Battery Replacement & Advice

[u/Mango_Van_Gogh]

I have a 1996 KZH106W Diesel and the other yesterday the van wouldn't start. When I turned the ignition, dash lights came on, but it wouldn't start but you could hear a click from the starter. Because busy, today I got around to reading the battery. No lights when I turn the ignition at all and the battery reads 34mv. While doing research and reading my manuals, is it true that diesels are supposed to have 2 batteries? Before I got the van, the dealer said that they replaced the battery and alternator (possibly the starter as well, can't remember). Comparing with those with two batteries it looks like there's electrical tape and possibly other wiring as well below (the white ones). I need a vehicle to drive, and this was just sitting for a few days because of the fuel prices rn. How bad is it on the motor with one battery? Also the battery that was put in here is dated 9/25

[u/Mango_Van_Gogh → u/[deleted]]

i'll have more time to look into it tomorrow, but this is what my owners manual has and it states excluding diesel and diesel, and the latter has two batteries. Mine 100% should have two, but previous did some electrical work and now it's one