Thread: Discovery 4 "smart" charging system.

Hi GIL. the "Low Battery, Start Motor" message should commence once your battery voltage is below 12.2v.

BUT, with healthy batteries, you can start your motor from as low as 11.6v.

Hi Tim,
Thanks again for sharing your knowledge.
I will perform the test once the readings get to 12.2v.
This may take another week at the rate voltage is dropping.

We'll see what the battery is really like then.

I'll continue to post the results.
Regards
GIL

What “test”?

You’re ongoing posts are only confirming everything everyone else in this thread already.

Hi All,

Update on the readings:

Day 18:12.44v
Day 19:12.43v
Day 20:12.44v
Day 21:12.42v

Regards
GIL

Hi All,

Update on the readings:

Day 22:12.41v
Day 23:12.41v
Day 24:12.42v
Day 25:12.41v
Day 26:12.35v

I'm a bit surprised that the voltage has held up for the last week, but this mornings reading was a significant drop.

I'll continue taking readings til I have 4 weeks worth - 2 more days.

Then I will perform the test Drivesafe has indicated in post #70.

I'll have to do it by then anyway as I need to move the car to get my mower out and knock the heads off some daisys or we'll need a machette to get to the front door!
Regards
GIL

Hi All,

Update on the readings........


Day 27:12.34v
Day 28:12.34v

This completes a full four weeks of readings.

I then performed the test Drivesafe outlined in his post of 16th July 2020, 10:05 PM.

Unlocked and opened car: 11.76v
Ign ON and headlights ON: 11.50v
Wait 3 full minutes.
End: 11.41v
Ign OFF and headlights OFF
Wait 3 full minutes.
Final reading: 11.83v

I then started the car.
It did NOT display the "Low battery, Start Motor" message.
The cranking speed was slower than normal but it had NO PROBLEM starting.
Reading after a minute or so of running: 15.00v.

Ran the engine til the coolant gauge moved just above the lower Band on the gauge.
Car is now on my smart charger for overnight.

I'll see what it finishes up with and advise.
Probably should then post a summary of findings and what I have learnt.

Regards
GIL

Hi All,

Firstly, thank you to everyone who contributed to this thread.
A big shout out to Drivesafe for his expertise and willingness to share his knowledge.

As a summary, here is a table showing the voltage reduction over the 4 weeks of the test. Note: My battery is around 3 years old.

Battery-Long-Term-Voltage-Drop.jpg
EDIT: table didnt load 1st up. Here it is now.

What Have I learnt?
- The older style brake controllers (like my Tekonsha Prodigy) have significant current draw in their quiescent state. (10 mA)
The newer ones (like Redarc TowPro Elite) have around 1 mA.
This compares to the cars quiescent current consumption of 20 mA or less. So the shorter battery drain times I was initially concerned about can be understood.


- If you are concerned to minimise battery drain then power the brake controller from
-AUX battery
-Accessory switched power via relay.
This may require settings to be set again on power up.
-or disconnect it from power when parked.
Must remember to re-plug for the next use.
I don't really recommend this course of action.


- The Smart Battery Sensor ONLY works when the engine is running and does NOT contribute to the battery drain when parked, as I initially thought (and titled the thread accordingly).


- A battery lasts longer when charged properly. I (and others) have seen this (in the caravan installations for instance) when the charging is done by Solar Systems.



- Reconditioning a battery makes a significant change to its ability to provide its full capacity in arduous conditions.


- Drivesafe has detailed a State Of Charge (SOC) test in the thread.
This is easy to do and gives a result which could be used over the life of a battery to compare its performance as it ages.
ie. Each year or when a problem is suspected.



Where to From Here?
- I plan to connect my start battery into the vans solar system when parked up at home (essentially another battery set in the vans system). The AUX battery controller will manage the start to AUX battery connection in the car.


- Knowing the cause for the shorter time to discharge the battery I will monitor its condition more closely. Of course the solar connection will maintain its charge at home.


- I plan to perform a recondition charge every 3-6 months.


- When we are away with the van I have been connecting the AUX battery to the vans solar system anyway. I think it may be better to use the start battery connection for this. Still pondering this as there are ramifications for starting the car if problems arise with the vans batteries/system. Maybe connecting for a daytime or two each week could work.


- I will NOT be editing the cars CCF to disable the Battery Monitoring Sensor as it only works when the engine is running and will not contribute to the battery discharge when parked.

Wrapup.
I hope this extended test of the start battery discharge process has been useful. I found nothing of this detail or length when I was searching for answers prior to starting the thread.
It has reinforced the findings of a number of people who have posted in the thread and hopefully quantified them as well.
I would expect a new battery to hold voltage for a longer time and an aged battery to hold voltage for a shorter time than the tabled results here.


Thanks to all for your contributions
Warm Regards
GIL

Useful information. Thanks for sharing it.