Battery Chargers & Maintainers

Selecting the proper charger will depend on what you are trying to accomplish. Deep cycle applications typically have a charger with an amp rating approximately 10-20% of the battery pack's AH rating.

For those trying to keep a starting battery fully charged when not in use, you generally don’t need a high amp battery charger. Instead, you can aim for a charger around 5-10% of the battery’s AH rating. Just remember, going too small can cause excess wear and tear on the charger and may even result in the charger faulting out.

While it might be possible, our answer is no for several reasons. Consider that a large battery in a car is approximately 100 AH, so a large battery pack of five or more batteries could be greater than 500 AH. Most batteries will lose 3 to 5% of their charge a month when brand-new and not hooked up. So, it's fair to assume they may lose double that when hooked up and not being used.

We have seen many people try to use a small charger or maintainer such as the Battery Tender Plus that only outputs 1.25 amps. Considering that 10% of 500 AH is 50 amps, the Battery Tender Plus would have to be in charge mode for 40 hours to make up for the natural discharge. The charger could be on even longer if the battery pack has a parasitic draw.

Ideally, you want a charger that doesn’t have to work that long to maintain a battery pack. We typically recommend selecting a charger with an amp rating that falls between 10% to 20% of the battery pack's AH rating, so for a 500 AH battery, a 50 amp charger would be ideal. While a small charger may work for some time, it could fault out from being in charge mode too long or fail prematurely from overuse.

In our 12v 500 AH battery pack scenario, we recommend the IOTA 55 Amp Converter Charger Power-Supply. A Charger Converter / Power-Supply is perfect for high amperage battery packs. They have demand sensing technology to actively make up for loads applied to the battery pack without taking the charger through another charge cycle. Their ability to supplement the amperage instead of always going into charge mode whenever the battery is in use makes them ideal for large battery packs.