D4 2nd battery charging

Thanks for all the interest and comments. My cranking battery (with the 2nd battery completely disconnected) is sitting at 12.1v.

Tim the issue I have with the D4 seems to stem from the intelligent charging system fitted to this vehicle.
I had a National Luna Intelligent Solenoid (http://www.nationalluna.com/battery_systems.htm) fitted along with the 2nd battery. This system appears to work similar to yours i.e. it couples and de-couples the batteries depending on certain voltage situations. The NL system fitted is supposed to work with the D4 but after a few days use the 2nd battery is at a low state of charge and drains quite quickly if a fridge is connected (about 3 hours). It would seem that the D4 system picks up this 2nd battery and does not charge it fully? Your thoughts and why should your system appears to work in the D4?

I suggest that you talk to National Luna about the problem you have with their unit as it may be faulty or incorrectly installed for the D4. My voltage sensitive relay that cuts-out within seconds of the engine stopping keeps the aux battery well charged although the cranking battery runs down with too long between good top-ups.

Tim, my cranking battery is usually at 12.1 - 12.3v. I have an sc80 system in my D3. Health check of the cranking battery shows it has 770cca @ 3 years old @12.2v. My vehicle sits around a bit and I charge it with a ctek 5.0a (or 20a if in a hurry) biannually. My car never throws up messages or any such thing unless the cranking battery falls below 12v (which sometimes happens if not used for a week or so) - any bizzare messages are dealt with by 24hrs on charge and then all is good. HTH

Quote:

---

Originally Posted by Epic pooh

Tim, my cranking battery is usually at 12.1 - 12.3v. I have an sc80 system in my D3. Health check of the cranking battery shows it has 770cca @ 3 years old @12.2v. My vehicle sits around a bit and I charge it with a ctek 5.0a (or 20a if in a hurry) biannually. My car never throws up messages or any such thing unless the cranking battery falls below 12v (which sometimes happens if not used for a week or so) - any bizzare messages are dealt with by 24hrs on charge and then all is good. HTH

---

Hi Mick, I'm not sure if the V8 D3 has the same alternator as the TDV6 D4, but my battery is 3yrs old as well and has the USI160 DBS, my main battery sits around 12.7v as does the second battery.

Is 770cca a bit low?? shouldn't it be up around 900cca that the original battery is, or does the V8 have a smaller battery??

Baz.

Morning Baz ! My battery is an 850cca battery, the battery guy thinks 770 at almost 3 years is quite acceptable. My battery is only 12.5+ after a charge or a long run. I've always thought my system was a bit low but it seems to work fine. My car probably sits around a lot more than yours !

I have no idea if the alternators are the same - but my alternator is the original and is 9 years old. When running the reported voltages seem normal as far as I can tell.

All good, I have a Golf TDi as a daily drive now, so the Disco sits in the driveway and is only driven up to the shops by the missus and for trips, so will be interesting if things change, might check it Saturday to see.

Baz.

Hi Mick and mate, you need to carry out a reconditioning of your battery.

There is no way an alternator can charge and MAINTAIN a battery when the vehicle is not in regular use, and your type of use is a VERY common scenario these days.

The trick to using a battery charger is to fully charge the battery but do not remove the charger once it goes into FLOAT mode.

When a battery charger fully charges a battery, it only fully charges the amount of capacity in the battery that can actually be charged.

That may sound like double dutch but over time batteries loose capacitance and this can be caused by many factors, like not charging the battery on a regular basis, not charging it long enough to allow the battery to get to a fully charged state and so on.

You can easily end up with say a 100Ah battery with only 60% of it’s original capacity being able to be charged.

So when you charge the battery, and the charger goes into FLOAT mode, you have only charged the 60% available.

Now the trick is to leave the battery charger on, after it goes into FLOAT mode and leave it in float mode for around 8 to 10 hour. Then turn the charge off for around 12 hours.

You need to let the battery’s electrolyte settle between charges, so that when the charger is turned on again, it will virtually stir up the electrolyte.

Then repeat the charging cycle for as many times as you can, as this will help to revive the battery and in many cases will noticeably increase the battery’s usable capacity.

But this type of conditioning charging will also allow the battery to be quicker charged, while driving.

In your case Mick, there is a very good chance you will increase you CCA as well.

I just checked my cranking batt this morning. Mines sitting at 12.4v. Aux battery isolated and charged with a redarc BCDC1240 dc-dc charger. Car does a mixture of school drop offs and longer 20+km running

Thanks Tim. I normally just leave it on the 5a ctek for about 24hrs which puts it into float mode for about 16hrs. Am I better off charging the batteries individually do you think (ie disconcerting them both from the car) ? Next charge will be done in a couple of weeks and I'll do as you say disconnect the charger and reconnect half way through. Do you think there is any value to the recondition mode on a ctek (never used it) ?

Hi again Mick, there is no need to separate the batteries but if your charger has setting for different types of batteries, just set it to “AGM” or 14.4v and all the batteries connected to the charger will be safely fully charged and conditioned.