sgaskill
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Post by sgaskill on Apr 14, 2016 19:04:47 GMT -8
Hi all, I am restoring a 1965 18 ft FAN camper. I just started the process of completely rewiring it with AC and DC. I've bought an isolater, and a 1500 watt pure sine inverter. I've looked at a few schematics and see a "transfer relay". What exactly is this and is it necessary? Also I am looking to buy a converter/charger (3 stage). Is there any special kind I should be looking at (size etc.)? Thanks for any information you can give me. Scott
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Post by vikx on Apr 14, 2016 20:28:17 GMT -8
Welcome Scott!
I have had good luck with Progressive Dynamics converters. They have a "smart charger" and are kinder to batteries than some. You shouldn't need a huge converter, 30 or 45 amps is sufficient. You can get lower amperage converters, but they cost the same, so no sense going there.
As far as the transfer relay, I believe it is for a generator connection, but not sure. Many modern motor homes run on big battery banks and large inverters plus the generator. The relay prevents two AC sources from entering the AC distribution panel at the same time.
Keep in mind that little trailers do not have much space and don't like extra weight, so a battery bank is not always possible.
Hope this helps. Elaborate systems are not usually installed in vintage trailers. I think solar charging might be something to look into if you plan on boon docking.
I'll be moving this to our electrical section, scroll down and you'll find it.
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sgaskill
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Post by sgaskill on Apr 15, 2016 4:28:36 GMT -8
I plan to do a lot of boon docking. Was going to buy 2 6v golf cart batteries. And I have a tiny generator that i'd use only for emergencies. And I do plan to buy a couple solar panels too. If I don't use a generator then it sounds like I may not need the transfer relay. Thanks vikx
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cowcharge
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Post by cowcharge on Apr 17, 2016 1:38:38 GMT -8
When you say "isolator" do you mean a battery isolator switch, to charge while driving? Make sure you run a big enough wire so that the amps actually make it all the way to the camper.
Using your generator to run a converter is very inefficient, you'll be running it all day and it still won't be fully charged (check it with a hydrometer to see for yourself). Converters make good 12v power supplies when on shore power, but they're not very good battery chargers, they take way too long, if ever, to get a full charge into the batteries. And generators are already one of the most expensive ways to get power, but if you must, it's best to go right from the 12v output of the gen to the batteries, you'll get the same amount of charging done in half the time.
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sgaskill
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Post by sgaskill on May 5, 2016 14:42:21 GMT -8
When you say "isolator" do you mean a battery isolator switch, to charge while driving? Make sure you run a big enough wire so that the amps actually make it all the way to the camper. Using your generator to run a converter is very inefficient, you'll be running it all day and it still won't be fully charged (check it with a hydrometer to see for yourself). Converters make good 12v power supplies when on shore power, but they're not very good battery chargers, they take way too long, if ever, to get a full charge into the batteries. And generators are already one of the most expensive ways to get power, but if you must, it's best to go right from the 12v output of the gen to the batteries, you'll get the same amount of charging done in half the time.
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sgaskill
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Post by sgaskill on May 5, 2016 14:49:30 GMT -8
The isolator i have is to prevent the truck battery from being drained by the coach.
What size wire would he recommend I use from the alternator to the coach batteries to charge during travel? My batteries are in the back of the coach rather than the front so its quite the distance from the alternator.
Also I didn;t know about the converter taking to long to charge full. The one I bought is 45 amps. Do you think an upgrade to a 60 or even 100 would charge a lot more effeciently?
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Post by vikx on May 5, 2016 20:54:55 GMT -8
Agree on a genny not being very efficient for charging batteries. Solar is better. The vehicle would charge on the road. I would go with minimum 10 to 12 gauge wires from the front of the trailer to the back. Also, the vehicle may need a larger output alternator and decent gauge wire to the 7 way receptacle. Something to research on your truck/car/SUV.(the 7 way cord uses a 10 gauge charge wire)
I don't believe the higher amp converters have any different chargers. The only difference would be a "smart" charger verses one that might overcharge your battery(s). I would be sure the converter you buy has a smart charger/maintainer.
