just switch to house motor, sail, motor - no switching. The starter battery is just there in-case you leave the lights on and kill the house.
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Re: Battery Charging Assistance

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Originally Posted by asdf38 View Post
That said, dealing with the switching is a big pain. A great upgrade is a battery combining relay, or an echo charger (I just installed a relay). Lots have been written about them here. Both serve to effectively combine the batteries automatically when the alternator is running. This means that if you can start off the house bank (you nearly always can) then you can avoid switching at all. Just switch to house motor, sail, motor - no switching. The starter battery is just there in-case you leave the lights on and kill the house.
I agree
And to add one thing - most often the shorepower charger is wired direct to the batteries. If this is true in your case the switch can be off when on shorepower. I would check the charger outputs to be sure.
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Old 06-02-2012
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Re: Battery Charging Assistance

Figure out what you have, most likely the alternator output goes to the C post of the 1-2-B switch. Then try these improvements:

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams [added 9/21/11]

[added 1/31/2012] This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com

You should never have to leave your switch ON when you're away from the boat. The charger should be able to go directly to the house bank for charging.
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Old 06-08-2012
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Re: Battery Charging Assistance

Thanks for the responses everyone...and Stu, thanks for posting those links, they were helpful in further explaining the 1/combine/2/off switch...

Thanks again,
Brian
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Old 06-08-2012
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Re: Battery Charging Assistance

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Originally Posted by mitiempo View Post
I agree
And to add one thing - most often the shorepower charger is wired direct to the batteries. If this is true in your case the switch can be off when on shorepower. I would check the charger outputs to be sure.
If you leave the switch off, won't the bilge pump then be disabled?
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Old 06-08-2012
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Re: Battery Charging Assistance

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Originally Posted by MarkSF View Post
If you leave the switch off, won't the bilge pump then be disabled?
The bilge pump should be wired direct to the battery through the appropriate fuse - not through the panel.
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