ABYC does make an exception for battery lugs which can be soldered without crimping.
The ABYC does make an exception for battery lugs provided they meet the specifications for soldering of 1.5 times wire diameter. there are lots of battery lugs sold that do not meet this criteria.It is my understanding that this exception came about because factory pre-made battery cables are often factory soldered and cheaper for some builders to use.
220.127.116.11. Solder shall not be the sole means of
mechanical connection in any circuit. If soldered, the
connection shall be so located or supported as to
minimize flexing of the conductor where the solder
changes the flexible conductor into a solid conductor.
EXCEPTION: Battery lugs with a solder contact
length of not less than 1.5 times the diameter of the
NOTE: When a stranded conductor is soldered, the
soldered portion of the conductor becomes a solid
strand conductor, and flexing can cause the
conductor to break at the end of the solder joint
unless adequate additional support is provided.
Also, ABYC is not the law, their standards are advisory only and entirely voluntary.
This is entirely true for DIY's, unless, as I mentioned above, you need insurance and your surveyor notes your connections as he deems unsafe and your insurance company won't issue coverage until said items have been repaired..
The ABYC standards are partly derived from the CFR for boat builders, which is mandatory, and partly from evidence based practices so some of what is in the ABYC standards is mandatory if you are a boat builder.
Solder can be fine but should be done properly and with a mechanical connection, then solder. A wire slice, as in Western Union, pig tail slice etc. does not satisfy the ABYC requirement of "mechanical connection" and I have personally spoken with John and asked for clarification on this question.
It is important to note that the ABYC does NOT ban the use of solder on boats. It makes suggestions about how to safely use solder on a boat and that suggestion is a mechanical connection, then solder, and then properly strain relieved. In my 35 years on and around and working on boats I can practically count on one hand the number of times I have come across "properly" soldered wire joints.
Having worked in three different boat yards, on "yachts", with a friend who is a marine surveyor and on my own boats and customers boats it has allowed me to see with a large, N=LOTS, of solder failures. On your own boat, N=1, failures might be quite rare, but as the N grows, N=500, N=3000, N= 5000. N-10,000 etc. so does the rate of failure/success between solder and crimps on boats. The failure rates I have seen for soldered connections is significantly higher than that of crimped connections, because most folks just don't know how to do it properly. When done correctly they are fine, and some folks DO know how, but that happens very, very rarely in my experience. The PO of my own boat was an EE and still made horrible and unsafe soldered joints..
Lots of electronics equipment wiring connections are soldered only.
Yes factory soldered joints are almost always fine as they are done to a standard. DIY soldered joints are most often not done to a level that can even compare to a wave soldered device.
Soldering is fine as long as you provide adequate strain relief on the wiring to prevent flexing of the soldered joint.
I would add:
If a proper mechanical connection exists, if a heat sink was used to prevent solder creep, if done correctly to prevent a cold solder joint , if the right solder was used to prevent corrosion etc.....
I have NO problem with the use of solder if done by a competent solderer. Tthe reality is that I have seen so few good soldered connections on boats that I am a touch skeptical that it happens all that often.
My real concern is for a newbie DIY to hit Rat Shack, buy a $4.99 soldering iron and begin re-wiring the boat...
Crimps for the masses are a lot easier and historically, in the marine environment, more reliable, hence the ABYC's suggestions for a mechanical connection then solder...