Battery Charging

[M6AJJ]

This may be a simple question but I would like to know the best way to charge the battery on todays modern cars.

Due to various reasons the car (S Class) is only being used perhaps once every two weeks at the moment, and this is not enough to keep the battery charged. Normally you would disconnect the battery and put it on trickle charge every couple of weeks and that would solve the problem. However, I am very loathe to disconnect due to all the complicated electrics that would need resetting.

Can the battery be charged still fitted to the vehicle, and if so which is the best way to do it?

Any help much appreciated.

 

[Silver Arrow]

"Due to various reasons the car (S Class) is only being used perhaps once every two weeks at the moment, and this is not enough to keep the battery charged."

Battery should survive a lot more than a couple of weeks. I suggest that you first get a new battery.

Then. if you must, use a low trickle charger with the electrics connected. I have a 1 amp old job for this. If you have a window handy, one of the solar panels sold by caravan shops for about £20 will keep the charge up. (I have one on a small boat I leave parked on a lake).

 

[television]

Silverarrow is wise in keeping his old trickle charger.
these days one can only buy a Auto charger and as soon as you plug that in the serge for the first few minutes is what messes up MB's.
I am in the middle of an article on this, its quite involved.

AS a safety measure for now, start the engine, join up the charger and turn on, let it all run for a few minutes, then turn engine off.

Malcolm

 

[Ian Brown]

Silverarrow is wise in keeping his old trickle charger.
these days one can only buy a Auto charger and as soon as you plug that in the serge for the first few minutes is what messes up MB's.
I am in the middle of an article on this, its quite involved.

AS a safety measure for now, start the engine, join up the charger and turn on, let it all run for a few minutes, then turn engine off.

Malcolm

Malcolm if the battery is flat how is it possible to start the car with a flat battery before you connect the charger to charge it? then on the other hand if the battery is strong enough to start the car then the battery may not need charged.

 

[television]

Malcolm if the battery is flat how is it possible to start the car with a flat battery before you connect the charger to charge it? then on the other hand if the battery is strong enough to start the car then the battery may not need charged.

the thread was to keep the battery charged and in good order when not being used.

When a battery is flat, a voltage from the charger can exceed 30 volts to get the battery to the bottom of the curve of the useable part of the battery, once the battery has reached this point the voltage and charging current will go down to the trickle state.
Modern battery chargers are Auto (it cost money to put on a switch) therefor as soon as you join up it is the initial first few seconds that do the damage to our cars, the only safe way is to have the car running on its closed loop, and join in.

If the battery is flat, the car should be jumped started in the correct order.
I have found 31 different ways that MB's should be charged, depending on the car.

After being jumped the car's alernator should not be used to charge the battery,they are designed to keep the battery topped up, and not charging from flat. It is only the battery that keeps the alernator from self desruction and other parts of the car. you understand of coarse that in order to charge, the voltage from the charger must be higher than that of the battery in every case this is where the problems start, there is a margin or thin line, cross it and the problems start to appear on this forum.
As said I will do an article if anyone interested

 

[tamrsoft]

Connecting your trickle charger to the battery

I have never quite known the reason for not connecting a charger to the battery while in situ but the previous discussions now seem to account for this. I do not have an auto charger but a home built jobby that allows me to control the output in 1/2 volt steps and a built in precision ammeter to allow me to control the charging current. I assume that I can attach this to the jump start terminals under the bonnet and set the trickle charge at about 1/4amp with the battery in situ and without starting the car first.

 

[television]

I have never quite known the reason for not connecting a charger to the battery while in situ but the previous discussions now seem to account for this. I do not have an auto charger but a home built jobby that allows me to control the output in 1/2 volt steps and a built in precision ammeter to allow me to control the charging current. I assume that I can attach this to the jump start terminals under the bonnet and set the trickle charge at about 1/4amp with the battery in situ and without starting the car first.

Sounds fine to me, put it on minimum charge when you first join up, and adjust after a few mins, keep your eyes on it for the first hour.

whilst on this subject, another safe way is to turn on the heated seats if fitted and the rear demister, (this would save the large currents used by the starter) after the battery has been on charge a couple of mins turn the key and aux products off.

Malcolm

 

[Ian Brown]

Sounds fine to me, put it on minimum charge when you first join up, and adjust after a few mins, keep your eyes on it for the first hour.

whilst on this subject, another safe way is to turn on the heated seats if fitted and the rear demister, (this would save the large currents used by the starter) after the battery has been on charge a couple of mins turn the key and aux products off.

Malcolm

Surly Malcolm that wouldn’t be a good idea switching on the ignition before connecting the charger, just in case you damage the ECU when you power on the charger. Is that not why they manufactured anti spike jump leads to protect the ECU after the car you were jumping started.

 

[television]

Surly Malcolm that wouldn’t be a good idea switching on the ignition before connecting the charger, just in case you damage the ECU when you power on the charger. Is that not why they manufactured anti spike jump leads to protect the ECU after the car you were jumping started.

