What is Power Factor Correction (PFC)?

This can be split into 2 groups:

Active PFC – by far the best, this gives a full input voltage range from 80-300V, and (in more technical terms) massively reduces the VA off the product so it will work with about 40% less current and power from generators. This accounts for about a extra 20% cost over the other type.

Passive PFC – this is a simple way of matching the units capacitance with an inductor to balance the load. This allows the unit to pass EU laws regarding harmonic distortion but does not actually fix the harmonics. This results is a much lower cost product with much lower input voltage variations. I.e. 210-230V abilities at much higher VA rating so a generator would need to be about 40% larger to run the product. I.e. a 12V 60A active PFC charger would run on less than a 1000W gen set but a passive charger of the same size would need about 1500W.

This feature is a big deal and should not be ignored especially on boats or vehicles where there are large voltage variations on the input. Even in 110V or 230V only areas, the voltages can easily drop 10%. With Active PFC this is of no concern with Passive PFC the charger will simply stop working.

Power factor Correction (PFC) is the concept that cleans up the electrical waves. By doing so, it increases the efficiency of the charger significantly. Efficiency is measured by the power going out (DC) and the power going in (AC) times 100.
Prior to PFC a chargers efficiency ran at about 65% (35% energy wasted through the charger). With PFC the efficiency
figure is more like 90% (only 10% lost through the charger). PFC, therefore, makes electric bills cheaper and enables one to run the charger from a smaller generator.
Active PFC shall more than likely be advertised as a selling point to the product.
If not advertised assume passive PFC.


The Ingress Protection (IP) rating system is an internationally recognized scale that relates to proven protection against environmental factors such as liquids and solids.

Ingress protection ratings can be identified by the letters IP, followed by two numbers. These numbers define the amount of protection a digital scale has against specified elements and its ability to resist foreign matter that could otherwise get inside the product and cause it to fail.

The first number refers to the amount of protection a scale or indicator enclosure has against solid matter (such as dust particles), while the second number defines the level of protection against liquids. The larger each digit is, the greater the protection.

First number – Protection against solids
0 No protection.
1 Protected against solid objects greater than 50 mm.
2 Protected against solid objects greater than 12 mm diameter.
3 Protected against solid objects greater than 2.5mm diameter.
4 Protected against solid objects greater than 1.0mm diameter.
5 Dust protected.
6 Dust tight. No Ingress of dust.
Second number – Protection against liquids
0 No protection.
1 Protected against vertically dripping water.
2 Protected against dripping water when tilted up to 15°.
3 Protected against spraying water at an angle of up to 60° from vertical.
4 Protected against splashing water when the enclosure is tilted at any angle up to 15°.
5 Protected against water jets from any direction
6 Protected against heavy seas or powerful jets of water.
7 Protected against the effects of short term immersion (under defined conditions of pressure and time).
8 Protected against submersion (under conditions specified by the manufacturer).
9k Protected against close-range high pressure, high temperature spray downs.

Courtesy of www.averyweigh-tronix.com

What is Regenerative Braking?

Please see page 13 for a comprehensive explanation.

Why choose the Alternator to Battery Charger over an Advanced Alternator Regulator?

Ease of installation, is the simple answer. They both end up doing the same thing but by very different technologies. The advanced regulator is a lot cheaper but can be hard to fit. The alternator to battery charger lot more expensive and is a lot easier to fit and has a few extra features like an internal splitting system.

Why Choose a Battery to Battery Charger over an Alternator to Battery Charger and an Advanced Alternator Regulator?

The Battery to Battery Charger is a trouble free installation. Both the Advanced Regulator and the Alternator to Battery charger would cause problems with vehicles with complex ECUs. This is all European vehicles. Most American vehicles may still be okay (this will change over the years). The Battery to Battery Charger connects to the engine starter battery and has 100% nothing to do with the primary system (other than taking its power). All complex aspects off the primary system are left in tact. This ensures no problems will be reflected in the standard engine management system.

Which Battery to Battery Charger to use?

Features 1 New Batt to Batt 2 Waterproof 60A-120A 3 IP68 waterproof 4 Original 5 Original with RBF
Including cables and fuses
Current limiting
High V reduction and low V Boost
Battery type adjustable 6 types
Battery type adjustable 8 types
Battery type adjustable 9 types
Battery type adjustable 4 types
Custom set
Lithium battery type
Fan cooled
RBF friendly
Adjustable current limit new 120-240 model

Why Choose an Alternator to Battery Charger over an Alternator Regulator?

Alternator to regulators have the following disadvantages to the Alternator to battery chargers:
Relatively difficult to install: This limits semi skilled personnel for fitting.
Requires the removal of the existing alternator to work on it: This can be awkward and time consuming.
Requires extra cables to be run on the boat or vehicle: This can be again be time consuming and awkward.
Warranty on new engines: Some engine / vehicle dealers raise warranty issues if a new alternator is modified to fit an advanced regulator.

