good sun, terrible menudo, sore feet, water monsters

solar harvest

Forecast said foggy today, but it’s been completely clear since sun-up.  If it holds up this could be the first “full pull” charge in 10 days.

menudo

There’s a Latinx subpopulation in Newport, and a few Mexican restaurants.  One claimed “menudo every day” which to me is like a red flag to a bull.

The whole experience was pretty  bad, but the menudo was tragic.  I think it was just their pozole with some lovely honeycomb tripe and una pata thrown in.

Small bowl, $14 FFS.

feets

Dog and I do a lot of walking, and I did something to my feet in the last couple of days. I think it was a few trips up/down a long steep roadway 2 days ago that did it.   Not an unnoticed injury from an errant step or hole, as it;’s the same in both feet.

They are stiff and they hurt like they are half-cramped.  I hobble pretty good when I sit for a while but after a few minutes they are just uncomfortable.  I was walking in sneakers and may switch to hiking boots today to see if it helps.

water anomalies

One of the places I was hobbling walking yesterday was along the Newport pier area.   I saw something brownish break the surface and thought it might be a sea lion’s head crowning.  I’ve seen them do that in the immediate area.

When it came back up I realized it was pulsing:  it was a jellyfish floating right at the surface.  I hadn’t seen any jellies here so I watched for a while.  Those things are weird.

I walked a ways down the pier and saw a bunch of them in the shallows.  There are reflections and zoom issues but hopefully you can make them out:

I assume jellies don’t have a plan to go anywhere specific, although since some have photo- and other receptors they might be able to orient and control their depth in the water column.

Apparently their locomotion is hyperefficient:

…jellyfish have been shown to be the most energy efficient swimmers of all animals….  Muscles are used for the contraction of the body, which creates the first vortex and pushes the animal forward, but the mesoglea is so elastic that the expansion is powered exclusively by relaxing the bell, which releases the energy stored from the contraction….

Jellyfish achieved a 48 percent lower cost of transport (the amount of food and oxygen consumed, versus energy spent in movement) than other animals in similar studies.

 

watered batteries after three weeks of Eternal Absorption

I normally water every couple of couple of months, but thought it would be smart to check early this time just in case I was boiling off a ton of water.

The water use was in line with what I normally see.  I got a couple bloops out of each cell, with the exception of one cell that took 4 bloops.  Misfilled before?  Venting more?

WAG

I have two wild-ass guesses as to why: Continue reading “watered batteries after three weeks of Eternal Absorption”

battery checkup

A few days ago I noted the tall conifers were impeding my ability to get a full charge on the SLAs.    I ended up setting Vfloat == Vabs to get more absorption time and let endAmps drop further.

results

After four charging days of eternal absorption endAmps finally fell back down to normal levels and was still dropping slowly.  This suggests (but does not prove) there was no permanent loss of capacity.

I’ll keep the controller configged this way for the near future to see what happens.     I do not have the option (or desire) to upgrade to a top-tier controller with serious endAmps monitoring.  The mid-range Victrons’ adaptable absorption feature is reported to get confused with “false sundown” events and can short-stroke Absorption.  Then I’m in the same situation only with less money.

my WAG (wild ass guess) about what was going on

In general,

  1. Slow charging extends Bulk and truncates Absorption.   In my normal open-air camping the somewhat overpaneled system (2:6:1) starts making power quite early.  there’s not a lot of power available at those solar angles, but it’s something coming in rather than nothing.  I think this slow, gradual charging was making for short absorption that fit in the 180min window.
  2. Fast charging  makes for quicker bulk and longer absorption.  In this case the sun was largely blocked until it was quite high in the sky, about 11am.  Bulk was shorter and Absorption would have been longer but it was chopped off by my controller’s 180min max.

trashwalk, abandoned antique car, and continuing charging adventures

Not being able to make campfires isn’t a problem for me, but the inability to burn trash in the rocket stove is.  I had a plastic bag of trash and the dog was a bit feisty so I figured we’d walk back to the paid campgrounds to drop off the trash in those dumpsters.

Looking back at the van before we left, you can already see some light hitting the van through the trees:

Since it’s mid-week the campsites were mostly empty.  I took advantage of that to make a shortcut through the first site I saw.  It turned out to be a time-saver;  it did cut off a lot of trail time but more importantly Continue reading “trashwalk, abandoned antique car, and continuing charging adventures”

backchannel: converter charging your RV batteries with Tito

from this blog post

> Single stage converter/chargers can shorten the lifespan of your batteries by overcharging them.