You cant have a spike big enough to do any damage on a closed loop with 50 amps flowing (rear window + seats, not ign only)

Malcolm
foot note This is the method that MB also recomend

 

[tamrsoft]

Based upon my original suggestion, is there any reason to switch on the ignition at all during the trickle charging period. The charger would be removed before ever attempting to start the car.

 

[M6AJJ]

So just to clarify, do I have it right? :

Star the car, if the battery is flat use jump leads from another battery.

Disconnect the jump leads and connect the charger.

Turn the engine off and leave battery to charge.


Many thanks for all your help so far, especially TELEVISION

 

[television]

So just to clarify, do I have it right? :

Star the car, if the battery is flat use jump leads from another battery.

Disconnect the jump leads and connect the charger.

Turn the engine off and leave battery to charge.


Many thanks for all your help so far, especially TELEVISION

Not quite, no time left now,will post this evening

Malcolm

 

[television]

Based upon my original suggestion, is there any reason to switch on the ignition at all during the trickle charging period. The charger would be removed before ever attempting to start the car.

No you do not turn on ign in your case.

Malcolm

 

[anyweb]

As said I will do an article if anyone interested

i'm interested !

cheers
anyweb

 

[Silver Arrow]

Most electronic units which are susceptible to power surges can be protected by suitable circuits. These tend to use capacitors and inductances to soak up the spikes. Putting things between the charger and the battery tends to be ineffective as the battery is itself a huge capacitor. I have circuits in my boat to prevent damage to things like GPS etc when I start up the engine. When you put on a new battery most things survive the short downtime, or you can parallel a battery to permit a chanegover without supply interruption.

Paralleling a discharged battery directly with a charged on will quickly discharge the new one as the charge will flow into the empty one.

 

[television]

or you can parallel a battery to permit a chanegover without supply interruption.

Paralleling a discharged battery directly with a charged on will quickly discharge the new one as the charge will flow into the empty one.[/QUOTE]

A Problem of putting a fully charged battery in parallel with a flat one.
If the donor battery has just been charged the voltage on it can be up to 15volts
B Problem with flat battery is that as the stored energy goes down below the useful curve the resistance goes up, this means that it can accept a voltage way in excess of 12 volts (to charge a totally flat battery you can put more than 30volts through it to get it to charge)
So when you put battery Ain parallel with B you are putting the 15volts through the sytem.

Answer you could cream off the top on battery A by joining up a load like a head light bulb for 10 mins. this is why I talk about closed circuits.

You can now purchase little 12volt cigar lighter back ups for memory on radio.
On all MB,s that I know the Radio is fed from the cigar lighter cable it is for sure from the 124 (first series)

Malcolm

And to those waiting to pounce on this subject it did not come from any data source

 

[Silver Arrow]

I have never used them previously, but there are some charger systems which use the lighter socket. That might make a convenient way of exchanging batteries too.

Whenever I fit a new battery, I always charge it on an automatic charger after it is delivered and before I fit it.

The emergency start packs will charge the pack up to 15v before use. (Son has an old diesel transit which has no glow plugs)

Most of the alternators and dynamos on my toys tend to be set at about 14.7 v

 

[turnipsock]

I'm getting confused by this thread.

Lead/Acid batteries don't handle being discharged to low levels very well.

A battery shouldn't drain in a couple of weeks. Running the engine every now and again would be a better solution, it also means that the engine parts remain coated with oil.

Using the alternator to charge a flat battery is not a good idea as it puts a large load on the alternator. Lead/Acid batteries have a low internal resistance so can draw/deliver a large current.

Personally, I think the safe way is connect the battery (still on the car) with jumper leads to another car and run the other cars engine for a bit. The two batteries in parrallel reduce the load on the alternator.

 

[Silver Arrow]

I agree: Returning to my original posting, If the existing battery discharges in a couple of weeks it's better to replace it.

 

[television]

I'm getting confused by this thread.

Lead/Acid batteries don't handle being discharged to low levels very well.

A battery shouldn't drain in a couple of weeks. Running the engine every now and again would be a better solution, it also means that the engine parts remain coated with oil.

My first thead said the above

Using the alternator to charge a flat battery is not a good idea as it puts a large load on the alternator. Lead/Acid batteries have a low internal resistance so can draw/deliver a large current.
My second thread said the above


Personally, I think the safe way is connect the battery (still on the car) with jumper leads to another car and run the other cars engine for a bit. The two batteries in parrallel reduce the load on the alternator.

Both cars should be in the closed loop mode, Donor car engine running, not reving. other car should have lights, heated rear window on to stop any surge, start car.

Threads become distorted, my first answer like yours is correct, then someone ask how do you start it with the battery flat, and here we are with two totally different situations.
I am in the middle of doing a good article that covers all possible situations

Malcolm