Tag Archives: battery power

Raising the wick on our DC power

More than thirty years ago Jim read a book, The Magus, by John Fowles. The old man turned up the lamp to better show a photo. Jim liked the concept enough to purchase an Aladdin kerosene lamp.

Aladdin still fits their kerosene lamps with silk mantles and the white-hot illumination is silent and intensely bright, if you raise the wick. But you don’t unless you want to reveal something by the light. The lamp otherwise quietly and warmly provides background illumination. Until you raise the wick — then the light power is really on.

We’d not heard the turn of phrase but found it very appropriate for our DC power project. This started a few weeks ago upon our return from QuartzFest [LINK TO BLOG RE QUARTZFEST] in the Arizona desert. Our battery power was great whilst gaining solar power and until we use lighting or fans or the water pump. And the battery power seems to sag and gradually return less and less throughout the evening.

The fix is simply new and more storage batteries. Jim has long considered increasing our battery bank from two to four. Four years ago he changed our second or third pair of troublesome and short-lived 12v batteries to a pair of 6v golf cart batteries. These well outlasted the 12v batteries although some of the credit, no doubt, goes to the much improved PDI Intellipower converter charger. Our old converter charger apparently boiled out our batteries in short order, necessitating annual replacement of the 12v rv-marine batteries.

Soon after switching to a pair of 6v golf cart batteries (U2200 Interstate) Jim also switched us to the new and much superior PDI Intellipower 60 amp converter charger. The new converter charger has float rate charging to maintain full batteries without overcharging and has a boost rate to more quickly bring the batteries up to speed when they are low.

These two were okay but never great

But our two 6v golf cart batteries never seemed to have much depth. We’re great during the day with sunshine bathing the solar panels and feeding the batteries. After sunset the battery drain starts. Read a little, wash some dishes, take a shower, run the furnace a little while, and there’s not enough to run the ham radio at full power. The two 125 watt solar panels can, by 10 a.m., return our batteries to full charge. We enter the float charge stage on the solar charge controller, where it drops the charge rate to keep the batteries from going more than 14 volts.

four 6v batteries to make 12 volts with 464 ah

Two issues cause this battery drain: four year-old batteries and only 225 amp hours capacity even when they were new. Our new batteries are 464 amp hours, attained by wiring two series pairs of 6v 232 amp hour batteries in parallel. Jim wired these with four identical length #4 battery cables to optimize the load balance between all cells.

Although the Airstream’s original battery cables were #6 welding cable Jim decided instead to buy #4 battery cables. Welding cables are intended for portable use and a different set of requirements than cables for stationary batteries. Welding cables need to remain flexible and easy to coil and store. Battery cables don’t need the flexibility or coiling attributes and, properly specified, SGT battery cable will provide self extinguishing jackets not found on welding cables.

a red and a black set connect both pairs of 6v batteries to the RV's 12v mains

The current carrying capabilities of #6 AWG and #4 wire are, for our short cable distances, both adequate. The #6 wire is rated for carrying up to 120 amps, and is rated for voltage drop of 3% or less for our 8 feet total wire length from batteries to load (12 volt distribution panel). Our RV does not have an inverter (to convert DC to AC voltage). Our largest load is the amateur radio, rated at only 22 amps. We’re fine with either cable size unless we install a large inverter — then we would up the cable size.

The connections for the batteries need to be tight, weatherproof, and free from scuffing. We make the main connections between house mains and battery mains in a 6 X 6 X 4 pvc junction box mounted to the trailer’s front exterior wall. We found a nifty fuse holder with two 3/8″ posts, brass washers and lock washers and nuts. Without the fuse it becomes a sturdy dual-post terminal for our positive and negative cables in the j-box.

Polyethylene battery box holds upper pair of batteries

Jim found a polyethylene battery box from All Battery Co which fits nicely over the original battery box. But how to clamp it securely for travel? We devised a hold-down which slides through slots in the lid and the box ends. All-thread attaches from small l-brackets on the trailer’s a-frame up to holes in the 1/4″ X 1″ X 24″ hold-down bar. Jim felt the battery box might still slide on top of the lower box.

aluminum tray holds upper battery box

He devised a nice battery tray of 1/8″ X 2″ X 2″ aluminum angle. The corners are bolted together, a downward flange near each end keeps the tray from sliding left and right, and the all-thread centers through a flange at each end of the battery tray. The poly battery box nestles snugly in the tray.

