Hi Damon,
Just returned from your neck of the woods in London, spent most of my time at traffic lights. haha. Also got funny looks from the locals with my very French Normandy mud covered 3 year old Toyota, when I parked at my clients. Note to self,...... remember to take wheelbarrow for the Parking charges next visit !!!!!
I haven't commented on your batts, as there are a lot of very wise guys here that have oodles of more brains and experience.
However, .... I thought that I would share my last 10 years of experience with used/second hand AGM's, (real ones with soaked matt plate separators) and Sealed Lead Acid, SLA.
This summer I purchased and installed over a ton of New SLA batteries, they were called marine types Ultra deep cycle.
http://www.ebay.co.uk/itm/4-X-12V-110AH-Deep-Cycle-Battery-Numax-XV31MF-Leisure-Caravan-Marine-Boat-/191830670926?hash=item2ca9ffbe4e2017 my Installation is now .... a 48v 1300ah battery system, strings of batteries with copper plate/strap inter links and main 16mm battery cables are all just about the same length.
Firstly ..... I had tested 12 of those New SLA for the last 5 years and they had all behaved very well and staying remarkably stable with at rest voltages and loading voltages. In the old photo below there are 8 up the top on test.
Up top as they only weigh 25kg each, lighter than the equivalent ah AGM's
Secondly ..... The Photo is 5 years old showing my test installation, ....... My previous used/second hand AGM's MARATHON, and those Blue ones in the Pic, forgotten there 4 letter name, were bad bad. In every day use Lasted between 1 year and 5 years, then they would no longer hold more than 12.2v after 24hrs rest period.
Most would loose a cell, either the first or the last, as the plates inside had only 6 -10mm clearance, and any buckling would have the cell rise slightly and connect with the main link bars, and that was that. And yes I took a couple apart to look see. (but folks remember there is ACID in there, in the matt separators).
The exception is those yellow POWERSAFE (Hawker Siddley) they have behaved well, five years down the line.
Those Used Second hand YUASA 6v 160ah SLA have also behaved very well over the past 5 years. The only drawback is there 6v and therefore need some careful cable connections.
Thirdly...... I got fed up with constantly monitoring those used/secondhand AGM's, but being short of large amounts of cash, found that NEW SLA cost about the same as the so called refurbished AGM's, In the Uk anyway. Hmm, this was becoming a no brainer, but what New make was the best? at the best cost? and best weight?
Fourthly......... and importantly for me, was a comment from 'Oztules' ........
"Lets be clear, there is no need for a monster battery or an expensive battery, better to use golf cart ones that will last 5 years, and replace them every 5 years.
6x220ah American batteries can be found for $200, so a 24 battery bank will only be $5000 ( you will probably get more years than that as they will rarely be discharged beyond 25%... and that should give 3000 cycles)
Stylish expensive cells ( whilst I like them very much) are not necessary to produce a better system."So hence with me going down the Leisure battery route, but I deliberately never discharge beyond 10%.
So far my testing and monitoring has revealed some interesting points, especially as I have moved down the OzInverter route, with the OzInverter back charging and the AC coupling, where the battery bank does not have to be so massive as the GTI's feed directly into the OzInverter created AC output MINI GRID so the battery bank is not being heavily drawn upon.
Damon, Just my opinions and observations on a Simple, Robust and very Cost Effective solution that suits my situation.