Tinned Marine Battery Cable 25mm² 170A
Tinned Marine Battery Cable 25mm² 170A
Tinned copper flexible battery cable, 25mm², rated 170A. Fine-stranded, electrolytically tinned copper in a flexible PVC sheath. This is the cable to use anywhere it may see salt air, condensation, bilge water or road salt, which on a boat means everywhere.
Why tinned
Plain copper corrodes from the strand surface inward, and it does it invisibly, underneath the lug where you cannot inspect it. The joint slowly gains resistance, then gets warm, then fails. Tinning puts a barrier on every individual strand. It costs a little more and it is the correct answer for marine, for a campervan engine bay or underfloor run, and for any off-grid installation that is not in a dry indoor cabinet.
Specification
- Conductor: tinned copper to BS EN 60228 Class 5 (flexible), 322/0.30 stranding
- Cores manufactured to: ISO 6722-1:2011 Class B, 105°C
- Specified for installation to: BS EN ISO 13297:2021, Small craft. Electrical systems. Alternating and direct current installations. Note that this standard replaced ISO 10133:2012, which is still quoted across most of this market and has been withdrawn
- Cross sectional area: 25mm² (nearest AWG equivalent 4)
- Current rating: 170A nominal, conditions not stated by the manufacturer
- Overall diameter: 10.1mm
- Conductor resistance: 0.794 mΩ/m at 20°C
- Weight: approximately 0.3kg per metre
- Colours: red and black
Typical applications
The highest volume size across all three markets. 1200 to 1500W inverter at 12V, 50 to 60A DC-DC chargers, battery to busbar on 100 to 200Ah banks, engine starting on small diesels, 3000W at 24V, 5000W at 48V.
Current rating: what the manufacturer actually says
AMC publish 170A for this cable as a nominal current rating, and they publish no conditions alongside it. Their datasheet says, in full: "Nominal current amperage ratings are provided as a guide only, and can vary depending on the application, condition and environmental factors." There is no stated ambient temperature, no installation method and no bundling basis, on any size in the range.
We say so because the same number is quoted all over this market as though it were a rated ampacity, and it is not. The datasheet is linked at the foot of this page if you want to check us.
So the derating below is ours, not AMC's. We treat their figure as a single unbundled cable in open air, because that is the usual convention for a table of this kind, and we apply bundling factors following ABYC E-11 practice, which is the most widely used published basis for DC conductor derating in small craft. It is engineering judgement applied to a guide figure, and we would rather show you the judgement than hide it.
| Condition | Factor |
|---|---|
| Single unbundled cable in open air (our assumed baseline) | 1.0 |
| 2 to 3 cables bundled or in conduit | × 0.7 |
| 4 to 6 cables bundled | × 0.6 |
| 7 to 24 cables bundled | × 0.5 |
| 25 or more cables bundled | × 0.4 |
| Engine space or other high ambient | Derate further, and size on volt drop as well |
These ratings are considerably higher than BS 7671 would permit for the same conductor, because BS 7671 assumes a lower permitted conductor temperature and different installation methods. BS 7671 does not apply to small craft in any case: Regulation 110.2 excludes vessels covered by BS 8450. It is the right reference for a caravan or motor caravan, through Section 721. If you are used to BS 7671 tables, the difference is worth understanding rather than being surprised by.
Volt drop is usually what decides the size, not current
At 12V a 3% volt drop budget is 0.36V in total, there and back. That almost always calls for a larger cable than the current rating alone would suggest. BS EN ISO 13297 permits up to 10% for general circuits and 3% for equipment vital to safety.
Work it out properly with our cable size calculator, which checks current rating and volt drop independently and hands you a configured assembly at the end.
What goes with it
- Copper tube terminals: 25mm² in M6, M8, M10
- Adhesive lined heat shrink: 19mm, sized to the lug barrel rather than the cable diameter
Or let us make it up for you
Give us the length and the stud size at each end and we will cut it, crimp it with matched DIN 22-series hexagonal dies, seal both ends with adhesive lined heat shrink, label it and send you a certificate of conformity with the reel batch number, the die code, the measured crimp dimension and the measured end-to-end resistance on it. Configure an assembly.
How it is supplied
Cut to length is supplied as one continuous piece: set the quantity to the number of metres you need. Coils are supplied on a reel. Cut lengths are made to order and are not returnable unless faulty.
Datasheet
Every cable specification on this page comes from the manufacturer datasheet, and you can read it yourself: download AMC Oceanflex tinned copper PVC battery cable (PDF). We host the file here rather than link to the manufacturer, so it stays available and stays the version our figures were taken from. The derating factors above are ours, not the manufacturer's.