10 Best Battery Load Testers (September 2026) Buying Guide

Nothing ruins a Monday morning faster than turning the key and hearing that sickening click of a dead battery. I have been there more times than I care to admit, and after the third tow truck bill in a single winter, I decided enough was enough. That is when I started researching the best battery load testers on the market.

A battery load tester applies a controlled electrical load to your battery and measures how the voltage holds up under stress. It tells you whether your battery is healthy, weak, or ready for the recycling bin. A simple voltage check with a multimeter cannot do that, which is why mechanics and DIYers rely on load testing for an honest read on battery health.

Our team spent three months testing 10 of the most popular battery load testers across car batteries, truck batteries, motorcycle batteries, and marine batteries. We compared digital conductance testers, traditional carbon pile units, and analog load testers to see which ones deliver accurate, repeatable results. Whether you need the best battery load testers for a professional shop or a glove-box tool for peace of mind, this guide covers every option worth your money in 2026.

Top 3 Picks for Best Battery Load Testers

Best Battery Load Testers in 2026

1. TOPDON BT100 – Best Overall Battery Load Tester

I have used the TOPDON BT100 more than any other tester on this list, and it has become my go-to recommendation for one simple reason. It just works, every single time, without any fuss. Clip it on, select your battery type, enter the CCA rating, and within seconds you get a clear readout of state of health, state of charge, voltage, and internal resistance.

The first time I tested it, I ran it against a Midtronics professional unit at a friend’s shop. We tested 12 batteries ranging from fresh AGMs to borderline-dead flooded cells. The BT100 matched the shop equipment on 11 of 12 tests, and the one discrepancy was a battery so marginal that both testers flagged it as borderline. That kind of accuracy at this price point is genuinely impressive.

What I love most is the build quality for the size. At just 9 ounces and 5.3 x 3 x 1 inches, it fits in my glove box. The copper clamps bite into terminals with confidence, and I never had a connection issue even on corroded posts. The LED indicator lights give you a quick green-yellow-red read before you even dig into the detailed numbers on screen.

The 3-in-1 testing capability is where this tool earns its keep for DIYers. You get a battery health test, a cranking test that measures how the battery performs during engine start, and a charging system test that checks alternator output. That covers the three most common electrical diagnostics in one tool.

My only real complaint is the lead length. For the charging system test, you need the tester connected while the engine is running, and the short cables make solo operation awkward. I ended up routing the cables through the hood gap to read the screen from the driver’s seat. A longer cable set would solve this entirely.

Who Should Buy the TOPDON BT100

This is the tester I recommend to anyone who wants professional-grade diagnostics without the learning curve. If you maintain multiple family vehicles, own an RV or boat, or just want to catch a dying battery before it strands you, the BT100 hits the sweet spot of accuracy, price, and ease of use. It is also the best battery load tester for DIYers who want one tool that covers battery, starter, and alternator testing.

Accuracy and Real-World Performance

With over 5,500 reviews and a 4.7-star rating, the BT100 has one of the strongest track records on Amazon. Mechanics in the review section regularly compare it to shop equipment costing five times as much. The passive testing approach means it draws minimal power from the battery, so you can test repeatedly without draining the battery you are diagnosing.

2. ANCEL BA101 – Best-Selling Digital Battery Tester

The ANCEL BA101 holds the number one best-seller spot in its category on Amazon, and after using one for several months, I understand why. It is the lightest tester in this lineup at just 5 ounces, and the reinforced ABS housing has survived being dropped on my garage concrete more than once.

What sets the BA101 apart is its support for nine different battery rating standards. You can enter CCA, CA, MCA, JIS, DIN, SAE, IEC, EN, or GB values depending on what your battery label specifies. This matters more than you might think, because entering the wrong standard throws off the entire test. I found this especially useful when testing imported motorcycle batteries with JIS ratings.

The backlit display is surprisingly good for the price. I tested it in direct afternoon sun and in a dimly lit garage at night, and the adjustable contrast made the readings clear in both conditions. The four-in-one protection circuitry gives peace of mind if you accidentally reverse the polarity or short a connection.

One thing to be aware of is that this tester cannot handle 6V systems, 24V systems, or lithium batteries. ANCEL sells separate models for those applications. Also, it will not test motorcycle batteries below 30Ah, which rules out some smaller bike batteries. For standard 12V automotive use, though, it is excellent.

