PWM5 Solar Charge Controller



Thank you for buying the PWM5 Solar Charge Controller from – this guide will help you get the most from the product.


The PWM5 is a 6 amp solar charge controller using pulse width modulation for precise voltage control. Designed to be connected between a solar panel (up to 100 watts) and 12 volt lead-acid battery, the PWM5 ensures maximum battery life by preventing overcharging and maintaining maximum possible state of charge. The 3-stage charge sequence ensures that electrolyte is regularly mixed and acid stratification is minimised. Power consumption of the PWM5 is extremely low so more power ends up in the battery. The LED can be disabled if desired for even lower power usage.


  • Pulse width modulation charge control system
  • Solid-state microcontroller and MOSFET circuit
  • 3-stage charge sequence for safe rapid charging
  • LED voltmeter (0.1V accuracy) and PWM indicator
  • For use with 12 volt lead-acid battery systems
  • 6 amps maximum current handling
  • Compatible with solar panels up to 100 watts
  • Multiple controllers can be used in interesting configurations
  • Intelligent co-operation with grid tie inverter
  • Extremely low self consumption (less than 1mA)
  • Protected against short circuit and reverse polarity
  • Very low emission of radio frequency interference
  • 100% waterproof
  • UK designed, manufactured and supported


The red and black wires should be connected to a 12 volt lead-acid battery – red to positive, black to negative. Keep the battery connections as short as possible, ideally attach battery clamps directly to the ends of the red and black wires.  For safety, an 8-amp fuse should be connected into the red wire.

The yellow and black wires should be connected to a 12 volt (nominal) solar panel – yellow to positive, black to negative. The solar panel cables can be extended, but keeping them as short as possible will minimise power loss.

Please note – The PWM5′s  two black wires are connected together internally.


LED Enable/Disable

Upon connection, the charge controller’s blue LED will light for 2 seconds then extinguish. If the charge controller is disconnected during this 2 second period, LED operation will be disabled when next connected. This reduces the controller’s current consumption below the 1mA average (to around 650uA). To re-activate LED operation, disconnect the charge controller from the battery at any time other than during the 2 second period.

Please note – disconnect the battery clamps at dawn, dusk or when skies are overcast. There could be some pretty big sparks if you disconnect during full sun!

Bulk Charge (LED voltmeter)

During bulk charge, the LED indicates battery voltage – slow flashes for volts and faster flashes for tenths of a volt. Volts are displayed with 10 subtracted to make counting easier (you must add ten volts to determine the actual battery voltage). Tenths of a volt are displayed in full (up to 9 rapid flashes). It may not be possible to determine the exact number of rapid flashes.

Saturation/Float Charge (LED PWM indicator)

During saturation and float charge, the LED indicates PWM operation. The brightness of the LED indicates the amount of surplus energy. If the LED is bright, the battery is more fully charged. There is a perceptible flicker of the LED during PWM operation to indicate pulse width modulation.

During the saturation charge phase, the charge controller will hold the battery at 14.4 volts. After a period of time, the PWM5 will switch to the float charge phase and hold the battery at 13.5 volts. Overnight, the controller switches back to saturation charge mode to ensure the battery is charged as fully as possible, early the next day.

Low battery Indication

If the battery voltage is low (below 11 volts), the LED will pulse at a regular rate. This indicates that the battery requires charging. Additional charging (using a battery charger) may be required during winter months.


PWM5 Configurations



Extending the 6A Limit

Multiple charge controllers can be used to connect multiple solar panels to a single battery. Each PWM5 can have a solar panel up to 100W connected to its yellow/black wires. Then all the red/black wires are connected in parallel and hooked up to the same battery.

Charging 2 (or more) Batteries with 1 Solar Panel

Multiple charge controllers can be used to charge more than one battery from just one solar panel. This time a single solar panel up to 100W is connected to the yellow/black wires of multiple PWM5s (in parallel). The controllers’ red/black wires go to the batteries (one controller per battery).

Compatibility with Grid Tie Inverters

If you have a grid tie inverter (the type that operates between 14 and 28 volts), you can connect both your solar panel (up to 100W) and the grid tie inverter to the yellow/black wires of the PWM5. The red/black wires connect to your battery. In this configuration, your battery will be charged first, then surplus power from the solar panel will be drawn by the inverter and fed into your mains. The best of both worlds – a fully charged battery and solar power offsetting your electricity usage and lowering your bill!

