Alternator Set Point

[jon_d]

Yes,

The alternator will keep the battery at 14.3V

The battery voltage will (should) only drop when the current drawn exceeds the alternator current output.
(The the engine is off, there is no alternator output, so the battery voltage will fall)

[BruceS]

Rainy day Jon, rainy day!
You just never now when you might need it!
Might even by the cost of a cruise on the Creek? lol

Ssssh! Wayne ........ he doesn't have to know how much I usually charge!!

[T1 Terry]

At 14.3v continuous the batteries will fully charge, then start to dry out. It does explain the life you got from the batteries a little better but it certainly explains the reshaping. 14v is about as high as you want for alternator voltage unless they are all short runs like taxi use or mums shopping car. That 14.3v would have a continuous current element with AGM batteries as they would be gassing at that point and recombining the hydrogen and oxygen, these involves heat as a by product so some energy is wasted as heat in the recombiners, some in plates themselves due to inefficiencies, some to create the gassing as electrolysis is quite energy intensive, so quite a bit of electrical energy is converted to heat energy so the alternator would continue to provide that wasted electrical energy..... and unless there was adequate cooling that heat continues building up till the electrolyte boils. The pressure combined with the heat softened plastic case produces the pregnant battery look that Jon showed us on another thread.

T1 Terry

[Mrcoolabah1au]

heaps

[Jon and Kay]

Thanks Terry.
The SBI12 smart relay has a manual override switch to allow the alternator to be disconnected (from the dash) during long drives. It also drives the majority of loads to the vehicle including aircon, wipers, lights and fridge. Not much current left over for batteries, although it would help hold batteries at higher than float voltage should I leave camp fully charged (which rarely if ever happens as I don't use caravan parks, i.e. never on power.)
That said, I have had the need over the last few months to clean up a property I purchased, and sitting on power with the Xantrex inverter/charger on float at 13.8 (as per battery specs) most likely caused that battery to fail. In hindsight....I should have lowered the float to 13.3 during that time both on the Xantrex and PL40. Still, 5 years + for everyday use of 150ah+ gives me about 2000 cycles at 30% DOD, and the occasional complete accidental discharge is fair enough for AGMs. I also noted when disconnecting the battery pack that there was some build up occurring on the terminal ends. Some maintenance procedure should have been carried out during the last five years to wire brush the terminal ends and add some protective paste before reconnecting. We learn, but will my practices change on the next set?
The alternator is a strange beast when t comes to charging non-vehicle battery. Why don't we add a controller (like PL40/60) between the alternator and battery, hence controlling charging as with other sources?

[T1 Terry]

Thanks Terry.
The alternator is a strange beast when t comes to charging non-vehicle battery. Why don't we add a controller (like PL40/60) between the alternator and battery, hence controlling charging as with other sources?

This is where the DC to DC charger comes into play, they have staged charging and good ones has a method of switching them off/on again when required. We utilise this feature for the Li batteries so the secondary control unit can stop the charging for a period of time if a high cell is detected, then resumes charging and watches for another high cell alarm.

T1 Terry