Bob C Posted January 4, 2012 Share Posted January 4, 2012 I plan on installing my inverter next to the coach battery as suggested here. I think that the wire from the isolator to the coach battery is currently an 8 ga. I plan on installing a 4 ga from thealternator to inverter to the breaker and from the breaker to the battery. Basically putting in heavy wire all the way through. Does the existing wire go to the 120 v converter for some reason? How do I route the heavy wire? Can I go from the breaker straight to the battery to keep everything as short as possible? Sorry for all the questions but I want to do it once and do it correctly. Thanks for the help. Quote Link to comment Share on other sites More sharing options...
WME Posted January 4, 2012 Share Posted January 4, 2012 How big is the inverter? Even with 4 ga to the battery you may need 0 ga to the inverter. A 750w inverter can draw up to 75 amps. Quote Link to comment Share on other sites More sharing options...
waiter Posted January 4, 2012 Share Posted January 4, 2012 I plan on installing my inverter next to the coach battery as suggested here. I think that the wire from the isolator to the coach battery is currently an 8 ga. I plan on installing a 4 ga from the alternator to inverter to the breaker and from the breaker to the battery. Basically putting in heavy wire all the way through. Why the upgrade to heavy wire?? Unless your also upgrading your Alternator to supply high er current (i.e. 120 amps), a heavy wire isn't necessary. The 55 amp alternator is probably supplying a max of around 35 amps to the coach circuit. If you do decide to do this anyway, don't forget to upgrade the circuit protectors (self resetting circuit breakers) to a higher amperage, i.e. 60 or even 100. ALSO - leave the #8 wire and just add on a new #6 beside it. If you are installing a high amperage alternator, then the wire upgrade is mandatory if you wish to get those amps to your truck battery and your coach battery. You need to supply the battery with about 14.6 - 14.8 volts in order to fully charge it. Normally, when your driving down the road, the only thing from the coach that's loading down the alternator will be the coach battery charging. Initially, if the coach battery has been run down, it will be drawing full current from the Alternator, i.e. say 30 amps. If the Alternator is putting out 14.8 volts, and the #8 wire going back to the coach battery is 20 ft long, a 30 amp draw through the wire will drop about 0.4 volts. This drops the voltage at the coach battery down to about 14.2 volts.. OK - DON'T PANIC - Even thought this isn't enough voltage to fully charge the battery, the battery is charging. As the battery charges, the current draw starts going down, and hence, the voltage drop in the #8 wire also starts going down. As the battery continues to charge, it'll reach a point where its only drawing an amp or two. At 2 amps, the voltage drop in the #8 wire will be 0.03 volts, the voltage at the coach battery will now be 14.77 volts. and the battery will maintain a full charge. Does the existing wire go to the 120 v converter for some reason? The Converter has a couple jobs; It supply's 12 volts when your plugged into shore power and also acts as the 12 volt distribution center. So, the Converter can get 12 volts from the Truck, from the Coach battery, or from the Converter when plugged into shore power. I If you have the old original Converter, it will supply around 25 amps, HOWEVER, the voltage isn't high enough to charge the coach battery at 25 amps. It will only charge around 4-6 amps, and is not an intelligent charger, it will boil the battery. Put a Converter upgrade on your list of things to do. John Mc 88 Dolphin 4 Auto Quote Link to comment Share on other sites More sharing options...
Maineah Posted January 4, 2012 Share Posted January 4, 2012 Yes how big is the inverter? The standard wiring to the isolator is a # 8 good for 30 amps or so. The alternator is 60 amps it needs to feed two batteries and run all the stuff in the truck lights, heater fan, andso on. You would gain a bit better charge rate to the coach battery with a larger wire but if you max the alternator out you'll not fully charge the batteries. The little breakers are good for 30/35amps the isolators maybe 65 amps or so if you run a # 4 wire you'll need a 100 amp fuse to do any good. If you are close to the battery in the coach you can drop the wire size to the inverter to match the draw because the loss will be low on a short run. Granted you probably will not draw huge current all the time but when you do every thing will take a hit. Watts divided by battery voltage will give you amps don't mean to discourage you butyou'll need to consider every thing if you want it to work right and it really depends on how much currentyour inverter is going to draw. There are a few web sites that have wire gauge to current charts that will give you an ideal on what you'll need be sure that you look at DC loads there is a difference with wire size. I would not worry about the coach converter is really does not need a bigger wire if it's the original you may consider a new converter due mainly to the better charge rate and general output it's a great upgrade. Quote Link to comment Share on other sites More sharing options...
