Lesson learned about AGM batteries...

[Cray Paper]

When I bought my boat it had 3 Optima Blue Tops in it and I thought no matter what I wouldn't have battery issues. Every time the boat was parked at home I put Battery Tenders on the batteries and thought it should be no problem to get them to recharge. I think they were low on charge when I picked the boat up but worked. Last spring I decided to replace the 3 with 2 new Blue Tops as they didn't seem to hold a charge very well and were 13 years old. We got careless last year and for several reasons the tenders were not plugged in, or were plugged in later after the batteries had discharged.

The last time I used the boat last year one of the batteries was dead so I pulled one out of our travel trailer and it did fine, swapped it out before putting the boat to sleep for winter and put the trickle charger tender on it. At some point during the spring the cord was unplugged so neither battery was being charged. So I now just catching up on this and now understand the issues with trying to recharge dead AGM batteries. I had to bad a new blue top to get the hatch open and start the engine to de winterize. Now I am trying to resurrect the 2 dead 1 year old blue tops. I am using my dads Snap On charger, connected one the dead batteries to the battery in my work truck with jumper cables and hooked the charger to the dead blue top. The blue top had 2.5V when I started, after 1.8 hours it was up to 10.8 volts. I hooked another AGM specific charger to the 1st dead blue top and unhooked the jumpers from the good battery.

I then hooked up the other dead Blue Top (8.9V status) and connected the jumper cable to good truck battery and Snap On charger to dead Blue Top terminals.

Anyone else done this before? Taking a severely discharged AGM and charging it back to normal? I've seen some people say to draw the undercharged AGM back down to nothing and start over and keep repeating until it reaches 12.6V. What is the easiest way of drawing the battery down? I dont have many things that clip on to a battery other than portable air compressors, will that work?

 

[ToMorrow44]

Yep I did this with a friends Blue Tops that got left on and run all the way down. You have to trickle charge AGM batteries, if you throw 10 or 15 amps at it like a lead acid, you'll fry them. My Schumacher charger has an AGM setting, charges at ~2amps. It took ~30hours of charging to bring the batteries back to 100%.

BTW if your batteries are running down over the winter, then theres some sort of draw on them (something is wired directly to them). I have never put a charger on my blue tops, just turn the battery switch off, sits for months, turn the switch on and good to go.

 

[LargeOrangeFont]

That is not an AGM problem so much as it is a Optima problem. Optimas suck.

 

[mjc]

Yep I did this with a friends Blue Tops that got left on and run all the way down. You have to trickle charge AGM batteries, if you throw 10 or 15 amps at it like a lead acid, you'll fry them. My Schumacher charger has an AGM setting, charges at ~2amps. It took ~30hours of charging to bring the batteries back to 100%.

BTW if your batteries are running down over the winter, then theres some sort of draw on them (something is wired directly to them). I have never put a charger on my blue tops, just turn the battery switch off, sits for months, turn the switch on and good to go.

Same here I have never charged any battery in any of my boats. i don't understand why so many people have to have on board chargers and trickle chargers?

 

[LargeOrangeFont]

Same here I have never charged any battery in any of my boats. i don't understand why so many people have to have on board chargers and trickle chargers?

You'll typically get another couple years or more with a tender on the batteries. For people that launch and go directly to the channel and sit all day, they may not even get a good charge on the batteries.

 

[renodaytona]

I use a no name brand 1.5 trickle charger on mine. I have two blue tops that are 14 years old and I'm able to get them to 13.8 volts with that charger after a few days. Needless to say that I always plan ahead when I need to get them charged up.

 

[SJP]

Same here I have never charged any battery in any of my boats. i don't understand why so many people have to have on board chargers and trickle chargers?

Do you store any of your boats in LHC year round? Without a trickle charge no batteries last out there in anything.

 

[LHC Kirby]

I talked with the Optima guy up in Reno at Hot August Nights - out in parking lot they had a booth - Atlantis Hotel.

I told him that ever since they went to Mexico that their batteries have been crap. He said, that the batteries are getting better - his tone was "ah shit - someone who knows about our shitty batteries"

 

[96motorhead]

Interstate told me that agm batteries are not as resilient as lead/acid batteries. He told me when an agm is fully discharged they are more difficult to revive. This is why I do not use agm batteries.

 

[rvrrun]

Same here I have never charged any battery in any of my boats. i don't understand why so many people have to have on board chargers and trickle chargers?

Because any parasitic drain will drop the battery voltage enough to cause dendrite growth ultimately rendering the battery useless.

 

[mjc]

Do you store any of your boats in LHC year round? Without a trickle charge no batteries last out there in anything.

Yes they are in Havasu. I had a walmart battery in my K5 blazer that was parked outside and the battery lasted 9 years out there. Last boat battery lasted 5 years never had a charger on them.

 

[lbhsbz]

That is not an AGM problem so much as it is a Optima problem. Optimas suck.

Agreed.

I've been using nothing but Deka (east penn) for the last 5 years or so and have been very happy...seems everything else moved to production to Mexico and they all suck.

