Mastervolt · Battery charger

Mastervolt ChargeMaster & ChargeMaster Plus

ChargeMaster is Mastervolt’s range of fixed-mount, fully automatic battery chargers for shore power and generators, with three outputs that are galvanically isolated from the mains; the oldest manuals online date from 2008 and 2009, and of the original line only the small 12/25-3 and 24/12-3 are still sold. The discontinued 12/35-3, 12/50-3, 24/20-3 and 24/30-3 (4 kg, LED display) charge all three outputs at full current, while the large LCD models 12/70-3, 12/100-3 and 24/40-3 to 24/100-3 give only 10 A on outputs 2 and 3, meant for starter batteries. The ChargeMaster Plus, presented in 2016, adds lithium profiles; its 12/75-3, 12/100-3, 24/40-3 and 24/60-3 came first as MasterBus-only units with part numbers ending in 0, and today only the “CZone” versions ending in 5 are listed, with CZone and NMEA 2000 built in and a third output that can also charge from the alternator (VSR) or feed a smaller battery. Since the early 2020s the compact 2.5 kg 12/35-3, 12/50-3, 24/20-3 and 24/30-3 and the two-output 24/80-2 and 24/110-2 complete the range. Temperature sensor, MasterBus parts and remote panels are shared, but manual, settings and fuse table depend on the model and its hardware version — read the part number and serial number on the label on the right-hand side before ordering; Mastervolt’s Mass and older IVO chargers and the small 230 V-only ChargeMaster 12/10-1, 12/15-2 and 24/6-1 are separate products and not covered here.

Manuals & documents

The links go to Mastervolt’s own documents — some as archived copies of pages the maker has since taken down. We host no manuals or drawings.

Wear parts & part numbers

PartOEM numberAlso fitsNote
Charger44010250 · 440201201,2,3—ChargeMaster 12/25-3 and 24/12-3, the two original models Mastervolt still lists; the OEM Quick Connect version of the 12/25-3 is 44010252.
Charger44310355 · 44310505 · 44320205 · 443203054,5,6,7,8,9,3,10—Compact ChargeMaster Plus 12/35-3, 12/50-3, 24/20-3 and 24/30-3 (2.5 kg, three full outputs, MasterBus, CZone and NMEA 2000). Same footprint as the old ChargeMaster 12/35-3 to 24/30-3 (291 × 210 mm) but 26 mm flatter.
Charger44310755 · 44311005 · 44320405 · 4432060511,12,13,14,15,16,3,10—ChargeMaster Plus 12/75-3, 12/100-3, 24/40-3 and 24/60-3 in the current CZone version (5.9 kg); they replace the MasterBus-only first series 44310750, 44311000, 44320400 and 44320600 in the same housing.
Charger44320805 · 4432110517,18,19,10—ChargeMaster Plus 24/80-2 and 24/110-2 CZone: two outputs, the second for a 12 V or 24 V starter battery.
Temperature sensor4150050020,9,15,21—Battery temperature sensor with 6 m cable and RJ11 plug, supplied with every ChargeMaster and ChargeMaster Plus; fix it to the case of battery bank 1 and plug it into the “Temp sense” socket.
Temperature sensor4150080022,23,24—The same sensor with 15 m of cable, for batteries far from the charger.
Fuse6384001600 · 6384003200 · 6384004000 · 638400630023,9,24,25—Mastervolt industrial DC fuses, DIN 00, 16 / 32 / 40 / 63 A, as listed in the ChargeMaster manuals: 16 A for the 24/12-3 and 32 A for the 12/25-3 (hardware up to H), 32 A for the 24/20-3, 40 A for the 12/35-3 and 24/30-3, 63 A for the 12/50-3. The ChargeMaster Plus manuals give ratings only (see the specs).
Fuse holder / fuse base638100100023,9,25—Fuse base DIN 00 (up to 160 A) for the industrial fuses above.
Fuse604015 · 60403026,27—ATC blade fuses 15 A and 30 A (packs of two) for the ChargeMaster 24/12-3 and 12/25-3 from hardware version I (2015 manual).
Fuse holder / fuse base60701726,27—In-line ATC fuse holder for those blade fuses.
Network connector (T-piece, terminator)7704000023,26,9,8,25—MasterBus terminator; a MasterBus network needs one at each end. One comes with every ChargeMaster Plus.
Network cable77040050 · 77040100 · 77040300 · 77040600 · 770410009,26,15,25,28,29—MasterBus cables (straight UTP patch cables with RJ45) of 0.5, 1, 3, 6 and 10 m; 0.2, 15 and 25 m are listed too (77040020, 77041500, 77042500). Daisy-chain only: no ring and no T-pieces.
Network cable77060050 · 77060100 · 77060200 · 7706050030,31,32,33,15—Mastervolt-CZone drop cable RJ45 to M12, 0.5 / 1 / 2 / 5 m, to join a CZone or NMEA 2000 backbone through a tee; the 1 m cable comes with the ChargeMaster Plus.
Data converter / gateway7703010034,9,26,25—Mastervolt USB Interface (formerly MasterConnect USB): connects a Windows PC with MasterAdjust, or the CZone Configuration Tool, to the charger.
Remote control7701031035,8,36—EasyView 5 MasterBus touch display: shows charge state and changes settings remotely.
Remote control77010600 · 7701050037,38,39,40—SmartRemote, retail and OEM version: small plug-and-play MasterBus panel; Mastervolt lists every ChargeMaster Plus as supported.
Remote control77010300 · 770103059,26,25,27—MasterView Easy and MasterView Easy MkII, the older MasterBus touch panels listed in the 2009 and 2015 ChargeMaster manuals.
Relay7703050041,11,42—Multipurpose Contact Output: potential-free MasterBus relay contact, used as the charger status (alarm) contact, e.g. for low voltage or loss of shore power.
Battery monitor (shunt)77020100 · 770201159,43,11,25,44—MasterShunt 500 (in the older manuals) and today’s MasterShunt 500 CZone: battery monitor whose voltage reading the charger can use to compensate cable losses.

