Here is the lower case and the 8 cells with the BMS system removed. The case is quite elegant in design and aesthetics but the solid points ended there. Sadly it lacks any solid measure for cell compression and considering the cells bulged, right where the compression was lacking, lends to credence to the cell compression bar up top actually doing its job. Mastervolt fully admitted to me, in writing, that this was a design flaw.


It is also painted steel which means it can rust and this battery case did have multiple rust spots despite no signs of salt water intrusion.


For what it is worth these prismatic cells cost me about $224.00 each, or about $1780.00 for eight of them, but that is just the bare cells. Mastervolt had to design this, engineer it, build and include a very hardy BMS which includes cell temperature monitoring probes, an excellent safety feature, communication, balancing and build the case then sell it through retail channels and warranty it with everyone along the way wanting to make a buck on it. If you want to understand why LFP is expensive look no further than nearly $1800.00 worth of LiFePO4 cells to make a 24V 160Ah battery.


Design Issues:


Do you really get your money's worth with a $10,000 factory engineered LFP battery? In the 2010-2011 vintage, with Mastervolt, I would say they had some improvements to make.


Issues:


Loose Bolts - All bolts interconnecting cells, BMS and busbars were physically loose, some less than finger tight. VERY SCARY! You also have NO ABILITY to check or re-torque them. One was so loose the basbar was physically rattling between the battery terminal and washer. Mastervolt claims to have addressed this in newer models.


Lack of Cell Compression - The manufacturer of these cells requires adequate cell compression in the form of solid end plates. The end plate design on the battery was essentially free floating for the bottom 2/3 and the cells bulged and were destroyed in the bottom 2/3 of the cell case. Mastervolt claims to have addressed this in newer models.


Over Charging - Mastervolt suggested charging these cells at 3.65V per cell back in 2010. This is MURDER if using typical CC/CV charging sources where absorption voltage is held at 3.65V per cell. This charge guidance, mixed with a CC/CV charge source with timed absorption, is likely what caused the cells to bulge and become ruined. Mastervolt has marginally addressed this in newer LFP batteries with a recommendation of approx 3.55V per cell. IMHO this voltage is still unnecessarily high and with too long an absorption could still lead to bulging and ruined cells.


Over-Discharging - You simply can not make a claim on "self discharge" based on the manufacturers bare cell rating and then stack a massive BMS directly bolted to the battery cells, with no on/off switch, and not know the quiescent draw of the BMS. This is a HUGE FAIL! This is what finally put the nail in the coffin for this battery, though based on cell bulging it had already been destroyed by over charging. It had been physically disconnected from the boat and it DID NOT survive the self discharge duration in the manual without murdering itself. Mastervolt claims to has reportedly addressed this in newer models with a way to shut down the BMS when the batteries are left idle.



Sealed Super Secret Case - The case of this battery is so super secret sealed that you can not even check for proper bolt torque. This is simply UNSAFE. I know Mastervolt probably does not want folks seeing Winston / Thundersky cells in there for $10,000 but in reality this is a simple safety issue.



Inferior Plastic - When I got this battery both lifting handles were broken and this was not from shipping. Mastervolt had no replacements as of May 2016. Mastervolt claims to have addressed this in newer models.



Painted Steel Case - Really?? Seriously?? This was is a $10,000 battery back in 2010 and the case was light gauge painted & stamped steel? It was already beginning to rust in numerous locations. Really painted steel for a marine battery..?


Self-Destructing BMS - I can understand Mastervolt's apprehension to allow folks to work on these batteries but when you fail to support a product, that is not even 5 +/- years old, with only a few hundred cycles on it and claims of 2000+ cycles, you could at least tell a qualified technician how to do it.


Mastervolt refused warranty, and yes I know it was technically out of warranty, but this battery failed due to engineering failures. Engineering failures including a very, very misleading self discharge claim, not even knowing the BMS's quiescent draw, charge voltage guidance, lack of cell compression, loose busbars etc.. If the BMS had not been "self destructing" I could have very easily balanced new cells and then reassembled this battery, in about two hours, with brand new Winston cells. This is really quite off-putting for such an expensive product.



Please Consider This Before You DIY:


I understand LiFePO4 technology was relatively new in 2010-2011, but if you think you can DIY a proper system, without adequate research, please take the time to understand that even a very good & experienced company like Mastervolt made numerous mistakes, in numerous aspects, on this LFP battery.

IMPORTANT: Today the Mastervolt LiFePO4 batteries are far better engineered and all the noted issues have been dealt with. I would have no qualms recommending a Mastervolt LFP battery. Please understand this battery was built in the very early days of LiFePO4. Yes, Mastervolt was one of the early Pioneers of LFP, and they certainly got some arrows in the back. Like any good company they learned from their mistakes and moved forward. Kudo's to Mastervolt for recognizing this and addressing it.