Sterling Power's original Pro Combi S Pure Sine Wave Inverter / Charger 24V 3500W. Might show signs of installation/wear.

30 days warranty


Dimensions 3500W


DC (V) Power (W) Charger (A) Code
24V 3500W 100A PCS243500


Pro Combi range is designed to be very competitive, no frills, high performance, and value for money products, presented in a simple, easy to install and use style.
If you require power assist, parallel connection, three phase output functions or any other enhanced combi features then this range is not for you. If you’re not familiar with these things this ProCombi is perfect for you.
Modern combis are getting more and more complex, with each company trying to out do the next with abilities beyond the understanding and requirements of most people. This detracts from the combi’s main strength of being easy to install and easy to use. There is, no doubt, a market for the advanced functions but the vast majority of combi users simply do not need them and never will. Most people simply require the unit to act as a high performance constant current battery charger when on mains power then cross over to act as an efficient inverter when on battery - and that’s it!
The problem with enhanced functions is, even if they are not used, they eat up valuable power. The more functions on a product running (even though you do not use them) the higher the quiescent current on the inverter (the current the unit uses itself to operate). Complex combis at 12V can use as much as 9.5 A, whereas, Pro Combi can use as little as 2A.
Also, a lot of the expensive combis do not even have a power save function which can drop the combi power consumption to as little as 0.2A when off load, some combis continue to consume 2A + even when there is no load.
Sterling has reversed this trend with this Pro Combi range by stripping away the unnecessary features from a complex combi saving money. The end result is a simple, straight forward product that does what you think it should. Using our years of experience in this market we have tailored the product range to suit 90% of people purchasing Combis. 

Standard Features
30 amp through current
P.F.C. (power factor correction)
4 step progressive charging
8 battery type selector
Earth - neutral link when on inverter mode to comply with latest regulations

Pro Combi S Euro pure sine wave 220V 50Hz Euro Standard

DC Voltage Power at 25 deg C (Watts) Part Number
24 3500 PCS243500


Pro Combi S pure sine wave 110V 60Hz USA Standard

General Specifications

 Weight 3500W
 Dimensions  2500W LxHxD 380mm x 220mm x 190mm | 3500W LxHxD 550mm x 220mm x 190mm


Inverter specification output


Inverter specification input


Charger Mode Specification


How to compare model ratings with other Combis:
                  Watts  vs  VA :  the  truth
The most significant issue to be aware of is how output ratings are massaged to appear better than the competition.  You might be excused for thinking that a unit with ‘3000’ written on it, for example, means that it will deliver 3000W continuously.  This is not necessarily the case if you look at the small print.

Have you ever found it strange that the product you want to run (i.e. the hair dryer, washing machine, TV, etc), has the power consumption shown in watts, yet the inverter/ generator companies give you the rating in VA, and when you put your 1000W product on a 1000 VA inverter it does not work. In the small print you find out that the 1000 VA inverter is only 700 watts for 10 mins then it over heats- this simply cannot be right.

In the eyes of the unknowing consumer, rating a power product in VA is a simple way of using meaningless figures to confuse and make performance appear better than it really is. Unfortunately this practice is still allowed in Europe (European standards committees are looking into this practice) unlike the USA where there are recognised standards (eg ABYC) and you can be sued for publishing misleading information and incorrect ratings. The only true rating, without confusion, is in watts, using a simple resistive load with unity power factor, such as an electric heater / standard light bulb, etc. This method gives a lower correct figure, however, it is not what the marketing teams involved in promoting power products want to see.

Take, for example, a 3000 Victron Multi that is perceived by the public to be 3000W continuously rated. If, however, you read the Victron specification for watts at 40 degC the actual power is 2200W.The Sterling 2500W Combi delivers 2300W which in fact makes it a more powerful unit. This distortion is not limited to Victron, unfortunately most, if not all, the European manufacturers push model figures to the realms of fantasy in spiralling competitiveness and in order to confuse and impress the public who believe that these figures are actual continuous power rating. 

Furthermore, the effects of temperature and the duration of duty (i.e. how long a load is maintained) can also be used to manipulate ratings. It is much harder for a unit working in 40 degC ambient temperature than in 25 degC, just as it is harder to run at a higher load for extended periods. Therefore, a unit rated for short periods at a cooler temperature will also appear more powerful.
To illustrate, taking data published by Victron Energy and Mastervolt, the following comparison can be made                                                       

The simple truth of the matter is VA means nothing. If you want to know how much power your inverter is going to give you then ask for the rating in watts at 40 deg C , all the other ratings should be kept for the comic books where they belong. ProCombi has the lower value in the model name but, in fact, is the more powerful of the bunch when like for like ratings are compared making it even better value for money than you thought. With the Sterling unit you get what you think you should be getting, and it does what it says it does on the box.
The sooner ratings have a legal recognised standard like the U.S.A. the better for everyone.

On the battery charger side
1) 4 step constant current battery charging
2) 8 preset battery type selector plus de-sulphation
3) Powerful charge rate
4) Will charge even with totally flat batteries
5) PFC, draws about 30% less power than conventional units

On the crossover side
1) 20  m/s crossover time, will not to lose any equipment due to power loss
2) 30A through current ability on all models
3) Twin 30A / single 50A on the 3500W models

On the inverter side
1) High overload ability
2) High temperature rating
3) Low quiescent current
5) Power saver mode to automatically reduce power
6) Allows through power even with no batteries connected
7) Neutral earth link to enable RCD breakers to work

On the remote control
1) Ability to switch the unit on/off
2) Ability to select or de select power saver mode

1) Removable local panel to give remote control with warning and function LED
2) Remote on/off plus remote power saver on/off
4)10 metres remote cable
5) Almost 20 alarms / warnings / information
 There are 2 main models the Pro Combi Q ( for quasi-sine wave ) and the Pro Combi S ( for pure-sine wave )  

So the simple question is, what best suits your needs?
Pro Combi Q, (quasi-sine model) suitable for most installations, where you would use a microwave, fridge, hair dryer, vacuum cleaner, kettle, computer, etc The vast majority of products will run on quasi-sinewave. Hi Fi could have a buzz on the speakers and older non flat screen TVs may have a line on the screen. It is not possible for us to say what item may have a problem, if any.
Pro Combi S (pure sine wave model) where all the above plus washing machines, bread makers, thyristor controlled equipment are used -  then sine wave is required.
To make the choice even simpler we have 6 months exchange / upgrade policy. If you purchase a Pro Combi Q and find there is some equipment that you cannot run due to the Quasi Sine wave and require Pure Sine wave, Sterling are happy to up-grade your quasi-sine unit for Sine wave with the only cost being the difference between the 2 products  (unit must be sent direct to Sterling and in good condition). Offer applies dealing direct to the factory only.

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