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Batteries-did I just make a mistake?

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TCurran
Admiral

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USA
588 Posts

Initially Posted - 01/09/2013 : 03:58:09

Had to replace my boat batteries, I had two Duralast group 27 dual purpose wet cell batteries. Was talked into (because of the price offered) two Optima Blue Top AGM group 27s. As I said, was offered a deal hard to refuse, essentially only $50 more for the pair over replacing with wet cells. What I didn't notice till I got home was the difference in amp hours, 115 (wet cell) versus 66 (AGM) Did not realize there was such a difference between the two.

What's the thought, should I return the Optimas???

Tom Curran
1981 Capri 25 Hull #101 "Dirty Debbie"
1988 Watkins 30
PAFB, FL

Edited by - on

britinusa
Web Editor

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USA
5404 Posts

Response Posted - 01/09/2013 : 05:26:46

Better batteries, but do you need the AH's?

Paul

Edited by - on

Bill Holcomb
Admiral

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USA
769 Posts

Response Posted - 01/09/2013 : 07:36:26

Hi Tom,
The batteries that you bought will work fine. They will use up their charge much quicker though than the wet cell batteries. If you have shore power and a marine smart battery charger this shouldn't be a problem unless you are planning some long trips away from the marina AND you have a lot of electronic equipment running all the time.
Bill Holcomb - C25 Snickerdoodle #4839

Edited by - on

TCurran
Admiral

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USA
588 Posts

Response Posted - 01/09/2013 : 08:01:26

Bill/Paul,
Thanks, I understand they're suppose to be a better battery and technology, just was real supprised at the difference in amp hour.

I don't have shore power, but use a solar panel to keep them charged at the dock. They don't sit long, since use the boat 2-3 times a month. I don't normally use alot of power during my normal sails, but do venture out for a few days once in a while. I was planning upgrading my solar panel to something like DavyJ's and installing a ice box. So...this might just move the solar upgrade up to the front of the line.

I haven't installed them yet and I guess looking for a reason not to return them, could not beat the price and thought they were a great upgrade. Like Bill said, they should work fine for my application with an added plus of not having to become a contortionist and climb down to fill the batteries with water.

As always, thanks for the advice.

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 01/09/2013 : 10:29:12

Only you can decide if the "advantages" are advantages in your use, but you have less capacity than the average group 24 in a group 27 case. The advantages are rapid recharge if you have a high output charging system of 50 - 100 amps, vibration resistance that isn't an issue in a sailboat, no acid spill if you capsize, and no maintenance. I have never had to top off electrolyte in my Walmart batteries and will stick with more amp hours for less money. AGMs probably live longer in the engine compartment of a planing powerboat, but I am yet to be convinced of their value in a sailboat. I have gone back to "maintenance free" after the second AGM in my Miata because they didn't last any longer than my other car batteries.

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pastmember
Master Marine Consultant

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2402 Posts

Response Posted - 01/09/2013 : 10:35:28

They have a special "charging profile" and you should confirm your charging set-up supports them. I would not put any battery that was not deep cycle in a boat.

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redeye
Master Marine Consultant

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3475 Posts

Response Posted - 01/09/2013 : 11:45:28

I think you made a mistake if you are solar charging only. My understanding is your solar is kinda like a float charge ( depending on the amp output of the panel )

If you get a charge from the engine, then I'd think you are nectar.

I'm guessing you have some research to do or tell us more details.

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KenDavis
1st Mate

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USA
69 Posts

Response Posted - 01/09/2013 : 12:01:21

a small advantage of AGM's is they don't outgas hydrogen while charging. For that reason they are considered safe to install inside the passenger compartment or trunk of cars.

that being said, the small rate of charge from solar or even normal shore power chargers (<10 amps?)wouldn't produce much.

I think I would want the extra capacity in amp hours. I didn't realize there was such a difference either.

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Stinkpotter
Master Marine Consultant

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Djibouti
9044 Posts

Response Posted - 01/09/2013 : 12:34:51

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by TCurran
 ...What I didn't notice till I got home was the difference in amp hours, 115 (wet cell) versus 66 (AGM)<hr height="1" noshade id="quote"></blockquote id="quote">WM's Group 27 AGM is rated at 92 amp-hours, undoubtedly at a higher price. Maybe this explains the "hard to refuse" price.

I know some folks who use AGMs in their sailboat up here, partly because they can leave them aboard, unattended, over the winter. They hardly self-discharge at all, and therefore won't freeze. Other than that, I'd say the case for them is dubious. My wet-cells from Defender have gone five seasons now without needing a drop of water. (Searching for wood to knock on...) The Optima AGMs that came with the boat were immediately fried by the Honda outboard.

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 01/09/2013 : 14:38:59

And as Frank said, there is no reason to have dual purpose, start/deep cycle, with a 9.9 outboard. Design changes for starting loads will result in a shorter life than in a straight deep cycle, and a d.c. will provide more amps than you will ever need for starting.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 01/09/2013 : 15:50:05

Tom,
I think you're probably fine. I installed a couple of the same batteries about three years ago and have had no trouble with them at all.

