Mixing AGM and Flooded in a Bank ?

I did one deep cycle as mentioned in that old thread, haven't done any since.

When I have two (ordered another today) I can use my 55 amper on both to stay inside the 27amp limit, and do a charging profile. I expect that will show the AGM difference in Absorption that was discussed in another recent thread with Mex explaining that.

BFL13 wrote:
LY, I did a small test of this AGM when I first got it that posted about. Must be in the archive-- I tested for voltage drop at high amp draw.

http://forums.trailerlife.com/index.cfm/fuseaction/thread/tid/29061017/srt/pa/pging/1/page/1.cfm

Thats right, I forgot about it. I now remember I was going to max out my 800 watt inverter for an ~69 amp load to compare my Aged Northstar, but never did.

Are you going to cycle that battery to 50% over ~8 hours sometime?

LY, I did a small test of this AGM when I first got it that posted about. Must be in the archive-- I tested for voltage drop at high amp draw.

http://forums.trailerlife.com/index.cfm/fuseaction/thread/tid/29061017/srt/pa/pging/1/page/1.cfm

With single 100AH battery "near full" at 12.9v,
Toaster- pulled 69 amps, voltage now 11.6v
Let battery recover, then 12.9 start-
Kettle- pulled 89a, voltage 11.2

I thought that was pretty good. You don't want to do that much draw on the battery as a practice though or it will not last long!

Notes on that say a single (much used) T-1275 perhaps 130AH, did about the same for voltage drop for comparison.

On quality vs price etc, I could not get the benefit of the quality ones in my situation, so I am going with "good enough." A full-timer would look at it differently.

Hi,

It does not matter on charging, but may cause extra gassing on the low voltage unit.

It does matter when two different batteries are paralleled and not actively being charged. The lower voltage jar may be a parasite on the high voltage battery.

BFL13 wrote:

pianotuna wrote:
Hi BFL13,

The number I'd pay the greatest attention to is the fully charged voltage. If that is identical GREAT. If it is not close well.........

Does that matter for doing 50-90s? or
Does that only matter on solar doing 75-95s? or
Does that matter only on getting to 100 and then Floating?

I am interested in seeing how BFL13's UB121000 AGM performs under his scrutiny whenever he starts cycling it deeply.

AGMS vary very widely as to price. One can get 100Ah for as low as 160$ and as high as 400$ in the lower 48.

Expecting the same performance from both, or lumping them into the same category of battery performance/ attributes, even if both are vrla agm's, is unwise in the extreme.

Even 2 very similar AGM batteries, Northstar and ODyssey, well their performance claims as to cycle life are nearly identical, their weight, their CCA, their AH capacity at the 20 hour rate are identical or nearly so.

But Odyssey says their fully charged voltage is abotut 12.86, and Northstar says 13, and My nborthstar Did indeed rest at 13.06 volts. now at 465 cycles I don't know OCV, as it never rests.

And While years is the common method of measuring longevity, there is a huge differnce when there are 300+ cycles a year, vs 35.

I have ~ 465 deep cycles on a 38 month old Northstar AGM battery whose cost was ~340$. If I were to use 'morning' voltage alone as an indicator of its health and remaining capacity, then I would say it is just fine and good as new and still going strong while breaking my arm to pat myself on the back.

What tells me other wise is the reduction in amps( with high amp charging source applied in a depleted state) and time required to reach absorption voltage, and the extended time for amps to taper to 0.5% of capacity at absorption voltage.

If I deplete 45 of the new 90AH at a rate at nearly 2x that of peukert's allotment of 4.5 , my voltage still remains above 12.2 and rebounds higher while still under a ~0.4 amp load.

The voltage metric, at least on my Northstar battery, reveals nothing. The ammeter does.

In BFL's usage, I see no issue combining batteries in parallel for temporary use for extra capacity, but I think we can all agree that hooking them all up in parallel and leaving them in parallel until failure, would just cause them to fail earlier than if the same capacity was all the same age/type.

What would be Ideal, and making the most of what one already has, can be very different things. However, Newbs reading this thread might get an idea that new and old and flooded and AGM can be combined in parallel permanently, without worry, and that is not true.

But neither will it cause a rift in the space time continum as one might be led to believe.

hedge wrote:
BFL: I'm curious what brand AGM's you have. I'd like to find some locally but don't seem to recognize any of the brands I see.

I have this one and am looking at getting a second one. It is made in China according to the box it came in. It seems to be the same one sold under various brands in the States too. UPG has a version of this same "121" on Amazon eg. If you do the conversion, wegosolar price is similar to the US price on these, which is unusual to say the least. :)

I like the people at wegosolar, who do know their stuff, so I try to buy there if it works out for price.

http://www.wegosolar.com/products.php?product=Stark-AGM-12V-Deep-Cycle-Battery-100-Amp-hour-%40-20hr-rate

pianotuna wrote:
Hi BFL13,

The number I'd pay the greatest attention to is the fully charged voltage. If that is identical GREAT. If it is not close well.........

Does that matter for doing 50-90s? or
Does that only matter on solar doing 75-95s? or
Does that matter only on getting to 100 and then Floating?

BFL: I'm curious what brand AGM's you have. I'd like to find some locally but don't seem to recognize any of the brands I see.

Hi BFL13,

The number I'd pay the greatest attention to is the fully charged voltage. If that is identical GREAT. If it is not close well.........

Thanks westend. I agree that the AGMs give you more options wrt location etc. They are not that much more expensive now it seems either around here.

The 12v 100AH one I have is about $50 more than a T-105 here. We don't have those $80 6s like you can get at Sam's/Costco or else that would change my story!

I post my various set-ups to find out if I can get away with whatever, based on what the pros here say, but also to show that everyone can get away with doing things that are supposed to be taboo in all the battery blurbs, but aren't really no-nos in real life. So what if you "only" get seven years out of a battery instead of ten? :)

Mr Wizard, that's another way. Of course with solar you can operate in the higher SOCs because you have a long time during the day to get it done at the lower amps. Another factor I forgot to mention is you still need a big enough bank so you stay above inverter alarm 11v running the big stuff.

The main thing is you can have the set-up that lets you do things your way; you are not stuck with whatever your RV came with so you can't do things.