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'73 Concord 20' Class A w/Dodge 440 - see profile for photo
Griff in Fairbanks wrote:
I was starting to think I was spitting in the wind and wondering if I should continue.
I'll get to chargers soon, in a future post. Until then, yes, you DO want a smart charger, as long as it comes from a reliable manufacturer. You want a multistage charger, with at least three stages, and some knowledge as to how to best use it.
For now, I'll let the cat (part way) out of the bag. Motor vehicle charging systems are merely okay for maintaining a battery. To keep your battery in top condition and extend it's life, you also need to use a good quality multistage smart charger and use it properly.
I was starting to think I was spitting in the wind and wondering if I should continue.
I'll get to chargers soon, in a future post. Until then, yes, you DO want a smart charger, as long as it comes from a reliable manufacturer. You want a multistage charger, with at least three stages, and some knowledge as to how to best use it.
For now, I'll let the cat (part way) out of the bag. Motor vehicle charging systems are merely okay for maintaining a battery. To keep your battery in top condition and extend it's life, you also need to use a good quality multistage smart charger and use it properly.
Definitely not spitting into the wind. I appreciate the info, and will try to read your post on chargers.
Downsizing ">
I finally had a chance to do a little testing on my DC problem, and have narrowed it down to one wire. Unfortunately, the 'hot' seems to have shorted out somewhere.... Dang it. There is maybe a foot of it visible before it disappears into the wall and routing to the opposite corner of the RV. Taking suggestions as to what might be the best way to get a new wire to the destination. Anyone with experience with this?
Sometimes you can securely attach a new piece to the old and pull it through, but if it's stapled along the way you can't do that.
eyeteeth wrote:
I have been printing the information off to reference later... Good info.
I finally had a chance to do a little testing on my DC problem, and have narrowed it down to one wire. Unfortunately, the 'hot' seems to have shorted out somewhere.... Dang it. There is maybe a foot of it visible before it disappears into the wall and routing to the opposite corner of the RV. Taking suggestions as to what might be the best way to get a new wire to the destination. Anyone with experience with this?
I have been printing the information off to reference later... Good info.
I finally had a chance to do a little testing on my DC problem, and have narrowed it down to one wire. Unfortunately, the 'hot' seems to have shorted out somewhere.... Dang it. There is maybe a foot of it visible before it disappears into the wall and routing to the opposite corner of the RV. Taking suggestions as to what might be the best way to get a new wire to the destination. Anyone with experience with this?
It's more likely a break in the wire if you're not blowing fuses/circuit breakers. (It could be a unprotected circuit, in which case the wire will be getting very hot and may act as a fuse by burning up.)
Leeann's suggest is probably best. However, what I do if I want to still use the same routing is use the old, suspect wire as a "fish" tape. Firmly tape the new wire to one end of the old wire and CAREFULLY use the old wire to pull the new wire through the confined spaces.
I emphasis carefully because, if the wire is indeed broken, the insulation is the only thing holding the length together. Also, you're probably going to run into considerable resistance as you pull the wire around corners and through tight spaces.
If the old wire comes out without pulling the new along with it, you pulled too hard or the wire was completely broken, insulation and all. If the wire was on an unprotected circuit, an actually short may have caused the wire to burn through.
Melted metal and charred, blackened insulation is evidence of a short-induced melting. Discolored insulation by itself might indicate current was kicking off heat trying to jump across a small break in the wire, especially if the insulation is otherwise intact.
If the new wire doesn't follow the old wire, you'll have to use an actual electrician's fish tape or, more likely, follow Leeann's advice.
When you get the old wire out, examine it for abrasions on the insulation that indicate it was rubbing against a sharp edge, eventually leading to a short. (2004 Chevy 2500HD Silverados is one case i know of where this is a known manufacturing problem/defect.) In this case, you'll want to reroute the wire if you can't get at and fix whatever is causing the abrasion.
In any case, it'd be a good ideas to make sure the circuit is protected by a fuse or circuit breaker. With the exception of some parts of the starting system, every circuit should be protected. Best practice, as codified in current marine wiring standards, mandated a fuse or circuit breaker within seven inches of the circuit's power source.