Lower batteries now are a lot better organized

Since the two upper batteries in the poly box and tray will be a lot to remove (135 pounds comprised of two batteries, four battery posts, two hold-down bolts), we installed a battery watering system from Camping World. We have a quick-connect fitting outside the battery box and a squeeze-bulb filler to fill the lower batteries from a distilled water container. When the upper batteries need water we will also address the lower batteries and without needing to remove the upper batteries first.

We have dry-camped various times over the past several years and have never had the luxury of a little spare battery power. Typically we would have seen 12.2 or 12.4 by bed time and the same low reading the following morning. The furnace could draw hard on the pair of batteries, the fan running noticeably slower than normal. And the lights would dim as the evening progressed.

Junction box and upper battery box with hold-down

The results from switching to four 6v golf cart batteries instead of only two have been very gratifying. We have run over two weeks on solar only and the batteries have remained strong throughout the day and night. Initially we babied them out of habit. Then we tried running as many lighting circuits as we might when plugged into shore power. No problem, the batteries might show 12.4 or 12.6 before bed time and by morning we’re again starting at 12.8 to 13.0. This is a great improvement.

Arizona has over 300 days of sunshine every year. We’ve had only two or three cloudy days in four months. We probably won’t, until we leave here, learn how the batteries do on the second day or third day without sunshine. Worst case, we have the 1KW Yamaha generator. We won’t, however, be surprised if the batteries hold just fine for several days.

When Jim recently described his planned changes to DC storage battery, cabling, and solar panels to friend Jack AA8Q, Jack stated, “Fine business on raising the wick on your DC power system”. Yeah, it’s definitely brighter now.

Now if only the truck can tow the extra 135 pounds . . .

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©2007-2012 Dreamstreamr

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Odds and Ends

We voted last week.  Picked up absentee ballot from our mailbox and realized we had zero days to deadline to get this in the mail and on the way to NC.  Our first time to do this, we’d always been home to vote before and relied on local newspaper for sample ballot and our research.

This time we studied the candidates electronically with great assistance from a voting info page sponsored by one of the universities.

A sign I’m back into my rhythm — three days in a row I’ve enjoyed my cup of matcha tea on our patio by 06:00 a.m.  It makes me feel great to watch the sun rise (closer to 06:50), to breathe the clean morning air, hear the morning noises of a busy city street, sip the rich tea, and read just one scene from a play or one small chapter of a slow book.  Except this morning I spent adding to these paragraphs and my next post.

We were moving around and committed to other things for the previous six weeks.  I might not have had but one sunrise cup of tea.  Didn’t even get out of bed until after 7 or 8 or even later a few times.  Well yeah, those times I stayed up until after 01:00 in the morning and am not too likely to get up right away.

I like this groove better.  Quiet time, just a little niche in the day, to get my my bearings.

Found the sole general delivery Mesa Post Office last week for our forwarded mail.  Mesa has maybe a dozen contract postal units (CPUs) serving their respective resorts like this one and several branch post offices in Mesa. We learned last year the branch post offices won’t handle general delivery mail.  Most folks staying in these many resorts simply get their mail through their CPU.  We receive a key from the resort for our mailbox, and the CPU stuffs whatever arrives (plus a generous helping of junk mail) into our box for us.

Our mail would go from the forwarding agency (Escapees) to the local post office, and then to the CPU for our resort.  But last year one of our forwarded packets disappeared.  The CPU lacks a scanner and so cannot account for what the Post Office does, and does not, transfer to the CPU.  Our packet left Escapees and the Post Office scanned it successively throughout its journey until it left the local Post Office.  Did the CPU get it?  We’ll never know.

This year we’ll use General Delivery instead of the resort’s CPU.   We pick up our mail every week or two directly from the post office.  The post office retains secure chain of custody on our package until we pick it up ourselves, at which time the post office scans it out as delivered.  Safe and sure.

Finally turned on the AC, it was 92 outside in the shade and we’re parked in full sun.  Mornings were 60 degrees, really nice for sitting outside.  I’m back to an old habit, making a cup of matcha and reading a chapter at sunrise.  Sort of symbolizes return to routine for me.  But this week the morning lows are high 40s, a little chillier.

Seems funny to have the air on and still turn off the converter to save electricity.  But the solar panels are more than capable, with all this sunlight, of maintaining the batteries throughout all the day’s use.  Why pay for more kwh?

We’re running the lights and fans and fridge controls and phantom (okay, all the battery loads) with solar charging only.  This is an experiment, to see how well it works and for how many (if any) weeks we can do this as the sun gets lower and lower in the sky.  Our solar panels aren’t yet tiltable but I’d like to correct this — maybe I can get to it in the next couple of months?

Jim and Debbie

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