Which OPTIMA Battery is Best for My Trailer?

In this edition of the OPTIMA mailbox, Stan M. asks, "I have a small pull behind trailer with ac and 10amp charging when hooked to a vehicle. Which series is best when the battery discharges for three days slowly below serviceable limits and is then charged 12 hours while attached to the car, the REDTOP, YELLOWTOP or BLUETOP?"

Stan,

We recommend YELLOWTOPs or BLUETOPs (except the 34M) for any application that might involve deep-cycling. However, the question you need to answer is whether your vehicle's charging system is robust enough to handle maintaining the battery in your vehicle and potentially recharging a deeply-discharged battery in your trailer. Most vehicle charging systems are designed to maintain the batteries that came in the vehicles, not recharge auxiliary batteries on attached trailers.

We have run tests with an alternator manufacturer, using a stock alternator and a deeply-discharged battery on a vehicle that needed to be jump-started. The elevated temperatures and alternator output we observed were not conducive to long-term viability for either the alternator or the battery. If your charging system is up to the task, then an appropriately-sized YELLOWTOP or BLUETOP (except the 34M) would be suitable. 

We would also encourage you to research how much electrical demand will be placed on your trailer battery relative to the capacity of the battery (look for the Ah specification). Peurket's Law indicates the more deeply you discharge a lead-acid battery, the fewer cycles you will get out of it. For that reason, if you routinely deeply-discharge the battery on your trailer, your best option for a trailer battery might be the largest battery with the most reserve capacity that you can fit in your trailer.