Numbers checked against the sources below on 23 October 2026. Always confirm against your serial number and exact type before ordering.

Service intervals

TaskInterval
Electrical connectionsAt least once a year: check the whole installation, AC and DC, for loose connections and damaged or burnt wiring, and put defects right at once15,8,9,23
Storage / winterisingMay stay on over winter with the batteries connected. To take it out of service: shore power off, charger off, DC fuses out, AC breaker or RCD off, check with a meter that inputs and outputs are dead, then disconnect; store dry and dust-free15,8

From the Mastervolt manuals for the ChargeMaster and ChargeMaster Plus: the charger needs no maintenance and has no user-serviceable parts — only the connection compartment may be opened. Clean the case with a soft, clean cloth only, never with solvents, alcohol, petrol or abrasives, and keep the ventilation openings clear. Mastervolt gives no service hours.

Specifications

TypeFixed-mount, fully automatic charger for shore power or a generator; three outputs galvanically isolated from the mains (two on the ChargeMaster Plus 24/80-2 and 24/110-2) that share the total charge current; 3-step+ charging (bulk, absorption, float) that may stay connected all year1,8,15,19
ModelsChargeMaster, still sold: 12/25-3 (44010250; OEM Quick Connect version 44010252 with a WAGO 770-113 plug on 25 cm of cable) and 24/12-3 (44020120), with attached 2 m AC cable, LED display and settings by the Set button or through MasterBus1,2,23
ModelsChargeMaster, discontinued: 12/35-3 (44010350), 12/50-3 (44010500), 24/20-3 (44020200) and 24/30-3 (44020300) with LED display and DIP switches; large LCD models 12/70-3 (44010700), 12/100-3 (44011000), 24/40-3 (44020400), 24/60-3 (44020600), 24/80-3 (44020800) and 24/100-3 (44021000)9,45,46,47,48,49,50,51
ModelsChargeMaster Plus 12/75-3, 12/100-3, 24/40-3, 24/60-3: first series MasterBus only (44310750, 44311000, 44320400, 44320600), current CZone versions 44310755, 44311005, 44320405, 44320605. Compact 12/35-3 (44310355), 12/50-3 (44310505), 24/20-3 (44320205), 24/30-3 (44320305). Two outputs: 24/80-2 (44320805), 24/110-2 (44321105)16,52,15,8,19,53
Charge currentTotal, shared by the outputs. ChargeMaster: 12/25-3 25 A, 12/35-3 35 A, 12/50-3 50 A, 12/70-3 70 A, 12/100-3 100 A; 24/12-3 12 A, 24/20-3 20 A, 24/30-3 30 A, 24/40-3 40 A, 24/60-3 60 A, 24/80-3 80 A, 24/100-3 100 A. ChargeMaster Plus: 12/35-3 35 A, 12/50-3 50 A, 12/75-3 75 A, 12/100-3 100 A; 24/20-3 20 A, 24/30-3 30 A, 24/40-3 40 A, 24/60-3 60 A, 24/80-2 80 A, 24/110-2 110 A1,2,9,45,46,47,48,49,51,8,15,19
Charge outputsChargeMaster 12/25-3 to 24/30-3 and the compact ChargeMaster Plus: three full outputs, all charged alike. Large ChargeMaster 12/70-3 to 24/100-3: outputs 2 and 3 give only 10 A each. ChargeMaster Plus 12/75-3 to 24/60-3: output 3 (DC 3 IN/OUT) limited to 40 A (12 V) or 20 A (24 V) by default and to 10 A by DIP switch for a small starter battery; it can also pass alternator current to banks 1 and 2 (VSR mode) and, on the 24 V models, charge a 12 V battery. 24/80-2, 24/110-2: second output 5–15 A at 12 V or 5–20 A at 24 V8,9,45,15,17
VoltageInput 120/230 V AC, 50/60 Hz, no switching needed: ChargeMaster 90–265 V, ChargeMaster Plus 80–275 V (not protected against surges above 275 V AC). Output 12 V or 24 V, fixed by model1,11,15,23
Charge voltages12 V models at 25 °C (24 V models double): bulk 14.4 V, absorption 14.25 V, float 13.25 V for flooded or 13.8 V for gel/AGM; lithium-ion (Mastervolt MLI) 14.25 / 14.25 / 13.5 V on the ChargeMaster Plus. Bulk and absorption each end after 8 h at the latest; every 14 days the charger repeats a short absorption phase (one hour on the ChargeMaster Plus). Temperature compensation with the supplied sensor: −30 mV/°C (12 V), −60 mV/°C (24 V)15,8,9,11,13
Recommended battery bankMastervolt’s recommended bank: ChargeMaster Plus 12/35-3 140–350 Ah, 12/50-3 200–400 Ah, 12/75-3 320–800 Ah, 12/100-3 400–1000 Ah, 24/20-3 80–200 Ah, 24/30-3 120–240 Ah, 24/40-3 160–400 Ah, 24/60-3 200–500 Ah, 24/80-2 280–700 Ah, 24/110-2 400–1000 Ah; ChargeMaster 12/25-3 50–250 Ah, 24/12-3 24–120 Ah4,5,11,12,6,7,13,14,17,18,1,2
