Car alarm goes off when charging timer starts

[justint]

I have a 2011 leaf, and frequently the car alarm goes when the charging timer starts. It doesn't happen everytime and so was replicated at the dealership, and they therefore said they couldn't fix it. Has anyone else had this problem. When it happens, i can deactivate the alarm with the fob but because i charge overnight it is very annoying and is annoying my neighbours. Thanks

[LeftieBiker]

I composed a longish post, and a site error ate it. Short version: check the rest voltage (car off for 30 minutes, doors closed, hood open) of the 12 volt battery. If that is dying then the voltage drop when charging starts may be triggering a sensor in the alarm that warns if the power is cut. If it's below 12.3 volts, recharge the 12 volt battery externally. If the battery is 4+ years old, replace it, and charge the new one fully before installation. Good luck.

[GerryAZ]

Is it the factory alarm that just flashes the lights and beeps the horn or a more elaborate aftermarket system? The factory alarm will activate when the 12V battery voltage recovers after dropping below a low-voltage threshold so it could be triggered when charging starts and the DC-DC converter starts charging the 12V battery (if 12V battery is weak). Aftermarket systems could be sensitive to electrical transients caused by the main contactor closing and charging current ramping up if their sensors, wiring, and control modules are not properly shielded.

[LeftieBiker]

If it is, as Gerry suggests, an overly-sensitive alarm (and you can't adjust the sensitivity) then an AGM or "marine" type 12 volt battery might solve the problem. Or, conversely, a starting type battery with a higher CCA rating than the OEM might experience less of a voltage drop when the contactors close. In any event, the battery size/configuration is 51R.