Convertor Questions

[Pete D]

It's not a contest, it's an exchange of information and we all learn in the process.

DIODES

According to this WiKi page on diodes, "While standard silicon diodes have a forward voltage drop of about 0.6 volts and germanium diodes 0.2 volts, Schottky diodes voltage drop at forward biases of around 1 mA is in the range 0.15 V to 0.46 V, which makes them useful in voltage clamping applications and prevention of transistor saturation.", so again unless we KNOW which diode is in play or we put a VOM on it, we don't know the voltage drop.

If only .15V and zero wire loss, we get a little over 80% charge; if .46V then we only get about 55% on an FLA battery (see below). Neither of these is acceptable to me, esp considering the cost of a diode isolator vs a relay...

However, I DON'T know what other magical components/circuitry there may be potted up in that black box to compensate for the various diodes' characteristics. Only way to really know is hook one up in a charging situation and measure the voltage difference between input and output with a good VOM.

I'll also fall back on the advice of folks on other RV lists, the guys with the BulgeMobiles who carry two, four or even six 6V golf-cart batteries, and the electronics geeks who know a lot more than I do about theory and they all seem to choose relays over diode isolators.

WIRE GAUGE

I believe 10g is not adequate, except for very short runs, because that's what started this current thread -- We apparently have a battery (AGM) that will accept a lot of current and a charging system that will provide same, connected by a wire and fuse that seems too small -- Looking at the cabling chart in the Intro... PDF, 10g is only good up to 12' for 40Amps.

Last time I went to an RV show, I noticed that the travel trailers were now using either 8g or 6g for the 12VDC connections to the house battery, where in prior years they were typically 10g.

PARALLEL CHARGING

Batteries in a bank should indeed be as identical as possible, but batteries separated by wiring don't seem to suffer as much in use according to what I've read and experienced.

It does occur to me that if the wiring is so oversized that the two batteries appear electrically side-by-side there may be problems, esp if one is an AGM and very discharged. If I had that situation (and I won't unless the price of AGMs comes down quite a bit), I would have a way to disconnect the house battery until I had the engine up and running and could leave it that way for a while.

RELAY

I'm not sure I buy into the "copper coils in the relay" messing with the charge. Seems to me that a proper design would account for that.

I do believe the relay should be sized for handling a constant heavy load consistent with the alternator's output.

 

[Pete D]

I just read the following on a Ford F-series Camper Relay thread on the Truck Camper Forum of RV.NET, where a discussion is going on about isolation, and this makes some sense to me and explains how the diode isolator, PROPERLY INSTALLED, can give a full charge without worrying about the diode voltage drop. Unfortunately, it does involve messing with the truck's wiring and may or may not interfere with something.

QUOTE
The isolator needs to go in the alternator output wire. It has a diode to both the truck battery and camper battery. That puts a .7V drop in both lines. The voltage regulator will adjust up the output and both batteries will get a proper charge.
END QUOTE

To work as stated, it seems to me that there must be a way for the regulator to sense the truck battery voltage(es?) directly.

BTW, one person said the Ford relay in 2003 was designed to handle 20Amps.

 

[S.C.M.O.D.S.]

Hey Pete, thanks for answering some of the questions I had related to using a cig lighter port to power an inverter to power a 3-stage charger to properly charge my AGM.

I guess I'm essentially in surfib's situation where I have an old isolator that came off the previous truck. To get things up and running, I guess I'll just install that and replace all the wiring that's still hooked to it (I kept it all connected and labeled it all saying what was connected to what so I could work backwards to set it up on my own rig).

So do you guys indeed think that 10 gauge wire is sufficient or should I go with 8? The distance looks to be in the neighborhood of the 12' discussed earlier.

As far as using a 3-stage charger to properly charge my AGM w/ my truck, from what I understand the only way to do this would be to have dedicated wiring running from the alternator (or the windshield wiper motor like in the setup that uses the isolator) back to a properly sized inverter that sits near a 3-stage charger (anything smaller than a Vector?) which is then plugged into the AGM.

However, since the number of components has increased the likelihood of failure has also increased. So I would still have the original isolator setup in place in case the inverter or charger were to fail.

This may all seem convoluted/overkill to properly charge a battery, but if set up right, I could use both the inverter and charger for other batteries/applications as well. And like I said, I plan on just mimicking the setup that was on the truck I got my camper off of as I learn more.

My understanding of electrical systems is minute and I really appreciate the time everyone spends answering questions and sharing their knowledge. True I could get my baby professionally wired up, but when something goes wrong I want to understand it and there is likely not going to be anyone around to help me fix it. So I'd rather learn to fish as they say. Once again all advice is highly appreciated and in the unlikely event in which I can reciprocate, I will.

One other side note: I think it would be kinda cool if w/in this site there could be an area that listed a set of systems/types of add-ons or equipment that are in consensus agreement by the members of the site to be the best setup running for most applications. For example, providing electrical power to your camper, type of jacks (brand and mechanism), roof rack, hitch cargo platform etc... You could go to the page where categories like these would be listed, click the jacks link for example and it would open up a list of types of jacks. Each type could be voted on by members w/ a thumbs up or down and comments/experience could be listed by members as to why they voted the way they did. Each jack type would have a cumulated score of thumbs up and down to give the reader a quick place to get aggregate understanding of the goods and bads of stuff based on the vast experience of those who know (namely you guys and eventually me) I think something like this could be even more valuable to newbies like me when the number of posts to this site keeps growing and you search for something like "jacks" and get 20 pages of different threads that might have the word jack in them but have nothing to do with selecting the best type of jack setup for you & yours. Just a thought.

P.s. I've read about solar panel use, but has anyone heard of someone using a wind generator on one of these babies? I have a feeling the wind might be more reliable for me in Alaska from Jan-June than the sun.

