Monthly Archives: August 2018

13 volts and a nice big crane

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Ravenswing is up and running on lithium batteries. We came back the next morning and found all four “parallel 4 packs” had balanced out to 3.28volts. Anton caught my tired typo the whole the other night; the parallel wiring of four cells of course kept the voltage in each new 400 amp hour battery at the 3.5volt level. All 16 cells had been hand-leveled at 3.28volts about four months ago, so I was happy they had not changed at all while waiting for this week. So we then proceeded with wiring them in series, to get up to a 400amp hour, 12v battery.

13.18v is pretty low, so we hooked up an old car battery charger rated at 10amps, which struggled to get the pack up to 13.31v after a couple hours. We’re ok leaving it there until the charging sources are hooked up.

There are three serial ‘jumpers’ between the four 3.5v groups. Note the one in the middle goes through a 150amp fuse; this is the first line of defense safety for a bad short circuit situation.

The previously installed 12v distribution panel matches the digital meter, and is a good at-a-glance basic tool.

But JoeS, a Bay Area Multihull veteran ocean cruiser, wants more details! Here goes, Joe…

I’m thinking of a max charge limit of 14volts (Joe does 13.8).

Lower limit discharge voltage is still up for debate. I need to read up on my CALB cells again, and ask the supplier EV.tv for their reco.

We’re installing a CellMon to monitor the voltage of each 3.5v 4-cell grouping. I’m judging that our usage and our charge pattern will be non-stressful duty for this bank, and thus it’s not necessary to monitor all 16 cells individually. I haven’t decided about installing any battery temperature sensors.

The CellMon will signal out to a loudspeaker alarm when a high or low limit has hit. I believe a second signal can be created at another voltage value, which we can send to the battery protection cutoff to shut down the power immediately. That device is planned to be the Victron BP-100. It is Bluetooth enabled and gets programmed from a phone / iPad app.

Primary battery monitoring is a Victron BMV712. This is also Bluetooth driven by an app. We mounted it at the nav / comms desk but it isn’t wired to the battery yet. Pretty sure it handles battery temp, if so we’ll get that sensor.

All three charging sources will be brought in to a common bus setup, then routed to a smaller Victron battery protector – BP65. This will be set with a lower limit than the BP100’s master cutoff, so all charging sources will be cut off from the battery before the battery gets “too full”.

The one decision not made yet is how to control the four 100watt solar panels. I’m leaning towards four separate circuits, each using a Genasun 140 Lithium profile MPPT controller. This will be the best at dealing with shade management (because the panels are in four different places around the boat). The alternative is bringing all four solar panels into a Victron MPPT controller (150/30 model I think). I like the idea of all-Victron because their stuff works well together. But does anyone know if the single controller can do differing shade per panel management well? Arlene and Glen, have you dealt with this?

Joe, the BMV712 is lithium-programmable. You tell it your ‘tank is full’ setting (e.g. 13.8v) and it does all the math from there, providing % of capacity left, and all kinds of other info. I’m excited to have it on the boat’s iPad.

All of this battery management stuff won’t happen until after the mast build journey, so we’ll stop talking batteries for now.

Early today we motored from Richmond to San Rafael Yacht Harbor. It’s not talked about much, but perfect for us with a big crane and it’s a DIY-only yard. You can’t hire them to work on your boat, but there are contractors swarming the place. And some funky toothless guys. (And gals). The yard crew is very competent with 30-45′ boats.

They swung the boat just a few feet above some late model cars – yikes!

Farrier’s design does look pretty swanky once you can get a few steps back. I love this angle…

Labor Day Yard day 1 was all about the dagger trunk. It was much more involved than I planned, as I realized hull-builder Howard had wrapped the Kevlar keel-line protection up into the trunk about three inches, and that buildup at the very bottom of the trunk was really screwing up the dagger fit. It was arm and back burning work to reach up past the foil block and rasp & shurform & grind as needed. I also had to rip out all the shims I installed during last November’s haul out. Argh for me, and at one point I wanted to punch Howard in the face. But by 7pm tonight the board goes up and down, fits snugly and the exit slot is re-epoxied. Keen followers will remember a few months back I sliced off 1.5″ from the aft edge of the board. Next time we’ll talk about the crash bumper that’s replacing that cutout. Stay tuned.

LiFePo4 batteries, at last

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What do you call the stage between bleeding edge and early adopter? I don’t know, but we spent the day there… after buying 16 lithium battery cells two years ago, their installation got started today. There’s been a lot of learning, planning and fretting for months. Anton has built electric vehicles and complex land battery systems, so we listened carefully to his practical advice and I thank him greatly for the encouragement to tackle building a lithium system from scratch. This morning he told me to wrap the lug wrench handle in electrical tape to avoid any mistaken arcing. Let’s not make any short circuits with a 400 amp hour system!

