Battery Safety

If properly handled, located, installed, and ventilated, EV batteries can be as safe—if not safer—than gasoline in an internal combustion-powered vehicle. Here’s how: 

Placement & Containment. Most EV conversions can add as much as 1,200 pounds to the vehicle’s stock weight—largely because of the size of the charging system and the weight of the batteries. The first step in a safe conversion is to choose a vehicle with a rust-free, sound body and chassis equipped with good brakes and wheel bearings to handle the additional weight. If possible, try to upgrade any drum brakes to disc for additional stopping power. 

Next, it is critical to distribute the battery weight throughout the vehicle and secure the batteries. Too much weight in the back of the vehicle can cause steering sensitivity, making the vehicle too responsive. Yet, too much weight over the front wheels can make every steering-wheel turn an upper-body workout. Distributing the batteries in a way to match the vehicle’s original weight over the front wheels should be the goal. The battery weight in the rear will be heavier than stock, and will require the addition of overload springs and/or shock absorbers. Also be sure to mount batteries to maintain the vehicle’s low center of gravity.

As a general rule, it’s best to keep the batteries out of the passenger compartment for safety reasons. In case of a front or rear collision or a rollover, batteries can leak acid if ruptured or turned upside down. If it’s not possible to place them outside of the passenger compartment, you can secure the batteries inside an enclosure. 

When it comes to safety, battery containment can’t be stressed enough. A plywood or plastic box is not sufficient to hold the batteries in place during a collision—unsecured batteries have the mass and momentum to break this type of enclosure and launch like deadly acid missiles. Batteries should be held firmly in place with metal battery trays and hold-downs, which can be fabricated from steel or aluminum angle stock. All framework should be welded for maximum strength, and the finished cage should be securely bolted to the vehicle floor or frame with bolts, nuts, and large-diameter washers.  

Ventilation. Flooded lead-acid (FLA) batteries are the most common propulsion batteries used in EV conversions today. FLAs will begin to produce hydrogen gas at about 2.37 V per cell during the last 20% of the charging cycle. While the possibility of enough hydrogen collecting to explode is low, caution and safety are always recommended. With batteries housed in an enclosure, fans and vents should be used to exhaust any hydrogen gas outside the vehicle. 

Handling. When handling or working around batteries, safe practices should be followed: 

• Wear heavy-duty shoes and gloves in case a battery slips while being placed or moved, or electrolyte leaks or spills. 
• Wear a face shield or goggles to protect your eyes in the event of an explosion or acid spray.
• To prevent shorting, wrap electrical tape around the unused end of any tools used for removing, installing, and/or tightening battery terminal hardware.
• To prevent electrical shock or shorting, place an insulating cover, such as a small piece of plywood or other insulating material, over the tops of batteries adjacent to the one you’re working on.