tkm

Hey folks, apologies for adding to the extensive list of battery questions, but I thought I'd ask before doing the obvious and just buying a new battery.

Here are the details:
- 96 993
- out of town for a long trip and so left car w/ battery disconnected for 3 months
- now, whenever starting, takes two turns of the key to fire her up (other RLers have had similar issues, which usually means new battery time)
- measured volts using cig lighter volt meter (per RLer recommendations) and get 11.3v when key is turned to "on" but engine is not started (11.3 is really low, I know, though not definitely bad battery based on what the packaging on this volt meter says)
- take car to battery shop (again, per RLer recommendations) to confirm it's indeed bad battery. battery shop measures directly from battery and gets 12.4v (which I think is good but different than cig lighter reading), BUT cold crank amps measures 300 out of normal 700
- person at battery shop says could be that it just needs to be charged, but also likely that battery's just "done"

I'm probably dumb for thinking this may mean I don't need a new battery, but can someone confirm/deny based on what I've told you? Does that extremely low cold crank amps mean there's no chance of getting this battery back to normal? Is there something else that could be causing this?

Thanks for the guidance!

vincer77

Have you charged the battery with a battery charger? That would be the first step then have the battery load tested again as well as the car charging system.

Then I would replace the battery.

I have a CTEK trickle charger that claims to be able to resurrect a dead battery, but I have no experience with that. Alex should chime in soon, and seems to have a great deal of knowledge with batteries.

Best of luck.

il pirata

I would recommend buying a CTEK 7002 for the future first.

Great buy right now on Amazon

http://www.amazon.com/CTEK-Multi-700.../dp/B000FRLO9Y

The 7002 does have instructions for bringing a battery back...I have used older CTEK products to do this with good results. If it does not help at least in the future when the car sits you can keep the battery in great shape...I get one with the cigarette adapter kit which they call Comfort Connect Plug...on your car you just crack the window enough to get the cord through THEN connect the Comfort Connect Plug and plug into the cigarette plug...it's always hot.

ca993twin

Vince is correct, there is no point in testing a battery that isn't fully charged. You might also lift the caps and look for excessive sulphate from all the sitting around. Be sure its topped up with distilled water. I don't know about the restorative properties of the maintainers... but lead acid batteries do NOT like to go flat and require a deep charge.

NC TRACKRAT

As I recall, when a conventional lead-acid battery is discharged, the plates sulfate. When that happens, battery efficiency is reduced. The more times it's discharged, the more sulfating occurs. Charging the battery will not reverse the process. Over time, even though the battery is disconnected, a conventional battery will discharge. Keeping a good trickle-charger on a battery guards against discharge and sulfating.

linen grey ghost

An initial question: how old is the battery as of this date?

Silvertarga

IXLR8

Any battery test has to be done from a fully charged battery as has already mentioned. That means charged to 14.4V and maintained there for at least a few hours.

Four to eight hours after the charger has been disconnected, you should have a battery voltage of 12.65 to 12.90 V (battery not connected to vehicle). 12.4V is too low unless the battery is being loaded with lights, etc.

11.4V is a fully discharged battery and its a sure way to short battery life...depending how long its been in that state.

That 300 out of 700 amp test is incomplete....you need to know what the voltage was when it supplied that current and how long it could be maintained. Maybe it is OK in that if it can supply a 300A current, which is more than what your starter draws.

Charge it up and see how it performs. Use a maintainer next time.

IXLR8

Although a lot of battery charger/maintainer manufacturers would like to make you believe you can revive a sulfated battery. Possible (depending on the state of sulfation), but highly improbable.

Those who say they brought one back from the dead were simply dealing with a discharged battery, not one that is heavily sulfated.

An AGM or GEL has a far better chance of being revived. But they have their disadvantages. I say, keep it charged and it will last a long long time.


And quicker in a warm environment. It is best to leave a fully charged battery in a cool/cold garage or basement making sure to keep an eye on the state of charge.

il pirata

Well okay but I am not sure we have have enough information to determine if the battery is heavily sulfated. From system engineering point of view, he most likely needs a charger longer anyway, spend $100 and try to get his current battery back, does not work get a new one and move on.

It really is simple Alex.

IXLR8

Exactly what I said. I was replying to NC Trackrat with respect to sulfation and the misleading info from charger manufacturers.

tkm

As usual, great feedback here, folks (and a little overwhelming, too, given my utter lack of knowledge about batteries and general auto DIY maintenance).

Just to respond to some of the comments:
1. Alex, thank you for the detailed directions. Very helpful
2. LGG, not sure of the age. At least 3.5 years old b/c I bought the car that long ago and haven't done anything to the battery
3. NC and others, should've kept a charger on it while I was away, but have no access to power in the garage of the building I park in. Noted, though, and so next time I skip town for a while I'll try and find somewhere else to put it
4. CA993, showing further ignorance here, but I had no clue what you meant by filled up w/ distilled water (but now do: , thank you)
4. Il, thanks for the link. Looks like I'll be buying that b/c, as you said, I'll need it in the future anyway regardless of whether I can resuscitate the existing battery (ditto Vince for bringing that up in the first place); just will need to find a place to plug it in, of course

If I'm reading all this correctly, steps are:
1. Buy charger
2. Charge battery (per Alex's detailed instructions)
3. Check charge
4. If still where it's currently reading, need a new battery

Thanks folks! Rennlist continues to amaze me. I unfortunately don't (can't?) do much to contribute to the community, but hopefully just being a member does some small part.

IXLR8

If you maintain the battery and it never gets neglected (discharged for a given time), batteries will last a long time. I'm in my 14th year with the original battery in my daily driver, and it starts just fine at -10F.

bjornebo

Thank you for the heads up about the CTEK 7002. I went ahead and ordered one.