Will a Battery Tender Junior charge a flat car battery?

[Stig / Major Tom]

My deceased FIL's battery in his Equinox is flat from sitting for months.
Will my Battery Tender Junior renew this battery if I connect it for a day or two?

Thanks.
Stig

[rjs987]

Not so sure any Battery Maintainer can charge up a battery from flat. That's usually a job for a trickle charger at least (while closely monitored) and the after a partial charge at least then the battery maintainer like a Battery Tender. There has to be a charge there to start with for a maintainer to know the state of charge and where in the program to start.

[Kansas kymco]

If the battery has sat dead for months it's toast.  I've ruined more then one motorcycle battery letting it completely discharge.  The plates in the battery sulfate up.

[scooterfan]

If a battery gets that flat it needs a quite powerful charger to restore the Voltage level again. Most cheaper chargers (in the country I came from) were not capable of rising Voltage from such low levels again.
If a battery’s Voltage level goes that low only a few times, it usually destroys the battery’s lifespan permanently.

[klaviator]

Hook it up and see what happens. 

[Stig / Major Tom]

Hook it up and see what happens.

That's my plan - just wanted to check I wasn't going to set off some codes.

Stig

[Ruffus]

@First normal strongest charger you have, then a trickle charger to desulfate, if plates not too much eaten up and shortcut.

[Kansas kymco]

That's my plan - just wanted to check I wasn't going to set off some codes.

Stig

If it's a automatic battery maintainer (mine flash a yellow fault light) . RJS is correct it has to have a voltage to know what to do.  Like I said I've got plenty of experience destroying a perfectly good motorcycle battery from neglect.

[Iahawk]

Stig, I haven't charged a fully dead battery with my Battery Tender JR..but i have topped off the battery in 2 different cars with it. On 2 lightly driven vehicles (one sat for a week or 3 between drives and the other is driven 1 or 2x per week) it would usually take 24 hours (or more) to get back to full charge (solid green light).

So don't expect anything to happen quickly...probably need to give it at least a few days before you give up on it.

[randyo]

I have had to "jump start" my charger on a completely dead battery, hook up another battery with at least a partial charge to get the charging process going, then disconnect after a while, sometimes you can revive  a dead battery

[Stig / Major Tom]

Stig, I haven't charged a fully dead battery with my Battery Tender JR..but i have topped off the battery in 2 different cars with it. On 2 lightly driven vehicles (one sat for a week or 3 between drives and the other is driven 1 or 2x per week) it would usually take 24 hours (or more) to get back to full charge (solid green light).

So don't expect anything to happen quickly...probably need to give it at least a few days before you give up on it.

Yeah, will do
 Not wanting to change out the battery - apparently car will throw codes, lose its mind, or need a few 100 miles to sort itself if battery is disconnected.
Love simple new cars.....
Stig

[Kansas kymco]

Yeah, will do
 Not wanting to change out the battery - apparently car will throw codes, lose its mind, or need a few 100 miles to sort itself if battery is disconnected.
Love simple new cars.....
Stig

Stig if the battery is completely dead it makes no difference to change it out.  The computer will have to relearn anyway.  There are 3 major battery manufacturers in the US . Johnson Controls having 50% of the market the other two are Stryten  and  East Penn.  The Stryten plant in Salina (30 miles North of McPherson) is 46 acres in size and employees 850 people.  Jumping a completely dead battery from a fully charged battery can be dangerous.  The hot battery sees this as a dead short.  If you have measurable voltage on the discharged battery you should be able to recharge.

[Stig / Major Tom]

Stig if the battery is completely dead it makes no difference to change it out.  The computer will have to relearn anyway.  There are 3 major battery manufacturers in the US . Johnson Controls having 50% of the market the other two are Stryten  and  East Penn.  I suggest you go to there web site to ask questions. Jumping a completely dead battery from a fully charged battery can be dangerous.  The hot battery sees this as a dead short.  If you have measurable voltage on the discharged battery you should be able to recharge.

Thanks for the advice -
 BIL said he jumped it  successfully 3 weeks ago - so, will check tomorrow to see if my Tender Jr. did anything - and if not will test with my little multimeter to see if there's any juice in the thing. It's a pretty nice car - don't want to mess it up. Will have it flat-bedded to dealership if necessary.

Stig

[Kansas kymco]

Thanks for the advice -
 BIL said he jumped it  successfully 3 weeks ago - so, will check tomorrow to see if my Tender Jr. did anything - and if not will test with my little multimeter to see if there's any juice in the thing. It's a pretty nice car - don't want to mess it up. Will have it flat-bedded to dealership if necessary.

Stig

I was under the impression it had sat dead for months.  If it was used three weeks ago you should have some voltage in it.  A 50% discharged car  battery can take up to 50 hours to recharge at 2 amps.

[Stig / Major Tom]

I was under the impression it had sat dead for months.  If it was used three weeks ago you should have some voltage in it.  A 50% discharged car  battery can take up to 50 hours to recharge at 2 amps.

I think it was used twice, maybe 3 times,  for short trips to Dr's over an 2 yr period.

Stig