Many Chrysler owners are perplexed when they keep getting a flat battery that won't crank the engine -- and then are told by an auto electrician there is nothing wrong! Their son/daugter's car never has this problem, and it cost one tenth the price....
Chrysler is not alone in this; even the almighty technocratic BMW is having the same problem, along with others. So what's to do here, what's up Doc?

Analysis:--
Firstly, that 'invisible' background load on the battery that is there ALL the time, even when not driven, locked up tight. That parasitic draw of current is these days getting bigger and bigger. The makers must think it's a problem because they are installing "load-shedding" software as the voltage of the battery falls gradually over time, say a week or so. The less important loads are cut off, same way as your power company sheds excessive loads -- brown outs, but worse.

But that's not all: There is another insidious problem if your battery keeps going flat. Your starter battery is not a so-called "deep discharge" type. If it is continually discharged to below around 75% of its capacity. ( this is around 12.4volt BEFORE you start cranking) it will rapidly get 'knackered' as we say in England. Meaning ruined. It only needs a very few flattening sessions to do this. Even the deep-discharge type must not be carried down below 50% of its capacity. They are both lead-acids, but the starter battery has spongy lead plates to increase the powerful starter current needed by the starter motor, i.e ampere-hours. The deep-cycle kind has hard lead, and a lot less ampere-hours, and is usually a much bigger.

One contributor, Qinteq, came up with a good idea, that of having solar cells permanently connected to the battery via the cigar-lighter socket, so that the battery is on constant charge all the time in daylight. This does work, excepting that bright sunlight is really needed all the time, considering that a third of the time, it's dark, therefore no charge. Even at this, the charge current is tiny with practical cells that can be put in the windscreen without obstructing the driver's vision, i.e. about 5watt. There could be a problem here in UK etc. with those dark dismal winter months.

I've realized that a SECOND battery is needed to ensure reliable starts even under the worst condtions. I call this the "helper" battery. In my Grand Voyager I had to put it in the passenger footwell; there is no-where else. But there is plenty room in the GV to put the front passenger seat right back. (This is a UK vehicle, the front passenger sits to the left). It is wired with proper very thick cables in parallel with the main battery, but with a battery isolator switch in the positive post. If you do this, read my disclaimer below.

The starting drill is as follows: Get into vehicle: Switch on helper batt. with isolator switch: Start engine, leave helper batt connected; Do your journey: Switch off ignition AND helper: Repeat process next time.

This means the helper is charged regularly by the alternator and will not go flat -- it can't because it's not connected to anything when vehicle is idle.

Installation:--
Knowlegeable amateurs will have no trouble with such a straightforward job. In the Grand Voyager, (UK) there is a handy chassis bolt for grounding the helper's negative underneath a bit of elbow shaped trim just above the floor, and the 12volt live lead(s) can be routed inside the door pillar (hinge side) although it's a bit fiddly. You have to remove the door/body mirror, but this easy once you've prised off the triangular black trim. The mirror's mounting bolts are easy to remove, and the electrics unplug. A vertical bit of trim must be pulled off the pillar. Of course, you will be sure that any 'shorts' to body/ground are impossible from this 12volt unfused wiring. The isolator is easy to fit on the + pole, and if you're feeling ultra professional, you can fit a solenoid-operated isolator with the solenoid connected to the ign. 'on' rail. The driver then will be immaterial to the operation. I happened to have a reel of heavy alternator cable, and I used FOUR of these together to swing the diesel. They are soft copper and easy to route. I used a big battery clip onto the regular battery.

Coincidentally, just after I'd done the job, I got talking to a man sitting in his 06 Chrysler 300 diesel outside Leeds market, and he assured me that Chrysler had fitted TWO batteries in his car as original equ. He could park his 300 for a MONTH at Leeds/Bradford airport and it would start at once, no bother. Well done Chrysler.

Disclaimer/caution:--
Because starter batteries are quite capable of setting the vehicle on fire, should there be a short-circuit, and starter circuits can't be fused, if you have ANY doubts as to your ability to do this kind of job, have an auto electrician do the job for you.

I say the above because I lost a Citroen C4 when a short in the ABS unit set the vehicle on fire, and it was a write-off. A £7,500 write-off. So I speak from experience.

Leedsman.

 

not advisable if U dont use a car for longer then 3 week pull the IOD fuse it will eliminate the battery draw completely .

 

Further pertinent facts about non-wet batteries.
Qinteq's contention that wet batteries are better than the other "sealed" batteries has scientific proof.

It all hinges on the freedom of the acid to move around in each cell. In a jelly battery or an AGM type (Absorbing Glass Mat) there is a considerable obstruction to this movement. Because the SO4 minus ion in the acid is quite a bit heavier than the H2O molecule, there is a gravity pressure over time to make the SO4 minus ion migrate to the bottom of the battery. This means that the upper part eventually has almost pure water only. Under these circumstances, the upper part cannot be charged, and therefore becomes permanently sulphated with the hard crystal form. The condition is known as "battery stratification, or acid stratification". The practical time involved in this migration is around 2 years, just about the time this 'sealed for life battery' becomes instead a 'sealed for death' battery. LOL.

If you have a wet battery on your car, a little "gassing" now and then is a GOOD thing, as it helps circulate the acid so there is no stratification, and therefore ALL of the plates come into play for charging and supplying current.

I proved the point myself with the old battery from my GV. It had a date of installation on it of 2 years ago. It was a sealed calcium battery from Halfords. I tested the ampere-hour capacity which should have been 72a.h. as it said on the case, using a 12watt lamp consuming of course, 1 amp., ensuring the discharge to be well over the 20hour rate The capacity left turned out to be LESS than 20a.h.

My previous car, a diesel Jaguar S-type still had the original wet Jaguar-battery installed from new, and at 7 years old still would crank the ice-cold diesel like billy-ho, and start almost instantaneously.

So.... taking the service life into account, a wet lead-acid costs about one fifth the price of a sealed one. You are welcome to speculate as to who is paying out and who is making the money around here...

Leedsman.