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Old 03-29-2015, 08:34 AM   #21
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I'd agree with the probable load guesses.

The first time we were on the hard for the winter with AGMs, I charged the batteries approx. 1x/month. The next time, I purposely didn't do squat... and the AGMs only self-discharged to about 12.6V over a 4-month period.

Our AGMs aren't spiral wound, so dunno about that... Didn't know Optima or others made any spiral-wound 8Ds...

-Chris
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Old 03-29-2015, 10:31 AM   #22
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angus99...

I had an 8D AGM go flat on me (don't recall v reading but it was in the range of your low one). My issue was a bilge pump that blew a hose after spring commissioning and the pump ran continuously after the boat was launched - couple of weeks before I arrived to move it.
I charged mine w/ house charger while on board for a limited time - hooked up a low A trickle charger during the week when I was away and repeated the above until it came up. So far it has been OK - a real relief as mine was nearly new and half a boat buck apiece ($500).
Since then a marine electrician has advise me to make sure the AGM's are fully charged - up to 14.6-14.7V immediately before disconnecting batty leads. I had to change my batty type setting to do this and monitor what V was. When the charger switched to float (new setting was above recommended) I shut off the charger & disconnected batty. The maintainers I use CLAIM to provide a cycle which reduces sulphation - not sure if that played any role or not - but felt it wouldn't hurt.

I was back at the boat a couple of times b4 it was shrink wrapped & I repeated the above just to make sure they were "topped off" to the full 14.6-14.7V. I'm curious to see what the V readings are in the spring when I "unwrap."
I have also investigated & now fully understand loads connected directly to battys - CO detectors were the worst offenders - I've since ran them through the batty SW - only active when battys are on as only time they are off is when I leave for extended times.
Hope this helps
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Old 03-29-2015, 11:08 AM   #23
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If you use an automotive type charger it is critical to disconnect the battery cables if the boat is in the water. Many of those chargers will connect the AC to ground and may cause stray current corrosion. This does not matter in a car or disconnected battery but with everything hooked up in a boat you don't want AC on the ground system.
If you have an inverter that will use some small current when not powering anything. The best solution si always disconnect the battery terminals for long term storage.
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Old 03-29-2015, 11:27 AM   #24
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Be careful using equalization settings on your charger. Most chargers tell you to only use this setting for flooded batteries. Equalization uses voltages much higher than normal and can cause the electrolyte to boil. Some brands of AGM batteries provide specific instructions for equalization. If your battery brand does not provide this, you might consider not doing it.

What brand are your batteries? What kind of charger do you have?

I think the trick with using a second battery is just using the second battery to convince the charger that it is hooked up to a good battery.
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Old 03-29-2015, 11:30 AM   #25
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Probably best to charge each battery individually.
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Old 03-29-2015, 11:58 AM   #26
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Probably best to charge each battery individually.
For now, this is what I'm doing with terminals disconnected. It's a manual charger set on 2 amps and that seems to be what the first battery is willIng to take. Some long days ahead of me, I suspect.
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Old 03-29-2015, 12:26 PM   #27
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good, let us know how it turns out.
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Old 03-29-2015, 03:59 PM   #28
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If the batteries have been discharged in freezing weather, I would check to be certain they have not froze and split their cases. That may not be visible from the tops if they are in boxes. Don't ask how I know this. At least in my case they were at the end of life anyway. Mine are not AGM's but I can't figure why that would make a difference from a freezing perspective.
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Old 03-29-2015, 06:03 PM   #29
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What brand are your batteries? What kind of charger do you have?
Deka Intimidators. I'm using an automotive manual charger set at 2 amps. The on-board charger is a Xantrex TrueCharge2, which I can't power up since I'm 150 ft from a source.

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good, let us know how it turns out.
Well, I charged one of the 1.9 volt batteries for about 5 hours at 2 amps, checking every 30 min or so. I saw up to 8.49 volts when I took the charger off and called it a day, but it dropped steadily; was at 6.4 a half hour later and still falling.

Still very cold in the engine room today; I'll try again next weekend with a longer charge in hopefully milder weather.

I did look for damage and saw no signs of cracking, etc.

Thanks all.
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Old 03-29-2015, 09:10 PM   #30
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If the batteries have been discharged in freezing weather, I would check to be certain they have not froze and split their cases. That may not be visible from the tops if they are in boxes. Don't ask how I know this. At least in my case they were at the end of life anyway. Mine are not AGM's but I can't figure why that would make a difference from a freezing perspective.

Out of curiosity, at what temp will battery fluids freeze?
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Old 03-30-2015, 02:28 AM   #31
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Angus,
SInce the boat was high and dry those batteries should have been ok. I leave my 12-13 yr Gels for 4 1/2 - 5 months and although the voltage has dropped they are still about 12.6.

Almost All electronics draw current even when 'off'. TVs and stereos the same. CO and Propane sensors draw current. Auto Fire systems may draw current if there are electronics involved. I don't KNOW this since I don't have one but it's likely. Unless they have a true ON/OFF switch there is a small current draw to maintain enough electronic activity to recognize a button push for 'ON'.

I have several pieces of equipment that do the same so I physically disconnect them.

None of these pieces of equipment draw much but add them up and leave them over many months and they will kill a battery bank.

If you have a dicey battery that is developing a low voltage cell , that battery can, if bad enough become a load to the other batteries.

You may or may not be able to save the batteries - good luck to you. You should be able to prevent this from occuring again but absolutely everything must be truly off or disconnected. Some boats are wired so the loads are killed with the battery on/off sw. but some are not and many electronics and such loads actually bypass those switches.

The other way is as suggested - disconnect all the batteries. Just be sure to tie those wire ends in such a way that they cannot touch anything such as a battery terminal.

