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Old 02-18-2013, 06:01 PM   #1
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House Battery Bank Charging - Electrical Extension Cord Requirements

I am new to this forum, so if this topic has been covered I apologize.

I have diesel coach and I use 4 6 volt deep cycle T-105 Trojan batteries as house batteries (amp rating is 225 each). Further, I have a Xantrex 458 Freedom 2000 watt Inverter/Charger. My coach is a 50amp system that, of course, can run off 30amp power.

I store the coach in a covered facility that provides 30AMP service. I hate dragging my huge 50AMP power cord (with 30amp plug adapter) out when ever I want to charge my batteries. I would like to us a heavy duty extension cord solely for the purpose of charging my house batteries when in storage. All the other coaches in the same storage facility use extension cords to charge their batteries...I just do not know the specs of there ext cords.


Can someone advise me as to the AWG or amp rating for an extension cord I could use for the purpose of charging my house batteries off 30amp service? Given the 2000 watt inverter/charger could I use a 15amp rated cord or should I use a 20 amp rated cord (2000 watts/110v = 18.18 amps)? I assume I am drawing far less amps than 15-20amp when just charging the house batteries.

Thank you for your response.

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Old 02-18-2013, 06:40 PM   #2
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A lot depends on how many feet you have to go to connect to power.
12 gauge is as small as I would go only for the reason no matter what
you think you will use it for one always forgets and runs more stuff.
When I changed my extension cords I went with 10 gauge so the above
did not occur and along with the fact the 30 amp drop cord to the 30 amp
service was inline with code.

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Old 02-18-2013, 06:52 PM   #3
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I run our DSDP off a 30 amp service all the time and just use a 30 amp extension cord in the winter when I put two 1500 watt heaters, a couple small fans and a 100w light bulb in the wet bay.
The MH is plugged in all the time and all the "salesmans" switches are ON. But, if all I want to power is the battery charger, the refer and the storage bay freezer (in the summer) I just us a 50' 10 Ga extension cord. I do change the charger setting so it only draws 5 amps though. My batteries (Interstate U-2200's) lasted one month short of 10 years but I also put 4 oz of mineral oil in each cell. The batteries we actually doing OK but we were headed out for a long trip and I didn't want trouble on the road.
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Old 02-18-2013, 06:59 PM   #4
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Just go to Walmart and buy an extension cord rated for 30 amp and the length you need. Thats what I did and until I put my new addition on and have 30 amp installed in the garage it will work and has for 3 years.
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Old 02-18-2013, 07:23 PM   #5
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A standard 12 gage extension cord will handle 20 amps through the wire but the male and female ends are only rated at 15 amps. That is pretty much all you will need to handle your charger
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Old 02-18-2013, 08:07 PM   #6
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I use a standard 12 gage / 50 foot cord to charge my coach when it's in storage. I also keep a 1500 watt heater plugged in during the winter and have never had a problem.
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Old 02-18-2013, 08:29 PM   #7
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A good heavy duty extension cord from a big box store wioo do jusr fine. You can go bigger and more expensive, but there may be a concern that somebody else at the storage facility would like it too.
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Old 02-18-2013, 08:35 PM   #8
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Outhers can do what they want. I use a 10 gage extension cord for those times I am just runing minimal amps. When in storage I plug the 50 amp cord in.
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Old 02-18-2013, 09:37 PM   #9
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What is the maximum charging current of the charger, because it is this figure you need rather than the output rating of the inverter.. Say it is 80 amps at 14 volts at the end of the bulk charge cycle. That is 1120 watts. Allowing for inefficiencies, the AC current you will need to supply will be around 1120/120 - say 10 amps +20% = 12 amps.
Assuming sensible run lengths, your mains cord will need to be rated to take that current.
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Old 02-18-2013, 09:54 PM   #10
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A 12 gauge extension chord would work if you are only going to use it just to maintain a charge on your batteries. However, some day you may want to run additional electrical devices along with charging the batteries so a 10 gauge chord would do much better. I recommend you buy a 10 gauge if you can afford it - they can be a little pricey. My generator manufacturer recommends that I "exercise" the generator once a month so I run it for an hour and it tops off the batteries very nicely. This way I don't have to mess with an extension chord or the 50 amp shorepower chord that gets very stiff and hard to handle in cold weather. If you do get an extension chord and leave it plugged in when the coach is in storage, you may want to keep an eye on the electrolyte level. Depending on what type of charger you have, it may boil some of the electrolyte out ever long periods of time with the charger on. Take good care of your batteries and they will take good care of you.
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Old 02-18-2013, 10:00 PM   #11
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Cost difference is chump change.