I'll explain why parts of the starting system are exempt from circuit protection in my next post.
1970 Explorer Class A on a 1969 Dodge M300 chassis with 318 cu. in. (split year)
1972 Executive Class A on a Dodge M375 chassis with 413 cu. in.
1973 Explorer Class A on a Dodge RM350 (R4) chassis with 318 engine & tranny from 1970 Explorer Class A
Leeann wrote:
Try to figure out a different routing of the wire that's both safe and easier to maintain.
Sometimes you can securely attach a new piece to the old and pull it through, but if it's stapled along the way you can't do that.
Try to figure out a different routing of the wire that's both safe and easier to maintain.
Sometimes you can securely attach a new piece to the old and pull it through, but if it's stapled along the way you can't do that.
Stapling usually should only be done on the solid, single-strand wires used on 120/240VAC systems, just like in houses. (These wires need to be fastened at regular intervals to keep them from flexing, which could lead to stress-induced breaks.)
12VDC circuits in motor vehicles should use stranded wire, which can stand up to vibration and flexing better than solid wire. Securing these loosely at periodic interval is a good idea to limit movement. However, surrounding structure is often enough to limit excess movement so many manufacturer forgo staples.
In some cases, the wrong type of staples (i.e., cheap staples) actually cause more problems than they prevent. In these cases, vehicle vibration causes the staple to cut through the insulation, resulting in a bare wire that could lead to a short circuit.
Leeann wrote:
All true but doesn't stop them from doing it.
All true but doesn't stop them from doing it.
That, along with the weird and wonderful things previous owners have done, is why I prefer to rewire part or all of old vehicles I'm rehabilitating. (In one case I ran across, I swear one circuit had electrons running around in a perpetual loop ... somewhat like the plumbing "fixes" my father did.)
Almost all motor vehicle batteries currently on the market are lead-acid batteries, with only relatively minor differences between the various types. All brands are effectively the same, with differences mostly limited to price and quality control.
Although based on old technology, with minor improvements over time, lead-acid batteries still provide the best available balance of availability, functionality, performance, and price. Less common batteries with different types of chemistry likely provide a less than favorable price/performance balance. (We are, after all, just trying to get to and from places that are, at most, a few hundred miles away. In particular, we're not trying to get to the moon and back.)
Gel batteries are best in certain specific circumstances but are general not suitable for motor vehicle use. (I will get to discussing where gel batteries might be best in a motor vehicle … and what you need to use them there.)
AGM batteries cost more but are arguably your best choice.
Flooded batteries are just fine, with a caveat related to VRLA and non-VRLA versions.
Non-VRLA batteries, which are basically limited to flooded batteries, are fine if you're willing to faithfully perform the routine periodic maintenance they require. (Non-VRLA batteries are usually called open-cell batteries.)
If you're the type of person who only checks their tire pressure once a year or less, you're better off with a VRLA batteries. (VRLA batteries are usually called maintenance-free or sealed batteries.)
Size (i.e., BCI Group designation), price, and ego are important considerations when choosing the battery that's best for you.
There is one difference that's very important when choosing batteries for our motorhomes: Starting versus deep-cycle batteries.
Side note: In the process of writing my electrical system ramblings, I've been researching the subject to make sure the information I provide is reasonably accurate and up-to-date, instead of relying solely on experience and memory. (Actually, this research is directed towards designing an electrical system for the boat I'm building that is reliable and does what I need … this research provides a sideways benefit to my ramblings.)
In this research, I've been relying heavily on marine electrical systems information, recommendations, and standards. Motorhomes and boats have similar electrical system features (such as dual battery banks) and share many common needs and issues. The reason I'm relying on marine information is boats operate in a somewhat more dangerous environment than motorhomes, which presumably results in more precise and reliable recommendations and standards. As a result, we can take "lessons learned" from the marine industry to improve our motorhomes' reliability and operation. This is especially important for our older motorhomes because they were produced close to the dawn of the motorhome industry, when there was very little experience and even less standards. (see https://en.wikipedia.org/wiki/Travco)
One very interesting bit of information I ran across was issues with the current standards for rating batteries, such as cold cranking amps (CCA). CCA, for example, is a measure of the number of amps a battery can deliver at 0°F for 30 seconds without dropping below 7.2 VDC. Average people cannot be faulted if they think this measurement would show up as a flat, horizontal line on a graph. (And, unfortunately, this may very well represent the test less than reputable battery manufacturers use to arrive at their CCA ratings.)
