Century C12-120XDA 12V 120Ah AGM deep-cycle battery for caravans, 4WDs, boats and solar — Group 31 footprint with M8 insert terminals in 12V_D polarity

Battery top-view polarity diagram for a six-cell 12 volt battery, positive terminal at the right side, labelled 12 Volt D polarity

Battery terminal line drawing showing a threaded insert in section with its bolt alongside, dimensioned for reference

Century

C12-120XDA — 12V 120Ah AGM Deep Cycle Battery

Name: Century C12-120XDA — 12V 120Ah AGM Deep Cycle Battery
Brand: Century
SKU: 148141
Price: 515.00 AUD
Availability: InStock

148141

Century C12-120XDA — 12V 120Ah AGM deep-cycle house battery for caravans, 4WDs, boats and off-grid solar. M8 terminals, 328×172×215mm Group 31 footprint, 32 kg, multi-angle fitment up to 90 degrees, 36-month Century warranty.

12V 120Ah

36 A max charge

90° multi-angle

$515.00

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Universal fitment12V 120Ah AGM deep-cycle house battery for caravans, 4WDs, boats and off-grid solar

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A 12V 120Ah AGM deep-cycle battery that runs house loads in caravans, camper trailers, 4WD dual-battery setups, boats and solar off-grid cabins. Powers fridges, lights, water pumps, inverters for TVs and laptops, and 12V accessory sockets through a full discharge cycle. The absorbed-glass-mat construction holds the electrolyte in a sealed cell so it can mount at any angle up to 90 degrees without spilling.

The case is ABS polypropylene with a UL94-HB flame rating, 328 by 172 by 215 mm with M8 threaded-insert terminals in 12V_D polarity. 32 kg over 220 mm to the top of the posts. Central venting and an integrated flame arrestor handle gas release, and heavy-duty carry handles sit flush on the short ends for a two-person lift.

Not a cranking battery, so don't use it to start an engine. Charge from an AGM-profile DC-DC or a solar MPPT with an AGM setting, 14.6 to 14.8 volts for the bulk stage and 13.6 to 13.8 volts for float. Keep the maximum charge current under 36 amps, keep the battery upright or on its side rather than inverted or end-mounted, and fuse the positive lead within 300 mm of the battery post.

Related in our range

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AGM construction — holds electrolyte sealed in the mat
Full-frame plates — handles deep discharge cycles
90-degree mount — side-mount in tight spaces
M8 inserts — bolt-on cable lugs direct
Flame arrestor vent — safe sealed gas release
Carry handles — flush ends for a two-person lift
ABS UL94-HB case — flame-rated container
36A max charge — matches common DC-DC chargers

Electrical

Voltage: 12V

Capacity: 120Ah @ C20

Max discharge: 1200A (5s)

Max charge: 36A

Float voltage: 13.6-13.8V

Equalise: 14.6-14.8V

Physical

Dimensions: 328×172×215mm

Over-terminals: 220mm

Weight: 32kg

Terminals: M8 insert

Polarity: 12V_D

Build

Chemistry: AGM VRLA

Case: ABS UL94-HB

Vent: Flame arrestor

Mount: Up to 90°

Length: 328mm

Width: 172mm

Height: 215mm

Over-terminals: 220mm

Weight: 32kg

The C12-120XDA has a 328 by 172 by 215 mm footprint with terminals sitting 220 mm above the base, so plan clearance to the lid or seat base above the battery. Weight is 32 kg so lift with the end handles two-handed; the Group 31 tray or an aftermarket deep-cycle tray with M8 hold-down studs fits the base. Secure with a hold-down bar or clamp through the lid lip.

M8 bolts into the threaded inserts for the positive and negative cable lugs, 12 Nm torque. 25mm² (3 B&S) cable minimum for the house run, 50mm² for a run over 2 metres or if a DC-DC draws the full 40 amps. Fuse the positive within 300 mm of the battery post with a MIDI 60A or MEGA 80A to match the DC-DC charger's maximum output.