12 guage should be minimum size, but 10 is optimum.

Next issue, connectors.

Buy a high quality cord, but think about connectors.

A 30 amp twist lock is a Contractor standard, so they are common, so price good.

Also rated for 30 not 15 or 20 amps.

Buy a Contractor cord, install twist lock on your landing or pick up the adaptor with the cord for standard outlet.

For MH end either use adaptor or replace end.

You will have standard cord that will charge batteries and run the AC
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Old 02-18-2013, 10:40 PM   #12
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if its strictly to charge batteries... your normal 14gauge extension will be just fine... remember, he is only using this to trickle charge the house batteries... not run the ac, fridge, tv etc.
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Old 02-18-2013, 10:54 PM   #13
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Originally Posted by Tony Lee View Post
Assuming sensible run lengths, your cord will need to be rated to take that current.
Which is why I set mine to 5 amps input.
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Old 02-19-2013, 01:40 AM   #14
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Interesting read. Not all of which meets code. Much of which is unsafe.e

Choices start with very small cords (those that have two prongs and you would use to run a light string at christmas) to the 50 amp cord the coach maker put on the coach. Then there is the 60 amp cord.

If you are going to use the 50 amp cord to get power into the coach then drag it out and use it. If you are going to tap a 30 amp recepticle then buy a 50 amp to 30 amp adapter and use it on the end of the 50 amp cord. Keep everything away from the 30 amp recepticle where you are plugging the cord into. If anything fails it will be here, failing means a possible source of fire. Worst case is fire second worst case is the need to replace the recepticle and plug on the end of the cord.

Now if this is the way you are going to go then all you will have is the 30 or so feet of cord on your coach and it will have at lest one size of wire over the code and maybe two wire sizes over the code requirements. Read as no voltage drop ( voltage drop means voltage wasted in the form of heat) (heat means possible fire).

Now if your plan is to put the adapter on the end of the 50 amp cord and plug it into a regular extension cord and leave the 50 amp cord in the basement of the MH then you will have a fire in the making.

The 50 amp cord has 50 amps on two legs for a total of 100 amps at 120vac Run that through a 20 amp cord or a 30 amp cord for any length of time then the failure is likely to happen at either end of the 20 or 30 amp cord. One end is at the recepticle where it is plug into and the other end is in your basement of your MH. So you make the choice, run the chance of burning down the building where it is stored in or catching your basement bin on fire.

Adapters are for using outside of your MH and only for a short time when it is watched for failure. Mostly pluged into a steel power post where failure will only damage the post and not start a fire in a occupied building or MH.

Now if your MH is like mine then the charger is pluged into a recepticle. But some of the chargers/converters are hard wired into the MH wiring system. If yours is hard wired then go back and read that which you should have already read.

If your charger is pluged into a recepticle then unplug it and plug it into a extension cord and plug the extension cord into a recepticle.

Now for extension cords,

#14 wire is for a 15 amp 120 volt load. It has the proper plugs on its ends they look like the regular plugs we are all used to. Two blades with a round ground pin.

#12 wire is for 20 amp 120 volt loads. It also has the proper plugs on its ends. They also look like the regular plugs we are all used to. But they are a little thicker. The recepticle end has stronger springs to hold onto the blades better. The big difference here is the recepticle rather than the plug. Next time you are in Home Depot check them out and compare. You can actually tell which one you are pluging into if you know what to look for.

You will find you can plug a 15 amp plug into a 20 amp recepticle. But if you compare the plugs you will find you can get a 20 amp plug that will not plug into a 15 amp recepticle.

Then comes the 30 amp cord with #10 wire the plugs and recepticle come in several types. Twist locks are for those applications where the contractor trips over the cord and tends to pull it out of the recepticle and the guy on the second floor who is just stepping for the ladder is not left in the dark. There is the dryer recepticle with huge blades it is for those applications where it is pluged in and forgotten and never inspected and should not fail at the plug, although the dryer plug is rated for 220 volts it also has 120 volts there also.. Then there is the RV crow foot that is rated for 30 amps at 120 volts.

What ever you decide to do do not overload your adapters. Do not take the chance that your children or your wife will not overload the adapter.

If your charger is the plug in type check the label for the amps draw and pick the shortest cord rated at or over the draw.

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