Forklift Battery Cables and SB Connectors

What the battery connection has to do

An industrial truck battery connects to the truck, and separately to its charger, through a heavy DC connector on a short length of flexible cable. In a multi-shift operation that connection may be made and broken several times a day, often by operators in a hurry, and the cable may be dragged across the battery tray. The connector must carry the truck's peak current without overheating, stay mated under vibration, and make it hard to connect the wrong battery.

SB-style connectors

In North America a widely used forklift battery connector is the Anderson Power Products SB series, a genderless two-pole design: the same housing mates with itself, so one part number serves both sides of a connection. Sizes are named after their maximum current rating:

Connector	Rated current	Where it is commonly found
SB50	50 A max	Scissor lifts, golf carts and small equipment
SB120	120 A max	Mid-size equipment; check the equipment maker's data
SB175	175 A max	Pallet jacks and stackers
SB350	350 A max	Sit-down and stand-up forklifts; the most common forklift size

The ratings and typical uses above follow the connector guides published by forklift parts suppliers such as Forklift America. Contacts are selected to match the cable size: an SB175 takes cable up to 1/0 AWG, while SB350 contacts are offered for cable from 1/0 AWG up to 4/0 AWG and larger, according to suppliers' listings. Check the connector maker's data for the exact contact part number for your cable.

Housing color and voltage

SB housings come in several colors, and matching colors mate while different colors are keyed apart. The forklift industry has used color to help keep a battery of the wrong voltage out of a truck. Forklift America describes the suggested scheme as follows, and notes that it is not always followed:

Housing color	Suggested system voltage
Yellow	12 V
Orange	18 V
Red	24 V
Gray	36 V (also the most common color, often used for other voltages)
Blue	48 V
Green	72 V
Black	80 V

Because the scheme is only a convention, and gray is used widely, never assume voltage from color. Label batteries and trucks, and check. Because SB connectors are genderless, it is also physically possible to connect a charger directly to a truck; site procedures should prevent that.

European material handling equipment often uses DIN-style battery connectors instead of SB. These are a different family and do not mate with SB housings.

Battery cable

Flexible, fine-stranded copper. Cables that are unplugged daily need flexible stranding, not stiff building wire.
Size for the truck's current and cable length, within the connector contact's range. The truck or battery maker's documentation states what is required.
Jacket resistant to abrasion, battery electrolyte and oils. Flexible battery cables are made with rubber and thermoplastic jackets; check the cable maker's chemical resistance data.
Correct lugs at the battery end, crimped with the tooling the lug maker specifies, and sealed.
Polarity identification on both conductors, with red and black jackets or durable marking.

How battery connections fail

Pulled by the cable. Operators yank the lead instead of the handle, loosening contacts and breaking strands at the crimp. Handles on the housing help.
Heat at the contact. A worn, contaminated or loosely retained contact heats up under load. Discolored housings are a warning sign.
Mismatched contacts. Contacts crimped onto the wrong cable size, or the wrong contact type in a housing, carry less current than intended.
Crushed or chafed cable from being trapped when the battery is installed.

Chargers, battery changes and opportunity charging

How a site charges its trucks changes what the connection has to endure. Operations that change batteries between shifts make and break the connection at the battery room as well as the truck. Operations that opportunity-charge, plugging in during breaks, connect the truck far more often. In both cases:

match the charger's connector series and color to the batteries it serves, and label the charger with the battery voltage;
keep charger cables supported off the floor, where they can be run over;
give operators a handle to pull, and train them to use it;
include charger cables and connectors in the same inspection routine as the trucks.

Inspection checklist

Look for melted or discolored housings and pitted contacts.
Check the housing color, labeling and voltage match between battery, truck and charger.
Pull gently on each cable at the connector to check contact retention.
Check cable jackets for cuts, electrolyte damage and crush.
Check lug connections at the battery for corrosion and tightness, following the battery maker's procedure.

Common questions

What is the difference between SB175 and SB350?

Size and current rating: 175 A and 350 A maximum respectively. They are different housings and do not mate with each other.

Does a gray connector mean 36 V?

Not reliably. Gray is suggested for 36 V but is widely used for other voltages. Check the battery label.

Will two SB connectors of different colors mate?

No. SB housings are keyed by color so that only the same color mates.

What gauge cable goes in an SB350?

SB350 contacts are offered for a range of cable sizes, from 1/0 AWG upward. Choose the contact that matches your cable, and the cable that matches the truck's requirement.

What to send a supplier

Connector series, housing color and contact part numbers.
Cable size, stranding, jacket and colors.
Lengths, lug type and hole size at the battery end.
Handles, boots and labeling required.
Tests: continuity, polarity and crimp pull tests where specified.

Specifying the environment for any cable is covered in how to specify transport cables.