Battery Tender ?

[bondobill]

Is there any problems with leaving a battery on while the boat is moored and having a battery tender hooked up to the battery ?
I need to leave one battery on to run the bilge pump/ float switch while the boat is moored,
The slip has shore power.

I have a chance to get free moorage this winter at the marina where I launch my boat.
Leaving the boat in the water would make it whole lot easier getting out fishing, and hopefully a lot more often.  

Bilge pump/float switch is not wired directly to the battery.  :(

I have a Deltran 12V 1,25 amp battery tender I am hoping would do the job

[CLM65]

As long as the charger automatically drops to a trickle charge when it senses the battery is full, you should be fine.  I keep a Guest charger on mine all the time, and haven't have a problem with it.  Can't speak for your specific charger though....

[Capt. Bob]

Agreed.

Let's say this is what you have.
http://www.batterytender.com/Automotive ... -Plus.html

This style charger states it will remain in a float mode (maintenance) as long as it sensing voltage at a certain level. When the voltage drops below that level, it goes into a "charge mode". This is a typical algorithm for smart charging technology these days so.....

Boat's in the water.
No rain in site.
Minimal/no drain on battery (float switch in off position).  
Battery at full charge.
Charger in float/maintenance mode.

Big rain comes.
Bilge fills.
Float switch "floats".
Bilge pump runs controlling/emptying bilge.
Battery voltage level drops.
Charger goes in "charge mode".

Rain stops and sun/moon comes out.
Pump drains bilge, float switch no longer floats.
Current draw stops and charger continues to charge.

Battery voltage level is reached that changes charging mode eventually reaching the float stage. Cycle complete.

As Craig stated, if it's a smart charger, you should be fine. The fact that the battery is "switched on" isn't a problem. Even with a parasitic drain, the charger will sense the voltage drop at the programed level and begin doing its thing. Makes no difference if it's gradual or over a relatively short period of time.

Good luck.

[wingtime]

IMHO the Battery Tender brand is best option out there for maintaining your batteries.  They have a unit that is made for marine use.  I have them on my other toys such as my Jeeps or motorcycles.  Before I bought a battery tender I was replacing batteries once a year... after..  once ever several years.

[RickK]

Bruce I went to their site and they really don't have any technical data on lead acid vs gel or AGM.  Every other Mfr talks about all of that.  Is the Battery Tender only for lead acid type batteries?

[wingtime]

Bruce I went to their site and they really don't have any technical data on lead acid vs gel or AGM.  Every other Mfr talks about all of that.  Is the Battery Tender only for lead acid type batteries?

Not really sure...  I used one on a AGM battery in my plane with good results.  My buddy has a 67 GTO and he kept going thru batteries from it sitting...  I gave him one of the basic Battery Tenders...  no more bad batteries.

[bondobill]

Here's what I have found on the Battery tender I have

•Perfect for all lead-acid, flooded or sealed maintenance free batteries (AGM and gel cell).
•Complete 4-step charging program (initialization, bulk charge, absorption mode and float mode).
•Automatically switches to float / maintenance voltage after fully charging the battery.
•If the battery voltage drops too far under load, full charger output power resumes.
•Temperature compensated to ensure optimum charge voltage according to ambient temperature.
•Solid state two color LED indicates stage of charger.
•Spark proof and reverse polarity protected.

I have 2 Optima batteries in the boat.  One yellow top and the other blue top, both AGM type
I should be good to go... right ?  

[RickK]

Thanks for the info Bill. If the batteries are still working and holding a charge I would say yes.  
It is weird that they don't mention the types of batteries that they are good for on their site except Lead Acid. Most other mfr go out of their way to talk about the battery types and how their product takes care of them.  
Merry Christmas.

[seabob4]

While I would imagine ALL chargers (short of the cheapest POC you can buy) will cut output once a charge state has been achieved, one does have to pay attention if one is using gel-cell batts.  Gel-cells cannot take the higher voltage output of a typical charger when in the bulk charging state.  While gel-cells aren't widely used, it is something to consider.

AGM and lead-acid can be charged the same...

[Capt. Bob]

The key (as Rick stated) is that you keep the AGM batteries in a "minimum charged" state. I can't recall what voltage is considered " minimum charged" for an AGM but some smart chargers cannot bring an AGM back once it falls below this minimum voltage. Once the voltage drops below a certain level (let's use 7 volts for an example, though it may be more or less) the AGM (gels also) require a boosting charge to get them above that (7 volt) threshold which then triggers the programed algorithm for that brand charger. Older smart chargers (and many new) can't do this and the battery will then not take a charge.

http://www.hotrod.com/how-to/interior-e ... m-battery/

Optimas are known for this behavior (though it is an AGM trait) and the company now markets their brand name charger for them. It is costly in comparison to other smart chargers but it does work.

http://www.optimabatteries.com/en-us/sh ... ital-1200/

The real key is not to let the battery voltage drop that low to begin with but....

