Using a battery for depot backup power

An on-site battery is the most common resilience measure at an electric depot, partly because it’s often being considered for other reasons anyway.

Why the battery is a natural fit

If you’re already weighing a battery to shave peaks or avoid a grid upgrade, giving it a resilience role can be a modest addition rather than a separate purchase. Configured for it, a battery can keep essential charging running through a shorter power cut, bridging the gap until supply returns or backup generation starts.

What it can and can’t do

A battery is a bridge, not an indefinite supply. It won’t run a whole depot for a long outage, but it can keep the vehicles that matter most moving for a meaningful period — a valuable safety margin for a fleet that now depends on charging. How long it lasts depends on its size and how much charging you ask of it during the outage.

Design it in

To play this role, the battery and its controls have to be set up for backup from the start — able to detect a supply loss and keep critical circuits charging. It’s a design choice, not something you can improvise mid-outage, so raise it early if resilience matters.

Where it fits

For longer or more critical needs, pair the battery with backup generation or islanding, covered in the main resilience guide. But for many depots, a battery sized with a little resilience headroom is the single most practical step — how much depends on your exposure.