Charging the house batteries from the engine alternator

[flynbanjo]

Are there any issues charging the house batteries from the engine driven alternator?

I recently purchased 4 AGM batteries from a bus converter and they warned me about over charging the batteries if they are connected to the engine alternator.   

[TomC]

The only worry with AGM is over volting them. Make sure your alternator is set no higher than 14.1vdc. or 28.2vdc if it is a 24vdc system. You can pump in as many amps as you want with AGM since they have much less resistance then normal wet batteries. You'll love them. My last set of 2-8D's lasted 7yrs. And in that 7yrs I did nothing to them. Good Luck,TomC

[sparkplug188]

You should not have any trouble charging your house batteries from the engine alternator.  The only problem is if the house batteries become depleted, your starting batteries will also be depleted.  You will want some way to disconnect the house batteries from the starting batteries.  Use either a manual switch or an automatic charging relay.

http://www.bluesea.com/products/category/Automatic_Charging_Relays

[TomC]

Automatic relay is nice, but I like everything controlled by me. I used two of these http://www.amazon.com/Solenoid-Continuous-Isolation-4-Terminal-Insulated/dp/B005JCX8OY strapped together to effectively have 300amps continuous since the alternator on the bus is 300amp. I wired the solenoid to a on-off-on switch on my dash. One of the ons is wired through the ignition. The other on is wired to the deep cycle batteries so to be able to energize the solenoid in case the starting batteries go dead-which has happened and started the bus on the deep cycle batteries. Has been 100% reliable for over 20 years. Good Luck, TomC

[wg4t50]

My large concern is centered around the fact depends on the alternator your using.
If your using one of the origional big jobs, like on the MC7, rated at 250 Amp at 28 VDC, no problem.   BUT if you have retro fitted a small alternator such as an autombile 100 amp area, you will cook it.  They are designed as battery maintainers and not for heavy charging. Besides a 100 amp alternator usually will produce the 100 amp but drop the voltage to about 11 VDC or less while pulling the 100 amps.
Why I run my generator into the 100 amp Charger in the Xantrex inverter for an hour or more in the AM to take the big load off the engine driven alternator.
The ISM500 has a Leese Neville 160 Amp and I do not want to smoke it.
My Opinion as usual.
Dave M

[Audiomaker]

Must be different on busses... on boats we use what's called a "Dual Battery Isolator".

[eagle19952]

what they should have warned you about is that AGM batteries (when taken down to lowest state of charge) need to be completely topped off more often than not ( I plan my charging times and durations) with that in mind.
So inverter charging via my 12kw genset gets at least the first hour if I am leaving that day (a no power pole stop).
Having said that I have one battery bank that starts and serves as the house. Have had no problems with that set-up, averaging 7 years out of wet cells.(My batteries were 2+ years old when I got my coach.
Keep in mind also that my Deka wets (first set) were not any better or worse than NAPA batteries. Those being the two sets I have used. 8d'S.
I am 6 months into my first set of AGM's and will treat them the same.
I favor a combined battery bank.

[Audiomaker]

Because the title is a little vague, maybe we can tie this topic in?...

"Charging house batteries of a different voltage from the engine alternator".

One thing to consider in the overall topic is that house batteries can be specialized, more of them, and more expensive than starting batteries.

It would not be a far out question to wonder why you spend all this money on intelligent chargers (bulk, absorption, float, equalize or desulfate...etc), and then connect that same bank to a dumb ol' alternator....even running the same voltage in both banks.

I've toyed with this idea.. vehicle batt's run an inverter which powers a charger to the house batt's.  This allows regulated and rocket science charging to the house batteries from the alternator.  Of course, you could also charge different voltages (24v charger powered by 120vac inverter, powered by 12vdc switch source).  Some inverters also can be "locked out" from the ignition (won't turn on if ignition is off).

Seems like a pretty simple setup if you have separate banks.
I...without input to the contrary plan to do this, and to make it even more complicated, I plan to run an extra Automatic Generator Start from the house system back to the vehicle system.  In this case, if for some reason the vehicle batteries get low, the generator will kick on and charge those from a house powered battery charger.   House charges vehicle, vehicle charges house.

If the ignition isn't on, the smaller vehicle system inverter won't be on anyway, so you shouldn't get any nuisance generator starts unless there's a problem (like leaving your parking lights on without noticing).  When the ignition is on (and the "aux" inverter), the alternator is keeping the batt's up in both banks, but charging the house batteries the same way your inverter/charger does... with care.

In the event that your house inverter system fails, the vehicle inverter system could be manually switched on to provide power until repaired.

Humble Opinions Expressed
Sean

[Jon]

It has been common on professionally converted Prevost coaches to use the 50DN to charge both the house and chassis batteries. The voltage setting on the 50DN regulator is around 27.7 volts but can be up to 28.0

Generally the chassis uses a battery such as the Delco 1150 (4) which is a no maintenance lead acid battery, and the house uses AGM batteries. I have had that set up on 3 coaches over a 24 year span using a single 50DN and have had no issues with battery life.

However, and this is a big thing to note, when the generator is running or the coach is plugged into shore power the inverters become the battery chargers and they are three stage chargers set to the charging voltages specific to the house battery manufacturers recommendations. That means that typically, at least once a day the house AGM (or gel) batteries are getting the proper charge protocol because at the end of the day we are either plugged into power or the generator is running so we can use the AC units or other heavy electrical loads.

[flynbanjo]

Thanks everyone.  As always great advice. 

[BlakeWright]

Ample Power (amplepower.com) make a Smart Alternator Regulator.