What guage wire for 120 foot 110V ext cord to 45 amp Iota battery charger?

[Northeaster]

Hi Folks,

After great input on this site, I have bought a new Iota 45a charger for my house bank (2 new group 27 wet cells). As I am about 120 ft from the AC, at my marina, I would like to know what guage of wire I would need, to not overheat, during maximum charging.
I tried a voltage calculator, but would like someone with more electrical knowledge to advise me as well.
I will either buy a premade "high end" extension cord, or make my own, by buying the bulk wire and ends. I have a short, approx 20' heavy duty shore power cord, and require a 100' extension cord - total run = 120'

Thanks in advance!!

[pfatyol]

Just a question, the 45 amp Iota Charger, the 45 Amp is the output amperage, what does the manual / unit say for required input amperage?

[SteveInMD]

American Wire Gauge table and AWG Electrical Current Load Limits

This site says #10 for 120 feet one way will get you a little under 10% voltage drop pulling 45 amps. Number 12 wire would result in 18% drop - that's way too much. I wouldn't go more than 10% voltage drop. I realize it's not likely that you will be pulling the full 45 amps, but for lack of a better number you should size it that way.

[sailingdog]

45 Amps at 14.4 VDC, worst case scenario is 7 amps total... a 12 AWG power cord should be able to handle that.

[camaraderie]

NONONONONONO!

The MAXIMUM current draw on AC is 11 amps!!! You just use your standard 30amp dockside power cord. There is NO appreciable voltage drop in AC.

What you DO need to worry about is the gauge of wire from your charger to your battery! Use this link to figure that out and be sure to use the TOTAL length of the wire TO and FROM the charger to the battery!
http://beta.circuitwizard.bluesea.com/

[SteveInMD]

Good catch camaraderie. The 45 amps is 12 volt at 45 amps to the battery.

A number 14 AWG cord is enough for the 11 amp load. I would still use a #12 cord in case you want to also run a power tool or something at the same time.

[sailingdog]

Cam-

He needs an extension cord, since he is 120 FEET from the AC outlet. No dockside shorepower post.

[Northeaster]

Wow!! This is why I decided to ask!! I don't know the input amperage, as i haevn't picked up the unit yet - it was shipped, and is waiting to be picked up - so no manual yet!

I forgot about the ac-dc so I was thinking I needed something that could handle 45a on AC ... like #8 wire!! Glad i asked.

Cam - Just so I can understand, if there is no Voltage drop on AC - why do they recommend thicker guage extension cords when running expensive tools like routers, etc? I thought the thinner cords would cause more resistance, and burn out / damage the motors over time!

SD - yes, you are correct - I need a 100' extension cord, ot go with my 20' shore power cord!! So you think that #12 cord should be fine??

[SteveInMD]

You didn't ask me, but that wont stop me from answering! The specs for your charger say 11 amps max on the input side, so yes a #12 is good. If you are going to buy a 100 foot cord get a #12 wire ext. cord. Anything smaller at that length isn't good for much else than a few Christmas lights or something. A smaller AWG size cord is just hard on your power tools, etc.

[camaraderie]

Steve is absolutely right. You DO get a little voltage drop (like 3 VOLTS when the charger is on MAX) on a 100 foot run but the 12G will be absolutely fine.