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Old 23-06-2014, 15:53   #1
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Solar and AGM'S

Hi, I joined this forum almost a year ago this month then got involved in other things (shore bound-kinda). Anyway, I'm about to go out "on the hook" for a couple of weeks, and in the spring, I plan to head toward the gulf. I'm presently on a lake in Tennessee. I'm curious to know whether solar panels are adequate and safe to charge the batteries (I have 2 AGM's). I don't know anything about it really, I've just heard that AGM's require specially regulated current for charging. As a result I purchased a shore charger with a setting specifically for AGM's. Now that I am planning to be away from shore more often, I'm thinking more about Solar and how best to set up my house banks. I have no inboard, my vessel is a San Juan 7.7 and I've been living aboard it almost 15 years. I've done some coastal (Portland, Seattle, BC, though not in this boat), but mostly on the Columbia River, Oregon and Tennessee Lakes. Easy to get complacent on a closed lake! Anyway, any and all advice is welcome!

Thanks in advance
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Old 23-06-2014, 16:12   #2
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Re: Solar and AGM'S

My understanding is that the real issue with AGMs is that they need to be charged to 100% regularly and are not as forgiving of partial charging as FLA.

But far as charging AGMs with solar I don't see what the problem would be. Just be sure you can adjust whatever controller you use to match an AGM charge profile.
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Old 23-06-2014, 16:35   #3
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Re: Solar and AGM'S

Many, probably most solar controllers have an AGM battery setting. But unless you are charging at high rates, like 10% or more of the batteries capacity, I wouldn't worry about it.

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Old 23-06-2014, 16:50   #4
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Re: Solar and AGM'S

Thanks,
I am still looking at solar panels, regulators, controllers and the like, trying to sort out what I need and how much. I plan to convert all my incandescent lamps to LED soon to cut down on current draw. I'll start perusing topics and posts to avoid a redundant subject/question. I'm looking forward to becoming a regular fixture around here soon - Thanks
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Old 23-06-2014, 18:24   #5
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Re: Solar and AGM'S

I use solar via an outback flex80 to charge my bank of Odyssey 1800 AGM batteries. Works great, keeps them topped up most of the day.


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Old 23-06-2014, 19:37   #6
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Re: Solar and AGM'S

Short answer is there is no issue with solar charging AGM and if you go over 40w get a controller.

If you do go with solar read this.

Installing A Small Marine Solar System Photo Gallery by Compass Marine How To at pbase.com

I am totally rewiring and upgrading my boat which happens to be the same size as yours and probably designing for a similar purposes so I just made all the decisions that you are about to.

The best advice I got (too late) was get a way to measure your consumption first. Then keep track of your consumption for a while.

You've been living aboard 15 years and are probably very used to unlimited power with your shore charger.

This will get complicated quickly because you will find that your consumption will be higher than what you have available.

The best sequence I have decided on is this

1. Monitor your consumption and decide a target daily use for your boat I will guess 50-80 amps like me
2. Decide how many days you want to go without recharge compared to battery space - for me this became 2 days
3. Size the battery bank at 50% consumption - for me 3 batts @ 100 a/h = 300/h
4. I have 200 a/h house and ~25% of start batt to use or - 125 amps useable
5. Decide your charging strategy.

Charging -

1. 70amp alternator run ~30 minutes a day = 20-25amps
2. 100w solar @ 80% efficient X 8 hours/day (tropics) = 53amps

My energy budget has to come in around 70 amps

I don't know how you feel about aesthetics but getting more than 100w solar on your boat or my boat starts to get ugly quickly.

Battery monitor - Living on hook for a while you will need to know about your batteries. I have done the research and the Smartgauge is the way to go today.

The only drawback is that it doesn't measure or track amps consumption and I have not yet found a separate (cheap) gauge to do that.

The Victron BMV602 does this but for "monitoring" the charge status it is inaccurate (due to practical operator limitations not the gauge). You need something like this for step 1.

I have almost convinced myself to get both but I am still looking for a cheap digital amp counter.

If you've gotten this far and are still hanging on the last thing is how to charge two banks with one system - The simplest may is to wire everything to house and put an ACR (charge relay) between house and start)

So a ton of complexity.

Now - You already have a shore charger - I think another way to go for you is forget everything above - get a suitcase hondagen and a gas can. I recommend buiding a small vented box on the foredeck rail somewhere and store fuel and generator out of the cabin and lockers.
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Old 23-06-2014, 20:03   #7
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Re: Solar and AGM'S

AGMs are still flooded batteries - just sealed. AGM's have slightly different charging voltages but most solar controllers have a setting for AGM's.

100 watts of solar seems kinda small if you plan on having a fridge. We have over 500 plus a wind generator and we can generate about 150 amps on a very good solar day here in northern florida.

