Charging car battery?

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Jul 18, 2017
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Do you know what test/tests he did? If you drove to him and he simply tested with a volt meter when you arrived it doesn't prove anything. I have a car battery in my garage that I know to be failing but it's been sat at 12.7 v for almost a month (off charge).
Your battery needs to be tested under load. I would expect a bespoke battery supplier to have the correct equipment to do this, but if not it can be done with a multimeter (ideally with min/max function). The procedure is to connect the meter across the battery terminals after it has stood for a few hours. The meter should read over 12.4 v on a good battery. Then start the car and measure the voltage across the battery as the starter motor turns the engine over. If it drops below 9v your battery is failing. If you're car starts within a second or two and the refresh rate of your meter is slow it can be difficult to see how much it drops, hence one with min/max is preferred.
Goes to show how ignorant I am on car issues. None of the testers measured the voltage drop whens tarting the car. There never has been an issue starting the car which is why I suspect the aux battery.
 
Mar 14, 2005
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Earlier this week two different battery places told me that the battery needed replacing. Today while in Malvern I thought I would pop into ETB. One of the first questions the fitter asked me before checking the battery was whether the car had one or two batteries. At least he seemed to know more than the tow previous fitters.

Anyway he went under the hood unlike the other two previous fitters and did the tests. He then showed me the results and the battery reading was 12.6v! I am guessing that the terminals under the hood are for the main 12v battery. He could not test the aux battery while it was connected and he was not allowed to disconnect it.

I am now of the opinion that it is the aux battery that may be faulty. Although I can disconnect the negative terminal, I cannot remove the strap holding it down in place as I do not have a long enough extension for my socket set plus the the only rachet I have is the torque wrench which is just that bit to long anyway. What is a 1/4 inch square drive or a 3/8 square drive when dealing with Rachets?
I have never come across any situation where two batteries specifically of different types needed to be connected in direct parallel for a system to work. Consequently I would be surprised if your;s are genuinely connected together in direct parallel.

However, IF they are connected in direct parallel, then attempting to do a battery condition test without disconnecting the batteries will not tell you anything conclusive about either battery.

Until you have established if the actual wiring situation your working totally blind. and quoing voltages means very little.

But if both batteries are only charging to 12.6V then that raises the question s the alternator actually producing the correct charging voltages?
 

JTQ

May 7, 2005
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If there were issues with the auxiliary battery, the first "hints" I would expect to be seeing is a reticence for the vehicle's stop start system to function correctly.
Not using stop start habitually , and I am guilty of that, hides those early signs.
Mine in a Disco 4 failed at about year 7, I discovered it on one of those rare times I decided to give the SS a birthday treat, and it soon became evident it was not interested in working anything as "early" as it once did, only becoming "live" after a long run.
I purchased the identical battery as LR had fitted, from Tayna at way cheaper than the dealers quoted [the storeman even told me to look anywhere else!].
Then my in village indy fitted it and coded it, for a favour free of charge plus keeping the old one. I had removed the cover and clamp before popping in, so the job took minutes, far shorter than our social chat did.
Stop start was immediately back working just as it ought, I still only bother with it when I come into town or roadwork delays where it does something constructively useful.
 
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Jul 18, 2017
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I have never come across any situation where two batteries specifically of different types needed to be connected in direct parallel for a system to work. Consequently I would be surprised if your;s are genuinely connected together in direct parallel.

However, IF they are connected in direct parallel, then attempting to do a battery condition test without disconnecting the batteries will not tell you anything conclusive about either battery.

Until you have established if the actual wiring situation your working totally blind. and quoing voltages means very little.

But if both batteries are only charging to 12.6V then that raises the question s the alternator actually producing the correct charging voltages?
Thanks for the helpful post as I am learning slowly. When I used the multimeter across both batteries yesterday, both batteries read exactly 12v? Due to answers in earlier posts I checked and cannot see if the two batteries are connected in any way.
 
