First Time Boondocking Plan - Tech Question

[RLGetman]

I am trying to learn & prepare to Boondock for 12 days in Oct. I have a standard 5er setup (two 6 volt batteries) and a 2000w Honda generator. For convenience I purchased a battery level indicator at Camping World that plugs into the 12 volt receptacle in my coat closet and it reads 13.7v when I am connected to shore power. I have a multi-meter which reads exactly the same as the indicator.
My pre-boondock test plan is to disconnect from shore power, switch ref & water heater to LP, turn off all ghost circuits (clocks, TV, etc...) and just use lighting (I have LEDs) when needed. I want to see how long my batteries will last before needing a charge (I read that 12v is 50% and time to charge). I will then run the generator and see how long it takes to charge back up to 13.7v.
Is this a good plan? What am I missing?
Thanks

[McZippie]

ArcticDodge wrote:

Old-Biscuit wrote:
Boondocking is about FUN

Run the genny couple times each day and enjoy the camping.

X 2

X3 we run it when voltage gets down to 12. for as little 15 to 20 minutes.

Sometimes we charge with 265 amp engine alternators for 10 to 15 minutes.

[BFL13]

I thought you used a load tester only after the batts were deemed "full" (by whatever indicator)

What good is a load tester after a 50-90?

---------------
There seems to be some sort of "crossing the line" as in "going too far," where you do 50-90s and have all sorts of trouble afterwards, and doing 85-97s such as on solar where you don't see so much of that kind of trouble ( if you have enough solar for the size of the bank to do that.)

I suppose it is to do with battery chemistry magic, but it is for sure you can go for a longer time camping with "incomplete recharges" when the recharges are only 3% incomplete than you can when they are 10% incomplete.

Again that is with Wets. I have no info on comparable AGM situations.

If we are to compare Wets vs AGMs for camping off-grid, we should make sure we are both doing 50-90s in a row for how long, and not compare doing 50-90s on Wets vs 85-97s on AGMs

[tplife]

BFL13 wrote:
...AGMs may be wonderful, but I would hate not being able to measure to know for sure...

Instead of using a hydrometer, you use a load tester, around $40.00.
Kendall's right about the time to charge on a converter. Charge advantages are using higher-Amp 110V chargers or alternators to charge the battery. Of course, that's no reason avoid an AGM, unless you like buying new Levis after you change out your batteries. And corrosion in your battery box. Explosive hydrogen gas. And split battery cases when your battery freezes. I'll never know these things because my batteries are AGM.

[KendallP]

double post

[KendallP]

As I said... this is an oldie. Here's a canned response I found in my rv.net folder. Note the real data from 2 typical RV converters charging an actual Lifeline...


I have yet to see any test results on an AGM that when charged at any fast rate with a typical converter at say 14.4V or so... doesn't begin to force the amperage to taper long before 90% SOC.

Here's one that is being charged at about C/2. The IOTA dropped out of boost at 15 minutes or so, but notice that the Amps still begain to taper at just 10 minutes in. These are typical RV converters. This is how a Lifeline reacts to them in real life. Even at C/2 it took over 2 hours to go from 40% to 90%. The IOTA took 2 1/2 hours.

(Below the Lifeline chart is BFL13's infamous "ugly graph" that shows it took 129 minutes to do a 50-90 on a pair of 6V GC2s at only C/3. And as we all know... the 40-50% portion of the charge is definitely the easy part. It only added about 10 minutes. So the speed winner here is actually the GC2s. At best it's a draw... even at a slower charge rate for the GC2s.)

(And at the bottom of the page is Fisherguy's graph. 2 hours or maybe 2:15 to do a 47-90 at C/3 using another typical converter.)





BFL13's Ugly Graph

[KendallP]

BFL13 wrote:
AGMs may be wonderful, but I would hate not being able to measure to know for sure.

Hey B,

The sailors worked with Lifeline using Lifeline-supplied AGMs. And out of those experiments came a realization that AGMs still require occasional overcharging (equalization) to bring them back to 100%. Thus their manuals were updated accordingly.

