I found this and interesting read, particularly not relying on individual battery BMS when you have more than one battery in a marine set up. Maybe you find it interesting.

Outback Marine Blogs Lithium Battery BMS Installation - Australian Marine Standards

www.outbackmarine.com.au/blog/outback-marine-blogs/lithium-battery-bms-installation-a-guide-by-mark-smith/

Thanks.

I've moved up my list the need to thoroughly understand my battery setup. It's been on the list, but reading the article gives me some points to check sooner rather than later.

Understandable articles in June 2024 Practical Boat Owner (No 704 ) -practicalboatowner-lithium -

Probably a good reason to get one 200 amp hour rather than two 100 amp hours (unless you want 24 volts). Then probably leave a lead acid totally separate for the starter motor.
I was looking through battery dimensions yesterday and was rather surprised to see that the Volt-X 120ah (which I have) has exactly the same dimensions as their 190 amp hour and also 200 amp hours from certain other manufacturers- ie 345 by 245 by 190.

Manufacturers tend to use standard battery cases and therefore fit cells then packing material to fill the void.
I opened up a 200amp Volt-x battery a few years ago and found that the cells and bms only took up half the space in the case.

Try finding an electrician who understands lithium battery system set-ups can be difficult, I have built several lithium batterys inc one for my sons boat but when i set up the electrical system for my motorhome - totally offgrid, never needed to plug in, even charged up in pouring rain, I went through a few electricians until I found one who had half a clue but even then it was a bit over his head but after explaining how the whole system worked he signed off on it, My current project, 40ft cat, twin outboards - nissan leaf powered, most likely using Tesla Life-po4 cells but that may change, hopefully Battery tech gets better by the time I'm ready for batteries.

The potential increased capacity is amazing. Muller Energy, for example is selling 314ah kits at $1400, that take up the same space as my old 120ah lead acid batter that only has 60ah of usable capacity !

mullerenergy.com.au/

Not relying on a single BMS is a very good plan, especially one inside a battery and not knowing how it works or what standard it was built to. I have two 120AH Lithiums side by side in the battery compartment and each has a thermistor (temperature sensor) glued on top so I get a warning if they suddenly get hot.

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Trek said..
Not relying on a single BMS is a very good plan, especially one inside a battery and not knowing how it works or what standard it was built to. I have two 120AH Lithiums side by side in the battery compartment and each has a thermistor (temperature sensor) glued on top so I get a warning if they suddenly get hot.

Yep totally agree with taping a thermistor to the outside of a lithium battery and furthermore it must be connected to a LOUD alarm. I have a smoke detector directly above and very close as well.

There are enormous differences between the prices of seemingly similar Lithium Iron Phosphate batteries. I'm not sure I want to pay an enormous premium for a name that has been in business for three or more years versus one that is relatively new.

There is definitely an argument for paying a bit of a premium for one from a bricks and mortar store where you can take it back and plonk it on the counter and say that it doesn't do x. I have just had the experience of buying a supposed AGM battery for my car from Automotive Superstore which was definitely not AGM and they admitted as such but then gave me a hard time and dozens of emails to get my money back. I'm glad I paid by PayPal. Interestingly there is also a mob suing a YouTuber who tested a particular brand of battery at well under 80% of the claimed capacity and even fudged their website to change the warranty after the fact.

This is one of the reasons why I highlighted the RTM sale a few months back as they are very good with returns over the counter.

I recently rang Outback and queried the enormous price difference between their Gentrax batteries and their Volt-X batteries (particularly their July sale where 200ah could be had for 499) and was straight out told that Volt x had been in the market far longer and therefore commanded a premium.

To compare apples with apples one must determine whether the battery has pouch cells or prismatic cells and also have a look at the specifications and particularly the continuous discharge rate which is important to me as I wind up a heavy keel on an electric winch on my trailer sailer. I wouldn't dream of being without my new $53 DL24p capacity tester now which I would use on any new lithium battery after charging and before installation.

I'm also now of the view that an internal Bluetooth BMS which reads out individual cell voltages and facilitates top balancing is essential as the cases on these things are welded/glued shut and you have no hope of doing it yourself without destroying the case. I rather like the idea of the voltex pro see-through case range although it still doesn't really tell you the quality of the components.

I'm looking to up the capacity of mine a bit from 120 to say 200 and came across this amazing offering from Banggood which meets all my criteria but unfortunately only fits the length and width of the battery recess in my internal fibreglass liner but misses out on the height constraint by 25 millimeters. I have used Banggood probably 9 or 10 years ago for quadcopter parts and batteries for my son and they were reliable despite having a few bad reviews. There are a couple of YouTube reviews on this brand of battery (although not the exact one) which seem favorable. If the battery was 20 mm less in height I would buy the product in a flash but I would definitely pay by PayPal to protect myself in case of an argument.

au.banggood.com/Gokwh-12V-320AH-LiFePO4-Lithium-Battery-4096Wh-200A-BMS-8000+-Deep-Cycles-Built-in-bluetooth-Perfect-for-RV,Marine,Home-Energy-Storage-p-2014159.html