I’m running a 160amp alternator charging 8 house batteries on my commercial trip boat. These run inverters to power electrical appliances in the bar and a vacuum cleaner, etc. The ZM4 allows me to give the peak amount of power to the batteries without overloading the inverters. The ZM4 was a simple solution because it works so well, saving me time, money and stress. Great customer support, quick delivery and always available for questions.

 Peter K

 Having an electronic background and fitting out my own launch I knew I needed a smart charger to get the best from my batteries, after searching the net and being put off by very high prices I found the ZM4.It was the single most pleasurable process during the fit out, The ZM4 works superbly and easy to install, my house batteries were old and running at only 60% and 5 years old, I still get good usage saving the cost of replacements for a bit longer. The ZM4 is designed on very sound battery charging principals and delivers even at very low RPM. Graeme was fantastic, very helpful and even popped in for a personal visit when he was in my town, he went out of his way to offer advice and share his experience, and he supplied me with an alternator with the correct pulley size in addition to tips on making up a better pulley tension system.I highly recommend the ZM4 for any boat or camper van.Delivery was excellent and service superb.Thanks for a great product

Marcus K

I wish to say that the ZM4 was all you said and more. It was easily installed (with help from a couple of phone calls) and works a treat. Even after a couple of months when I wanted to add a tacho to the system Graeme did not hesitate to help in  simple layman terms so that I actually understood what I was doing. Sent me the part I needed without hesitation. I feel that I got good value at the price I paid and exceptional service.

 John D

I have fitted the ZM4 smart controller and am looking forward to reducing our engine hours to charge our batteries. The support and advice I received was outstanding, including a professional conversion of the alternator. The ZM4 is very affordable and the build standard is high. The instruction manual was informative and very easy to follow.

Neil A

I have found the ZM4 to be a great product; adjustment is simple when checking the charge rate using a digital meter. I believe mine was one of the earlier model and still under some development, Graeme recalled it and brought it up to date at no cost to myself. It has performed perfectly and I believe it represents great value for money.

Alan S

ZM4 works great, it’s so nice to always have full batteries. Your service is A1 and value for money. - Brian J

A fantastic product that does what it is supposed to do - straight out of the box.Easy to install and set up with very clear instructions.Excellent value for money.Product support is second to none. This company truly wants to help you get the best out of their product.I like knowing that my batteries are being looked after and charged in a way that not only charged, but charged quickly and in a way that prolongs their life.  - John P

The ZM4 provides an effective alternative to the big brand smart regulators and at a very affordable price. Easy to install and after 2 years, has proven totally reliable. The support provided has been outstanding.Highly recommended. Steve M

My yacht was fitted with a stock standard Bosch 85 amp alternator and although it coped well with normal loads such as engine starts and light standing loads it struggled to high demand loads.I could never get maximum amperage from my alternator and charging the batteries took a long time whilst motoring. Replacing the alternator was not going to fix this and the only alternative was a smart regulator. The ZM4 fit the bill perfectly. It’s a very cost effective unit and gives the user the option to make minor voltage adjustments to suit their needs. Replacing the standard regulator with a ZM4 was easy and the instructions were very descriptive and well-illustrated. System performance improvement was immediacy noticeable.  Later on I made a request to change the system reaction time to suit my specific needs. This was done and returned within a week.The system has been running faultless for 2 years, basically install it and forget it. 

Andre W

The ZM4, coupled with the 90 amp alternator purchased together as a package from Graeme Polley, now provides ample 12 volt power for my launch. Previous to this, I struggled continuously with undercharged batteries and poor anchor winch performance,The ZM4 was very simple to install, just follow the provided instructions,. And it has performed flawlessly now, for nine months and a hundred engine hours.. All the other 12 volt regulators that I found when researching this upgrade for the launch, appeared to do much the same job but were selling for many times the price of the ZM4. And the price of other alternators offered, again all seemed hugely more expensive than Graeme Polley’s product. This combination certainly was ‘Value for Money’. I could not believe the patience and depth of knowledge displayed by Graeme Polley. Graeme far exceeded my expectations when it came to answering all my questions, promptly returning my emails, and providing ‘expert’ knowledge as to how I might upgrade my launch.  Customer Service rating....

