Liftmaster 3800 Battery backup (475LM)

[justsam]

I have been considering adding a battery back up to my installed 3800 for some time, but we recently had a fairly long duration power outage that convinced me to go for it.

Clearly the system has a manual release and my door is well balanced so not all that difficult to open, but I was more concerned that my wife may in a bit of a panic not release the deadbolt and wonder why the release was not working.

The unit is very much plug and play, with one molex type connector to the 3800, and no other power cord. There are two mounting screws and the physical packaging is a bit odd, more mated to the conventional openers as opposed to the 3800 packaging. When mounted to the wall, the legend for the description of the LED's is covered.

Inside the unit uses two 12 Volt batteries to power the 24 VDC motor in the 3800. The battery leads are molded in the battery tops, and have a molex type connector to go to the circuit board. This may well mean at replacement time you will need to clip the battery leads at the battery and terminate with a standard 1/4 inch push on connector which most batteries of this type use. Of course you could just buy the "genuine" Liftmaster replacement. There is a moderate amount of heat generated by power resistors in the charging circuit maintain reasonable battery temperatures, if you are in that type of environment. (I'm not)

For about $70, good piece of mind, easy install, and functions well.

 

[jbs]

Good review. Thanks. How many open/close cycles can one expect to get out of it (roughly).

 

[NitroPress]

After the long outages here, I was going to rig backup power for my two 3800s... until I realized, belatedly, that they are on a circuit powered by the backup generator. (I had no reason to expect they were and it took me a few days to notice the control pads were lit...)

$70 is a pretty fair price given that a pair of decent gelcells alone would run most of that. No real need to DIY something for the other $20 or so.

 

[cowboyjosh]

$70 is a whole lot less $ then a CARB compliant generator seeing how your in California. On a LM with belt drive, you can get about 20 cycles out of a backup battery, for the poster who asked, thats what LM states in the manual.

 

[Teken]

$70 is a whole lot less $ then a CARB compliant generator seeing how your in California. On a LM with belt drive, you can get about 20 cycles out of a backup battery, for the poster who asked, thats what LM states in the manual.

This assumes all variables are equal and the same. If the door is not properly balanced it will drain the battery.

If the climate is extremely hot / cold this will reduce the available current. If the batteries are over two years old they will produce less current.

Thus, affecting the amount of up & down cycles available . . . The molded connectors on the batteries only came into play in the last three years.

This was the worst idea ever and forced the uneducated home owner into paying an insane price for a cheap aszz battery!

Regardless, the battery pack is well made, and does serve its purpose as it is so designed. I have installed 12 of these units in the last two years and they all perform flawlessly . . .