This is my first posting to the forum. I am planning out my future with a buddy for circumnavigation and living on the boat. I am going to get either a SM2k or a Beneteau 57. Batteries are a huge plan for me. I have done tons of research on what to use and what my plans are. Most likely our usage will be as much as Delos (200+ amphr daily). During the Zoom meeting there were places for questions that were not answered.
Denis - Yes Bill and Battle Born did recommend the 24v over the 12v. BUT..... the BMS used in Battle born, whether the 12v or 24v batteries, will balance the cells just fine and going with the 24v ones won't make a difference. The Battle Born rep even said that but if you weren't paying attention closely you would miss it. The BB BMS are robust and the batteries are built better than all the rest being made these days. Worth the extra expense. However, IF BB would make a 24v with more than 100 amp hr capacity, in the same size Group 31, and price it lower than 2x the 12v price, I would be highly interested in that setup. Due to the 50amp hr current size it still would take 8x of them. I would rather do the 12v ones which allow for that emergency usage.
As a thought - I also am considering if purchasing the SM2k doing a separate 12v bank purely for electronic usage and anything 12v. The Beneteau 57 has a 280amp hr bank for that and separated the 24v bank. Haven't done the calculations for that completely but would dedicate 1x solar panel for keeping that topped off (engine alternator when running also) and be able to charge cameras, flashlights, and run the depth and wind MFd's all day everyday without draining any of the main battery bank. Might be a bit over the top, but it would help. Options for extending the banks could be to put 2x extra 24v bank batteries in the aft clothes locker beside the bank or put them beside the nav station on the floor. Putting that extra pair should be fine as long as all the wires running to the unswitched distribution block from all the pairs are of equal length. That way they will all charge and discharge the same.
Solar panels - I also noticed MOST people, lets say having 3x panels, have one MPPT to charge the bank. That one MPPT is the same cost as what 3x MPPT's would be for each panel due to inputed power levels. So if you had 3x MPPTs you would have complete redundancy if one went bad. Same cost.
Starter - yes if you use 24v ones you would have to have a step down to 12v for that power.
Phillippe - Please watch on YouTube DIY with Will Prowse and he shows PLENTY of low prices LiFEPo4 12v Group 31 batteries that are taken apart and investigated. He always finds issues with them such as not producing the stated amp hrs they should, cheaply made BMS circuits, incorrect sized wires inside the batteries, and poor sodering of terminals inside. Some could melt due to high flows of amps pulled during usage due to incorrect wires and some mislabeled relays. Make your decision off your research and what you can learn from those informational videos.
I watch Ken's videos and enjoy them. I will be for sure watching his new setup and seeing how it works out. Same for Delos - most don't know and I don't think Brian mentioned it during the Zoom video but they had a 8x 12v 100amp hr setup. Not sure why but about 2 yrs into it (July 2020) they changed those out for new BB batteries and I wonder why. If aiming for higher amp hrs I get it. But I am highly interested in when his video in a month or so comes out to find out why they changed them.
I have done some minor estimations --- if you use 200 amp hrs daily, and also have 900w of solar, you will cycle (each cycle is one full discharge of a battery bank capacity) once per 3 days or so. That is a bit over 115 cycles per year living on the boat. If the LiFPo4 batteries get 4k+ cycles (85% capacity at that time) that would be 40 yrs of usage. If that is the case then spending 2-300 more per battery to get the BB ones, which are the best, seems highly worth spending that extra money rather than trying to find a steal. This is the lifeblood of the vessel and something you will use every day so why risk it. This is of course IMHO.
PS - If we all could run the AC unit or units off the bank I am sure we would. However take a look at the Gone with the Wynns website and on there they have a video explain a "soft start" modual that attaches to the ac unit and will drastically lower the amp hrs used and keep the kick start amp hrs way down. It manipulates the start up sequence to prevent the spike. This possibly if utilized would allow more usage of the AC's in a hot climate. I will be installing at least 1 if not for all three units.
Hope this helps as I am learning myself