PART2: How much power does a camping fridge use at different temperature settings?

In last month’s blog, we looked at how ambient temperatures affect your camping fridge’s power consumption. We did this by comparing the energy efficiency of a common camping fridge, where the internal temperature was set at 4ºC, and the ambient temperature was altered through 21ºC, 32ºC and 43ºC.

By keeping the fridge’s temperature fixed 4ºC, and only altering the ambient temperature, we were able to highlight the impact that external conditions have on a camping fridge’s energy use. In this particular example, the energy used was roughly 3 times higher (within a 24-hour period) when comparing the fridge’s performance at 43ºC as opposed to 21ºC.

The lesson: If possible, try to keep your camping fridge cool, well ventilated, and away from direct sunlight and/or high-ambient conditions. In case you missed it, you can read that blog piece here.

This month, we’re looking at how various temperature settings affect the energy use of the same 60-litre single-compartment fridge. We’ve done this by following the same methodology as last month’s test, however, in this case, we’ve fixed the ambient temperature at 32ºC, and then fluctuated the fridge’s settings through +4ºC, -6ºC and -16ºC.

This allows us to “exclude” the effects of ambient conditions, and focus solely on how various temperature settings affect a common camping fridge’s energy consumption.

The following graphs depict this best…

KEY POINTS

As mentioned in our previous test / blog, the greater the difference between the fridge’s internal- and external temperatures, the faster these two temperatures want to equalize.

That said, your fridge’s insulation is the only barrier that’s slowing down this process. Given that insulation is never 100% effective, eventually, some loses will occur and the fridge’s compressor will have to cycle on in order to replace the lost energy.

In short: Decreasing your fridge’s internal temperature has the same effect as raising the external / ambient temperature. The worst-case scenario would be if the internal temperature was set very low, and the ambient temperature was very high. In this case, it’s not uncommon for the compressor to run 100% of the time.

TEMPERATURE SETTING TIPS

Of course, very few things are better than an ice-cold beer in the bush, however, it pays to be mindful of how “ice-cold” temperatures impact the energy use of your camping fridge.

Generally speaking, most household fridges operate within a 4ºC to 7ºC range. Setting your camping fridge any lower than that may be unnecessary in terms of power consumption.

That said, it can be a good idea to set your fridge’s temperature super low while you’re driving – when the fridge is drawing power from the vehicle’s alternator – and then to adjust the temperature upwards once you get to camp and the fridge is running on battery power.

By doing things this way, you not only ensure that your drinks are cold when you get to camp, you also reduce how much work the compressor has to do thanks to residual cooling.

In much the same way, if you have a dual-compartment fridge, it can be helpful to deep-freeze ice bricks and/or meat in the freezer section while you’re driving, then, once you get to camp, adjust the temperature setting upwards (approximately 7ºC), and move the ice bricks / meat to the fridge section where it can slowly defrost and assist with keeping things cool.

In closing, perhaps the most important lesson of all is knowing that optimum energy efficiency requires a hands-on approach – both in terms of mitigating the effects of high-ambient temperatures, and, to actively adjust your fridge’s settings to best suit the conditions of the day.

The post What temperature should I set my camping fridge? appeared first on 4WD Revolution.

PART 1

Knowing how much power your camping fridge uses is an important step in knowing how much battery energy you need. It also helps when calculating your required solar-panel size.

While several factors affect your fridge’s energy use, ambient temperature is one of the most impactful. Other factors include:

• Your preferred temperature setting
• The thickness of your fridge’s insulation
• The volume of your fridge
• The overall design and engineering of the compressor and piping
• How often you open and close the unit

Of course, it’s impossible to make any specific claims about power use when dealing with so many variables, however, by isolating the effects of ambient temperatures, we get to see how significant a role it plays. The following graphs present an example…

AMBIENT TEMPERATURE

The greater the difference between your fridge’s internal temperature, and the ambient external temperature, the greater (or faster) these two forces want to “equalise”.

This is why the quality and thickness of your fridge’s insulation is so pivotal because the insulation is the only thing that’s slowing down this equalising / warm-up effect.

However, no insulation is perfect, eventually, the fridge’s internal temperature will rise to a point where the compressor will cycle on in order to bring the temperature back down.

