How To Charge 24 Volt Batteries With Solar Panels?

Because off-grid solar panels are often set up for a 12 volt charging system, if you have a 24 volt battery system, you’ll need to connect two panels in series or purchase a single high voltage solar panel to create enough energy to charge the battery.

Can 12 volt solar panels be used on a 24 volt system?

A 12V solar panel should typically be used with a 12V battery, whereas a 24V solar panel should be used with a 24V battery. A key aspect to remember is that while a 24V battery is not currently available on the market, you may make one by connecting two 12V batteries in series.

To charge a 24 volt battery, how many watts do I need?

So we’ll need roughly 700 watts of solar panels to supply enough electricity to our 24 volt battery (assuming 5.5 sun hours per day). To put it another way, to charge this deep charge battery, we’ll need seven 100-watt solar panels.

To charge a 24 volt battery, how many amps do I need?

Because 24 volt charger technology has kept up with the technological change, current battery charging philosophy employs microprocessor-controlled charging patterns in three stages (or two or four stages).

These are “smart chargers,” and high-quality models are rarely available in bargain retailers.

Bulk, absorption, and float are the three stages or steps in lead acid battery charging (or sometimes complete shut off in some cases). Qualification, or equalization, is often seen as a separate stage, generally for commercial reasons. The bulk and float stages will be found in a two-stage unit. To maintain battery capacity and service life, follow the charging processes and voltages recommended by the battery manufacturer, or use a high-quality microprocessor-controlled charger.

The earlier 24 volt charger had a fixed charging voltage that was high enough to “push” energy into the battery (amps).

The easier this forcing process is, the lower the initial battery voltage (state of discharge), therefore you may see the amp meter (if provided) run up to the charger’s maximum output amperage and stay there for a time.

The tougher it is for the 24 volt charger to drive the amps in as the battery voltage rises, as it happens when the state of charge climbs, therefore the amp rate lowers. When the charger’s output voltage can no longer force any more into the battery, current practically ceases. However, depending on where this voltage threshold is, it may be high enough to overcharge the battery over time, or keep it in the gassing stage, drying out a flooded type battery. For this reason, these chargers should be closely watched and disconnected when the amp meter reaches the lowest setting. Some of these older technology devices feature timers, which, depending on the setting and battery charge status at the start of the charge, may result in overcharging if left on too long or undercharging if left on too short. Overcharging damages batteries more quickly than undercharging. Undercharging causes sulphation to build up on the plates and eventually harden, reducing battery capacity.

The “smart chargers” are designed with today’s charging philosophy in mind, and they also use data from the battery to deliver maximum charge benefit with minimal monitoring.

The microprocessor enables for a complete charge cycle without the need for a timer, and it does not undercharge or overcharge, allowing for appropriate battery management and maximum battery life when used regularly.

True Gel batteries require a specific charge profile, which necessitates the use of a gelspecific, gel selected, or gel appropriate charger.

Gel batteries have a peak charging voltage of 2.3 to 2.36 volts per cell, which translates to 27.6 to 28.3 volts for a 24 volt charger, which is less than a wet or AGM battery requires for a full charge.

When the voltage in a Gel battery is exceeded, bubbles form in the electrolyte gel, resulting in lasting damage because the bubbles do not disperse when the over voltage condition is removed.

Three Stage Battery Charging

With a 24 volt charger, the BULK stage accounts for around 80% of the recharge, during which the charger current is held constant (in a constant current charger) while the voltage rises. A properly sized charger will provide the battery with as much power as it can handle up to chargercapacity (25 percent of battery capacity in amp hours), while not raising a wet battery beyond 125 degrees Fahrenheit or an AGM or GEL (valve regulated) battery above 100 degrees Fahrenheit. For AGM or some flooded batteries, the target voltage for a 24 volt charger is 2.4 to 2.45 volts per cell, or 28.8 to 29.4 volts.

The AGM/flooded 24 volt charger’s ABSORPTION stage (about the final 20%) involves the charger holding at the absorption voltage (between 28.8 VDC and 29.4 VDC, depending on charger set points) and gradually decreasing the current until the batterypack is fully charged.

The battery pack may have some permanent sulphation if it won’t keep a charge or the current doesn’t diminish beyond the specified recharge period.

The charge voltage is dropped to roughly 2.25 volts per cell, or around 27.0 VDC, and held constant in the FLOAT stage, while the current is reduced to less than 1% of battery capacity.

This mode can be used indefinitely to keep a fully charged battery pack. Instead of maintaining a float voltage, some chargers turn off and monitor the batteries, commencing a charge cycle if necessary.

Divide the amp hours to be replaced by 90 percent of the charger’s rated output to get an estimate of how long it will take to recharge.

A 100 amp hour battery with a 10% discharge, for example, would require 10 amps to be replaced.

