Power inverters

[hitthebricks]

If a inverter take 12 volt power and converts it to 110 volt power, could I plug the inverter into my cig. lighter and the onboard charger into the inverter to charge my batterys? Sounds to easy. HTB

[Moose-Hunter]

Howdy HTB...

It almost does sound too easy. I don't think the circuit for your cig lighter would have the juice to power your onboard charger. Having never worked with an inverter, I really can't make an educated guess.

Why not wire in a "dedicated" circuit for your inverter directly to the battery? That way, the inverter would be getting as close to "full" power as possible and eliminating the possible overload problems with the cig lighter...

Or maybe running power to your inverter, back to a connector near your trailer connections for charging while driving.

Just food for thought...

[Giant_Jackpot]

It’s all about the watts. But without doing the math, I doubt the efficiency would be there to make it work. In other words, it would take more power to run the inverter than you are putting back. If I get time I will do the math for you……….

[Macgyver55]

Nope, Jackpot is right, it doesn't work that way. It uses more power to charge the battery than it is able to put back. In fact it will drain the battery faster than doing nothing. If this type thing were possible, we would be seeing a whole lot of electric cars running around.

[Giant_Jackpot]

But I’ll bet a guy with the name Macgyver could get something going with some bubble gum and duct tape!

My first reply was with the thought you might be trying to charge the main motor battery which would not work. But you MAY be able to charger your trolling motor batteries. I say MAY because it would depend on how many amps your main motor charging system can kick out.

I did a few minutes of research on the web and looked at 4 different manufacturers of on-board chargers. None of them listed how many amps they were pulling from the 120 volt outlet. I looked on the back of the power supply for my laptop and it uses 1.5 amps at 120 volts and its output is 4.5 amps at 20 volts. 1.5 amps times 120 volts equals 180 watts AC power required. Basing these calculations on my laptop charger, the needs of a 20 amp on-board charger would be 4 times greater so 180 watts times 4 would equal 720 watts continuous. Again looking on the web at various inverter manufacturers, I cannot find any that will tell me how many amps these things pull out of a 12 volt battery. I did notice however that an inverter with a 720 watt output has a 30 amp fuse on the 12 volt input. I would assume the inverter would never run continuously at 30 amps so lets say it runs at 20 amps continuous. Can your main engine put out 20 amps continuously? Remember that your engine also needs to charge the starter battery.

Well, I have probably said too much and if anyone has better specs/info out there please correct me if I am wrong. I would say this would not work out too well and as Mac pointed out I would think that if this were a good way to do it, the boat manufacturers would offer it as an option. Now if you have a big cabin cruiser with twin inboard engines and dual 100 amp alternators, that is another story………..

[efgh]

If you have a trailer conector that is O.E.M. equipment on your truck, the bigger round one, the center one is hot, direct from the battery, if you run a wire from this post directly to the boat battery it will charge the boat battery while you drive or run the pickup, this is how my camper trailer works. just a thought on how to charge batterys on the move.

[Dave]

efgh, I use that line from the tow plug to charge my pickup camper battery. Works great. I think it's actually lableled as a battery charge line for travel trailers. The line should already be fused and it runs through a relay that turns on when the ignition key is on, on a Ford F250 anyway.

[marine_man]

It almost sounds like you're looking for a stay n charge system.. or something similar... do a search on here for "Stay N Chage"... it's very similar to hooking up to the heavy red wire at the trailer connection on your vehicle.

marine_man

[GoodToGo]

Careful, it's not always the center one, at least if it's not OEM. On my 6 pole Hoppy the center is for electric brakes. The auxiliary power is labeled battery recharger (in the directions)and is one of the side poles. It is on a relay though, you won't get any voltage unless the key is on. Mine is a 40 amp relay. I don't see any reason why this wouldn't charge batteries while the truck is running and the lights are off.

[hitthebricks]

Thanks for the replys guys, kind of knew it couldn't work but couldn't figure out why, guess thats why I lay brick for a living. Thanks again HTB