Tag Archives: DC Batteries

batteries, Electrics, school bus RV, Skoolie, Uncategorized

Cold Weather Care and Feeding of Batteries

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A recent discussion and some questions on the subject of batteries gave me the idea to sum up what I have on the subject in hopes that it will help other folks’ batteries to last longer.  For the RVer who wants to stay quiet, a good, reliable battery bank is the way to keep so many of those systems that make camping life so comfortable going, and most of us can’t afford and don’t want to buy those expensive new batteries often.

There are a number of strategies when choosing batteries for your RV/Camper.  Some people choose one single large battery, like this ‘universal replacement’:  This one has a rating of 200 Amp-hours (It would last for 200 hours under a constant 1 amp draw, or 1 hour at a 200 amp draw) at 12 volts DC, which is the usual power system for your regular vehicle and most RVs.

Some folks like to use golf cart batteries, as they can be obtained used, and even as 6 volt batteries, can be hooked up in series to make a 12 volt output and are often fairly cheap, like these (new): These, hooked up as two sets of series connections by a parallel connection would yield 140 Amp-hours at 12 Volts DC.

Now, the ones above are AGM (Absorbant Glass Mat) batteries. This technology became popular in the early 1980s as a sealed lead acid battery where the acid is absorbed by a very fine fiberglass mat, making the battery spill-proof, and means that it can be mounted in any direction. These batteries have very low internal resistance, are capable of delivering high currents on demand and offer a relatively long service life, even when deep-cycled.

AGM batteries are maintenance free, provide good electrical reliability, and are lighter than the flooded lead acid type (which I’ll mention in a moment). They stand up well to low temperatures and have a low self-discharge, but the major advantages are a charge that is up to five times faster than the flooded version, and the ability to deep cycle without ruining the battery. AGM batteries offers a depth-of-discharge (DoD) of 80 percent, while flooded batteries are specified at 50 percent DoD to attain the same cycle life.  The downsides are that they tend to be heavier/bigger per Amp-hour and higher costs than flooded batteries.

A flooded battery might be a cost- and weight-effective choice, looking something like this one: This battery would give 150 Amp-hours at 12 Volts DC, but with a smaller, lighter battery.  The downside of this battery is that you have to make sure the battery is topped up with distilled water, as it will off-gas explosive hydrogen gas and other corrosive gases (so it has to be placed in a vented compartment). You can get around some of the work of topping your battery(ies) up with an automatic system like this one which makes it a simple job with a a hand pump to fill once you install the hose to each of the cells of the battery(ies).

Another problem with flooded batteries is that a full discharge (50%) causes strain on the battery, and each discharge/charge cycle permanently robs the battery of a small amount of capacity (Unnoticable at first, but each subsequent discharge takes more capacity from the battery). Most of the flooded types will have a life of about 200-300 cycles, while the Lifeline batteries that we got are rated for 1000 cycles.

When it comes to cold weather, AGM batteries have another couple of advantages over flooded batteries in that they are much more likely to survive a freeze intact, and loose less of their charge over the same length of time.  This last is probably the most important of the two, as the trick to keeping a battery healthy over cold weather is keeping it charged.

As the weather gets colder, the effective Amp-hours in a battery drops, while at the same time, its voltage capacity rises.  This means that your charger has to be able to cope with this.  There are a number of ‘Smart Chargers’ out there, like these: 

or as units built into converters like this

The thing about these ‘smart’ chargers is that they will automatically detect the charge that your battery has and adjust their output to give your battery what it needs, from ‘bulk charging’ (up to almost 90% charge) through the ‘absorption charge’ (to charge the last 10-15% of the battery) to ‘float charging’ (which keeps the battery full at a constant lower voltage) and even the maintenance cycle of ‘equalizing’ charging (which highly charges the battery to prolong the battery life by removing sulfur from the plates).  A regular charger like you might have in the garage for your  car generally has settings for either a ‘starting charge’ (lots of amps you use to try and get the car started with a dead battery), a ‘bulk charge’ (To bring the battery to a full or near full charge), and a ‘float charge’ (to keep the battery full), though it doesn’t pay any attention to the battery that it’s connected to and continues to do what the switch is selected to, which can easily over-charge a battery and leave you with sulfur corroded plates.