Power consumptionAt full load: ChargeMaster 12/25-3 450 VA, 24/12-3 435 VA, 12/35-3 575 VA, 12/50-3 825 VA, 24/20-3 660 VA, 24/30-3 925 VA; ChargeMaster Plus 12/35-3 600 VA, 12/50-3 850 VA, 24/20-3 700 VA, 24/30-3 1000 VA, 12/75-3 1300 VA, 12/100-3 1700 VA, 24/40-3 1400 VA, 24/60-3 2000 VA, 24/80-2 2800 VA, 24/110-2 3800 VA. From the battery when idle: under 2 to 10 mA, depending on model23,9,8,15,19
Breaker / fuseDC fuse in each positive output cable: ChargeMaster 12/25-3 32 A and 24/12-3 16 A (2011 manual, hardware up to H) or 30 A and 15 A (2015 manual, hardware I on); 12/35-3 40 A, 12/50-3 63 A, 24/20-3 32 A, 24/30-3 40 A. ChargeMaster Plus 12/35-3 40 A, 12/50-3 60 A, 24/20-3 25 A, 24/30-3 40 A, 12/75-3 85 A, 12/100-3 125 A, 24/40-3 50 A, 24/60-3 80 A; 24/80-2 and 24/110-2: to suit the cable. AC side: a switch or breaker to disconnect it and an RCD where local rules require one; on the compact Plus the input breaker must be rated above 120 % of the maximum input current at 120 V23,26,9,8,15,19
Power cable sizeMinimum battery cable, under 3 m / 3–5 m: ChargeMaster Plus 12/35-3 10/16 mm², 12/50-3 16/25 mm², 24/20-3 6/10 mm², 24/30-3 10/16 mm², 12/75-3 25/35 mm², 12/100-3 35/50 mm², 24/40-3 16/25 mm², 24/60-3 25/35 mm². ChargeMaster 12/35-3 to 24/30-3 (2008 quick guide, under 2 m / 2–5 m): 12/35-3 16/25 mm², 12/50-3 25/35 mm², 24/20-3 10/16 mm², 24/30-3 16/25 mm²8,15,54
Data connectionsChargeMaster: MasterBus (RJ45); into CZone only through a MasterBus–CZone bridge set up in MasterAdjust. First-series ChargeMaster Plus (part numbers ending in 0): MasterBus. CZone versions and compact models: MasterBus, CZone and NMEA 2000 (charger, battery and DC status PGNs 127507, 127508, 127506) through the RJ45–M12 drop cable supplied (1 m). Alarm contact: Multipurpose Contact Output 7703050055,16,15,8,4,41
DisplayLED status display on the ChargeMaster 12/25-3 to 24/30-3 and on every ChargeMaster Plus (stage of each output; on the current Plus also load level and error codes, stepped through with the ON/OFF button); LCD on the large ChargeMaster 12/70-3 to 24/100-31,9,15,45
SoftwareMasterAdjust (Windows, free download from Mastervolt) through the Mastervolt USB Interface 77030100 for every MasterBus setting; on a CZone network the CZone Configuration Tool15,8,34
WeightChargeMaster 12/25-3, 24/12-3 1.8 kg; 12/35-3 to 24/30-3 4 kg; 12/70-3 to 24/60-3 7 kg; 24/80-3, 24/100-3 8 kg. ChargeMaster Plus compact 2.5 kg; 12/75-3 to 24/60-3 5.9 kg; 24/80-2, 24/110-2 6.3 kg1,9,45,47,49,8,15,19
DimensionsHeight × width × depth: ChargeMaster 12/25-3, 24/12-3 234 × 132 × 60 mm; 12/35-3 to 24/30-3 291 × 210 × 131 mm; 12/70-3 to 24/60-3 362 × 277 × 150 mm; 24/80-3, 24/100-3 432 × 277 × 150 mm. ChargeMaster Plus compact 291 × 210 × 105 mm; 12/75-3 to 24/60-3, 24/80-2 and 24/110-2 384 × 250 × 127 mm1,9,45,47,48,49,4,11,17
Waterproof ratingIP23 on every model: for dry, ventilated spaces only, mounted vertically with the cables pointing down1,9,8,15
Operating temperatureChargeMaster Plus −25 to 80 °C ambient: full power up to 40 °C, then 1 % less per °C to 60 °C and 8 % less per °C to 70 °C, no output above 70 °C. ChargeMaster 12/35-3 to 24/30-3 −25 to 65 °C, 3 % per °C less above 40 °C; 12/25-3, 24/12-3 −25 to 60 °C, reduced power below 0 °C and above 40 °C15,8,9,1
CoolingSpeed-controlled fan plus natural convection; noise under 45 dBA at 1 m (compact ChargeMaster Plus), under 52 dBA (ChargeMaster Plus 12/75-3 to 24/60-3, ChargeMaster 12/35-3 to 24/30-3), under 60 dBA (24/80-2, 24/110-2)8,15,19,9
MountingVertical, cables down, at least 100 mm clear on every side; never directly above the batteries it charges (battery gases corrode it); the fan can be heard near berths15,8
Warranty2 years from purchase on the ChargeMaster Plus, repair or replacement only; damage from reversed polarity is not covered15,8
Years builtChargeMaster: oldest manuals online from 2008 (quick guide) and 2009; of these only the 12/25-3 and 24/12-3 are still listed. ChargeMaster Plus: presented by Mastervolt in November 2016; CZone versions listed on Mastervolt’s site by 2019, the compact models by 202154,9,56,57,58,59