Bob C Posted January 4, 2012 Author Share Posted January 4, 2012 I had planned on installing a new converter. I also have a Scamp trailer and on that forum they pretty much agree that the stock converters are nothing but slow death to batteries. I was told over there that the Progressive Dynmaics converter with the 3 step "Charge Wizard" was a pretty good unit. I can get a 45 watt unit for about $100 with the smart charger. For the Toyhouse, i guess that adding a 6 ga wire from inverter to battery (with fuse) is good. Keep inverter VERY close to battery. Install a different converter. does this sound like a good list for a spring project? If so, I think that I will order the new converter today. Since I am installing a new deep cycle battery, i may as well do the converter at the same time. Thanks for the help. Quote Link to comment Share on other sites More sharing options...
waiter Posted January 4, 2012 Share Posted January 4, 2012 All that sounds good - look at the price difference between 45 and 55 amps, might be worth the extra $10 to go 55 amps. ALSO look at the kit, it has a new distribution board etc. What size inverter??? EXAMPLE: a 1500 watt inverter drawing 150 amps, using a 2 1/2 ft wire in each direction (5 ft total) will drop 0.3 volts in the wire (#6 wire) Keep the inverter as close as possible and make the wire as big as possible. Some auto supply houses can custom cut the wire and crimp on connectors for you. Here's a link to a wire voltage drop calculator. Enter your length first, then enter the amps. Voltage Loose Calculator John Mc 88 Dolphin 4 Auto Quote Link to comment Share on other sites More sharing options...
Maineah Posted January 5, 2012 Share Posted January 5, 2012 How big is the inverter and what do you intend to run with it! That would be a big help we could help you a lot better with a bit more info. I agree with John the price difference between the 35-45 is like 6 bucks and maybe 20 from 35 to 55 Quote Link to comment Share on other sites More sharing options...
Derek up North Posted January 5, 2012 Share Posted January 5, 2012 Another possible source for heavy cables is a welding supply shop. Quote Link to comment Share on other sites More sharing options...
Bob C Posted January 5, 2012 Author Share Posted January 5, 2012 The inverter is a 750 watt to run the dorm sized refrigerator. I still plan on putting in a 3 way frig when I find a good used one. I tried a 400 watt inverter, but the frig put it into overload so it shut down. I am hoping it is just the start up that is overloading the 400 watt. I had borrowed the 400 from a friend (and it still works good) to see if it would work and was going to buy an inverter anyway. I got the 750 digital display Schumacher for $35 as a close out. The inverter will be very close to the battery, like 18" or less. I will look into the larger converter. I don't plan on being hooked to outside power very often but if it is only a couple of dollars more, it would be a good deal. Quote Link to comment Share on other sites More sharing options...
Maineah Posted January 5, 2012 Share Posted January 5, 2012 OK now were are talking I don't think you need to change any thing. Just make a good hook up to the coach battery and call it good. The inverters are pretty linear so all though it's 750 watts it will only draw what it needs, so for a very short time it may draw a bit you can check the tag on the fridge it will give you the current rating use that figure X2 and that is close to what it will draw to start. I just had a look at a fairly big dorm fridge and it only draws 6 amps running so you are good to go your system will charge the coach battery just fine. If your inverter is close to the coach battery just use the cables that come with the unit you may have to cut off the clamps they have there own fuses so you are good be sure the cables going to the battery are well protected because they won't be fused. Parked you may have to turn it off over night to avoid draining you battery I guess the best bet it to see how often it runs. A new converter is a good investment it saves the battery, you can leave it plugged in and it will give you good clean power for all your 12 volt stuff. I have a 45 amp unit and it's all I need and then some I leave it plugged in all winter you can't do that with a stock charger/converter. Quote Link to comment Share on other sites More sharing options...
waiter Posted January 5, 2012 Share Posted January 5, 2012 Everything Maineah said The only thing I would add - Before going to all the trouble of installing the frig, plug it into the inverter and run it for a couple days. ALSO - look at the cost difference between the 750 and a higher power inverter, I'm thinking 1500 watts to run a microwave or a coffee pot. John Mc 88 Dolphin 4 Auto Quote Link to comment Share on other sites More sharing options...
Bob C Posted January 5, 2012 Author Share Posted January 5, 2012 The frig was in the MH when I bought it. I would like to change to a 3 way if I can find a good price on one. I messed up on a new smaller one by waiting to talk to the wife. Only $200 for a 2 cu ft norcold, new in the box. And only $30 delivery. I won't wait next time. I don't drink coffee and don't plan on installing a microwave so i think the 750 will be good. Stepping up to 1500 didn't seem worth the extra $ for me. I have been tenting, pop-up, and Scamp camping for 50 + years and having an electric light seems like luxury to us. I am lucky to have a good wife who thinks sitting by the fire and then snuggling in the sleeping bag is a great end of the day. We have never cooked a meal in either the pop-up or Scamp in 20 years. With the MH, I can see us cooking inside in cold weather when we get into the Rockies but simple stove top stuff or maybe in the oven. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.