Some people winterize their system by removing the batteries from their RV/campers, and keeping them warm. This is a perfectly acceptable way to winterize, but for batteries with larger Amp-hour capacities (and especially those that are heavier AGM batteries or built into specialized compartments) this can be a lot of work. You still have to remember to keep the batteries charged, or you might lose a cycle of life through discharge as they sit.  Also, if you have the flooded batteries, taking them out is a great time to top them up, and pay more attention to keeping them charged, as they’ll discharge faster than the AGMs.

Also, if you’ve heard that you can’t store your batteries on concrete over winter, as long as your batteries are in a plastic case, you can disregard it.  This adage comes from the time when batteries were produced in wooden cases, and the wet wood sitting on the porous concrete meant that the concrete would slowly leach away the water from your battery.  The only concern with modern batteries is if you can get your fingers underneath to lift them back into their places so you can get going again in the warmer times of the year.

 

 

 

Appliance, Electrics, school bus RV, Skoolie

iLLumi Projections E26 Edison DC 12V-20V LED Light Bulbs *or* Electrics (Part IV)

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Barring the installation of the DC circuit breaker panel that I mentioned before, I went about installing the first 12 volt DC light that would be powered by the house batteries.  The need for this was displayed on a short day-trip we took to help a friend clean out her old family’s house, and the boy was unable to read, and I had some trouble finishing loading and packing the bus because the lights that I had installed were AC, and I hadn’t enough cable to run electric power from the house we were cleaning.  I wasn’t going to just leave the key in the accessory position for the interior lights, because I’m a bit touchy now about running the bus batteries down after our Evangola trip.

Anyhow, I had found two of these lights at Buffalo Reuse, though only one of them had its glass globe, and they both had the original 1920-30’s fabric-coated wiring.  Toward that end, I disassembled the fixture, replaced the old wiring with 14-gauge plastic-coated wire, and installed a new light bulb socket.  (A tip to people who might want to try rewiring such a fixture – use a ball pull-chain as a wiring snake to get the wire through those support tubes.)  In retrospect, I probably could have used 18 gauge wire, but I tend toward overbuilding anyhow.

Unfortunately, the ‘cup’ that holds the globe was lightly cracked and I haven’t been able to find a replacement, as it’s smaller than standard.  It’s a usual thing for such lamps, however, as the older brass gets brittle.  I decided that it would be okay, though, as I was going to cushion the cup anyhow, so I went about that.  I used some vinyl electrical tape to circle the interior of the cup, and then to surround the base of the globe as well, as this would keep road vibration from causing any problems.  I then went about gently scraping all the old paint flecks from the brass and glass.

However, getting the light refurbished was the easy part.  I wanted the light to rest above where the table will be in the cabin area of the bus, and the ceiling there is, of course, curved.  I wanted to have a flat base (parallel to the floor, that is) to mount the light to, and I had the wood to work with, but the curve looked tricky.

The endcap!As a woodworker, I knew the importance of having a jig or template to help and didn’t want to do the ‘trial and error’ method of creating one, until I realized that I had one already – the rear interior endcap!

I used some MDF that I had about, and traced the endcap, and cut it out, making sure to draw on plenty of lines at 90 degree angles to the flat base of the endcap.  These were important, just in case the smaller bit of the template (where the MDF wasn’t wide enough to fit the whole of the endcap might not be exactly parallel to the base) …

So, armed with the new template, I worked out how far from the window edge the light needed to be and set about making a base that would fit the light AND the ceiling.  I had some 7/8″ thick oak to work with and cut it to 5 1/2″ squares, and traced the curve onto one.

Careful cutting on the bandsaw, and then shaping with the bench sander yielded a very nice fitting piece of curved oak.  A 2″ forstner bit cut a smooth access core down through the curved wood, setting the stage for the important attachment bit for the light fixture; the part with the screw fitting on it.

The ‘light fixture mounting attachment’ needed to be sunk into the wood, parallel to the flat base, and this was quickly undertaken with a wood chisel.  Since I was working with oak, and going with the grain of the wood, this wasn’t bad at all.

I put a second piece of oak under the curved one to give a nice solid base for the lamp.  I did this because the thin edge of the curved piece I had cut was really thin.  I was afraid that if I just attached the lamp to it, it would crack or pull the attaching screws right through the wood.  Plus the routing on the bottom would be another nice touch of decoration that would show in the bus.

Using a countersinking bit I put four #10 screws into the two pieces of oak together, and drilled some holes through to the bottom and countersunk from the bottom for the metal pan-head screws that would attach it to the ceiling.  I then gave it a coating of stain and let it rest while getting the rest of the job ready.