Probably not.  Most old-school single-stage converters kill batteries by undercharging them with too low a voltage. They were typically set up to hold Vfloat, let’s say in the mid-13s.  Let’s review what “Vfloat charging” can do: Continue reading “backchannel: converter charging your RV batteries with Tito”

Mea Culpa: my own battery charging

I grouse enough about the mistakes others make;  here’s how I am undercharging my own batteries and doing some amount of damage.

My campsite is in the Mount Hood national forest.  Tall conifers of some kind make solar charging problematic, even with a 2.6:1 overpaneled system.   I moved spots a few times to maximize the amount of sun I can catch.

Normal situation:

  1.  run the bank down to ~12.4v-12.5v overnight
  2. hit Vabs after 10am and finish Absorption some time after noon.

Reminder that my batteries are fully charged when current acceptance Continue reading “Mea Culpa: my own battery charging”

backchannel: lead battery voltage while charging

from this post discussing resistance of Li vs. Pb batteries.  We know Li has lower internal resistance than Pb;  there is no need to exaggerate the effect.

 

> A totally dead[lead] battery will instantly read 14.4 volts when charging

 

It will not.

At C/2.5 charging (max for quality AGM) from 50% DoD it takes about 20mins to reach Vabs==14.4v, at which point  ~13.5Ah will have been replaced. (source)

At C/5 charging (max for FLA, min for AGM) it takes about 76mins to reach Vabs=14.4v, at which point 26.7Ah will have been replaced.

So it is not instant and the battery is not “completely dead” when Vabs is reached.

Pb charging: absorption finishing amps and state of health

tracking  endAmps

The Absorption stage of lead-chemistry battery charging is characterized by constant voltage (Vabs) and decreasing current.  The battery takes less and less current as it approaches full charge, and finally plateaus at a low rate.  Current is the red line in this graphic:

https://chargetek.com/chargingbasics.html

That leveled off terminal rate in the right third is called endAmps, finishing amps, tail current, etc. It is typically C/200 to C/100, or 0.5 to 1A per 100Ah of battery capacity.  Fresh batteries tend to have lower endAmps reached more quickly, and tired / old / abused batteries tend to have higher endAmps reached more slowly (longer Absorption phase required).

 > I have repeated this test with AGM batteries [in] worse shape that exceeded 7 hours to attain 100% SOC, likely due to sulfation.

If that is so, one might be able to record endAmps monthly as a metric for battery state of health.   It might not tell you when a particular battery is toast, but increasing endAmps would be an indication of design, all other things being equal.

MainSail suggests endAmps greater than the 0.75%C (C/133) indicates the battery is no longer running at full capacity:

Over many years of capacity testing hundreds and hundreds of batteries, flooded, GEL and AGM I have yet to see a lead acid battery that could [deliver] its full storage potential at anything less than 0.75% in tail current at absorption voltage.

The wording is a bit odd there, and IMO means “worse (higher) tail current than 0.75% rather than ” < 0.75%”.

increasing Vabs when Absorption duration is limited

Charge controllers have different strategies for knowing when to end Absorption

  • high end controllers may hold Absorption until the specificed endAmps is achieved as long as it takes (or as long as sunlight is available).
  • mid-range controllers may hold Absorption for a duration specified by the user
  • low-end controllers usually hold Absorption for a set duration like 2 hours.

In each of these cases, batteries in poor health may require longer than the available time to drop to endAmps.  One workaround for maxxed Absorption duration is to increase Vabs.  I propose increasing Vabs in 0.1v – 0.2v steps until endAmps can be achieved within the available duration.

Caution:  as Vabs creeps up you will either hit the maximum allowable setpoint (AGM, Gel) or need to water more often (flooded).

 

longshot:  decreasing charge rate when Absorption duration is limited

Charge time remains relatively constant whether charging at max or min rates for the battery.  Again quoting Mainsail:

charging AGM at C/2.5 (max rate) resulted in the battery being 63.3% “full”3) at Vabs and being fully charged in 5hrs, 30 minutes (20min Bulk, 5hr 10mins Absorption)

charging AGM at C/5 (min rate) resulted in the battery being 77.4% “full” at Vabs and being fully charged in 5hrs, 42 minutes (76min Bulk, 4hr 26mins Absorption)

It is conceivable that charging at a minimum rate (particularly for flooded that can be successfully charged as low as C/10) could also help absorption finish faster.  Overall time would be about the same but the charging process would spend more time in Bulk which by definition is not time-limited.

anecdote

My own set of flooded golf cart batts (2x 6v in series) is Absorped at 14.6v @ 70F and finishes at 1.79A, or 0.81% (C/123) in about 2.5 hours. This suggests I have lost some capacity in 589 cycles at 50% DoD (installed 9/24/2018).  I wasn’t measuring it before so I can’t compare to new, and the loss of  capacity is not noticeable in practical experience.