Please note – you can connect the yellow side of multiple PWM5s together or the red side, but not both. Controllers cannot be paralleled up. Solar panels larger than 100 watts cannot be used with this controller.


The controller is protected against short circuit and reverse polarity at both the battery and solar panel connections.

The PWM5 is also protected against interference from radio transmissions and electrical activity. A watchdog circuit ensures its continued reliable operation. Radio frequency emissions are extremely low.

A diode is fitted into the yellow wire. This protects the charge controller against short circuit and should not be removed during the warranty period. If product warranty is not required, the diode can be removed for a small performance improvement. If the diode is removed, ensure that your solar panel is fitted with a blocking diode and that the solar panel connections are not shorted when the controller is hooked up to a battery.

Please note – never short circuit the terminals of a lead-acid battery.


The PWM5 comes with a 1 year warranty. The warranty will be void if the diode is removed from the yellow wire, or more than 6 amps are passed through the controller. Solar panels larger than 100 watts cannot be used with this controller.


Problem: The LED has stopped working and disconnecting the battery hasn’t fixed it.

Solution: This can happen when there’s power coming from the solar panel. Cover the solar panel and try disconnecting the battery again. Or wait until dark and disconnect the battery. The LED function will be restored.

Problem: My panel is connected but there’s no output.

Solution: Connect the red/black wires to a 12 volt lead-acid battery.

Detailed Explanation:  The charge controller does not work like a voltage regulator. If you connect a solar panel to the yellow/black leads, you will measure nothing on the red/black leads unless they are connected to a battery. In fact the only meaningful voltage measurements you can make are at the battery terminals.


  • Maximum current handling: 6 amps
  • Maximum solar panel power: 100 watts
  • Current consumption (LED indicating voltage): 1mA average
  • Current consumption (LED off): 650uA typical
  • Dimensions: 68mm x 35mm x 17mm (approx)
  • Cable lengths: 220mm (approx)

29 Comments on User Guide

  1. Paul says:

    It’s not clear to me what a slow flash is and what a fast flash is. A video of the device in operation would help.


    • Julian says:

      I’ll have to describe it in words because most cameras are just too slow to pick the flashes up! The duration of the flash is very short; that’s a power saving measure. By slow flashes I mean flashes that are about a half a second apart, the fast flashes are about a quarter second apart. So if there are 3 slow flashes (not so closely spaced) and 5 fast flashes (closely spaced), that’s 13.5 volts. Actually it’s easier than it sounds.

  2. john says:

    i have purchased 7w solar trickle charger to charge a12v 110 amp liesure battery do i need a regulater ? also do you think a 7w charger is to small?

    • Julian says:

      You can probably get away without using a regulator until about April next year. In the middle of summer, a 7 watt panel would eventually harm your 110Ah leisure battery (and leisure batteries aren’t cheap). My first system had a 12 watt panel connected to a big old car battery, and in midsummer I noticed the battery voltage had risen to 16.5 volts – enough to cause damage. That led me to buy my first charge controller and then to design the PWM5.

      Do I think a 7-watt panel is too small? It depends on the season! In the middle of winter it won’t do very much – I would recommend a 20-watt panel to keep a battery topped up (even if it’s not being used). In summer, your 7-watt panel will be more than adequate and will need a regulator if you don’t want to overcharge the battery.

  3. julian says:

    Hi I’m Julian and I’m wondering if I get a reply by email aswell as my message posted

  4. Eric says:

    I have a caravan with a 110Ah leisure batt and 2x20w solar panels all wired up with a rubbish charge controller, rubbish because it leaks over 100mA back so discharges much of it’s input, especially overnight. Can I use your unit with my 2x 20w panels in parallel ?

    If so I’ll be buying one due to the extreemly low internal consumption

    Thx Eric

  5. Tony says:

    Hello Julian
    I use a PWM5 with a solar panel to keep my gel batteries up on my small boat, first class device.
    My outboard can be configured to give about 22v and 3amps.
    Would the PWM5 be able to cope with the outboard ok??? I will only use one or the other.

    • Julian says:

      It depends how the output from the outboard is regulated. If it’s current regulated and the voltage can be pulled down to that of the battery (12v to 14v) then it might work. But the PWM5 wasn’t designed for use with anything other than solar panels, so I can’t offer warranty if it doesn’t work (or worse).

