Flat Car Battery Issues

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634 posts

Ultimate Geek

#3370039 2-May-2025 16:22

richms:

Yes, but if you are in range some of the time but not at the right time, you miss its transmission - the phone doesnt connect to it on demand when present near it. When the car is running you get live data and it will let you know about voltage drop when cranking and chargeing voltage etc, but for something that you walk past twice daily when its idle, its hopeless to get an alert about it getting low.

ah, yes i see. bluetooth devices, as well as pertinent apps, should resume the connection (and functionality) when they see each each other again.

Lenovo

Shop now for Lenovo laptops and other devices (affiliate link).

johno1234

2688 posts

Uber Geek

#3370042 2-May-2025 16:25

Asteros:

richms:

I know a couple of people that also bought the cheap small ctek to put on unused cars and have found the car battery dead and the charger flashing error after leaving it for a month or so. They are not put it on and forget about it things and I am a little annoyed that noone seems to be making an IoT car battery charger that lets me keep an eye on it.

In my experience Ctek chargers perform very well. I bought mine in NZ and it came with a 5 year warranty. They are set and forget. Agree errors usually come from a battery that needs to be replaced.

I have the little ctek 3.8A on the JetSki and a 10A for the cars. By cheap I think the OP meant lower current less expensive. The little ones are not much use and too slow for large batteries. The big ones are a lot more expensive.

outdoorsnz

669 posts

Ultimate Geek

#3370043 2-May-2025 16:27

nitro:

wonder if you've blown a (DMM) fuse. that other terminal usually has a 200mA limit.

if you get it showing the 3.2A parasitic drain, start disconnecting the fuses (the car's) one at a time until you find the one that clears the current drain.

200mA fuse is blown, but that could have happened some time ago.

So I tried putting black in common (MM) and red in 10A unfused (MM) and completing the circuit, but still got some numbers like 36 that jumped around briefly and then showed 0.01A.

Would blown fuse prevent correct reading?

mdf

3490 posts

Uber Geek

Trusted

#3370069 2-May-2025 20:48

What are best practices for charging car batteries? I've got a CTEK MXS5 like mentioned earlier in the thread (currently charging the battery that - as the Universe would naturally have it - was flat during the worst weather of the year). It comes with the option of eyelet fly leads which I had always assumed were intended to be permanently mounted to the car's wiring harness where it meets the battery. Since, you know, the manual has a picture with that very option. However the manual also says to mount the neagtive clamp to bare metal on the chassis (hydrogen gas explosions...)

Again unsurprisingly, t'internet was not in unanimous in resolving my confusion. I've seen sites advocating always removing the battery from the car/car wiring, never removing from the car, clamp to battery poles, never clamp to poles, and chargers are actually a scam perpetuated by Big Battery and/or the Illuminati.

Any advice please?

Ge0rge

2021 posts

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Lifetime subscriber

#3370070 2-May-2025 20:56

My three vehicles have them directly connected to the battery terminals. I also keep an eye on a few quads and rideon lawnmowers for friends, also connected directly to the battery terminals. My rideon and quad are permanently on charge with an MXS5.0 except when they are in use.

Vehicles at work have them directly connected to the batteries as well, as do the majority of NZFS fire appliances - although they tend to have the charger onboard the vehicle, as do the majority of caravans, campervans, motorhomes etc but still directly connected to the batteries. Take from that what you will.

johno1234

2688 posts

Uber Geek

#3370076 2-May-2025 22:15

mdf:

What are best practices for charging car batteries? I've got a CTEK MXS5 like mentioned earlier in the thread (currently charging the battery that - as the Universe would naturally have it - was flat during the worst weather of the year). It comes with the option of eyelet fly leads which I had always assumed were intended to be permanently mounted to the car's wiring harness where it meets the battery. Since, you know, the manual has a picture with that very option. However the manual also says to mount the neagtive clamp to bare metal on the chassis (hydrogen gas explosions...)

Again unsurprisingly, t'internet was not in unanimous in resolving my confusion. I've seen sites advocating always removing the battery from the car/car wiring, never removing from the car, clamp to battery poles, never clamp to poles, and chargers are actually a scam perpetuated by Big Battery and/or the Illuminati.

Any advice please?

my ctek manual is clear that the cable can be wired directly to the battery +/- terminals.

nitro

634 posts

Ultimate Geek

#3370078 2-May-2025 22:53

mdf:

It comes with the option of eyelet fly leads which I had always assumed were intended to be permanently mounted to the car's wiring harness where it meets the battery. Since, you know, the manual has a picture with that very option. However the manual also says to mount the neagtive clamp to bare metal on the chassis (hydrogen gas explosions...)

i have the same charger, and i charge connected directly to the battery terminals, for the following reasons:

good smart chargers should be able to manage charging better, such that they aren't overcharged (which is when venting is most likely to happen)
no convenient bare metal part near the battery, and the short leads on those cteks (would also have to remove the plastic engine cover)
availability of those permanently attached (directly to the battery terminal) pigtails, such as ctek's (really, what's the difference between connecting the charger to those and connecting the charger clamps directly to the battery terminals?)
where else would you connect when charging (new batteries before installing) out of a car? are venting and explosions not an issue then?

also just checked the owner's manual, which:

for jump starting, does state to use the vehicle ground:

but nothing of the sort for recharging (does advise to disconnect the negative terminal, which would protect the electronics):

this is my personal method, and have thankfully not had any catastrophic experiences doing so. not trying to convince anybody to do the same.

tweake

2291 posts

Uber Geek

#3370148 3-May-2025 10:20

mdf:

What are best practices for charging car batteries? I've got a CTEK MXS5 like mentioned earlier in the thread (currently charging the battery that - as the Universe would naturally have it - was flat during the worst weather of the year). It comes with the option of eyelet fly leads which I had always assumed were intended to be permanently mounted to the car's wiring harness where it meets the battery. Since, you know, the manual has a picture with that very option. However the manual also says to mount the neagtive clamp to bare metal on the chassis (hydrogen gas explosions...)

