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Old 15-04-2010, 07:13   #1
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Time for Batteries

I have 3 West Marine PV-27DC 86AH sealed gel batteries. The other day, the display on my charger started bouncing all over the place, when I had amps selected. Since then it's not shown more than a few amps (less than 10). According to a mechanic around here, batteries are usual good for only about 4 years or so, so they're probably starting to go on me. Well, after pulling the cover off my battery compartment, I confirmed that. Mine were purchased in 2002!

Since I'm replacing them anyway, already spending money I don't have, just got myself a giant fridge and some more solar, and going on the hook in the next few weeks. Should I replace them with the current West model, probably the SeaGel 8G27M?
Or should I go with something bigger, better, higher capacity, etc?

I can't go much bigger than what I already have, though,
about 9-1/2 H x 6 W x 11-3/4 L, because of the size of the compartment. It's L shaped with one side measuring about 13 x 12 and the other 9-1/2 x 14. I could probably go about 11" high. I'm thinking if I went with AGM slim lines I could get a little more capacity, but I'd only be able to fit 2 of them, so not much more. Can you put different size batteries on the same bank? AKA 2 big slim lines and one smaller one?

Any suggestions?

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Old 15-04-2010, 08:09   #2
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You would be able to fit in far higher Ah battery capacity in the space you have available if you decided to fit LiFePO4 batteries in preference to sealed gel lead acid batteries. Also about half the weight of your current batteries.
Of course it all comes down to if you want to spend more for the higher performance and increased total battery capacity which lithium batteries would provide.
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Old 15-04-2010, 08:14   #3
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Also check different suppliers in your area for prices.
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Old 15-04-2010, 08:34   #4
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Conventional wisdom says wet cell 6V "golf cart" batteries are the most durable at the best price per watt hr capacity. AGMs have their advantages but only if you want to pay the premium, have the charging system capable of taking advantage of their rapid charge capability and are of the type who think putting water in them periodically is a maintenance headache.

It is a decision you can make intelligently only after you first figure out what your power needs are - how much power do you need on a typical cruise? What can your existing charging system properly recharge in a reasonable time?
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Old 15-04-2010, 09:00   #5
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Quote:
Originally Posted by LiFeTech Energy View Post
You would be able to fit in far higher Ah battery capacity in the space you have available if you decided to fit LiFePO4 batteries in preference to sealed gel lead acid batteries. Also about half the weight of your current batteries.
Of course it all comes down to if you want to spend more for the higher performance and increased total battery capacity which lithium batteries would provide.
How much cost?
What advantages do they have over AGM?
Capacity, charge time, battery life, etc?

Will they work with a Morning Star solar charge controller and a Xantrex Freedom 20 inverter/charger?
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Old 15-04-2010, 09:14   #6
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Originally Posted by S/V Illusion View Post
Conventional wisdom says wet cell 6V "golf cart" batteries are the most durable at the best price per watt hr capacity. AGMs have their advantages but only if you want to pay the premium, have the charging system capable of taking advantage of their rapid charge capability and are of the type who think putting water in them periodically is a maintenance headache.

It is a decision you can make intelligently only after you first figure out what your power needs are - how much power do you need on a typical cruise? What can your existing charging system properly recharge in a reasonable time?
My solar controller and my inverter/charger will work with the AGMs, but even if I don't go with them, I'll at least get sealed gel again. Getting to that back battery to put water in would be a big PITA, since it's really buried back there.

I'm not sure if I really do need the extra capacity. All my lighting is LED, I have a handful of chargers for dive lights, camera, strobes, electric toothbrush, etc. that will need to go on the inverter on occasion (maybe once/twice a week tops). A small shop vac that may go on the inverter on occasion. Then just laptop, all the normal boat things, instruments, water pump, etc. The only big draw is the fridge, which draws about 6 amps max.

Even if I replace them with the current West model, I'll have 258 Ah, and I'm also going to have 420 watts of solar. I haven't done any real math, but I may be fine. Conventional wisdom does say more capacity is better, though, so I'm just throwing the idea around. I'm also thinking more capacity will make it easier to get by with just solar, even if there is nice long cloudy week or so. I'd rather not add a wind genny too.
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Old 16-04-2010, 05:27   #7
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How much cost?
What advantages do they have over AGM?
Capacity, charge time, battery life, etc?

Will they work with a Morning Star solar charge controller and a Xantrex Freedom 20 inverter/charger?
Initial cost is considerably more than lead acid but actual cost over the life of the battery works out to be around 70% of the cost of using lead acid.
Advantages over AGM.....less than half the weight, environmentally friendly (does not contain sulphuric acid and does not evolve explosive hydrogen gas while charging), life of more than 3000 cycles, charge time for a completely discharged battery to more than 90% capacity can be achieved in 15 minutes.