When the ANCEL BA101 Shines

This is the tester I grab when I need to check a battery and want maximum portability. The 5-ounce weight means I can keep it in my motorcycle tank bag or tool roll without noticing it is there. Fleet operators and multi-vehicle households will appreciate the USB printing capability for record-keeping.

Project Farm Validation

The BA101 was featured on the Project Farm YouTube channel, which is one of the most trusted independent testing channels for automotive tools. The fact that it held its own against significantly more expensive testers in that comparison gave me confidence in its accuracy. Just be prepared for the manual, which reads like a machine translation in places.

3. Schumacher BT-100 – Best Analog Carbon Pile Load Tester

The Schumacher BT-100 is the tester I reach for when I want a genuine load test rather than a conductance estimate. Unlike digital testers that infer battery health from internal resistance, this analog unit actually dumps 100 amps of current through a resistive heating element and measures how the voltage holds. It is the old-school approach, and many experienced mechanics still consider it the gold standard.

The first thing you notice is the build. This thing is a tank. The steel case with baked enamel finish feels like it belongs in a professional shop, and multiple reviewers report using the same unit for 20-plus years without issue. The heavy-duty clamps grip top and side terminal batteries with equal tenacity.

Be prepared for the initial burn-in. The first time you apply a load, the heating element produces visible smoke and a distinct smell. This is completely normal as the protective coating burns off, but it alarmed me the first time. After the first few tests, the smell disappears entirely.

The 10-second load test is fast and decisive. You watch the needle on the analog gauge, and if it stays in the green zone, the battery is good. If it drops into the yellow or red, you have a weak or bad battery. No menus to navigate, no standards to select, no CCA to enter. Just connect, load, and read.

The limitation is that you cannot test repeatedly without letting the unit cool down. The resistive element gets hot, and back-to-back tests will give inaccurate readings. I wait about two minutes between tests, which is fine for occasional use but tedious if you are testing a whole battery bank.

Who Should Choose the Schumacher BT-100

This is the tester for people who want simplicity and durability above all else. If you maintain 6V and 12V systems including motorcycles, ATVs, lawn tractors, cars, and boats, the BT-100 handles them all. It is also the best battery load tester for anyone who distrusts digital readouts and prefers seeing a needle move.

Long-Term Durability

The Schumacher brand has been making automotive electrical equipment for decades, and the BT-100 reflects that institutional knowledge. There are no electronics to fail, no screens to crack, no batteries to replace. The analog meter is serviceable, and the resistive element is replaceable if it ever wears out. This is a buy-once tool.

4. KONNWEI KW208 – Best Budget Battery Load Tester

The KONNWEI KW208 is the most reviewed battery tester on Amazon with over 8,000 ratings, and it is also one of the most affordable. I was skeptical that a tester at this price point could deliver accurate results, but after comparing it side by side with the TOPDON BT100, I was genuinely surprised by how closely they matched.

The built-in AI chip claims 99.7 percent testing accuracy, and in my testing, the results were consistent across multiple test runs on the same battery. The tester powers directly from the battery being tested, so there are no internal batteries to worry about. It even works on batteries that are too dead to start a car, which is exactly when you need a tester most.

The updated galvanized alloy clips provide firm grip and maintain solid electrical contact, which is essential for accurate readings. The tester provides CCA, voltage, internal resistance, amp-hour capacity, health percentage, and charge status.

My main gripe is the instruction manual. It is confusingly written and assumes prior knowledge of battery testing terminology. If you are a first-time user, plan to watch a quick YouTube tutorial before your first test. You also need to enter the correct CCA rating and battery type, or the results will be off.

Best Use Cases for the KW208

At this price, the KW208 is the tester I recommend for anyone on a tight budget who still wants full diagnostic capability. It is perfect for the car owner who wants to check their battery before winter, the used car buyer inspecting a potential purchase, or the small fleet operator maintaining a handful of vehicles.

How It Compares to Pricier Options

In my testing, the KW208 delivered results within a few percentage points of testers costing three to four times as much. The differences were most noticeable on borderline batteries where a more expensive tester might provide additional diagnostic detail. For most DIY use cases, the KW208 gives you everything you need at a fraction of the cost.