[KendallP]

tplife wrote:
You're right, I'm wrong, the military and aviation and Rock My RV and Harley-Davidson all use AGMS because they're just too stupid and didn't read that scientific conclusion over at cruisers forum...I stand corrected.

I accept your apology. 🙂

tplife wrote:
Admitting that, lead-acid cells don't have the low resistance of AGMS and as a result generate head during charging. That low resistance is why AGMs charge so much faster (they do) than standard lead-acid batteries.

Yes. They CAN charge faster. No argument there. But with typical RV converters that regulate voltage... they don't. Higher voltage is required to "push" the extra current in faster. But to keep from frying your electronics, you would have to disconnect the bank and charger from the coach in order to realize this "advantage." This is well known. If you think this is incorrect, then I'm afraid the burden is on you to prove otherwise.

As far as your next post is concerned, unless you house your batteries upside down or inside the coach with no outside ventilation, then I didn't see a single advantage out of all those listed.

[BFL13]

It must be a learning thing when you have AGMs how to tell what is going on, I don't know.

I know my Wet true deep cycle 12s (T-1275s) and 6s all act the same way when doing 50-90s when camping. Mainly, after only two 50-90s in a row, the SG is in the white when charged back up to 90 according to the AH count (Trimetric) Subsequent time on the solar before dark does nothing to help with that SG reading but does add some AH.

So the batts act after that like they are at the indicated capacity of 90% according to the Trimetric, but they are in trouble according to the hydrometer.

This means the good stuff must all be at the bottom of the batteries out of reach of the hydrometer, I suppose. Why, I have no idea.

All I know is I better fix that sometime before it is too late.

So what happens inside an AGM, and how do you know? I would be worried it was at the equivalent to being in the white but you can't tell. OTOH, the glass mat may keep things more even, I don't know.

I do know that I hate not knowing, and so I prefer to be able to use an hydrometer and get the facts. After that, I can go into my PITA routine (or not so bad with 6s--don't know yet with the T-1275s) to fix the problem when I get home.

AGMs may be wonderful, but I would hate not being able to measure to know for sure.

[tplife]

"AGM batteries are not the best choice for all applications - they are rather expensive compared to flooded batteries. However, their safety and design features make them the battery of choice for many applications, such as:
•Where you cannot have fumes or hydrogen, such as in poorly ventilated areas, or where fumes may cause corrosion to electronics, such as repeater and cell phone sites.
•Where resistance to shock and vibration is important.
•Where spilled acid from leaking, tipped, or broken batteries cannot be tolerated.
•When installed in a location where maintenance would be difficult or expensive, such as remote communications sites.
•Where the batteries may be subject to freezing (-40 degrees F or lower).
•Anyplace where you need a reliable totally sealed battery for safety or environmental reasons - wheelchairs, medical standby power, inside RV's, computer room UPS systems, or in enclosed spaces in boats."

Reasons to use AGM Batteries

If those aren't advantages you can benefit from, then no, I would agree that it doesn't make sense to pay more for an AGM.

[tplife]

KendallP wrote:
Oh, here we go.

Not an AGM hater, here. But not a lover either. The sailors over at cruisers forum settled this long ago. (Hint: AGMs were not the winner.)

OK. With automatic, voltage controlled converters, charge time is virtually identical.

The real benefits of AGM are a lack of maintenance.

However, when one performs successive 50-90s or... worse yet... 40-80s... in order to bring them back to 100%, a mild overcharge is required... just like with your typical flooded batteries. Only man, do you have to be careful.

If you always recharge to 100% after each draw, then this is a non-issue and AGMs have value. Of course... at a slight cost in Amp hours per volume of battery.

You're right, I'm wrong, the military and aviation and Rock My RV and Harley-Davidson all use AGMS because they're just too stupid and didn't read that scientific conclusion over at cruisers forum...I stand corrected. Admitting that, lead-acid cells don't have the low resistance of AGM batteries and as a result generate heat during charging. That low resistance is why AGMs charge so much faster (they do) than standard lead-acid batteries.

