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gwp 05-05-2004 06:56 PM

Battery Charging Question
My Oday 25 came with a small (~4"x6") battery charger which remains permanently connected to the battery. It claims to be "fully automatic". One year ago, I bought a new marine battery (nothing extraordinary, just a $50 marine battery) and it is now dead, or at least a few cells are dead. The charger is always hot to the touch even when there has been no load on the battery. When I leave the boat, I always turn the battery selector switch to "off", but the charger is still always hot when I return. I know this is very limited info, but......Questions:
Should I expect a battery to last longer than one year?
Is this a cheap unreliable charger which has burned up my battery prematurely?

GordMay 05-06-2004 12:21 AM

Battery Charging Question
Yes, to both queries.

Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float.

Bulk Charge The first stage of 3-stage battery charging. Current is sent to batteries at the maximum rate they will accept while voltage rises to full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. Most garage and consumer type battery chargers are bulk charge only.

Absorption Charge The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.4 to 15.5 volts.

Float Charge The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it''s main purpose is to keep an already charged battery from discharging. Voltages at this stage are typically 13.2 to 13.6 volts.

Tell us more about your energy consumption & boat use; and we can offer a little advice. Obviously, better chargers & batteries cost more - so you have to match your technological investment to your requirements.


gwp 05-06-2004 06:02 PM

Battery Charging Question
Gordmay, Thanks for the info. I guess I assumed that my "fully automatic" charger did more than pump 12 volts 24/7. That''s what I get for assuming. My boat is on shore power always except during the few hours I''m sailing each week, and the charger is permanently connected. When I bought the boat, it came with the small charger I mentioned earlier, and a larger charger which wasn''t connected. Here is the larger one which I brought home to use:

Is this charger a 3 stage charger? I will try to find the paperwork on it and learn more. Perhaps I should take this one aboard and use it on my new battery. Many thanks to you......Gary

e-27 sailor 05-06-2004 09:02 PM

Battery Charging Question
I think there are a few different issues here. 1st, think about how much you really use or need your battery. If you''re a day sailor, you might need it for running lights about once or twice a year. A hand-held VHF solves your comm problems. 2nd, small batteries only need small (6-10 amp) chargers. I have a group 27, 85 A/H battery, and it only takes about an hour to charge it up. You might want to invest in a Guest, 3 stage charger, and plug it in as you''re preping the boat, and/or while putting her away. You can go about 4 weeks between charges. My guess is you might have boiled off the electrolite in both your other batteries by leaving the big charger connected full time. And last, you can''t expect a $50 battery last too long.

GordMay 05-07-2004 01:33 AM

Battery Charging Question
The pictured Sears "Fully-Automatic" charger is not a 3-Stage unit. It''s a fast charger that throttles back to a "trickle charge". There are some different strategies for sensing the voltage at which to throttle back. I''m not certain which this unit uses - but I would NOT recommend leaving this charger permanently connected (there are a number of imortant reasons) !!!
The best Chargers cost over $250 (up to $400); but there are cheaper alternatives that would seem to match your fairly limited demands:
BoatUS currently has a “special” Sale ($29.99) on the Guest Charge-Pro
Charge Pro Portable Battery Chargers
This handy, portable, three-stage electronic charger features built-in thermal and overload protection, reverse polarity protection and LED ready indicators, so you''ll know when you''re ready to roll. The unit comes prewired with a 6 ft. AC cord and 4 ft. DC outputs.
You could permanently wire this unit (/w a breaker or fuse).

gwp 05-07-2004 03:50 AM

Battery Charging Question
Thanks, I feel more comfortable having power on my auto bilge switch all the time. Otherwise, I''d probably just charge prior to going out. I''ll pick up this Guest charger. That sounds like it will suite my purpose. Thanks for the education.....Gary

Nereus32 05-07-2004 11:28 PM

Battery Charging Question
I always like to point to It is full of info on deep cycle batteries, charging routines, and charging technologies. Lots of information that is really educational regarding the deep cycle battery we all love so much, yet don''t really understand.

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