When you are plugged into a campsite pillar, a marina berth or a garage socket, the job is different from alternator charging: the supply is abundant, the voltage is fixed, and you can size the charger for the battery rather than for what the engine can spare.
Universal input
The mains chargers in this shop accept a documented 90–265 V AC input, which covers both 230 V European supplies and 110–120 V supplies in North America and parts of the Caribbean. That matters if the vehicle or boat travels.
What a mains lithium charger does
An AC-DC lithium charger converts mains alternating current into a controlled charging output for the battery. It performs the same role as the alternator-side DC-DC charger, but from a fixed, high-voltage source. That gives it three advantages:
- Power is not limited by the alternator, so a higher charge current is possible.
- The input voltage does not move, so the charger can be simpler and hold its output more precisely.
- It can run for hours without the engine idling, which is how you actually want to charge on a site.
Note the difference from a DC-DC charger: a mains charger will typically also be able to hold a float or storage voltage once the bank is full, and it may let you charge while DC loads are running. Check each model’s documented behaviour for what it does at the end of a charge.
Match the charge voltage to the bank
As with any lithium charging, the voltage must follow the battery manufacturer’s specification. The documented outputs in this catalogue map to bank sizes like this:
| Bank | Cells in series | Documented charge voltage |
|---|---|---|
| 12 V nominal | 4S | 14.6 V |
| 24 V nominal | 8S | 29.2 V |
| 36 V nominal | 12S | 43.8 V |
| 48 V nominal | 16S | 58.4 V |
A model with several documented output voltages covers multiple bank sizes; a fixed-output model is simpler and often cheaper if you only ever charge one bank. Choose deliberately: the wrong output voltage is not adjustable after the fact on a fixed model.
Sizing the charger — and the socket
Charge current should sit within what the battery accepts. A bigger charger than the battery can absorb wastes money and may simply be refused by the BMS.
The second limit is the supply. A 68 A charger at 12 V is delivering roughly 1,000 W, and it draws at least that much from the mains:
| Supply | Approximate current |
|---|---|
| 230 V AC | about 4.4 A |
| 110 V AC | about 9.1 A |
Add something for conversion losses and for the surge at switch-on, and allow headroom on the circuit. A 6 A campsite pillar shared with a kettle, a water heater or a hair dryer will not be happy, and a 10 A lead running 30 m to the pitch will drop enough voltage to raise the current further. Plan the charger around the supply you actually have, not the one on a good day.
Generators
A charger is a continuous load for hours, not a brief surge like a power tool. Size a generator for the sustained load plus losses, and check its continuous rating rather than its peak rating. Some small inverter generators will accept a 1,000 W charger but will be running near their limit the whole time.
Mains charging in practice
AC-DC lithium chargers
AC–DC battery chargers
90–265V to 14.6–58.4V AC-DC Battery Charger, 5–68A
The multi-voltage model covers 14.6 V through 58.4 V, which suits an installation that might charge a 12 V bank on one trip and a 48 V bank on another. The fixed 14.6 V model is the straightforward choice for a single 12 V system.
Combining mains and alternator charging
Many installations have both, and they do not conflict as long as each charger is sized for its own source and both are configured for the same battery specification. The requirements are the same on both sides: the correct charge voltage, a current the battery accepts, fusing at the battery end, and sensible cable sizing.
If you have not yet sorted out the alternator side, read the guide to alternator charging first — it covers the smart-alternator problem and how to size the charge current against what the vehicle can spare.
Installation checklist
- Confirm the battery’s specified charge voltage and maximum charge current from its datasheet.
- Pick the model with that documented output voltage and a current within the battery’s limit.
- Check the supply: breaker size, lead length and what else is running on the same circuit.
- Fuse at the battery end and keep the DC cable short and thick.
- Mount the charger with room for air movement — it is a mains-powered unit running for hours, so it will get warm.
- Test with a partly discharged battery and measure the actual charge current before trusting the nominal figure.
Frequently asked questions
Can I leave the charger connected permanently?+
It depends on what the model does once the battery is full. Check the documented behaviour on the product page. If it holds a storage or float voltage appropriate for your battery, permanent connection is normal practice; if not, disconnect when the charge completes.
Will a 110 V supply work?+
The documented input range of 90–265 V AC covers both 110–120 V and 230 V supplies, so the same unit works in both. Remember that the mains current is roughly double at 110 V, which matters for extension leads and breakers.
Can I charge two banks at once?+
Not from a single-output charger, and not by connecting two different banks together. If you need to maintain a start battery as well as a house bank, use a separate device intended for that job and confirm how it isolates the two.
Is a mains charger better than an inverter running a charger?+
They are different situations. On shore power there is no reason to involve an inverter. Running a charger from your own inverter would mean DC to AC and back to DC, losing energy at every step.
Does charge current fall as the battery fills?+
Yes, in the constant-voltage phase the battery accepts progressively less current. That is normal. The charger’s nominal current is the maximum it will deliver, not a rate it holds until full.
Mains current figures above are arithmetic examples based on a 1,000 W output, before conversion losses and switch-on surge. Charge voltages and current ratings are supplier-stated for the exact models and are not independently tested by PVShop. Follow your battery manufacturer’s charging specification.