Kärcher OC 3 Foldable 7.4V 2000mAh Li-ion Battery

My OC 3 stopped mid-spray and now it won't turn on even after charging — what happened?

This is almost always a low-voltage lockout triggered by the battery dropping below the protection circuit's cutoff threshold during use, and it won't recover with a normal charge cycle. The built-in BMS has disconnected the cells to prevent damage, and some chargers won't initiate a charge when they see a voltage this low. Put the unit on charge for at least 30 minutes before pressing power — some protection circuits need a trickle period before the charger handshake completes. If the LED display still shows nothing after a full charge attempt, check the battery terminals for corrosion or debris causing a dropped connection.

The LED on my OC 3 shows full charge but the pump pressure drops off almost immediately — is that the battery or the pump?

At 7.4V nominal, a battery that reads "full" on the indicator but sags hard under pump load is showing classic capacity fade from repeated shallow cycles — the display reads resting voltage, not what the cells can actually deliver under draw. A healthy 2000mAh li-ion pack at this voltage holds steady through a full wash cycle; if pressure falls off within the first minute, the cells are no longer holding their rated capacity. This often happens when the unit has been stored with a depleted battery or left on the charger continuously for extended periods. Test by running the unit immediately after a fresh charge — if pressure drops within the first burst, the battery is the problem, not the pump.

My OC 3 sat in the garage all winter and now the charger just blinks without fully charging it — what's going on?

Li-ion cells that sit discharged for months will self-discharge below the threshold where a standard charger will engage, and the blinking typically means the charger is detecting a voltage too low to begin a normal charge cycle safely. We've seen this voltage land below 6V on similar 7.4V two-cell packs after a full winter of storage, which is deep enough that the protection circuit treats it as a fault. Some chargers have a recovery or "wake-up" mode that applies a small pre-charge current — check whether your charger supports this by holding the charge button for 5 seconds if it has one. If the charger continues blinking after 20 minutes without transitioning to a solid charge light, the cells have likely degraded past recovery and the battery needs replacement.