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Old 10-05-2014, 18:15   #1
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Opennion and or Advice (Battery's)

Ok the solar system is now in stalled and working fine (2- 100 watt panels)...now during the test we found that with the refer/inst/radio and auto pilot the system could not keep up with the draw down. My existing Battery's consist of 3 AGM Deep Cyc group 31's for which 2 are dedicated to house and one to start. It seems the problem is not enough storage capasity...Now here is the problem i am facing...(1.) add two additional batteries to take on additional storage..(2). Leave as is and run motor once in the morning and once at night to recharge. The boat is a CS 30 and consums 1/2 gal an hr at 1500 rpms. The mission is too go south in Nov and spend the winter in around the Keys with the intent to stay away from marina's...Ok so here is the question...more batteries or stay as is and suck up the fuel ?
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Old 10-05-2014, 18:27   #2
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Re: Opennion and or Advice (Battery's)

It all depends on what your ENERGY BUDGET is. Have you done one? Otherwise, we can't answer. For example: Do you have a fridge?
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Old 10-05-2014, 18:27   #3
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Re: Opennion and or Advice (Battery's)

It is impossible to say what to do without knowing how many amphours you consume in an average day. You may be consuming 100 amphours in a day. 200 watts of solar panels will typically put out 70 amp hours of power in a sunny day. More batteries isn't going to help. You need more solar panel watts, at least 300 watts, probably more.

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Old 10-05-2014, 18:30   #4
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Re: Opennion and or Advice (Battery's)

More batteries. AGM's will fit in all kinds of places.
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Old 10-05-2014, 18:45   #5
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Re: Opennion and or Advice (Battery's)

I'm thinking you have about 315AHrs in your two banks. And 200W of solar.

If you give some numbers on your fridge, radio, auto pilot, etc then someone here would help.

Voltage, Amps, watts, daily use time, whatever you got.
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Old 10-05-2014, 18:47   #6
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Re: Opennion and or Advice (Battery's)

As my wife is fond of saying: "yeah, BUT..."...

The AGMs themselves have their own issues: since they accept so much amperage from a charging source, the alternator must be able to deal with them. A little research on AGMs will show that, and the OP must know what he is dealing with with his entire electrical system.

We simply don't know if he does, yet...

AGM Battery Issues (from Maine Sail)
AGM Batteries - Making The Choice - SailboatOwners.com
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Old 10-05-2014, 20:04   #7
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Re: Opennion and or Advice (Battery's)

If you think another battery would solve your problems, just parallel the start battery with the house bank. If the batteries do go dead you shouldn't need more than an hour or two of sunlight to get enough power to start the engine.

You didn't mention the test conditions--sunny vs cloudy makes a big difference. A 30 ft boat with decent refrigeration and led lighting should make do on 200 watts of solar in the summer, but you might need another panel for the winter.
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Old 10-05-2014, 20:22   #8
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Re: Opennion and or Advice (Battery's)

A lot to consider, but 200w should do it! I have 270w and almost always float unless it is dark clouds all day. To really be self sufficient permanently you need more storage and your solar is right on the edge but will probably work if you "watch your watts!" In your case consumption is the key as your storage is limited. Like he said, flip on all the batts and see what happens!
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Old 10-05-2014, 20:24   #9
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Re: Opennion and or Advice (Battery's)

Batteries don't make energy, they store energy. If your batteries are going down in voltage during the day more batteries isn't the answer. Reduce the power load or increase the solar are the options. In the mean time you can run the engine daily but AGMs (or flooded for that matter) are not optimized for engine charging. Get more solar if you can afford and have space. AGMs have very limited life if they are constantly partially discharged. At least once a week they need several hours of engine charging to top them up. Try to do it while motoring somewhere to reduce engine wear and tear.

Once you have enough solar then more batteries will get you through cloudy days better. And it's not 1 for 1. More batteries in parallel makes the existing batteries more efficient.
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Old 10-05-2014, 20:34   #10
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Re: Opennion and or Advice (Battery's)

[QUOTE=donradcliffe;1538173]If you think another battery would solve your problems, just parallel the start battery with the house bank. If the batteries do go dead you shouldn't need more than an hour or two of sunlight to get enough power to start the engine



I'm not sure how you determine how dead is "dead". 1 or 2 hours of how much sun? You might want to kick back and have a few beers. Maybe manana.
There is really not much to worry about if all you want to do is start the engine. Several dead 12v batteries in series will start the engine if you want to re-wire them. Just make sure you don't have anything delicate turned on.
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Old 10-05-2014, 20:56   #11
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Re: Opennion and or Advice (Battery's)

450 watts of solar, and 800 amp hours of house batteries (the 25% rule of average power consumption to storage, or the batteries won't last long). This gives you matched average usage to consumption based on your general description. You also have reserve power when needed. You'll still have to top up with engine on a heavy use day, or a few days of clouds and/or rain. All my clients with boats as yours have this setup and no complaints. We have the same on a P-45 catamaran, with fridge and a host of other electronis toys (flatscreen, dvd, computer, etc.). You still have to manage usage, or be prepared to run the engine. More than this and your boat may start looking like a NASA science project. If you can afford an Outback Flex 60 controller, you'll almost be able to ignore the system, and lots of power options and data to play with.
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Old 11-05-2014, 04:10   #12
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Re: Opennion and or Advice (Battery's)

Awww sorry I forgot to mention that the test day was very sunny and bright...the refer is a Sea Frost, What I think I will do is continue to run test this summer up till the time to go south and then make the decession to either add or stay as is based on what i find over the next 6 months,,
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Old 15-05-2014, 06:04   #13
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Re: Opennion and or Advice (Battery's)

U consume therefore U must create.

There is no free lunch.
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Old 15-05-2014, 06:29   #14
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Re: Opennion and or Advice (Battery's)

You are using more electricity than you are generating. More batteries isn't going to help at all. It's like thinking... My watermaker produces 4 gallons of water a day, but we drink 6 gallons of water a day, so I must need a bigger water tank. You do see the problem with that logic, don't you?

Stu gave you the answer in the very first response. If you want to do this right, so that you have enough energy available without spending a lot of money on more than you need, then the very first thing you need to do is come up with an ENERGY BUDGET. You need to know--at least to a fair approximation--how much energy you are using on an average day. Without that, everything else is just a wild-ass guess.

Good luck.
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Old 19-05-2014, 17:47   #15
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Re: Opennion and or Advice (Battery's)

a foot note to my little problem...I was talking to a very experience sailor and we were discussing my battery arrangements...He told me he never uses his start battery...he starts his motor on his house batteries and therefore he keeps his switch on house....I ask why (being the dummy I am) he said he uses his start battery only as a back up and the charger keeps all of them up..he said you never know when that situation come up and u need that start and if the switch is on both all the time there is a possibility you could loose all....and then have nothing to start with....so again i bow to all you learned men of the sea does this make sense....
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