I've not been impressed with the way the battery is being charged on my Grand Voyager. Here is a practical and easy way to alter it -- no messing with the alternator.

1) Measurements over time indicated that initial alternator voltage after starting was 13.9volt. This dropped to 13.4 after a few minutes. This was consistent over time, and results in the battery being consistently under charged for most modern batteries. Measurements were done on a professional "Fluke" digital multimeter. Trust me, it's accurate.

2) Since most batteries sold over the counter are either lead-acid-calcium, or lead-acid-calcium-calcium, these type of batteries are undercharged at the above alternator voltages. Possibly these voltages are intended for some other type of battery.

Fortunately, there is an easy way to raise the charge voltage to 14.4volt without over stressing anything, as the design of the system is intended to do this -- I refer to the maker's own design here, not mine. 14.4volt is the 'old' charging voltage as used to be.

It consists of inserting a 33K0 (33,000ohm) half or one watt simple carbon film type resistor (worth about 10p.) in series with the live 5volt lead to the "cold battery sensor" mounted under the battery tray. On my GV, the leads are easily accessible coming out from under the battery tray, and on mine are colored blue and brown. The blue is the earthy one, the brown is the 'live' at around 5volt. I just used a small connector block to do the job. The circuit is "dead" at ign. off, there's no need to disconnect anything. Cut the brown lead, strip back and insert into a small connector block of the 2A. type. Fit the 33K0 resistor on the other side of the connector block so the resistor becomes in series with the brown lead.
Caution: These colors are on MY diesel GV., they MAY be different on yours! But the sensor is easy to find, just slip your hand under the battery tray.

Explanation:--
The voltage used to charge any type of lead-acid battery is crucially important even down to a few tenths of a volt.

Types of lead acid batteries:
"Wet" type: The acid is visible and can be topped up with distilled water. These were charged at 14.4volt from the alternator in the old days by a regulator either inside or outside the alternator. Wet batteries are rare on domestic cars nowadays.
"Sealed" type: Or sometimes called no-maintenance. The proper charge voltage here is anybody's guess. Some are vented, some aren't. Some only vent under pressure by blowing out a rubber plug. They work by catalyzing the hydrogen and oxygen produced under gassing back to water. Thusly the SG (specific gravity) of the acid comes back to 1.28 at full charge.
"Calcium" type: The positive lead dioxide grid is laced with about 1% of calcium. This improves the self-discharge condition markedly.
"Calcium-calcium" type. Both the positive lead dioxide grid AND the spongy lead negative plates are calcium laced, reducing the self-discharge condition even more. Both the calcium types are advised by the battery manufacturers to be charged at a higher voltage, 14.8 to 15volt is advised for calcium-calcium types, 14.5 for calcium types.

The alternator is not controlled the "old" way by a separate or included regulator. Nowadays, and certainly on Chrysler motors, the field/rotor current to the slip rings is provided by the microprocessor system, and is pulse-width-modulated to control the effective current to the rotor.

Therefore, altering the cold-battery sensor to improve the charging voltage does not make either the alternator or the charge-control system do anything it wasn't intended to do in the original design. In this design, if the sensor (which is a simple -ve. temp. coefficient resistor) goes o/c, the micro defaults to exactly 14volt. And it does, I've measured it.

It's crucially important to get the charge voltage right for the type of lead-acid battery you have fitted -- it's not "fit and forget". If you don't get the charge voltage right, the result will be a short battery life, made worse by short-trips. Add to that the parasitic battery drain, and you have the dreaded "heavy-click" no-start when you come to use the car after a few days rest.

Finally, there is a new type of lead-acid battery coming. It's a lead-carbon containing a supercapacitor built in. They are already being called "supercabatteries". It is said they are capable of thousands of charge-discharge cycle.

Leedsman.

 

Ahhh so in other words your tricking the alternator to produce a bigger output. I take it by altering this resistor you get a bigger or lower voltage.
Very neat.
I had my battery going flat when I first got the car last year until I noticed the lights still on at odd times. Yes, you guessed it I now turn off the interior light variable wheel/adjuster so now have no battery drain.

 

I was not having " lights still on at odd times" but decided to lower the overall draw on the battery for the about 70W of interior bulbs. Goggs, on mine if I deliberately override the the automatic setting and leave my interior lights on the computer switches them off at 15 minutes after I've locked up and walked away anyway.

I changed my festoons and the two 'map lights for 10W equivalent SMD [not crap LED] CAN-BUS error free versions similar to these. Mine were cheepo but they've been in nearly two years with no problems. I dropped the draw from 70+W to 10W and increased the brightness tenfold. The T10's were a pig I had to pull the holder to bits and re-solder wires direct to the T10's but they are certainly more than capable of reading by at night.

___________

Leedsman, interesting findings mate !

 

Something struck me about the way the cold-battery sensor is fitted. It is not in tight physical contact with the battery. Because the battery and its sensor are fitted under the bonnet/hood about 9" or so from the engine, soon after starting the engine will warm up and influence the sensor and charge voltage, WHILE THE BATTERY IS STILL COLD because of the long thermal inertia of the battery. Remember, it's full of lead, water and some acid, all substances with high specific heat. Getting stuck in traffic will worsen the situation, as there is no "whoosh" of outside air cooling the sensor.

Therefore, the sensor is not going to work as intended by the maker in any case, because the engine is warming it up while the battery is still cold.

Quod erat desperandum.

Leedsman.