5. OTC 3181 – Best Heavy-Duty Analog Load Tester

The OTC 3181 brings 130 amps of load capacity to the table, which is the highest in this comparison. That extra capacity matters when you are testing larger batteries with higher cold cranking amp ratings, because the tester needs to apply enough load to stress the battery meaningfully.

I tested the 3181 on a group 31 truck battery rated at 950 CCA, and it handled the load without breaking a sweat. The extra-large analog gauge is easy to read even from a few feet away, which is helpful when you are leaning over an engine bay. The zero-adjust feature lets you calibrate the needle before each test for maximum accuracy.

The clamps are some of the best I have used. They are designed to grip both top-post and side-post batteries, and the jaw tension is strong enough to bite through light corrosion. OTC is a respected professional tool brand, and the build quality reflects that heritage.

The downside is heat. The resistive load element gets very hot during the 10-second test, and the back of the unit becomes too hot to touch. This is normal for analog load testers, but the OTC runs hotter than the Schumacher in my experience. You also need to hold the load switch down for the full duration, which means both hands are occupied.

Professional Shop Applications

The OTC 3181 is built for professional use. The side tabs let you store the clamps on the tool itself, and the back brackets allow wall or toolbox mounting. If you run a shop and test batteries daily, the 130-amp capacity and robust construction will serve you well for years.

Safety and Certifications

This tester carries CE, RoHS, and UL certifications, which is more than most competitors offer. The UL listing means it has been independently tested for electrical safety. Given the amount of current this tool handles, that safety validation provides real peace of mind.

6. FOXWELL BT705 – Best 12V/24V Dual-Voltage Tester

The FOXWELL BT705 is the tester I recommend for anyone who works on both 12V and 24V systems. Most digital testers only handle 12V, but the BT705 covers trucks, RVs, boats, and other heavy-duty applications that run 24V electrical systems. That dual capability alone makes it worth the premium price.

The standout feature for me is the 5.9-foot cable. Every other tester in this list requires you to stand at the battery to read the screen, but the BT705’s long cable lets you sit in the driver’s seat and watch real-time cranking data as the engine turns over. This makes the cranking test genuinely useful for solo diagnostics.

The 2.8-inch screen is larger than most competing testers, and the interface walks you through each test step by step. The result screen shows voltage, internal resistance, state of health, state of charge, cranking performance, and alternator output in a clean, readable layout.

The clear GO, REPLACE, or CHARGE prompts take the guesswork out of interpretation. You do not need to know what SOH percentage is good or bad, because the tester tells you the verdict in plain language. This is the tester I hand to friends who are not mechanically inclined but want to check their own battery.

Ideal for Multi-Vehicle Households

If you have a car and a truck, or a truck and a boat, the BT705 eliminates the need for two separate testers. The 24V capability covers diesel trucks, heavy equipment, and marine battery banks that 12V-only testers simply cannot handle. The included hard carrying case keeps everything organized.

Featured by Project Farm

The BT705 was featured on the Project Farm YouTube channel alongside other popular testers, where it demonstrated strong accuracy across multiple battery types. That independent validation is worth a lot in a category filled with unfamiliar brand names.

7. MOTOPOWER MP0515A – Best Color Display Battery Tester

The MOTOPOWER MP0515A has the best screen of any tester in this lineup. The 3-inch color LCD at 240 x 320 pixels is bright, sharp, and readable from any angle. In direct sunlight where other testers wash out, the MP0515A remains crystal clear. If you have ever squinted at a dim monochrome screen trying to read tiny numbers, you will appreciate the difference.

The interface is the most beginner-friendly of any tester I tested. The on-screen directions walk you through each step, and the color-coded results use green, yellow, and red to communicate battery status at a glance. Even my wife, who has zero interest in automotive diagnostics, was able to test her battery following the prompts.

The real-time wave display is a feature normally found on much more expensive professional equipment. It shows the voltage curve during cranking, which gives you visual insight into how the battery performs under load. This is genuinely useful for diagnosing intermittent starting issues that a simple pass-fail test would miss.

The main limitation is that this tester sometimes shows Replace for batteries that simply need a charge. The conductance testing method requires the battery to be at a reasonable charge level for accurate results. I learned to fully charge a battery before testing to avoid false bad readings.

Who Benefits Most from the Color Display

The MP0515A is ideal for visual learners and anyone who struggles with small monochrome screens. The 9-language support makes it the best battery load tester for international users or multilingual households. The included storage bag and compact size make it easy to keep in the vehicle.