Jul 18, 2017
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If there were issues with the auxiliary battery, the first "hints" I would expect to be seeing is a reticence for the vehicle's stop start system to function correctly.
Not using stop start habitually , and I am guilty of that, hides those early signs.
Mine in a Disco 4 failed at about year 7, I discovered it on one of those rare times I decided to give the SS a birthday treat, and it soon became evident it was not interested in working anything as "early" as it once did, only becoming "live" after a long run.
I purchased the identical battery as LR had fitted, from Tayna at way cheaper than the dealers quoted [the storeman even told me to look anywhere else!].
Then my in village indy fitted it and coded it, for a favour free of charge plus keeping the old one. I had removed the cover and clamp before popping in, so the job took minute, far shorter than our social chat did.
Stop start was immediately back working just as it ought, I still only bother with it when I come into town or roadwork delays where it does something constructively useful.
As a matter of habit I switch off the Stop Start system every time we use the vehicle. Tayna is about 400% cheaper than the dealer!
 

JTQ

May 7, 2005
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As a matter of habit I switch off the Stop Start system every time we use the vehicle. Tayna is about 400% cheaper than the dealer!
IMO, it is time you explored that avenue, to see if it does what it is primarily there to do, I very simply, non overly involved test to make, and very targeted in checking out that component..
 
Nov 11, 2009
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I do as JTQ and use SS in town or heavy traffic.. Not so meticulous with the manual Kia as I use Neutral , but the twin clutch auto one I was told keeping the engine running just on auto hold may not do the clutches any favours. True or not I don't know but erring on the side of caution. But the Jeep is a conventional torque convertor automatic.
 
Jul 18, 2017
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I do as JTQ and use SS in town or heavy traffic.. Not so meticulous with the manual Kia, but the twin clutch auto one I was told keeping the engine running just on auto hold may not do the clutches any favours. True or not I don't know but erring on the side of caution. But the Jeep is a conventional torque convertor automatic.
It may some strange, but we hardly ever use the Jeep in town as we live out of town. I think part of the problem is that since Aug 2022 we have not even done 10k miles. Sometimes the Jeep is not used for several or more days, but alarm is on draining one of the batteries.
 

JTQ

May 7, 2005
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I do as JTQ and use SS in town or heavy traffic.. Not so meticulous with the manual Kia as I use Neutral , but the twin clutch auto one I was told keeping the engine running just on auto hold may not do the clutches any favours. True or not I don't know but erring on the side of caution. But the Jeep is a conventional torque convertor automatic.
The TC auto ought to have "neutral" so even removing most of the pumping of the engine's power into the oil when stationary.,
 
Nov 11, 2009
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The TC auto ought to have "neutral" so even removing most of the pumping of the engine's power into the oil when stationary.,
Yes it does. But I just come to a halt and Autohold is applied, and if in SS the engine restarts very quickly without any hesitation. Also it is a dry clutch system..
 
Oct 19, 2023
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If there were issues with the auxiliary battery, the first "hints" I would expect to be seeing is a reticence for the vehicle's stop start system to function correctly.
This mirrors my recent experience. Stop start rarely worked for almost a year. Car started ok until the freezing weather when it started after cranking slowly for a few seconds. A full charge didn't help. New battery fitted, stop start working again (so now I have to keep turning it off :ROFLMAO: ).
The only other thing I noticed with the failing battery was that after a freezing night the infotainment system had to be switched on when I started the car the following morning, normally it would come on when the ignition was turned on.
 
Jun 6, 2006
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SWMBO 8 year Kia oem battery let us down at sub zero degs last week. 12.6 v on multimeter after smart charging. Now looking for a new battery. As it’s a start stop the recommended battery is nearly twice the price. Circa £250.

So I’m not surprised the Jeep is nearly £500.

You have mentioned a number of weird electrical issues. I guess the only way to establish causation is plugging into Jeep’s diagnostic kit at a Dealer. If it is the battery and it fixes the issues all well and good. But if it doesn’t you may end up throwing money at replacing both batteries when the problem is something else.
Very annoying but that’s the problem with all this hi tech stuff today.

I googled Jeep battery problems and this cropped up. It tells me the life expectancy of Jeep batteries is not as good as other makes.Not sure who made your original battery?

