We’re often asked if it’s possible to use a lead-acid starting battery alongside LiFePO4 house batteries, charging both from the same alternator. The answer is generally yes, but it requires some special considerations. Lead-acid (or AGM) and LiFePO4 batteries are different technologies with incompatible charging requirements, so they should never be combined directly. This means a battery combiner is not suitable. However, there are two viable options for charging both battery banks from a single alternator.
One effective solution is using a DC-DC charger, which allows the alternator to charge both battery types while keeping them electrically isolated. The Victron Orion DC-DC charger is an excellent choice for this purpose. It enables the starting battery to charge directly from the alternator, while providing a separate charging profile suited to the LiFePO4 house batteries. The benefits of this setup include:
- Independent charging for different battery types
- Multiple charging profiles tailored to each battery type
- Straightforward installation and monitoring
- Alternator protection
- Expandable: multiple Orion units can be connected in parallel for higher power charging
The Orion is available in both isolated and non-isolated models. The isolated version is suitable for applications where the battery banks do not share a common ground, such as some vehicle and marine setups. The non-isolated version is designed for systems with a common ground, which is typical in most marine installations, making it the appropriate choice for many boats.
Below is a wiring diagram for a single Orion DC-DC charger with two battery banks:
A battery isolator enables the charging of multiple battery banks while keeping them isolated from each other. The Victron ARGO FET Battery Isolator enables the charging of three battery banks. The disadvantage of this approach is that there is a single charging profile applied to all three battery banks. Thus, if the start battery has a significantly different charging profile from the LiFePO4 battery bank, this may not be a good option.
Advantage – multiple batteries can be charged independently.
Disadvantage – only one battery charging profile.