ECU Problems: Many new engines have ECU’s (electronic control units) on their engine management systems, any attempt to fit an advanced regulator will result in alarms going off (mainly in vehicles, motor homes and the latest marine engines). The Alternator to Battery Charger ensure the main vehicle / boat voltage remains within the ECU’s programmed parameters and allows the extra battery bank to be charged at the higher voltages needed to achieve fast charging.
Total Package: 95% of installations using an advanced alternator regulator also have some sort of split charger system whereas the alternator to battery charger already has that built in.

What is Current Limiting?

Current limiting is the ability of the product to internally limit the current which it will allow to pass through itself. This prevents damage to the unit in the event off heavy current draw (larger than the rating of the product) such as engine starting and large bow thrusters/inverters. This also allows multiple units to be used on the same battery banks with no overloading of one unit. Any size charger / alternator can be used with a current limited device and this device shall limit the current to the rating of the device.

Can I use my solar panels in conjunction with Sterling’s charging products?

Yes, they will work, they have nothing to do with each other but the solar systems will not affect nor interfere with any Sterling Power system.

How to Rate the Size of Charger:

This very much depends on circumstance:

  • From standard shore power, the rule off thumb is to charge at about 10% of the Ah capacity of your battery bank(s). This is ideal if leaving to charge overnight or time is not a big factor. An empty battery (about 80% empty) would fully charge in about 8-10 hours.
  • If charging from a generator, to save on generator hours / fuel, it is recommended to rate the charger to 25%+. The larger the charger the faster the charge rate and the less hours on the generator’s set. This is a purely finincially driven decision based your requirements.
  • A user may wish to really thump current in to their batteries in order to get them charged quickly between short stops. They may be using AGMs and are willing to replace them regularly (as they shall not live long). In this case rate the charger at around 50%+ of Ah capacity. for batteries like lithium it could be as high as 1C which is charging at the total rate of the battery’s Ah in one hour. You could actually use 400A of battery charging on a 400Ah lithium battery bank and charge in 1 hour.

Note. Rate to continuous onboard use. E.g. using 50A, only charging at 20A, equals a 30A deficit. In this case use at least a 50A charger.

Need a larger charger than Sterling can provide?

The Sterling Pro Charge Ultra range is digitally controlled and current limiting. This allows numerous units to be put together in parallel (to increase current rating) or to be put in series (to increase voltage rating). A typical example would be someone wanting 120A charger at 12V. Simply add 2 PCU1260 in parallel. Likewise, you could add 2 PCU2430 together in series to get 30A at 48V.

How to Calculate Fuse Ratings.

In order to work out the size of fuse needed, follow this formula for working out the fuse rating, voltage or wattage for each appliance:
P (power Watts) = V (Voltage) x I (Amps)
The current the product will pull can be calculated by dividing the power used by the appliance by the voltage going into the appliance:
I (Amps) = P (Watts) ÷ V (voltage) for a fuse you like to work from 50-200% above this amp rating depending on the product. For example, if you using a 2500W inverter which is about 200A load, the inverter may have a large short term overload of say 4000W, so the fuse would be able to deal with that surge. The same would be true for a bow thrusters, anchor winches, air conditioners where there is a sizable overload ability – rate to double the continuous load. However, for fixed loads with no overload (e.g. lights) then 30-50% above is fine. Remember, the fuse is to protect the cables not the product, also, note that any wire directly connected to a battery should be fused.

DC voltage measured DC 12V (fuse size) DC 24V (fuse size)
Fridge (40W) 6A 3A
Hairdryer (1400W) 200A 100A
Kettle (1600W) 200A 100A
Laptop PC (350W) 50A 25A
Microwave (1400W back plate) 200A 100A
Television (300W) 50A 25A
Washing Machine (2200W) 300A 150A

How Effective is Advanced Battery Charging?

We are asked all the time ‘do i really need advanced charging on my batteries?’ What effect does a split charger diode have on charging? what % improvement will our products have on a system? Will the extra fast charging boil my battery? Will it excessively gas the battery? what effect, in real terms, can i expect? Most of the questions stem from old wives tales rampant in this market. The idea behind this article is to lay to rest any and all of them and offer the facts . Remember the below results are extreme and meant to show just how hard you can charge an open lead acid battery with no adverse effects. The results were all data logged and were 100% real and reproducible. They are neither guess work nor are made up.

How Effective is Advanced Battery Charging?

Voltage versus current absorbed test

Part 1: The effect of voltage on battery charging

There is no magic with advanced charging systems, in effect, all they do is increase the differential voltage between where the battery is and the charge voltage. In other words the higher voltage that is applied to a battery the faster it will charge. However, on the down side if you do not control that higher voltage after the charge then you will damage the batteries. This simple experiment will show you the direct relationship between actual voltage applied to a battery and the current (A) being absorbed by it. This will give you some idea how your system can be improved and where the problem may lie.

