pianotuna wrote:
RLS7201 wrote:
Grover, I believe you're on the right track if your new batteries have a built in charge controller. As far as alternators not being able to fully charge house batteries, that's non-ยข. A steady charge at 14 volts for a full day of driving will fully charge lead/acid house batteries. If you are concerned about over heating you alternator with Li batteries, why not put a temperature sensor on the alternator before and after the battery change and see what happens. I see so much hype about burning out alternators but no solid evidence.
Richard
1. 14 volts will NOT fully charge a lead acid battery in a full day of driving. It is unlikely unless there is a dedicated alternator that 14 is available for the entire day.
2. Victron has a different opinion that yours on burning out an alternator.
https://www.victronenergy.com/blog/2019/10/07/careful-alternator-charging-lithium/
While I have a lot of respect for Victron two things about this test three things about this test jump out at me.
1) I have never seen with a pulley more than half the size of the crankshaft pulley, meaning that automotive alternators typically turn at more than twice as fast as the engine and therefore get better cooling than what is being demonstrated in the video.
2) I have no idea what this alternator was designed for and whether it has anything in common with the one in my coach. I would hope that Freightliner and Cummins know that when putting an alternator into a motorhome chassis it will be expected to charge both engine batteries and a bank of house batteries simultaneously and take adequate protection for this.
3) As good as Victron is I know that they are trying to sell something.
I am not trying to fully charge the house batteries anyway. I am just trying to keep them moderately charged then either plug in somewhere or run the generator if needed to top them off before a long stay. As the video points out alternators are not extremely efficient anyway and putting an additional widget in the line would further reduce that efficiency.
One of my first camping trips in the coach was boondocking and the generator failed. Since the rig was so knew I called Cummins for advice and they told me to run the engine as needed to keep the house batteries charged. Just avoid going over 12 hours total to avoid damaging the particulate filter.
I know that there are some people out there running LiFe batteries in their coach and I would like to hear about their personal experience.
