That looks like the batteries that that were in the alarm system in the business I owned. Back up power when the power went out.
I was always told that battery lead was something that you didn't want to mess with. Poison fumes went melting or something like that.
Those are AGM power supply batteries (similar to deer feeder and trailer breakaway batteries, just different sizes) and the plates are separated with fiberglass matts soaked in gelled electolyte. The plate material is a calcium-fortified lead alloy like most batteries and is super-toxic to process. Theres a sticky on Boolits that explains the chemistry and bad juju, it's no joke.
I just got done shredding five years of receipts from Blue Cross/Blue Shield for all the medical procedures I've undergone since 2013. And I've been writing checks for the last two years for my fathers Assisted Living facility care. Long term medical care is expensive! Lead is cheap. Going to the e-room one time is way more expensive than saving $50-$100 on lead.
I'd find out if I could sell them to a legitimate metal recycler and use the money to buy lead from a reputable source.
Salvaged battery lead should be avoided at all costs. Since the advent of the maintenance free battery the lead content has been reduced and elements such as strontium, calcium and others have been added. Most of these elements cast very poorly, ruin a pot of good alloy they are blended with and are extremely toxic. The quantity and quality of lead from batteries is not worth the risk or the effort.
From "Linstrum" on the Boolits forum - Maintenance free/low maintenance batteries use calcium metal-doped lead to catalyze the hydrogen gas. The lead alloy used in batteries also contains a bit of antimony and arsenic to help harden and strengthen the lead. When hydrogen comes in contact with arsenic and antimony, the hydrogen reacts to form ammonia analogues called arsine and stibine, AsH3 and SbH3. In World War One the Germans experimented with these as war gases. As such they were highly effective since they are deadly in amounts too small to easily detect.
Do yourself and everyone else in the vicinity a favor and DO NOT use batteries. Severe lung damage and even death could result. Sell the batteries to a recycler and let the professionals deal with the risks.
I agree with the fellers above, don't even think about it. Some batteries have little lead and are alloyed with other chemicals and the small amount of lead one could salvage isn't worth all the trouble and danger. As an auto electrician for a large city dept of water and power, I worked with all kinds of batteries, and the only part I considered using was the posts, but removing them was more work than it was worth and they had to be thoroughly cleaned of any corrosion first...
It all comes down to looking at the cost versus the benifit. Batteries do not even come close to the tipping point, potential cost is too high. You still have at least a few good years left, don't waste them when you don't just have too!