That said, the number of ON/OFF cycles is directly related to the ambient temperature. A higher ambient temperature means a higher number of cycles within a 1-hour period.

The graphs below highlight this fact on a single compartment fridge with 60 mm of insulation, and an internal temperature setting of +4ºC.

By excluding all the other variables, and looking at the effects of the ambient temperature alone, we’re able to see how impactful the operating conditions are on a camping fridge’s energy use.

To be clear, it’s not that the compressor is working “harder” or “faster” at 43ºC (as opposed to 21ºC), it’s that the compressor is cycling on 3 times more often. The actual energy consumed – per cycle – is mostly the same at various ambient temperatures, however, the number of cycles considerably changes.

The final graph below combines the concepts of the previous 3 graphs, and stretches that information over 24-hours.

It’s important to note that these values are typical for this size- and type of fridge, however, some variations will exist between manufacturers and the actual usage of the unit. What’s more, these results are based on an empty fridge. If the unit was packed full of groceries, the ON and OFF times would both be longer as the contents of the fridge would “stretch out” the cycle times.

For the reasons explained above, it becomes obvious that the energy use of a camping fridge is irrelevant when stated as a snap shot in time. For example: It’s quite possible that a fridge equipped with thick insulation, drawing 3.5A, can be more economical over 24-hours, than a fridge equipped with thin insulation drawing just 2.5A over the same period.

Again, the efficiency of a camping fridge relates more to the insulation, than it does to the compressor itself. However, the benefit of using a more powerful compressor is that the unit can pull the temperature down a lot faster when you need it to.

KEY POINTS

Ambient temperatures are the enemy! The hotter the operating conditions, the more often the fridge will cycle ON and OFF. Insulation is the best defence against this.

Solution: Keep your fridge away from direct sunlight, and if possible, remove it from a hot vehicle.

Ventilation plays a key role in your fridge’s ability to extract heat. A fridge that can’t “breath” properly, will use more power.

Solution: Make sure your fridge’s ventilation ports are unobstructed, and that hot air can flow freely away from the unit.

Heat will follow the path of least resistance, this includes the door / lid seal that’s designed to be compressed.

Solution: Always keep your fridge’s lid properly latched.

Frequently opening and closing your fridge will increase the number of compressor cycles, as well as how much energy is consumed over 24-hours.

Solution: Try to think ahead in terms of what you need from your fridge, and keep the lid opening to a minimum.

Click here to browse the full range of National Luna fridges

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Answer supplied by National Luna.

Click here to view National Luna’s range of solar-ready products.

To answer this question you first need to know:

• How much energy are you using on a daily basis?
• How much time do you have to replace it?

WHAT SIZE SOLAR PANEL FOR CAMPING?

Naturally, your 12V camping fridge plays a big role in your energy use over a 24-hour period. However, calculating that power consumption can be difficult when there are so many variables at play, including: The ambient operating temperature, the time of the day, how often you open and close your fridge, and of course, your preferred fridge / freezer temperature.

Typically speaking, a premium 12V camping fridge may use between 30Ah and 45Ah over a 24-hour period. Depending on daylight conditions, as well as your geographic location, most campsites have anywhere between 2- and 7-hours of usable solar energy.

Considering that an 85W panel produces roughly 5 amps per hour in ideal conditions, you would need at least 7-hours to replenish 35 amps.

Of course, the above calculation is radically simplified and based on minimum solar requirements as per: fridge size, performance, operating conditions, and how often you’re opening and closing the fridge. What’s more, the calculations don’t account for non-ideal conditions such as:

• Dew / Dust on your solar panel
• Partly cloudy weather
• High ambient temperatures and additional strain on your fridge
• How many appliances you’re powering, and…
• The fact that you need to power your fridge at the same time that you’re recharging your auxiliary battery

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MINIMUM PANEL SIZE

This is why it’s best to upsize the panel to a 120W / 150W unit if you’re thinking in terms of minimum requirements.

What’s more, upsizing your panel size will help to produce enough energy to power additional camping accessories such as LED lighting, and/or a cellphone charger. In some cases, many campers may even opt for a 200W or 250W panel for an additional margin.

However, bear in mind that your regulator would need to be rated to this capacity, and that such a panel may be impractically large in the case of non-flexible units.