[KendallP]

Oh, here we go.

Not an AGM hater, here. But not a lover either. The sailors over at cruisers forum settled this long ago. (Hint: AGMs were not the winner.)

OK. With automatic, voltage controlled converters, charge time is virtually identical.

The real benefits of AGM are a lack of maintenance.

However, when one performs successive 50-90s or... worse yet... 40-80s... in order to bring them back to 100%, a mild overcharge is required... just like with your typical flooded batteries. Only man, do you have to be careful.

If you always recharge to 100% after each draw, then this is a non-issue and AGMs have value. Of course... at a slight cost in Amp hours per volume of battery.

[tplife]

full_mosey wrote:

wa8yxm wrote:

...
Some folks like to brag about how fast some makes of AGM batteries charge.. yup, 5:45 instead of 6:00. 5 times the price and it saves you a few minutes is all.

I would like to see a link to prove that 5 x $ comment!

Sam's Club has wet 6V GCs for $110 and AGM 6V GCs for $180.

I get $70 or a 61% difference. Using your 5 x $, the AGM would cost $550!

I would be pleased to discuss the factual merits of both wets and AGMs. 🙂

HTH;
John

There are so many advantages to AGM batteries over the standard lead-acid models, that regardless of charge time, I'd run, not walk, back for another Optima when mine dies. I don't need a hygrometer, battery box, vents, gloves, new jeans due to acid burns, and I can mount and use it right inside the enclosure with me, upside down if I want and run it down much lower without any damage. If you consider the actual cost per Ah, they're not much more expensive, and certainly not 5X as much. I bought my Optima for $120.00 at costco instead of the wet-cell at WalMart for $80.00. From my experience, I got a lot more for my money from my smaller, lighter, better AGM instead of saving a little $ up front.

Flooded vs. AGM and Gel

[KendallP]

Well... if you're going to be THAT way about it... then I'll, once again espouse my old mantra...

CAPACITY IS KING!!!

Though the actual effects may not be as pronounced as the theory suggests... Peukert says that... (paraphrasing)... per a given draw... the greater the capacity, the slower the draw per cell and the actual capacity is increased exponentially.

Put another way...

If you take 100A off of a bank over 100 hours, the capacity left will be greater than if you take the same 100A off in 20 hours.

Cram as many amp hours in your battery box as it will take. 4-GC2s would be great! Try and be sure to keep pairs of the same age in parallel together.

I don't have the height for golf cart batteries and have room for a max of 3. So I have 3-Group 27s for a total of about 300 Ah.

With a few hours a day on an old 13" tube TV/DVD player, a few hours a day of boombox, some furnace at night and a few hours on the LED bulbs, I can go 5 days before my bank gets down to 50%. As a broke business owner, I have never taken a longer camping trip than that, so solar is a non-issue for me... thus far.

However, my rig is old and built at a time where parasitic draws were virtually non-existent. My CO and smoke alarms run on their own batteries and I have no fancy monitors and such. About the only draw I have are a few gas valves. Not everyone is so luck to have such an ancient rig. 🙂

[TenOC]

Old-Biscuit wrote:
Boondocking is about FUN

Try to live without electricity (except for the Ref). This is "CAMPING not RVing. Get up with the sun. Dinner before dark. Sit around the campfire at night and watch the stars. No TV or Radio. One or 2 scented candles (in a jar for safety). Live like your grandparents did. With only the Ref and water pump drawing electricity I can go 4 or 5 days before I require a recharge. I did purchase a 140 watt (?) portable solar unit from Harbor Freight for $150.00 (?) that allows me to boonbock for a week without running the Generator -- that I carry only for special electrical needs -- but almost never use.

[MEXICOWANDERER]

TURNKEY wrote:
Why is no one suggesting solar???
I've gone through the same questions recently and found solar is the best for light power draw boon docking.
I would refer all to HANDYBOB'S blog http://handybobsolar.wordpress.com/

Some environments are cut out for solar, others aren't.