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Short question - does a battery maintainer charge the battery as good as the car's alternator?
Long story:
I have a 2007 LS460 L (RWD) with about 120k mileage. I don't drive it a lot and it stays in the garage for most of the time. When the battery drains, I start getting the famous "3 warnings" - VSC, ABS and Brake Systems. After driving the car for a few days, those warnings go way. Google search indicates those warnings will show when the battery is low, when the computer cannot read the sensors. Makes sense.
To prevent the battery from draining, I connect the battery to a maintainer (trickle charger) when I parked in the garage. I disconnect the maintainer before I drive the car. The car starts every time. The battery is 100% healthy according to battery testers. However, the famous "3 warnings" always show up every time. And they won't go away unless I drive the car continuously for a few days. If I drive the car everyday and don't use the battery maintainer, the warnings will never show up.
I am trying to understand the logic here. If the maintainer charges the battery as good as the alternator, why would those warnings show up? Is it possible that the warnings are not related to the battery at all? If that's the case, what they are related to? I know for sure those are not permanent warnings as they always go away after I drive the car for a few days. Thank you!
Last edited by helloguys; Mar 5, 2025 at 03:26 PM.
Not necessary battery related issue. I see on the photo you have your parking brake is set. Are you leaving your car on the parking brake for a long time? If yes, try to park your car without engaging your parking brake when you put it away for the extended period next time. You might have sticky parking brake actuator or something else of that nature that prevents normal brake release when you take it out of storage. Maybe your brake system just needs some good servicing.
It depends on the "maintainer" you are using. Some of them are almost useless. They will only provide a minimal charge to the battery. And certainly if your battery is depleted, they will not charge the battery. I would recommend you purchase a CTEK 7002 or CTEK MXS 5.0. I prefer the 7002.
Yes, the alternator charges the battery just as good as a maintainer. The difference is the alternator only charges while the engine is running. The battery maintainer does just that, it maintains the full charge. You either have a old battery that is losing charge or an electronic that is causing a parasitic drain.
I would recommend you purchase a CTEK 7002 or CTEK MXS 5.0. I prefer the 7002.
I bought a MXS 5.0 and it lasted for 7 months and it was unreliable for even that short time, I have to charge my car about every 3 days to keep the batt in good shape so the POS will start when I want to use it.
Try this, I have 6 of them attending to the fleet and they are excellent.
I have two cars with 8 year old batteries that are still perfectly able to sit for a month and start thanks to these maintainers keeping the cells like new.....
The 460 should be able to sit for at least 3 weeks and start no problem, when my wife "crashed" mine it sat outside for a bit under 2 months and still started no issues off a maintainer. My LS430s never last a month though, usually dead in two weeks max.
Whenever I buy a new car I always let it sit for one month to check for draw or air suspension leak down issues, the RXs and LSs are what forced me to buy chargers as they were problematic. The 460 was surprising in that it didn't have a problem, I was expecting an issue out of my A8s but the 4.0 was left off tender for a whole winter and it started zero issues.
Phaeton did flatline one of its batteries when I had it at my shop for a few weeks waiting for me to replace all fluids etc, that's was a non issue though as I simply told it use the other one.
Last edited by Striker223; Mar 7, 2025 at 01:21 PM.
I bought a MXS 5.0 and it lasted for 7 months and it was unreliable for even that short time, I have to charge my car about every 3 days to keep the batt in good shape so the POS will start when I want to use it.
See, that's why I prefer the7002!
I think you may have gotten a defective unit, because I have read very positive reviews of the MXS. That is why I mentioned that model, but I have no experience with it.
I think you may have gotten a defective unit, because I have read very positive reviews of the MXS. That is why I mentioned that model, but I have no experience with it.
I think it was a faulty unit too, I ordered a 7002 earlier today because it has the power supply feature and the voltage on the MXS seemed to vary but was mostly around 15.3, I wanted the 13.5v for updating some software later on this year.
I think it was a faulty unit too, I ordered a 7002 earlier today because it has the power supply feature and the voltage on the MXS seemed to vary but was mostly around 15.3, I wanted the 13.5v for updating some software later on this year.
I've had the 7002 many years now and used it on several different cars (and my snowblower) and I have been very happy with it. I'm sure you will be also.
I've been using the "Battery Tender" models for a while. I have the 750ma one that I use for my motorcycle and the 1.25 amp one for the LS. I've had zero problems with them but I do have a stronger charger for use when a battery is very low/discharged.
Last edited by Protholl; Mar 9, 2025 at 09:31 AM.
Reason: Corrected spelling
I've had the 7002 many years now and used it on several different cars (and my snowblower) and I have been very happy with it. I'm sure you will be also.
The 7002 seems to be a better built unit for sure.
Battery maintainer vs. Alternator?
