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12V 50Ah Lithium Battery for Forward-Facing Sonar: PGLM50 Guide
Short answer: The Pro-Guide PGLM50 is a 12V 50Ah lithium battery (12.8V nominal LiFePO4) that stores 640 watt-hours, weighs 14 lb and measures just 7.75 x 6.5 x 6.9 in. With a 50A continuous discharge rating, an IP65 case and 3,000 cycles at 100% depth of discharge, it is a compact dedicated battery for forward-facing sonar and fish finders, and it can also power a kayak trolling motor.
Forward-facing sonar changed how anglers fish, and it changed what they need from a battery. These units want clean, steady voltage all day, and they work best on a battery that is not shared with the trolling motor or engine. This guide explains why a 12V 50Ah lithium battery is a popular choice for a dedicated electronics battery, how long it runs common setups, how it compares with AGM, how to charge and mount it, and how it stacks up against Pro-Guide's U1 and Group 24 options.
Key Takeaways
- Compact electronics battery: 50Ah and 640Wh in a 7.75 x 6.5 x 6.9 in case that weighs 14 lb (6.4 kg).
- Clean, steady voltage: LiFePO4 holds its voltage until nearly empty, which is what sonar and graphs want.
- Headroom: 50A maximum continuous discharge, with protection against over-charge, over-discharge, over-current, over-temperature and short circuit.
- Built for the boat: IP65 rated case and self-discharge under 2% per month.
- Long life: 3,000 cycles at 100% depth of discharge, 6,000 at 80%, with a 5-year free replacement and 10-year pro-rata warranty.
- Proven by anglers: the PGLM50 holds a 5-star average across its customer reviews, many from anglers running forward-facing sonar.
Why Use a 12V 50Ah Lithium Battery for Electronics?
Modern fish finders and forward-facing sonar are high-powered computers. When they share a battery with a trolling motor or an outboard, voltage dips and electrical noise can show up as screen interference, slow redraws or units that reset. Running electronics on their own battery isolates them from those loads. Our article Should You Run a Separate Battery for Your Boat Electronics? explains the why in detail.
The question then becomes which battery. A full-size Group 31 is often more capacity and weight than an electronics circuit needs. A 12V 50Ah LiFePO4 battery hits the middle: enough energy for a long tournament day on one or two graphs plus forward-facing sonar, in a case small enough to tuck under a console or helm. LiFePO4 adds the flat voltage curve, so your units see steady power until the battery is nearly empty, and the cycle life to do it for thousands of trips.
The PGLM50 is a deep cycle battery. It is built to deliver steady current over hours, not to crank an engine.
Pro-Guide PGLM50 Specifications
| Model / SKU | Pro-Guide PGLM50 |
| Chemistry | Lithium iron phosphate (LiFePO4) |
| Nominal voltage | 12.8V |
| Capacity / energy | 50Ah / 640Wh |
| Cycle life | 3,000 cycles at 100% DoD, 6,000 at 80% DoD |
| Discharge current | 10A standard, 50A maximum continuous |
| Discharge cut-off | 10V |
| Charge current | 10A standard, 50A maximum |
| Charge voltage | 14.6V (±0.2V) |
| Charging temperature | 32°F to 131°F (0°C to 55°C) |
| Discharge temperature | -4°F to 140°F (-20°C to 60°C) |
| Self-discharge | Less than 2% per month |
| Protection | IP65 plastic case; over-charge, over-discharge, over-current, over-temperature and short-circuit protection; cell balancing |
| Terminals | Internal thread (M6) |
| Bluetooth | Enabled |
| Dimensions | 7.75 x 6.5 x 6.9 in (196.9 x 165.1 x 175.3 mm) |
| Weight | 14 lb (6.4 kg) |
| Warranty | 60-month free replacement, 120-month total pro-rata |
Want the full numbers? Download the PGLM50 data sheet (PDF).
The PGLM50 packs 640Wh into a 7.75 x 6.5 x 6.9 in case, small enough to mount under a console or helm.
How Long Will a 12V 50Ah Lithium Battery Run Forward-Facing Sonar?
