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Sterling - Pro Combi Q Quasi Sine wave charger / inverter


Pro Combi Q Quasi Sine wave charger / inverter
  • 30 amp through current
  • P.F.C. (power factor correction)
  • Includes remote control with 10m cable.
  • 4 step progressive charging
  • 8 battery type selector
  • Charger only select option (on S models only)
  • Earth - neutral link when on inverter mode to comply with latest regulations
Price:  £573.00
RRP:  £673.80
Save:  £100.80 (15%)
(Inc. VAT @ 20%)
Pro Combi:  

Article Number:  PCQ121600

The Sterling 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 some of the more 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 9.5A, 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.

The pro combi Q is 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 a quasi sinewave.  Hi Fi systems could have a slight buzz on the speakers and onlder, non-flat screen TV's may have a line on the screen however it is impossible for us to accurately state exactly what item may have a problem, if any at all.

Sterling - Pro Combi Q Quasi Sine wave (220v 50Hz Euro Standard)

Power / wattage (at 25°c) DC voltage Part no.
1,600 12v PCQ 121600
24v PCQ 241600
2,500 12v PCQ 122500
24v PCQ 242500

Sterling - Pro Combi Q Quasi Sine wave (110v 60Hz USA Standard)

Power / wattage (at 25°c) DC voltage Part no.
1,600 12v UPCQ 121600
24v UPCQ 241600
2,500 12v UPCQ 122500
24v UPCQ 242500


General specifications

  Euro standard USA standard
Input wave form Pure sine wave Pure sine wave
Nominal voltage Input 230v AC Input 110v AC
Low voltage trip 184v (+/- 4%) 92v (+/- 4%)
Minimum engage 194v (+/- 4%) 97v (+/- 4%)
High voltage trip 270v (+/- 4%) 128v (+/- 4%)
High voltage re engage 253v (+/- 4%) 122v (+/- 4%)
Max input AC voltage 270v RMS 135v RMS
Nominal input frequency 50 or 60Hz (auto-detect) 50 or 60Hz (auto-detect)
Low frequency trip 47Hz (for 50Hz), 58Hz (for 60Hz) 47Hz (for 50Hz), 58Hz (for 60Hz)
High frequency trip 53Hz (for 50Hz), 62Hz (for 60Hz) 53Hz (for 50Hz), 62Hz (for 60Hz)
Output wave form (on by-pass mode) same as input (on by-pass mode) same as input
Overload protection Circuit breaker Circuit breaker
Short circuit protection Circuit breaker Circuit breaker
Transfer switch rating 30 amp 30 amp
Efficiency on line transfer mode 96% + 96% +
Line transfer time 20ms 20ms
By-pass without battery connected Yes Yes
Max by-pass current 30 amps 30 amps
Bypass overload current 35 amps: alarm 35 amps: alarm


Inverter specification / output

  Euro standard USA standard
Output wave form Modified sine wave / quasi sine wave Modified sine wave / quasi sine wave
Output continuous power (watts) 1,600w / 2,500w 1,600w / 2,500w
Output continuous power (VA) 2,400w / 3,600w 2,400w / 3,600w
Power factor 0.9 - 1.0 0.9 - 1.0
Nominal output voltage RMS 230v 110v
Max voltage RMS 260v 130v
Output voltage regulation +/- 10% RMS +/- 10% RMS
Output frequency 50Hz (+/- 0.3Hz) or 60Hz (+/- 0.3Hz) 50Hz (+/- 0.3Hz) or 60Hz (+/- 0.3Hz)
Transient response time <150ms (0% to 100% RCD load) <150ms (0% to 100% RCD load)
Nominal efficiency >85% >85%
Surge ratings 1,500 model = 4,500VA  2,500 model = 7,200VA 1,500 model = 4,500VA  2,500 model = 7,200VA
Online current consumption at 12v / 24v 12v = 1.2A  |  24v = 1A (with new TX tran) 12v = 1.2A  |  24v = 1A (with new TX tran)
Power saver mode current consumption 12v = 0.4A  |  24v = 0.2A 12v = 0.4A  |  24v = 0.2A
Short circuit protection yes (less than 3 cycles) yes (less than 3 cycles)


Inverter specification / input

  Euro standard USA standard
Nominal input voltage 12v or 24v (depending on model) 12v or 24v (depending on model)
Minimum start voltage 10v (for 12v models)  |  20v (for 24v models) 10v (for 12v models)  |  20v (for 24v models)
Low battery alarm 10.5v (for 12v models)  |  21v (for 24v models) 10.5v (for 12v models)  |  21v (for 24v models)
Low battery trip 10v (for 12v models)  |  20v (for 24v models) 10v (for 12v models)  |  20v (for 24v models)
High voltage alarm 15.5v (for 12v models)  |  30v (for 24v models) 15.5v (for 12v models)  |  30v (for 24v models)
Power saver Below 20w (when enabled) Below 20w (when enabled)
Power saver Can be switched on/off with remote control Can be switched on/off with remote control


Charger mode specification

  Euro standard USA standard
Input voltage range 196 - 245v 96 - 130v
Output voltage Dependent on battery type selection Dependent on battery type selection
Output current (12v model) 1,600w = 40A  |  2,500 = 55A 1,600w = 40A  |  2,500 = 55A
Output current (24v model) 1,600w = 20A  |  2,500 = 55A 1,600w = 20A  |  2,500 = 55A
Battery initial voltage for start up 0 - 15v (x2) for 24v 0 - 15v (x2) for 24v
Over-charger protection shut down 15.7 12v (x2) for 24v 15.7 12v (x2) for 24v


Charger Curves (4 Stage constant current) Battery types. 4 step digital controlled progressive charge

Battery type Charge V Float V
Gel USA 14.0 13.7
AGM 1 14.1 13.4
AGM 2 14.6 13.7
Sealed lead acid 14.4 13.6
Gel Euro 14.4 13.8
Open lead acid 14.8 13.3
Calcium 15.1 13.6
De-sulphation 15.5 for 4 hours
Battery bank size Auto detected / auto-program adjusted
Remote control Front control panel removable as remote control
Dimensions 430 x 185 x 180mm
Weight 1,600w = 18kg  |  2,500w = 20kg


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° 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° ambient temperature than in 25°, 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:

Model/product Public perceived power True Cont. Watts @ 40° Victron Phoenix MultiPlus 12/3000/120 3000W 2200Watts Mastervolt Mass Combi 12/2500-100 2500W Not stated Sterling Pro CombiS or Q 12/2500 2500W 2300Watts Victron Quattro 12/5000/200 5000W 12 V / 3000Watts Sterling 3500 combi 3500W 3300Watts.

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°, 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.

What does the Pro Combi range offer?

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. P.F.C., 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.
  4. Power saver mode to automatically reduce power.
  5. Allows through power even with no batteries connected.
  6. 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
  3. 10 metres remote cable
  4. 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's 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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