Trickle charge at 15.5v ?

toptime · 16 Feb 2019

Hi everyone,
I just noticed that my 07 C2 is trickle charging at 15.5v
The charger is an Aldi smart charger / conditioner which shows the charging voltage. I've been using it since the start of the winter and it has been working fine but I'm sure it was charging at less the 14v when I used it last.
I'm assuming the voltage is slightly higher as the current is now low as it trickle charges.
Anyone have any experience with this? Or maybe the same voltage on the same charger? Seems a bit high to me........

kurlykris · 16 Feb 2019

Can you check the voltage at the battery terminals with a digital Multimeter to verify the actual voltage ?
You`ll boil the battery at anything over 14.4v and it will be gassing :nooo:

toptime · 16 Feb 2019

Yes that was my concern

As soon as I unlock the car (and put a load on the battery) the charger display drops to 12.9v and I measure the same with the mm. If I switch the charger off the battery voltage is 12.7v which is fine.
Switch the charger back on and it shows 12.9v then rises back to 15.3v with 5 to 10 mins......
Weird.......
Something to do with surface charge maybe?

kurlykris · 16 Feb 2019

You`ll only see the surface charge after you have disconnected the charger, it should only be about 0.5v, I usually put a small load on the battery for 30 seconds or so, then leave it for an hour or 2 before I test the open circuit/actual voltage of the battery.
It sounds like the voltage regulator is fubarred in your battery tender to me :nooo:

toptime · 16 Feb 2019

Sounds like it's time for a new charger then!
Ironically it's sat at 13.7v for the last hour.!

deMort · 16 Feb 2019

If the charger is over chargeing the battery then the battery will be warm to the touch .. if a severe over charge then it will get hot and you will have an acrid smell .. it will make your eyes water .

Ive seen it .. battery was the shape of a balloon .. we couldnt go near the car for the smell and we pushed it outside to cool down .. full protective gear and we finally removed the battery once it had cooled down .. scary stuff !

That was an alternator fault pushing over 18 volts into it though .

997 and they can charge upto 16 volts .. its normally when a battery is very dead or a possible fault .. but at that voltage it doesnt seem to boil a battery .. close to the edge though in my books .

basically what im saying .. see how hot the battery is .. if cold then dont worry .. if its getting warm then the charger is faulty or the battery is .

IMHO anyways .

toptime · 16 Feb 2019

Thanks for the replies guys. Battery is not warm, no smell and no signs of anything untoward. If the charger didn't have a readout I would have no reason. To think anything is wrong.
Really don't want to risk cooking anything though so I think I'll get another one.

Luddite · 18 Feb 2019

OK, I have zero knowledge of gel batteries, and my info only really applies to lead acid batteries thus may be of little use here..

With the alternator charging the battery 13.2 volts and under too low 13.8v to 14.5 OK above 14.5v too high.

In the case of lead acid batteries, if charging or discharging heavily they give of EXPLOSIVE gas and if my poor memory is correct the gas is Hydrogen..? I have seen the aftermath of an accident where a battery exploded blinding an engineer in one eye as the result of the gas build up external to the battery being exposed to a flame.. though any kind of spark caused by disconnecting a charger lead crocodile clip before switching the charger off can cause an explosion if the battery is gassing, same goes for a loose clamping arrangement on one of the terminals and the ign key turned to start position...creating a spark at the terminals...

Battery fully charged taken off the charger and left disconnected from any circuit for approximately an hour and voltage readings taken across the battery terminals.

12.72 volts 100% efficient 12.52v 80% 12.3v 60% 12.12v 40% 11.9v 20%

Taking voltage measurements with the battery connected in the car can give readings that mislead given the demands of the circuits connected, often referred to as parasitic losses. A worst case scenario might be measuring across the battery terminals with the starter turning the engine over and not starting, where a reading of 10v to 10.6 might be considered average, though could be as low as perhaps 4v if the battery is on it`s last legs but still able to turn the engine over, all be it slowly..

No doubt this info is well out of date, but may just be of use to those with older Porsches running lead acid batteries...?

toptime · 18 Feb 2019

So, I exchanged the charger for a new one yesterday. I checked the charger after about 6 hours and it was showing 13.7v. Checked again this morning and its back to 15.3v :?:
The battery is a Bosch S5 and all appears well......

jl-c · 18 Feb 2019

You don't say what you replaced it with. Much as I like Aldi biscuits I would not trust my Porsche to an Aldi branded battery charger. Buy ( or borrow, I guess) a CTek. Totally your choice but not a road I would go down. Things are cheap for a reason......

toptime · 18 Feb 2019

I replaced it with like for like from Aldi. The Aldi / Lidl units get very good reviews and are used by owners on the premium car forums. It was the reviews that made me aware of them and so I picked one up to give it a try.

I also noticed on the back of the packaging of the new charger that the charging end voltage is between 15.1v and 15.5v so this answers my original question.

Thanks all for your help.

MisterCorn · 18 Feb 2019

I don't know my people rate CTEK chargers so highly. They are certainly OK, but of the two trickle chargers I have ever had fail on me, both have been CTEK ones. They are generally OK, but certainly not 'fit and forget'.

MC

jl-c · 18 Feb 2019

Just speak as you find, you obviously fell unlucky. I have 4 CTek's which are all in use most of the time (if not on a car, re-conditioning spare batteries) and have been absolutely faultless. ( so that should put the kiss of death on them! ) :floor:

maph · 18 Feb 2019

OP, glad you are sorted :thumb:

Regards C-tek my first charger stopped working with little use (mode button packed up, a common fault apparently) making it impossible to use.

I now have two newer C-tek MSX 5.0s, but I am not totally convinced with these either. I was charging one of my other cars in storage (BMW M Coupe) and it was all lit up with a full set of green lights, doing it's pulse stage apparently....... went to take it out and the battery was completely stuffed.

Reconnected it, put it in a restore mode, checked it a few days later, again all green lights, happy days....... no battery still dead.

New battery and has not skipped a beat since, just do not trust the c-tech's reporting any more, not so smart me thinks.

Again, I am probably unlucky but I agree that their reputation seems higher than the quality of their products.

Oggie · 19 Feb 2019

Charging at 15.5V isn't unusual for a "smart" or "multi-stage" charger. On some chargers (I'm not familiar with the Aldi charger) have a stage called equalisation which will charge at a higher voltage of between 15V and 16V for a period to reduce sulphation and stir up the electrolyte to stop stratification that can occur in wet type lead-acid batteries.

For more info, there is an article on the charging stages here: http://www.chargingchargers.com/tutorials/charging.html

Trickle charge at 15.5v ?

toptime

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kurlykris

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kurlykris

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