Marine Battery Charger and Charging Systems
Batteries are only as good as the way they are charged. We install marine battery chargers, DC to DC chargers and split charge systems, and find out why boat batteries are not charging or keep draining, working at your berth from Brighton to Southampton.
A boat can have three or four charging sources: the engine alternator, a mains charger on shore power, solar and perhaps a generator. Each needs to suit the batteries fitted and to work with the others, rather than fighting over the bank.
Mains battery chargers
A marine battery charger runs from shore power or a generator and should have a charging profile for the battery type: lead-acid, AGM or LiFePO4. We fit it with protected AC and DC wiring, set it up and check it against the bank. Victron chargers and inverter-chargers are among the equipment we supply and install.
Victron installation · Marine inverter installation
Split charge relays and DC to DC chargers
A split charge relay simply joins the domestic bank to the engine battery when the alternator is running. It is cheap and simple, but it does not change the charging voltage. A DC to DC charger controls charging to the domestic bank, which suits lithium and long cable runs and protects the alternator. Which is right depends on the batteries and alternator fitted.
Boat batteries not charging
When batteries will not come up, we work through the charging path:
- Alternator output and its sensing and field connections
- Relay, DC to DC charger or isolator between banks
- Charger settings for the battery chemistry
- Fuses, isolators and voltage drop in cables
- Battery condition and capacity under test
Boat battery draining
A bank that goes flat when the boat is left usually has a standing load: a bilge pump cycling, an instrument left on, a radio memory, or a fault leaking current. We measure the draw and track it to its circuit rather than adding more charging to hide it.
Marine solar panel installation · Lithium battery upgrades
Making the charging sources work together
On a boat with an alternator, a mains charger, solar and perhaps a generator, each source should use settings that suit the bank, and none should overcharge it when the others are running. A battery monitor shows what is going in and out, which makes it far easier to judge whether the system keeps up with your use. With lithium, the battery management system may stop charging when the bank is full or cold, so chargers need to handle that gracefully and the alternator needs protecting. We set up each source, test them under load and explain what the display should show day to day.
Frequently asked questions
Do I need a DC to DC charger or a split charge relay?
A relay can suit a simple lead-acid setup. With lithium, or a long cable run, a DC to DC charger is usually the better choice. We assess the system first.
Can I keep my old charger if I change to lithium?
Only if it has a suitable LiFePO4 profile and settings. We check it against the batteries fitted.
Why do my boat batteries keep draining?
Usually a standing load or a leakage fault. Measuring the draw and isolating circuits finds it.
Do you fit split charge in campervans?
Yes, campervan split charge and DC to DC work is covered on our campervan lithium and split charge page.
Sort out your charging
Tell us the batteries, the chargers fitted and the symptoms, and we will arrange a visit and written quote.