 

[McKay]

I have had good luck with the CTEK 56-674 to revive AGM batteries. (I leave one on my boat plugged in.)
What happens is the sulfate if left dead for two long. Takes a special charger to shock them back to life. It hits them with pulses of higher voltage to recover them.

 

[FreeBird236]

Even with my battery switch off, I can still raise the drive, I understand many boats are wired this way.

Conventional battery fan here.

 

[Bobby V]

That is not an AGM problem so much as it is a Optima problem. Optimas suck.

I usually get at least 6-7 years on optimas using a tender. :thumbsup

 

[FreeBird236]

Just changed the batteries in my 08 this year (10th season), still fine but I was starting to worry. Replaced the conventional marine Centennials with the same.:thumbsup

 

[Rsqfxr]

I run 3 odysseys and a 40 amp onboard charger

 

[LargeOrangeFont]

I usually get at least 6-7 years on optimas using a tender. :thumbsup

I'd wager you'd get half that or less without a tender. My buddy got less than 3 years out of them without a tender, twice. His boat was stored in OC too.

I'm on year 3 of Duralast deep cycles with a tender.

 

[fishing fool]

I've learned that the cost $$$. Wet acid batteries has as much or more reserve and can last for years if taken care of.

 

[ToMorrow44]

I had a pair of Optimas that were over 10 years old. They got a little tired, they would start the boat just fine, but it would shut off my GPS which was annoying, so I put a new pair in. Year 3 with those and a charger has never touched them. I actually kept the old ones, I use them as a shop battery. Not sure why you guys are having such a hard time with them.

 

[ToMorrow44]

Even with my battery switch off, I can still raise the drive, I understand many boats are wired this way.

Conventional battery fan here.

Yeah, so theres a circuit thats wired directly to the battery and not to the common terminal on the Perko switch. I know some did that with the hatch as the Perko was under the hatch. There may be other things wired to that circuit too that slowly drain the batteries over time. Mine with the switch off, nothing works, equivalent of disconnecting the battery cables.

 

[fishing fool]

I had a pair of Optimas that were over 10 years old. They got a little tired, they would start the boat just fine, but it would shut off my GPS which was annoying, so I put a new pair in. Year 3 with those and a charger has never touched them. I actually kept the old ones, I use them as a shop battery. Not sure why you guys are having such a hard time with them.

I think it depends on the electronics (stereo) you have in your boat. If you have a lot of stereo then the alternator may not recharge the batteries back up. This is why a battery charger is needed.
I know before I moved to Havasu I may not use the boat for a month or maybe more (kind of like milkmoney) and just the memory for the radio would drain the battery.

 

[Bobby V]

I'd wager you'd get half that or less without a tender. My buddy got less than 3 years out of them without a tender, twice. His boat was stored in OC too.

I'm on year 3 of Duralast deep cycles with a tender.

My boat is a 98'. Always used Optimas with 6-7 years of life. I didn't start using a tender until a few years ago.

 

[EmpirE231]

I had one yellow top optima in my sandcar when I bought it. It was deeply discharged... did that charge setup where you connect it to another battery & a charger... went back to normal, and lasted another 5 years or so until I sold it.

 

[LargeOrangeFont]

My boat is a 98'. Always used Optimas with 6-7 years of life. I didn't start using a tender until a few years ago.

Failure rate seems to have gone up dramatically in the last several years. Are you seeing a better life of yours since using a tender?

 

[Waterjunky]

I use deep cycle batteries on my projects here at work. All my projects are strictly solar powered. At this point I have crossed everything over to AGM batteries. I think there are a few misconceptions floating around here. Something to keep in mind is that there are different qualities of batteries in the market. Price is not necessary the best judge of quality, blue top Optima being a good example of this. Before making the swap, I was using standard flooded wet cell batteries on all my projects and had an average life expectancy of somewhere around 18 months. Since I swapped to a premium AGM I have not had a single battery die in the last three years. I have around 25 of them going. Not one has died! One of the advantages of a "good" AGM is charge rate. it was mentioned earlier that you needed to only trickle charge them. Not so much.... you need to watch your voltage and not burn them up but you really pour the amps to them and they just soak it up like a sponge. Now of course this works well up to a point, you get too far past 90% charged and you better taper off but that is no different than a normal batter. My point is that you can recover the center portion of your charge curve several times faster than a conventional battery. Like with any battery rapid charging cycles are harder than slow trickle charging but you can still do it if needed. an additional advantage is regarding depth of discharge. AGM's are a little more forgiving of deep cycles than a conventional flooded battery. You can still damage them by doing it, no battery likes complete discharges......... As a last benefit, most (not all so don't go doing anything stupid without checking into it....) AMG's are fully sealed meaning you can mount them in odd locations and out of position. When space becomes a premium, this gets more and more important. Even sealed traditional batteries need to be kept upright.

There is a lot of miss information and wives tales regarding batteries of all types our there so, take everything I have said for exactly what you paid for it. Just a few details that I have learned working on research projects with 12v power systems.