zero Posted January 3, 2013 Share Posted January 3, 2013 what about using an oversize alternator? could you run the engine in park for a 1/2 hour and charge up the house battery when it got low? Yes, I do it often on several of my RVs. My Chevy Blazer Chalet has a 150 amp alternator that puts out 50 amps at engine idle. Works great but - as Maineah stated - not an efficient way to do it. Not sure how much that matters for some. A 2.2 or 2.4 four cylinder engine is very inefficient at engine idle speed anyway. Asking it to run a small power load is much more wasteful then if you did the same with a small 3-5 horse lawnmower engine (or a small gas powered generator). I just put a 150 amp alternator in my 1978 Toyota for the same reason. The main thing you need to watch is what size alternator you use. The regulator for an auto alternator is not very "smart" and will overcharge and overheat batteries if it's too big. So, once you know what size your battery bank is - you should match it with the alternator. A stock alternator in an older Toyota can charge near 30 amps at engine idle. If you only have one RV "house" battery" that's all the charge you need. My Chevy Blazer has four RV batteries and that's why I use the bigger alternator. As to ruining the converter? I doubt it, but yes they get hot. You don't want to be parked on dry grass with the engine running long (or a wood floor). There is a woman near me who ran her entire house all one winter on her Honda Accord. Yeah, sort of a silly thing to do - but it worked and her converter never suffered. She got mad at the power company and had her power shut off (with no real plan). She bought some batteries and two inverters and lived the entire first winter by hooking jumper cables from her Honda Accord to her battery bank and jamming a stick on the gas pedal to rev it up . After that first winter, she put in solar panels. Probably the most efficient battery charger on the planet if run on gasoline is a small 5 horse motor hooked to a 50-100 amp auto alternator. Very easy to build such a small portable rig. Quote Link to comment Share on other sites More sharing options...
douglitas Posted January 3, 2013 Share Posted January 3, 2013 looks like we're going to go with a 250 W solar panel...new for $265! charges 18V 17A in full sun. ( I know that's 300W, but those figures are rounded off) about 5 ' long and weighs 40 lbs. These guys even charge on overcast days. Now I need to make a light weight foldable stand for the panel so I can park in the shade and set the panel in the sun and charge my battery all day. Quote Link to comment Share on other sites More sharing options...
Maineah Posted January 3, 2013 Share Posted January 3, 2013 It won't damage the converter because it's just doing what it normally does but it will run hot I mean like really hot because there is no air flow to cool it off. Those of you that have suffered hot foot driving your toy home know what I'm talking about. 130 HP engine making power that could be done with 2 or 3 does not compute. Solar to me unless you need a/c and a microwave is the only way to go earth friendly quiet and a good bit cheaper then a generator. Quote Link to comment Share on other sites More sharing options...
zero Posted January 4, 2013 Share Posted January 4, 2013 looks like we're going to go with a 250 W solar panel...new for $265! charges 18V 17A in full sun. ( I know that's 300W, but those figures are rounded off) about 5 ' long and weighs 40 lbs. These guys even charge on overcast days. Now I need to make a light weight foldable stand for the panel so I can park in the shade and set the panel in the sun and charge my battery all day. They charge, but not by much on darkish overcast days. Maybe somebody is telling your stories? Or maybe your overcast is much brighter then mine. My house and barn are run 100% from solar and I have a digital readout in the house so I can always tell what the panels are doing. With 5400 watts of solar panels - when the sun goes behind the clouds I'm lucky to be getting 200 watts out of the whole mess. A 250 watt panel will at times barely make 1 amp of charge current when it gets dark and cloudy. To the converse, in extreme cold and snow cover it can overproduce and charge over 20 amps. $265 is a good deal considering that 5 years ago it would of cost near $1000 for that panel. Quote Link to comment Share on other sites More sharing options...
WME Posted January 4, 2013 Share Posted January 4, 2013 Be careful about "remote panels" your dealing with low voltage and high current. Power loss can be substantial. Quote Link to comment Share on other sites More sharing options...
douglitas Posted January 4, 2013 Share Posted January 4, 2013 thanks for the comments and suggestions. For a current of 17A over 50 feet #8 should do the trick...not too expensive. I also had a solar home with a small array (about 2K) and the panels would charge decently on overcast days. Those were the days of $4/watt for used panels. What I am looking for now is a tripod or other type of mounting system that is light, foldable and adjustable. Quote Link to comment Share on other sites More sharing options...