This information is 100% accurate and can be reproduced on any test bench at any time.

The test is very simple and not open to miss interpretation. We will use a simple 100Ah lead acid, so called ‘leisure battery’, a low cost, nothing fancy battery. All we have done is to discharge the battery to about 50%, then connect it to a 180A regulated power supply. We will simply present the battery a starting voltage of 13.2V and see how much current it will absorb from the power supply, then we will simply ramp up the power supply voltage and measure the extra current absorbed as the voltage increases.

For example, the red line shows that when the battery was 50% full at 13.2V the charge current was 35A and at 14.8V the charge current was 160A, an improvement off about 457%. However, the black line on the graph which was taken when the battery was about 70-75% full shows that, at 13.2V, the current was about 1A (showing that, at 13.2V, the battery was full (in its opinion)). Where, as at 14.8V we were still putting in about 60A, a charge improvement of 6000% (rather an improvement).

Why the specific voltages?: The voltages chosen are real voltages which one would expect to see in real life.

13.2 volts: this voltage appears in 2 main circumstances.
a) If you use a split charge diode then one would expect this sort of voltage at the battery.
b) Most alternators now have a built in temperature compensator on their regulator. When the engine room heats up (especially on a vehicle) then the assumption made by the alternator manufacturers is that the battery should be full. So, as the warm air in the engine room is pulled past the regulator, the voltage from the alternator is reduced, the end result is we have seen standard vehicle alternators start off at 14V and drop to 13.2V in vehicles (with the bonnet down) after about 20 minutes. This is okay for the starter battery but will ensure your secondary batteries never charged (as per the graph).

For 24V x all voltages by 2
How Effective is Advanced Battery Charging?

How much extra power is actually absorbed into the battery?

Having established the dramatic charge improvement which a battery can achieve with the increase in voltage, the many sceptics amongst us will now say ‘ the battery will charge faster,’ but you will gas the battery profusely, you will over heat it and boil it, and all the extra current going into it is not being stored, it is simply being gassed off. Therefore the apparent fast charge is a waste of time. All you have done is wreck the battery. These all appear valid points yet are all prolific rumours. Now lets see if they are true or simply the old wives tales.

Part 2: will this fast charge rate cause problems?

With test 2 we take 4 x 100A identical lead acid batteries, as per the above test. We connect all 4 together and discharge them to the same level. Then we will charge one at a time (using a 200A regulated power supply) and over a 1.5 hr period and see how much charge in the form of A are absorbed into the battery and using an Ah counter we can measure the actual Ah which have passed into the battery. After the battery has completed its charge cycle at the allocated voltage we will then see if the A are actually in the battery as storage A. We do this by discharging the battery through an inverter with a 400 watt light bulb load and time how long each battery can run the load after it has completed its charge cycle. If the Ah counter shows more amps going into the battery and the load runs for a longer period of time, then the amps must have been stored in the battery. We will also measure the battery temperature before and after the charge run to see if the battery is in danger (50 deg C is when a battery starts to have problems) of over heating and boiling.

For 24V x all voltages by 2

Answers to the questions based on actual facts:

  • Will the fast charge rate also put more into my batteries? One can clearly see that on the 13.3V charge only 21Ah were put into the battery as opposed to 60Ah with the 14.8V charger. An improvement of about 300%.
  • Did this 300% improvement actually go into the battery or was it simply lost in heat and gas? The inverter discharge test clearly shows that the 13.2V battery ran the inverter for 48 minutes, where as the 14.8V test ran the inverter for 114 mins, a clear 230% improvement. So yes, the extra A were being stored in the battery, and were consumed by the inverter as this was the only place the inverter could get the power from.
  • Will the high charge rate boil my batteries? One can see the rise in the battery temperature at 14.8V was from 18 deg C to 32 deg C, well inside the 50 deg required before there are any problems. Also bare in mind that this test was charging a 100Ah battery at 150A, in real life with 4 x 100Ah batteries you would need a 500A alternator or battery charger to be able to reproduce this test run, so it’s unlikely that one would have a charging source that good.
  • Is it possible to put a lot of power into a battery in 1 hr? The graph clearly shows that the bulk of the power absorbed by the charger was in the first hour. So obviously, the battery was comfortable with this as the temperature rise was well within the battery’s limits.
  • A 100 amp hr battery gives 100A output? Simply not true, even with the best charger, at least 40% or 40Ah tends to be of no use in a battery.
  • Are there any other benefits from this fast charging? Yes you also de-sulphate the batteries, this dramatically increases the life of the batteries and reduces the running hours of your engine and fuel costs associated with the charging of the batteries. In fact there are no down sides to this process.

Conclusion: Its quite clear that all the fears are old wives tales. Now all you have to do to harness this information is to add a computer