It will still cash flow nicely becuase tenants will pay own heat afterward, but still, the 50% rule is a quick "acid test".

@Brent Paul The battery pack is completely different chemistry than a lead acid battery.

It’s an art, not a science so I can’t get into all the details here in one post, but I can guarantee that by the end of my three day course you will be able to tell within 4 minutes and 20 seconds whether your applicant is on the swag, the meth, the crank, the acid, the booze, the bath salts or the good stuff.

If there is no flowing water you could scrape, acid etch, and throw drylok on there for $100 in materials - easy DIY job.Note: you do have electric and plumbing there that need to be moved for proper sealing,  so you would want to have pros handle those pieces.

I remember in New Delhi they has sponges on sticks soaking, between wipes, in a bucket of what smelt like acetic acid. 

Remember inflation is like acid slowly eating away at cash making it a little less every day, so it must be actively deployed to preserve itself, via equitable gains safeguards and keeps it working 24-7 as a perfect hedge against inflation. 

If you have a pile of lead acid batteries than need maintained and replaced regularly it will be a harder sell.

Clean again to wipe off dust.I used "Zinsser Cover-Stain" primer; this stuff is thick and smells like battery acid.

It's water based and is not quite as impressive as the acid stain method.

@Mike Franco also consider acid stained concrete for durability