Your FM radio with preset stations may need to be reprogrammed in spring. Just make a note of the stations.


And check into some of those suggestions like plugging in monthly overnight.
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Old 03-30-2015, 02:46 AM   #32
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Lead acid cells will freeze at different temps depending upon the state of charge so it is hard to answer specifically so here is Trojans chart. A fully charged battery would be tough to freeze but at half charge in many areas of the country a battery could be in trouble.

http://www.trojanbattery.com/pdf/WP_...orage_0512.pdf


http://www.lifelinebatteries.com/manual.pdf Page 22 shows freezing points for Lifeline AGM. It's better but is not immune.
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Old 03-30-2015, 06:32 AM   #33
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Something to consider for next season if you're not able to connect to the AC power source during layup is a 1.5 watt solar panel might keep the batteries up over the winter. A solar panel of this low wattage won't need a charge regulator and can be had for less than $20. I've been using one to maintain a group 31( flooded lead) used to power a pair of electric winches, and so far so good. On an overcasts day, it puts out 20 volts.

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Old 03-30-2015, 06:56 AM   #34
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Thanks, guys. All of the advice here has been very helpful. I'm going to try to consult a Deka tech today and will see what the manufacturer recommends for this specific model.

I'm actually wondering if pulling the four AGMs that perform start/household duty and taking them to a shop for recovery makes sense. The 5th 8A8D AGM only starts the gennie, (which seems like a lot of battery for that job) and seems fine. Getting them tested by a pro and charged with the right equipment might make sense. I can't stay with the boat long enough to do what may be necessary (24-40 hours) and our storage contract ends in about 3 weeks. This way, if they're confirmed to be unrecoverable, I can install new ones.

Lifting those 160-lb beasts out of the boat is going to be fun, too. I love the space it gives me in the ER, but the batteries are outboard of the main engines and not situated for easy removal. PLUS, I have to climb at least a 10-ft ladder to board the boat while it's blocked. .

This is going to be one of those lessons learned the hard way, I'm afraid.
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Old 03-30-2015, 07:24 AM   #35
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The 5th 8A8D AGM only starts the gennie, (which seems like a lot of battery for that job) and seems fine.

Another indicator the other batteries have had a load on, I think.

We use a G34 AGM to start our 8Kw genset (3-cyl. Yanmar diesel), and even that's a bit of overkill.

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Old 03-30-2015, 07:54 AM   #36
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Dont know if AGM will like it but if this were a LA


I would purchase a de sulfation device , and give it time.

If they froze hard and the case is bulged out , they may never recover
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Old 03-30-2015, 09:04 AM   #37
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Lead acid cells will freeze at different temps depending upon the state of charge so it is hard to answer specifically so here is Trojans chart. A fully charged battery would be tough to freeze but at half charge in many areas of the country a battery could be in trouble.

http://www.trojanbattery.com/pdf/WP_...orage_0512.pdf


http://www.lifelinebatteries.com/manual.pdf Page 22 shows freezing points for Lifeline AGM. It's better but is not immune.
when I was a young buck I worked at a Long Island boat yard. The young guys got the job of removing batteries and putting them in the racks for winter charging. Lots of frozen batteries otherwise come spring.

Next winter if at all possible use a different yard and Marina where charging is allowed, just my 2 cents worth.

BTW, be careful, charging a dead battery in a boat is not always fail safe.
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Old 03-30-2015, 09:08 AM   #38
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Originally Posted by C lectric View Post
Lead acid cells will freeze at different temps depending upon the state of charge so it is hard to answer specifically so here is Trojans chart. A fully charged battery would be tough to freeze but at half charge in many areas of the country a battery could be in trouble.

http://www.trojanbattery.com/pdf/WP_...orage_0512.pdf


http://www.lifelinebatteries.com/manual.pdf Page 22 shows freezing points for Lifeline AGM. It's better but is not immune.
Sounds like the moral of the story is if you keep your batteries reasonably charged, they are highly unlikely to freeze. Since it rarely gets freezing temps in south Florida, it is not something I ever thought about but we keep our boat in Michigan. It is in heated storage so not an issue for us but I like being aware of these things.

Thanks for the links!
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Old 03-30-2015, 12:14 PM   #39
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Deka Intimidators. I'm using an automotive manual charger set at 2 amps. The on-board charger is a Xantrex TrueCharge2, which I can't power up since I'm 150 ft from a source.



Well, I charged one of the 1.9 volt batteries for about 5 hours at 2 amps, checking every 30 min or so. I saw up to 8.49 volts when I took the charger off and called it a day, but it dropped steadily; was at 6.4 a half hour later and still falling.

Still very cold in the engine room today; I'll try again next weekend with a longer charge in hopefully milder weather.

I did look for damage and saw no signs of cracking, etc.

Thanks all.
The freeze damage can be internal, this could explain why one of the batteries was down to 1.9v. Considering how low your batteries got, it is possible for them to have frozen at temps in the low teens.

What are the temps now where your boat is? You may not have much success trying to charge a completely discharged battery at winter temps.

I would first try to charge the batteries that were 10 volts. Those might be recoverable. Don't try any of the high voltage (equalizing, recovery) settings that may be on your charger. Those are meant for flooded batteries and should not be tried on an AGM unless you call DEKA and they suggest it. I wouldn't use those setting while the batteries are in the boat either.

DEKA makes a good battery, you may be able to save some of them.

good luck.
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Old 03-30-2015, 03:29 PM   #40
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Thanks again guys. As recommended, I'm going to focus my charging efforts on the two AGMs at 10.5 volts and most likely take the other two to a battery shop for a proper diagnosis.

When I think all this probably could have been avoided . . . My head's really sore from banging it against the wall.
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