Batteries & Multiple Parallel Strings

A customer asked me about the number of parallel strings that can be used in a battery back up system, so I thought I would address this in today's blog.

Battery failures in a battery bank are rarely the fault of the batteries themselves. It usually has to do with how they are maintained, connected, and if they are sized correctly for your particular system. A good rule of thumb to follow is to keep the battery bank as simple as possible and limit to a single series of cells. Limit the number of strings of batteries to 3 or 4. The more strings you have, the harder it is to equalize the batteries.

When wiring batteries in series-parallel, you want to keep all the batteries at an equal state of charge. Batteries that receive less charge than others are more likely to fail prematurely taking years off your battery life. Any additional resistance added to a string can reduce the life of the entire string. So to minimize resistence keep the same wire size and wire lengths the same throughout the battery bank to help distribute current evenly throughout.

If battereis are not charged properly it will affect the life of the battery. If batteries are discharged too far, its harder to bring those batteries back up to full charge again due to build up of sulfation (crystals formed on battery plates during the discharge cycle of a battery). If the crystals are not broken down all the way during the re-charging cycles the crystals will eventually become sort of like cement, preventing the battery from charging to 100%, thus affecting the life of the battery.