Or a good auto electrician should have the correct kit to plug in to diagnose, I know the guy I use has very comprehensive diagnostics tools, fairly much to dealer level.
 
Mar 14, 2005
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Thanks for the helpful post as I am learning slowly. When I used the multimeter across both batteries yesterday, both batteries read exactly 12v? Due to answers in earlier posts I checked and cannot see if the two batteries are connected in any way.
It can sometimes be difficult to "see" how a circuit is made up as wires disappear into all sorts of different conduits, and unless you have the circuit diagram or are prepared to trace the wiring (very carefully) there may be a hidden connection.

However as I have pointed out already I cannot see any logical reason why both batteries would be connected in direct parallel, mixing size and chemistries is normally a No No as its fraught with difficulties.

As both batteries are giving the same 12V reading, A LA battery at only 12V is essentially less than 50% charged so that does perhaps suggest a common cause that might be limiting the charging, which is why I mentioned the alternator - an item that has caught you out previously. It could also be the voltage regulation circuitry (which might be in the alternator or could be separate to it).
 
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However as I have pointed out already I cannot see any logical reason why both batteries would be connected in direct parallel, mixing size and chemistries is normally a No No as its fraught with difficulties.
I have to agree. Why would you have a 70 AH battery and a 20 AH battery connected in parallel? You might as well have a single 90 AH battery. Also, if one battery went bad it could drag the second down with it. From what I've read, mine has an auxillary battery to maintain power to certain 'critical' controls in the event of failure of the primary battery.

Having said all that, both batteries are charged from the same source as I only have one alternator. I suspect that there is some sort of diode circuit to prevent one battery from draining the other.
 
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Jul 18, 2017
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Finally got enough nerve to remove the negative on the aux battery and then measure voltage on both AGM batteries. The vehicle had been standing for nearly 24 hours.

Main battery exactly 12v and the aux battery 12.1v. I gather that both the batteries should be at least 12.6v and need replacing?

However as per the negative terminal on the right I have never seen a battery with this type of terminal as the terminal looks to be square with a screw type rod in it. I am not sure if that screw needs to be removed to be fitted to a new battery as the only other ones I can find seem to have a square terminal for 12v 14ah 200A AGM auxiliary battery.

Please advise. Thanks.

Aux battery.jpg
 
Jun 20, 2005
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A wild card!
You said Most times the Stop Start is switched off as even less drain on the battery.
So why not go for the cheapest Lead acid batteries and stuff AGM ?
I do use SS on both cars , in fact it’s never turned off. So for us AGMs are the only way forward
 
Nov 16, 2015
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Sorry to say this. As you do not know what you are really doing. Don't mess about with it. Take it to a dealer or to an vehicle electrics , tech.
Àlso as you don't know he difference between a 1/4 drive and a 3/8 drive wrench you might damage the terminals refitting them.
 
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JTQ

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Main battery exactly 12v and the aux battery 12.1v. I gather that both the batteries should be at least 12.6v and need replacing?
No necessarily, what you are seeing is only indicating neither is any where near fully charged.

Even batteries that are losing their ability to hold much charge, can still exhibit 12.7, 12.6 volts if they are nearing fully charged.
Note this is hold as much energy as they now can hold, which could be way different to holding what amount of energy, they might once have been capable of holding.[The true Ah capacity being indicative of a quantity of energy]

As you are being told, you need somebody competent to check the "health" of your batteries, plus the health of their charging systems; just taking voltage readings yield less than the required information to know what the extent of your problems are.

Edit: IMO you are more likely to find "competence" in this area with a well respected auto electrician, than in many car brand dealerships! That's the area they work in, not just one facet of a much wider range of issues.
 
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Jun 16, 2020
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Finally got enough nerve to remove the negative on the aux battery and then measure voltage on both AGM batteries. The vehicle had been standing for nearly 24 hours.

Main battery exactly 12v and the aux battery 12.1v. I gather that both the batteries should be at least 12.6v and need replacing?

