Things have moved on from from the old Adverc & Sterling type alternator controllers. The Mastervolt Alpha Pro’s ability to set alternator target voltage is just a small part of it’s function and it brings alternator control to a new level. There are other similar controllers like Balmar’s MC-614 & the Wakespeed WS500 and Mastervolt’s version has a great balance between value & function. The Alpha Pro has never been offered as an option by any UK narrowboat builder or engine mariniser and isn’t marketed well by Mastervolt for the UK inland waterways so people just don’t realise what they can do. Update… as of late 2021 it’s just been added as a Lithium option on Beta 43/50 engines.

‘Small Engine Mode’. Sets a 20% alternator output (ie. alternator load) somewhere below tickover, and then specifies a higher engine speed for full output. There’s a smooth linear progression between these 2 points. This enables you to set a precise lower load at idle reducing further at the lower in-gear tickover speed.

For the high output alternator setups I supply & fit it works so well – fitting a large (12V 100+ amp) alternator to a typical narrowboat engine (Isuzu, Barrus, Beta Marine) creates high loads at in-gear tickover speeds – this causes poor engine running and belt problems. On Beta 43 & 50 engines it increases the likelihood of the serious crank pulley issues.

This tool makes it possible to fit a much bigger alternator to an engine or belt drive system than you would normally be able to use. The system is dialled down to work closer to the edge of belt or engine limitations and the larger alternator enables unstrained reliability and continuous high output.

Alternator temperature sensing. The optional sensor enables an alternator temperature to be set where output begins to back off and then a high temperature at where the alternator stops charging. It’s similar to how the ‘small engine’ feature works and allows you to get the very most out of the alternator but keep things safe and comfortable. Where there’s a large lead-acid bank or lithium batteries alternator temperature sensing is so useful.

Max Percentage Alternator Output. Good quality Lead Acid & Lithium batteries have a recommended max charge current (C-rate). This function can de-rate max alternator output to suit, or set a max alternator load based on belt limitations.

Programming is done with the Mastervolt interface and I take great care setting the system up properly. The end result is a powerful, efficient, unstrained and reliable system.

For charging Lithium batteries IMO a Mastervolt controller is absolutely the right way to go with many advantages over Victron or Sterling current limiting equipment. Current limiting is clumsy and a reasonable limit will creat too high a load on most engines at in-gear tickover yet doesn’t take advantage of a large alternator at higher engine speeds. Fitting the Alpha Pro safely gets the very best out of the alternator & engine, and many Lithium Battery Management Systems such as the Victron BMS, 123\SmartBMS or even a Victron BMV monitor can be adapted to control and shut down alternator charging.

You don’t need the expensive Mastervolt alternator and their smaller alternators don’t work well with a poly-v belt setup due to inability to run freewheeling clutch pulleys. Some domestic alternators used by the big UK engine marinisers can be adapted and work well with the controller. I have custom, well thought out alternator upgrade kits available to retrofit to some of the most popular engines, and an option to replace a 3.5 Dometic Travel Power with a 200 amp alternator – This becomes particularly useful with lithiums as the high loads caused by a Travel Power + large domestic alternator can cause issues meaning one becomes redundant. The 200 amp Bosch alternator used in many of my setups is the same series converted by Mastervolt in their top of the range ~£2500 14/200 system.

Happy to chat – Any queries/questions call Ed 07922 163072


Example of a standard alternator being modified for charging lithium.

During build of https://falcon-tenders.com new 2021 mega yacht limousine tender they looked at ways to charge a 2* 12V 5500AH Mastervolt lithium bank from the twin Hyundai engines. It was impossible to physically mount a Mastervolt alternator to the standard engines. I modify the factory fitted 150 amp Denso alternators to work with the Alpha Pro’s and full Mastervolt setup.

Practically any alternator can be adapted and the factory alternator is often a far better solution than a full Mastervolt or Balmar system.


Example of a large alternator installation only possible with a Alpha Pro..

Basic spec of this new narrowboat: 510AH Victron AGM battery bank. Victron 3000 Multiplus. Victron BMV712 monitor. High power demands: Wallas diesel oven, Webasto CH (no stove), small induction hob, coffee machine etc.. Engine is the latest Beta 38 Greenline with standard budget 100A alternator.

Customer finds the standard setup struggles to charge the large AGM battery bank. The factory Chinese-copy 100A alternator has a massive ~75mm aluminium pulley. Due to non standard shaft thread size unable to fit a freewheeling pulley. Beta offer to make a 60mm aluminium pulley but customer wants to get things right. I fit a 200 amp Bosch alternator with Mastervolt Alpha Pro & increase cable sizes to suit.

Normally, with the small Beta 38 you couldn’t install such a big alternator. The 6PK belt & freewheeling alternator pulley combination is close to belt limitations but will run a 200A alternator. Limiting factor is engine power. The large ~230mm crank pulley enables near full alternator output at the 800rpm tickover – which the engine just isn’t capable of running. This is the case with other popular engines too: Beta 43, Beta 50, Isuzu & Barrus. With the Alpha Pro it’s possible. Absorption voltage is set to 14.6V and ‘small engine mode’ is setup to reduce output at lower rpm: At 800rpm tickover programmed to achieve ~65 amps. In gear tickover drops engine speed slightly and output to ~55 amps. Slowly raising revs, output gradually increases to 240 amps (~3.5kw) at 1200rpm. We back the max alternator percentage output to 70% to suit the max charge rate of the Victron AGM’s.

Alternator temperature sensor is added and Alpha Pro programmed to keep temperatures ultra safe. With the freewheeling pulley customer notices everything is significantly smoother. Alternator performance is transformed.


Example of Alpha Pro + large alternator install for charging Lithiums..

My customer has installed a 390AH Valence battery system along with other kit (Victron 3000 Multiplus, Victron BMV 712 Smart, Solar etc) and has found the standard 80 amp alternator on the Isuzu Canaline 42 doesn’t work with Lithium. I install my custom 6PK poly-v crank pulley upgrade along with a high quality & powerful 175 amp Iskra alternator & freewheeling pulley.

A Mastervolt Alpha Pro is added and absorption voltage is set to the recommended 14.2V. It’s important to keep max absorption voltage conservative with most lithium’s to protect cells from over voltage. Often the BMS is built in and a disconnect due to cell over voltage can potentially damage the alternator. Small engine mode brings alternator current down to ~ 55amps @ 800rpm tickover dropping to ~35amps at in-gear tickover. Full power is dialled back to ~130amps at 1100rpm. Without small engine mode alternator load is just too high – Engine runs very badly almost stalling on tickover and won’t rev.

An alternator temp sensor is added – as alternator temperatures rise over a pre-set level, output is gradually backed off and never exceeds a very safe 90 degrees C. The setup is superb and takes full advantage of the large alternator without compromising reliability or engine performance/refinement. I add a control switch in series with the ignition switch so alternator can be shut down when required. This is an important feature particularly useful for drop-in type lithiums with no alternator BMS control. My customer is delighted with the new setup. The video clip below shows the Alpha Pro’s current control – There’s a slight lag with sound due to the Victron BMV Smart connection.