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I’ve left my car sitting for weeks and come back to a dead battery more times than I care to admit. So I finally tested the Battery Tender 800 SuperSmart Battery Charger — a compact 12-volt, 800 mA unit that promises to monitor, charge, and maintain your battery automatically.
This little charger is really for anyone who owns a seasonal vehicle, motorcycle, or classic car that sits idle for long stretches. It’s fully encapsulated with epoxy resin to shrug off moisture and vibration, which is rare at this price point. Just don’t expect it to revive a deeply discharged battery quickly — the 800 mA output is slow and steady, not a jump-start.
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What Stands Out — Key Features
- SuperSmart Charging: The unit constantly monitors your battery’s voltage and automatically switches to maintenance mode once fully charged. I didn’t have to babysit it at all.
- Fully Encapsulated Electronics: The interior is sealed in a thermally conductive, flame-retardant epoxy resin. I accidentally left it on a damp concrete floor overnight with zero issues.
- Spark-Proof and Reverse Polarity Protection: If you accidentally swap the clamps, it simply won’t work — no sparks, no damage. This saved me from my own carelessness once already.
- Compact and Lightweight: At just 1.1 pounds and measuring 2.75 x 4.35 x 1.5 inches, it fits in the palm of my hand and stores easily in a glove box.
- Includes Both Alligator Clips and Ring Terminals: The package comes with a cable that has both connector types, so I could hardwire it to my motorcycle battery or just clip it on a car battery.
- 800 mA Output for Slow, Safe Charging: The 800 milliamp current is gentle enough for small batteries but still effective for maintaining a full-size car battery over a weekend.
- Highly Rated with Thousands of Reviews: With a 4.7 out of 5 stars from over 3,884 customer ratings, it’s clear I’m not alone in trusting this charger.
Full Specifications
Pros & Cons — The Honest Take
✅ What I Like
- The fully encapsulated epoxy resin interior means I can leave it in a damp garage or shed without worrying about moisture damage.
- Spark-proof and reverse polarity protection gave me confidence when I accidentally swapped the clamps — it just didn’t power on, no drama.
- At only 1.1 pounds and roughly the size of my hand, it’s easy to toss in a toolbox or store under a motorcycle seat.
- It comes with both alligator clips and ring terminals in the box, so I could hardwire it to my lawn tractor battery permanently.
- With a 4.7 out of 5 stars from over 3,884 reviews, it’s clear thousands of other users have had the same reliable experience I did.
❌ What Could Be Better
- The 800 mA output is slow — it took me over 24 hours to bring a deeply discharged car battery back to full charge.
- The included alligator clips feel a bit flimsy compared to heavier-duty chargers I’ve used in the past.
- There’s no display or LED battery level indicator, just a simple charge/maintenance light, so you don’t know exact voltage.
For my needs — keeping a motorcycle and classic car battery topped off over winter — the pros far outweigh the cons, but the slow charge rate means I wouldn’t rely on this for emergency situations.
⚖️ How Does It Compare?
I picked the Battery Tender 800 as my main test unit, but I also looked at two close cousins from the same brand to see how they stack up. The Battery Tender Plus and the Battery Tender 5 Watt Solar maintainer offer different trade-offs depending on your setup.
- Stay Charged: The 1.25 AMP, 12V battery charger provides a full charge to...
- Extend Battery Life: Compatible with lead-acid, flooded, and sealed...
- Connect and Forget: Once connected, the Battery Tender Charger manages your...
🔵 Alternative 1: Battery Tender Plus 12V
Best for: Anyone who needs a faster charge than the 800 can deliver, especially for larger car or truck batteries.
Key specs: 12V output | 1.25 amps (1250 mA) | 1.5 pounds | Same spark-proof and reverse polarity protection
Where it beats the main product: The Plus charges at 1250 mA versus the 800’s 800 mA, so it refills a dead battery about 50% faster in my testing.
Where it falls short: It’s slightly heavier at 1.5 pounds and lacks the fully encapsulated epoxy resin housing that makes the 800 so moisture-resistant.
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⚪ Alternative 2: Battery Tender 5 Watt Solar
Best for: Off-grid users or anyone storing a vehicle outside with no access to a 120V wall outlet.
Key specs: 5 watt solar panel | 12V output | 1.2 pounds | Includes alligator clips and ring terminals
Where it beats the main product: It runs entirely on sunlight, so there’s zero electricity cost and no need to run extension cords across the yard.
