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#1011149 - 05/12/18 01:15 AM Re: Boat Deep Cycle Battery  
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Skywagon Offline
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Skywagon  Offline
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Bellaire Texas
Battery question....The battery isolator switch has position off, both, battery 1, battery 2. I have historically had 2 deep cycles in parallel. Is there any reason I couldn't mix them where 1 is starting and 1 is deep cycle? I run on both unless parking for a while then I switch to just one so I will always have a starting battery.

Last edited by Skywagon; 05/12/18 01:17 AM.

David
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#1011150 - 05/12/18 01:44 AM Re: Boat Deep Cycle Battery [Re: Skywagon]  
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terryofperry Offline
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Are you having trouble starting the motor on one deep cycle battery?

Terry


Terry
Perry,GA

#1011151 - 05/12/18 01:48 AM Re: Boat Deep Cycle Battery [Re: terryofperry]  
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No...I always start on both, but it will start on one with no issue


David
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#1011156 - 05/12/18 12:14 PM Re: Boat Deep Cycle Battery [Re: Skywagon]  
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I would want to be able to switch from one to the other so you KNOW you have some power left somewhere! My last boat was set up that way. As long as they both charge with engine running, I would want them set up that way for me. My motorhome uses (4) 6 volt deep cycle batteries for the coach power, and has (2) 12 regular batteries for the engine starting/run. Regular batteries are slightly better for starting. The generator starts off the coach batteries and I have had to use the switch to allow it to use the engine start batteries to start the generator. So there is merit in having the batteries on separate circuits.

#1011292 - 05/14/18 10:35 PM Re: Boat Deep Cycle Battery [Re: Skywagon]  
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elkroeger Offline
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There are experts with better answers than mine. So I'd defer to them. But as I understand it, normally you would operate off #1, for some period of time, then rotate occasionally to #2, so they get even use. They should be both set up to charge together, and depending on the charger, you may be able to put different types in. But I don't think people usually do that. I think you would need a charger that can do that, or separate chargers.

Just off the top of my head, I'd switch between them every week or so of actual use. And if anchored up for a period of significant battery drainage, you could use one as a house battery and save the other for starting only. I'd save the "both" setting for those times when something's screwed up, and now neither of them will start it. But I don't think it's really hurting anything to start on both.

Being that you're in tejas, you prolly should consider solar power. You'd have to do the math, of course, but in your typical usage, if you're draining your batteries beyond 50%, that's too much. Or if they're not getting topped up regularly (e.g. if its a hassle to run a power cord to the boat, etc.). Sounds like you probably have room for 100 - 200 watts on your deck (1- 2 panels). The really nice thing is that they'll keep your batteries topped up between uses, with no effort. That will extend your battery life, as well as minimize the potential for problems.

Get yourself a good setup with a proper charge controller. you can buy little 20 - 50W units around town, but spring for better panels with a good controller. These guys have a good little website to help you learn about it, and they're very friendly and helpful on the phone too. I bought some stuff from them for my camper van. Glorious. https://amsolar.com/

Last edited by elkroeger; 05/14/18 10:36 PM.

I'm a man, and I can change, if I have to, I guess.

Eric
#1011294 - 05/14/18 10:45 PM Re: Boat Deep Cycle Battery [Re: Skywagon]  
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elkroeger Offline
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They've re-done their website since I was last there. The educational stuff is tucked away in a not-so-obvious spot.

https://amsolar.com/diy-rv-solar-instructions/


I'm a man, and I can change, if I have to, I guess.

