Modeling power usage on a boat

[SV Bacchus]

Originally Posted by akprb

Was more fun to be a electricity tyrant and now even those days are gone thanks to LEDs.

Same here, the wife and kid did a take off of Seinfelds "Soup Nazi" by calling me the Power Nazi. But hey, never got below 70%, well, until the lightening strike took out all means of charging including solar. But that is another story for another day.

[newhaul]

Originally Posted by SV Bacchus

Same here, the wife and kid did a take off of Seinfelds "Soup Nazi" by calling me the Power Nazi. But hey, never got below 70%, well, until the lightening strike took out all means of charging including solar. But that is another story for another day.

that's what a spare alternator is for

[mbartosch]

Originally Posted by evm1024

I've been working on a model to calculate the power usage on boats.

...

Anyway, this model is written in perl and is not quite ready for prime time. That is a nice way to say that I just threw the code together and any structure in more or less by chance. Not my best example of coding.

It is currently set up to model FLA and LiFePO4 battery types. It has solar and an alternator for charge sources and just a general table for ships loads.

...

OF course when the code is not too much of an embarrassment to me I'll publish the code.

What factors would you like to see in the model?

That's really great! (I am an active Perl hacker myself, been there since 4.036, back in the early 90s...).

Anyway, it will be very interesting to see if your model confirms our real life findings during our 2016/2017 one year cruise.

Some data for you to crunch:

Before I designed the system I had some measurements from a one week "test vacation" with the newly bought boat. We still had the old lead acid bank on board but we were able to get the numbers for actual consumption (this is summarized in a blog post here: https://www.entropypool.de/2015/05/0...and-use-cases/ )

The numbers I got during the shakedown cruise (110 Ah/day at anchor, 250 Ah/day when sailing prolonged times) were later confirmed by the actual data we got during the cruise itself.

I designed the system to have the solar cover the "at anchor" case to 100 %. For prolonged cruising (> 24 h) I calculated we would have to run the engine for 1.5 - 2 hours a day on average. This calculation was later confirmed by actual data from the cruise.

Data from our boat:

- 400 Ah LiFePO4 bank, 12 V system
- 120 A alternator (externally regulated with a Balmar MC-614, derated to protect the coils from overheating). Observation: it starts at 100 A and then goes back to about 80 A after a few minutes (and stays there).
- 425 Wp solar, two banks with MPPT controllers; daily yield (measured during the cruise) between 0.8 and 1.8 KWh, typical yield about 1.2 - 1.4 KWh

Daily energy consumption (measured/experienced during the year)

At anchor:
100 - 120 Ah typical. Peak usage 150 Ah when recharging the portable dinghy battery bank from the solar panels (about once a week).

When sailing 24/7:
250 - 350 Ah typical

The 250 Ah are experienced in calm to moderate conditions. The 350 Ah were only seen in prolonged times of bad weather (Bft 7 - 8, nasty waves) when the autopilot had to do some real work.

Summary of "use cases" from the core/main cruising time (2016-11-09 - 2017-08-14, 279 days)

1. Ocean passage; 34 days (La Palma - Grenada)
We were trapped in 13 days of total calm with 700 nm of zero wind around us. Using the engine would have been totally pointless. We had enough water and food and hence decided to have a vacation on the ocean instead of motoring.
Hence we switched off navigation and drifted for a few days. This means that a few days of this passage were identical to the "at anchor" use case - with neutral energy balance.

Total engine hours during this passage: 52.0 h (1.52 h per day).
Propulsion/charging ratio: 100 % charging

2. Ocean passage; 21 days (Guadeloupe - Horta/Azores)
Total engine hours during this passage: 117.3
Propulsion/charging ratio: about 20 % (4 days of calm in the Horse Latitudes) propulsion, 80 % charging

3. Ocean passage; 8 days (Azores - Spain)
Total engine hours during this passage: 37.7
Propulsion/charging ratio: 15% propulsion (about one day of very low winds), 85 % charging

4. Cruising mode; most of the remaining time (216 days)
Total engine hours: 135,4
Typical was to stay at one place for 1 - 4 days. In rare cases up to 10 - 14 days.
0 days of shore power (exception: charge to 100 % before leaving for the long cruising passages)
Propulsion/charging ratio: 100 % propulsion, 0 % charging (to confirm: never used the engine to charge batteries at anchor)

SoC regime:
- SoC mostly between 30 % and 90 % during cruising. This did not require any particular attention during the "at anchor/leasure" times.
- During the passages recharging was done daily or every other day (depending on SoC).
- Passage sailing SoC policy: SoC at dawn no less than 45 %. Typical energy usage over the night (lights, nav, autopilot, fridge): about 20 - 25 %.
- When recharging with the engine, delta charge of at least 30 % or to SoC of 70 %
- During the year SoC was at 100 % some time when motoring for prolonged times, e. g. during calms on passages. During normal cruising we avoided high SoC values by making liberal use of the electric kettle and induction plate.

