Battery Tender and dead battery

January 29, 2019, 11:10 AM

quote:
Originally posted by a1abdj:
This is one of the reasons that I like the old school chargers. Doesn't matter what condition the battery is in, it will run a charge to it. Today's smart chargers don't like to do that.

What I have done is taken another battery, run a set of jumper cables to it, and then hook the charger up to the dead battery to get it to run. On occasion it will catch on that you're attempting to trick it and shut off, so you may need to restart it a few times.

Exactly I have an old school or dumb charger hooked up to my Motorhome chassis batteries now. They were dead at 11.7 volts. The smart chargers work wonders on a low battery or keeping a battery up. But a dead battery their circuitry making sure you have the battery hooked up correctly o the charger shuts it down on a dead battery. Hooking a good battery to the dead battery should trick the charger into charging.

January 29, 2019, 04:44 PM

hrcjon

Discharged batteries are not an issue for actual battery tender brand. the cutoff is 3v. there will not be an issue at 11.7v. A battery that is less then 3v is likely really dead both figuratively and literally. But sometimes you never know and then you can trick these chargers into trying or use an old one or jump it or ....

January 29, 2019, 07:35 PM

Mark in Michigan

So I had a similar issue to the OP in late fall on my Vette, but the car had not been driven much at all this past year. Hooked up the Battery tender, but it just flashed red.

Broke out the old-school battery charger, but no joy! It would not send any current through the battery.

So I bought a new battery, installed it and started the Vette. Drove it a little bit, then put it in the garage and hooked the Battery Tender up to the new battery for winter storage.

January 29, 2019, 08:16 PM

Edmond

CTEK for the win. This is what I have:

https://smartercharger.com/col...s/ctek-multi-us-3300

January 29, 2019, 09:44 PM

bubbatime

Read the manual. Sometimes the charger will have an over ride feature so that you can charge up dead batteries that have only a few volts left. You can also hook up a good battery using jumper cables, then hook up the charger. The charger will charge both batteries at the same time. Once the dead battery has some voltage in it, disconnect the jumper cable to the good battery.

And, of course, a battery tender is going to take 24 hours to charge a battery.

January 29, 2019, 10:12 PM

Neel

The battery tender plus which I use is flashing red while it's either plugged in, or charging the battery.

When the battery is fully charged then it goes green.

For a battery which is very low, keep in mind a battery tender only puts out 1/2 amp while it's working so it will take a while.

January 29, 2019, 10:30 PM

jimmy123x

quote:
Originally posted by Neel:
The battery tender plus which I use is flashing red while it's either plugged in, or charging the battery.

When the battery is fully charged then it goes green.

For a battery which is very low, keep in mind a battery tender only puts out 1/2 amp while it's working so it will take a while.

Yeah like 10-20 days on a completely dead battery.