Battery Charging

[Tuppence]

Hello,

I have a an IS 250 SE 2005 think I need to charge Battery, have a ctek charger.  Sorry for daft ? but do I put the negative on the neg Battery terminal or a part of the car's metal-work.  Thanks

 

[Texas]

According to the C-Tek manual it says ‘Battery inside vehicle connect to chassis (away from fuel lines!) but I have connected mine with the permanent ring ended C-Tek Comfort connector straight onto Battery terminals so 🤷🏼

[Linas.P]

On the Battery terminal. Honestly cannot see any rationale for connecting it to car body. I guess somehow Ctek thinks it is better in case of some issue that instead of blowing the charger it blows something in car, but I can't see how that could be better.

Basically when connected directly to the Battery it is the charger or the Battery which will be damaged in case something goes wrong (although Ctek should have built in protections). When connected to car body, it is the car electrical system which will be damaged - I assume weak point will be combination fuse if you lucky. But trust me - you don't want electrical issues on IS250!

[LenT]

 

24 minutes ago, Tuppence said:

Hello,

I have a an IS 250 SE 2005 think I need to charge battery, have a ctek charger.  Sorry for daft ? but do I put the negative on the neg battery terminal or a part of the car's metal-work.  Thanks

 

Not daft at all!

Best practice is considered to be to use a metal earthing point away from the Battery.  Generally you can use the point where the negative lead connects to the body.

The reason is that the old style of lead acid batteries could produce hydrogen gas which would form an explosive mix with the oxygen in the air should there be a spark.

With modern batteries this is very unlikely, but you will still see experienced mechanics doing it.

However, as you have a CTEK, you should do as Paul has already suggested, and get the connectors that fit permanently to the Battery posts and then connect to a separate lead from the charger.  You can get a connector that has a traffic light system of leds that give a reasonable indication of the Battery charge level.  I’ve fitted them to both our cars, so I just have to lift the bonnet to check out the Battery.

You can see them on the CTEK website.

https://www.ctek.com/uk/battery-chargers-12v-24v/car-charger/ctx-indicator-eyelet-m8

[Barry14UK]

I connect my charger direct to Battery terminals,  However, my Lexus manual does say to connect the negative charger lead to a more remote part of the chassis (presumably to help avoid  the very small chance of a spark igniting any improperly vented Battery gas).  

[Tuppence]

On 4/4/2022 at 2:33 PM, LenT said:

 

Not daft at all!

Best practice is considered to be to use a metal earthing point away from the battery.  Generally you can use the point where the negative lead connects to the body.

The reason is that the old style of lead acid batteries could produce hydrogen gas which would form an explosive mix with the oxygen in the air should there be a spark.

With modern batteries this is very unlikely, but you will still see experienced mechanics doing it.

However, as you have a CTEK, you should do as Paul has already suggested, and get the connectors that fit permanently to the battery posts and then connect to a separate lead from the charger.  You can get a connector that has a traffic light system of leds that give a reasonable indication of the battery charge level.  I’ve fitted them to both our cars, so I just have to lift the bonnet to check out the battery.

You can see them on the CTEK website.

https://www.ctek.com/uk/battery-chargers-12v-24v/car-charger/ctx-indicator-eyelet-m8

 

[Tuppence]

Thank you Gents for your help re Battery charging.  Thanks Len for the link to the "traffic light gadgit"  Have ordered one, will get garage to put it on when car goes for service.

[Herbie]

On 4/4/2022 at 1:21 PM, Linas.P said:

On the battery terminal. Honestly cannot see any rationale for connecting it to car body. I guess somehow Ctek thinks it is better in case of some issue that instead of blowing the charger it blows something in car, but I can't see how that could be better.

Basically when connected directly to the battery it is the charger or the battery which will be damaged in case something goes wrong (although Ctek should have built in protections). When connected to car body, it is the car electrical system which will be damaged - I assume weak point will be combination fuse if you lucky. But trust me - you don't want electrical issues on IS250!

Sorry Linas but that's wrong.

The only reason for the advice to use any unpainted part of the body/screw/nut is purely for safety reasons, not electrical reasons.

A charging/charged Battery can release hydrogen gas, which can be explosive if ignited. If the negative Battery terminal is used and a spark is created as you take the croc clip off it, it could* cause an explosion - this is the reason to use any nut/bolt/screw - so that it's far enough away from the gas that there's no risk of explosion.

It makes not one iota of difference electrically, and it doesn't matter in the slightest where the negative croc clip is connected, from an electrical point of view.

*In more than 45 years of spannering, driving, and generally messing around with cars, I have never personally experienced an explosion, nor have any of my friends, family or workmates and when asked, it was discovered that all of us just connect to the negative Battery terminal. Not only does there have to be the gas and a spark, but it also has to be present in the correct proportions for an explosion to occur.

[Linas.P]

I don't think that is realistic possibility (and as you said you have never heard of it happening in 45 years) to generate so much hydrogen that spark from clamp would make an explosion. Literally I have never heard of it happening. What is realistic possibility is that when charging bad Battery it could short, overheat and if connected via body of the car instead blowing just a Battery or the charger, it would destroy entire car electrical system. That said decent chargers have protection from that and should never result in Battery overheating, it may short, but charger should sense it and stop charging. 

