I decided to test my battery at work today, because I have had the occassional traction control fail message briefly pop up upon starting the car, and it cranked a little slow this morning.

I drove thirty miles to work (rural driving at 60MPH) and shut the car off. 4 hours later I started the car and drove a mile down the road to the bank, where the car idled for 5 minutes, then 6 or seven miles of driving, followed by 2 minutes of idling. I then drove the six miles back to work, shutting the car off and restarting it when I stopped at the gas station halfway back. When I tested the battery an hour later, I got these readings:

Volts: 12.40 volts
Measured CCA: 791CCA (battery rated at 850CCA)

Starter test showed 11.16V on starting

Charging test showed 13.63V (idling in Park)

Question is, has the car been driven enough today for an accurate test? The car is driven everyday, usually 30 miles at a time.

Before I replace the battery, I want to be sure.

Also, does anyone have any experience with Deka batteries? We sell a 900CCA, OE fit, Deka battery (Part#49S) here. My cost on it is only $95.00, so I'd like to buy one if nobody has had a negative experience with the brand. The Deka batteries we have sold have been great for our customers, but other cars aren't as picky as Jaguars.

 

I would take the battery to an auto parts store and do a load test. They have a tester that applies a load to the battery and monitors its discharge. That will determine if you need a new battery or not a lot better.
I recommend checking the short positive terminal wire for corrosion also. I just replaced mine, it had corrosion down inside the cable cover. I tried cleaning it, that worked for a couple months, then it corroded again and decided it was time for a replacement. No more terminal corrosion now....yaayyyy.

 

chad, how old is the battery?....readings don't look that bad...cold cranking...holding up....i went through same issues this summer especially when using ac and not punching it out on the highway...go to auto zone they can run through for you....as you know these kitty s are high maintenance. i wound up getting a new battery...top of the line anywhere from 130-150 bucks but worth every penny!

 

The battery is 2 or 3 years old.

I actually work at an auto parts store, and we have a $600 top of the line battery tester, which I've been using. It performs load tests, shows CCA, checks starter cranking voltage, and charging system voltage. It even prints the results after the test.

I brought the tester home with me last night. I drove straight home, which is a 30 mile drive (pretty much nonstop, with only one stoplight and no stop signs). I tested the battery when I got home. Voltage was up to 12.89v, but CCA stayed at 791, which is less than the 850CCA the battery is rated.

I let the car sit overnight and tested again this morning. It was back down to 12.40 volts, with CCA staying around 790.

I'll disconnect the battery when I get home from work today, and test it tomorrow morning to see if the battery is discharging, or if there is some kind of a draw on it.

 

Your battery sounds just fine to me.

 

Chad, since you work in a parts store and do this all the time and I don't, when you test batteries for customers do you usually see the CCA actual rating that you get on your machine match the CCA rating on the battery?

I always wondered how accurate the CCA advertising on the battery is and just how long a battery can produce those numbers.

Just curious.

Stewart

p.s. I agree with the last poster, your battery seems fine.

 

From what I've read, these cars don't like anything less than 12.5 volts. My battery drops below that after sitting several hours. The 12.4 volts it is testing at is equal to 75% charge (or battery life, I forget which) according to the chart I stumbled on elsewhere on this forum.

I'll disconnect the battery when I get home today, and test it again tomorrow. If it stays at 12.80- 12.90 volts, than I'll know that there is a draw somewhere. I'll start by checking the cables and also the bulkhead connector. If the battery tests at 12.40 volts again, then I'll know that the battery is discharging, and I'll toss a new one in.

 

All admirable, but hang on a quick question - has the car been sitting for any amount of time, say over a few days to a week over the past few months? If so, try running the battery down with a 12V auto bulb over night, recharge and drain a couple of times and refit it.

I salvaged a 2 year old Varta (my experience with them? the Best for Jags) by doing the gym trick with it, the car sat for a couple of weeks and I got trac flashing on startup, the battery 'bench press' fixed it. Yours is marginal right now. Exercise it

 

There's some in truth in what you've read about static voltage, but this is only part of the story.

What drives our Jags nuts is voltage drop during cranking. A weak battery, bad grounds, wet connections, etc can cause sufficient drop in the system that it's similar to a power loss on a desktop computer.

I'd put the battery on charge, measure no-load voltage afterwards and see if it decays over the next few days. You might have a parasitic drain somewhere.

 

Don't sell Varta here, which is a shame. Had them as OEM on my LRs and they were super. The one in the RRSSC was perfect after five years.

 

Typically, we see some degredation of CCAs after a couple years, usually around 50 CCAs lost. I've seen some batteries lose 100 CCAs after 4 or 5 years, yet still pass the load test and be shown as good batteries.

If I was driving any other vehicle, I wouldn't think twice about the test results of my battery. But we all know how fussy Jags are when it comes to voltage. On cold mornings it is cranking slower than normal. I'm getting the occassional "traction control fail" message briefly pop up during starting of the engine. The windows seem to be operating slower than they used to, and my CD changer is starting to act up (It sometimes doesn't recognize discs, and I have to eject the cartridge and reinsert it. Then it works fine.)

The batteries we sell actually test higher the the rated CCA. For example, the 49 group size battery that my XJR requires is rated at 900 CCA, but tests over 1000 CCA. Another reason why I'm tempted to toss a battery in it.

 

Seems silly to ask, but all your cables and connections are good, clean, and tight, right?

 

The car did sit at the repair shop for two weeks, when the fuel pumps were being replaced. That was the end of this past August into the beginning of September. Other than that, I never have let it sit longer than a day or two. The car is driven 60 miles a day Monday through Saturday, and usually parked on Sunday. It did, however sit for several months before I bought it.

 

They all appear to be good in the battery compartment, at least, but I'll take a closer look after work.

 

A deep cycle run on that battery wouldn't hurt either.

 

Yes it would.

Automotive batteries don't like deep discharges at all.

 

Search for a "state of charge" voltage table. Lots around including on this site.

Then, fully charge the battery using a slow trickle charge.

Let it sit for an hour to drop the float charge.

Measure the voltage.

 

I don't see where you have tested the current draw after shutdown... It should be in the 25 mA range after about 25 minutes.

 

Yes your correct, but only if you do it multiple times. A single deep charge will either rejuvenate your older battery (usually from lack of use) or show the cells are probably toast.
If you have any swelling do not do a deep charge either, that alone is the sign the cells are giving up.

 

I'm still on the original battery with my 01XJR with 35,000 miles.
Battery is always on "life support" (cheap $6 Harbor Freight charger) when not using the car and I do check and add distilled water once or twice a year.