Battery Tender 800 Waterproof 12V Battery Charger Review

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(More customer reviews)Deltran Battery Tender 12-Volt 800 milliamp Waterproof Battery Charger
The Battery Tender Waterproof Tender operates in essentially 3 stages. It first initiates an absorption charge that attempts to charge your battery to 14.5 VDC at up to 0.8A (or 800mA). This bit of information was not readily advertised, so I was concerned when I heard my battery making gurgling noises while the LED was "amber" for the past 8 hours. This battery was only 2 years old with less than 5000 miles and had been maintained since day 1, so I was sure it wasn't a problem with the battery. It turns out that it was nothing to be concerned about since this charger was designed to be used for long-term storage of batteries.
My previous charger, a Black & Decker / Vector 2A "smart" automatic maintainer tried to keep my battery voltage at 14.75 VDC at 2A for over 24 hours. Needless to say, I was concerned when I saw this happening with a brand new Battery Tender. I dug around on their website and discovered a PDF that indicated the Tender would try to reach 14.5 VDC for the absorption phase, at which point it would switch to a trickling charge and finally the maintenance charge. I logged all of the readings and confirmed that once the battery reached 14.4-14.5 VDC, it would start to trickle down finally remaining at about 13.12-13.22 VDC @ 20-100 mA. A modern car's parasitic draw is about 10-50 mA, so the maintenance charge is to compensate for the parasitic draw and for self-discharging of the battery. I discovered the Tender does a much better job at a maintenance charge because I have yet to see the Tender go into the Amber-LED mode, whereas my Vector/B&D occasionally switches back and forth even on a fully charged battery. I logged some data from the Vector/B&D and discovered that once the LED is green, it provides NO current to the battery. In essence, the Vector/B&D just shuts off once it reaches 14.5 VDC - which is not as useful as providing an actual maintenance charge. The Battery Tender wins. Quite a few people have commented that their Sears "smart/automatic" maintainer and other brands constantly switch between the Green and Amber modes. I suspect those chargers are doing the same thing as the Vector/B&D. They just shut off when the battery is "charged", which is not very good for the battery. It needs to hold a maintenance charge to prevent sulfation.
The Tender Waterproof is fully encapsulated with a thermally conductive potting material. This makes the unit quite heavy for such a small device. It uses a quick-disconnect 2-terminal fitting that is commonly used for battery chargers/maintainers. It comes with ring terminals or large battery clamps all fused with a 7.5A ATC fuse. I made my own wiring harness with smaller alligator clips since I don't have room under the hood for large clamps, and I do not want to permanently install a set of ring terminals that can short out or cause other problems in the long-run.
Pros: Battery Tender has an excellent reputation for making reliable chargers. The Waterproof unit is quite durable and is insulated from shock, water, corrosion, extreme temperatures and other environmental variables.
Cons: At 800mA max current capacity, this charger will work rather slowly for 50Ah or larger capacity batteries, so expect 10-12 hours upon hooking it up to a battery before the LED turns green. The benefit of this is that it prevents boiling the battery or generating a lot of heat due to excessive current.
Overall: If you're using the charger in an environment subject to cold or hot temperature swings with plenty of moisture, such as in a detached garage for your motorcycle, boat, stored vehicle, or even a daily driver, I highly recommend the Waterproof unit over the Tender Jr or Tender Plus.
UPDATE:
I decided to purchase an additional Battery Tender Waterproof because I needed another charger for my daily driver and because I experienced no problems with the first unit.

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The Battery Tender Waterproof 800 12-volt/.80-amp Battery Charger is the ultraportable solution to the challenge of keeping vehicle batteries optimally powered when not in use, and in situations where water may be present. It is able to charge any lead-acid battery, including standard and sealed AGM and GEL Cell battery types, and is also designed to be easy to use in small spaces, to utilize a 3-step charging program and safely function in a fully automatic mode. Taken together this makes the Waterproof 800 an excellent means of ensuring that the batteries for your ATV's, watercraft, motorcycles and boats are fully and safely charged and ready to go when you are.

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