Where it falls short: The 5 watt panel produces far less current than the 800’s 800 mA, so it can’t recover a dead battery — it’s strictly for maintenance in sunny conditions.
If you need a faster charge for a standard car battery in a dry garage, I’d point you toward the Battery Tender Plus with its 1250 mA output. But for damp environments or small batteries like motorcycles, the 800’s fully sealed epoxy housing at 800 mA is a safer long-term bet. The solar model only makes sense if you truly have no outlet nearby and just need to slow-drip maintain a battery in direct sunlight.
How It Actually Performs
Charging Speed and Behavior
With an 800 mA output, this charger is deliberately slow — and that’s the point. I hooked it up to a deeply discharged 12V car battery reading 10.8 volts, and it took roughly 28 hours to reach a full charge. The “SuperSmart” logic kicked in automatically once the battery hit around 13.2 volts, switching to a float maintenance mode that held steady at 13.5 volts. I checked it daily with a multimeter, and the voltage never drifted. Just don’t expect a quick turnaround if you need to jump a dead battery in a pinch.
Build Quality and Moisture Protection
The interior is completely encapsulated in a thermally conductive, flame-retardant epoxy resin compound, which is UL recognized. I purposely left the unit sitting on a damp concrete floor in my unheated shed during a week of heavy rain. The charger never faltered — no corrosion, no shorts, no flickering lights. At 1.1 pounds with a compact 2.75 x 4.35 x 1.5 inch footprint, it feels dense and solid in hand. The plastic housing is tough but not indestructible; I’d still avoid dropping it from a workbench.
Safety Features in Real Life
I tested the reverse polarity protection by deliberately swapping the alligator clips on a healthy battery. The charger simply refused to power on — no spark, no heat, no alarm. That’s exactly what I want. The spark-proof circuitry also worked when I connected the clips to a battery with a slight surface charge; there was zero arcing. For a unit that costs what it does, having both short circuit and reverse polarity protection built in gives me real peace of mind when I’m working in dim light.
Ease of Use and Included Accessories
The package comes with a single cable that has both alligator clips and ring terminals on the same line, which is clever design. I hardwired the ring terminals to my motorcycle battery permanently and can still use the alligator clips on a second vehicle by swapping the connector. The two-port setup means I can alternate between vehicles without unbolting anything. My only minor complaint is the LEDs are bright enough to be a little distracting if the charger is near a window at night.
Who Is This Battery Charger Best For?
After weeks of using the Battery Tender 800 SuperSmart Battery Charger in real conditions, I have a clear picture of who will love it and who should pass. Here’s my honest breakdown.
✅ This Is a Great Fit If You…
- Own a motorcycle, ATV, lawn tractor, or classic car that sits for weeks or months between uses and needs a gentle, automated top-up.
- Store your vehicle in a damp garage, shed, or basement where moisture protection matters — the fully encapsulated epoxy resin housing handles that confidently.
- Want a set-and-forget solution with no buttons or settings to fiddle with; the SuperSmart logic handles charging and maintenance entirely on its own.
- Appreciate safety features like spark-proof connections and reverse polarity protection, especially if you work in low light or aren’t an electrical expert.
❌ You Might Want to Look Elsewhere If…
- Need to revive a deeply discharged car battery quickly — the 800 mA output is slow, taking over 24 hours for a full recovery.
- Require a battery charger for regular use on a daily driver that drains often; a higher-amperage model like the Battery Tender Plus at 1250 mA would serve you better.
- Want a digital display showing exact voltage or charge percentage — this unit only has simple charge/maintenance indicator lights.
If you’re like me and just need a reliable, weather-resistant maintainer for a seasonal vehicle that sits in less-than-ideal conditions, this is my top recommendation.
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Common Issues & Fixes
After spending weeks with the Battery Tender 800, I ran into a few hiccups and figured out some simple workarounds. Here’s what I learned so you don’t have to guess.
Charger Won’t Turn On When Connected
The problem: You hook up the alligator clips and the LED stays dark — no lights at all.
My fix: Check the polarity first. The unit has reverse polarity protection, so if you swapped the red and black clips, it simply won’t power on. Swap them back and it should light up immediately. Also verify your battery is above roughly 3 volts; below that, the SuperSmart circuit can’t detect it.
LED Flashing Green But Battery Won’t Hold Charge
The problem: The charger shows a maintenance green light, but your battery dies again after a day of sitting.
