Why do battery threads get so granular?

[Cthoops]

I'm not asking this to be snarky - I am truly curious. Why do the battery threads on here turn into double-digit pages with discussion of shunt this, percentage that, float here, 1% there?

We have a mental block when it comes to the subject of electricity, so in recognition of that fact we installed two Firefly batteries two years ago before we left to go cruising full-time. We also installed a Balmar battery monitor. With the exception of pushing the button on the Balmar a few times a week to check the capacity percentage, we have ignored the batteries since installation. In fact, the Balmar died last month and we decided not to bother replacing it.

We charge the Firefly's with two Renogy 100 watt semi-flexible solar panels, each hooked up to their own Genasun solar controller. They are also charged when we are motoring by a 70 amp alternator on our Beta (which was an upgrade from the 40 amp stock alternator). This set up has proven more than sufficient for us.

Now before everyone starts telling me we're doing it wrong and "we're gonna die", I will say that we have minimal power loads on our boat. The biggest draw is charging our electrical gadgets and our Engel refrigerator. We have LED bulbs for every light (both exterior and interior), an alcohol stove and no pressure water (so no minimal draw for a propane/LPG stove or when we are using water), and your standard chartplotter/transducer/VHF.

Realize that I am NOT saying that everyone else is doing it wrong. I'm just wondering if the extra attention that is being paid by people on these battery threads is due to a larger boat? More electrical needs? A general interest in the subject? I truly would like to know because I find it rather perplexing.

Thanks.

[sailorboy1]

Its a sport. Kind of like Hunter bashing.

[Cthoops]

Originally Posted by sailorboy1

Its a sport. Kind of like Hunter bashing.

That’s what I’m starting to suspect.

[kmacdonald]

It's the gospel to some.

[a64pilot]

If the biggest electrical load I had was an Engle used as a fridge and I could get by with just two batteries, then I wouldn’t worry about it either.
Yes we could live that way, in fact we could live with no electricity at all, or a motor for that matter.
But we choose not to.

When you start talking about $2K or $3K or more for a battery bank, then it behooves you to try to make it last.

But it’s not hard really, the discussion always really surrounds when a battery is completely charged, for many they are certain it’s when their monitor says it is, or when the charge source drops to float, but it’s as simple as watching charge acceptance rate.

[AndyEss]

I suspect some of it is that many cruisers/off grid users are switching to LFP batteries. These have somewhat different characteristics than lead-acid batteries (and all their variations. LFP batteries also have a high initial cost, which makes economic sense if you treat them right to get all their promised life span - and thus lower per cycle costs.
As LFP matures and systems integration becomes easy, users will find other topics to become “experts” on to keep life interesting.

[Bycrick]

A64 is right when he states that after spending several thousands of dollars on batteries, one would like not to kill them too quickly.

But I’d suspect there are a couple of psychological factors here also.

I have to justify spending $x on batteries. After I have, I’m far less likely to believe that I was a dummy and made the wrong decision. So I have to believe that I was right.

There’s also a trend to think that increased display precision is the same thing as increased accuracy. Not true.
1. A $3 Chinese thermometer reads 79.2 degrees. Really?
2. A GPS displays latitude to 3 decimal digits of a minute. 1/1000 minute is about 6’. The specified GPS accuracy without augmentation is about 15 meters, or +-8 in the low order digit.
3. A digital volt meter displays 12.5 volts when the meter accuracy is +/- 1% +/- 2-5 counts. So it might really be anywhere from about 12.1 to 12.9 volts.
4. A battery monitor displays "state of charge" but only estimates things like Puekert's coefficient, temperature, actual battery capacity, etc. Then displays this to 1%.

But again, after I’ve spent a bunch of money on measuring equipment, I really, really want to believe that it’s right. If I believe it’s right, I really want to think that I understand what it really means.

[Chotu]

It’s also a throwback from pre-solar.

We had to pay a lot more attention when the banks were drained all the rule and the alternator put the energy back.

[Wotname]

Originally Posted by Bycrick

A64 is right when he states that after spending several thousands of dollars on batteries, one would like not to kill them too quickly.

But I’d suspect there are a couple of psychological factors here also.

I have to justify spending $x on batteries. After I have, I’m far less likely to believe that I was a dummy and made the wrong decision. So I have to believe that I was right.

There’s also a trend to think that increased display precision is the same thing as increased accuracy. Not true.
1. A $3 Chinese thermometer reads 79.2 degrees. Really?
2. A GPS displays latitude to 3 decimal digits of a minute. 1/1000 minute is about 6’. The specified GPS accuracy without augmentation is about 15 meters, or +-8 in the low order digit.
3. A digital volt meter displays 12.5 volts when the meter accuracy is +/- 1% +/- 2-5 counts. So it might really be anywhere from about 12.1 to 12.9 volts.
4. A battery monitor displays "state of charge" but only estimates things like Puekert's coefficient, temperature, actual battery capacity, etc. Then displays this to 1%.