Eric
#1011301 - 05/14/18 11:59 PM Re: Boat Deep Cycle Battery [Re: elkroeger]  
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thanks Eric...the way the boat came set up from the factory is three batteries per engine with isolator switches for each engine. However for the number 1 engine charging system (built in from factory) also carries two deep cycle house batteries. So here is typical day....I start all engines on both, engaging all batteries per engine. I run on both as it does keep them all charged and get somewhat even charging. It will charge them all when alternator or AC is applied regardless of switch position. When we park for the night, we run the gen for house, cooling, heating, etc. Once it gets dark and its time to get quite, I switch to house bank only which is position 2 on engine 1 and I shut down the gen as a courtesy to others on the water. If I am tied up I just plug in ac which will run everything, So...that was a long explanation. What I was trying to think about is with the difference in CCA, AMP Hours, and discharge cycles would there be any reason I couldn't mix deep cycle and starting type on same switch. The boating forums are crazy with answers from, yes, no, burned my boat, set the marina on fire, been doing it that way for years, blah blah...you know like an oil thread.... So last weekend I did put starting battery and 2 deep cycle in parallel and we will see what happens over time. You think motorcycle batteries are expensive...go by some deep cycle AGM 27 series batteries...you can part with a Grover Cleveland in a flash.
.


David
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#1011315 - 05/15/18 07:13 AM Re: Boat Deep Cycle Battery [Re: Skywagon]  
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elkroeger Offline
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Yeah, $1200 doesn't seem so bad for a great big battery. But then you say "um, I need, uh... gulp. Six of them?" And that explains my interest in battery life.

The big difference (and it's been a long time since I've read up on it) between starting batteries, and deep cycles, is that the deep cycles have thicker plates than starting batteries. Those lead plates dissolve and precipitate with use and there's no way to control how the lead precipitates, so they resemble their original shape less and less. Also, the deeper you drain the battery, the more material that gets dissolved (I may have that backwards, but you get the idea anyway). You can charge it up, sure, but you're putting a lot more of the material back on there every time too, so they lose their shape faster. You can see how thin plates wouldn't last as long. Essentially they figured out that they can make a smaller, lighter, cheaper battery put out more amps *bang, right now* because it has more surface area per unit volume. But they're not much good for anything else. How long do you run that starter? 2, 3 seconds? See what I mean? A lot of juice in short bursts.

In a boat: You prolly got plenty of room, and they act as ballast anyway, so it's okay to put a great big son of a motherless goat in there. I read a book from the 1970s a while back about off grid living. The author was a talented amateur. He posed the question: how do you tell which battery is better, when they're priced differently and rated the same? Only thing he could think of was to simply weigh the thing. Buy the heavier battery because its got more lead in it.

Both types of batteries are rated in Amp-hours (how many amps can it put out for how many hours) and that measure really is the final word on how much work the battery can do. The Cold Cranking Amps is how they rate the battery in the freezer. Chill it down to some ridiculous temperature (which slows the chemical reaction and reduces the output). Then see how many amps it'll push. Again, *bang right now*. This stuff really comes into play in harsh winter climates. For your purposes, being down south, you can probably ignore CCA.

It sounds like you have a relatively large operation going on in your boat, which is above my pay scale. Surely the builder had a guy, and he knew what he was doing? But that's the basics on batteries anyway. You may be liable to run into issues with uneven charging and discharge. Maybe one would sulfate faster than the other? I don't really know. I would assume that the starting type battery would wear out first, but it's worth figuring out, so you don't have to part with more of those Grovers prematurely.


I'm a man, and I can change, if I have to, I guess.

Eric
#1011323 - 05/15/18 10:53 AM Re: Boat Deep Cycle Battery [Re: Skywagon]  
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terryofperry Offline
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Originally Posted by Skywagon
No...I always start on both, but it will start on one with no issue


I believe that to be your answer. If you are having issues starting a motor with a deep cycle battery then you would want an SLI battery to start the motor, if you are having no issues starting the motor on deep cycle batteries then it is better to have matching batteries, ie, both deep cycle or both SLI. I am fond of Sonnenschein (Prevailer), many other great choices out there also.

http://www2.exide.com/us/en/product...chnologies-network/gel-vrla-network.aspx

http://www.sonnenschein.org/Prevailer.htm

Terry


Terry
Perry,GA

#1011444 - 05/16/18 11:38 PM Re: Boat Deep Cycle Battery [Re: elkroeger]  
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elkroeger Offline
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So I will just point out (if anyone cares) that my description of how batteries work is incorrect. Sorry, been a long time since I thought about this stuff, and I was suffering from insomnia when I typed that.

Google knows all, grasshopper.


I'm a man, and I can change, if I have to, I guess.

Eric

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