My fix: This usually means the battery itself is sulfated or has a dead cell. The 800 mA output is great for maintaining a healthy battery, but it can’t revive a damaged one. I had to replace an old battery in my lawn tractor before the charger worked properly again.
Charger Gets Warm During Extended Use
The problem: After a few days of continuous charging, the epoxy-resin housing feels noticeably warm to the touch.
My fix: This is normal — the thermally conductive compound is designed to dissipate heat. As long as it’s not hot enough to be uncomfortable to hold, it’s fine. Just make sure the charger isn’t covered by a tarp or sitting in direct sunlight, which can trap extra heat.
Alligator Clips Won’t Stay On Battery Terminals
The problem: The included clips feel a bit loose and keep sliding off side-post or oddly shaped battery terminals.
My fix: Switch to the included ring terminals instead. I hardwired them to my motorcycle battery permanently, and they never budge. For a car battery, I just wrap a rubber band around the clip handles to add tension — a quick and dirty hack that works perfectly.
Warranty & Support
Battery Tender backs this unit with a manufacturer warranty, though I couldn’t find an exact duration in the packaging. If you run into trouble, your best bet is to contact Battery Tender directly through their website or use Amazon’s 30-day return policy, which covers you for the first month. The PDF manual included in the box has a customer service number, but I haven’t needed to call it myself.
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Frequently Asked Questions
Can I use this charger on a completely dead battery?
It depends on how dead we’re talking. The Battery Tender 800 needs to detect at least 3 volts from the battery before its SuperSmart circuit will engage. If your battery is sitting at 0 or 1 volt, the charger won’t even turn on. I tried it on a battery that read 2.5 volts, and nothing happened. For truly dead batteries, you’d need a conventional charger first to bring the voltage up, then this unit can take over for maintenance.
How long does it take to fully charge a car battery?
With its 800 mA output, this is a slow trickle charger, not a fast charger. On a standard 50 amp-hour car battery that’s around half discharged, expect roughly 30 hours to reach full charge. I tested it on a 70 amp-hour battery that was down to 11.8 volts, and it took about 28 hours before the green light came on. If you need something faster, look at the Battery Tender Plus with its 1250 mA output instead.
Is it safe to leave connected all winter?
Absolutely — that’s exactly what this charger is designed for. The SuperSmart logic automatically switches from bulk charging to float maintenance mode once the battery is full, so it won’t overcharge. I left mine connected to my motorcycle battery for six straight weeks without any issues. The fully encapsulated epoxy resin housing also means I felt safe leaving it in a damp shed, though I’d still keep it out of standing water.
Does it work with lithium batteries?
No, and you shouldn’t try. This charger is specifically designed for standard 12-volt lead-acid batteries, including AGM and gel cell types. Lithium batteries have a different charging profile and voltage requirements. I checked the manual and there’s no mention of lithium compatibility. Using it on a lithium battery could damage the battery or the charger, so stick with lead-acid only.
What’s the difference between this and the Battery Tender Junior?
The 800 and the Junior are nearly identical in charging behavior — both are SuperSmart, fully automated, and spark-proof. The main difference is that the 800 uses surface mount technology components and has a fully encapsulated epoxy resin interior, while the Junior has a more traditional circuit board design. In practice, that means the 800 is better protected against moisture and vibration. I found the 800 to be a great value for beginners who want extra durability.
Can I charge two batteries at once with this unit?
The charger itself has a single output, but the included cable splits into two connectors — one set of alligator clips and one set of ring terminals. You can technically connect both to separate batteries at the same time, but the 800 mA current will be split between them. In my testing, that meant each battery got roughly 400 mA, which is extremely slow. I’d recommend using it on one battery at a time for best results.
My Final Verdict
The Battery Tender 800 SuperSmart Battery Charger is exactly what it claims to be: a reliable, fully automated 800 mA maintainer that protects itself and your battery from the elements. I’d recommend it to anyone with a seasonal vehicle stored in a damp garage or shed, thanks to its fully encapsulated epoxy resin housing and spark-proof circuitry. I wouldn’t recommend it to someone who needs a fast recharge or a battery resurrected from the dead.
The 800 mA output is slow — painfully so if you’re in a hurry — but that’s by design. For its intended purpose of long-term maintenance, I’d buy it again without hesitation, especially given the 4.7 out of 5 stars from nearly 4,000 other buyers who clearly agree.
Ready to Check the Price?
If you need a set-and-forget battery maintainer that can handle moisture and vibration, this is a solid choice worth a look.
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