There are some damn-fine reasons to mark off a few minutes on a “summer” Friday morning chat to talk for a few minutes about prepping and batteries.
I can speak with some authority because my name somehow shows up on some patents related to battery state-of-charge instruments.
On the surface, this is no big deal, but the more you understand about batteries, the more being a co-holder on software related to battery charge/discharge levels is a very big deal. In other words, people who really know their poop about batteries are few and far between.
But if you read this morning’s discussion (and maybe print it off for further study) you can join the ranks of the battery-wise.
So top up the coffee and I will make this as short and to the point as possible.
Application Note: This discussion is specifically for preppers, ham radio ops participating in field day later this month, and RV’ers as well as boaters.
What is a Battery?
The first concept to master is the terminology of batteries. Because once you understand what the language means (in engineering and software design terms) a lot of misconceptions quickly fall bay the wayside.
Cells: A cell is generally comprised of an anode and a cathode. In between them is an electrolyte. The electrolyte can be dry (semi-dry), wet, or even air (as in zinc-air cells) can be used.
The key concept is that a cell is one collection of parts that uses electrochemistry to store and release energy.
Cells are temperature sensitive.
A typical cell may be fully charged at 2.1 volts per cell if it is hot outside, say 100F. This translates to 12.6 Volts when discussing a 12 Volt automotive, marine, or RV battery.
As the temperature decreases, the individual cells slow down as chemistry works slower (and at higher voltages) as temperature drops.
By the time you get down into the area of 65F, the resting state of a fully charged battery may climb to 2.3 Volts per cell – which is why the auto and deep cycle equipment is based on 13.8 Volts for charging.
Now let’s fast-forward to winter. When it is about 30 F outside, the fully charged cell will need 2.55 Volts per cell. This would put us around 15.3 volts with a properly charged (nominally) 12 Volt battery.
So Much for Cells – What is a Battery?
A battery is a collection of cells. Battery geeks speak in terms of charging and discharging as volts per cell. Humans, just refer to the nominal battery rating – which is good enough for most purposes.
A common battery may have plates made of lead (or lead-antimony for auto use).
What are Majory Battery Types?
Conventional automotive cells are comprises of many thin plates within their 6 cells. On the other hand, a Deep Cycle battery will have often half as many plates, but will deliver more energy over more cycles.
High plate surface area will give maximum terminal voltage under load for a brief period. Auto’s don’t use a lot of power over time. A short burst of power (10 seconds) is usually enough to start a car.
On the other hand, if you are operating an RV and you have an inverter going and there’s a show on satellite, you want a very good deep cycle battery. You want to see the whole movie, right? So power at a modest level (perhaps 500 watts) for as long as possible.
What About Special Cells?
Special needs are best suited to specialized batteries (collections of cells in a container) that have desired characteristics.
If you have a marine application, a Sealed Lead-Acid (SLA) battery is preferred because battery acid and salt water combine to create chlroine. Marine gel cells such as those from West Marine are a great choice if the battery could be “salted.”
If you are bouncing all over hell-and-gone, then Absorbed Glass Matt batteries are superb. Just expect to pay a lot more for them. The seal AGM battery in our old airplane was a $275 item three years ago and I doubt they have gotten cheaper.
Is there One “RIGHT” Battery?
Don’t we wish!
No, there is not. It takes some serious consideration of the battery’s purpose in order to select the best battery.
Sure, SLA-AGM for everything (or gels) may be good, but here is where we get into two critical concepts:
Cost Per Watt-Hour of Storage
A watt is a unit of work. The problem is that in order to find out capacity of a battery, you need an integrating watt-hour meter, of a microprocessor-driven Amp-Hour meter (see the Xantex catalog, I was at one of their acquired companies ack when) for a selection of these. They are precisely what you need in order to accurately determine battery state of charge.
When you are just shopping, look for the best cost per amp-hour or best cost per kilowatt-hour (look to manufacturer spec sheets) and try not to overpay too much.
A couple of examples:
We go to the WallyWorld and find a group 27 sized mixed use battery for our trolling motor. It costs $140. The manufacturer claims it will deliver 100-amp hours.
Since we run the trolling motor slowly, (10 AMPs) we MIGHT get 6 hours of use out of the battery.
I know – you’re thinking “How come I can’t get 10 hours of trolling?”
Here’s the problem: At 13.8 volts (battery just off the charger) you might be getting 138 watts of work. But battery manufacturers rate batteries in Amp-Hours for convenience of testing and they don’t think a battery is dead until the voltage with the motor on drops to 10.5 voits. But you see? 10 times 10.5 is only 105 watts of work when you get out into the fully depleted battery area.
But stand by, fellow troller, there’s another gotcha in the wings:
Cycle Life and Depth of Discharge.
Note: Charging is a temperature dependent art. Get a charging temp table from your battery manufacturer.
Holy smokes, now what?
Sad truth is that you might be able to get “name plate” service for 100 cycles out of your battery, but if you were just a little gentler on the battery and only used half its capacity, then you might get 2,000 cycles out of it.
The reason has to do with how sulfury crystals are deposited on the battery plates and driven back into solution during charging. (This is how hydrometers work.)
And that gets us to the whole mattery of battery charging and discharging.
Multiple Stage Charging
When a battery is nearly empty (say below 11.4 volts on a 12 Volt system), the battery will (after a minute or so, and an effect called crack of the whip) begin to store energy as fast as you can toss amps into it. This is why big sailboats like the one Elaine and I lived on *(and me for 10 years+) use big computer-controlled charging systems. They charge very quickly with minimal engine run time. Work slick on RV’s, too, espectially if you aren’t going anywhere for a while and you just want to “top off batteries” with an hour or two of engine time.
