Battery Charging

[arctictraveller]

Excuse me if you covered this, but how is your alternator regulated, and where does it sense voltage from? I suspect that often times, they are reading start battery voltage, and cut way back too quickly. If it's using an internal regulator, couldn't its out put be increased with an adjustable, external regulator? I just have to think that at a 60 percent SOC, the acceptance rate of a large battery would allow a much higher charge rate, for a longer period of time than the current regulator now does. In my case, with the stock alternator, (100a? On a 5.4) often times I can drive all day, and still not fully recharge my 220Ah bank. I suspect the internal regulator if cutting back too soon, based on start battery voltage, not the house bank.

[Scalf77]

My alternator is a stock ford solution, I just ordered the higher output alternator when I bought the van. I believe the output is inline with what you would expect in a standard lead acid battery.

The two battery systems are joined together with a ACR, like many here I run the Blue Sea 7622. So when the batteries are combined the load should be seen as one load, not just the staring battery. There is of course a drop in voltage between the two systems do to long run of 2 awg cable from the starter to the house. The amount of the voltage drop difference goes down as the current drops, as expected.




Certainly an externally controlled alternator could be a choice to boost your output. If I was running a second alternator I would certainly run a Balmar external voltage regulator. I had some reservation putting one on my main alternator, although I know people have done it.


Even my shore charger that was set to 60A took six hours to charge from 50%. It only spent 40 mins in the bulk phase (max current), the rest was in the Absorption phase. I suspect setting max to 80A would decrease the time, but not by much.


-greg

[ConnieKat]

Greg,
Fascinating data collection! I was once a data analyst for the AF, but haven’t seen this degree of work since I retired. Great Job! I am currently going through some redesign on my 2005 Chevy Express SMB, and trying to decide if it makes sense to go up from 2 to 3
house batts ( if I can make room!) . Also plan to add a
solar array, which has turned into more of an issue than I expected because of the shape on my extended top. Contoller and inverter are already in, just need help in trying to intall the solar psnels correctly.
I’m limited to solar or plug in because prev. Owner had everything ( and I do mean EVERYTHING ) propane removed from the van. A reinstall would be a nightmare because of missing pipes and hosing. Bought a solar generator for extra help just in case.
Sorry, went a bit overboard on the info. What batts would you recommend, and how many?
Thanks,
ConnieKat

[boywonder]

Originally Posted by Scalf77

Alternator
And finally, I collected some data from the alternator. This is with my 2004 E350 van, I got the upsized alternator on it which I believe was 140 Amps. I use the Blue Sea 7622 Automatic Charging Relay. In the graph below you will see all the charge data and the state of the ACR. I started with the SOC at 59% and made a quick stop for dinner 15 mins into the run. I left my computer system running while it was parked to keep the everything up and recording.




As you can see the alternator doesn’t have any phases, it put outs current based on the load it has, as that load decrease the voltage goes up and the current decreases. Unfortunately, one of the problems, is that without the absorption phase, we really can’t push the last 10% back into the battery


-greg

Excellent work Greg!!


I've always been concerned that the alternator/voltage regulator would overcharge the battery on long drives since it's basically a dumb charger....it's not clear to me why the alternator cannot top up the battery on long drives....why can't the alternator charge the absorption phase?..not enough volts?


You've mentioned above that as the load decreases the current drops and the voltage increases...as expected......seems like we'd have more volts than we want.......but looking at the orange and red voltage curves they appear to remain pretty flat the whole time.

[Scalf77]

Originally Posted by boywonder

Excellent work Greg!!


why can't the alternator charge the absorption phase?..not enough volts?


You've mentioned above that as the load decreases the current drops and the voltage increases...as expected......seems like we'd have more volts than we want.......but looking at the orange and red voltage curves they appear to remain pretty flat the whole time.

It is a combination of volts and current, while the alternator flirts with the absorption voltage, it settles in around 14.2 -14.3 (Lifeline Absorption voltage is 14.4) Of course in higher temperatures it may actually meet it. The next problem is current, the typical current is higher than what you would get out of the alternator for that voltage. In Absorption we have a constant voltage with controlled current. The alternator controls current based on the voltage.

If it only charges the starting battery to 85% - 95% that is not a big deal, the car manufacturer builds that into their battery size choice. So if you just use your alternator you are only getting 85% to 95% of the capacity of your RV battery from the start.


Here is the voltage graph at a resolution for battery volts.



-greg

[Jack K]

Thanks for the education. Nothing like empirical data! Bookmarking this one for sure.