Exceptional!! – Graeme A

About 18 months ago I purchased a ZM4 smart regulator. All I can say now is that I am delighted I did and am definitely satisfied I got value for money. The ZM4 smart regulator does what it was advertised to do, “ensure batteries are being charged when the engine is running”. So no more wasting fuel running the engine trying to perk up the batteries with out result.An other important aspect of this purchase I found was that the supplier, Graeme Polley, was as good as his word with regard to follow-up support. I am no expert when it comes to these matters and found Graeme ready and willing  to help with advice when needed to ensure customer satisfaction.-A thankful sailor

Rudi B.

Thanks Graeme, that ZM4 you designed works a treat, we will definitely be fitting more of them, they are perfect for charging leisure batteries to the right voltage, because the voltage is adjustable, the price and service was pretty good too, the only criticism in my view is that the voltage control needs to have finer adjustment, with my fat fingers it can be a little tricky 

Harry,Vantage RV Ltd

I’ve been mulling over our charging dilemma for a few years. We have a 28 foot yacht, 14hp Diesel engine. We installed a 12v fridge about 5 years ago (sucks about 1 - 1.5 amps/hour), I had a hunt around & found the ZM4 to be very well priced.After Graeme tested, overhauled & modified my existing alternator I couldn’t believe it was the same unit. It arrived back looking brand new again. The ZM4 was quite simple to install. When I did need Graeme’s input he was always happy to help out.So with the ZM4 we’re putting back in around 1 amp every 2 minutes, 30 amps per hour.In summary, the ZM4 is a fantastic product that has completely solved our charging issues. Installation is not at all difficult and the small outlay involved won’t stretch the bank. Graeme is very down to earth, & he doesn’t “talk down” to you –

John H

The ZM4 is a great product , we fitted it to a 120 amp  alternator in our campervan which is fully mains & inverter electrified,  with gas  only for emergency.Great value and thanks for the terrific service.

Dereck & Mary S

I have had a ZM4 fitted to my yacht since 2007,serial number 021, and never had a problem,

Great unit - Leith M

I am very pleased with the ZM4 regulator I have now run it on two separate occasions and it is performing brilliantly and it complements the solar and wind generator nicely. The ability to regulate the voltage on bulk charge is a very nice option so one can optimise the charging. Thank you for all your help as it has been very worthwhile.

Simon – Trinidad

11.2m Powercat. Twin engines, triple battery banks, triple alternators. Complex, inefficient and unreliable.Embracing Graeme’s experience, service, passion and commitment to quality we refurbished and reconfigured the charging system to twin alternators, twin ZM4’s and twin VSR’s to simultaneously charge the start battery banks in parallel with the large house bank. End result? Simplicity, capacity and reliability. 

Graeme’s personalised service goes well beyond just the supply of a smart, cost effective regulator and alternator refurbishment service.  I recommend you talk to him first about achieving the maximum efficiency of your charging system from alternator output (idle RPM, pulley size, rating) to battery bank capacity (amp hours, charge voltage, charge time). I thoroughly recommend his service.

Leigh J (Auckland) – Dec 2014   

The ZM4 is an excellent piece of kit, it has massively cut down my charging time and unlike the smart charger on my last yacht, this one does not cook your batteries! Further Graeme is a great guy to deal with, he also matched a hastily purchased alternator to the ZM4 and then made some significant improvements to the alternator.  Very few marine electricians would have his understanding of charging systems

Gordon Dyer Waiheke Is - March 2015

The best thing I have ever fitted to my keeler and at a very affordable price. Along with Graeme's invaluable advice it resolved many electrical gremlins and has given me the confidence in the electrical system to venture away for weeks at a time. I would also recommend fitting a monitoring device showing battery SOC (% state of charge) and charging amps - you'll be surprised at how little engine running time is required to fully charge the batteries and how well the ZM4 works. Greg - "Loose Cannon"  


I am very very impressed with the finish  of the alternators and to the standard of workmanship shown. Many thanks Ross N 2015


Once again thanks for all your help, it’s the best customer service I have ever come across.Allan W - Australia - Feb 2016


Graeme,Another very happy customer here.  The replacement alternator dropped into place as hoped for, the ZM4 control unit is functioning well and after two weekends of use all is great.  Thank you for your guidance and suggestions for the install.  -Rob P March 2016


The ZM4 performs as Graeme said it would. It was installed during July 2015 and has performed flawlessly.

Graeme’s dedication to customer service and producing a good product is second to none.

