Building custom chargers for all industries and services

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Total Battery Solutions can offer our customers a custom designed charger, should one of our standard range of chargers not meet the requirements for the application.

Chargers MUST be compatible with the battery pack and operate within the limits specified by the cell manufacturers. The charger also forms an integral part of the safety logic.

Abuse of cells by inappropriate charger systems is a common cause of battery pack reduction in performance or even failure. Chargers can be embedded in the battery pack BMS, host equipment or be free standing. In the latter case they may be operated by a DC source such as a lap top 65W adapter or have their own internal universal AC input.

battery_circuit_boardEvery chemistry will have its own type of charging algorithm(s). For example in Lithium rechargeable then CC/CV [meaning constant current followed by constant voltage] is universally mandated by the lithium cell manufacturers, charge termination is by taper current, usually about 10% of the full charge current. NiMH uses a constant current with ΔV and/or Δt termination.

The charger monitors the pack voltage and will apply a fractional charge if the battery is too low to accept a full charge rate. For example the maximum charge rate recommended for a lithium NMC cell is 0.7C where “C” is the capacity, so for a 2.6AH pack that is a full charge rate of 1.8Amps whereas with a low battery <2.8V/cell the rate will be about 0.18Amps until the cell voltages >2.8V measured as a total pack voltage.

The constant voltage for Lithium NMC is 4.2V per series cell. This is critical for cell life cycle and some users set CV to 4.1V.cell for an increase in life cycle performance.

Charge temperature range is also controlled either by digital temperature signal or a thermister with negative co-efficient performance, embedded in the battery pack.

Smart packs can use level 2 or level 3 SMBUS chargers which interface with the BMS Fuel Gauge. In a level 2 system the Fuel Gauge commands the charger which acts as intelligent current/voltage source. In a level 3 charger the Fuel Gauge supplies data on demand. The TBS CX-2 charger is configured as a level 2 system but can be programmed to stand alone. It is compatible with the Power Block™ range of standard battery packs.

Charger Design was last modified: May 25th, 2014 by julie claydon

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