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Old 30-12-2015, 19:54   #16
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Re: Batterie Gel or AGM

Originally Posted by 2Wind View Post
I'm with Mark here.
Start batteries should not be "deep cycle" and have generous CCA to exceed the engine manufacturer's recommendation. .
If starting is via a separate battery, it doesn't make sense to use a deep cycle battery for economic reasons but assuming it has adequate CCA, there is absolutely no harm in using a deep cycle.

We actually just have a single bank for everything (We can easily pull start the motor so no concerns with a dead battery bank)

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Old 30-12-2015, 22:01   #17
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Re: Batterie Gel or AGM

Originally Posted by 2Wind View Post
Over spec cables are not to be sneered at especially when cable run is long, for example when traversing between hulls for the port to starboard battery link.

When a current of 100 A flows through a cable of 50 mm> cross section (AWG 0) and 10 m length (30 ft), the voltage drop over the cable will be 0,26 Volt. Similarly a current of 50 A through a cable of 10 mm> cross section (AWG 7) and 5 m length (15 ft) will result in a voltage drop of 0,35 Volt!
Thanks for delivering " Cable Sizing 101". ��

I'm not sneering, just pointing out that much Lagoon wiring is oversize. As are L400 gel start batteries. Not sure about other Lagoon models. I'd rather have a bit too big than too small in each case. The over spec battery cables that Lagoon fit, in the L400 that the OP owns, allow a house bank upgrade to a substantial size before cabling needs up sizing.

OP needs to understand that, unless he wishes to get very complicated battery charging systems, it is best to have batteries in both house bank and start roles that require similar charge voltages. That's why Lagoon fitted gel start batteries in the first place. Not because they are ideal start batteries, but because the buyer wanted a gel house bank, and the start batteries had to be compatible.

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Old 31-12-2015, 05:08   #18
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Re: Batterie Gel or AGM

Throwing my 2 centavos in on something to consider. When we bought Seapaws 2 the boat had gel cells on the house bank and the two single start deep cycle batteries. The surveyor didn't notice that those batteries lived under a bunk in a practically sealed compartment. The two deep cycle batteries will off gas when charging, not good under a mattress in a sealed box. I have gone to sealed AGM. on second set of batteries since we had the boat, got just over 7 years out of the first set. Best part was my good friend got the whole set for me through his company..(no charge/ free), 8 group 24's and 2 group 27's for the start batteries. I was not so lucky on the recent set, but I shopped around and got them for about $135 each at a battery warehouse type of place.

Long story short, be aware or where the potential off gassing style batteries may live if you purchase that type.

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Old 31-12-2015, 07:55   #19
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Re: Batterie Gel or AGM

VRLA batteries, both Gel and AGM, do not tolerate high temperatures as well as flooded nor can they recover from being sulfated from sustained discharge by equalization, the exception being Lifeline AGM. Unfortunately many builders design for batteries to live next to diesels, suffering through shut down temperatures over 200dg F. Temp sensors are cheap and a critical data point for optimizing the charge rate on VRLA, especially Gel batteries which are critically dependent on charge profile. You will destroy expensive gels by simply having the alternator regulator or solar controller drift above the 14.2 bulk limit and appropriate float. I've opened many premature failed gels with crystalized electrolyte. We've had tremendous success with Lifeline batteries, even for electric drive systems over the past 15 years. They have charge acceptance like LiFePO4 with out the very real risk of Lithium thermal runaway (several recent examples of boats lost through LiFEPO4 (lithium) chemical fires, same reason FAA shut down Boeings fleet last year). In addition, Lifeline warranties 80% discharge performance. They are pricey and require charge sources to have the appropriate charge profile, which most charge controllers do these days, but life expectancy is there. Hopefully Tesla or another big OEM will resolve the very serious issues with Lithium batteries so that we can someday shed the weight liability that come with calcium lead batteries, but for now that is where reliably safe energy storage technology is.
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Old 31-12-2015, 08:26   #20
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Re: Batterie Gel or AGM

Originally Posted by peterp View Post
Not too clued up on batteries, but my engine starting batteries are now 5.5 years old and whilst they are OK I feel it would be prudent to fit new ones. When I ordered my Lagoon 400 I ticked the box for GEL they have been and still are fine except the Genset starter battery I replaced after four years. I think I will stay with GEL batteries as I assume the charging system being alternators, solar, and generator are set up for GEL. Any one have any preferences.
I use and recommend the German made gels. The Prevailer I have in my boat is about 17 years old and no apparent loss of capacity. The energy density is lower than the AGM's by about 10% I believe but the peace of mind that acid is never going to leak out and eat everything up + the longevity and reliability makes it worth it to me. And yes, I know that AGM's are supposed to be leak proof but I have personal experience on a customers boat where the Dynasty AGM's only 3 years old leaked out a lot of acid that ate up the epoxy coated shelving, the engine, the electronics.. The AGM acid seems to be even more corrosive than the acid in a normal wet cell battery. I never have corrosion on the terminals of my gels, just a very clean battery. Probably some good AGM's out there but I see no need to experiment! Best of luck.