Again unsurprisingly, t'internet was not in unanimous in resolving my confusion. I've seen sites advocating always removing the battery from the car/car wiring, never removing from the car, clamp to battery poles, never clamp to poles, and chargers are actually a scam perpetuated by Big Battery and/or the Illuminati.

Any advice please?

for permanent wiring connect it direct to battery terminals.

the reason for clamping on the chassis is in case it sparks and ignites the hydrogen (same with jump starting). and yes i've seen it happen, having a workshop sprayed with acid is not fun. however good chargers will generally run at a lower voltage to avoid off gassing. but regen mode and full calcium mode will deliberately run the voltage higher to create gas which helps stir up the acid.

off course when you have the battery totally disconnected you can't do that and should leave it for a while for the gas to dissipate.

MikeAqua

7769 posts

Uber Geek

#3370584 5-May-2025 13:56

Just a quick comment to say that calcium batteries do best when charged with the correct charging profile. Most multistage chargers provide this.

I have three c-teks for the boat (start, trollingmotor/winch, house) to keep the batteries topped up when it's on the trailer. I've had them for years and they are excellent. I also have a Repco multi-stage charger in the garage, it's also a few years old and does a perfectly good job.

Mike

Bung

6351 posts

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Subscriber

#3370606 5-May-2025 14:50

MikeAqua:

Just a quick comment to say that calcium batteries do best when charged with the correct charging profile. Most multistage chargers provide this.

AFAIK that isn't something that cars do. They are routinely supplied with calcium batteries but the alternator only reaches about 14.5v which isn't quite enough to get the electrolyte stirred up.

Wheelbarrow01

1702 posts

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Chorus

#3370677 5-May-2025 21:57

johno1234:

The stop/start battery on our Touareg finally gave up after an incredible 12 or 13 years old. I wish I could remember what brand it was but it was likely to be the factory original as the car was only 2 years old when we bought it. It's a huge, very expensive battery and a pain to replace as involves removing the front passenger seat to access it.

I can't stand the stop-start feature. It is hard on batteries, ring gear, pinion and starter. Worst of all, the engine decides to conk out just when you need to hoof it into a gap in the traffic. It's almost a reflex reaction to hit the deactivate button when I start the car. As far as I can tell it can't be re-programmed to default inactive instead of default active.

For what VW charges for a Touareg battery, they had better last 12-13 years! I posted about my last battery purchase at the time...

Based on the size of the battery you could start a mining truck with it (or a small ship) but I admit it's a V8 diesel so it does need some grunt I guess.

Likely half the reason why mine failed was because both during and after covid I started working from home a lot more and so the car started to be used less frequently, and for shorter trips. But since replacing the battery a couple of years ago, I routinely stick it on a smart charger overnight around once every 3 months and haven't had any problems. I connect the charger to the remote +/- poles under the bonnet, because bugger trying to reach the actual battery terminals under the seat...

For the record, I charge all my cars' batteries (I have a few rarely driven project cars) without disconnecting the battery from the cars and have never had any issue. Smart charger, max of 6 amps from memory.

nitro

634 posts

Ultimate Geek

#3370680 5-May-2025 23:07

Wheelbarrow01:

Likely half the reason why mine failed was because both during and after covid I started working from home a lot more and so the car started to be used less frequently, and for shorter trips. But since replacing the battery a couple of years ago, I routinely stick it on a smart charger overnight around once every 3 months and haven't had any problems. I connect the charger to the remote +/- poles under the bonnet, because bugger trying to reach the actual battery terminals under the seat...

ctek used to advise simply connecting the charger directly to the battery terminals. however, with the advent of BMS in modern cards, they now advise either using those charging poles, or positive battery terminal and vehicle ground. this way, the BMS is made aware that the battery is getting charged and act/react accordingly.

johno1234

2688 posts

Uber Geek

#3370691 6-May-2025 06:50

Ctek mxs manuals still say connect to battery. I’m my car the battery is not conveniently accessible so I use the positive pole in the engine bay and earth. Electrically it’s the same circuit.

Bung

6351 posts

Uber Geek

Subscriber

#3370695 6-May-2025 07:56

It will depend on publishing date. The MXS 5 instruction video is 7 years old now. The video that mentions BMS is 1 year old. The car used in the video isn't identified but could be a VW clone. Not something I'll run into 😁

tweake

2291 posts

Uber Geek

#3370809 6-May-2025 09:37

nitro:

ctek used to advise simply connecting the charger directly to the battery terminals. however, with the advent of BMS in modern cards, they now advise either using those charging poles, or positive battery terminal and vehicle ground. this way, the BMS is made aware that the battery is getting charged and act/react accordingly.

thats an interesting point. the difference between post and chassis is where the amp meter is on the ground cable. by using the chassis the sensor can read how much charge.

however i doubt that connecting to a post would be an issue. the main thing a bms does is to stop draining the battery to much and to monitor/control charge rate while driving. it would check battery voltage on startup and go from there regardless. domestic plug in chargers are not big enough to cause an issue.

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