Trickle charger or maintainer: which one can stay on?
A basic trickle charger pushes a small, constant current whether the battery needs it or not, and can overcharge if you forget it. A smart maintainer charges, then switches to holding the battery full. The second is the one to leave connected.
Checked against sources on by the TrueAmps editorial team.
What each one does
Battery Tender, which sells both, puts it plainly. A trickle charger "delivers a low, constant current to your battery", and its drawback is the "risk of overcharging if left connected for too long". A smart charger uses "microprocessors to monitor and control the charging process" (Battery Tender).
The confusing part is the name. People search for "trickle charger" and mostly mean a small charger they can leave on a car in the garage. Many products sold under that label are smart chargers with a maintenance stage, including every model on this site. Check the product page for a maintenance or float mode before you leave one connected for weeks.
Chargers on this site rated to stay connected
| Charger | Amps | Recharges up to | Maintains |
|---|---|---|---|
| NOCO GENIUS1 | 1 | 30 Ah | All battery sizes, per NOCO |
| Battery Tender Junior Multi-Chemistry | 1 | not published | Float maintenance, per Battery Tender |
| NOCO GENIUS2 | 2 | 40 Ah | All battery sizes, per NOCO |
| NOCO GENIUS2D | 2 | 40 Ah | All battery sizes, per NOCO |
| NOCO GENIUS5 | 5 | 120 Ah | All battery sizes, per NOCO |
| NOCO GENIUS10 | 10 | 230 Ah | All battery sizes, per NOCO |
Picking one for storage
For a car or bike that sits over winter, the current barely matters: the maintainer only tops up what the battery loses. A 1 or 2 amp unit such as the GENIUS1 or Battery Tender Junior is enough for that job. If the battery also needs recharging from low first, size the charger to the battery with the charge-time calculator.
Questions people ask
Can I leave a trickle charger on all winter?
Battery Tender, which makes both kinds, lists "risk of overcharging if left connected for too long" as a drawback of a basic trickle charger. For months of storage, use a smart charger or maintainer that the maker rates for long-term connection.
Is a battery maintainer the same as a trickle charger?
No. Battery Tender describes a trickle charger as delivering "a low, constant current", while a smart charger uses a microprocessor to monitor and control charging. Many products sold as trickle chargers today are smart chargers.