Stop/start...regen...smart Alternator... Dc-dc Charger For Leisure Battery Or Not?

[travelvolts]

There is still much to learn about how intelligent alternator behave in varying environments. I would imagine that there would be some temp compensation. There are a good many sensors supplying the ECUs with various info and I don't see why they wouldn't also use this info to regulate the alternator for maximum efficiency at all times.

 

[Dellmassive]

here a small bit of additional data . . . .

as you may know the van was sent off to the repair center after having the side caved in, anyway all good now. but look at the Ctek battery monitor readout for both batteries over that duration.

the van was layed up for around 5 weeks with the odd start here and now. Both batteries show very poor SOC/SOH atm.

Over the xmas break i did connect the Noco GB1500 charger to each intern until it registered 100% . . . . but they seem to be dropping back down fairly quickly.

this shot shows the current SOH/SOC as of today.


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This shot shows the gradual decline in the main battery over November into December, The first large spike was them boost pack starting the van and a drive home + a few days work. The large spike near the ens is me with the charger.



A similar story here with the AUX battery, gradual decline, few short drives.. then a mains charge over xmas about 4 days ago. This Aux battery has the Redarc DC-DC charger connected to it using the ignition feed (BCM relay feed) as a trigger/turn on.



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this is the 15amp Noco GB1500 smart charger



The only thing connected to these battery's apart from the OEM setup is a 12v USB charger/power supply for USB kit.


Ill run the van properly/daily soon and expect both batteries to rise upto 80%/100% SOC/SOH

Moving forwards i might look a getting a small "50W small solar panel" to sit on the dash via a PWM/MPPT controller plugged into the dash 12v socket as a temp measure to help keep the battery topped up while parked up for extended periods 1/2/3 weeks.

was also considering the twin battery onboard EHU charger that @mmi mentioned as an option.

her are some of the BM2 datalog readouts . . .

this one shows the AUX batt flat at the repairers.

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this one shows the days after getting the van back and a day out and about. (you wont see the 15v regen highs as this battery is now connected to the Redarc DC-DC which filters out/isolates the battery from the starter/alternator.

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this one shows the GB1500 charge process over the 7hours it was connected

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this one shows today, after sitting for another 5days after being charged.... then a short trip at 10am.

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[mmi]

Just another observation to complement thread's early observations of currents in and out of the batteries.

The battery management seems to have a few different modes at the engine startup. Every now and then it starts boost charging by raising alternator output up to about 14.8 Volts shortly after engine startup. Actually, now at freezing temperatures this seems to be the norm.

Anyways, attached a picture of a nice warm day +15C, batteries at regular SOC after 8 hour standstill. Aux battery connected through factory split charge relay.

Having such a mighty alternator the voltage boosts up in about 3 seconds along the current peaking up to almost 90 Amps before saturation. Separate measurements have shown that the aux battery absorbs about the same. Actually probably slightly less into aux battery because of that being at the end of “current limiting” 10 mm2 factory installed cable.



Anyways, just proves that factory 80 Amp fuse is good/big enough for the purpose when connecting the batteries simply through a relay.

 

[travelvolts]

One more confirmation of the need for a DC-DC charger instead of a relay!

 

[mmi]

this one shows the days after getting the van back and a day out and about. (you wont see the 15v regen highs as this battery is now connected to the Redarc DC-DC which filters out/isolates the battery from the starter/alternator.

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I'm a little bit confused now. This is the aux battery voltage behind fed by Redarc DC-DC? Is the aux battery here initially fully charged? If not - I'm confused why the DC-DC charger doesn't keep the voltage up at about 14.7Volts. As it seems in the picture, the voltage, after a very short initial boost charge, just "floats" at about 13.5V (e.g. as hours 18-19 in the picture). If not fully charged, keeping the voltage at 13.5V doesn't charge a battery much, rather just maintains the charge level. Just asking ...

 

[travelvolts]

I am guessing that the battery is fully charged. As the start voltage was around 12.5/12.6 this would suggest so.

 

[Dellmassive]

we have the Redarc BCDC1240-lv (From @travelvolts)

its a Boost/Absorption/Float DC-DC charger.