Charge from an AGM-profile DC-DC charger or an MPPT solar controller with an AGM setting. Bulk at 14.6 to 14.8 volts, float at 13.6 to 13.8 volts at 25°C, maximum charge current 36 amps. Keep off a wet-cell flooded profile, since AGM charge voltages are different and a flooded profile under-charges the AGM over time.

12V 120Ah AGM deep-cycle house battery for caravans, 4WDs, boats and off-grid solar

Fits caravans, camper trailers, 4WD dual-battery house positions, boats, campervans and fixed solar banks

Suits any tray taking a 328×172×215mm Group 31-footprint deep-cycle AGM in 12V_D polarity

Sealed, spill-proof case allows mount angles up to 90 degrees

Not a cranking battery, don't use to start an engine

Not for inverted or end-mounted installations

Q: What's the difference between a deep-cycle and a starter battery?
A deep-cycle battery is built to be discharged slowly to half or less of its capacity, then recharged, over hundreds or thousands of cycles. A starter battery delivers a short burst of high current to crank an engine, then is recharged to full by the alternator within a few minutes. Running a deep-cycle in a cranking role is weak; running a starter in a cycling role destroys it. The C12-120XDA is a dedicated deep-cycle, not a starter.

Q: What does AGM mean?
Absorbed Glass Mat. The electrolyte is held in a fine glass-fibre mat between the plates instead of flooded as liquid. That means it can't spill, it tolerates vibration better than a flooded cell, and it mounts on its side. The trade-off is you have to charge it with an AGM-profile charger that keeps the voltage in the AGM range.

Q: How many cycles will I get out of it?
Depends on how deep you discharge it. Century rates AGM deep-cycle for roughly 500 cycles at 50 per cent depth of discharge, climbing into the thousands at 30 per cent depth or less. Keep it above 50 per cent state-of-charge and recharge promptly after use to maximise cycle life.

Q: Can I use this as a cranking battery for a 4WD or caravan tow vehicle?
No. The C12-120XDA is a dedicated deep-cycle built for slow discharge, not for the few hundred cold-cranking amps a diesel engine needs on start-up. For a cranking role see the Century Dual Force+ 27X MF (dual-purpose cranking plus light cycling) or a dedicated Century truck or 4WD starter battery.

Q: What size cable and fuse should I use?
25mm² (3 B&S) cable is the minimum for a house run under 2 metres; 50mm² for anything longer or if the DC-DC pulls the full 40 amps. Fuse the positive within 300 mm of the battery with a MIDI 60A or MEGA 80A so a short-circuit trips the fuse before the cable overheats.

Q: Can I mount it on its side?
Yes, the sealed AGM construction supports mounting at any angle up to 90 degrees. Don't mount it inverted (upside-down) or end-mounted. The vent paths and the pressure-relief valve don't work correctly in those orientations.

Q: What charger do I need?
An AGM-profile charger. A Century CC1212-XLi, a Victron Blue Smart IP22 on the AGM setting, an Enerdrive ePOWER or a Redarc BCDC with AGM profile selected will all work. Bulk 14.6 to 14.8 volts, float 13.6 to 13.8 volts, maximum charge current 36 amps. Don't charge off a wet-cell flooded profile since AGM wants higher bulk voltage.

Q: Does it come with cables, terminals or a tray?
Just the battery itself with M8 threaded-insert terminals. You supply the cable lugs, cable, tray and hold-down. M8 flag-style lugs or M8 ring lugs bolt straight into the insert.

Q: Can I run it in parallel with another battery?
Yes, but match the model and age. Don't parallel a new C12-120XDA with a tired three-year-old deep-cycle, and don't mix AGM with flooded or lithium. Use equal cable lengths from each battery to the common bus, and fuse each battery lead at the positive post.

Q: Will it work with a lithium charging profile?
No. Lithium profiles bulk-charge to 14.4 volts with no float stage, which under-charges AGM and leaves it sulphating. If a DC-DC can switch between lithium and AGM, make sure it's set to AGM when charging this battery.

Q: What does the 36-month warranty cover?
Manufacturing defects in materials and workmanship under Century's warranty statement. Normal wear from cycling, abuse, over-discharge and the wrong charging profile aren't covered. Full terms in our warranty policy.

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