Roy M. October 2016 - Fitted to a motorhome


I recently purchased a launch which appeared to have electrical gremlins causing an electrical spike at a certain rev / temperature range. Graeme tested the ZM4 for me and also ran my alternator through his test rig to see if they were the cause of the problem. Both were functioning as intended, so on a second visit to my boat Graeme isolated possible fault causes and eliminated them as variables until he found the problem – an inadequate circuit breaker. We replaced this with a more suitable alternative and tidied up some of the wiring in the engine room, ran, tested and calibrated the ZM4 on a sea trial. I was extremely happy with Graeme’s service, knowledge and fault diagnosis capabilities and would not hesitate to use him again or refer him to others. Scott Henderson, Tauranga November 2016


I have recently fitted a ZM4 alternator voltage regulator on ‘Meola’ a 13m trawler style boat. Power by a 4L3B Gardner.

It has helped to stop the under/overcharging and gassing off on the two banks of 24volt batteries.

Being able to set the desired voltage to the batteries is brilliant and having a floating capability as well makes a huge difference to the max storage.

I am very satisfied with this product and recommend it to others.

Regards Iain - Auckland - December 2017 .


Hi Graeme!

 I just thought that I’d take a quick minute to tap this email to you, to say a HUGE thanks! I purchased a ZM4 at the end of last year having found that a competitor brand circuitry had all burned out and left me in a situation where I needed another external regulator and fast (I was all packed up ready to head out for summer break to find that my alternator wasn’t charging my batteries).I got recommended your unit by a friend and installed it, it was very easy to install onto my 671 Detroit Diesel motor. The only thing I didn’t realise is that the old external regulator was switched to positive and this needs the negativeToo all the people that are thinking about buying this unit, just do it!. Graeme’s help over the phone to diagnose that, that was my issue while he was at a campsite was amazing! “do this then check then ring me and tell me” I had called about 20 marine sparkies and all of them had left for their own break and I was staring down the barrel of not being able to use the boat at all.But my persistence and Graeme’s help got me there. After disconnecting everything from the cover (of the alternator) and changing a few wires around we got it going. And we left for Waiheke (from Milford) that day. It charged at 15 volts the whole way. From here we left and went up to Great Barrier Island where we spent 5 days until the storm threatened so we came home.If it wasn’t for the ZM4 and Graeme being so knowledgeable about his product and alternators. We would have not had the awesome break that we did.

I would have no problem on recommending this product to anyone. Thanks a bunch Mate! 

Drew Miller. January 2018


Just to let you know that the reg I fitted is working perfectly.Just came across the South China Sea with no wind and motoring all the way for 4 days. The old system would have cooked my new AGM batteries so I am thankful for your smart alternator reg.Continuing to motor up the east coast of Malaysia and on to Thailand this SW monsoon season. Best regards and thanks for a great product and all your help setting it up.

Geoff ~ S/V Arnak ~ May 2018


I have just completed installing the Smart Regulator system that Graeme  Polley designed and supplied for my offshore yacht.I am not tech savvy regarding charging systems so Graeme designed a setup with backup to cover all eventualities. This involves  two ZM5’s that are switched if one should fail.Controlled trickle charge in case my Lithium Ion house batteries over-discharge.An over- voltage  warning alarm on start battery in case of Splitting  Diode failure.Graeme also provided a spare modified alternator brush block, a spare alternator and spare standard brush block.I am now confident to sail off in to the blue with the knowledge and backup capability to handle all the problems that could possibly occur.There were quite a few teething problems with setup, wiring and adjustment but Graeme managed to get me through all that with skill and enormous patience for my lack of tech ability.I would recommend that the average boatie should not only buy the Smart Regulator from Graeme, but also get him to advise and design an appropriate set up.His charges were very reasonable and the advice and education on  batteries and charging matters invaluable.

Merv Wilson, Yacht “Mulberry” - July 2020


I have fitted four of these smart regulators to 2 fishing boats and a pleasure boat and have a very good run with them. They are giving us longer spells between charges and longer battery life, and the service and knowledge I received from Graeme Polley has been exceptional and much appreciated. Very happy customer.

Douglas Dobbs. - November 2020


Well that last ZM4 Smart Regulator of yours kept our batteries beautifully charged for almost four years and a thousand engine hours, from New Zealand through French Polynesia, Hawaii and Alaska, and now down to British Columbia. It would still be working great I'm sure if I hadn't made that silly mistake with a crossed wire last fall. Thanks to your very quick response, we were back up and running with the new ZM4 in no time. You've got a reliable product Graeme, and your customer support is top of the stack. You can use me for a reference any time.

Al T - SV Ten Gauge - April 2022