  6. billy long says:

    Hi, I,ve read on the internet about a fella who has a solar panel rigged up on top of his parcel shelf to the battery of his ‘s type’ Jag because they are known for flatting their battery when not used often. any idea what size panel he would have used and would he have used a pwm5? thanks Billy [uk]

  7. chaplin says:

    I want to use it between 8 Watt solar panel (~18V 0.5 A) and car battery connected during cigarette plug. Manufacturer recommend just unplug it when it fully charged :)
    Can I not disconnect it with this device? Can it be connected when I drive my car ?

    • Julian says:

      Yes, you could connect it with the PWM5 and you could leave it connected when you drive because the PWM5 is tolerant of other charging sources including alternators. An 8 Watt panel is not very powerful though and when I tried using a small solar panel inside my car, the windscreen blocked out so much of the sun’s energy, there wasn’t much left.

  8. chaplin says:

    What a size of PWM5 ?

  9. Sam says:

    Hiya, I am looking to but one of these charge controllers but my question is this. If I have two 12v batteries connected in parallel to output 12v with double the AH’s could you attach this charge controller to one of the batteries and it would charge both batteries as they are still connected in parallel? If so then when running my 24v DC to 240v AC inverter of the parallel batteries would I have to disconnect the charge controller or could it stay attached and charging them?

    Thanks and sorry if this are simple or dumb questions!

    • Julian says:

      If the connecting wires between the two batteries are reasonably thick, you can treat it as a single battery. The charge controller can be connected to either battery and both will charge together.

      Yes, you can leave the controller connected while you’re using the inverter.

      Not dumb questions!

  10. Dave says:

    Will you be makeing as Solar Controller that can cope with 12v 6.5 Amp (100Watt)

    • Julian says:

      The 6A maximum current is a soft limit – it can be exceeded. Some higher grade 100W solar panels do output a little more than 6A and my guarantee is that all 100W panels are compatible. The controller has been field tested with a number of different 100W panels in a variety of locations worldwide and all feedback has been positive so far.

  11. chaplin says:

    My cigarette plug include diode for protection. Are is need remove it or leave as is ?

    • Julian says:

      I’d leave the cigarette plug alone – for 2 reasons. Car windscreens block out a lot of the sun’s energy, so putting a solar panel inside the car and connecting it via the cigarette lighter socket isn’t the best idea. I’d attach the charge controller directly to the battery terminals, make up a plug and socket arrangement and keep the solar panel outside the car. It’ll charge a lot faster that way.

  12. John Holland says:

    PWM5 was working perfectly until I disconnected battery bank (boat).
    Cannot get LED working again even though controller part seems fine. Have reconnected and waited 2+ seconds before disconnecting battery again and reconnecting. No LED. Please help.
    Many thanks

    • Julian says:

      This happens because power from the solar panel keeps the controller alive even though the battery has been disconnected. Try again after dark or cover the solar panel and try again.

  13. Peter Clarke says:

    Hi Julian, I am hoping that on discovering your product that you may have saved me a ton of trouble and headaches in my project. I am an astrophotographer purely as a hobby and need to be in outdoor locations away from light and then of course electricity. I wish to use a solar panel to keep a 125AH marine deep cycle battery charged for when the sky clears. So after reading your webpages am I correct that with a 20w or 40w solar panel charging the 125ah battery that all I would need to add is your PWM5 float charger? Hope you can let me know of any problems with this setup.

    • Julian says:

      Hi Peter. This is exactly what the PWM5 was designed to do – provide 12 volt power in off-grid situations. My only advice would be – go for the 40W panel rather than the 20W – that big 125Ah battery will need a good size panel to match.

  14. Dennis Johansson says:

    Hi Julian,
    I have a solar panel of 18V and 80W. Is it possible to use your PWM5 with this panel and a 12V battery?


  15. David Knight says:

    My indication light has stopped flashing at all.
    I don`t know how long it`s been like it.
    Should I be concerned.
    Kind regards,

  16. ravi says:

    Dear Julian ,
    when you say 6amp and 100watts panel can be used to charge , does this means that we have to select the panel depending upon battery amph …i mean c/10 or any rating of battery will do

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