3-Stage Alternator Regulators

Vehicle starting batteries – usually flooded-cell lead-acid – are primarily designed to supply short bursts of energy to quickly and reliably start an engine and then promptly be fully recharged. Starting batteries aren’t designed to be deep-discharged and then recharged – like a deep-cycle house battery – so a vehicle alternator’s voltage regulator is typically set at a fixed target voltage of between 13.6V and 14.2V, which is fine for this type of narrow application.

However, this voltage range is typically not high enough to fully recharge deep-cycle batteries following normal or perhaps even extreme use, especially if they’re cold. So, what if you want to use your engine’s alternator to also fully charge deep-cycle house batteries – flooded-cell, AGM, or gel – especially if these batteries are very hot or very cold? A three-stage alternator regulator – a.k.a. a “smart regulator” – may be the answer.

Like a smart plug-in battery charger or a multi-stage solar battery charger, a smart regulator features multi-stage voltage outputs (bulk, absorption, float) that may be user-selectable for different battery types (flooded-cell, AGM, gel). Really sophisticated smart regulators may even offer plug-in remote temperature sensors that attach to the battery case to allow the regulator to optimize target voltages based on the battery’s actual temperature.

For applications where the engine alternator is a prime recharging source, this suite of features allows for deep-cycle house batteries to be correctly and fully charged, resulting in both superior performance (usable Ah) and battery longevity (cycles). This is a primarily a marine application, as it’s well suited to hybrid “marine” batteries that are used for both starting and house applications, but there’s also some interest in the RV community.

Several companies manufacture smart regulators and other smart-charging system components that can be retrofitted to certain existing alternators and systems.

Give us a call at 615-285-0663, and we’ll be happy to discuss these and other possible solutions your particular battery charging requirements. Or visit our website.


About the Author – Jim Goodnight – also known as “crewzer” — is a retired solar industry application engineer, product manager, and forum moderator and has previously written for Home Power and Solar Professional magazines.