When my bank can no longer reach endAmps within the three hour max the controller allows I will try increasing Vabs.

 

backchannel: “my [200w] solar refills my batteries by 10:30 am nearly every day!”

I think it’s worth talking about so onlooker solar newbies don’t get confused about the abilties of their solar config, worry about whether or not it’s working, and/or murder their lead batteries.

From this post on the Promaster forum.  This is the system in question.  The author and I are running the same battery bank.  He charges it with 200w of panel and I charge with 570w;  I still don’t get my bank fully charged “by 10:30am nearly every day”.   It can happen (a night of shallow cycling, early AM driving, etc)  but it’s not normal.   I am not calling BS;  rather, I suggest critical information is either being left out or not understood.   Either way it’s bad for solar newbie onlookers.

======

I think 200w of panel is a real sweet spot for vandwellers. I like that amount and recommend it as a sane default.

> my solar refills my batteries by 10:30 am nearly every day!

Depends on what “refilll” means.  It’s pretty easy to hit (an incorrectly measured) “100% SoC” by voltage ~12.8v or even Vfloat.  It’s pretty tough to get deep-cycled Pb fully charged (ie, completed Absorption down to battery manufacturer spec — endAmps) with solar-only charging by 10:30am.

Given that lead-chemistry batteries take 2-3 hours to finish Absorption after deep cycling, Vabs, usually in the mid-14v range, would have to be attained by 7:30am-8:30am. Not too many solar-only systems can do that, even significantly overpaneled ones charged by MPPT under excellent ouput conditions (temperature and insolation).

Caveat to onlookers: the controller switching to Float does not mean that Absorption stage was successfully completed. It means the controller switched to Float.  The way to know for sure that Absorption is being completed is to watch your meters during late Absorption and verify that the battery is accepting something like a typical  C/200-C/100 cutoff (or whatever your battery mfg recommends). For a typical 200Ah lead bank this would be something like 1-2A. If your controller allows you to set endAmps of C/200 or whatever, go ahead and set it. Most consumer controllers don’t do this (or can’t separate out battery charging and loads to measure accurately) so you may have to just max out any Absorption duration setting that is available. Once you know your system is finishing Absorption correctly you can let it fly on autopilot. If you are offgrid and your controller refuses to finish Absorption, you might choose the nuclear option and set Vfloat == Vabs (check water levels more often).

Example with data: I am putting ~175w into a 220Ah bank this partially-cloudy morning in NV and at 10:30am local I still hadn’t kissed my 14.6v Vabs. This puts me at a fully charged (“filled”, IMO) between noon and 1pm. My system has more panel but because I am running loads on my system (~200w worth of laptop and crypto mining) this is a pretty good approximation of how a 200w:215Ah system with no loads would charge the bank on a good day.

If I stop being an idiot and don’t run the crypto rig until later in the day I can typically get fully charged by noon assuming my preferred level of snowbird insolation. 🙂 This is with an overpaneled system and not the usual experience with solar.

Having said all that, banks cycled lightly to ~80% or assisted by alternator (or other) charging in the early morning would have a decent chance of being fully charged by 10:30am.

backchannel: solar is a luxury

I generally don’t look at the username or other details of a poster’s presence when replying;  I stick to the “content of their [text] character[s]”, to paraphrase MLKjr.  This can cause me to waste time casting pearls before known swine.

So I didn’t realize that the post was by a daydreaming pothead who frequently bombs half-baked ideas at us in /r/vandwellers.  This particular one didn’t seem as moronic as usual (only confused and overconfident) so I engaged.  It had the title:  “How often do you drive your van? I think solar is a luxury. I’m thinking driving to work and to buy food ect is going to be plenty of time for the alternator to recharge 4 deep cycle batteries. Instead of having solar you could recharge with a system your van already has.

So here’s what I wrote before I realized s/he probably wouldn’t even remember writing it later:

Solar charging and alternator charging are different beasts that work better together than either do separately.

Solar isn’t mandatory if you can plug in a smart converter at work a couple times a week to get the bank fully charged.

People who want to charge from alternator only would be wise to look at lithium or carbon-foam chemistries which don’t care about partial stage of charge (the scenario you presented). Lead batteries die early from partial charging.