A modern 12V car battery is going to take a long time to fully charge at 6Amps. The car's alternator(or generator depending on how "classic" the car is ) probably puts out around 30 Amps. Newer car charging systems are much higher - 60 Amps or more.

You can safely charge that battery at 20 Amps.

For fully discharged batteries, the following table lists the recommended battery charging rates and times:

80 Minutes or less [32 ampere hours or less]

15 Hours @ 3 amps

5 Hours @ 10 amps

80 to 125 Minutes [32 to 50 ampere hours]

21 Hours @ 4 amps

7.5 Hours @ 10 amps


125 to 170 Minutes [50 to 68 ampere hours]

22 Hours @ 5 amps

10 Hours @ 10 amps

170 to 250 Minutes [68 to 100 ampere hours]

23 Hours @ 6 amps

7.5 Hours @ 20 amps


Above 250 Minutes [over 100 ampere hours]

24 Hours @ 10 amps

6 Hours @ 40 amps

OK JOG, the car is a 69 AMX, 390,bored out,Dark Blue, edlebrock 4 barrel,Really clean.It has around 80k mi  on it,and its beautiful. He enters it in alot of shows,and has a room full of trophy's.Thanks all you guys for your answers,it's really Helpful. Where does it tell you how many amp hours a battery is?

Here's a little blurb from Optima about reserve capacity and CCA.

The Battery Council International (BCI) has created a group of standardized specifications that help give consumers an apples to apples comparison from one product to the next. Cold cranking amps is one of those specifications, as is Reserve Capacity. So what is Reserve Capacity? It is a time measurement that explains how long a fully-charged battery can deliver 25 amps of current in an 80°F-environment, before the battery is discharged down to 10.5 volts. - See more at: http://www.optimabatteries.com/en-us/experience/power-source/battery-reserve-...


Thus, reserve capacity can be roughly calculated into amp-hours if you really want to.  take the minutes of reserve capacity, multiply by 25 (amps) then divide by 60(minutes in an hour) to get amp-hours.  This will get you somewhere close.  There are other variables in there too regarding the way the battery is made internally, how well it handles slow discharge (if you're really discharging at 1 amp), lots of chemical reaction stuff that I don't even pretend to understand.

Note that down to 10.5v is DEAD.  A starting type battery will not tolerate this type of use for more than a few cycles before it begins to rapidly deteriorate. They are designed to provide a blast of current quickly and then be quickly recharged.

Most of the renewable energy folks say never take a battery below 60% if you want it to last and they prefer never below 80%.  They've had years of playing with batteries to figure it out.  And, they are using expensive deep discharge batteries.

If the car is going to be sitting, self-discharge will have the battery pretty well dead in a month.  Use a battery tender or put on a 2 amp charge for a day every other week to keep the battery up.

I know that the AMX is the performance model but my Mom had a 69 Javelin, it was a cool car  

ToesNose wrote on 12/19/14 at 04:39:26:

AMX was actually more than just a 'performance model' as the chassis was modified to make a 2 seat 'sports car' on a shortened wheelbase, though the Javelin was the car they started with to do that
There was also a 'hopped up' performance model of the 4 seat Javelin, called the 'SST'

Thanks for all the useful info.Turns out the battery charged up good, and the car fired up,no problem.My friend is looking into a battery tender.Thanks again.