ron.dittmer wrote:
I just learned that our 2007 E350 chassis is equipped with a 150 amp alternator.
Ron, that's outstanding!!
Our E450 has only a 130 amp alternator on it ... I wonder what year Ford switched to 150? The more the better regarding alternator size, IMHO. I even wish we had the dual-alternator option on ours - for backup redundancy - not necessarily for amperage delivery capacity. Your 150 should be fine with your battery bank. My 130 sometimes delivers 50 amps to our coach's partially discharged 200 amp hour AGM battery bank.
I've never yet seen a knowledgeable answer in these forums backing up claims to the affect that "be careful when depending upon stock alternators to charge large RV battery banks, as you might ruin your alternator" - explaining in solid technical terms why this is something to watch out for with modern alternators. Most responses seem to be from experience or information based on what older alternators might do. The specifications for my Ford 130 amp alternator say nothing about it not being rated for continuous duty at any point along it's output versus RPM, versus ambient temperature ... performance curve.
I can't believe that modern electonically controlled/regulated alternators aren't completely protected from damaging themselves anyway, anyhow, in any ambient air temperature. After all, as far as I know from my experiences or reading about those of others, alternators can recharge a completely flat engine starting battery without burning themselves up (i.e. shorting or opening their rectification diodes or other circuitry).
You might want to check Ford's output curve for your 150 amp alternator to see what output currents it's capable of at engine idle speeds. My alternator is good for 60-70 amps when the V10 is idling, so your alternator should be good for a bit more. If you take a look at your alternator's output versus RPM curve, remember that the curve is alternator RPM - not engine RPM. The engine overdrives the alternator a higher RPM than what the engine is spinning at when idling, and this overdrive ratio may appear somewhere else than in the curve image itself.
For faster charging of our coach batteries, I sometimes idle the V10 for awhile to really dump the current into them from the alternator. I then follow up with 3-5 hours on the stock converter with the ultra-quiet little Honda generator to bring the batteries up to around 90%. When driving between campsites, the alternator is spinning so fast that the coach batteries will charge to 100% after 4-5 hours on the road. My technique only works as well as it does because AGM batteries charge just enough faster at all applied charging voltages so as to be a good match to our hit and run camping style.
