What size solar panel do I need for a 150Ah 12V battery?

You need approximately 378W of solar panels for a lithium (LiFePO4) battery, 424W for an AGM battery, or 450W for a flooded lead-acid battery. These figures assume 5 peak sun hours per day. A 400W array is the practical minimum for lithium.

Can a 200W solar panel charge a 150Ah 12V battery?

A 200W panel can charge a 150Ah 12V lithium battery, but not in one day of typical sunshine. At 5 peak sun hours, 200W delivers about 1,000Wh -- roughly 56% of the 1,800Wh needed. It would take about two sunny days to reach a full charge from empty. For daily full charging, 400W is the minimum.

How many 100W panels do I need for a 150Ah 12V battery?

Four 100W panels (400W total) will charge a 150Ah 12V lithium battery in about 5 peak sun hours. Three panels (300W) can do it in about 6.5 hours. If you are in a high-sun area with 6 or more peak sun hours, three panels may be sufficient.

What charge controller do I need for a 150Ah 12V battery?

For a 400W array on a 12V system, you need a controller rated for at least 42A (400W / 12V x 1.25 = 41.7A). A 50A MPPT controller is the standard choice. A 40A MPPT works if your array is 360W or less.

How long does it take to charge a 150Ah 12V battery with 400W of solar?

With lithium chemistry and an MPPT controller, 400W of solar charges a 150Ah 12V battery in about 5 peak sun hours. With AGM, expect about 5.5 to 6 hours. Real-world conditions (temperature, angle, shading) typically add 15 to 25 percent to these times.

Is 150Ah enough for an RV?

A 150Ah 12V lithium battery provides 1,800Wh of usable energy, enough to run RV lights, a 12V fridge, phone and laptop charging, water pump, and a vent fan for a full day of typical use. For air conditioning or high-wattage appliances through an inverter, consider 200Ah or larger.

Should I get one 150Ah battery or two 100Ah batteries?

A single 150Ah battery is simpler -- fewer connections, no balancing concerns, and less space. Two 100Ah batteries in parallel give you 200Ah total and offer redundancy (if one fails, you still have 100Ah). For most users, a single battery in the right capacity is the better choice.

What Size Solar Panel to Charge a 150Ah 12V Battery? (Calculator + Chart)

A 150Ah 12V battery stores 1,800Wh of energy and needs roughly 378W of solar panels with lithium chemistry, 424W with AGM, or 450W with lead-acid to charge fully in 5 peak sun hours. A 400W array -- two 200W panels or four 100W panels -- is the practical recommendation for this battery size.

Quick answer and calculator

A 150Ah 12V lithium (LiFePO4) battery stores 1.80 kWh. Accounting for 95% charging efficiency, you need to deliver approximately 1,895Wh from your panels. At 5 peak sun hours, that equals 378W.

AGM at 85% efficiency requires 424W, and flooded lead-acid at 80% efficiency requires 450W.

Battery voltage

Battery capacity

Battery chemistry

Target charge time

hrs

Required solar panel size

To charge a 100Ah 12V Lithium (LiFePO4) battery in 5 hours

Energy to charge

1.26kWh

If you use 100W panels

panels needed

If you use 200W panels

panels needed

171 kg

CO₂ avoided per year

0.04

equivalent US homes powered

trees planted equivalent

$74

estimated annual savings

Chemistry	Efficiency	Cycle Life	Panel Watts
Lithium (LiFePO4)	95%	3,000–5,000	252 W
Deep Cycle AGM	85%	500–1,000	283 W
Lead-Acid Flooded	80%	300–500	300 W

Tap to see sensitivity analysisSensitivity analysis

Sensitivity range
Scenario	Value
Low (-20%)	202 W
Expected	252 W
High (+20%)	302 W

Battery chemistry has the biggest effect \u2014 switching from lead-acid to lithium reduces required panel watts by ~20%.

What size battery do I need?See production for your state

Sizing table by charge time and chemistry

Charge Time	Lithium (LiFePO4)	Deep Cycle AGM	Lead-Acid Flooded
4 hours	474W	529W	563W
5 hours	378W	424W	450W
6 hours	316W	353W	375W
8 hours	237W	265W	281W
10 hours	189W	212W	225W

These figures include chemistry-specific efficiency losses and assume panels produce their rated wattage during peak sun hours at STC conditions.

Which solar panel to buy

For a 150Ah 12V battery, you need 380W to 450W of solar. Here are the best configurations:

2 x 200W panels (recommended) -- Two 200W panels totaling 400W is the most balanced setup. It charges a lithium battery in about 5 peak sun hours and fits on most RV roofs or ground mounts. Wire them in parallel for 12V compatibility with either PWM or MPPT controllers.

4 x 100W panels -- Four 100W panels (400W total) offer maximum flexibility. Use parallel wiring for PWM controllers, or two series strings of two panels in parallel for MPPT. The smaller panel size fits around roof vents, antennas, and other obstacles on RVs and boats.