Stevo Posted January 7, 2013 Share Posted January 7, 2013 Is this the $7 multimeter at Harbor Freight http://www.harborfreight.com/7-function-digital-multimeter-92020.html that you recommended? Would that work for whatever I need to test on a Toyota motorhome? And could I use that same multimeter to check how many amps something (like a DC fridge/freezer for example) is using so I can figure out how many watts I need for a solar panel system? If you are trying to diagnose ;problems - you need some cheap diagnostic tools. Start at the simple level. Furnace and battery. #1 find out how much power your furnace is actually using. You can buy a digital multimeter from Harbor Freight for $7 and it has a 10 amp scale on it (all you need). Your furnace should probably only draw 6-8 amps max. Then verify what battery you have by AH or RC size AH is amp-hour and RC is reserve capacity. They both tell you the same thing in a different way. A typical Walmart 12 volt type 27 deep cycle battery is rated at 115 AH or 160 RC (approx). Basically good for a steady one amp draw for 115 hours before it's dead. Almost 5 days. Cut that in half or a battery only half-dead and you've got 2 1/2 days. Now - if your furnace draws 8 amps - just divide 2 1/2 days by 8 amps and you get 7 1/2 hours run time. That's with the furnace going non-stop and never shutting off. If running half the time ,that comes to 15 hours of staying warm with one battery. But you need to figure out what battery you have, if it's any good and if it's fully charged before you use. If it does not rise up to near 14 volts when your RV is running, you've got problems. Quote Link to comment Share on other sites More sharing options...
Derek up North Posted January 7, 2013 Share Posted January 7, 2013 That'll do the job. Quote Link to comment Share on other sites More sharing options...
stamar Posted January 7, 2013 Share Posted January 7, 2013 yes they often give them away for free with coupon. i have about 4. at this point i have 2 for each car. They all kind of have the same drawback in that the 9 volt battery that they come with is a peice of crap and dies. it even leaks. but once you have another 9 volt battery in it its great. Quote Link to comment Share on other sites More sharing options...
Stevo Posted January 7, 2013 Share Posted January 7, 2013 Can I test a DC Edgestar fridge/freezer to see how many amps its using with that cheap multimeter at Harbor Freight? And if so, do I need to buy some special connectors that don't come with it? Quote Link to comment Share on other sites More sharing options...
zero Posted January 7, 2013 Share Posted January 7, 2013 Can I test a DC Edgestar fridge/freezer to see how many amps its using with that cheap multimeter at Harbor Freight? And if so, do I need to buy some special connectors that don't come with it? The cheapest multimuter at Harbor Freight can test to a maxiumum of 10 amps DC. If your freezer draws more then 10 amps it will blow the fuse. I've bought many of those little multimeters for $1.99 each. I've also ruined many, but for that price - no big deal. If you want to spend a few extra bucks - this HF unit tests to 20 amps which will be more then enough for a small DC fridge. http://www.harborfreight.com/ac-dc-digital-multimeter-37772.html I don't know what you but my place has a large 12 volt DC refrigerator and a large 12 volt DC chest freezer. Both run on 5-6 amps but spike at 10-12 amps at first motor start. Quote Link to comment Share on other sites More sharing options...
zero Posted January 7, 2013 Share Posted January 7, 2013 And could I use that same multimeter to check how many amps something (like a DC fridge/freezer for example) is using so I can figure out how many watts I need for a solar panel system? The amps that a refrigerator draws has little to do with what size panel you need. It's depends on how often it runs versus how often it does not. That is controlled by how much insulation it has. I've run a 6 cubic foot 12 volt DC refrigerator on a single 120 watt solar panel in the "dark" Adirondacks of NY. So that panel on a good day makes 5-6 amps per hour for maybe 5-6 hours and it's enough for the fridge to stay cold for a day and a night. Obviously you cannot direct-couple the panel without a battery that acts as a "storage buffer." I suggest you go to this link and read up a bit on solar powered refrigerators: http://www.backwoodssolar.com/catalog/refrigerators.htm Quote Link to comment Share on other sites More sharing options...
Stevo Posted January 7, 2013 Share Posted January 7, 2013 I will read the information from the link you suggested, and thank you. I don't want to hijack this thread anymore than I already have so I just started another thread on energy usage, etc. here http://toyotamotorhome.org/forums/index.php?showtopic=5431 and would really appreciate your input please. The amps that a refrigerator draws has little to do with what size panel you need. It's depends on how often it runs versus how often it does not. That is controlled by how much insulation it has. I've run a 6 cubic foot 12 volt DC refrigerator on a single 120 watt solar panel in the "dark" Adirondacks of NY. So that panel on a good day makes 5-6 amps per hour for maybe 5-6 hours and it's enough for the fridge to stay cold for a day and a night. Obviously you cannot direct-couple the panel without a battery that acts as a "storage buffer." I suggest you go to this link and read up a bit on solar powered refrigerators: http://www.backwoods...frigerators.htm Quote Link to comment Share on other sites More sharing options...