The Float voltage from it is 13.3v
Charge profile A is set for 14.6v

The Aux battery was already at 12.6v at the start so the charger moved to float stage fairly quickly (as @travelvolts mentioned)

The charger disconnects from the battery every 100-seconds for 5seconds to monitor the battery SOC.

https://www.redarc.com.au/Content/Images/uploaded/Manuals/BCDC Instruction Manual.pdf






The Float voltage from it is 13.3v





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[Dellmassive]

heres today datalog from the main starter battery . . . . .

i lost the matching AUX data log for today because the logger thew a wobbly . . . (but ill get another soon)

ambient temp 4-deg C (no extra power demand ie blowers/heaters/heated windscreen/AC were switch on)



as you can see the van is doing its best to charge up the main starter battery by putting out 14.6v ....

below is the BM2 readout for the AUX battery for today (redarc dc-dc) . . . . Similar story the Redarc is trying its best to Boost/Absorb?float the battery.




and below is the Ctek readout for both batterys . . . . .

im now thinking that the Ctek units monitor the SOH as well as the SOC.., you can see its still not happy with the SOC of both.

which makes sense as they have only had about 3/4hrs charging since i got the van back (with mostly flat batterys).



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[mmi]

Interesting... I think the outdoor temp is crucial bit when interpreting the graphs. We are now down at -10C and the van seems to stay more and more at about 14.8V. Consequently the SOC of the batteries creep up. Actually it seems that even regenerative braking is disabled - it seems that it won't even kick in when the alternator momentarily takes a break. Anyways, getting back to regular routines doing longer drives next week so will get more repeats for the statistics.
I look forward to see your batteries SOC to creep up too

 

[t0mb0]

I have those CTEK gizmos, they work well to give a general impression of SOC when the battery has been at close to rest for a while. However, they are no good at all for relatively rapid changes in SOC caused by rapid charge/discharge. They will probably “catch-up” overnight as they take stock of the increased voltage at rest.

If you want acurate SOC after heavy current flow, you need something like the victron monitor which uses a shunt to monitor the current flow.

 

[travelvolts]

I would tend to agree, your Ctek thingy is throwing you a curved ball. What it is saying does not make sense according to battery voltages at beginning and end of charge.

 

[Dellmassive]

Todays data: (about an hours drive each way to and from work)

this was the Ctek readout at 1430hrs . . . .



still showing poor SOC/SOH.

This was today AUX BM2 logging readout . . . . .



as you can see even after the DC-DC has moved to float charge . . . . . once the van had been sitting for a while the battery rest voltage starts to drop to 12.3/.4volts. (so not fully charged, yet)

to get a third opinion i connected up the battery tester.

this was the AUX battery . . . .





so that reading shows a farly good battery.

and this was the starter battery readout . . . . .





again its showing a good SOH but a lower SOC,

basically i think i need a few more days for driving about at work to see iff the readings change.

as a final test i redone the Ctek readouts at the end of the day..

 

[travelvolts]

Something definitely not right with that Ctek.

 

[t0mb0]

The CTEKs could be faulty I suppose. It’s also possible the batteries are knackered, which wouldn’t be that surprising if they were sitting at empty for a while. In my experience, those CTEKs work providing the battery has been at rest for a while (assuming they’re directly hooked up to the battery with no excess resistance on the circuit).

It looks like that battery health gizmo is measuring something like max CCA and I don’t see how it could infer actual vs rated capacity from that.

 

[mmi]

Just throwing a few thoughts to keep thread alive...

I think the gizmo actually measures the voltage and extracts the SOC from that - which is pretty much ok as long as the measurement is done the same way always - after battery being at rest for a while.

Collected all the gizmo readings of the thread and plotted voltage vs. SOC - which looks quite good actually.


Another thing which can be easily measured is internal resistance. From that can be extracted an approximation of the CCA. My guess is that the SOH is just a function of this CCA (~internal resistance) vs. rated (typed in) capacity. Though not many samples here to prove that. The lowered SOH of the old battery supports my assumption though - it didn't change with charging neither did the CCA.

Based on the plot looks a bit like that the SOC of "0" at about 12.0 Volts is more just the "o" of useful capacity before entering into deep discharge (about 25-30% of real SOC).

Can you get a second/third opinion on voltage readings of the gizmo? Does the gizmo show battery's internal resistance?

