AudenHoggart Posted July 8, 2019 Report Share Posted July 8, 2019 We'll be away for 4 weeks in August. Should I disconnect the battery? (presumably by just disconnecting the negative lead.) In case it's relevant, this is a 2013 C-Max SE with only 65K miles on it. It's kept in a carport in Portland Maine. Thanks! Quote Link to comment Share on other sites More sharing options...
Zathrus Posted July 9, 2019 Report Share Posted July 9, 2019 Instead of disconnecting battery, recommend connecting battery charger that also goes into float mode (acts as battery maintainer): https://www.amazon.com/Mroinge-maintainer-Automotive-Motorcycle-powersport/dp/B0716HN1Y4/ref=sr_1_23?crid=3RHKVHCCDXUYJ&keywords=battery%2Btender&qid=1562635252&s=gateway&sprefix=battery%2Bte%2Caps%2C155&sr=8-23&th=1 bigqueue 1 Quote Link to comment Share on other sites More sharing options...
plus 3 golfer Posted July 9, 2019 Report Share Posted July 9, 2019 (edited) A battery charger / maintainer is the best option as noted in above post. But since it's outdoors and you may not want to put a battery charger / maintainer on it, fully charge the battery with a battery charger (can take 16 hours or so) just before disconnecting negative cable from the ground stud in hatch area. Put tape around cable terminal so it doesn't touch ground. If battery is in "good" condition, it should start up on return. However, if battery is older, its storage capacity will have diminished since new and self discharge while disconnected could yield a no start condition upon return. How old is your battery? If it has been replaced, did dealer do it and reset the Battery Monitoring System (age)? The reason is a fully charged newer battery should be able to start car even if left connected at 30+ days assuming a 20 mA average parasitic drain would be around 40%. snowstorm says - "With car OFF, opening/shutting the door sends the current to about 8 amps. After a minute or so it steps its way down to about 0.4 amps. Then after maybe 30 minutes or more it finally drops to under 0.01 amps)." However, if battery was replaced and dealer did not reset age, your battery State of Charge (available capacity) may be low. The vehicle charging algorithm will use its computed lower SOC and not charge a new battery to the higher appropriate charge level. So, if you don't know, then you should at minimum charge battery with charger whether leaving connected or disconnected. Can you measure your battery voltage to see what it is? If should be around 12.6 - 12.7 Volts for a newer battery (and age reset). If it's 12.4 or lower (I've seen 12.2 Volts prior to battery reset with the BMS showing single digit SOC). either battery is old (has lost capacity) or charging algorithm was not reset and is using its computed lost capacity from last reset. Edited July 9, 2019 by Plus 3 Golfer Quote Link to comment Share on other sites More sharing options...
Billyk24 Posted February 11, 2020 Report Share Posted February 11, 2020 second the thought for a trickle charger Quote Link to comment Share on other sites More sharing options...
bigqueue Posted February 11, 2020 Report Share Posted February 11, 2020 (edited) I agree with the float charger....I am sure many will work just fine, but I have had great luck with the original Battery Tender: https://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITK8S/ref=sr_1_4?keywords=battery%2Btender&qid=1581406906&sr=8-4 Edited February 11, 2020 by bigqueue Add photo Quote Link to comment Share on other sites More sharing options...
bigqueue Posted February 11, 2020 Report Share Posted February 11, 2020 (edited) .. Edited February 11, 2020 by bigqueue Quote Link to comment Share on other sites More sharing options...
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