 

 

 

 

Loading a drill just smaller than the metal screws that would affix the wood to the ceiling, I pre-drilled one hole, and marked the center of the access channel in the wooden base.  I then switched to the hole saw and cut through the metal of the ceiling to so the wires could be run.

Using a regular wire snake to run the wires, it was a simple thing to get power to the location.  I ran 12 gauge wire from the converter to where the switch was going to be at the windows, then ran the 14 gauge wire from there, as I planned on hooking more lights in on this same circuit.

While I’m really looking to run some manner of dimmer in on this circuit, for now, I just put in a pull-switch.  It was easy to drill a hole in the exposed ceiling sheet metal, and for now the circuit is grounded to the frame.

After that, it was a simple matter of connecting the wires at the lamp, and tightening the screw pole to cinch it up to the wood.

 

 

In trying to make the batteries last as long as possible, I wanted to have the most efficient lighting that I could, and went for some LED lights.  Most of the problems with LED lighting seem to be in that the LEDs only put out light in a relatively tight beam, making them tough to use in a standard fixture.  Toward dealing with this, I found this multi-directional style of bulb, in both 7 and 9 watts:

I have to say that these are SUPER bright on 12 volts, and while they say that they’re rated up to 24 volts, I don’t think I’d want to see them – they’d be way too bright.  As it is, the bulb does stick up over the globe a little, but the upward-facing LEDs provide a lot of indirect light off the bus ceiling (and show the places where it really needs to be cleaned!).

These bulbs are the soft-white version, and the vendor that I got these from indicates that there’s a bright-white version, but these seem very white compared to an incandescent, or even CFL soft-white bulb.  I did light them up when it got dark as well, and got these results:

Appliance, Skoolie, Uncategorized

The Norcold Refrigerator 876EG2 *or* Electrics (Part III)

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After getting the AC breaker box and converter installed and working, I set about getting our fridge in place and powered.  The 4-4 1/2 cubic foot fridge that we salvaged from our friends’ trailer was what we wanted in terms of a small three-way unit, but unfortunately, it didn’t work.  First, the controller card wasn’t responding, and even though the ammonia system was sealed and I could force the AC heating element to fire up and run, the fridge just wouldn’t cool.

Now, if you’re only used to our modern, AC, compressor refrigeration systems, the ammonia-based systems of a heat-powered system may seem odd. But they are super-quiet (aside from the occasional gurgle) and great for boondocking.

Here’s a nice introductory video on non-mechanical refrigeration systems:

If watching the video is too long for you, essentially the three-way (two electric heating elements or the LP gas heater) system works non-mechanically (no compressor to force-chill the liquid/gas coolant) to cool the interior of the freezer and fridge through heating ammonia to a gas, then taking advantage of the fact that it will condense back to a liquid and the chilled liquid ammonia will become the cooling factor for the freezer and the fridge.   Ammonia boils (and thus condenses back to liquid) at -28°F, which is more than enough to keep things freezing in the freezer.

Now, in getting a second-hand non-mechanical fridge system, there are some trouble-shooting things you need to do, unless the owner you’re getting it from can demonstrate that it definitively works.  One is to tip it on it’s back for several hours, then raise it up slowly.  This is done as an attempt to insure that all the liquids are back down in the reservoir so that the ammonia can be boiled off, and thus cool the interior of the fridge/freezer.  The other is to bypass the thermostat’s circuit board and put a heat source (like the electric heater that is installed on the unit or an LP source, like a low flame propane torch) to see if the ammonia will boil out and chill the system.

The most important part of the system is the cooling system, and many old fridges can be rehabbed by purchasing a new cooling system (most for around couple hundred dollars).  After I tested the salvaged unit for a couple of days and found no temperature change in the interior at all, I considered this, and started in to do my research, finding out that the shipping charges for these rebuilt/recharged systems can be costly.

It turned out that for us that a (relatively) local seller on Craigslist was selling a 6 cu ft Norcold Refrigerator (model 876 EG2) for about what it would cost for us to get the rehabbed cooling unit for the smaller salvaged unit.  And, the seller had it running and cooling when I came to pick it up, so I knew that it was good.  (He was also the one that threw the converter in for a song.)  This was a good deal, as a comparable new unit like one of these is much more expensive:   

The 876 model is a two-door unit, which was a change from the salvaged one, which had a small metal enclosure for the freezer that helped to cool the rest of the fridge.