People with a good understanding of engine starting systems know an actual chart of starting system demand is a curve, starting with high amps and dropping down as the engine begin rotating. As it turns out, this view of the curve is also somewhat erroneous. (This included my prior understanding of starting system demand.)
Blue Sea Systems used refined test equipment, capable of very rapid time-slice sampling, to measure actual starting demand on a variety of marine engines under real world conditions. In spite of my understanding of variables in scientific measurement, I was very surprised by the results.
This demonstrates an ongoing problem with all fields of engineering and standardization. To avoid a lengthy (lengthier?) explanation, I'll use gas consumption as a metaphor. My 1990 Ford E150 van, with an inline 300 cu. in. engine, uses an average of less than five gallons of gasoline per week. Before you get jealous, I should point out the van only gets used once or twice a week for trips totaling less than ten miles and trips once or twice a month around 70 miles each. (This is why motor vehicle ads say, "Your mileage may vary.")
While Blue Sea used a variety of engines, it's my impression they used a large diesel marine engine as the most extreme example. (Makes sense, large diesel engines are notoriously difficult to start.) Blue Sea's tests indicate the greatest demand occurs almost immediately, when the starter has to overcome the engine's inertia. Their tests show this initial spike in peak starting current can reach as much as 1500 amps. This huge spike is part of what they call the Inrush Period, lasting approximately 1/4 second.
The graph they provide on their website shows an immediate spike of 1250-1300 amps, dropping quickly to 800 amps in a few hundredths of a second. The curve then slows, dropping to 600 amps in roughly 0.16 seconds, before showing a secondary spike reaching almost 800 amps that may represent engine resistance due to a cylinder compression stroke.
After the secondary spike is a relatively smooth curve representing a rapid decline in demand changing into a slower decline. Blue Sea calls the period following the secondary spike the Cranking Period, comprising the time from when the engine starts rotating freely and is finally running on its own, which averages 9-3/4 seconds.
WOW!!!
(And, "Whew!" Sorry, my scientific background got the better of me, leading to a description that might be a bit more detailed than necessary.)
At this point, you're probably wondering how a battery rated, for example, at 800 CCA can produce that much current. Remember, CCA rating is a measure spanning 30 seconds, which is roughly 750 times as long as the initial spike described above. The arithmetic mean (average to non-mathematical folks) for the first 10 seconds of Blue Sea's graph is roughly 800 amps, with the graph dropping to 200 amps a little before the 11 second mark. Also, the alternator has probably taken over and started recharging the battery well before the end of the CCA rating's 30 second period.
Simply put, motor vehicle batteries, as well as most electrical wiring and components, can handle short duration surges in excess of their rating. (Blue Sea's largest battery switch, designed for diesel engines, is rated at 600A continuous and 900A intermittent, using the current UL standard for these switches.)
Blue Sea calls the combination of the Inrush and Cranking periods the Engine Cranking Cycle. Based on their research, they established an Engine Starting Standard, which is being consider for incorporation into American Boat and Yacht Council (ABYC) standards and is already being referenced by a significant portion of the marine industry.
Okay, what started out as a side note turned into a description of what happens in a engine starting system and became longer than expected. So, I think I'll have to put off starting vs deep-cycle batteries for my next post. (At least, this post laid the groundwork for that discussion.)
BTW - I'm writing these using on-the-fly, stream-of-consciousness. I try to do some proofreading and editing before posting but typos and confusing sentence syntax does slip through. (It doesn't help I grew up in northern Minnesota, where "throw the cow over the fence some hay" syntax was common … uff-da!)
When you rewired... say... your MH. Did you try and pull a new wire through the old path? (Say... using the current wire) Or, did you reroute a new wire? I know what end result needs to be, but don't have the experience to know the best path to take. (Thanks)