Group 29 VS Group 27

tenbear wrote:
If it takes too long to recharge, replace your OEM converter if its a single stage, with a modern 3 - 4 stage converter.

Agreed! It is a worthwhile upgrade and good for your batteries. Here's a video showing how I did it if you are interested.

That's kind of what I'm getting at.. so many trips are fairly short. I've seen people dry camp for three days at beach and drive 40 miles home. Then proclaim their batteries are charged and park the RV for a month in a storage lot.

Don't fall into that trap. When the RV is tucked into storage, have some kind of system to monitor and keep batteries fully charged. It will be money well spent.

Also-I've noted house battery voltages (not charge current). I've seen mid 14s when initially starting cold engine, but once underhood temps get normal, I've seen 13.6-13.8 volts on house batteries. To me that is occurring at a place in charge cycle where the batteries should have the full on 14.4 volts. I do not see alternator output optimized for charging two deep cycle batteries ten feet away from the engine compartment.

tatest wrote:
Other loads are insignificant compared to 100-160 amp alternator outputs.

Not always the case.

My GMC 4X4 pickup came stock with only a puny little 65 amp alternator. When commuting from work at night in the winter, I'd often set idling bumper to bumper in cold pouring down rain with the windshield wipers, heater, headlights, and DVD player running.

I got tired of a skipping DVD player during, or a weak battery after the above ... so I upgraded to a special order 200 amp alternator for my pickup. Of course I didn't need 200 amps for the situation I described. What I did need was much higher alternator output at low engine RPMs.

Sometimes I get the impression that folks focus too much on alternator maximum output capacities. The real bonus you get with a big alternator is more output at all engine RPMs.

Whether or not the alternator is going to charge your house batteries is a matter of time/distance, not battery size. Any alternator on a Ford or Chevy van cutaway chassis is going to have the capacity to do the job, after restoring the charge from a startup, if you are running long enough. Other loads are insignificant compared to 100-160 amp alternator outputs.

I don't expect the alternator to recharge my house batteries after sitting for months, because my campsite is 15 miles from my house, barely enough run to take care of the starting battery. So I recharge, after storage, in my driveway before a trip. But most RVers travel a lot farther?

Hmmmm ... our Class C has 200 amp hours of coach batteries (two 100AH 12V Group 29 AGM) in it.

On the dash I have a voltmeter and ammeter monitoring these batteries as I travel down the road. With the coach batteries being drawn down to around 12.1 volts after camping and then driving to a new campsite, in about 5 hours the E450's Ford 130 amp alternator will have charged these AGM batteries enough such that the current going into them from the alternator - as indicated by the ammeter's detection shunt I installed in the coach batteries' main negative lead - has declined to show only around 0.1 or 0.2 amps going into the coach batteries

To me, this looks like they have then been fully charged in that time. Perhaps it's because the batteries are AGM that they appear to be charged in 5 hours, or maybe it's the low contact resistance solenoid I installed between the alternator and the coach batteries, or maybe it's the 6 gauge wiring Winnebago installed between the alternator and the coach batteries - but something is causing the batteries to show what they show.

FWIW, these two batteries are 8 years old and I keep them connected to the powered stock 13.8 volt motorhome's converter almost full time (except when the weather is real hot) whenever the RV is in storage at home between trips. The label on the batteries says to float them at 13.5 volts to 13.8 volts.

Guys I don't get that one. You're down 100+ amp hours from full, start up E450 and maybe get 30-40 amps back to batteries at best. At least that is what mine is fused at 40 amps I think. How much time would it take to get that last slow 10-20% state of charge back into batteries? Maybe on a very long day driving.... But I can't see it fully charging batteries off alternator on a more local trip 1-3 hours from home say.

Nothing to do with group 29 vs. 27. Just heads up I don't think you can trust the alternator to completely charge the batteries unless you complete a very long day of driving.

No issues with the alternator. Even with 4x Group 29 you will not have an issue.

If you are expecting a fast charge from generator you should post the converter model. Some are excellent, others very slow.

Or consider 100 watts of solar to really keep the battery in good shape.

ratfink09 wrote:
Would I have any problem with the alternator on our E-450 chassis keeping up with charging the chassis and house batteries while driving?

First off I'd go with the bigger battery.

As far as your alternator goes, it depends on the wiring to house batteries and how far you drive. In my case I've seen the solar panels work away at (charge) my batteries after driving for several hours.

My suggestion would be to find a way to maintain your batteries once you get home to ensure they're fully charged at that time, and stay fully charged. Solar, trickle charger, etc. I think a good deal of RV battery trouble comes from batteries put away in discharged state or allowed to draw down for months (parasitic loads) without maintenance.

ratfink09 wrote:
Would I have any problem with the alternator on our E-450 chassis keeping up with charging the chassis and house batteries while driving?

I don't have the Ford E-450 but I can't imagine the OEM alternator would have any problem keeping the batteries charged. It must be rated about 100A. I know my Chevy could keep the batteries charged.

Would I have any problem with the alternator on our E-450 chassis keeping up with charging the chassis and house batteries while driving?