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Old 31-12-2015, 08:59   #21
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Re: Batterie Gel or AGM

when I picked up my new 39 year old sailboat on Long Island this spring, I suspected that the 4+year old schedule 27 wet cells might not be a good idea for the trip through Bermuda to its new home on St Croix. After days of research I came to the conclusion that the only benefit of AGM and Gel batteries was that you didn't need to check to be sure they wee wet. For less than the price of 2 AGMs or Gels, I bought and installed 4 schedule 31 deep cycle wet cells and check the water level once a month. I am very happy with my decision
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Old 31-12-2015, 09:04   #22
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Re: Batterie Gel or AGM

Mark (colemj) has given the best advice on this thread by far. The OP should reread those posts before making any changes. As noted, the OP asked about starting batteries, not house, and that is a completely different discussion. You do NOT need any kind of deep cycle battery for charging, but if you have a large enough deep cycle battery it will start engines just fine. It's just overkill.
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Old 31-12-2015, 09:26   #23
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Re: Batterie Gel or AGM

I have been boating for more than 50 years now and have lost more batteries because of a) forgetting to top them up, or b) (most likely) to have something left on somewhere which drained the batteries whilst I was not on the boat. Most battery systems have additional connections which bypass the main isolators for a radio, bilge pump or an other auxiliary use. A week of full discharge will kill a flooded battery.
At least with gel batteries they are more tolerant to being discharged and I don't have to worry about forgetting to top them up!
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Old 31-12-2015, 10:03   #24
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Re: Batterie Gel or AGM

I have several friends who cruise either full-time, or have made a multi-year voyage in the past, and they have had wonderful results from East Penn gel batteries. Ideally, you'd use the 6V conventional "golf cart" style batteries in parallel, as they are functionally different than the 12V batteries (better for deep cycle use).

For starting batteries, it's doesn't really much matter, except that your life will be simpler if you have a single battery chemistry on board, so that you don't have to worry about excessive voltages from one charging source damaging some other battery bank.

A friend who circumnavigated over a six-year period got 1,000 cycles out of a set of six-6V East Penn batteries, then replaced them, and got another 1,000 cycles out of the replacement set.

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Old 31-12-2015, 10:50   #25
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Batterie Gel or AGM

Once again, a reminder that the OP is only looking for a starting battery. He isn't concerned with capacity, and if he needs 80% discharge cycles, he has bigger problems.


Edit: oops, I responded before realizing there was another page of posts, and I can't figure out how to delete this from my tablet.

You do not need a parachute to skydive. You only need a parachute to skydive twice.
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Old 31-12-2015, 12:12   #26
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Re: Batterie Gel or AGM

Originally Posted by Joyful Noise View Post
After days of research I came to the conclusion that the only benefit of AGM and Gel batteries was that you didn't need to check to be sure they wee wet.
If that is your conclusion then you might do some more research.

Gel and AGMs:
Accept charge at a higher rate, shortening charge times. With large alternators the engine can be run less - a big win.

Similarly during discharge they hold higher voltages at higher loads - useful for electronics (particularly nominal 12VDC devices that were not designed for marine use and have issues at lower voltages). This was a big improvement for me.

Can survive deep discharges better. I think this is not much of an advantage because any serious cruiser simply doesn't let their batteries go flat.

Operate at any angle. I don't see this as much of an advantage, as long as the electrolyte is kept topped up in FLA batteries. My Carina sails on her ear yet I never experienced problems with my original Rolls FLA batteries.

Don't need added water. I am tempted to label this as silly, as checking the water levels every month is really no big deal, but in some installations access is difficult so for them it is an advantage. Even operating in the tropics I rarely added more than a cup/month total for three 31H batteries. If I had cared, I would have bought recombinant caps to reduce consumption to near zero for FLA.
As to the OP, given that his charge system is set up for gels he could use either gel or FLA for a starting battery. As others have said, the starting battery doesn't normally get drawn down very far so the somewhat lower charge voltage limits for gel shouldn't limit a full charge. Usually for starting batteries the problem is that they are held to high charge voltages after they are full due to the needs of the house batteries so it might actually be a tiny advantge for FLA. If the decision is to change to FLA then consider a sealed battery if topping up the water is an issue.

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Old 31-12-2015, 18:17   #27
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Re: Batterie Gel or AGM

We had to make a similar decision, but quite different. We were designing a new battery system for a cargo aircraft, we selected the 80 lb nicad. There are three reasons certain batteries die (nicad and possible lithium ion).

Neglect (number 1)

Charging profile, the intitial charge for a discharged battery is easy, once topped, the battery will burn off its liquid hastening number one (neglect), . Once topped, the battery should have a maintenance charge (smart chargers will do this). (Nicad)

Manufacturing defects, this one is troublesome as we could not find a vendor that didn't have issues. It was mainly the membranes that were defective. The result is thermal runaway. Generally water cooking off with rotten egg smell (acid). Adequate ventilation so you can breathe is recommended.

But to the point, if my batteries lasted 7 or more years, I first would be overjoyed and I wouldn't change anything, use the same battery when replacing.
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Old 01-01-2016, 00:36   #28
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Re: Batterie Gel or AGM

Doesn't sound like you need to do anything. Have batteries tested if you are concerned. Stick with what you have if they are working well.

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