[billknny]

I modeled my power system using the only objective function that matters to me: DOLLARS!

Consumable costs: Diesel fuel to run genset, amortized cost of batteries.

Capital Costs: Depreciated cost of solar, and genset.

Variables: Battery size and chemistry, depth of discharge. Size of solar install. Size of battery chargers. Frequency of operation of genset.

My analysis was useful because it pointed out things I might have missed otherwise. It indicated that the lifecycle cost of Li batteries was lowest--but not by much and not worth the upfront investment when you looked at the time required for the payback.

Although low in initial battery cost, FLA came out WAY more expensive when everything was added in. Mostly because of more frequent generator time to top of the batteries to avoid sulfation.

We ended up with Firefly batteries. Most of the technical advantages of Li batteries, especially the tolerance for PSOC operation, and very high CAR, but the much smaller initial investment means I have several thousand dollars to do other things with for ten years.

[RaymondR]

Originally Posted by Singularity

If you get away from boat electronics and look at household system development you'l find more than you ever imagined. I'm not saying that anyone should want any of the data, rather that this technology is available for next to free (free software coupled with generic sensors (temp, pressure, volumes, flows, quantities, accelerations, direction, fire systems, cameras, tracking cameras)).

The boating community is only a fraction of a percent of the global community interested in these topics (modelling, efficiency, etc).

All true but!

In human affairs there are many dichotomy pairs. One of these is the "doers and havers" pair. This thread was started by a "doer" who sought our opinions on a software model for predicting the performance of DC power systems on boats.

Us "doers", as folks deeply interested in technology and consequently those most likely to come to an understanding of the underlying science and operating principles, are generally fully aware of what the professionals are turning out and it's commercial availability however we are driven to attempt to produce the same results using our own mental and physical skills.

For my part I will always encourage anyone who wishes to be a "doer" and in the process enhance their skill set and enrich their physical and metaphysical existence.

[SV Bacchus]

Originally Posted by newhaul

that's what a spare alternator is for

Believe it or not I have one! However, externally regulated with Balmar and I didn't have a spare regulator. I do now..

[newhaul]

Originally Posted by SV Bacchus

Believe it or not I have one! However, externally regulated with Balmar and I didn't have a spare regulator. I do now..

I do believe it.
Years ago I had a hotshot semi built on a gmc 1 ton chassis .the previous guy had all kinds of spares .spare water pump spare vacuum pump alternator well you get the idea . But no spare serpentine belt that drives it all . Didn't take but 2 days after I bought it to find the error of his ways. Loose vacuum loose the brakes on tractor and trailer. Gets the old heart racing :-):-)

[SV Bacchus]

Originally Posted by newhaul

Loose vacuum loose the brakes on tractor and trailer. Gets the old heart racing :-):-)

Ouch, I bet it does. My heart would have skipped a few beats..

[sailorboy1]

When my power model (the battery monitor and voltmeter) say I’m low on power, I add more

[Singularity]

Originally Posted by RaymondR

All true but!

In human affairs there are many dichotomy pairs. One of these is the "doers and havers" pair. This thread was started by a "doer" who sought our opinions on a software model for predicting the performance of DC power systems on boats.

Us "doers", as folks deeply interested in technology and consequently those most likely to come to an understanding of the underlying science and operating principles, are generally fully aware of what the professionals are turning out and it's commercial availability however we are driven to attempt to produce the same results using our own mental and physical skills.

For my part I will always encourage anyone who wishes to be a "doer" and in the process enhance their skill set and enrich their physical and metaphysical existence.

Please consider re-reading the previous posts. Also please consider getting more up-to-date on the state of the technology that other non-professional doers are operating working with. I think that I would use the word enthusiast where others would use the word doer.

[SV Bacchus]

Originally Posted by sailorboy1

When my power model (the battery monitor and voltmeter) say I’m low on power, I add more

That has been my mode of operation for the past year, works for us.

[newhaul]

My mode is I take out when the sun goes down and put in when the sun comes up.

[RaymondR]

Originally Posted by Singularity

Please consider re-reading the previous posts. Also please consider getting more up-to-date on the state of the technology that other non-professional doers are operating working with. I think that I would use the word enthusiast where others would use the word doer.

I've read every post in the thread, at my age the real problem is retention rather than attention.

What are you objecting to, the dichotomy hypothesis, the terminology - the "doers and havers" contribution to the vernacular? What's your real problem mate?