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 price & 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. When boat owners/builders/engineers realise what they are & can do they’ll become much more popular.

‘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 kits 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 is possible. Adding the optional sensor allows you to set a temperature where alternator output begins to back off and then a high temperature at which the alternator shuts down. 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 recommended charge rate (C rating). 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 a Mastervolt hardware 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 current limiting equipment. This 80 amp limiter creates too high a load for 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 and 123\SmartBMS 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 substantial 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 an alternator installation where an Alpha Pro is required..

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 a Beta 38 with the 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 and unable to fit a small freewheeling pulley in an attempt to improve cooling & smooth engine running. 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.

Normally, with the small Beta 38 you couldn’t install such a big alternator. The 6PK belt & freewheeling alternator pulley combination is close to the limit but will just about run a 200A alternator. Limiting factor is engine power. The large ~230mm crank pulley enables high 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 ~67amps. 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 Lithiums. I install my 6PK poly-v crank pulley upgrade along with a high quality & powerful 175 amp Iskra alternator upgrade & freewheeling pulley.

A Mastervolt Alpha Pro is added and absorption voltage is set to 14.2V as recommended for most Lithium systems. 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.