 

[Dellmassive]

Nice work...
The Launch tester doesn't show the internal resistance but I believe it measures it.

The new version of the tester does show internal resistance..... but I've misplaced atm.. I'll try and find it tomoz.

 

[Hah!]

Had a very strange set of readings yesterday accross 3 AGM batteries (2 leisure, 1 starter)...



Dropped to zero across all three at +-04:30 to +- 17:00. Sitting on the drive doing nothing. It was cold, say from -3 to 6 or 7C but even so very strange. Can only assume it was the temperature since it was across all 3?

 

[Dellmassive]

Totally mad set of data from today:

Back at work and a bleary-eyed start this morning i forgot to enter the Autowatch Ghost code to disable the immobilizer . . . . so the van started and stalled as its supposed to . . . .

Now one thing I've noticed that if you restart the van again too quick after this that sometimes the van shows up a "start/stop error - disabled" . . . which can be cleared by shutting the van down, locking/unlocking the van, ignition, code, start and off you go.

today was one of those "too quick" occasions, but needing a battery charge i thought i would leave the start stop disabled for now...



within a few minutes i noticed that the starter battery volt display in the 12v socket was showing a full field 14.9v solid..... continuous.

it was like this for the whole hour or so journey.... (i kept notice of the battery temperature to make sure it wasnt over charging . . .)

but look at the Cteck readout graph . . . its climbed to 65%.. (so the 14.9v was very good for the battery charge)




below is the BM2 readout for the AUX battery (Redarc) . . . . which shows at 12.1v charge this morning . . . then the drive to/from work.... ending up at 12.6v, but bound to drop to 12.1v by the morning.




Now the next thing i discovered was that on the way back from work, the van started a DPF Regen . . . . increased RPM to 950 from 800, burning smell from DPF, start/stop disabled etc etc etc.




now what i noticed was that again the van made the alternator full field again 14.9V . . . . .constantly until the regen was complete.





after the regen . . . the voltage dropped back down to the 13.3v as expected & stop/start was re-enabled.





and also for @mmi here is a screen shot of the Redarc dropping the charge voltage to the Aux battery so it can monitor the battery voltage to determine the SOC (every 100 seconds)



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[mmi]

So you don't have any load on aux battery overnight or when the van is standing? It looks like that in the last picture in timeframes at about 0-7 and 9-15.
I also have noticed that often during the regen the voltage stays at max (mine showing 14.8V). But also noticed that it's not the case always.
So as you know when regen is taking place - if you get a chance during a regen to drive at around 40mph then so that DSG can choose either 5th, 6th or 7th, keep eye on that. I'm pretty confident that the DSG then chooses higher gear than normally, dropping usually revs down to even 1200.

 

[Dellmassive]

More data, we have now fitted a second BM2 (Bluetooth battery monitor) into the system,

so we now have a CTEK & BM2 on each battery, starter and Aux.

during the fitting the battery's were disconnected to make the system safe to work on . . . .

interestingly it looks like the "reset" has made the CTEK units a bit more responsive . . . . . . . so it looks like the CTEK monitors may like the odd reset now and again.

Here is the main CTEK screen showing both battery's today:



here is the detailed readout for the starter battery, you can see the jump is SOC just by resetting it:



here is the AUX detailed view, again you can see the jump in SOC for no apparent reason:



next here we have yesterdays starter detailed view from the BM2, (this is the newly fitted monitor), so now we can have a full 24hr daily logging on both battery's:




and next the AUX battery BM2 detailed view (DC-DC Redarc charger):



SO after a few days at work the starter battery has increased its SOC to the expected 80% and the vans energy management system is doing a good job at keeping it that way via the smart alternator and jumping from 14.9v +regenerative braking and 13.3v float voltages.

The AUX battery is still a bit strange, the Redarc goes into Float fairly quickly into a drive indicating it a good SOC, and @ 12.v full after stopping.

but the voltage seems to drop down to 12.0v by the morning. . . . the only load over night is a couple of USB chargers that are not connected to anything.

We have a Victron BMV-712 battery monitor to add into the loop, and also the to meter out the standby current to see why the 6 week old Varta EFB+ battery is dropping over night.

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