RV dehumidifiers need to collect pints of water per day, not ounces. RVs can be very large, up to around 400 square feet in floor area. The Association of Home Appliance Manufacturers recommends a minimum capacity of 10 pints per day for a "moderately damp" area of up to 500 square feet.
This recommendation applies, of course to dehumidifiers for the house. RVs are frequently homes but they are not houses and the temperature inside them changes more quickly in response to variations of the outdoor temperature. In combination with the amount of moisture released inside the relatively restricted space of an RV, this accounts for the extreme condensation problems often reported.
For this reason I would advise against "mini-dehumidifiers" for the RV. There are two types; rechargeable dehumidifiers, which use silica gel to absorb water, and small, electrically powered units, using the "Peltier" process. Neither type can remove more than a couple of pints of moisture per day, typically much less. They are unsuitable for all but the smallest Camper Van and even then more than one may be needed.
Specialized dehumidifiers for RV's and boats are available and have the advantage of being short and squat, meaning a low center of gravity, which makes them more stable while a vehicle is moving. An example is the Mighty Dry DH10. This unit will remove 10 pints per day and is compact and light but retails at around 5 which is a lot of money to pay for a low capacity unit. Even 10 pints per day may be a little less power than you need in a large RV. If the dehumidifier is too small it will run continuously, pushing up your energy costs.
I assume that most folks will be using the dehumidifier while hooked up to an external electricity supply. Units that operate on a 12v supply are unlikely to have the power that you need.
For most RV users a room dehumidifier will be fine. Typically the smallest capacity room dehumidifier is rated for 25 pints which will be enough for even the largest RV. Any reputable brand will be OK but, even in the biggest RV, space may be a little limited.
A "slim" dehumidifier with a shallow depth will be easier to accommodate and will not project so far into the vehicle. One example is the Soleus CFM-25E which has a depth of only 9.25 inches and is rated down to temperatures of 36°F so will be suitable for cold weather.
An alternative is the DeLonghi DD45 model. Although nominally a 45 pint dehumidifier this unit is actually comparable to the Soleus CFM-25E. This apparent anomaly arises from the different testing conditions at which the two units were rated. At the AHAM standard, 80°F and 60% relative humidity, both are 25 pint dehumidifiers.
The DeLonghi is a little deeper than the Soleus, at 11.8inches but can be placed flush against the wall due to the location of the intake and output air vents on the sides. It is less tolerant of cold operating conditions but will function down to 41°F.
Another issue of concern for RV users is the noise level produced by a dehumidifier. On this count the Soleus CFM-25E takes the prize. It has three fan speeds and at the lowest setting it generates only 41dB of noise, very quiet for a dehumidifier.
One way to reduce noise from a dehumidifier is to switch it off. Of course you would not want to do that but both of the dehumidifiers I have mentioned have adjustable humidistat controls and switch off themselves when relative humidity has been reduced to your chosen level.
A dehumidifier with a little more power than you need will run for fewer hours, making less noise and saving you energy.
Happy camping!
