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Old 02-09-2011, 02:40 PM   #1
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Battery Question

Is it possible to show good voltage at the battery with the charger off and still not have enough cranking amps?

I am still messing with my bow thruster. I got a new joystick which works but now the thruster will only run for a minute without running the battery down.

The battery is 6 years old but is a Lifeline 8D AGM that does nothing but lay there until I need the truster or windlass. It has not had very much use in its lifetime. We don't anchor but we do thrust occasionally.
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Old 02-09-2011, 03:07 PM   #2
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RE: Battery Question

Absolutely. Let the battery sit for a while off charge before you read the voltage. Take a reading while it is under load.
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Old 02-10-2011, 08:58 AM   #3
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RE: Battery Question

That particular battery is not cheap.....jus sayin'!!!
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Old 02-10-2011, 11:52 AM   #4
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RE: Battery Question

I have one more test to do and here is why.

I have been messing with the thruster for a couple of weeks. At dockside it only gets an echo charge. It takes this trickle charger a long time to top off an 8D. Sometimes 40-50 hours if it is really run down...according to a boat electrician that I spoke to. He said: "When the thruster is normally used, the engine is running, thus putting a good charge into the battery and keeping it topped off. When the engine is turned off, the thruster battery has done its job and gets only the trickle from the echo charger to maintain a full charge."

He also said that a 6 year old AGM is past it's prime, but not necessarily bad.

The test is to take the boat out and run it long enough to get the battery restored to full charge and then see how long the truster will run.

That is the current plan.
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Old 02-10-2011, 12:18 PM   #5
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RE: Battery Question

Doc -- It would seem that your shore power charger should*keep the AGM topped off. If not, you have either a battery or charger issue to deal with. Sometimes when leaving the dock, a thruster is necessary (not for a minute though) so having the battery charged up at the dock is important.

Did you do the load test RickB suggested? Is this a new problem or one that has been there for a few years?
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Old 02-10-2011, 01:38 PM   #6
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RE: Battery Question

It failed the test so it is coming out. I just got back from an spin in the harbor that lasted over an hour. The battery never did take a charge above what it had at the dock. My other batteries got up to normal running voltage.

Now I have to find two straping young men to pull it out of the hole and drop in the new one. 161 pounds. In the community where I live finding someone under 65 is tough.

Sunchaser: it is a new problem that began when the thruster started failing a couple of weeks ago.
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Old 02-11-2011, 06:28 AM   #7
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RE: Battery Question

Harbor Freight has a battery load tester for $19.95. Not a sophisticated instrument, but it will test a battery at rest and under load.

This is far easier than taking a battery to a battery retailer to have it tested.

I just replaced four house batteries and the charger. I'll never know if the charger failed and killed the batteries or the other way around. Of course, the replacemenrtt batteries had the terminals reversed from the originals so that required some modifications to the wiring, but why not - it's a boat!.
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Old 02-11-2011, 08:01 AM   #8
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RE: Battery Question

Doc, This depends on your charging system unless I am missing something. If your alternator is charging the house bank only and the echo charger is still charging the thruster battery while under way, then nothing is going to change from charging at the dock. The little secret that very few AGM manufacturers tell you is that if you do not recharge an AGM to 100% every time you go through a discharge/ recharge cycle, you will reduce the life of the battery. AGMs do not last as long as well maintained wet cells, and I usually only recommend them for systems that have batteries stashed in locations that make checking battery water and refilled very difficult. Chuck
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Old 02-11-2011, 09:37 AM   #9
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RE: Battery Question

Capt Chuck,

The echo charger is 110 volts. When I am running I normally do not run the generator so the battery is getting charged by the alternator.
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Old 02-11-2011, 09:44 AM   #10
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RE: Battery Question

Hi Chuck,

My experience with AGM's is somewhat different.* I do extended cruising and anchor 2/3-3/4 of the time. with no generator, and rarely bother to plug into shore power.* I use a Link 2000 battery monitor, so I have a good handle on how far my batteries get recharged (it's sure not always 100%) and how well they are performing.*

My house bank batteries, two G31 "dual-purpose" 12v AGM's (made by East Penn - Deka) are ten summers old and still going strong.* They've spent more than 600 nights at anchor so far.* Seems to me that with proper regulators and not much severe discharging abuse, these Deka AGM's can be expected to be very long-lasting.

The Optima AGM's which start my Cummins pickup (sitting outside in below-freezing temps much of the winter) are 9 years old and going strong.


Doc:* I would have no worries about replacing your 8D with multiple smaller batteries - 6V golf carts for example (and they're available in AGM as well).* Loads of cruisers have done this with great success - some banks as big as 8 or more 6V's.
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Old 02-11-2011, 11:49 AM   #11
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RE: Battery Question

I now have a new 8D AGM in hand and am waiting for two young constructions workers from down the street to show up.
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Old 02-11-2011, 12:17 PM   #12
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RE: Battery Question

Quote:
RCook wrote:

Hi Chuck,

My experience with AGM's is somewhat different.* I do extended cruising and anchor 2/3-3/4 of the time. with no generator, and rarely bother to plug into shore power.* I use a Link 2000 battery monitor, so I have a good handle on how far my batteries get recharged (it's sure not always 100%) and how well they are performing.*

My house bank batteries, two G31 "dual-purpose" 12v AGM's (made by East Penn - Deka) are ten summers old and still going strong.* They've spent more than 600 nights at anchor so far.* Seems to me that with proper regulators and not much severe discharging abuse, these Deka AGM's can be expected to be very long-lasting.

