Schumacher SP3 Automatic Battery Extender / Maintainer

• For use with 6 and 12 Volts batteries
• Scrolling digital messaging displays step by step instructions to properly charge your battery
• Auto voltage detection automatically detects 6 or 12 Volts batteries
• Hook attachment allows the unit to hang outside the work area for safety and convenience
• It includes 50 ampere quick connect clamps, 24 inch fused ring leads harness with weather cap, 12 Volts DC adapter and manual

I purchased one of these to charge some sealed lead acid batteries, and it works like a champ. Hook it up to the battery, plug it in and let it do its thing.

That being said, there are a couple of quirks the user should be aware of. The % capacity display is not at all accurate. It will typically state that a battery is 95% full, then increase slowly until saying it is fully charged, and on maintaining. I used this with several 9Ah 12V batteries, and some 8.5Ah 6V batteries. All of these were tested before & after with a BK Precision 601 professional battery analyzer. The readings never agreed, but that is not necessarily a problem.

BK Precision 601 Battery Capacity Analyzer

While the $400+ BK 601 is a great tool, it is not necessary to know the precise values of capacity, load and no-load voltage or internal resistance (unless you want to know these things of course!) If you are maintaining SLA batteries of a smaller capacity, say anywhere from 3 to 20Ah or so, just hook up the Schumacher and ignore the initial reading. If it says 95%, the capacity might be 80% or might be 45% (I saw readings higher and lower on the 601) No matter. Let the Schumacher charge until it says 'Fully Charged' or 'battery maintaining'. But do not stop charging just yet. At that point, the actual capacity might only be at 95 or 97% (as verified by the 601). Let it go another 15 minutes or half an hour. Then go ahead and disconnect. By that time, nearly all the batteries I tested were at the full 100% according to the BK 601.

If the battery is too far gone, the Schumacher will let you know. There are a few batteries here and there that will accept a charge from the Schumacher, but may not perform as well as new batteries. Outside of a professional analyzer, there is not much you can do about them. They will work, but may only have 90% or so of the charge. The Schumacher does as best as it can with them.

It also oworked well at auto-detecting 6V batteries. Very simple to use, and for easy operation and good performance, and a great price, I give it 5 stars. Just be aware of its limitations.

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After receiving this gadget, I realize that I probably could have used the smaller SP2 unit, but now that I've had it a few weeks, I'm quite pleased with how it works.

It is pretty large, but still only about a quarter the sise of a car charger. It's roughly the size of a brick, and has a big LED readout that tells you what it's doing readable from a good distance.

So far, I've only used the alligator clips for my motorcycle battery, but this also comes with a connector that you can attach permanently to the battery and has a simple connector to the charger cord. That means you don't have to remove the seat to hook up the charger. That seems pretty useful, and if I ever decide to unhook my battery and risk losing all the settings on my stereo, I'll install it.

I think something like this is essential in places that have a proper winter that keeps you from riding for weeks at a time.

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This is a great gadget and a must have for any garage mechanic. It takes the guess work out of your battery's maint. Very easy to use. Ive only had it a few days and its already saved me time. I highly reccomend it. Well worth the money!!!

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I bought this battery "extender" to maintain the battery in my two-year-old, rarely-driven garage queen. When I first attached the unit, it said it was analyzing the battery, then reported that it was 5% charged, and proceeded to begin charging. The car had been sitting for three weeks, so I was not alarmed at the battery's condition. It has now been 48 hours, and display says the battery is at 91% charge, the same thing it said twelve hours ago. So either my like-new battery can no longer take a full charge, or this unit is flawed in some way.

Other than this odd behavior, I like the SP3. It tells you what it's doing, takes up little space, and comes with a few different connection options.

One last thing. The manual that comes in the box is brief and omits information--like the connection options. I found a better copy online, but that should not be necessary.

Here is an update: after four days of charging (!), the unit finally switched over to "Maintaining", so all seems well.

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Great charger for the price you can't find a better one. I highly recommend. It analyzes , charges and maintains your battery. Great charger for long time storage of your battery.