With a 5 amp 24 volt charger, the estimated recharge time is 10 amphours/(.9×5) amps = 2.22 hours. A battery that has been deeply drained deviates from this formula, needing more time to replace per amp.

Experts differ in their suggestions for how often you should recharge.

It appears that the depth of drain has a greater impact on battery life than the frequency with which it is recharged.

Lead acid batteries, even sealed varieties (AGM and Gel), prefer to be maintained fully charged as much as feasible.

Recharging when the equipment is not going to be utilized for a while (for example, during a mealbreak or whatever) can keep the average depth of discharge over 50% for a serviceday.

This primarily applies to battery applications when the average depth of discharge per day is less than 50% and the battery may be fully recharged once per day, such as in a mobility or industrial application. This is referred to as “opportunity charging.”


Equalization is essentially a charge that may be managed. Although some charger manufacturers refer to the peak voltage reached by the charger at the end of BULK mode (absorptionvoltage) as an equalization voltage, it is not strictly correct. This approach can benefit higher capacity wet(flooded) batteries, especially those that are physically tall. If a wet battery is not cycled on a regular basis, the electrolyte might stratify over time. In equalization, the voltage is raised over the typical peak charging voltage (to 15 to 16 volts in a 12 volt charger) and kept for a set (but limited) period deep into the gassing stage. This stirs up the chemistry throughout the battery, “equalizing” the electrolyte’s strength and removing any free sulphation on the plates.

The design of sealed batteries (AGM and Gel) virtually eliminates stratification, and almost all makers of these batteries advise against it (advising against it). Although certain manufacturers (particularly Concorde) provide a technique, it is vital to follow the voltage and time parameters to avoid battery damage.

Volt Charger Sizes

A low milliamp output (100, 200, 500 milliamps), up to 40 or 50 amps, 24 volt charger that plugs into a 115 volt power outlet is available (chargers above about 30 amps usually require a 20 amp circuit, so check). Some of the smaller components, like antique chargers, are unregulated and merely have a fixed voltage output. These take a long time to charge and should be avoided if at all feasible. Smaller amp capacities are suited for smaller batteries, such as those used in electrical and security applications that require between 1.3 and 12 amp hours. They can also be used to maintain larger batteries. A medium amp output 24 volt charger would be in the 15 to 20 amp range, and could be used for a variety of applications requiring 100 amp hours of battery or more, as well as applications requiring a consistent amp load (power supply application). To protect the charger from moving back into the boost or bulk stage in a power supply situation, the constant draw should be a small percentage of the charger maximum amp capacity, or the charger should have selectability for the power supply or”battery with load” mode. The larger components of the 24 volt charger versions have an output of roughly 25 to 40 amps (except commercial, 220 VAC input types, or 3 phase). These are utilized in battery banks with a lot of amp hours or in applications that need to recharge quickly (possibly at the expense of maximum battery life). When a generator is employed as the AC power source, the larger units are sometimes utilised, and generator run time is taken into account.

The charger should be roughly 25% of the battery capacity (ah = amp hour capacity), according to most battery manufacturers.

A 25 amp 24 volt charger would be required for a 100 ah 24 volt battery pack (or less).

Larger chargers can shorten charging times, but they can also shorten battery life.

Smaller chargers are fine for long-term floating, such as a 1 or 2 amp “smart charger,” but they would be inefficient or burn up if used to bulk charge large capacity, deeply drained batteries.

Is it possible to charge a 24V battery with a solar panel?

Although a 12V solar panel can charge a 24V battery, it will not be as efficient as a 24V panel. The battery will take longer to charge since the 12V solar panel cannot output as much electricity as a 24V solar panel.

An MPPT charge controller is the best technique to charge a 24V battery with a 12V solar panel. To get the most out of your solar panel, the MPPT charge controller will help regulate the electricity by regulating the voltage and current.

Is it possible to connect a solar panel directly to a battery?

A solar panel can be connected directly to a 12 volt automobile battery, but if the power output is greater than 5 watts, it must be monitored. Solar panels with a power rating greater than 5 watts must be linked to a battery via a solar charge controller to avoid overcharging.

In my experience, theory rarely stands up to real-world testing, so I’ll connect a solar panel directly to a partially depleted deep-cycle lead-acid battery and use a solar charge controller to compare voltage and current. Go straight to the test results.

Before that, I’ll go over some theory learning is beneficial because it clarifies things!

What is the best way to charge a 24 volt battery?

Connect a jumper cable to the second battery’s negative (“-,” “NEG,” or “GND”) terminal. Connect the negative (“-,” “NEG,” or “GND”) post of the battery charger to the jumper wire with the alligator clip at the end of the wire. Connect the battery charger. Switch on the battery charger and set the charge rate to 20 amps.

To charge a 24V 200AH battery, how many solar panels do I need?

Before we can answer this query, we need a little more information on the battery. Will the battery be totally depleted despite its 200Ah capacity?