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sgaskill
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Post by sgaskill on May 6, 2016 15:25:56 GMT -8
the charger/converter i bought is 3 stage "smart" one. I read about the higher output vehicle generators. I buy the truck next year so something to consider. Thanks about the gauge wire being 10 from generator to the 7 way. I had another question. How do you know how charged your house batteries are? I know you can infer the % based on the voltage output at the battery. Like 12.09 v is about 50% capacity (and I know its not good to let it get below 50% very much). Is there a gauge you can buy to install inside camper to tell?
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Post by vikx on May 7, 2016 23:24:38 GMT -8
Basically, the charge is determined by the smart charger. It's charging about 13.5, and quits at 14.3... There are basic meters available that tell you charge state of the battery.
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sgaskill
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Post by sgaskill on May 8, 2016 10:59:14 GMT -8
Good to know. Thanks
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cowcharge
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Post by cowcharge on May 12, 2016 7:23:10 GMT -8
The isolator I have also directs the alternator output to the house battery after it's finished charging the vehicle battery. I dunno if all isolators do that or not. Voltage is only mildly useful as a ballpark figure of state of charge, and even the best battery monitors can only estimate the state of charge from battery-size info you program into them combined with counting the ingoing and outgoing amp-hours. To truly know the state of charge (in a wet battery, if you have sealed you're out of luck), you need a hydrometer to test the specific gravity of the electrolyte. They're cheap, and every auto parts store sells them. They not only tell you the state of charge, but they also show how each cell compares with the others, letting you know when you should equalize them, and when they are getting old: www.google.com/?gws_rd=ssl#tbm=shop&q=hydrometer+batteryA higher-amp converter will only speed up the bulk charging that gets you to 70-80% charged. After that it goes to absorption phase, where the amps are limited. With the voltage as low as it is in converters, getting that last 20-30% charged takes as long as the first 70-80%, but it's also the most useful part of the charge. I'm thinking the wire size for vehicle charging of an isolated house battery should be much larger than that needed just to run the lights and brakes through the harness, especially at 20 feet long or more. A typical alternator can put out 95 amps if the battery can take it, which is too much for #10, which is only rated for 30 amps in the table I read.
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sgaskill
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Post by sgaskill on May 12, 2016 17:20:37 GMT -8
Ok. That's what I was thinking about the isolator.
I wondered how accurate the estimation of the charge % would be just knowing the current voltage. Makes sense that it wouldn't be so accurate. I've seen hydrometers around but had never had reason to use one. Until now.
The converter I just bought is (3 stage) 45 Amp one so it should be enough. I keep reading that the last bit of the charge is hardest to get and that charging the batteries with a trickle charge a week or so before you use them is best to get them fully charged.
Re: wire gauge from alternator to house batteries, I had been thinking # 10, but maybe #8? I will figure it out.
Thanks a lot cowcharge, this information was very helpful. Good luck with the Shasta.
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Post by kto17 on May 14, 2016 11:50:32 GMT -8
I speed read thru this and there is some great advice. I didn't see it mentioned but because your batteries are in the back I would assume they are in a storage area. Make sure they are vented to the outside even if they are sealed. A smart charger will help avoid any issue but overcharging, which is when you are more likely to have a boiling issue.
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sgaskill
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Post by sgaskill on May 15, 2016 5:12:10 GMT -8
Good Advise. There is already a vent back there in the storage space. And it will put it far from the inverter as well as I have been warned about having it too close to the batteries.
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Post by kto17 on May 16, 2016 12:51:42 GMT -8
Good Advise. There is already a vent back there in the storage space. And it will put it far from the inverter as well as I have been warned about having it too close to the batteries. If you can build a box around it to separate it from the inside of the trailer. If you have a boiling issue the fumes can very dangerous. I read a post recently on a FB group with a newer trailer that they could smell and hear the battery boiling. They were awake when it happened and disconnected it.
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