Knowing what you have
Boat Battery Monitors and Shunts
On lead-acid you could read state of charge off the voltage and be roughly right. Lithium holds its voltage almost flat from 90% down to 20%, so voltage tells you nothing until it is telling you something urgent. A shunt-based monitor counts the amps in and out. Without one you are not managing a bank, you are hoping.
How to size a battery monitor
- The shunt goes on the negative, between the bank and everything else — every load and every charge source.
- Rate the shunt above your largest possible current, which is usually the inverter, not the windlass.
- Bluetooth or a panel display: pick the one you will actually look at.
- Calibrate it at install and again after the first full charge, or the state of charge drifts.
The full reasoning is in Boat Battery Shunt Placement: Wiring and Bypass Errors.
The options
Compare equipment ratings and applications
| Product | Shunt rating | Price band | Best suited to |
|---|---|---|---|
| Victron SmartShunt 500 A | 500 A | $180–$260 | Any boat where you would rather read the bank on a phone than on a bulkhead. |
| Victron BMV 712 500 A | 500 A | $250–$340 | Helm or nav-station mounting where a glance matters. |
| Enerdrive eLite 500 A | 500 A | $280–$390 | Certified installs already specified around Enerdrive. |
| Renogy shunt 500 A | 500 A | $110–$180 | Budget refits where the alternative is no monitor at all. |
Head to head
Asked most
Where does the shunt go?
On the negative, between the bank and everything else. If any load or charge source connects to the battery on the shunt's battery side, that current is invisible and every reading is wrong.
Do I need a monitor if my battery has Bluetooth?
The battery's own BMS reports what it sees at the terminals, which is better than nothing. A shunt sees the whole DC system, including a second bank and every charge source. On a cruising boat, fit the shunt.