How long can a battery tender be left hooked up safely? All winter? or is that too long?

 

I believe they can if you have one of the better units like a Battery Tender Plus. I unhook mine from time to time just to give everything a break, though. Does it help? Is my reasoning sound? I don't know, but I haven't had any trouble doing it like this. Someone smarter than me will chime in I'm sure.

 

A quality tender can be hooked up all winter with no ill effects. It monitors the charge and turns itself on only when a charge is needed. Stay with the quality units though.

 

My old Harley is at the cabin and is left on the Battery Tender all the time I am not there. It is my understanding a battery will loose 30% of its charge in 4-6 weeks so that said the battery would be dead in 18-20 weeks or 4-5 months. I don't go often in the winter and found the Battery tender always has the battery at charge and has never burnt a battery up.

 

Agreed. Mine has been hooked on a tender all winter so far. The tender that I have switches on/off automatically, depending on the charge.

 

I use both the Battery Tender and the Harley version on my 2 Harleys and my 2 Boats and my John Deere. You can buy the Battery Tender at most Farm stores for $29.00 The units i have look like a small charger that plugs in the wall with a small cable coming out. I put 2 flat connectors on everything I own and move chargers from time to time. FYI the 2 flat connector from your local department store trailer hardware aisle works with these little chargers.

 

Thanks all for your replys. I am using the HD supersmart 12 volt 750 amp

 

The tender also has a fuse so in case there is a surge in your power it will not damage the battery. I leave all my bikes hooked up all the time unless I am riding them. I am yet to have a problem.

 

I only plug mine in about an hour a week, in an unheated garage - and with a good battery I really don't even need to leave it on that long.

 

A decent one will monitor the battery voltage and have temperature compensation. When I replaced the stock battery with a new AGM, the instructions said to get a tender with temp comp. Leave a good charger on all the time.

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While a battery is being charged, it is important that the charger absorption and float, maintenance voltages closely match the recommendations of the battery manufacturer. The absorption voltage match is important for quick charging. The float, maintenance voltage match is important for long term, storage charging.

Batteries are sensitive to temperature. Recall the number of TV ads showing how tough a battery is when it can start a vehicle in sub-zero temperatures. Cold temperatures tend to reduce a battery’s ability to deliver current to a load. High temperatures not only increase a battery’s ability to deliver current to a load, but also increase a battery’s internal losses. Temperature compensation is a way to change a charger’s output voltage to maintain optimum compatibility with the battery’s charging requirements. The way it works is that the charger senses the ambient temperature. Then it increases the charge voltage when it is cold and decreases the charge voltage when it is hot. Typical values for temperature compensation for a lead acid battery are minus 0.0025 to minus 0.004 volts per degree Centigrade per 2-volt cell. For a 12-volt battery, that would be minus 0.015 volts to minus 0.024 volts per °C. The reference temperature requiring zero charge voltage compensation is 25 °C or 77 °F.

How important is temperature compensation? Like with most everything else about batteries, it depends on the application. For industrial, critical load, standby power applications, where the batteries may be connected to a live charger for a number of years, then temperature compensation can have a significant influence on battery life. In many consumer applications like SLI, deep cycle marine, etc., temperature compensation will increase long-term battery performance, but it is probably not essential in all applications. Where it is most beneficial is in helping to minimize the negative impact of a battery’s self-discharge characteristics in high temperature environments. Deltran Battery Tender Plus Battery Chargers Overcome the Negative Impact of High Temperature on Battery Performance.

The self-discharge rate of a battery is directly dependent upon the ambient temperature of the battery environment. At higher temperatures, the chemical reaction rates that determine self-discharge will also increase.

When a battery sits idle, its self-discharge characteristics will reduce its ability to deliver power on its next use. If the battery either sits long enough, or if the ambient temperature rises high enough, then the battery may become fully discharged. In fact, it is possible for the battery to be over-discharged to the point where it cannot be recovered.
The Deltran Battery Tender Plus battery chargers overcome the negative impact of higher ambient temperature and battery self-discharge in two ways. First, the Deltran Battery Tender Plus battery charger applies a safe, float, maintenance voltage level to the battery to overcome its internal losses and counteract the self-discharge phenomena. Second, the Battery Tender Plus battery charger automatically compensates the amplitude of its charge voltages for changes in ambient temperature. It reduces the amplitude of the float, maintenance voltage as the ambient temperature increases and it increases the amplitude of the charge voltages in colder temperatures. In mathematical terms, this type of compensation scheme is called a "Negative Temperature Coefficient".

The temperature compensation ratio employed by the Deltran Battery Tender Plus battery chargers is approximately minus 3.67 millivolts per battery cell per degree Centigrade of temperature rise above 25 °C. Stated another way, the output voltage of the Deltran Battery Tender Plus battery charger will drop 0.022 volts, or 22 millivolts, for every degree Centigrade temperature rise, when it is connected to a 12-volt battery.
In the event that the temperature would rise enough so that the Deltran Battery Tender Plus battery charger voltage output drops below the what would be considered a normal operating voltage for a 12 volt battery, then the Deltran Battery Tender Plus battery charger automatically disconnects itself from the battery via an internal solid state mechanism, affording an extra measure of safety in a very high temperature environment.