However, we have regular flooded batteries so they are less efficient (charge-acceptance wise) and are therefore slightly less efficient then the AGM counterparts for marginal solar configurations.

Since you have no inboard you may want to consider a honda generator instead of a large solar array. The 1000i is quite small and fuel efficient, I think .6 gallons an hour at rated output.
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Old 23-06-2014, 20:14   #8
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Re: Solar and AGM'S

I suggest you spend an hour or so reading Handy Bob's stuff. He has a lot to say about living off-grid. https://handybobsolar.wordpress.com/

Marinebeam Replacement LED bulbs for your existing boat fixtures (read the LED IDIOT's GUIDE & other tech page stuff) or Marine Lighting - Boat Lights - Yacht Lights - Imtra PWM current regulated LED lights
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Old 23-06-2014, 20:53   #9
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Re: Solar and AGM'S

I use Morningstar solar controllers 15 amp PWM models for both my 12 volt Gel house bank and my 48 volt AGM propulsion bank. They have switch settings for Flooded, Gel and AGM. Been operating for over seven years without a single problem. As others have said watch your energy usage if you are going to totally rely on solar. I recommend you change EVERY incandescent bulb on board from the mast on down to LEDs for the biggest energy savings.
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Old 23-06-2014, 23:19   #10
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Re: Solar and AGM'S

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Originally Posted by sailorboy1 View Post
My understanding is that the real issue with AGMs is that they need to be charged to 100% regularly and are not as forgiving of partial charging as FLA.....
Your understanding is flawed I'm afraid.

Justin Godber at Lifeline has been one of the few manufacturers to come out and say you should charge batteries regularly to 100% otherwise they sulfate. In the same article on morganscloud.com he says this also applies to all lead acid batteries, AGMs, GELS and FLAs. They are all wet lead acid batteries.
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Old 24-06-2014, 05:14   #11
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Re: Solar and AGM'S

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Originally Posted by sailinglegend View Post
Your understanding is flawed I'm afraid.

Justin Godber at Lifeline has been one of the few manufacturers to come out and say you should charge batteries regularly to 100% otherwise they sulfate. In the same article on morganscloud.com he says this also applies to all lead acid batteries, AGMs, GELS and FLAs. They are all wet lead acid batteries.

Of course you should regularly charge your batteries to 100%! I never said otherwise.

I still believe my understanding. I take my understanding from stories of people using their batteries basically the same way. When I hear/read stories of boats with solar out on a mooring with AGMs lasting 3 years compared to regular FLA batteries lasting 5-6 years; I believe it is charging related.

But - I'm not an expect and even sometimes a ****
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Old 24-06-2014, 05:55   #12
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Re: Solar and AGM'S

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Originally Posted by sailinglegend View Post
Your understanding is flawed I'm afraid.

Justin Godber at Lifeline has been one of the few manufacturers to come out and say you should charge batteries regularly to 100% otherwise they sulfate. In the same article on morganscloud.com he says this also applies to all lead acid batteries, AGMs, GELS and FLAs. They are all wet lead acid batteries.
I disagree. OK; they are all wet lead acid batteries that will sulphate if not taken frequently to 100%. That is not the whole story though. If you have FLA you can equalize the hell out of to get the lazy sulphate that covered the plates back into solution to turn into sulfuric acid. You cannot do he same with AGMs because the electrolite does not work the same way.

Not that I advocate equalizing FLAs as a substitute for proper charging, but it is a good remedy even if it hurts the plates a bit.

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Old 24-06-2014, 06:24   #13
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Re: Solar and AGM'S

AGMs have no place on a boat , waste of money. You can't use the advantages and you get all the disadvantages

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Old 24-06-2014, 08:48   #14
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Re: Solar and AGM'S

"AGMs have no place on a boat..."

My AGM's are in two places on my boat. One is mounted on end to correct a listing problem.
They have worked GREAT for 10 years. Never touched them for maintenance.
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Old 24-06-2014, 09:12   #15
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Re: Solar and AGM'S

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....But - I'm not an expect and even sometimes a ****
My Lifeline AGMs are now in their 10th year.
Not all AGMs are the same, many are not designed to be discharged to 50%, they are for Solar or Telecom standby use.
Their main advantage is that they charge FASTER than FLAs, even with modest Solar Arrays, you don't need a 200 amp charger to get the best out of them, but that will also help.
There are NO disadvantages except the price - mine can and should be equalized regularly.

Why so many negative posts when the OP was asking for help with the AGMs he already has?

If you ask someone the time you don't want a long lecture on why haven't you got a watch, and which is the best watch to buy.

Please everyone offer useful feedback, not feedback based on ignorance.

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