Flooded Vs. AGM's

It's about time to pick up some batteries for my 27' Silverton restoration. I'm in the process of finishing up the wiring, getting ready for spring. The question concerns which type of batteries to install. I'll have a house bank and a starting battery. The original boat had the batteries located in the engine compartment. I didn't like that set up due to heat and long cable runs. So, I moved the battery's to a location under the cabin sole, in the bilge area adjacent to the engine compartment. Of course the batteries will be installed up and out of any bilge water. With the batteries inside the boat (where I will be spending some time), I'm wondering weather I should be concerned with gasses venting from flooded batteries.

I'm considering a couple of Trojan T-105's or T-125's (6 volt's wired in series to make 12 volts) and an appropriate flooded battery for starting.

If I go AGM I can pick up a single 12 volt house battery and a smaller starting AGM with comparable 20 hour rates (around 230 AH for the house bank) but they get really expensive.

So, should I worry about flooded batteries inside the boat or not?

I've installed the following:

Xantrax Truecharge 40 charger
Xantrax Pro Series 1800 watt inverter

This system is probably a little robust for a 27 footer. When I designed it I decided to go to the upper end of my power requirements. I'm pretty anal about maintenance so checking up on flooded batteries isn't a problem, the charger has an equalization program as well.

Thanks in advance for any advise you might have,

Missinginaction

 

Your battery banks are small, so either is a good choice.



Lead acid are cheap and cheerful.. Ive used them for many years. When fitted with hydrcaps water loss is minimized.

Presently I prefer Gel batteries.

Gels give good service life. large banks are easier to install. and rewatering off season is eliminated

I have no experience with absorbed glass mat. They look expensive.

With all batteries the battery charger is the issue. Ive never met a battery charger that I like. Overcharging is the problem.

A separte trickle charger, located at or very close to the bank, for off season charging is recomended.

 

I went for AGM because I got a great deal.

If you stay on top of water levels you'll be okay.

AGM are more forgiving to misuse.

I'd let the $$$ decide.

 

Thanks for the input guys. I'm leaning towards the Trojans. I use AGM's in our cars but for the boat it seems cheaper per AH to use flooded lead acid.

Regards,

MIA

 

You certainly will be happy with the Trojans, I use them exclusively when going wet.

 

I have been cruising with AGM batteries for 4 years and have had no problems, the starting battery was installed prior to 2007 and is still working fine, I installed 3 new house AGM's in 2009 ,and they are also performing well. I have 5 solar pannels and 1 wind generator, set point for solar charger regulator is 14.3 volts. AGM's can take a hard charge....seems to love it.

 

AGM advantages ("misuse tolerance"): high rates of charge and discharge, very low self-discharge rate (a fully charged battery can sit for months without getting discharged and damaged). A BIG AGM drawback: Severe overcharging will kill them quickly. They'll vent gas, and they cannot be refilled. The same is true for gel batteries. In that sense, flooded batteries are MORE forgiving.

Flooded batteries will vent ONLY when being charged. So if you charge during the day, when there's enough ventilation, you should be ok.

If you go with AGMs, the original Lifeline brand made by Concorde is much better than no-name products sold by West Marine etc. I've seen tests where the no-name thing had half the advertised capacity or less!

Gerold

PS: I've been using a Lifeline AGM since 2001 on my small sailboat with an electric motor, and I've recently bought Trojan TE-35 6 volt batteries for our powerboat project.

 

I try and keep my charge levels at about 80 to 85% and never take a deep discharge even if it means running the diesel which only happens when there is no sun for several days. I don't have a gen set aboard, chose not to. I can charge 18 plus amps from solar alone not including the wind gen. I tested this system before leaving the dock, unpluged the line cord and just used solar and wind for 6 months so when I left the dock there was no change in performance. I can run my watermaker, refrigerator, radios etc., and still charge the batteries at 5 amps or so. Only need to run the watermaker about 8 hours out of 10 to 12 days The secret is running the equipment at the right time of day "power management". I also have a 1k pure sine wave inverter for running small power toolls,laptops,soldering irons,routers etc. don't use tools much though. Hopefully the tech community will have developed a Lithium type of battery of proven quality and safety for a reasonable price before my AGM's go south. As it is now you need to rob a bank to get 425 amps Lithium batteries!