Divide 50Ah by the total draw of everything on the battery. Draw varies a lot between brands, screen sizes and how many units you run, so add up the current ratings in your manuals (divide watts by 12 to get amps).
| Load | Total draw | Estimated runtime on the PGLM50 |
| Single fish finder | About 2A | About 25 hours |
| Graph plus forward-facing sonar | About 5A | About 10 hours |
| Two graphs plus forward-facing sonar | About 10A | About 5 hours |
| Kayak trolling motor | About 20A | About 2.5 hours |
These are rough estimates; real runtime depends on the load, temperature and how far you discharge the battery. Customer experience lines up well with the math. One tournament crappie team runs two PGLM50s to power two Garmin LiveScope units and two Garmin 122SV graphs. Another angler runs forward-facing sonar off a PGLM50 in his Skeeter and calls the performance flawless. A kayak angler reported getting two days of fishing on a single charge.
If your total draw is higher than 10A, or you want multiple days between charges, consider two PGLM50s in parallel (the label allows up to 3) or a larger battery like the 100Ah 24M100.
50Ah Lithium vs. AGM for Boat Electronics
| Factor | Pro-Guide PGLM50 (LiFePO4) | Typical AGM electronics battery |
| Usable capacity | Nearly all of 50Ah | About 50% of rated capacity |
| Weight | 14 lb | Typically several times heavier for the same usable energy |
| Voltage under load | Stays flat until nearly empty | Sags as it discharges, which can cause screen issues and resets |
| Cycle life | 3,000 at 100% DoD | Typically a few hundred cycles |
| Self-discharge | Less than 2% per month | Usually higher |
| Warranty | 5-year free replacement, 10-year pro-rata | Usually 1 to 3 years |
For electronics, the flat voltage curve is the headline. As an AGM battery drains, its voltage drops, and sonar units can respond with noise, dimming or low-voltage shutdowns late in the day. A LiFePO4 battery like the PGLM50 keeps the voltage up until it is nearly empty, so the picture at 4 p.m. looks like the picture at launch.
What Is the PGLM50 Best For?
- Dedicated forward-facing sonar and graph battery: the most common use, and the one our reviewers describe most.
- Tight bass and pontoon boats: one owner of an 18 ft pontoon-style bass boat mounted the PGLM50 under the helm next to his 36V trolling motor battery bank for a clean, single-location install. He noted the two discharge at about the same rate, typically within 5% of each other, so he charges everything on the same schedule.
- Kayaks: 640Wh runs a full electronics setup for a day or more, and the 50A continuous rating supports a kayak trolling motor. The 12 Volt Trolling Motor Kit with On-Board Charging Connection Kit simplifies the wiring.
- Light RV, camping and solar storage: 640Wh with low self-discharge for intermittent use.
Prefer a one-box solution? The 12V 50Ah LiFePO4 Deep Cycle Battery Bundle pairs one PGLM50 with the Pro-Guide PGC-110 1-bank charger for a single-screen setup.
The PGLM50's top label lists its charging limits (10A standard, 50A maximum) and how many batteries can be wired together.
How to Charge a 12V 50Ah LiFePO4 Battery
Charge time is roughly 50Ah divided by the charger output:
- 10A standard: about 5 hours from empty, for example with the Pro-Guide 12V 10A 1-Bank Battery Charger on its lithium profile. Multi-bank versions like the 12V 10A 2-Bank Battery Charger let you charge your electronics battery alongside another 12V battery.
- 30A: about 1.7 hours from empty with the Pro-Guide 12V 30A Lithium Battery Charger.
- 50A maximum: about 1 hour from empty.
Follow the rules on the battery label and spec sheet:
- Use a smart lithium charger set between 14V and 15V. Pro-Guide specifies a 14.6V (±0.2V) charge voltage. Never exceed 15V.
- No desulfation mode. Do not use a charger with an automatic desulfation function.
- Charge between 32°F and 131°F. The PGLM50 can discharge down to -4°F, but let it warm up before charging after a cold morning.
- Don't run it below 12V. The label warns that discharging below 12V may damage the battery. The built-in protection cuts off at 10V; recharge promptly if that happens.