Boots Posted January 10, 2013 Share Posted January 10, 2013 Is anybody running 2 12v batteries? It just seems to me that it would be a great idea. Your thoughts please. I'm thinking about it. I have the room, as currently constituted. I am also thinking about taking out the enclosure under the sofa and enlarging it to hold four 6v batteries, but I think that the weight issues will keep me from doing that. The real problem with this is the gases given off by the batteries, they are corrosive, toxic and flammable. You would be very foolish to do this. The reason batteries are housed outside of the RV is for venting, cooling, and corrision resistances. Outside is where they belong Quote Link to comment Share on other sites More sharing options...
Boots Posted January 10, 2013 Share Posted January 10, 2013 Thanks for the replies. I have a pretty thorough understanding of electronics. I do know that 2 12v batts in parallel should last twice as long. Charging time will double because current in parallel will be split 50/50 to each battery. As far as the isolator goes it is pretty rusted up and I checked it with my meter. Its definitely bad. There is also some sort of circuit breaker or something mounted to it. i see no way to reset that. I will probably just take some long jumper cables just in case as I'm leaving for a boondock hunting trip on Wednesday. I also think my isolator has 4 poles. I will get a pic and post it up soon. YHi Shaggy, The circuit breaker is there to protect the wire (same as in your house) from over current (the demand exceeds the safe current limit of the wire) and so it is integral to the system and its safety. I bought one from Lordco (probably NAPA for you) and it took about ten minutes to install, it was rated for 30 amps. When you are up to inspecting the rest of the system, check the charging wire from the battery isolator and ensure that it is sized correctly (depending on the output capacity of your alternator) for the current, I would suggest something in the #6 to #8 AWG size. If you want to step it up a notch, here are some marine grade battery isolators - http://www.cristec.fr/en/on-going-serial-products/rce-electronic-battery-isolators.html All said and done, if it was me, I would do the repair, if I knew I had a problem before leaving, and then I had trouble, I have only myself to blame. Enough said. Good luck. Brian Quote Link to comment Share on other sites More sharing options...
Boots Posted January 10, 2013 Share Posted January 10, 2013 Can I test a DC Edgestar fridge/freezer to see how many amps its using with that cheap multimeter at Harbor Freight? And if so, do I need to buy some special connectors that don't come with it? Just to be clear, multimeters generally refer to the measurement of Voltage, and sometimes they can measure Resistance, however, if you want to measure Current, you need something that will read Amperage. A lot of small "multimeters" offer to read current, but they are not very accurate. If you really want to get an accurate reading of Amperage, buy a meter for that purpose, such as http://www.extech.com/instruments/product.asp?catid=26&prodid=87 - these use RMS meter calculations to determine the true current being drawn and also safety rated for explosion resistance or redirection. True, they are expensive, but you only have to buy one of them and they will likely last forever. These particular models are rated to 30 amps and on some models up to 400 amps DC. Brian Quote Link to comment Share on other sites More sharing options...
Stevo Posted January 10, 2013 Share Posted January 10, 2013 Brian, will this multimeter measure amps? http://www.harborfreight.com/ac-dc-digital-multimeter-37772.html I have no idea how to use it yet but I hope it works for amps cuz I just bought one. Quote Link to comment Share on other sites More sharing options...
waiter Posted January 10, 2013 Share Posted January 10, 2013 Yes, looks like it will measure up to 20 amps. John Mc 88 Dolphin 4 Auto Quote Link to comment Share on other sites More sharing options...
zero Posted January 11, 2013 Share Posted January 11, 2013 Just to be clear, multimeters generally refer to the measurement of Voltage, and sometimes they can measure Resistance, however, if you want to measure Current, you need something that will read Amperage. A lot of small "multimeters" offer to read current, but they are not very accurate. If you really want to get an accurate reading of Amperage, buy a meter for that purpose, such as http://www.extech.co...id=26&prodid=87 - these use RMS meter calculations to determine the true current being drawn and also safety rated for explosion resistance or redirection. True, they are expensive, but you only have to buy one of them and they will likely last forever. These particular models are rated to 30 amps and on some models up to 400 amps DC. Brian Multimeters are just what the name denoters - meters that do multiple things and not just read volts. For measuring current draw like Stevo wants to do - a RMS volt meter is not needed. If he wanted to read non-true-sinewave voltage from a cheap stepped wave inverter - then yes. The $4 Harbor Freight reads DC current to 10 amps and the $20 HF meter reads up to 20 amps DC. Both are plenty accurate in those current ranges. I've had two Extec 470 meters (my choice for cheap RMS meters with infrared temp). They certainly do not last forever. Quote Link to comment Share on other sites More sharing options...
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