 

I wrote [somewhere on here] on this subject a couple of years ago. I completely disregarded the cold battery sensor for more or less the same reasons as yourself - efficacy - it just makes no sense whatsoever to me to use this 'battery button' as a regulator of anything, so I looked to :

- the ability to store [battery] more
- to charge [alternator] higher
- in a shorter [minutes] amount of time

My conclusion at that time was that the alternator unit output [and associated sensors] was set at a petrol type battery needs requirement. Changing the alternator output from its current Ah of 60's and and CCA of 600's to a type 96 of 80's over 800's would send the computer into a spin and would require some level of software adjustment. My conclusion then was that this vehicle kept outside would never, regardless of battery size, be adequate for our winters unless used daily and run for at least an hour without start / stop. The best therefore we could do would be to put a battery in excess of 80's over 800's and mitigate the 'lifestyle' issue with a trickle charger or other on car supplementary charging method.

The fact that the battery button is not in contact with the battery shell merely adds to an already bad design element. I'm not sure for example if it was in surface contact it would make much difference. Certainly it could improve response times and temps. However if those response times and temps were so far out in the first place you are still in engineering terms unable to make a silk purse from a sows ear, you are merely getting an already 'wrong' result quicker and more frequently.

Using a resistor to bump the battery input 0.5 without [see above] sending the computer into a spin interests me, every small portion of volt / Ah on a short infrequent run is 'griss to the mill' and a benefit providing the battery spec can handle the input.

 

I will report on the efficiency of the mod. after appropriate field tests.

Leedsman.

 

Your work on the 'battery button sensor' ref - an 'in series' resistor deserves applause. Every man and his dog in the UK with an infrequent use diesel GV must to a greater or lesser extent has or has previously had issues with this. Your insight is the first time anyone has had a shot at fixing the 'root cause' of the problem rather than merely mitigating it with a work-around.

EDIT : 15th Feb 2016 - This ButtonMOD started by Leedsman is carried on in this post

 

Hear, hear, I second that. Thank you Leedsman and QinteQ. I look forward to your results following your field test.

In the mean time I will continue to plug in a solar trickle charger I picked up for a cheap 20 quid from my local / national electronics store and go hunting for some heat shielding material for the battery sensor in the hope that this might reflect the heat from the engine and deflect the problem.

I have over the last two years, come autumn, been removing the 'new' battery, replacing it with my fully charged spare 'old original' which I keep sealed and 'loaded' in the garage and performing a conditioning and charging cycle through the new one over a weekend when the car is not in use. So far, touch wood, it has been working well for me and I have not seen a dial sweep since.

Once again, many thanks to you both.
HH

 

More opinion for Leedsman's initiative.

I posted somewhere ages ago a question on why a cheepo £50 lead acid 'taxi' battery might be better for the UK GV CRD market rather than the then thinking that a £250 spiral replacement should be he way to go. At that time [in desperation] I bought a big S6 BOSCH and 'mullied' the battery tray etc to fit, I did consider the Odyssey 1500 but it was too salty at£350. My thinking at the time was that any replacement should be lead acid so the alternator can charge it better for short runs, in my case the BOSCH I fitted has a starting power of 3,500 watts this should be sufficient even for vehicles with an extreme cycle load, such as taxis.

The best we can do for cold starting is :

- CCA of 95+ which inevitably comes with an Ah of 95

However what we really need seems does not / can never exist, because on a short run the lower the Ah the better. The lower Ah of say 45 / 55 means the battery can [if the alternator can output it] soak up more charge in a shorter period. A fully charged top notch battery outside your house in a UK summer - start the car - no load at all on the charging system, everything turned off - put you headlights, radio, and blower on an at 2000RPM your alternator output will jump from 10+ to 30+ amps. So, in a UK winter, those like me with infrequent short runs really need a :

- CCA of 95+ with an [impossible combination of] Ah of 65

The BTS determines battery temp in order to control the charge rate via the PCM. Put simply colder = high charge, and warmer = lower charge. The 5 volts reduces resistance in ohms value as the temp goes up. Simply moving the sensor or putting a £1 computer 12v 'chipset' mini-fan on it will have the effect of maintaining the highest allowable amp input value. My / our problem as stated is short infrequent trips are not enough to keep the battery fully charged, this hard starting or a no-start condition causes chronic undercharging and a shortening via sulphated plates, low voltage as we all know can play havoc with onboard electronics, and the fuel injection and ignition systems. I always understood there were 2 general rules :

- (1) the alternator output should be a minimum of 1/4 of the battery aH, for continuous short runs however - charging the alternator output would need to be 150%[ish] of maximum load

- (2) the 1 to 25 ratio [1 horsepower energy from the engine to make 25 peak alternator amps energy]

This old Yorkshire-man's view on deep cycle wet-flooded needs to be related to newer tech. New tech such as AGM's and spirals can 'soak up' to 40% their available capacities rather than the 25% of the older tech. And there we have the nub of it .. .. a car designed for spark not compression has a diesel engine with a petrol standard battery which to me appears to be not fit for purpose in that first place, I question whether the alternator and cabling [safety] was upgraded for a diesel spec, subsequent advances in tech leading to recommendations for spiral and AGM fall down because the alternator output now no longer reflects the optimal ratio between alternator and battery capacity. To truly benefit from an AGM or Spiral the alternator output needs to be increased to facilitate the 40% that these battery types are capable of, instead we continue blindly with an alternator output incapable of charging a modern battery unless the car is run daily and for a long run.

Amps count - volts don't, does anyone know how the standard alternator can be swapped out for a high output free-wheeling [clutch] 7 groove pulley pushing 200 + amps without sending the in car diags in a spin ? Surely at worst a re-code of the EEPROM concerned will allow as much as double the amp output from the alternator. How do our Canadian cousins manage in their winters ? surely their battery-out / alternator-in combo's are different !

NOTE : Tech info is in the Chrysler workshop manual diesel powertrain supplement if needed.

 

Looking forward to results too but found that careful management of power usage has kept me going for last 18 months on same battery.