Cherers,
Don

 

Whoa !!!...18 amps from the sun...you have a lot of solar panels

 

I have 5 solar panels, 4 are articulated and 1 stationary. I have a very low carbon foot print, which was what I was looking for and only spend about $350 a year on deisel which is mostly used for motoring when there is no wind. I do use some gasoline for my dinghy outboard(2 hp), think it was around 20 to 30 dollars last year.

Cheers,
Don

 

Thanks again for the good info gentleman, I appreciate it.

MIA

 

Frankly I prefer flooded batteries. They are inexpensive compared to Gel and AGM, and if properly maintained last 5-7 years. That means using a good three or four stage charger, checking fluid levels regularly, and never letting them go below 50% discharge. As was said the charger is the critical item. You can cook any type of battery with the wrong charger. The one you have appears to fit the bill.

I would be concerned about ventilation for the batteries. Ventilation is required for all three types. Even AGM and Gel batteries will discharge if over heated (which means overcharged) There have been a few dramatic explosions with Gels although I haven't heard of anyone being killed.

Oh yeah, if you use flooded batteries get yourself a good professional grade hydrometer that is temperature corrected. Those cheap ones are highly inaccurate.

 

In my re-power and refit I have sold an as-new bank of 6V 242AH golf cart batteries inherited from the PO, total capacity 1452 AH at 12v. Instead I am using a slightly smaller bank of Odyssey PC 1800 AGM. They cost plenty, but I got a very good deal on them.

Reasoning involved several aspects.

I have 2 new diesel engines with a true 200 Amp large frame alternator on each. Flooded cells could not take these charge rates. I will also have around 1500W solar. I have removed two generators, and am not going to put one back in. The two main engines are my genny...

The footprint of the Odyssey's is so different to the normal battery that it was better to do it during the current engine room remodeling than have to configure new cabling later.

Part of the appeal of AGM is a deeper level of discharge, so my effective or useable capacity might even be a bit higher than before.

Whatever you do, go for a quality charger. Make sure that the latest Xantrex is up to snuff - some of their older units weren't the best. Add temperature monitor and charge control capability if not part of their normal setup. You should avoid overheating of any battery - having good airflow for cooling during charging is easier around an AGM as you don't have to have a box to manage the mess flooded cells can make. A tray will suffice for an AGM.

For the PO, consider fitting a high capacity alternator to your diesel engine as part of the whole system rebuild. Depending on how big this alternator is, you may find it worthwhile to go the route I did. Even one PC 1800 gives you a lot of useable AH. Since they can deliver both good cranking capability as well as deep cycle, you can use the same type of battery for house and start. This makes charge management more simple. Then rotate them periodically. Ie have one Odyssey (maybe a smaller capacity than the PC1800 in your case) as start, and 2 as house, all the same model. Every six months do a rotation of duty for the start duty.

 

My house battery bank, four 6 volt lead acid batteries, is located inside my cabin and I have not noticed any problems with venting. I have had good luck with the 6 volt golf cart batteries from costco. With proper care they last 5 to 6 years. I think that having just two 6 volt batteries will be marginal. Just because you have a 27 foot boat doesn't mean that you will use less electricity. Do a realistic survey of all your electronics and I think that you may be surprised at just how much electricity you will use every day when you are away from the dock. Charging batteries with your engine is a pain and hard on the engine. I have 4 solar panels totaling 260 watts. Peak charge amperage is just over 15 amps and 10 to 12 amps is pretty typical during the middle of the day. I have not had to use my engine for charging since installing my solar panels several years ago.
Good luck with your project.

 

Thanks guys. Hygrometer, check.

I like the idea of the battery rotation that Brian mentioned. I'm leaning towards golf cart 6 volt batteries similar to what Chuck suggested.

As far as the size of the house bank is concerned, I agree that a couple of 6 volt Trojan T125's might be insufficient. There is plenty of room in the battery compartment (it formerly held a 20 gallon freshwater tank and had room to spare). I thought I'd install two of the Trojan's for the first season as I'm not planning on going too far. If they're not enough I can easily add a couple of additional batteries in the future.

Keep in mind that this is a restored 27' Silverton (73) single, gas using a small Ford V8 (302). Intended use is mostly days, weekends and an occasional longer trip.

Regards, MIA