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If you are going to charge the battery do it with a charger as the alternator was designed to maintain a batterys charge and not actually charge a dead battery, charging a dead battery with the alternator puts a heavy load on the alternator and you could end up needing a new alternator as well as a new battery.
Even if there are no parasitic losses the battery will lose charge over time and will have to be recharged. Automotive batteries cannot take many deep discharges and recharges and will fail. If the vehicle is not used for extended periods the only option is to keep it connected to a trickle charger.
Even if there are no parasitic losses the battery will lose charge over time and will have to be recharged. Automotive batteries cannot take many deep discharges and recharges and will fail. If the vehicle is not used for extended periods the only option is to keep it connected to a trickle charger.
Yeah.. I burned through 2 batteries due to a small parasitic draw. It would take about 2.5 days to discharge the battery, but.. Constantly being discharged and recharged, after about 6 months, the batteries would get where it only took overnight to discharge them.
If it discharges and freezes - it is dead. A charged battery can sit through -20 or below, but if it loses the charge even 30 degrees will kill it forever. I do not know why.
We charged it overnight, and the car started. My housemate was sure it would need to be replaced (information she got on some website), but I suggested that we stop by a local mechanic we use and have him check it before heading off for a new one. He tested it, and it is fine, we just need to use that vehicle more often to keep it charged. Thanks to all who replied! Confirms what I have always thought to be true: don't believe everything you read, and always get a second opinion.
You do not need to start it regularly if you have a trickle charger (aka battery maintainer). You can pick them up for next to nothing at Harbor Freight when they have a sale. If you cannot run an extension cord out to the car, you can buy solar powered ones, but they may get stolen and will flag your car as one that is left sitting for long periods of time (same is true for an extension cord).
When you get a new battery, it might not be fully charged. Some shops will tell you to "just drive it," not understanding that some of us might let vehicles sit a week between driving. A short drive won't necessarily bring it up to full charge.
After I bought my present battery, I put it on a battery tender just in case because the drive home was short. In winter, I keep it on the tender unless I have just driven it and know I will drive it again in a few days. In summer I drive often and far enough there is no need for that.
Make sure your charger is appropriate for the type of battery.
The title pretty much says it all. New battery, car not driven for months. It needed to be jumped, but the battery did not stay charged. However, the car was driven only long enough to move it. Will actually driving it around help, or does it just need a new battery?
Driving it around will probably help. If someone took it on a 30-45 minute drive the battery would probably be fine for the foreseeable future.
If you are going to charge the battery do it with a charger as the alternator was designed to maintain a batterys charge and not actually charge a dead battery, charging a dead battery with the alternator puts a heavy load on the alternator and you could end up needing a new alternator as well as a new battery.
NOPE.
The alternator is "designed" to produce X amps at the rated voltage, typically around 14.2 volts for a 12 volt battery system.
The alternator will not work any harder on the load of a low/discharged battery than it would to supply power for other loads of the vehicle.
At that, few automotive batteries will "demand" much more than a 20 amp charge rate once they've received an initial surface charge at 13.8 - 14.2 volts. That surface charge demand is usually satisfied in the first couple of minutes of charging and the internal resistance of the battery goes up.
In days when cars were equipped with an ammeter, you'd see this characteristic displayed on the dash. After a couple minutes of an initial higher charge rate, the charging rate would drop to a much lower rate ... even on a car that had to be jump started with a low/discharged battery.
The only way commercial shop battery chargers can charge auto batteries at a faster rate is by doing so at a much higher voltage than the automotive alternator/regulator system is designed to do. The trade-off for a "quick charge" is much more heat produced in the battery during the charging process. If the battery gets too hot, it can be damaged. Far better to select lower amp charging rates to protect the battery ... at the cost of a longer charging session.
FWIW, in my shop we typically don't charge automotive batteries at over 20 amp rates and prefer 10 amp rates overnight.
As far as "sulfating" damage goes for a lead-acid battery from lack of use or from normal service, there are a lot of "maintainer" type chargers that use reverse-cycle high frequency charging cycles to break this layer up to extend the service life of a battery. I've had stand-by lead acid batteries (such as used for my emergency generators) last for over 20 years by using these "trickle maintainer" chargers. At some remote sites where these generators are located ... such as a friends' cabin at a lake in MN or a remote line shack in WY ... these generators aren't run but a few minutes to verify they're OK once every summer. Power for the maintainer/charger comes from a couple of solar cells so these units are completely off-grid independent, ready for service should the line power not be available.
My wife and I snowbird, Cape Cod to AZ, five months on the Cape, seven in AZ. We own four autos. Before leaving either location, among other preparations, I put two Deltran “smart chargers” (Battery Tender. These won’t overcharge a car battery.) on the batteries of both cars at the location where we are departing.
When we return to that location, the cars start up as if they had been started the day before. Do replace your batteries about every five years if you expect absolute reliability and no “surprises” when you try and start a car which has sat for an extended period of time, charger or no.
Rich
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