There was a test here on the forum using a PD converter (I think) on a Lifeline AGM. It performed the exact same as a flooded battery. Like Kendall stated, high voltage is needed to take advantage of those faster charge rates.
No need to be confused. Batteries in twin banks should be twins as much as possible.
Can you mix jars of various capacities? Yes, but probably not without paying some penalties in total life span of the bank. There are several members here who do this with varying success.
Can you mix old jars with new ones? Penalty as above, for the batteries are no longer "twins". They are more like fathers and sons, and the older the father the less energy capacity it will have, even if it has just been sitting around.
Can you mix chemistries? Yes, but probably not without effective and easy to use switching. There is at least one member who does this--but I don't know what his regime for use or charging are. Successful long term? That is unknown, it is more a case of "so far, so good". Doing this should probably be discouraged.
I went one step farther and my starting battery is also a "twin jar" with what I chose for my house banks.
Apocryphal reports seem to indicate that most folks with well thought out solar systems have excellent battery life spans. This appears to be even more likely for "weekend warriors" such as myself because the battery banks are (properly) maintained between trips.
Getting to 100% state of charge on a battery bank is sometimes referred to as "dancing on the needle". Getting to 97% is easy, but that last 3% is almost a religious experience. Yesterday, my 500 amp-hour four jar bank was charging at 0.2 amps. I disconnected the solar charge controller via a switch, and then turned it back on. Charging rate jumped initially to 3.4 amps, and then in under a minute fell back to about 1.2 amps. A moment or two later it was under 1 amp. Is the bank 100% fully charged? Well, 0.2 into 500 amp-hours is not much--but it is not zero either.
So in an ideal world, use identical jars in the battery banks, and maintain them with adequate solar. If you do, the battery bank may have a long life.
Kustom Koach Class C 28'5", 256 watts Unisolar, 875 amp hours in two battery banks 12 volt batteries, 2500 MSW watt inverter.
I have Four energizer Sam's club 6v batteries 18 months old
at the age of 8 months I added four 139 AmpHr cd tech AGM batteries
they are on the other side of the coach with an added 9ft run one aught welding cable
this is not the most efficient install
the solar charge is connected at the junction of the two banks
the WFCO 68100 connects to the OEM bank location and then to the AGM batteries
when charging from generator only there is a slight drop between locations
when solar is also involved the the voltage at each location is very close
about once a week I attach a vector 1093 charger to the AGM bank unplug an Anderson connector and let the vector bring the AGM to full charge where it says full
I cannot check specific gravity on the AGMs and while this is not the perfect match and perfect install I have had no know problems with the agm's almost 300 charge cycles on them, over 500 cycles on the GC's which will be replaced by this fall or before
has this hasten the demise of the 6v, I don't know, its been about 6-8weeks since. checked the sg on them, I need to do that again
btw my AGM are in a regular basement storage compartment not an rv battery compartment, I have no qualms or doubt about the valityity of the install
it works "daily full time" it is not 100% perfect, when i amp the charge rates with my digital clamp on meter, the differences between the banks is often only a couple of amps
early in the charge cycle the GC sometime take a few more amps, later in the cycle the agms are taking a few more, by the end of the cycle they are usually about equal taking only a few amps each
although I would like to reroute the welding cable run directly to the electrical bay and inverter for a better balanced discharge rate
* This post was
edited 05/02/12 11:40pm by MrWizard *
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Thanks for the info MrWizard, can I ask what size generator and what type and size converter you are using when you charge your batteries with AC? I checked my AGM's today. Last week I put them on an older battery charger I have that got them to 12.8 volts and said they were charged. Today I put them on a Sears charger I have that has a specific setting for AGM's. It indicated that at 12.8 volts they were only 80% charged! It started charging them at 14.6 volts for another couple of hours, dropping down to 13.6 volts when it went to float. I don't think my converter will be able to charge these things.
On Edit: I now see BFL13's post indicating it's a WFCO 100. I'll look it up.
Last week I put them on an older battery charger I have that got them to 12.8 volts and said they were charged. Today I put them on a Sears charger I have that has a specific setting for AGM's. It indicated that at 12.8 volts they were only 80% charged! It started charging them at 14.6 volts for another couple of hours, dropping down to 13.6 volts when it went to float.
I find that strange. Usually batteries can be fully charged at lower voltages than boost ... but just more time is required to get them there.
My AGM batteries, using only the 13.8 volt converter, eventually get to a point where the ammeter shows zero current going into them and I consider them as fully charged at that point. Right afterwards just as a check, if I start the engine so the alternator can supply 14.4 - 14.6 volts to the AGM batteries, the ammeter still shows zero current going into the batteries. This tells me that given the additional time, the batteries are still getting fully charged without use of boost voltages. I thought that's what "boost" meant ... boosting the charge rate so that charge time can be reduced.