Charging from the sun
Marine MPPT Solar Charge Controllers
A marine solar controller must match the panel array and the installed battery. Check PV voltage and current limits, battery-approved charge settings, temperature protection and BMS controls. Float settings are battery-specific; a lithium label alone is not proof of compatibility.
How to size an MPPT controller
- Controller amps must exceed array watts divided by battery nominal voltage, with headroom for a cold bright day.
- Check the maximum PV input voltage against your panels in series, not in parallel.
- Match absorption, float and temperature settings to the exact battery manual; disable equalisation where required.
- Bluetooth is worth it here: a controller you can read is a controller you will notice failing.
The full reasoning is in Lithium Battery Solar Controller Compatibility on Boats.
Sized for your boat
32 A
Charge current for a 400 Ah bank with 400 W of solar
Worked from the loads you have set in the calculator. Change the boat and this figure changes with it.
4 options fit — the first is the one we would fit
The options
Compare equipment ratings and applications
| Product | Charge current | Price band | Best suited to |
|---|---|---|---|
| Victron 30 A | 30 A | $220–$320 | Arrays up to about 400 W at 12 V. |
| Renogy 40 A | 40 A | $180–$280 | Solar-first refits on a budget. |
| Enerdrive 40 A | 40 A | $390–$540 | Certified marine installs with a 400–600 W array. |
| Victron 50 A | 50 A | $340–$470 | Arrays from 500 W to about 700 W at 12 V. |
| Victron 70 A | 70 A | $560–$780 | Arrays from 700 W to about 900 W at 12 V. |
Head to head
Asked most
What size MPPT do I need for 400 W of solar?
At 12 V nominal, 400 W divided by 12.8 V is about 31 A, so a 40 A controller with headroom. At 24 V the same array needs roughly half the controller current.
Will my existing solar controller work with lithium?
It may, if its configurable voltage, timing and protection settings meet the exact battery instructions. Check permitted float behaviour, disable inappropriate equalisation and confirm low-temperature protection.