The two door unit makes for a much more energy efficient and manageable freezer and fridge in terms of temperature.  You don’t get ice in the fridge area and the freezer stays really cold.

However, the 876 is taller and slightly deeper than the salvaged unit, which threw a bit of a wrench into my plans.  As you might remember from my floorplan, FloorPlans2 there was a covered window behind the fridge, as the fridge needed air space for the cooling vents, and for the heat and exhaust to be vented  outside in order to function.  One of the major reasons why absorption refrigerators don’t work has to do with insufficient ventilation and blockages in the heating system.

With the smaller, salvaged fridge, I had expected to cut vents into the skinned window and not have to cut the roof, even with the fridge sitting up over the wheelwell (I had expected to use the seat-rail as a support).  However, with the much larger 876, I would have to cut off the seat-rail, and rebuild the wheelwell cover in order to lower the fridge as much as possible, and then cut a vent hole in the roof.  I had also planned to cut vent holes in the floor to gain air flow and O2 for the LP burner, but with the depth and base construction of the 876, I wasn’t able to do that, so I would have to also cut into more of the skin of the bus in order to get good air flow (and I was nervous about both of these cuts, since I hadn’t done anything to the exterior up to this point!).

Now, I knew that the fridge cooled nicely on 12 VDC, and wanted to verify that it would run well on AC, and was upset when I plugged it in and got no response! But that was because the thermostat circuitry is all 12 VDC, and must have power to run so the AC can kick on the heating element.  Once that was rectified, I confirmed that the fridge would automatically switch from a DC source to an AC source (and back) when the AC was available for the heating element.  This is kind of a big deal as the electric heating elements are not as efficient as the LP burner, and when available, shore power is your friend for cooling.  The DC power is important for while you’re driving (and perhaps for regular running when all the solar panels get installed), and the LP is good for extended boondocking.

But before I could check and see if the LP worked, I had to replace the gas line from the solenoid and, as it turned out in dis-assembly and cleaning, a new burner.  The new burner was easily available  (though it used to cost less than it does now!) and needed a new compression fitting at the end of the tubing.

Luckily, I had bought a really nice set of tools for flaring compression fittings to redo the brake lines in my wife’s Daewoo, and it turned out that the gas line was a 5/16″ line that I had a bunch of, so I cut and formed up a new line that sealed up nice and tight, and all worked well.

Unfortunately, as the 876 had been pulled from an RV that had been sitting unused, it was from a unit that had been built in the late 80’s or early 90’s, and had this horrible beige padded covering that stuck out and made the fridge even that much bigger.  I had examined the doors and found that the hinges could not only be moved to the right side (from the left where they had been), but also that with the removal of one of the edges the padded facing could be easily removed and replaced with some stained oak plywood, which fit a lot better with our overall look.

I trimmed the existing wheelwell covering and removed the pieces that held it up.  Some 2×3’s built up a new floor for the fridge and then I could measure for the area that it would need for the air venting intake and then the hot air exhaust.  These presented some problem as the opening I wanted to cut would have gone right through one of the rub-rails.  I wanted to preserve these as much as possible so that the bus would keep as much of it’s structural integrity as possible.

To deal with this, I cut the skin between the rub rails to get the opening necessary for the air flow.  This was reckoned from the venting salvaged from the old trailer.  I ended up cutting down the locking casing for the smaller area so that I could get in and clean out the burner, then cut the vents so that the upper area could be screwed in place and sealed.  This makes it removable if necessary, but not with the ease of access of the lower area, yet also keeps the rub-rails intact.

For the top, I, with no small amount of trepidation, cut into the roof.  Three cuts allowed the roof to spring up above the reinforcing plates inside, and two triangular metal pieces for the sides created a nice opening for the heat to exit the bus and create a nice draft to pull cool air over the cooling fins of the fridge.  It has window screen over it to keep insects out, and will (eventually) get a nice sheet metal cover to keep the rain out.

Inside, the air was channeled to the outside by some wooden ducting, sealed with weatherstripping and screwed in place.  The actual flue from the LP burner would run up against the metal, keeping the burning hazard at a minimum, and allowing for plenty of air movement.

Wires were run for the DC and AC power sources and the fridge now runs like a top, even bringing some pop-ice sticks to a frozen state within a few hours.