DC-DC converter: https://www.amazon.com/gp/product/B07D5QVPWK/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&th=1

Battery Mount:

https://www.ebay.com/itm/143045778375

I'm using this to measure while testing, and will leave out once it all works:

https://www.amazon.com/gp/product/B013PKYILS/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

Everything connected via XT60 plugs. I swapped the 40v side fuse for a 25amp. On the 12v side is 40 amp fuses.

I wonder if the more stable lithium power is too much where a lead acid has a dip initially under load. Or maybe the DC-DC converter has a resetting fuse and I am going over 30 amps. I think I read you can add DC-DC converters , I wonder if adding another one on would solve the issue.. but then its getting expensive.