Recommendations for Battery Tenders

[Brett Dikeman]

On Jul 26, 2005, at 12:59 PM, Keith Lawyer wrote:

> Of course, a constant trickle charge is no good for a long period  
> of time, but this one says "maintenance charge turns on and off as  
> needed."  Not true?

To maintain the battery properly, it needs to be held at "float"  
voltage; it's better than charging every time the battery drops in  
voltage.

This page explains most of the different types of chargers, might  
have to skip down a little bit.

http://www.uuhome.de/william.darden/carfaq9.htm

The wall-wart BatteryTender lacks the power to do a proper multi- 
stage charge on anything larger than a small motorcycle/ATV/lawnmower  
battery, and it would take several days to bring a dead car battery  
back up using one, so don't consider it a "charger".  The larger box- 
shaped unit is of the "smart" charger variety (ie multi-stage) with  
float capability, and will be a little bit better at bringing up a  
dead battery, though still not ideal for  charging, since it can't  
hit anywhere near proper currents for bulk+absorption charge  
currents.  Mine conducts a little 'self test' on the battery,  
applying a gentle charge to see how sulfated the battery is, and its  
capacity.

The Vector units sold at many auto parts stores, wal mart, etc fall  
into the same "microprocessor controlled" category, but lack float  
charging capabilities; they're fully automatic,.  They also are  
slightly less than reliable- my 6-month-old unit had to be replaced  
just a week or two ago because it declared every battery connected to  
it to either be un-chargeable, or full.  When they work, however,  
they seem to work quite well.  My replacement unit does a short  
charge, stops, watches the voltage fall to determine capacity and  
SoC, then resumes charging at an appropriate rate.  The battery clips  
are also of a much improved narrow-nose design (the original clips  
were short and very fat, virtually impossible to get onto many  
terminals and jump posts).

I suppose the best combination would be the wall-wart battery tender,  
with one of the Vector chargers to bring it up to 100% SoC; you'll  
also be covered for left-the-lights-on-overnight contingencies.  The  
mid-size tender is best if you want an all-in-one.

Brett
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