This is BULK charging.
As the voltage slowly comes up, to about 14.2 volts, that battery wioll charge on a declining current basis until it will accept only 1%, or so, of it’s Amp-Hour rating. I know…
Let’s go back to that 100 Amp=Hour battery we picked up. When we charge it at 14.2 volts, at some point the current going into the battery will drop to 1 amp (1% of the 100 amp hours, eh?). Simple as pie.
This is the ACCEPTANCE charging part of the overall charging profile.
Last, come FLOAT where we kick the voltage down to 13.2 or so, and the battery is charged and not wasting energy from the charger (which would be dissipated as heat anyway). Dloat varies by temperture, too. Higher when colder. Lower when hotter.
After a fair number of charge and discharge cycles, and being more necessary as the depth of discharge increases, a liquid cell battery may be equalized.
Over cycling service, not all sulfur crystals are driven back into solution during charging.
To equalize, gradually increase the charging voltage to perhaps 15-15.4 volts, being careful to avoid thermal runaway) and allow the battery to begin to “gas” – it is not boiling.
Always wear eye protection, conduct equalizing in a fresh air environment because the gases released during equalizing are Brown’s gas – an explosive mixture of hydrogen and oxygen.
Optimum Battery Cycling for Field Day (Ham radio or Dry Camping)
Start with fully charged batteries. Run until battery voltage drops to about 11.2 volts under peaks on SSB or CW,
Then charge like hell until the battery voltage comes up to abourt 14.1 volts – kill the generator and make another 1,000 points or finish the movie.
When you’re all done, charge the batteries full, equalize, and try to explain to people who don’t work ham radio contests how being in the rain in a tent doing high speed code with a generator running just outside is fun. (Good luck with that…send in your reports…) I should mention the ham radio “sale” is much harder to dry campers with a cold toddie and a movie going…they use cells phones.
With good care (missing here at times) a battery should last 8 years in deep cycling service. Mine would go longer but I keep getting too busy to equalize. My bad.
Next Friday (if I remember) we will do solar panel basics…and maybe a simple load sheet. So dew drop in, as they say (somewhere, but not here).
I think that about covers the basics… There’s a lot more on the Peoplenomics.com site with how to do a load sheet and all that. But you may have some work to do before the weekend starts. Besides, come to think of it, I have another (guess what?)…
Eye Surgery Progress
Off to the big city (Tyler) again this morning – and again Monday – for more eye checks.
The eye is sealed well now…but there is a bit of blood from surgery which is in the VSS (visual saiine solution) by eyes now run on, instead of normal aqueous fluid as was installed at the factory.
To ensure pressure stays down, and to encourage the exchange of the bit of blood in the fluid, I will be on two kinds of drops. These are distinguished as the “blue drops that lower pressure” and the “Green drops that slow the production of fluid but give you a headache in some cases.” Yes, I know that one, now.
My vision was so foggy I was looking for the Ronnie Milsap songbook until it began to clear, about halfway through Thursday’s rant on Break Away Civilizations. (To which I should add Richard Dolan’s outstanding work in the field – oversight, ahem, so to speak.)
I would emphasize to those following along at home that a) none of this began until about five days after I began messing with the feng shui of the office and the ranch.
The second thing is, cataract surgery is nowhere near like what I am going through…so if you are thinking about surgery, go for it.
My problems arose from having one set of surgeries to take out the cataracts back in 1979. Implants were still on the drawing board, so I didn’t get them until 1991. And then they aren’t as good as today (engineered materials, don’t you know) so only one of mine failed, and that after 25 years of all kinds of head-banging adventures. No telling what actually set off the problem, I just know it crescendoed in April of this year.
But no, cataracts of the garden variety t’ain’t no big deal. My case is “special” – and it’s one of the toughest for the month (and maybe quarter) for a specialty practice.
So please don’t let me scare you out of the surgery…it’s great once done. Just – if you can help it – don’t spread out the removal and the implants by over a decade for starters. And don’t jump down off tractors and heft 150 pound hunks of concrete a second later and then stand up quickly. Give your eyes time to equalize a bit.
I’m a great believer in the Theory of Common Sense. Darwin awards as examples, the missing companion volume The Practice of Common Sense is being slowly drafted by people like me.
On the other hand, if you’re not making mistakes, check your pulse.
You may be dead.
A Friday First
Telemarketing slime is getting crude.
I had a call from a telemarketer Friday.
“Hello, this is the Windows Technical Support Department calling about your computer…”
Right here I knew is was slime (Microsoft doesn’t act this way or call from blocked numbers) so I “went George” on him.
“Cool. I have heard about telephone calls from outfits like yours…calling people and bothering them in order to try to scare money out of them. Go ahead…give me your best shot…let me turn on a recorder, while we’re at it… OK go ahead….”
A moment of silence.
“F((( You…” click.
I tried to call back to talk to the empty-pecker’s boss, but like I said, it was a slime call…and it’s a safe bet that unless it’s my son calling on his fancy backwoods SatPhone, its what?
NOT Windows tech support, of that you may be fairly sure.
With that, we have a busy weekend ahead…I’ll be supervising Elaine lifting everything over 10 pounds for another week.
She’s the best damn Chauffer, bartender, philospher, and personal assistant in the world and I am blessed. What the hell did I do to deserve things this good? Next lifetime, maybe a few less eye surgeries, please?
Have a fine weekend and write when you get rich…