The Optima AGM's which start my Cummins pickup (sitting outside in below-freezing temps much of the winter) are 9 years old and going strong.


*

Your experiences aside, this is a fact of life with AGMs and if ask directly the manufacturers will tell you the truth. You can also find it tucked away in some obscure part of their literature. Chuck
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Old 02-11-2011, 01:38 PM   #13
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RE: Battery Question

Captns Chuck and Cook, I think y'all are both correct. One is talking theory, the other reality. In theory, Chuck may be right. But in reality, wet cells likely don't get the exact care they need. So if you give each platform the same type of neglect, the AGMs are likely to outlast the wet cells when equally neglected....regardless of which is better when maintained perfectly. So since we all neglect our batteries to some degree, the AGMs are likely to outlast the wet cells...ANd as you pointed out Cook, they do!!!!
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Old 02-11-2011, 02:23 PM   #14
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RE: Battery Question

Wet Cells---Most common, flooded lead acid, low price, most
maintenance, use all same models-----4-8 years.

Gel---gel type electrolyte with silica added, no maintenance, less gassing,
No spillage---cons, kill easy, overcharge damage, much more expensive----
2-5 years.

Glass Matt or AGM, absorbent glass matt---Similar to wet cell---cons,
shorter lifespan, killed if overcharged, must recharge 100%-----4-7 years.
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Old 02-11-2011, 02:55 PM   #15
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RE: Battery Question

In my experience, AGMs last longer. They are just so damn expensive.
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Old 02-11-2011, 06:45 PM   #16
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RE: Battery Question

Chuck, are you grinding an ax here?
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Old 02-11-2011, 07:35 PM   #17
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RE: Battery Question

5 years since we finished Delfin's refit.* 1380 amps of Northstar AGM, and as far as I can tell, there is zero difference in performance between these batteries when new, and now.* I'm not sure what the theory is, but in practice in this installation AGM is performing better than any other battery I have had for a house bank including wet cells and gel.* I'll let you know in 5 more years how it's going.

I do acknowledge that you need more precise and accurate charging for AGM than wet cell, but that equipment is inexpensive and readily available.
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Old 02-12-2011, 07:27 AM   #18
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RE: Battery Question

Quote:
Baker wrote:

In my experience, AGMs last longer. They are just so damn expensive.

I think most experts would side with you on this one.* I made the decision, based partly on the difficulty of checking the electrolyte levels, to replace my four house batteries with AGMs.* I also had to replace the charger which*had failed.

With the new AGMs in place, the*bow thruster runs faster than it ever did and theres at least a volt less voltage drop when the inverter is powering the microwave as indicated by the display on the inverter.*

ABM batteries are said to have a lower internal resistance.* My experience leads me to believe that this is true.

As for "expensive" I can't argue on that but if they save me the agravation of trying to check the electrolyte levels every month, provide better performance, and last longer, it's worth it.
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Old 02-12-2011, 10:43 AM   #19
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RE: Battery Question

AGM's last longer and are more expensive. Plus when they die, it is a sudden death. One minute it is faithfully on duty and the next minute it is toes up without even a faint moan.

I can now report that the construction workers did not show and I was miffed. Last night at happy hour at the yacht club (don't you know) a couple of members chastised me for wanting to hire it done. We can do it, they said. So this morning I called the most vocal one...69 years old... and he said WHAT? I said WHAT? Anyway he came over and this morning we pulled the old one from under the floor of the forward stateroom, up the stairs to the pilot house, down the stairs to the salon and out to the cockpit. The new one was then piss anted back the same way and dropped in the hole.

Each of us needed bandages to stop the bleeding (baby aspirin thins blood) but now the thruster runs like new. There is joy in the house.
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Old 02-12-2011, 02:59 PM   #20
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RE: Battery Question

Quote:
Doc wrote:

AGM's last longer and are more expensive. Plus when they die, it is a sudden death. One minute it is faithfully on duty and the next minute it is toes up without even a faint moan.

I can now report that the construction workers did not show and I was miffed. Last night at happy hour at the yacht club (don't you know) a couple of members chastised me for wanting to hire it done. We can do it, they said. So this morning I called the most vocal one...69 years old... and he said WHAT? I said WHAT? Anyway he came over and this morning we pulled the old one from under the floor of the forward stateroom, up the stairs to the pilot house, down the stairs to the salon and out to the cockpit. The new one was then piss anted back the same way and dropped in the hole.

Each of us needed bandages to stop the bleeding (baby aspirin thins blood) but now the thruster runs like new. There is joy in the house.
Doc, was that at Isles YC?* We stayed there a couple of nights last spring.* Great club and food.* You will teach those guys not to talk too much around the YC bar.

*
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