Up front - those aren't truly deep cycle as they are a rebadge of Enersys/Odyssey "tppl" or pure-lead agm. (my gateway drug to lifepo4)
The good news - because they are pure lead, if they aren't totally shot, there is a *chance* you can recover them by yourself. I don't know if these are old discards, or purchased new or what.
They are easily killed however by owners pampering them with insufficient charge, such as from weak solar arrays and treating them like "conventional" agm's.
First up:
As a pure-lead, these NEED to have *at least* a 14.7v cv. Not 14.6 or lower. They have to "see" 14.7v cv. Those that say it just takes longer at lower cv's just don't know. When these are introduced into vehicular systems, many are incapable of providing that 14.7v cv, and degrade them. Perhaps these are out of such vehicles!
Also note, that as a pure-lead there is NO input current rush rating! They can handle it, unlike conventional agm. They can handle it! The takeaway is that you don't pussy-foot around here with low current. Unlike a conventional agm's max current input is usually .25 to .3C, this is where these START as a *minimum* required input current, otherwise you walk them down.
It is not clear if you have ever charged these *individually* before putting them into service. If not, and with insufficient charge, you can easily be unbalanced.
The thing to do is find a charge source that is hefty, and has
at least a 14.7v CV and charge individually an monitor them just in case they actually have gone to trash. But because they are pure-lead, the chance of you recovering them yourself is greater.
AT the very minimum,
set your solar charge controller's CV to 14.7v - but charge each individually, because if that voltage reading you are showing in the pics is true, you are badly out of balance. If they recover individually, you can put them back into your normal service.
Would love to know what your charging / solar setup is. And if these were used. Crossing fingers we can get these bad boys back in operation - albeit they are not truly deep cycle for our purposes, and you have a mix of old and new which is an invitation for never ending problems. Maybe, if things turn out, and your load needs are not so great, you can pair up the most like each other with each other for say two separate systems - a working bank, and a hot-standby you can swap in as the other charges.
Note: Odyssey tends to use the C/10 rate if they publish an actual ah rating at all. All I can find on these is the "RC" rating, so we can use the ballpark trick of multiplying the RC * .6 to come up with a ballpark C/20 ah rating - which so far I see would be 205 * .6 = 123ah. Pretty close to what you state as 100ah - did you find that rating somewhere? Otherwise, we can use the 123ah trick to calculate the minimum desired charge current. Which would be 123 * .3 = 36.9A. So if you have a charger, a 40A unit would be ideal for trying to bring these back. (as long as it has a 14.7v cv)
Makes me cry to see pure-leads getting abused...
