Quote:
Originally Posted by OHguest55
I bought a Battery Tender Jr. 750mA. Is this the right size to use when not using the trailer? I am confused about leaving the trailer on shore power all the time.
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I have the BT 750 mA, and it has served me well.
First, the BT is a battery maintainer, not a battery charger. It is intended for use during long-term storage of the battery. "Long term" isn't a well-defined term, but let's say a week or more. For shorter storage time, your TM charger will be fine.
The way to tell if your BT is doing the job is this:
1. Make sure that the batteries are fully charged, and the electrolyte level is proper. If you ask the BT to charge, it will do so - but because of its limited capacity, it will take a long time. I've done it.
2. Disconnect the batteries from everything. The TM, and any other RV, has parasitic loads that slowly drain the battery, even when you think everything is turned off.
3. Connect the BT to the batteries. Power it up, and look at the lights on the front of it. The lights will probably come up as blinking red, meaning "charging".
4. Go away for a few hours. When you come back, the lights will have changed to blinking green, meaning something like "We're just about there"
5. Again, go away for a while - maybe as long as 24 hours for your big batteries. The lights on the BT should become solid green. This means "The batteries are fully charged, and I am maintaining them". In other words, the BT has brought the batteries to full charge, and has sufficient capacity to hold them there, making up for any self-discharge that happens in the batteries. This is exactly what you want, and it tells you that the BT is up to the task. A bigger BT would get to solid green a bit faster, but once it gets there, it would do exactly the same thing as your BT 750 mA unit.
If the BT never gets to solid green, then it may be too small. I doubt that this is the case.
I have left a battery on the 750 mA BT for months, and it always works.
Bill