I recently shipped a couple of LiFePO4 batteries to a guy who is changing over from AGM to lithium for the house power on his boat. He already has a Morningstar MPPT solar regulator and I have been going over the programming settings so he can optimally charge his new lithium batteries with his existing Morningstar solar charge regulator. I must say the guys at Morningstar have been very helpful with their technical advice also.
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Old 16-04-2010, 06:02   #8
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grunzster,

Before you spend any (more) money, check out those gels. I have some gelled golf-cart batteries which spent their first 10 years on a sailboat and their last 3 years in my basement, where 1.5 years of that life was for a series of battery tests. They still check out pretty good, and they're now 13 years old!

Gels, if not overcharged, and if kept reasonably well charged and well treated can last a very long time. Longer than AGMs and longer than flooded batteries, depending on type of service.

I'd do a proper load test on them (either with a Midtronics electronic tester or, even better, with a known load over a 20-hour period, with the load calculated to deplete the batteries (to 10.5 volts) after 20 hours. See how long they go...that's the only way to be sure what remaining capacity they have.

If you're really planning to add batteries, though, I'd go with all new ones. Cheapest initial outlay, and pretty good value overall, are flooded batteries -- as mentioned, the golf-cart size is very popular. (I have eight T-105's on my boat, and two at home for my radios).

Other types of lead-acid batteries (AGM flat, AGM spiral, Gells, etc.) and other chemistries have both advantages and disadvantages, but they all involve a far greater initial outlay and their longevity is dependent on type of service.

Bill
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Old 16-04-2010, 12:39   #9
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Bill, Definitely think I'm going to go new and upgrade. I also have a dedicated starter battery, that a few owners back decided I need, contrary to what the manufacturer believes. That's a waste of perfectly good house battery space.

As long as I'm going to rip things apart what are people's opinions, 1 battery bank or 2? Is there really any advantage to having 2 banks if you're living aboard on the hook? Other than a reserve for the big fridge that already sucked 1 bank dry?
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Old 16-04-2010, 12:59   #10
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The preferred method these days is to have one large house bank, rather than two smaller ones, and a separate start battery.

Reason is that you'll draw one large bank down only half as much as each smaller bank when in use, and thereby will:

1. extend the battery life (you'll be cycling down to, say, 25% instead of 50%); and
2. double the rate at which you can charge the house bank, thereby cutting fuel and maintenance costs considerably.

How large should the house bank be? Depends very much on your living/cruising style, and the loads it will be expected to sustain. Also, depends on your charging setup: shore charger, alternator, generator, wind generator, solar panels, etc.

So, my vote -- as a professional working in the field -- is for a single larger house bank, a separate starter battery, and an EchoCharge or DuoCharge device for keeping the starter battery fully charged -- automatically, with no need for flipping switches or "combining" batteries.

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Old 16-04-2010, 13:10   #11
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Really!

So what I thought was previous owner weirdness was actually an upgrade to bring the boat to current standards? The house and engine starter batter both go to a Pathmaker auto switch and then to a Freedom 20 cherger/inverter. Also the solar controller I'm getting is a duocharger.

But why not have the engine just start off the house bank? Especially if it's a smaller engine (not going to draw as much during start up)? And that way get the benefit of an even bigger bank?
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Old 16-04-2010, 13:23   #12
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Quote:
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Really!

So what I thought was previous owner weirdness was actually an upgrade to bring the boat to current standards? The house and engine starter batter both go to a Pathmaker auto switch and then to a Freedom 20 cherger/inverter. Also the solar controller I'm getting is a duocharger.

But why not have the engine just start off the house bank? Especially if it's a smaller engine (not going to draw as much during start up)? And that way get the benefit of an even bigger bank?
You can, and some people do. Some even swear by the method.

However, it's not a particularly good thing to do. What happens if your big frig draws the house bank down so you can't start your engine?

I believe you should ALWAYS have a fresh, fully charged battery for engine starting. Just because :-))

And, if the start battery takes up room you need for another house battery, move the start battery. Somewhere. There's always a place for that iddy-biddy start battery :-)

Bill
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Old 16-04-2010, 14:32   #13
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I moved from the 1-2 both to 2 separate banks... one very large and the smaller one for engine starts ONLY. The engine batt is on an echo charge ... topped up by the large bank and so it's never below fully charged.

The big house bank can go down, but there's always the engine batt to start the engine and run the alternator which charges the big house bank.

This system is great.. except it if you get a bad cell in one of the paralleled house banks. So far... so good.

You can use an BlueSeas 8080 switch which lets you combine the batts for house and starting purposes... but why?
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Old 16-04-2010, 18:53   #14
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Good point Bill.

I think I have it figured out...well except the batteries I wanted aren't shipping for a few weeks. Since the AGM can be installed in an orientation, going to take some rearanging of my battery compartment, and moving some switches, one of my outlets, etc. But I should be able to double my capacity and then some. Think I may even be able to cram that start bettery in there, and get it out of the locker they originally installed it in.
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Old 22-04-2010, 04:05   #15
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if you have gel batteri bank, and want to have a masterv 100 amp charger/200w inverter.
How big a Gel bank will you need, so you dont destroy you gel batteries when useing the inverter, say taking out 2000w ?
is it the same for AMG ?
Normal led can be a lot smaller. and supply enof power to the inverter without killing the batts.

anybody ?
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