Re: LiFePo4 batteries: STERLING (with B2B charger) -vs- VITRON

Scott SV Tengah

Lifepo4 has been around since 1996, so I am not sure why people consider it "new technology that needs to mature", but that's besides the point.

I looked at these Sterling batteries and talked to the distributor back when I was selecting my Lifepo4 batteries in 2018. I opted for Victron for various reasons. I loathe so-called drop in solutions once I did a bit of research on these batteries. Victron is not perfect, but I like the more comprehensive thinking put into their systems. Insurance will likely be happier with a CE certified, comprehensive system designed to work together, for those of you hesitating due to that.

As to Dean's comment about the BP220 not being stout enough, I can attest to that. I didn't even need to try using the BT - the hydraulic passerrelle, which I believe is around 2000w, was enough to melt the BP220. The startup surge probably did it. We have not satisfactorily solved the hypothetical cell low voltage issue but I believe the brute force "load disconnect" option is not ideal. 

Dominique, I believe, found a solution whereby he fed the low current 24v control wires at the 24v panel through the BP220. I think that's a better solution as long as you are selective. In other words, don't load disconnect everything as many systems do. 

The nightmare scenario is that you're sailing along at night in a gale and due to the admiral (or yourself) running 5kw worth of appliances intermittently, over the last few weeks and not bothering to top balance the batteries, your batteries become unbalanced. You're at 25% SOC but one of the 24 cells in your bank has hit the low voltage cutoff limit. Your BMS cuts all power and you lose nav/lighting/autopilot. Oh and you have a leak in your engine room and your bilge pump just lost all power, too. Not ideal, imo.

An ideal solution, which is on my task list, is to use the pre-alarm output of the Victron BMS to either (1) sound an alarm and/or (2) start the generator and charge the batteries to say 80%SOC. That solves your low voltage problem vs. just cutting your loads. You can program the CELL voltage level to trigger this alarm, which will obviously be higher than the level that triggers a full disconnect.

In terms of segregating uses that may be safely disconnected, I believe I would limit it to fridges/freezers and freshwater pump. With a pre-alarm, you should know not to run your bow thruster until you charge the batteries. If you are away from the boat when the low voltage disconnect trips, I would rather not disconnect the bilge pump. Cheaper to replace some batteries than deal with the ramifications of a bilge pump that was needed, but not working.

Hope this helps.

On Fri, Aug 12, 2022 at 07:13 PM, David Vogel wrote:

2007 A54 #69
SV Tengah

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