In the vast arena of battery charger/maintainers makers, there are two who clearly stand out amongst the rest. They are Deltran Corporation of Deland, Florida, maker of the Battery Tender and a newer entry VDC Electronics, Inc. of Englewood, New Jersey, maker of SureCharge and BatteryMINDer.  Both these companies produce a line of charger maintainers (for 6v, 8v and 12 volt lead acid type storage batteries) that are by far "head and shoulders" above the crowd. What makes them different is their charge control technology, which allows their products to be left connected to batteries for weeks, months (or even years) without fear of battery "boil-out" due to over-charge.  Ordinary car/boat chargers are infamous for "frying" batteries or allowing them to self-discharge to a point where they develop a condition know as "sulphation", tiny crystals of sulfuric acid that form on the battery's storage plates.  In time, they build up, creating a barrier to proper charging and discharging.  Charging time will significantly increase with diminishing results (less cranking amps and running time).  Greater heat is also developed within the battery when it is allowed to sulphate, accelerating the breakdown of active storage plate material.  Batteries that should have lasted for five or more years, typically need to be replaced within 1-2 years as a direct result of sulphation build-up. To help you choose the charger maintainer that is right for you, we have assembled below the most important features of both company's 4 major products.  Please keep in mind that only VDC's BatteryMINDer conditions batteries (de-sulphates their charging plates), in addition to charging and maintaining up to 4 batteries at a time.  This feature is both a cost saver, as well as, performance enhancer and should be seriously considered by anyone seeking to maximize performance of any type lead acid battery, including maintenance free, marine, rv, deep cycle, gelled, agm. One last matter before summing up my recommendations.  VDC is offering a "free" battery/charging system monitor, they call the SureGuard (a.k.a. "smart box") to all who purchase their BatteryMINDer. Simply complete the warranty registration card enclosed with each BatteryMINDer package, along with $5.95 for Shipping and Handling and they will send you a $29.95 suggested retail price "smart box", an invaluable aid in determining the condition of both your battery and on-board alternator/generator charging system. If you haven't guessed it by now, my favorites are the Battery Tender Plus and the BatteryMINDer.  Given BatteryMINDer's multiple battery charging/maintaining capabilities and de-suphation conditioning circuitry and n="no charge - no hassle" 5 year warranty policy, my one vote goes to VDC Electronic's BatteryMINDer. Feature: Battery MINDer Battery Tender Plus Sure Charge Battery Tender Jr. UL Listed Yes No* Yes Yes 5-Year Warranty Yes Yes** Yes 2-yrs.*** Multiple battery Charging Yes No Yes (4) No Pulse Type Charging modes Yes (4) No Yes No 3 Stage Charging/Maintenance modes Yes Yes No No Manual Charge mode Override switch/button Yes No No No Charge Current (Peak Amps) 1.20 1.25 1.20 0.75 Auto Float Control (float monitoring) Yes Yes Yes Yes Direct Wall plug-in Yes No Yes Yes Power/Charge LED Indicators Yes Yes Yes Yes 12 Ft. Output Power Cord Yes No Yes Yes Qwik Connect Cord Sets (2) Yes Yes Yes Yes Conditioning (de-sulphation) Yes No No No Battery Tester included Yes No No No Patent-Pending/Applied for Yes No No No Charge re-start Mode Yes Yes Yes Yes Suggested Price $48.80 $59.95 $44.95 $39.95 *     Battery Tender Plus is ETL listed **   Deltran Requires owner of the Battery Tender Plus to pay $15.95 for the limited warranty to be honored, if copy of original bill of sale is not sent with unit. *** Deltran Requires owner to pay $9.95 for the limited warranty to be honored, if copy of original bill of sales is not sent with unit. BatteryMINDer Page