But again, after I’ve spent a bunch of money on measuring equipment, I really, really want to believe that it’s right. If I believe it’s right, I really want to think that I understand what it really means.

All of this plus there is group of folk who don't really understand electricity or battery technology yet are happy to repeat stuff they firmly believe to be true or fail to recognise they 'don't know what they don't know'.

Add to that, a lack of reading skills and zero comprehension ability

[Stu Jackson]

The basic understanding of how batteries get charged is often lost to altogether too many. People think float means full. People think their solar gets their house bank full by 1000.

Few understand the basic concept of battery acceptance.

Many people think battery monitors are like fuel gauges, and don't understand how to properly program and use them. Then folks buy Smart Gauges and think the simpler thing that gives them a simpler readout of SOC / SOH by doing it all "under the hood" without ever explaining how it works, is the "answer."

Many of us have written a lot about this subject.

Some choose to learn, others don't.

Wish I had a buck for everyone who started a thread with: "I don't know anything about electricity" after they've bought a boat bigger than 22 feet.

Some of us keep trying.

And none of us was born an electrician. That's why they write BOOKS about this subject. Some just choose to use forums. Maybe that's the answer to the OP's question: those of us who know and care keep trying to help.

a64 is right: "But it’s not hard really, the discussion always really surrounds when a battery is completely charged, for many they are certain it’s when their monitor says it is, or when the charge source drops to float, but it’s as simple as watching charge acceptance rate." Correct, but I'd add: "...at bulk or absorption voltage."

[sailorboy1]

I gave away a pair of 46 month old cruised on T105 golf cart batteries yesterday. Their matching pair bit it 4 months ago. The guy who came and got them said his batteries last 10 years. So I can not comment anymore on batteries as i must not really know or understand batteries at all.

[RaymondR]

I found that after I quickly killed a number of fairly expensive quality batteries and suffered the consequent wallet shock, battery management became a fascinating subject. I suspect this may be a common experience.

[UFO]

Originally Posted by Stu Jackson

The basic understanding of how batteries get charged is often lost to altogether too many. People think float means full. People think their solar gets their house bank full by 1000.

Few understand the basic concept of battery acceptance.

Many people think battery monitors are like fuel gauges, and don't understand how to properly program and use them. Then folks buy Smart Gauges and think the simpler thing that gives them a simpler readout of SOC / SOH by doing it all "under the hood" without ever explaining how it works, is the "answer."

Many of us have written a lot about this subject.

Some choose to learn, others don't.

Wish I had a buck for everyone who started a thread with: "I don't know anything about electricity" after they've bought a boat bigger than 22 feet.

Some of us keep trying.

And none of us was born an electrician. That's why they write BOOKS about this subject. Some just choose to use forums. Maybe that's the answer to the OP's question: those of us who know and care keep trying to help.

a64 is right: "But it’s not hard really, the discussion always really surrounds when a battery is completely charged, for many they are certain it’s when their monitor says it is, or when the charge source drops to float, but it’s as simple as watching charge acceptance rate." Correct, but I'd add: "...at bulk or absorption voltage."

Any book(s) you can recommend for someone with a limited knowledge?

[Jammer]

Originally Posted by Cthoops

I'm not asking this to be snarky - I am truly curious. Why do the battery threads on here turn into double-digit pages with discussion of shunt this, percentage that, float here, 1% there?

I would agree that there are some psychosocial factors at work in these threads, and that electricity is poorly understood by many participants.


But the real problem is that many boats have marginal power generating capacity for the size of the loads in use. Yours does not, because the loads you have are small, and perhaps because you motor regularly, and are in an area where the sun shines daily.


The presence of a watermaker, use of electricity for cooking, larger or less efficient refrigerators, are among the loads that drive people towards more complex systems.


Individuals whose cruising grounds are in the higher latitudes, during spring and fall when there are fewer hours of daylight, or in areas like the PNW that have cloudy weather, will have less output from their solar panels. This is especially true in cold weather where an Espar or similar space heater is used, as these require electrical power for controls and fans (or pumps as the case may be), even though they burn diesel for heat.



Unlike most land-based installations it is not always possible to install as many solar panels on a boat as one might like to have, particularly on monos, and particularly where there is a desire to limit windage.

[tkeithlu]

Yes, it's easy to detect cognitive dissonance at work in lengthy electrical posts. Yes, the forum has a number of posters with depth of knowledge about electrical systems (I am not one of them), and they do not always agree. Ask your question, and then step back while they have at it.

As for measuring equipment, recognize the difference between precision and accuracy. A naval gun that on average hits the other battleship but splatters shells over a wide area is accurate but not precise. A gun that puts all the splashes in one place, but that place is not where the battleship is, is precise but not accurate. You're going to pay bunches to get both in one instrument. But, the good news is that the precise but not accurate voltmeter can be used for seeing small changes in voltage when used repeatedly, and if you know that it reads 0.74 volts high you can use it for absolute measure as well.