Battery manufacturers offer a wide range of models.  In addition to various voltage and capacity offerings, popular battery models often follow a standard size (dimensions) which is commonly referred to as BCI sizing.  These guidelines have been outlined by Battery Council International for all manufacturers.  By selecting from models within a noted (BCI) size, a customer is able to choose a particular brand without having to determine if that model's dimensions will fit their particular application. This is common in applications such as industrial equipment or marine applications where the equipment or compartment has been designed to work with and house a battery or cell of a particular dimension.

A battery that follows the same BCI sizing and similar capacity from one manufacturer will often require varied charge & float voltages requirements from other brands. This is common as the charge requirements are based on the specific plate and cell construction. Heavy-duty plates often require a slightly higher charge voltage and current to reach 100% SOC. To prevent a charge imbalance and possible damage to new or existing batteries or cells, it is very important to always replace a model with one of the same brand & model to best match the charge requirements, allowing the battery bank to charge at the same rate and all cells to balance and reach 100% SOC.

  • Never replace a battery with one of a different voltage
  • Never replace a battery or cell in a battery bank with a model from another brand as charge requirements vary by manufacturer.
  • Do not replace a battery or cell in a battery bank with a model with higher/lower-rated capacity unless this has been specifically recommended by the battery manufacturer.  In some situations, based on the condition or age of the battery bank, a cell of lower capacity may be better suited to match the remaining capacity.


Replacement of batteries in an existing bank after 1.5-2 years of use is generally not recommended.  However, if replacing a failed cell/battery or full string of batteries in a system is necessary you may do so as long as the existing batteries or string(s) are in good condition.  All cells should be desulfated, evenly charged and provide normal voltage readings.  Testing specific gravity to confirm the state of charge and to identify weak or failed cells before replacement is also very important.  Often, if a cell has died due to charge-related issues, other cells in the battery bank will show similar signs or quickly follow.

When introducing batteries to an existing string you will first need to put them on a balance charge of 2.5 VPC, measuring the voltage on all units until each battery in the bank reads 2.5 VPC.  We do not recommend cycling prior to balancing the battery bank.  A balancing charge will eliminate the possibility of uneven charge and ensure the bank is at the same state of charge (SOC) ready to be cycled as normal.


NOTE: the attached cell replacement form should be completed and submitted with your order when requesting a replacement cell.

Many of our Rolls Battery Series 5000 models offer modular cell construction.  This means that each 2-volt cell is bolted together in series, rather than traditional welding, to provide the desired battery voltage.  The cells are housed in an outer container (red) and covered with a snap-on lid for protection.  The outer case provides an extra layer of protection against damage due to spills, punctures or cracks from freezing, etc.  

To replace a cell in a modular Series 5000 model, first, disconnect both terminal connections and remove the battery cover.  Most covers snap-on or may have small plastic pins along the edge which may be easily removed with a screwdriver.  You will notice a black silicone has been applied around each terminal.  This may be removed and will be replaced following the cell replacement.  A standard automotive silicone will suffice.

Note: cells are heavy and may require more than one person to safely lift from the case.

A photo is provided showing a cut-away of the modular cell construction and cell interconnections.

Each cell will be bolted together inside the outer case.  The interconnects for each terminal are keyed so they may only be attached in the correct position.  Locate the cell to be replaced and remove the bolt for both positive and negative connections.  Lift the cell out of the case and replace it with the new cell, making sure the connections are in the proper orientation.  Reinstall the connecting bolts and replace the case cover.  Last, re-apply a bead of silicone to seal around each terminal and reconnect cabling. 

Once the new cell has been installed, place the battery on a balance charge as instructed above.