Intro and plans

[mikeking]

Hi All,

I have a Dragonfly Trimaran (28 Sport) that I've had for a few years now. I've changed a few things over the years as needed, but am looking to do a bit of a project on her to a) clean up some of the things I've probably done wrong, b) give myself a bit more capacity to play with and c) because I'm interested in this stuff. Alongside this I'm also building a compute system using OpenPlotter (Raspberry Pi, Node Red, MQTT, Grafana etc.) that is hooking into the NMEA200 data.

The boat has a lot of electronics on it (Raymarine catalogue got dropped all over it by a previous owner) and while I have a 100Ah Rolls AGM battery, no expensive things like fridges and LEDs only, I still get concerned if I have to depend on the Autopilot for overnight stretches and have issues like radios reporting low voltage, chartplotters restarting due to voltage drop when starting the outboard etc. I'm going to do some checking on consumption, but I think I'm around 6A (72W) usage on autopilot. I would like to add a fridge, and to be able to run the heating fan when it gets icy, and in the UK at the moment, it's a tad cold.

The solar was updated by me recently (Sunbeam Tough 78W and Victron 75/15), replacing the old, and failing, Sunware 64W and Fox PWM controller. I'm limited on the amount of solar I can fit on board (she's a bit of a slim thing) although I could possibly get some slim panels on the amas, but don't like the thought of routing those cables through folding mechanisms. I also have a Honda 10hp outboard that has an alternator (I think 6A). Everything runs off the one battery as weight matters on these boats.

I'm thinking of building a DIY LiFePo4 battery, something like 200Ah @12v and doing a refit of the electrics. I'm concerned that I can't get enough solar to charge that size, and from what I read the alternator on the outboard is more likely to combust than charge when low.

Alongside that, ideas on BMS systems that could be integrated into a Rasperry Pi/NodeRed system (I'm liking open source like ElectroDacus over throwing money at brands) would be welcome.

Comments, pitfalls, abuse etc. all welcome.

and thanks @Will Prowse. Your videos have been most informative.

Thanks

Mike

 

[boondox]

First thing I would do is make sure that I cut down my power consumption to the bare minimum at night.

If the battery is in OK condition you may have more of a charging problem than a storage issue. With a bigger battery you need more charging. Do you have a way of measuring the actual consumption of the system? Meaning a shunt and some sort of logger? If not, then you can at least look at the spec sheets for all your gear and come up with a rough approximation. Then you can determine how much battery you need and hence how much charging you need. And yes, I have had one of those Honda's and the alt is good for a couple/three amps continuous or it will smoke.

If the battery has lost significant capacity then it may be as simple as replacing it, either with the same battery or a LFP. LFP being a better choice for you weight-wise. But just remember that with great battery banks comes great responsibility - of charging.

 

[mikeking]

First thing I would do is make sure that I cut down my power consumption to the bare minimum at night.

If the battery is in OK condition you may have more of a charging problem than a storage issue. With a bigger battery you need more charging. Do you have a way of measuring the actual consumption of the system? Meaning a shunt and some sort of logger? If not, then you can at least look at the spec sheets for all your gear and come up with a rough approximation. Then you can determine how much battery you need and hence how much charging you need. And yes, I have had one of those Honda's and the alt is good for a couple/three amps continuous or it will smoke.

If the battery has lost significant capacity then it may be as simple as replacing it, either with the same battery or a LFP. LFP being a better choice for you weight-wise. But just remember that with great battery banks comes great responsibility - of charging.

The battery is in good condition. Always been full (failing solar panel killed the last one).

Yes I have the ability to log. I've got a Nasa monitor and shunt that gives me a good view of consumption. Overnight at anchor is pretty easy, just LED lights and intermittent heating fan. I'm less sure about overnight sailing when I will want to rely on the autopilot and have all electronics on for AIS/Radio/GPS etc.

I'll do some experiments to see what sort of draw I get with different configurations.

Thanks

 

[boondox]

With a good audit of your power usage what you need to do will become clear. You want to add some margin, for example if it is blowing and the ocean is up, Iron Mike will use more power doing his job. There is no doubt that more charging would help you out. I am normally not a fan of windmills but that might be one possibility. Laying out an extra panel when conditions permit might be another. What about a small Honda genny?