However as per the negative terminal on the right I have never seen a battery with this type of terminal as the terminal looks to be square with a screw type rod in it. I am not sure if that screw needs to be removed to be fitted to a new battery as the only other ones I can find seem to have a square terminal for 12v 14ah 200A AGM auxiliary battery.

Please advise. Thanks.

View attachment 6226
I would look at the numbers on both batteries, go online and price new ones. Then replace, taking the seat out is probably the hard part. And it looks like you have done that. The terminals will then be like for like.

Only problem might be, if your car needs some coding done. So probably best to have an auto electrician do it. This can be how some garages and particularly main dealers get to charge over the odds. Short and curlies come to mind.

John
 
Jul 18, 2017
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I have no intention of changing the batteries myself, but the idea is to source the batteries from somewhere like Tayna and to supply them to the fitter.

I don't think it would be a good idea to have lead acid batteries inside the cab of the vehicle and the Jeep electronics is very fussy about which type of battery is used.

As for the wrench I do need one for the odd job that maybe I can do. Although I may struggle, at least I am making the attempt. Anyway to check the AH and the CCA of the aux I need to remove the plate covering the label. I can't use the torque wrench to do that and saw no point in buying a complete socket set with wrench when I already have a socket set for the wrench.

Lastly I like to learn about things like this as it helps keep the mind a bit active and I do not get ripped off when going to a fitter. Some things I know about, but just need confirmation so that I do not order the incorrect item Online. Thanks everyone for your input.
 
Jun 20, 2005
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Tayna? I thought you were anti buying from such places because of previous return issues?😉

I recently bought a new leisure battery from them . Top product cheap price👍👍
 
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JTQ

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Tayna? I thought you were anti buying from such places because of previous return issues?😉

I recently bought a new leisure battery from them . Top product cheap price👍👍
As has been my experience over many years for myself and friends, always first class, the packaging, the delivery speed & condition, and the products received. All have been by quality leading brands; I have not purchased any of the ones they have made.
 
Jul 18, 2017
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As has been my experience over many years for myself and friends, always first class, the packaging, the delivery speed & condition, and the products received. All have been by quality leading brands; I have not purchased any of the ones they have made.
My issue was a faulty battery and if it needs to be returned the hassles associated with it. There is no issue with their packaging, delivery speed and condition.

I have to admit that in that case it was a battery for the Corolla and the battery was one of their unknown brands and cheap which is why I now prefer to stick to well know brands whether buying from a shop or Online. :D

Can someone please comment on the small screw type post on the negative of the battery? It is obviously a fitment, but not sure if it is supplied with the battery on not?

As an after thought regarding the battery, initially I thought there was only one battery in the vehicle. When I found out there were two batteries even then I suspected only one of the batteries being an issue.

I am fairly sure I could managed if it was just the aux battery, however I have had conflicting advice that I may lose settings in the vehicle if the battery was disconnected unless I had a Memory type unit that holds the memory, I decided to abandoned that train of thought. If it happens at the fitter, it is their issue to resolve the issue.
 
Nov 11, 2009
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Tayna? I thought you were anti buying from such places because of previous return issues?😉

I recently bought a new leisure battery from them . Top product cheap price👍👍
My experience with an online battery supplier in the NW was excellent for the purchase but a nightmare when it went wrong. A bit like insurances a great purchasing experience but can terrible when things go awry.

In comparison the much derided eBay was excellent recently. I bought a lower bumper body part which on delivery wasn’t quite as advertised. The company weren’t prepared to supply three fastenings. So I opened a “return link” and immediately received a prepaid 48 hr tracked printable label and QR code. Took it to my local PO and four days later obtained my refund in to the credit card. Now if the battery supplier I had used was as good as eBay I would still be giving them my business.
 
Jun 20, 2005
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This link may help . As far as I can see there is no need to re boot any of the ecu things.Note the main battery has to be turned on its side to facilitate removal. The auxiliary battery needs the post fastenings transferring. I’m inclined to think a good auto electrician could do this for you at home with either he or you supplying the batteries. He may surprise you and say you don’t need both changing🤔

Will you be videoing your efforts😁
 
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