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Joe Diver
Master Marine Consultant

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USA
1218 Posts

Response Posted - 01/09/2013 : 17:51:17

You're probably okay unless you need the amp hours. Depends on your energy use profile really.

The only reason we put Optimas (AGM's) in Jeeps is because Jeeps sometimes tip over, or get to extreme angles. Put them in the Corvettes because of heat extremes and g forces slamming around the track.

Same can be said of sailboats....but most of us aren't tipping our C25's over or heeling so extreme a wet cell would spill. While an advantage in a pitchpole or violent broach, usually a little spill from wet cells is the least of your worries at that point.

Optimas are great batteries though and the group27 blue tops are marine deep cycles that also have good cranking amps.....so think bass boat, ski boat. No problem in a sailboat.

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Voyager
Master Marine Consultant

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USA
5308 Posts

Response Posted - 01/09/2013 : 20:40:08

I'm very surprised that the AH are so low. I took a quick look to verify the numbers but I haven't located anything concrete. If the AGMs are starting batteries you'll get a lot of current for short bursts, but low current draw over extended time may be compromised.
Then I thought of something very fundamental. A battery "contains" a fixed amount of AH total. Say 110 AH. You can safely discharge the battery to approximately 50% of its total AH rating. So the "effective" AH rating may be 55. Could this be what's going on here?
Even if the numbers are correct, two x 66 AH will provide you a LOT of power for lights, radios and chartplotters. That said, if you're accustomed to the power range of two wet cell batteries, it's likely you will be disappointed with the AGMs.

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 01/10/2013 : 12:25:16

I checked Optima's website, and the batteries are indeed 66 AH to total discharge @ 10.5V.

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redviking
Master Marine Consultant

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USA
1771 Posts

Response Posted - 01/10/2013 : 13:43:12

I'm a juice junkie. More amps is always better. I had 5 group 27's with a 1/2/all switch on my C25. If caught out, I liked knowing that my vhf ALWAYS had plenty of juice. And if necessary or for cheap cruising, I could hang on the hook for a couple of weeks before even thinking about the batteries.

Besides, the extra three were aft under the aft berth and near centerline. Helped performance!

Sten

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TCurran
Admiral

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USA
588 Posts

Response Posted - 01/10/2013 : 13:50:14

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave5041
 I checked Optima's website, and the batteries are indeed 66 AH to total discharge @ 10.5V.
<hr height="1" noshade id="quote"></blockquote id="quote">

To answer some of the questions, I am not a major energy user, the cabin lights are all LED (thanks to the PO), I use an LED anchor light and rarely run my depth sounder. My normal use is just the stereo, Sirius receiver, and GPS/chartplotter. I do need to run the numbers for my equipment to confirm, but I'm pretty sure the Optima's will handle my energy needs 99% of the time.

Again, appreciate all of the input.

Edited by - TCurran on 01/10/2013 14:07:30

OLarryR
Master Marine Consultant

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USA
3408 Posts

Response Posted - 01/10/2013 : 21:22:49

I recently replaced my 8 year old Group 25 flooded batteries with Group 34 AGM batteries. The AGMs are 55Amps and believe the flooded batteries were 65Amps. My solar controller has a setting for AGM batteries and I also decided to hook up the sensing wires from the controller to the batteries for a more accurate/tweaked charging rate. So far, I have notoced that my 20 watt panel has charged these batteries to whopping 14.1 volts. That to me is a pretty high standing voltage considering that 7 years ago my flooded batteries were charged to a standing voltage of about 13.2 - 13.3 volts and decreased to about 12.7 volts this past year. I use my batteries for relatively low load usage - mainly the fishfinder and occasional nav light usage. Not much more than that. So far, so good. Only time will tell.

Here is an interesting thing to consider and not necessarily so bad if your AGMs are not of extremely high Amps. My Guest battery charger (which I rarely use - Only when in a visiting marina and utilizing shore power) independently charges both batteries at max 5Amps on each (5+5 charger). The instructions indicate not to utilize on batteries that are greater than 55-60Amps. Okay...my flooded batteries were probably already lower than what they were rated at by the time I bought the charger. But the charger is fine for my 55Amp AGMs. As far as outboard charging...well, I generally do not use my outboard for all that long - mostly just in and out of the marina. However, I have a view screen on my fishfinder that will display the battery voltage and when my Honda outboard is running, depending on the throttle speed, it is charging the batteries at around 14.2 - 14.6 volts. From what I recall, that is about the recommended charging voltage recommended for AGMs.

I would have probably gotten another year out of my flooded batteries but I had bought one AGM to use as a battery backup to run a bilge pump for my home sump , in case my electric went out during Hurricane Sandy and my sump pump stopped. But we never did lose electricity. So....then I decided to buy another AGM and replace my boat batteries. If they last as long as my flooded batteries, then I will be happy. No water to periodically check and add !

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