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Re: Electric Conversion log for Kahleesea

Update 5/13/2019

I got a fair bit accomplished in spite of the weather this weekend.

The smart plug has replaced the old twist lock shore power connection, and the old cable was re-headed with the new connector. I highly recommend doing this, especially if you have kids that help you. It's much easier to say "plug this in until it clicks" than "twist it like that... no the other way... you have to line up the... never mind, I'll do it." I especially like the positive feedback from the locks. When you feel it click into place, you *know* it's right.

I was able to move the waste tank over enough to make installation of the battery box a fairly straightforward task. This was considerably easier than I expected. Once the battery box is in place, I'll just have to re-strap the tank back into place. I only had to move it to install the battery box due to an unfortunately placed elbow.

I assembled the battery box in my garage completely. The batteries are in, the BMS is in, the 48-12V converter is in, and the whole system is connected and running. So far, so good. I'm not super pleased at how the wiring turned out (bending well-insulated 000 cables to your will in a tight space ain't easy), but it works. The BMS sees all 48 cells and reports that they are all good, with a maximum deviation of .2V between the highest and lowest cells. That might decrease as I go through charge cycles and the BMS adjusts each individual cell charge. Still, a .2V high-low in a group of batteries that has never been charged as a unit isn't too bad. I'll have to keep an eye on this during the next few cycles.

I think this box will be Mark I. I can already see how I can make improvements for a Mark II. I also didn't glass it very well. I guess I would call it an adequate first attempt. I've never glassed anything before and kinda fumbled my way through it. I know it's waterproof, as I left the box outside during a downpour and there was no indication of water intrusion afterwards. It sure isn't pretty, though.

I may have found a good multimeter for monitoring the current flow and power consumption over time. This would give me good, solid data on realistic power consumption while under power.

The helm plate and battery installation is on deck this week. I should be able to start that once this spate of bad weather passes. Most of the remaining work is outside work so I'll need at least OK weather to proceed.
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Last edited by Captain Canuck; 1 Week Ago at 11:10 AM.
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Re: Electric Conversion log for Kahleesea

Update 5/16/2019

I set up the batteries in the box, fully connected and wired to the BMS with cell balancing turned on. Everything was set up as I would have it on the boat - the converter was running the BMS, the BMS was managing all 48 cells in 4 batteries, etc. The only thing I didn't do was put the charger on.

I checked on it last night. Much to my chagrin, it looks like the BMS has become unstable. It reads like a heat issue. If I leave the BMS off for a few hours, then use it, it works perfectly for a few minutes, then gets fritzy, showing garbled characters, then stops responding at all. I've been going back and forth with Thunderstruck about it.

The good news is that the cells are much more balanced now. They've gone from a max variation of .2V to .07V, with an average variation of .02V, so the BMS seems to be doing it's job. We'll see if that variation levels out even more during charge/discharge cycles.

Hopefully I can get the BMS replaced quickly.
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Re: Electric Conversion log for Kahleesea

Update 5/17/2019

After many conversations with thunderstruck, I've ordered a new USB serial cable. It's possible the cable was damaged and the BMS was not. If that's the case, I'll be installing everything this weekend. If not, I'll have to wait until a new BMS comes in.

I also dug into the grounding issue with the converter. Apparently that's a feature, not a bug. I didn't know the converter I ordered wasn't an "isolated" type. Apparently "common ground" is the norm for these things, and that's OK 99% of the time. However, the BMS is *so* sensitive (voltages are detected to 3 decimal places), that even a slight variation in voltage can cause problems. The long and short of it is I'm going to have to run the BMS off of a battery or buy a fully isolated converter, which is 5x more expensive than the one I have. Since I already have batteries, I'll run the BMS off of that for now.
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