Hi Eric,
I don't think it is an opinion after conducting about 10 years research into AGM and flooded cell recovery methods. :)
Although many applications use AGM for convenience. AGM still has a long way to go to match the longevity of flooded cell.
The drive to provide a sealed battery started with gel cells. It had electrolyte in a geled state which would not spill unless the case cracked. It was the only lead-acid battery that could function in a zero-g environment and had relaxed shipping requirements.
It was quickly discovered that if the battery was brought into the gaseous state, a bubble would form in the gel.
This effectively removed that plate area from contact with a severe capacity penalty. It is one of the reasons all gelled cells had limited voltage charging requirement. To my knowledge, I don't believe anyone manufactures them any more.
The next step in attempts to provide sealed batteries is the AGM. In this battery the separators are wetted to 97% capacity with liquid electrolyte. They were still limited to a reduced charging voltage. Unfortunately, the pressure relief valves tend to leak, resulting in cell dehydration and cell death.
So while some folks will use AGM for the reasons you cite, it has to be remembered that the advantage is offset by AGM's limited lifespan.
If cost is a factor in battery bank management flooded cell appears to be the winner.
If cost is not object, then AGM or lithium chemistry can be considered.
Don
--- In electricboats@yahoogroups.com, "Eric" <ewdysar@...> wrote:
>
> Dave,
>
> Don has some strong opinions about batteries, but I know of a number of EVs using AGM batteries (not Optima) that have hundreds of cycles at high amperage loads and deep discharges without failures or maintenance beyond charging. AGMs have an advantage over FLA in that they do not suffer as much from Peukert's Effect, allowing for a smaller rated battery bank (in Ah) to deliver that same amount of energy at rates between 1/3 to 1/2 the Ah rating (50A-75A from a 150Ah battery), or for the same size AGM battery bank to deliver close to 50% greater range compared to FLA batteries at the same high amp loads.
>
> But everyone is entitled to their own opinion. Personally, my money went towards Lithium batteries for the conversion of my 30' ketch. My second choice would be AGMs.
>
> Fair winds,
> Eric
> Marina del Rey, CA
>
> --- In electricboats@yahoogroups.com, "desulfator" <desulfator@> wrote:
> >
> > Hi David,
> >
> > Anything would be preferable to AGM.
> >
> > Most of the battery savvy folks use the large telecom batteries that have a clear case and space between the lead plates and cell wall. They have the additional advantage of an SG smapling port that can be used to bubble the cells with low pressure air. This will remix the electrolyte in the event it becomes stratified due to non-use.
> >
> > Another advantage to these large 2 volt cells are the reduced self discharge rates. It seems over time multi-cell batteries wind up with partially conductive cell walls that allow increased self discharge amperage.
> >
> > The only thing AGM batteries are good for is providing power in a Zero-G environment such as space exploration.
> >
> > Some applications trade longevity for convenience such as packaged units like emergency lighting or UPS. But the owners have to be prepared for battery replacement every few years.
> >
> > Lead-Acid flooded cell batteries will last 20-30 years if they are maintained properly and not exposed to high heat conditions.
> >
> > Don
> >
> >
> >
> > --- In electricboats@yahoogroups.com, "davidhughes_casaba" <davidhughes_casaba@> wrote:
> > >
> > > I remember the sparrow and never knew what happened. Interesting.
> > >
> > > I must admit, this is the first I have heard bad things about AGMs. What do you recommend flooded wet lead acids like Trojan or some other technology?
> > >
> > > Thanks
> > > Dave
> > >
>
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