Good to know

  • Before downloading a manual or buying fuses, read the label on the right-hand side: the letter in the serial number is the hardware version (E815H0001 is version H). For the 12/25-3 and 24/12-3 the manuals split between H and I — the later ones take 30 A / 15 A ATC fuses instead of 32 A / 16 A DIN fuses, and their lithium bulk voltage is 14.25 V instead of 14.6 V; for the 12/35-3 to 24/30-3 the split is between G and H.23,26,60,1
  • A first-series ChargeMaster Plus (part number ending in 0) charges only output 1 out of the box. Pick the outputs you use by holding MODE while switching on the AC and stepping through with short presses, or in MasterAdjust — otherwise the banks on outputs 2 and 3 never see a charge.61
  • On today’s ChargeMaster Plus the DIP switches decide the setup: in a CZone network switches 1 and 2 OFF and the device address on 3–10 (at least one ON); stand-alone or on MasterBus switch 1 ON and the battery type on 3–5 — all OFF means flooded, the factory setting. Check them after fitting a replacement unit: a new charger also does nothing until you hold ON/OFF for 3 seconds.15,8
  • The lithium setting matches Mastervolt MLI batteries only; for any other lithium battery enter the maker’s voltages as a user-defined profile in MasterAdjust. Lithium banks need no temperature sensor, but lead batteries that leave the 15–25 °C range do.15,8
  • Replacing a large ChargeMaster (12/70-3 to 24/100-3) whose outputs 2 and 3 gave only 10 A: on a ChargeMaster Plus 12/75-3 to 24/60-3 set DIP switch 7 to keep output 3 at 10 A for a small starter battery (under 50 Ah); output 2 always gets full current, so fuse and size its cable for that.45,15
  • Put the DC fuses in last, after checking the polarity, and expect a spark when you do (the charger’s capacitors) — so not with gassing batteries in a closed space. Fuses do not protect against reversed polarity; Mastervolt’s service can detect that damage and it voids the warranty.15,8

Videos & how-tos

Links to YouTube, nothing embedded. The maker’s own channel comes first; the rest are channels we found clear and correct for this model.

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Sources

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