Wet (lead acid) batteries and corrosion from gassing

[firehoser75]

My new to me boat (powerboat) currently has AGM batteries including 6 golf cart style batteries for the house bank. My charging system separately charges (using 2 different shore chargers) my start and bow thruster batteries (with one charger) and my house bank with the second (inverter) charger. I have recently added solar charging only for the house bank. I also have a Balmar Smart Gauge installed. The only time all of the batteries are charged together is when the engine alternator is doing the work and as it is the stock alt it does a poor job of charging the house bank.
I think that the house bank is not far off needing replacement, but the other batteries seem to be in good shape. As AGM's are almost 3 times the cost of flooded lead acid, are there any reasons why I shouldn't switch to lead acid? The house bank is located in the engine room (and are easily accessed for maintenance) where I also have 1 battery charger, 1 inverter/charger, a solar controller, a on board generator and other electrical connections,fuses, etc. The engine room size is about 500 cubic feet and has 4 vents that are about 2 feet by 8 inches each.
Would corrosion from gassing caused by charging and equalizing wet acid batteries be a concern or reason to stay with AGM? Have you heard of an "oil product" to add to the electolyte (floats on top and supposedly greatly reduces the gassing) and any comments as to the effectiveness of this and/or problems with this idea?
Thanks in advance for your comments, opinions and suggestions!
Merry Christmas and Best of the Season to everyone,
Tom

 

[justsomeguy]

Would corrosion from gassing caused by charging and equalizing wet acid batteries be a concern or reason to stay with AGM?

No, sounds like you have plenty of ventilation.

Have you heard of an "oil product" to add to the electolyte (floats on top and supposedly greatly reduces the gassing) and any comments as to the effectiveness of this and/or problems with this idea?

Yes. It's supposed to reduce evaporation and boil-off. It's snake oil.

 

[SG]

I'll be difficult -- answer about corrosion: I think if you're concerned, yes is the answer. You have to put these batteries in proper battery box if you go to wet cell lead acid technology. IF YOUR HOUSEBANK is in the engine compartment, you'll have hot batteries if you're motoring. I don't like that much. You're asking for trouble.

My view is that you must have a lot more ventilation and be concerned with wet cells; You HAVE TO HAVE PROPER battery boxes and containment for the.

Gel Cells need ventilation too -- but not very much. You MIGHT get by without a boxes -- but you shouldn't be putting batteries in an engine compartment.

AGM's don't need battery boxes -- but I wouldn't put them in an engine compartment.

 

[JimInPB]

AGMs generally let you bulk charge them faster than traditional flooded batteries, but if you don't charge the AGMs with the correct type of charger, they suffer pretty badly & can degrade rapidly. I don't need the fast charge characteristics of AGMs. I do just fine with old fashioned (more bang for the buck) flooded batteries.

The other nice thing about AGMs is that they don't spill acid when tipped on their sides. Depending on how your boat is used & what conditions you take it out in, this may or may not be an issue. I do fine keeping my flooded batteries in a plastic battery box that is properly strapped down. Your needs may vary.

Main Sail has posted a fabulous library of information on the various batteries that are out there, the perks of each, & their proper care. If you have some time to sit down & do some reading, his posts are probably the best source of information you will find.

 

[gettinthere]

if you can get the house bank out of the engine room, that would be good for the life of the batteries regardless of type. Also good for the electronics. My Balmar ARS5 voltage regulator started acting up and the first thing Balmar asked was whether it was in the engine room. It was. The heat caused expansion which cracked the epoxy many of their parts are set in. I relocated the new voltage regulator outside the engine room and all is good.

my flooded wet cells are in a compartment with the steering quadrant and over the last 10 years I see no corrosion on metals of any kind. And further, this setup has been in place since 1985 and I see no issues from wet cell gassing.

 

[Benny17441]

Just look at the features that the AGM batteries have over the wet cells type and make your decision based on whether you need any of those features or not.

 

[jeepbluetj]

Water miser caps can reduce offgassing. Most importantly, properly charged FLAs don't offgas that much anyway. Overcharging them causes much offgassing.

I'm a huge fan of cheap GC2 batteries for the house bank. Most boaters can't/don't take care of AGMs enough to see any benefit from them, particularly not when accounting for cost. Sams/Costco have GC2s for around $80. A local golf car place may be close in price with better batteries (Trojans).

As others mentioned, having the batteries in the engine compartment can be bad with all the heat. But that's the same for any kind of battery - so FLAs win there too 'cause you're killing cheaper batteries with the heat. You may be able to temper the heat issue with where your intake air comes from, running a blower, etc...

 

[firehoser75]

Thanks everyone for taking the time to respond. I really don't have any other location where I could accommodate 6 golf cart batteries, so they will have to stay in the ER. I was mostly concerned about the potential for wet cells to off gas and potentially cause some early corrosion issues, especially in the electrical/electronics that are in the engine room. On my former boat, the sailboat, it's house bank was located in the salon under the seatee and in 11 years with lead acid batteries, I never noticed any corrosion issues but I thought I would seek the experiences of others. Since the lead acid batteries are so much less expensive than quality AGM's , I think it would be better cost wise to go the wet cell route and replace more often if needed. My charging system is pretty good and is temperature compensated, with the exception of the stock alternator that seems to only really keep the start and bow thruster batteries up and only provides a small amount to the house.
I only recently heard about the oil additive, so was also looking for any first hand experience or knowledge. I suspected the "snake oil" idea.
Thanks again,
Tom