ENERGY SAVING TIPS FOR CAMPING

Once you start calculating your energy consumption, it becomes clear that optimising your energy usage is far more practical than buying the biggest panel that will fit in/on your vehicle.

What’s more, some campers make use of a 220V inverter to power their camera and/or laptop chargers, without realising that the inverter itself is drawing significant energy. If possible, it’s generally best to substitute your 220V camera / laptop charger with 12V USB alternative. This alone can eliminate the need for an inverter and cut your energy use in half.

On that note, it would be wise to increase your solar power to a 200W panel if you’re forced to use an inverter, and, to make use of a MPPT solar regulator as opposed to a PWM unit.

Naturally, other energy cutbacks can be made in the form of efficient LED lighting, as well as opting for a fridge / freezer with high-quality insulation, compressor performance, and a correctly sized power cable. Other energy saving tips include…

• Always keep your camping fridge / freezer’s latches closed to ensure optimum seal performance.
• Never pack items around the fridge’s ventilation. Doing so will raise the operating temperature and use more battery power.
• Set your camping fridge / freezer’s temperature to a low setting while driving, then adjust the temperature to a more economical setting once you arrive at camp.
• Avoid parking your vehicle directly in sunlight.
• Keep your camping fridge as full as possible.

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The post HOW MUCH SOLAR POWER DO I NEED FOR CAMPING? appeared first on 4WD Revolution.

Is a 40 amp DC-DC charger better than a 25 amp unit?

Not necessarily. National Luna explains why…

QUESTION

I’ve got my heart set on a DC-DC setup, purely because I like the ease at which solar power can be added to the system. My question is: What size DC-DC charger do I need? Should I be considering a 40 amp unit instead of the typical 20- to 25 amp charger? I know there’s a price difference, but is bigger better?

ANSWER

The limitation of any 20A or 25A DC-DC system is the fact that the battery’s recharge rate is restricted to just 25 amps or less. This is particularly important during the ‘bulk stage’ of the recharge process.

On that note, the following graph depicts the recharge curves of a 25A versus a 40A DC-DC charger. This test was conducted using a 140Ah AGM battery that was discharged by 110Ah (78%).

You’ll see from the graph above that the NLDC-40 restores up to 30Ah more than the NLDC-25 after just 2-hours of driving. Following that, the NLDC-40’s charging curve starts to taper off.

That said, although the 40A DC-DC system appears to be the “silver bullet” of vehicle-based, auxiliary-battery power, the benefit of using a 40A charger is only noticeable during the ‘bulk’ stage of recharging. Once you include the ‘absorption’ stage in the overall process, the total recharge time is similar for both products.

This is because the total charge time is determined by the battery’s technology, and not the charger itself. Simply put: The battery is the limiting factor.

Unfortunately, there’s no way around this, as most lead-acid batteries require considerable time to reach full charge. In contrast, a lithium battery will accept far more energy during its ‘bulk charge stage’ than a lead-acid battery, and ultimately, reach full-charge quicker.

READ NEXT: LITHIUM-ION VS LEAD-ACID BATTERY

However, the economics of using a lithium battery (within a vehicle-based application) should be strongly considered. Thankfully, the NLDC-40 and NLDC-25 both support Lithium-ion and LiFeP04 batteries, as well as regular Flooded, Gel, AGM and Calcium batteries.

So, from that perspective, using a 40A charger is noticeably beneficial if your driving habits are typically around the 3-hour mark or less. Beyond that, the two products start to offer similar results. However, there are other considerations, too…

CONNECTING A SOLAR PANEL TO A DC-DC CHARGER

As mentioned before, solar power plays a big role in the decision to install a DC-DC system, where most top-tier products include a built-in MPPT solar regulator.

Having a solar panel connected to your auxiliary battery negates the need to drive your vehicle on a daily basis. In many cases, solar power will be responsible for keeping the battery full, and may even be enough to supply your total power needs.

This feature is particularly important for motorhomes, caravans and off-road campers, where you’re more likely to camp for a prolonged period, rather than drive your vehicle everyday.

With this in mind, the NLDC-40 features a 600W MPPT solar regulator, as opposed to the NLDC-25’s 375W MPPT. Meaning, your panel array can be much larger when using the NLDC-40; and, because its solar input is rated to 42V, the unit supports newer, more efficient solar panels that generally produce higher voltages.