- Check after resting. Wait 1 to 2 hours after charging; if the voltage is below 12.8V, it needs more charging.
Mounting and Wiring Tips
Measure first: it is not a group size
The PGLM50 is 7.75 x 6.5 x 6.9 in and does not use a standard group-size case. Measure your space, including clearance above the terminals. As one reviewer put it, you may need to get creative with mounting in a tight boat.
Use the PGLM50 hold-down kit
Because it is not a standard case, a dedicated hold-down is the cleanest way to secure it. The PGLM50 Hold Down Kit keeps the battery from shifting or vibrating loose on rough water.
Wire your electronics cleanly
Clean power delivery matters as much as the battery. The Bass Tank Power Harness is a single-run electronics wiring kit designed to deliver consistent voltage to your graphs. Fuse the positive lead close to the battery and use M6 bolts with properly sized ring terminals.
Know the series and parallel limits
The label allows no more than 3 PGLM50s in parallel and no more than 4 in series. Use matched batteries at the same state of charge.
Keep it out of standing water
IP65 means dust-tight and protected against low-pressure water jets, not immersion. Mount it high and dry.
Monitor it from your phone
Bluetooth is listed as enabled on the PGLM50, and the product page links to the Pro-Guide Power iOS app.
PGLM50 vs. PGLM46 and 24M100: Which Should You Choose?
| Spec | PGLM46 | PGLM50 | 24M100 |
| Capacity / energy | 46Ah / 588Wh | 50Ah / 640Wh | 100Ah / 1,280Wh |
| Case | Group U1 | 7.75 x 6.5 x 6.9 in | Group 24 |
| Weight | 10.14 lb | 14 lb | 23.8 lb |
| Rated for | Electronics and light loads | Electronics, FFS, kayak motors (50A continuous) | Trolling motors and large electronics setups (100A continuous) |
Choose the PGLM46 if you need to fit an existing Group U1 box. Choose the PGLM50 for a compact, dedicated forward-facing sonar and graph battery with an IP65 case and 50A continuous rating. Choose the 24M100 if you need twice the capacity or want to build a 24V or 36V trolling motor bank; see our Group 24 lithium battery guide.
Frequently Asked Questions
Is a 12V 50Ah lithium battery enough for forward-facing sonar?
For most single-angler setups, yes. The Pro-Guide PGLM50 runs a graph plus forward-facing sonar drawing about 5A for roughly 10 hours. Add up your units' draw to confirm.
How long will the PGLM50 run a fish finder?
About 25 hours on a 2A fish finder and about 5 hours on a 10A electronics load. Actual runtime depends on the load and temperature.
How big is the PGLM50?
The PGLM50 measures 7.75 x 6.5 x 6.9 in (196.9 x 165.1 x 175.3 mm) and weighs 14 lb. It is not a standard group size, so measure your space before you buy.
Can the PGLM50 run a kayak trolling motor?
Yes. It is rated for 50A continuous discharge. A kayak trolling motor drawing about 20A runs for roughly 2.5 hours on one charge.
How long does it take to charge the PGLM50?
About 5 hours from empty at the 10A standard charge current, or about 1 hour at the 50A maximum. Use a LiFePO4 charger with a 14.6V charge voltage.
Is the PGLM50 waterproof?
It is IP65 rated: dust-tight and protected against low-pressure water jets. It is not rated for immersion, so mount it out of standing water.
How many cycles does the PGLM50 last?
The PGLM50 is rated for 3,000 cycles at 100% depth of discharge and 6,000 cycles at 80%, and is backed by a 10-year pro-rata warranty.
Power Your Electronics with the PGLM50
If you want clean, steady power for forward-facing sonar and graphs without hauling a full-size battery, the Pro-Guide PGLM50 delivers 640Wh of LiFePO4 energy in a 14 lb, IP65 package, with 3,000 cycles at 100% depth of discharge and a 10-year warranty. Tournament anglers and kayakers already trust it to keep their screens lit from launch to weigh-in.
Planning an electronics setup? Call our team at 1-800-827-3232 or browse all lithium batteries and battery and charger kits.
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