Hmm.. I got a DC-DC converter from powerstream (see Bleah, not enough amps for an exaplanation of why). It's rated for input range of 36-72v and output 12v at 12.5 amps. It should be sufficient for my Lectra's needs.
Unfortunately.. I hooked it up today to try and play with the lighting system and get that straightened out. Unfortunately I found the DC-DC isn't producing a steady voltage, instead it's bouncing from 8-10v pretty rapidly. Fully charged my pack is reading 70 volts (60 v nominal) so of course that's at the top end of the rated input range.
I'm beginning to get very frusterated, every DC-DC angle I try is being thwarted. Today I started thinking of an escape route through other technologies instead of DC-DC.
The purpose for DC-DC is to keep the pack balanced (rather, prevent imbalance). The simplest way to get 12v is to tap one battery in the pack. That works except that the battery you tap has greater load than the others, depletes earlier, and generally all the bad things from a misbalanced pack. The DC-DC route cures that by drawing from the entire string, converting that to the desired end voltage.
One option is to have a secondary battery, 12v, that's charged separately. Oh.. hmm.. I just had a strange thought... Because it's hard to find a 60v charger, I have two chargers, 48v and 12v. If, e.g., the battery that's charged at 12v had an extra battery connected to it, this would cure the imbalance. Aaaaahhhh... that's worth thinking over.
Another way I could have a secondary battery is these old 12v NiMH packs I have lying around.
The PowerCheq / BattEq approach is a different alternative. You'd tap one of the batteries to get the 12v system, and then trust the PowerCheq or BattEq (your preference) to keep the pack balanced.
I put a ? because maybe there's a different option.
I do kinda like the variant I just thought of above. In case it didn't make sense I'll explain what I'm thinking... the pack is made of 5 buddy-paired 12v 26AH batteries making 60v 52AH total. What I'm thinking is that I have a spare 12v18AH battery and it could be paired with one of the existing pairs. Specifically it would be paired with the one already charged by a 12v charger. It's that battery which would be tapped to drive the 12v system. The pairs would all be 12v52AH except for this one which would be 12v70AH.