[Herbie]

59 minutes ago, Linas.P said:

What is realistic possibility is that when charging bad battery it could short, overheat and if connected via body of the car instead blowing just a battery or the charger, it would destroy entire car electrical system.

Nope, again Linas, that's wrong.

The negative Battery terminal is clamped directly to the body anyway, so in effect the whole body and every screw, nut and bolt become the negative Battery terminal. What possible difference - electrically speaking - can a few inches of steel/aluminium/whatever make? The answer is, none.

[Mr Vlad]

I've seen many a thread on charging the car Battery on a few different brand car forums. Personally I find it strange/weird that on various cars there are no points other than the Battery posts to connect a charger. Also weird/strange that there are various cars with a dedicated negative post to connect a charger to. Also weird/strange that there are cars with dedicated positive posts to connect a charger to. Also weird/strange there are cars with both a negative and a positive post to connect a charger to. No wonder there a folk who wonder how to connect a charger. Me? The only time I've had to connect a Battery charger I actually removed the Battery then charged it. That's how I first saw it decades ago and it seems the only way to do it and safely even with fancy chargers. 

[NemesisUK]

Could it be that by connecting via a body part the Battery monitoring module (if fitted) can detect the recharge, so the car's systems know? Certainly with my Mercedes it was always recommended to do so, for that very reason.  In fact that's how the Mercedes dealer fitted the CTEK permanent charger connections for me.

[Herbie]

2 hours ago, NemesisUK said:

Could it be that by connecting via a body part the battery monitoring module (if fitted) can detect the recharge, so the car's systems know?

In a word, no.

As I said above, it makes absolutely no difference whatsoever to the electricity whether it goes directly to the negative Battery terminal or to a bolt head a few inches away. As long as there is a metallic conductive path, it will get to that negative Battery terminal.

[NemesisUK]

13 minutes ago, Herbie said:

In a word, no.

As I said above, it makes absolutely no difference whatsoever to the electricity whether it goes directly to the negative battery terminal or to a bolt head a few inches away. As long as there is a metallic conductive path, it will get to that negative battery terminal.

I understand that but my point was to do with the car's monitoring system. If one were to connect directly to the Battery terminals it would not pass current through the Battery monitoring module. I agree it makes no difference to the charging of the Battery but does to the car's system. Mercedes workshop files state to connect across the BMM so it and the car system knows the Battery is being charged.

[GMB]

7 hours ago, Herbie said:

In a word, no.

As I said above, it makes absolutely no difference whatsoever to the electricity whether it goes directly to the negative battery terminal or to a bolt head a few inches away. As long as there is a metallic conductive path, it will get to that negative battery terminal.

Herbie is right. From my school days electricity will always take the path of least resistance so if you connect to the body or the terminal it is the same result. It is as if you were connected to the same point i.e. resistance being negligible. Any other sensitive components that may or may not be monitoring the electrics should have or normally have protection built-in to counter adverse situations.

It is unlikely that you will get anything more than about 13.5v (within the tolerances) but you could get less or a short, and that would trip the charger.

Basically it is a can of worms.

 

 

[Herbie]

10 hours ago, NemesisUK said:

I understand that but my point was to do with the car's monitoring system. If one were to connect directly to the battery terminals it would not pass current through the battery monitoring module.

It must do, otherwise how does it monitor the Battery during normal running?

Plus, as Graham says, electricity will take the shortest path so if you connect the lead 5" away from the Battery terminal, it won't decide to go to the monitor first. Maybe Mercedes have got some proprietary system that is designed to work in the way you say, I don't know.

[Texas]

The cars ‘battery monitoring system’ ( if fitted ) would only be in operation when ignition is On/engine running ie alternator is actually outputting. So if a CTek is fitted and car is Off then no monitoring is happening.

[NemesisUK]

21 minutes ago, Herbie said:

It must do, otherwise how does it monitor the battery during normal running?

During normal running the only return route for current is through the car body, so passing through the Battery monitor sensor connected between the negative and body. If the trickle charger is connected directly to the Battery terminals, the current would take the shortest/easiest route, which is through the Battery?

[NemesisUK]

11 minutes ago, Texas said:

The cars ‘battery monitoring system’ ( if fitted ) would only be in operation when ignition is On/engine running ie alternator is actually outputting. So if a CTek is fitted and car is Off then no monitoring is happening.

There is no mention of IGN status within the guidance doc but the module does retain a history of Battery condition, which is used to determine Battery working capacity used in determining if electrical consumers should be enabled or not (i.e. seat heaters) when IGN is on. It's a complicated system and not well described, presumably because they expect the technician to have training?

[Texas]

So if an external source is increasing the charge of the Battery ( the CTek ) directly onto the terminals, then the cars monitoring system is ‘just’ going to see a better Battery  and as this external source of charge never actually went through the cars charging/monitoring system then what are the possible implications? ( apart from a better state of charge)

 

[NemesisUK]

I really don't know.... There must be some rationale behind it or why introduce the complication?

[Texas]

My sons 335 BMW has a charging system that requires the actual size, Ah and CCA to be input into car via OBD software as the system is so precise that it increases the amount of charge as the Battery ages and if not coded then a New Battery when fitted will be over-charged and not last very long.

[NemesisUK]

I thought I was being adventurous when I replaced the generator on my Imp with an alternator! How things have changed ...