This would be exceedingly odd I don’t recall ever completely depleting a battery. Although some lithium-based batteries can be discharged to zero, allowable discharge levels vary by battery type and design.

Because lead-acid batteries are the most prevalent high-power battery in use currently, I’ll base my response on that.

In general, assuming 4 peak-sun-hours per day, a 200Ah lead-acid deep-cycle battery would require a 300 watt solar panel to fully recharge from 50% depth of discharge (DOD). With a clear sky, charging might be completed in one day.

For a 24V converter, how many solar panels do I need?

You’ll need at least 1 x 120-watt solar panel to charge a 200AH 24V battery at its C/20 rate of 5 amps current for 24 hours. Given that your solar panel’s peak output may not always be available, you’ll need to double that figure by two or three to charge a 24v battery efficiently.

Is it possible to charge a 24 volt system using a 12 volt charger?

One factor that deters consumers from switching to a more efficient 24v system is the difficulty and cost of finding 24v chargers. As a result, how can we charge a 24V battery from a 12V source? The circuit below demonstrates how to set up switching such that two 12v batteries can be linked in series to provide 24v while being charged in parallel by a 12v charger.

For a 24v system, two 12v automobile relays are utilized. These relays have a continuous current rating of 30 amps. Of course, instead of two single pole relays, you might use a single double pole relay, but they are rarely available with more than a 10 amp rating. Most controllers in this application will be fine with the 30 amp relays we recommend because they have contacts capable of supporting far over 100 amps for short periods of time.

Consider the system that runs on 24 volts. The two batteries are linked in series through the typically closed connections when the relays are not in use (solid black). When both relays are turned on, the batteries are connected in series. The relays are controlled by a third contact, B, and are automatically energized when the 12v charger is connected.

It may be tempting to connect the NC contacts in parallel rather in series, as shown below, to improve current handling; however, there is a risk that if a relay contact becomes stuck, one battery will be shorted out, destroying the other relay as well.

With this arrangement, you must ensure that the 24v (or 36v) that will be applied to the 12v charger for a brief period of time will not damage it. Alternatively, you can arrange for contacts B and C to make contact first, thereby energizing the relays before connecting the charger.

Other configurations of this system are available; for example, this diagram depicts a 36v system with four relays.

Which is preferable, a 12v or a 24v solar system?

On 24V or 48V, you can buy significantly larger inverters than on 12V. There are several benefits to using a higher DC supply voltage.

– For every given load, reduce DC current by half and losses by a quarter. Reduced chance of a fire.

– Improved input control. At 12 volts, a 0.5 volt line drop is a 4.6 percent supply drop, whereas a 0.25 volt line drop equals a 1.04 percent supply drop.

– Increased efficiency and regulation of inverters. i.e. there are fewer losses while changing to 240 VAC. Inverters don’t have to work as hard to maintain a consistent AC output.

– Batteries have a larger useful operating voltage window (for acceptable DOD).

A quality 24 volt inverter would suffice up to 3kW of maximum demand. The rule of thumb is that the inverter’s maximum current demand should not exceed 120-140 amps. If your power consumption exceeds 3 kW, you should consider a 48-volt system. For cost-effective cabling, switching, breaker, and fusing, 150 amps is the upper limit.

In short, the voltage of your solar power system should be determined by your energy use. Continuous currents of more than 100 amps should be avoided.

The larger the components, the higher the current (measured in Amperes or Amps). Large diameter cables and fuses are required for high currents, both of which are costly. When the voltage is doubled, the power (Watt) is doubled at the same current.

Dealing with currents greater than 100A is both inefficient (and perhaps unsafe) and costly. A normal domestic extension cord is rated for a maximum current of 10A. 100A would most likely melt it and cause a fire!

Extra low voltage solar power systems used to be standardized at 12 volts. Most systems today are 24V or 48V with a 230V AC inverter. As a result, the house’s wiring does not need to be different from that of any other grid-connected home, and the cost of cabling is considerably lowered.

We recommend hiring an electrician to install 230V AC wiring in your home. This allows you to use regular air conditioners and lighting, which are generally less expensive to purchase and are getting more efficient.

We used to try to keep the expense of an off-grid installation down by keeping it small. This was accomplished by employing non-inverter 12V or 24V appliances and lighting. Inverters and solar panels have gotten more efficient and inexpensive in recent years. Furthermore, most customers appear to seek more power over time. Upgrading or expanding a 12V DC system with a small inverter is challenging, if not impossible. Not to mention the fact that extra low voltage equipment and lighting are sold by only a few companies.

It’s largely a distribution issue. You may distribute the same amount of power over a shorter distance with a higher voltage by using a smaller cable. It, if you need to operate a large DC motor or want to run something far away from the batteries, 24v will allow you to do so with less cable. This can save money or allow for more services in some setups, but it isn’t always the best option. You’ll also need more high-voltage batteries, so it’s not a panacea for a less priced system.