1 x 400W panel -- A single large 400W panel minimizes wiring and connections. Modern 400W panels are about 1.7m x 1.1m and weigh 20 to 22 kg. Good for ground mounts or dedicated roof areas. Requires an MPPT controller since the panel's Vmp (around 36 to 41V) significantly exceeds the 12V battery voltage.

2 x 100W panels (minimum for high-sun areas) -- In the southwestern US where you get 6 to 7 peak sun hours, 200W can charge a lithium 150Ah battery in about 10 hours (effectively two days). This only works if you do not deplete the battery daily.

Charge controller sizing

The 150Ah 12V system operates at relatively high currents, making proper controller sizing critical:

400W array: 400W / 12V x 1.25 = 41.7A. You need a 50A controller. A 40A MPPT controller may work if you wire panels in series at higher voltage, since the MPPT converts voltage to current on the battery side.

300W array: 300W / 12V x 1.25 = 31.3A. A 40A controller handles this with margin.

200W array: 200W / 12V x 1.25 = 20.8A. A 30A controller is sufficient.

For 400W on a 12V system, the high current (33A at battery voltage) means MPPT is the clear winner. Wiring two 200W panels in series (about 36V Vmp) halves the input current to the controller and reduces cable losses. The MPPT controller converts this to the appropriate battery charging voltage and current.

MPPT vs PWM for a 150Ah 12V system

At 400W on 12V, the MPPT advantage becomes significant:

PWM at 400W/12V: Four 100W 12V-nominal panels in parallel. Each panel's Vmp of 18V is clamped to about 14.4V battery voltage, wasting about 20% of the voltage potential. Effective power delivery: roughly 320W. You also need thick cables to handle 28A or more from the array.

MPPT at 400W/12V: Two 200W panels in series at 36V Vmp, drawing about 11A. The MPPT controller converts to about 28A at 14.4V battery voltage, delivering roughly 380 to 400W effective. Lower array current means thinner, cheaper cables.

The MPPT advantage at this system size is 20 to 25%, which translates to about an hour faster charge time each day. An MPPT controller in the 40A to 50A range costs $80 to $150, easily justified by the performance gain.

Series vs parallel for multiple panels

For a 150Ah 12V battery with four 100W panels:

All parallel (PWM-compatible) -- All four panels at 18V Vmp, combined 22A Imp. Simple wiring, good shade tolerance (one shaded panel does not affect others), but requires thick cables and a large controller. Works with PWM or MPPT.

2S2P (two series strings in parallel, MPPT recommended) -- Two pairs of panels in series (36V each, 5.5A each), pairs in parallel (36V, 11A combined). Halves the cable current. Best overall configuration for MPPT controllers.

All series (MPPT only) -- Four panels in series at 72V Vmp, 5.5A. Very low cable current, thinnest possible cables. But one shaded panel drags down the entire string. Only use this in shade-free installations.

For two 200W panels, wire them in series (36V, 11A) for MPPT or in parallel (18V, 22A) for PWM. Series is preferred with MPPT.

Real-world factors that reduce output

At 400W of solar, expect these real-world reductions:

Temperature -- Solar panel output drops 0.3 to 0.5% per degree C above 25 degrees C. At 65 degrees C cell temperature, your 400W array produces 320 to 352W.

Panel angle -- Flat-mounted panels produce 10 to 25% less than optimally tilted panels. For a 150Ah 12V system on an RV, consider portable tilt brackets for campsite use -- the 30 to 60W gain is meaningful at this battery size.

Shading -- Position panels to avoid shadows during the 10 AM to 3 PM window. With parallel wiring, shading affects only the shaded panel. With series wiring, use panels with bypass diodes to minimize the impact.

Wire sizing -- For 30A or more at 12V, use 8 AWG wire for runs under 10 feet and 6 AWG for longer distances. Undersized wire wastes energy as heat and can be a fire hazard.

Plan with a derating factor of 0.80 to 0.85. A 400W array effectively delivers 320 to 340W in typical real-world conditions.

Depth of discharge and usable capacity

Lithium (LiFePO4) -- 80 to 100% DOD gives 120 to 150Ah usable (1,440 to 1,800Wh). This is enough to run an RV overnight with lights, fridge, electronics, and a vent fan.

AGM -- 50% DOD gives 75Ah usable (900Wh). To get the same usable energy as 150Ah lithium, you would need a 300Ah AGM bank -- twice the weight and size.

Flooded lead-acid -- 50% DOD gives 75Ah usable. Additionally, lead-acid requires equalization charges every 30 to 90 days and periodic water topping, adding maintenance burden.

A 150Ah lithium battery weighs about 14 to 18 kg. An equivalent 300Ah lead-acid bank weighs 80 to 90 kg. For mobile applications (RVs, boats, vans), the weight savings alone justify the lithium premium.