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Author Topic:   Quality Charger for AGM Battery
davej14 posted 05-16-2012 04:32 PM ET (US)   Profile for davej14   Send Email to davej14  
I need to replace my dated 30-year-old Sears battery charger. It still works fine but I have to watch the charge voltage or it will exceed the recommended voltage for my Optima AGM battery. I don't think I want to mount a charger in the boat, I only typically need to charge it after winter storage.

What is a reasonably priced external charger that would safely charge my battery without having to personally monitor the status ?

Jessielove posted 05-16-2012 05:37 PM ET (US)     Profile for Jessielove  Send Email to Jessielove     
How about Optima's AGM battery charger? php?gclid=CLHmp6zhhbACFQlN4AodgFzAkA

jimh posted 05-16-2012 05:50 PM ET (US)     Profile for jimh  Send Email to jimh     
Are you asking about battery chargers that run from 120-VAC?
davej14 posted 05-16-2012 09:40 PM ET (US)     Profile for davej14  Send Email to davej14     
I am looking for a reasonable plug-in-the-wall, 120-VAC-operated battery charger that will work with an AGM style bttery. Ideally I would be able to plug it in and forget about it for a few days without boiling out the electrolyte.

I like everything about the Optima charger but its $199. price. I am looking for something under $100. There are a plethora of them online. I am seeking input from those who have hands on experience.

L H G posted 05-16-2012 10:01 PM ET (US)     Profile for L H G    
I use a simple little solid state Everstart brand trickle charger. No worries at all about overcharging. Keeps batteries full charged, and will bring a completely dead battery up to full charge in a few days. Costs about $25.
jfortson posted 05-17-2012 06:59 AM ET (US)     Profile for jfortson  Send Email to jfortson     
Try and search for agm charger. They have a number of charger/maintainers that can be hooked up and then "forgotten" for a while. I use one on a gold caddie and leave it hooked up 365 days a year and never had a problem.

Since charging time is not a priority, there should be several in your price range. I have found the site to be competitive on battery/charger prices, but once you identify a suitable charger, you could search other sites.

jimh posted 05-17-2012 08:43 AM ET (US)     Profile for jimh  Send Email to jimh     
I use several Promarine battery chargers with AGM batteries. On my bench I have the Promarine Precision Float Charger. It supplies about one Ampere of current and is well regulated for voltage so that it does not boil the electrolyte out of a battery. I would not use it as L H G suggests to routinely restore charge to a deeply discharged battery. It runs rather warm when delivering maximum current, and it will take several days of charging to recharge a typical AGM battery from a boat. If you have a battery with a capacity of 80-Ampere-hour and you charge it at a rate of 1-Ampere, it will take at least 80-hours to recharge the battery. Actually, it will probably take more like 100-hours. That is four days. Even if you have the time, the 1-Ampere float charger is not the best choice because it just runs too warm for me to feel good about leaving it running that long, especially unattended.

In my boat I have a two-bank Promarine charger. It can deliver about 8-amperes, and it can split the charge between two batteries. I have it permanently mounted. The battery charging leads are terminated in ring terminals.

At work I have a three-bank Promarine charger. It keeps a float charge on three or four AGM batteries. It has been running for several years.

The Promarine Precision Float charger is sold with spring-loaded battery terminal clamps.

I'd recommend mounting the AC-powered charger permanently in the boat and wiring it to the battery terminals with ring-terminal connections instead of spring-loaded clamps. This will be more convenient to use.

jimh posted 05-17-2012 01:42 PM ET (US)     Profile for jimh  Send Email to jimh     
The cost of a battery charger tends to be proportional to the current that a charger can deliver. The cost also tends to increase if a charger has a charging algorithm and will alter the charging current and voltage in a programmed manner to best condition the battery. Most modern chargers are reasonably well regulated for voltage. The Promarine Precision Float Charger tops out at voltage that is generally safe for most AGM batteries. You should check the label on your AGM battery. Typically the battery manufacturer will list the recommended maximum float charge voltage for the particular battery. You can compare this with the charger float voltage (if the charger has different phases of charging).
jimh posted 05-17-2012 01:43 PM ET (US)     Profile for jimh  Send Email to jimh     
I forgot to mention prices:

1-Ampere Precision Float Charger is about $40

8-Ampere two-bank charger is about $100

15-Ampere three bank charger is about $150.

These are designed to be permanently connected, except for the Precision Float charger which can be bought with either clamps or ring terminals. If you want a carry-around charger, look under automotive chargers. Marine chargers will tend to be for permanent installations.

jimh posted 05-17-2012 02:17 PM ET (US)     Profile for jimh  Send Email to jimh     
If you buy a nice carry-around charger, when you need it for the boat you will find out that your neighbor or your brother-in-law borrowed it last weekend and has not returned it.

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