Quote:
Originally Posted by Hdlaut
I don't want 800ah for my trailmanor, thanks, I was just speaking of recent experience. I no longer have the boat, but I did have a Victron Multiplus and Color Controller.
I am interested in the 230ah cells. Are you still planning to offer the full, top balanced battery with compression, heater and BM?
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I won't build another one as a shipping and sold item, but I can definitely help you construct one of your own. This is a very long post.
3 questions arise.
#1, will you want compression from both sides, or only one side? In my previous battery builds, I have put "balanced" spring assemblies on both sides. The only advantage of that practice is less movement by expanding batteries (they only shift from the centerline outwards, over the width of two cells).
In contrast, this time I plan to build with compression springs on only one side, the plate on the other side being held tight against the rods by solid nuts and washers (no springs). This reduces the cost for springs, simplifies the assembly, and eliminates the extra inch of pack width from one side (where the 2nd set of springs doesn't stick out anymore). The disadvantage is having more cell movement by the 3rd and 4th cells of the expanding pack. But the "balanced scheme" still required one end to move free in comparison to the other. I now feel that "balanced" compression springs should probably only be used in much larger battery packs, with more than 8 cells. Good compression springs cost a small fortune, and "balanced" schemes require twice as many of them.
#2, I now recommend JDB BMS. This 4S pack should have either a 200A BMS or a 250A BMS. I'll be building my own with a 250A Daly, which I already have. The BMS should not be the limiting factor on battery current, it should be limited by a fuse (preferably class-T) which can blow before the BMS detects excessive current.
#3, Although both of my battery packs have heater pads installed, I've never wanted to use them, and my "automated + manual override circuit" is extremely complicated. BMS "protects" the battery from being charged below about 38 degrees anyway. I'm now inclined to disconnect all of the "automation" and just wire the heater pads through a switch (which I will probably never use). In very cold mornings, Solar provides very little power before 9:30 AM standard time, and I have been letting BMS assure that it doesn't get into the batteries. But my batteries are internal to the TM insulation, under the dining bench. If yours will be in the somewhat more exposed "exterior" compartment, we can come up with a different scheme. Will you often face sub-freezing mornings?
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The battery face size is 174mm wide x 207.3mm tall, about 56 square inches. The total compression should start at 12 PSI, being 672 lbs. The best spring to do this, fitting 3/8" big box store threaded round tube, is here:
https://www.thespringstore.com/catal...in/category/2/ Qty = 6 costs about $48.
To spread the compression evenly over the face of the "end" battery cells< I have two strategies. The more perfect, but very heavy, is to use steel plates at both ends (insulated from the battery cases by a thin sheet of plastic.) The less effective but lighter and cheaper method is to connect each pair of compression bolts (3 horizontal pairs on each side) is to use some C-channel or square bars across a piece of plywood covering the batteries. Square bars would naturally bend less, but that property might be pretty severely compromised by cutting holes for 3/8" round tube. C channels bend quite a lot, due to the limited height of the sides. That's probably worse, although the steel can be purchased.
I'm going to try the square channel segments first (over 3/4 plywood), and see if there are obvious problems occurring across the width. If there are, then I'll be switching back to steel plates.
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Depending on your power usage, 230Ah may or may not supply a generous buffer for energy use in cloudy-day boondocks. I'm uncomfortable with "only" about 225Ah in my own current usage, but I want to do some piggy things through an upgraded Inverter. What is your expected power usage, and do you have other sources (Solar, Inverter/Generator) to fill in any gaps?