unregulated alternator charging on AGMs

[arghhh]

I just finished the upgrade and rewiring of the entire house and starting battery bank and had a few questions about the setup to give my batteries a good shot of living through the season.

Here is the background and setup of the system.

2 4D AGM batteries as the house bank 198Ah each.
1 Group 27 wet lead acid as the starting.
Inverter / charger for when I am plugged in.
120 amp unregulated OEM alternator.
Xantrex pathmaker battery combiner.
Link 20 meter to watch over it all.

The AGMs say on them to limit the voltage to 13.65 volts. The inverter / charger will sit at 13.6 when the are fully charged. The alternator on the other hand runs about 14.4 when charging. The pathmaker combines all the batteries when the voltage is about 13.2 and the high voltage disconnect is set at 14.6.

So is this alternator going to kill my new AGMs when running the engine for any period of time?
I wouldn't mind getting a new alternator with a regulator on it but would it charge my lead acid to full?
In the end do I need to replace both my alternator to regulated and start battery to AGM?

Or is there something else I am not thinking of?

Thanks guys

[sailingdog]

Yes, the alternator will fry the AGM batteries... It will eventually dry out the absorbed electrolyte...leaving the batteries very nice, if large, paperweights. Why not just add a regulator to the alternator??? In the long run, it'll be a lot cheaper than replacing the AGM batteries regularly.

I'd also recommend you change your starting battery to an AGM one, since the voltages for charging are slightly different. If you set them for the AGMs, you'll shorten the life of the wet-cell battery, or vice versa.

[arghhh]

Originally Posted by sailingdog

Yes, the alternator will fry the AGM batteries... It will eventually dry out the absorbed electrolyte...leaving the batteries very nice, if large, paperweights. Why not just add a regulator to the alternator??? In the long run, it'll be a lot cheaper than replacing the AGM batteries regularly.

I'd also recommend you change your starting battery to an AGM one, since the voltages for charging are slightly different. If you set them for the AGMs, you'll shorten the life of the wet-cell battery, or vice versa.

Well I did forget the mention the alternator is one of the internally regulated ones. It is frame grounded and there is a little stud for the 12 volt output. Do they make regulator types you can just put on the output of the alternator?

I was already planning to replace the lead acid starting when it died with an AGM to keep my sanity.

[chucklesR]

External regulator:

Balmar Max Charge Voltage Regulators

Do this Balmar's Digital Duo Charge

I would think your link 20 would be serving as a regulator ?

[JohnRPollard]

Originally Posted by arghhh

The AGMs say on them to limit the voltage to 13.65 volts.

I have never heard of an AGM limited to this charging voltage. Usually they can take as much or more than a wet cell. Gel Cell batteries are usually limited to this range of charge voltage. What brand AGM did you select?

[sailingdog]

Chuckles-

I don't believe the Link 20 has an external regulator for the alternator. Believe that is only a feature on the much more expensive Link 2000R.

Originally Posted by chucklesR

External regulator:

Balmar Max Charge Voltage Regulators

Do this Balmar's Digital Duo Charge

I would think your link 20 would be serving as a regulator ?

[arghhh]

Originally Posted by chucklesR

External regulator:

Balmar Max Charge Voltage Regulators

Do this Balmar's Digital Duo Charge

I would think your link 20 would be serving as a regulator ?

The max charge looks promising, but my alternator doesn't have all the different outputs for field voltage and such. The pathmaker combines the batteries when charging from any source on any battery so I am not sure I need the Duo Charge. My link 20 is not the regulator version, just the 2 bank battery monitor.

I have never heard of an AGM limited to this charging voltage. Usually they can take as much or more than a wet cell. Gel Cell batteries are usually limited to this range of charge voltage. What brand AGM did you select?

They are Deka equivalent I think.

[chucklesR]

Then the cheapest easiest most sure method is to dial down your alternator output to 13.6 (that's what the adjustment screw is for) and not worry about maxing your starting battery.

[JohnRPollard]

Originally Posted by arghhh

They are Deka equivalent I think.

This is what one Deka vendor says about charging their AGMs:

Important charging instructions:
* Warranty void if opened or improperly charged.
* Do not install in a sealed container.
* Constant under or overcharging will damage any battery and shorten its life. Use a good constant potential, voltage regulated charger. For 12-volt batteries, charge to at least 14.4 volts but no more than 14.6 volts at 68oF (20oC). The open circuit voltage of a fully charged 12-volt AGM battery is 12.8 volts at 68oF. As the battery charges, the building internal pressure (voltage) causes resistance to the charge. Therefore, the on-charge voltage must be higher (at least 14.2 volts) to overcome this internal pressure (voltage) during charging.

From here: Deka SeaMate' Sealed AGM Batteries

By contrast, the Deka Gel Cells have a recommended charge range of 13.8-14.1 ( http://www.eastpenn-deka.com/assets/base/0909.pdf )

[chucklesR]

Optima's can take 14.3 which is why I went with them.