 

[surfib]

One other side note: I think it would be kinda cool if w/in this site there could be an area that listed a set of systems/types of add-ons or equipment that are in consensus agreement by the members of the site to be the best setup running for most applications. For example, providing electrical power to your camper, type of jacks (brand and mechanism), roof rack, hitch cargo platform etc... You could go to the page where categories like these would be listed, click the jacks link for example and it would open up a list of types of jacks. Each type could be voted on by members w/ a thumbs up or down and comments/experience could be listed by members as to why they voted the way they did. Each jack type would have a cumulated score of thumbs up and down to give the reader a quick place to get aggregate understanding of the goods and bads of stuff based on the vast experience of those who know (namely you guys and eventually me) I think something like this could be even more valuable to newbies like me when the number of posts to this site keeps growing and you search for something like "jacks" and get 20 pages of different threads that might have the word jack in them but have nothing to do with selecting the best type of jack setup for you & yours. Just a thought.

I agree! That would be a cool thing to add!

As far as everything else goes, I'll go with 8 guage wiring, the standard solenoid, I just ordered the Iota, and hopefully the instructions will answer my questions. My budget is helped by the fact that my work has a port supply account with West Marine so I spend ALOT of time their, infact I just rewired a good chunk of my wiring due to the previous owner deciding it was easier to run the wire outside of the camper than to drill a few more holes and run it inside!

 

[S.C.M.O.D.S.]

Yeah, I think I'll likely go with the 8 gauge myself. I got the day off tomorrow so I plan on going to west marine to get the wire I need to set it all up. I currently live in an apartment w/ no garage and room for few tools. It'll be an adventure, but hopefully it will go well b/c I need to make sure my heater still works!

Surfib, what Iota converter are you going w/ and are you getting the 3-stage charger option w/ it? Yeah, I think my suggestion would really be helpful for this kind of stuff. I could look up which batteries, converters, inverters, magazine holders, lighting and on and on so much easier. I think it could be great but it might be really hard to set up Good luck w/ your setup

Also, the old isolator and thermal breaker I've got from the previous owner still look good, I don't need to buy new ones do I? Can anyone confirm that?

 

[flinchlock]

It's not a contest, it's an exchange of information and we all learn in the process.
I am sorry I gave the impression this was a contest on my part.

Since I am investing $13,000 for a bed on wheels, my nature is to research and understand so that I do not have to spend more money and more time down the road to redo/fix stuff. At my stage in live, my choice is to spend my money correctly up front.

I strongly believe in Proof of concept. It is not that I do not believe anything someone tells me... I must also understand what information I am given. The "just trust me" words or tone drive me to the point of exhaustion researching.

Just to add more fire to this thread...

Hellroaring Battery Isolators have a 0.001 volt drop.

Here is a comparison chart between the various systems/methods we have been discussing.

Mike

 

[surfib]

I'm going with the DLS-30 with the "smart" charger add-on.

 

[EdoHart]

Hellroaring BIC-95300

I have one of the BIC-95300 isolators and really like it. It might be a bit much for any one that just wants to power the camper, but the way I use the truck it's very nice to have a backup starting battery. I've drained the primary enough to just get clicks out of the starter, throw a switch and it starts right up.

BTW,
S.C.M.O.D.S. = State, County, Municipal, Offender Database System?
"Oh merciful mother of acceleration, don't fail us now."

 

[surfib]

My problem is if I run my batteries down on my truck, I'm pretty screwed, the starter on my truck is 24 volts, and it needs all the cranking amps it can pull from my 2 1000cca batteries as it can get. It spins my engine at least 300rpms as it spins. I've run them down before, and jumping the truck was a no go, almost stalled out my tahoe when I turned the key, and dont forget I have to fight the glow plug relays pulling amps as I start!

I would rather not give myself a reason to be able to connect the batteries!

Mike

 

[Pete D]

The Hellroaring isolators look like the right stuf to me.

Guys, also keep in mind that sometimes "good enough" is indeed good enough. If one is only occasionally boondocking without shore power or generator or solar, and not using the power-sucking stuf like the furnace or reefer in 12VDC mode, one can get by with a lesser charge in the house battery as long as one does hook up a smart charger (or monitors a manual charger carefully) to the battery at home. What seems to permanently hurt a battery, esp a starting-type battery, is to be significantly discharged and then not recharged at all for long periods.

If running new wiring, I would go with the heavier gauges, but 10g gauge should be "good enough" for typical use, esp with flooded lead-acid batteries and long drives.

I suspect that the early isolators were just diodes and that's where they got a bad reputation from, however, there are likely still some out there, so regardless of what you install as an isolation system, be sure to check the outgoing voltage with a VOM.

 

[Everett]

Solar Battery Charger

After an extensive research, I decided to use the "Optima" 12 volt Deep Cycle Battery and A 12 volt 20 Amp Solar charging system------I am very pleaased-----I've tried to keep all batteries separate----and avoiding all propane systems--------the new solar capabilities are super-----Everett

 

[S.C.M.O.D.S.]

Hey EdoHart,

Sorry 'bout the delayed response, I didn't see your post until now (9/25/07 22:59). Does "It's 106 miles to Chicago, we got a full tank of gas, half a pack of cigarettes, it's dark, and we're wearing sunglasses." answer your question? Next time your wife, girlfriend (or partner, nothing wrong w/ that of course ) complain that you'll never watch a musical w/ them just throw in a little Jake and Elwood. It technically counts as a musical. Cheers!

 

[EdoHart]

Sure does

"The Blues Brothers" is still on my list of top 10 all time greatest movies. The problem with watching a movie like that with someone who hasn't seen it before is that I keep snickering before the punch line. I like the musical angle, never thought about that - I'll remember it the next time it comes up.