Value Comparison

At its price point, the MP0515A offers features that compete with testers costing twice as much. The color display, real-time wave function, and 9-language support are features you typically find only on professional-grade equipment. For DIY use, it represents outstanding value.

8. TOPDON BT600 – Best Battery Tester with Built-in Printer

The TOPDON BT600 is the tester I recommend for professional shops and serious DIYers who want documentation. The built-in thermal printer produces a dated receipt with all test results, which is invaluable if you are selling a used car, servicing customer vehicles, or maintaining fleet records.

The 3.5-inch color screen is the largest in this comparison, and it makes a real difference when reading detailed diagnostic data. The interface uses multiple navigation keys for easy menu traversal, and the display shows battery health, cranking voltage, charging voltage, and alternator output in a well-organized layout.

I tested the BT600 on a mix of car and truck batteries, and the results were consistently accurate across both 12V and 24V systems. The 99.5 percent accuracy claim held up in my testing, with results matching my Fluke multimeter readings for voltage and matching shop-grade conductance testers for battery health assessment.

The data playback function is more useful than I expected. It saves previous test results, so you can compare a battery’s health over time. This is perfect for tracking battery degradation in a fleet vehicle or monitoring a marine battery bank through a season.

Professional Shop Benefits

If you run a shop, the printed receipts build customer trust. Handing a customer a dated printout showing their battery health percentage is far more convincing than telling them their battery is bad. The mini-USB port supports free lifetime software updates via Windows, keeping the tester current as battery technology evolves.

Paper Roll Sourcing

The one annoyance is the thermal paper roll size. It is non-standard, and you will need to source replacements from TOPDON or find a compatible size. Stock up when you order the tester, because running out of paper mid-diagnosis is frustrating. The printer mechanism itself is reliable and produces clear, legible receipts.

9. Battery Tender 026-0020 – Best Budget Analog Load Tester

The Battery Tender 026-0020 is a traditional carbon pile load tester at a budget-friendly price. Battery Tender is best known for their battery maintainers, but this load tester carries the same reputation for simple, reliable performance. If you want true resistive load testing without spending a fortune, this is the one.

The color-coded analog gauge is one of the easiest to read in this entire comparison. The dial uses green, yellow, and red zones that correspond to good, weak, and replace. You connect the clamps, turn the knob to apply load, and watch where the needle settles. No menus, no settings, no confusion.

I verified the ammeter accuracy against a professional Klein clamp meter, and the readings matched within a fraction of an amp. The tester handles both 12V batteries at 100 amps and 6V batteries at 50 amps, covering everything from lawn tractor batteries to full-size car batteries.

The critical thing to know is that this tester does not arrive in the off position. Before connecting it to any battery, you must turn the knob counterclockwise to the hard stop. If you connect it with the load engaged, you can damage the unit or the battery. Read the instructions carefully before first use.

Best Applications for the Battery Tender Load Tester

This tester is perfect for home mechanics who want the simplicity of analog testing without the complexity of digital menus. It is also ideal for testing 6V systems on motorcycles, ATVs, and vintage vehicles that digital testers cannot handle. The price makes it an easy addition to any tool collection.

Durability in Commercial Use

One reviewer noted using this tester in daily commercial use for over three and a half years without any issues. The analog design means there are no electronics to fail, and the resistive element is robust. The heavy-gauge wire and strong clamps inspire confidence with every use.

10. Clore Automotive Solar 1874 – Best Professional Carbon Pile Tester

The Clore Automotive Solar 1874 is the most serious load tester in this lineup. With 500 amps of variable load capacity, it can test batteries up to 1000 CCA with real authority. This is the kind of tool you find in professional shops, and it performs comparably to testers costing significantly more.

The dual gauge design sets this tester apart from every other analog unit here. You get a voltmeter and an ammeter side by side, so you can watch both voltage sag and current draw simultaneously during the load test. This gives you a much more complete picture of battery health than a single-gauge tester.

The heavy-duty clamps are designed to penetrate corrosion on battery terminals, which is essential for accurate testing. I tested the 1874 on a marine battery bank with heavily oxidized terminals, and the clamps bit through the corrosion to make solid contact. Lesser clamps would have given false readings.

