While the amount of battery drain from the radio will not be more than a few milliamperes, the problem is that it is a constant drain on the battery, therefore, the dockside charger will be constantly charging the battery(s) to offset the drain. This will ultimately shorten your battery life, but by how much I really don't know.
Originally Posted by KnottyGurl
If your charging system is not automatic from say 10amp to 2 amp auto switching and sensing then upgrading will be a good idea, everything runs from the batterys, lights, radios, stereos so it will always be a draw, if you only need a trikle charge and your delivering a full charge then that could be an issue. If your not in a position to upgrade then turn the charger off during the days your there and back on when you leave so it gets a better cycle.
It is frustrating the amount of misunderstanding I see and come across regarding chargers, but, it is understandable given the buying habits of many sailors when it comes to chargers. Folks tend to put all kinds of thought into "what batteries should I buy"
, threads up the whazooo here about just that but barely ever a thread on how to buy a good charger.
ALL CHARGERS ARE NOT CREATED EQUAL
There is LOTS of junk out there that can kill your batteries.
A good marine charger, emphasis on marine
, should never over charge a battery. It should ideally, at a minimum, have three stages for charging; bulk / constant current, absorption voltage and float voltages. It would preferably have a fourth and fifth stage as well, equalization and cyclic absorption for wet cells to prevent stratification.
Ideally I would LOVE to see every boater buy a battery charger that incorporates a battery temp sensor that mounts directly to the battery but these are pipe dreams. A charge voltage that is correct at 80F will be far to high at 100F and will eventually ruin the bank..
"But my batteries never get above 80F."
Consider the large J boat I worked on last summer who was on his third set of AGM batteries in 4 years. That is over $3400.00 in batteries!!! A $300.00 charger with temp compensation would have gone a long way towards helping the situation.
The batts are behind the stbd settee and under the stbd side nav seat. The hull is flag blue and at mid day the temp inside the battery compartment exceeded 110F, IN MAINE...... His charger was NOT temp compensated....
I am at a loss as to why I see folks spend hundreds, and thousands of dollars, on batteries then try to feed them with the cheapest Wal*Mart, Sears or other "cheap" automotive type of charger, not saying folks here are doing that, but I see it day in day out in the "real world"..
I just had another bank less than 1 year old ruined by a cheap Schumacher Ship-n-Shore charger. I am now at over 5 banks ruined by Schumacher Ship-n-Shore chargers and one of them was a 2k GEL cell bank that was being fed over 15 volts on the GEL SETTING!!!!!!!!!! THESE ARE NOT MARINE CHARGERS despite the glossy marketing...
Decent quality marine chargers will have brand names like; Xantrex, Guest, Newmar, Charles, Pro-Mariner, Sterling, Victron, Mastervolt etc.. They will not have a Die Hard or Schumacher sticker....
A good marine charger will not over charge batteries. It is not the charge current that "over charges", because current is dictated by the battery at a specific voltage. Current acceptance is dictated by the battery not the charger. Chargers don't "force" current into a battery the battery takes what it needs up to what the charger can supply. I have a battery on my bench right now taking less than .04A of charge current at 13.4V. It is being fed by a 40A charger.... The battery only wants .04A to maintain 13.4V so that is what the charger supplies.
What over charges batteries are incorrect voltages held at an incorrect level for too long or at the wrong temperature.. Voltage is pressure so a voltage too high, for too long, will increase the acceptance enough to boil off electrolyte once the batteries have become "full". This is why a float feature, float is a lower maintenance voltage, is very important. A good
charger will remain in float while light loads are used.
Leaving a charger plugged in while away from the boat when it is at a marina is an area I'm not going to get into. Suffice it to say many chargers that fail are caused to fail by the HORRIBLE power available at most marinas. When they fail they can often take out the bank with them thus the charger gets the bad rap not the marina's power supply that caused the whole mess..
I have found that the newer "world voltage" chargers such as the Pro-Mariner Pronautic P and Sterling Pro-Charge Ultra (these are the same charger under different brands developed in partnership) deal with these fluctuating voltages far better than US only voltage chargers. Many brands now offer "world voltage" chargers.
A good charger is money well spent. A cheap charger is most often working against you and will nearly always bite you in the end.
Features worth considering:
*UL 1236 or ABYC Compliant
*Multiple programs for charging
*A user customizable charge program
*Repeat absorption mode (to prevent stratification in wet cells)
*Temp sensing (at the battery not the air around the charger)
*World Voltage capable 90V-260V & 40-80hz
*Warranty - some quality chargers are coming with a 5 year warranty!!