Age of both the battery and its owner can lead to this state.

Sounds like you're in good shape so enjoy........

PS..... This is gleaned from their site FAQ as it relates to your original question.

Can I leave the Battery Tender Plus® battery charger connected to a battery while I’m using the battery to power another appliance like a radio?
Actually, this is basically the same situation that exists by default on many of today’s complex, computer controlled vehicles that have a wide range of on-board electronic devices, many of which consume electric power even when the vehicle is not running. So the short answer is ‘Yes, you can leave the Battery Tender® Plus (BT Plus) battery charger connected to a battery even when it is being used to provide power to another appliance. However, this is definitely not a simple yes or no type of question. There are definitely some things to consider that may limit this type of usage.

Think about how consumer electronic products are used and consequently, how they are designed. To keep the price low and competitive, it is important to limit the battery charger applications to a realistic, manageable portion from the vast number of ways in which a battery charger may be used.

The simplest applications involve charging and maintaining vehicle engine start batteries. The advantage in this application is that there is almost always another, larger source of electric power to charge the battery while the vehicle is running. So the off-line engine start battery charger need not normally supply the full amount of charge stored by the battery. One common exception would be when the vehicle battery is drained because lights were left on.

The point is that the engine start battery charger is not normally expected to deliver its maximum charge current for extremely long, extended periods of time.

[seabob4]

Bob, that's a good point about "minimum voltage", however, lket me say this.  I deal with a LOT of batteries, both AGM and lead acid.  It is my findings that a "good" batt, even when allowed to sit for great lengths of time, will typically drop down to only around 11V min.  A "bad" batt, however, can see voltages down in the 7 or 8 range, given the same length of time.  This indicates a batt that needs replacing, usually because a cell is suspect.  

That same "good" batt, when a bulk charge is applied to it, will typically show upper 13s on a voltmeter, testing rest voltage.  A "bad" batt will show about 12.75V max, given the same applied charge.  It will also drop fairly quickly down to around 12.2V once the charger indicates a full charge and the charger is removed.  A "good" batt will drop to around 12.5-12.6V and stay there...

[Capt. Bob]

Bob, that's a good point about "minimum voltage", however, lket me say this.  I deal with a LOT of batteries, both AGM and lead acid.  It is my findings that a "good" batt, even when allowed to sit for great lengths of time, will typically drop down to only around 11V min.  A "bad" batt, however, can see voltages down in the 7 or 8 range, given the same length of time.  This indicates a batt that needs replacing, usually because a cell is suspect.

Sitting on a shelf/boat with little/no drain isn't what I'm getting at but rather a constant drain such as a light/pump/radio. Any battery that is fully functional inside can be drained to 0 volts given a device draw and time. Therefore my example is based on my own experience (maybe the term ignorance is more appropriate) having left the battery switched in the "on" (1 in this case) position after exercising the engine. The toggle switches on my boat are illuminated (old school) white in the off, red in the on positions. I ran the motor on the muffs, shut down but forgot to switch the battery to the off position. A week or more later I noticed the switch in the on position and upon checking the voltage on the #1 battery found it to be around 2 volts. I tried recharging with my smart charger but it wouldn't happen. As stated earlier, the program didn't have enough voltage to initiate the charge sequence. Prior to this event, the battery worked fine.

I tried "fooling" the charger using the techniques shown in link I provided above but only ended up with two "dead" batteries which my charger could not charge. I then bit the bullet and bought the Optima charger which did boost charge (my term) both batteries (one at a time) and then go into its regular charging program. So far, I have had excellent results with this expensive charger on all three types of batteries I have on the homestead including flooded, AGM and Gel. The incident has also forced me to pay more attention to what I'm doing when running the boat on muffs and consuming alcohol during the same time period.

Chit happens.

[bondobill]

CB
Your last post reminded me that when a battery is on my dash switch panel is illuminated .

No way to turn them off
The panel was installed new this last summer. I have no idea how  much they draw.
I wonder if the tender could keep the battery charged with these on ?

[seabob4]

Odd you were able to do this Bob.  All DC appliances I know of (including switch illumination lights) have a operating range of typically between 9 and 14 VDC.  Once the batt voltage drops below 9, the appliances cease to function.

[seabob4]

Bill, pull the panel and note the positive lead that powers your back-lighting.  Move that to the NAV LGT position (either left or right terminal, the one that powers both running and anchor).  This will cause your back lighting to come on when you turn your nav lgts on...