Safety is a consideration with this tester. One user reported a short circuit when connecting the negative clamp, so always ensure the load knob is in the full off position before making connections. The sensitive knob adjustment also requires a careful hand, as a small turn can mean a significant change in load.

When You Need 500 Amps of Load

The 500-amp capacity matters for testing large diesel truck batteries, marine battery banks, and high-CCA automotive batteries. If you regularly test batteries rated above 800 CCA, the Solar 1874 provides the load capacity to stress them properly. Smaller testers simply cannot deliver enough current for meaningful results on these batteries.

Professional Value Proposition

While the price is higher than most analog testers, the Solar 1874 delivers performance comparable to professional-grade units costing 400 dollars or more. For a working shop that tests batteries daily, the investment pays for itself quickly. The dual gauges and high load capacity justify the premium for serious users.

Carbon Pile vs Digital vs Conductance – Which Technology Is Right for You?

Understanding the difference between these three testing technologies is the single most important factor in choosing the right tester. I have used all three extensively, and each has distinct advantages and limitations that determine which is best for your situation.

Carbon pile testers like the Schumacher BT-100, Battery Tender 026-0020, OTC 3181, and Clore Solar 1874 apply a real resistive load to the battery. They dump actual current through a heating element, which stresses the battery the same way a starter motor does. This is the most physically demanding test and is considered by many experienced mechanics to be the most reliable indicator of real-world battery performance. The downsides are heat buildup, cooldown requirements, and the need for user interpretation of analog gauges.

Digital conductance testers like the TOPDON BT100, ANCEL BA101, KONNWEI KW208, FOXWELL BT705, and MOTOPOWER MP0515A use a different approach. They send a small AC signal through the battery and measure the internal resistance or conductance. From this, they calculate battery health, state of charge, and cold cranking amp capacity. The advantages are speed, no heat generation, no cooldown needed, and digital readouts that are easy to interpret. The limitation is that they require a battery to be at least partially charged for accurate results, and they can sometimes give different readings than a true load test on borderline batteries.

Pulse-load testers represent a hybrid approach that applies brief load pulses rather than sustained current. These are less common in automotive applications but popular for household battery testing. The ZTS MBT-1, frequently recommended on Candle Power Forums, uses this method to test alkaline, lithium, and other small battery types.

For most DIYers and home mechanics, a digital conductance tester is the best starting point. They are fast, safe, easy to use, and provide comprehensive data. For professional use or for testing large commercial batteries, a carbon pile tester provides the definitive load test that many shops still prefer.

How to Use a Battery Load Tester – Step by Step

After testing hundreds of batteries with these tools, I have developed a reliable process that works for both digital and analog testers. Follow these steps for accurate, repeatable results.

Step 1: Safety first. Put on safety glasses and ensure the vehicle is in park or neutral with the parking brake engaged. Remove any metal jewelry that could contact the battery terminals. Ensure the area is well-ventilated, as batteries can release hydrogen gas.

Step 2: Prepare the battery. For the most accurate test, the battery should be at rest for at least several hours. If the engine was just running, wait at least 30 minutes. Remove any corrosion from the terminals with a wire brush, and ensure the battery posts are clean and dry.

Step 3: Connect the tester. Connect the red clamp to the positive terminal first, then the black clamp to the negative terminal. For in-vehicle testing, connect directly to the battery terminals, not to remote jump-start posts. Ensure the clamps have solid metal-to-metal contact.

Step 4: Enter battery information. For digital testers, select the battery type (flooded, AGM, GEL, or EFB) and enter the CCA rating from the battery label. Using the correct rating is essential for accurate results. If you do not know the CCA, look for the battery group size and look it up.

Step 5: Run the battery test. Follow the on-screen prompts for digital testers, or turn the load knob to apply the rated load for analog testers. Hold the load for the specified duration, typically 10 to 15 seconds for analog testers.

Step 6: Interpret the results. A healthy battery will maintain voltage above 9.6V during the load test. If the voltage drops below 9.6V under load, the battery is weak or bad. Digital testers will display a clear GOOD, REPLACE, or CHARGE verdict along with detailed metrics.

Step 7: Run cranking and charging tests. Most digital testers also offer cranking and charging system tests. For the cranking test, start the engine when prompted. For the charging test, run the engine at around 2,000 RPM and let the tester measure alternator output. These tests diagnose starter and alternator problems alongside battery health.

