Free up valuable storage and AGM advantage

[Catigale]

Can anyone speak to how AGMs fare to cold weather??

I dont kill batteries with discharges in use...I end up leaving them on the boat in winter and they freeze...that kills them pretty quicky I have found.

I killed both of mine two winters ago and have been limping with about 10% capacity on both house and motor battery....combination of shore power at slip, yelling at anyone who leaves a light on, and using rechargeable flashlight at night...

Ill break down next spring and buy two new ones of as-of-yet-undertermined type....

[Chip Hindes]

I dont kill batteries with discharges in use...I end up leaving them on the boat in winter and they freeze...that kills them pretty quicky I have found.

Fully charged batteries are good to at least -40. Only discharged batteries freeze. I assume both types are equally susceptible if left discharged.

I keep power to the boat and the automatic charger on all winter; and it keeps the wet cells topped up fine. If you can't do this, you need to top them off on a standard charger at least once per month.

AGMs have a much lower self discharge rate and should be good through the winter, so if you can't keep the wets charged up they would be a better choice. You might want to pull the negative cable just in case there's some residual draw; I know for instance my stereo has a constant low draw to maintain the clock time and radio station memory. I'm assuming it's only a few ma but I've never measured it.

[Hamin' X]

When they do give up the ghost I will replace them with a pair of 6V GC2 golf cart batteries. They have 215Ah and when wired in series will give me all the power I would ever need.

Just a note on battery capacity ratings. Different battery chemistries react to different discharge rates differently. Capacity ratings have more factors to them than just AH rate. You must also know, the temperature of the rating, the duration of the discharge and the number of cycles. Golf cart batteries are designed for medium discharge rates of short duration over a lot of cycles. I think that you will find that for light marine/RV use, that golf cart batteries will have about 1/2 of their stated AH capacity, because you are loading them less over a longer period of time.

[Tom Spohn]

I am with Duane and Chip on this one. We are using two 6 volt batteries wired in series and even with microwave, computer, video, radio, etc. on the inverter we don't even come close to zapping them.

FWIW Blue Water is using the Dyno 6 volt batteries. Depending on the model you choose your GC2 can have up to 245 AmpHr.

http://www.dynobattery.com/prod01.htm

[Hamin' X]

[/quote]FWIW Blue Water is using the Dyno 6 volt batteries. Depending on the model you choose your GC2 can have up to 245 AmpHr.


I looked up your battery on the website given. Not much in the way of real specs, but it does say that the 245 AH rating is a 20 Hr rating. That is over 12 Amps draw average for 20 Hrs! By the time you reduce that draw to a reasonable load for the average boat (I don't have any real world figures of my own), say 4-5 Amps, you will stretch out the discharge time to 50-60 Hrs. Very few battery sellers give all of the specs needed to make a reasoned choice. Here is an honest one---

http://www.kingsolar.com/catalog/mfg/exide/e3600.html

It is my understanding that the AGM batteries don't have this problem, but I would have to research further.

[Frank C]

If you are looking for AGM batteries try Gruber Power Services. They are my main battery supplier that I use for the power wheelchairs and scooters that I sell. The batteries are foreign made, a lot less expensive, and they last as long as the domestic ones ...Jeff

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Group 27,  75 AH   11"  7"  10"    53 lb   $  70  1 year full
Group ??, 103 AH   13"  7"   8"    83 lb   $ 156  3 year full
Group 31, 110 AH   13"  7"  10"    84 lb   $  89  1 year full

Great link HamminX, to Kingsolar for golf cart batteries ... I searched to no avail for prices after reading Tom's post about 6 volt batts. However, two of those sixers (cost $120 plus s&h) versus two of the AGMs provide the same 220 ampHrs (cost $180), about a 50% premium for the AGM over the 6 volt wet cells.

Since Jeff is using the AGMs for wheelchairs, I have to believe that they're a "durable" replacement for the six-volters. More importantly, they also permit the boatowner to forget about replenishing water, ignore the potential of upending them on heel (or worse), and forget about solar or trickle maintenance crap. Since my boat is, after all, a sailboat ... and it sits idly for long weeks in a dry-store trailer lot ... those are compelling benefits, IMO, for that extra sixty bucks. Sure hope that Group 31 fits under my aft-galley seat. I'll let you know how I like the AGMs next season.