A few months back we made these straps from a sheet of copper. That took longer than expected but at least saved some $ for quality (lowest resistance) balanced power across the cells.

The battery tray was built back in Santa Rosa. Today we built out component mounting spaces around it.

After mapping out parts locations it was time to make all the custom length cables. No fancy hydraulic crimpers here; just old school compression.

Here’s a progress view as the parts go in.

You’re looking at the 16 three-volt cells that have been made in to 4 twelve volt batteries (via parallel strapping). They are resting as separate groups overnight so that the individual cells within each of the four batteries balance among each other. Tomorrow hopefully we’ll find that the four groups have very close voltages to each other (ideally about 13.2volts based on how they were stored). If not we’ll balance them manually with a charger.

Ravenswing is coming out of the water this weekend so we can trim the daggerboard exit slot at the bottom of the hull to match the new daggerboard shape. I thought we could get away with not having to adjust down there, but when the v.2 dagger was slid home last month, it didn’t make it out the bottom. Oh well. Silver lining is the opportunity to finally get some artwork on the float hulls.  Hope you like it next week.

The third dimension

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Truth be told, it’s been a very painful boat year since we broke the mast. Ravenswing sits at her dock looking long and wide, but NOT vertical. We chose a mast builder and made a purchase agreement within two months of dismasting, but the company got backed up on orders and delayed our build about nine months. I almost pulled the plug, but stayed with Composite Engineering because of the strong, fast, beautifully crafted masts on Skateaway and Round Midnight. These big ocean racing tris have had great success with their CE masts, and we expect the same. And so, on the one year anniversary of our crash, the new mast finally got started. The fiber layup is finishing now, and the resin infusion is to happen this week or next.

Back in June Keith and I went to visit CE to shake the trees a bit, and I needed to see the process given all the delays. I came away impressed with the product. These photos are “the one just before” ours; it’s actually for an America’s Cup class boom, but using the same carbon weight and braiding setup.

Here’s how they build them:

Start with an aluminum extrusion, coated in a release agent (yes, we could have just settled for an aluminum mast like this 10 months ago :). This is the one our mast will be shaped from.

The blank is placed on a very long shuttle table and run through this large stationary braider. Note the hundreds of spools (creels) of carbon and fine fiberglass (white thread)

The wad of fibers extending past the aluminum blank (mandrill) allows the builders to grab the fiber bundle and hydraulically stretch all the unidirectional carbon out very straight. That’s the key to building strong compression-resistant carbon fiber. But you also need “hoop strength”, ie bands of fibers running around the mast at 90 degrees. For you long time followers, remember we added all that hoop strength to the first mast in 2015(?) by doing the tight spiral wraps. At CE, they’ll add the hoops with the banding braider in yellow here:

Our mast is making about a dozen trips through this braider. Note that all of this is dry fabric, NOT pre-preg. They will remove the mast from the braiding area and then build an epoxy resin infusion vacuum bag around the whole thing. This will squeeze resin in around every fiber of that complex braiding. Immediately after the resin is fully infused, the infusion equipment is put aside and the whole works slides in to this 70′, multi-atmospheres pressure autoclave. The epoxy will be cured somewhere in the 200-300F range (I forget what exact temp he said).

After the baking process, the new spar is ready to have the aluminum mast mandrill pulled out. They have a huge chain-drive table for that, and apparently you say little shop prayers before a fantastic popping sound when the release gives way and the product separates from its mold.

At that point, we have an odd turn of events – CE is so understaffed right now that I’ve agreed to go work for them in September to help finish my own mast. We have to fabricate the crane, the rotation arm, the spreaders, the hounds, etc etc. Everything that makes a bare stick a sailboat mast. We figure that’s a couple of weeks.

The push is really on now to get Ravenswing ocean ready for this fall. I’ll try to get back in to frequent, shorter posts as all this work heats up.

We do have one nice thing done: shore boats. After fixing up the Portabote, we decided it didn’t cut the mustard for our uses. So thanks to Drew, we copycatted and got a Takacat 340 Sport like his. It’s a catamaran inflatable, extremely stable and with the 9.9hp, this thing rocks!

You all just heard Jimbo’s big sigh of relief. (Portabote sold)

The first video link shows the first run, and it gets amusing with the engine mounting not yet tweaked.

And we’ll sign off tonight from the other shoreboat, the SUP that at some point we’ll actually try to paddle surf. Stephane says he’ll show me what he learned from the Costa Rican teacher babe :)