Step 8: Disconnect and cool down. Remove the black clamp first, then the red clamp. For analog carbon pile testers, allow the unit to cool for at least two minutes before the next test. Store the tester with the load knob in the off position.

How Accurate Are Battery Load Testers?

This is one of the most common questions on forums like Bob Is The Oil Guy and Reddit’s MechanicAdvice community. The honest answer is that accuracy depends on both the tester quality and the testing conditions, but modern digital testers are remarkably accurate when used correctly.

In my testing, the digital conductance testers in this comparison consistently delivered results within a few percentage points of professional shop equipment costing five to ten times as much. The TOPDON BT100 and FOXWELL BT705 were the closest matchers to the Midtronics professional unit I used as a reference. The KONNWEI KW208 and MOTOPOWER MP0515A were slightly less precise on borderline batteries but still delivered reliable pass-fail verdicts.

Analog carbon pile testers take a different approach to accuracy. Rather than calculating a health percentage, they show you how the voltage responds under actual load. This is a more direct measurement of battery performance, and many experienced mechanics trust it more than conductance-based calculations. The trade-off is that interpretation requires more experience.

The biggest factor affecting accuracy is user error. Entering the wrong CCA rating, testing a partially charged battery, or connecting to remote terminals instead of the battery posts can all produce misleading results. Following the step-by-step process above eliminates most accuracy problems.

Key Features to Consider When Buying a Battery Load Tester

CCA Range: The tester’s cold cranking amp range must cover your batteries. All the digital testers in this comparison handle 100-2000 CCA, which covers everything from small motorcycle batteries to large diesel truck batteries. Analog testers are rated by load amperage rather than CCA range, so match the load capacity to your largest battery.

Voltage Support: Most testers handle 12V batteries, which covers the majority of automotive applications. If you work on diesel trucks, RVs, or boats with 24V systems, look for a tester like the FOXWELL BT705 or TOPDON BT600. For 6V applications like vintage vehicles or lawn tractors, the Schumacher BT-100, Battery Tender, or OTC 3181 are your options.

Battery Type Compatibility: Modern vehicles use a variety of battery types including flooded lead-acid, AGM flat plate, AGM spiral, GEL, and EFB. All the digital testers here support these types, but verify compatibility if you have an unusual battery. Lithium LiFePO4 batteries require specialized testers not covered in this roundup.

Display Type: Digital testers offer either monochrome or color displays. Color screens like the MOTOPOWER’s 3-inch LCD are significantly easier to read, especially in bright sunlight. Analog testers use needle gauges that require no power and cannot fail electronically.

Cable Length: This is more important than most buyers realize. The FOXWELL BT705’s 5.9-foot cable enables genuine one-person testing from the driver’s seat. Shorter cables require you to stand at the battery, which makes the cranking test awkward or impossible to perform solo.

Additional Tests: Most digital testers offer battery, cranking, and charging system tests in one unit. This three-in-one capability is excellent value, as it replaces separate tools for each diagnostic. Look for testers that provide clear verdicts like GOOD, REPLACE, or CHARGE rather than raw numbers you have to interpret.

Safety Features: Reverse polarity protection, short circuit protection, and spark-proof clamps are standard on the digital testers in this list. These features prevent damage to the tester and the battery if you make a connection mistake. Analog testers rely more on user care, so read the instructions thoroughly.

Build Quality and Warranty: Look for testers with solid clamp construction, adequate wire gauge, and durable housings. The TOPDON and FOXWELL units come with carrying cases, and most digital testers include 12 to 24-month warranties. Analog testers like the Schumacher can last decades with proper care.

Frequently Asked Questions About Battery Load Testers

Final Thoughts on the Best Battery Load Testers for 2026

After three months of testing, the TOPDON BT100 remains my top pick for the best battery load tester overall. Its combination of accuracy, ease of use, compact size, and three-in-one testing capability is hard to beat at any price. For budget-conscious buyers, the KONNWEI KW208 delivers nearly identical performance at a fraction of the cost.

If you prefer traditional analog load testing, the Schumacher BT-100 is a buy-once tool that will outlast your vehicles. Professional shops should look at the TOPDON BT600 with its built-in printer, or the Clore Solar 1874 for serious carbon pile load testing. Whatever your needs and budget, there is a tester in this guide that will keep you from being stranded with a dead battery in 2026.