What’s more, the NLDC-40 boasts a second DC input that can be connected to an external power supply. This is common in mobile homes where Mains Power (220V AC) is converted into DC current, and then subsequently connected to the NLDC-40’s separate auxiliary DC port. This utilizes the NLDC-40’s powerful 5-stage smart-charge algorithm that effectively creates a 220V Maintenance Charger.

TO SUM UP…

Although a 40A DC-DC charger will reduce the bulk-charging time, the real benefits are realized in applications with larger battery banks or installations with large solar arrays.

On that note, here’s a short list of when a 40A DC-DC system should be the preferred choice, and, when it shouldn’t…

A larger 40A DC-DC charger is better when:

• You need the extra charge quickly during the ‘bulk stage’ of the charge, despite the battery not reaching full capacity.
• You have a large battery bank where the ‘absorption stage’ is comparatively short to the ‘bulk stage’ of the recharge process.
• You are powering a load (a fridge or another appliance) at the same time as charging the battery.
• You want the extra solar capabilities

A larger 40A DC-DC charger is NOT better when:

• The battery is not capable of receiving high currents, which is often the case with smaller GEL and Lithium batteries.
• Your application is mostly stationery, where you rely predominantly on AC power.
• Your solar array is relatively small (150W to 350W).

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Whether you’re a weekend camper or long-haul overlander, there’s no denying the convenience of a solar setup. Aside from having free energy to power your camping fridge, a solar panel can also be used to maintain your auxiliary battery for optimum service life.

With this in mind, here’s a basic guide on how to connect a solar panel to your dual-battery system or Portable Power Pack.

WHAT DO YOU NEED?

Simply put: A solar panel, a regulator, some heavy-gauge cabling, and of course, an auxiliary battery.

Although solar panels may vary in cost and quality, what’s just as important, is the regulator that goes with it. In short, the regulator is what converts the panel’s high voltage into a voltage that’s suitable for your battery; which means, the regulator must support your panel’s current and voltage rating.

Typically speaking, regulators are either MPPT or PWM in design. MPPT units are generally more costly, but noticeably more efficient in terms of how much energy they extract. PWM regulators may not be as efficient, but they are basic in function, reliable, and low cost.

It should also be noted that some panels have built in regulators, so be sure to check this before you purchase your panel.

INSTALLED DUAL BATTERY

If your vehicle is equipped with an on-board / installed dual-battery system, you simply connect the panel to the regulator, and the regulator to the terminals of your auxiliary battery.

On that note, it’s best to have your regulator as close to the battery as possible in order to limit voltage loss between the two. For this reason, it may be best to avoid panels with built-in regulators if you want the panel to be mobile and positioned away from your vehicle – resulting in a long cable and noticeable voltage loss.

What’s more, make sure you connect the regulator directly to the auxiliary battery, and not to your vehicle’s main / cranking battery.

PORTABLE POWER PACK

As far as Portable Power Packs and Auxiliary Boxes are concerned, the installation is even easier: simply connect the solar panel to the regulator, and the regulator to the 50A grey coupler on your power pack.

On that note: National Luna recently launched a DC-DC Portable Power Pack, also known as the Green Box. This product is hugely versatile in that it features a 25A DC-DC dual-battery system, a built-in MPPT solar regulator, and a multitude of output power points.

The Green Box makes the installation of a solar panel super straight forward because the MPPT is already built into the unit. All you have to do is plug your solar panel directly into the Green Box’s solar input port, and the built-in DC-DC system takes care of the rest.

The National Luna Green Box is a portable power solution, that doubles as a dual-battery system, as well as a mobile solar setup. Best of all, you can use it in your vehicle, your campsite, or even in your house during load shedding.

WHAT CABLE SHOULD YOU USE?

Cabling is often the most overlooked subject when it comes to dual-battery systems and solar solutions. Ideally, we recommend nothing less than 16mm² cabling between batteries, and 6mm² from your solar panel to regulator.

How bad can voltage loss be? Depending on its diameter, a light-duty cable may double your auxiliary battery’s charging time, and in some cases, prevent the battery from fully recharging and fail as a result.

Brought to you by National Luna

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