Power inverter install

[Chesapeakegem]

I DID do a quick forum search on this question before posting so.....I have this shiny new 800w/1600W inverter that I'd like to install for the occasional recharging cell phones and running a laptop, fan, etc. etc. Not for continuous use. My question is: Is it okay to wire it directly to my deep cycle marine house battery?

Thanks,,,

[Hirilondë]

Every wire in a boat should be fused according to its size as close to the source of power as possible. I like being able to turn off the power myself in most cases should I choose to, but that is a personal preference.

[Figment]

"wire it directly to house battery" vs. what?

A fuse or breaker is mandatory.
I'd connect it downstream of my ammeter, just because I'm a nerd and don't like un-tracked loads.
I don't think it's necessary to have a cutoff switch, but again I'm a nerd and I like to know that NOTHING is drawing down the batteries when I leave the boat.

What are you trying not to do?

[Chesapeakegem]

This is not intended to be a permanant installation, pretty much "On" only when needed then disconnected when not in use. The unit (a Cobra model CPI) features automatic shutdown on Current overload, Voltage overload, Voltage shortage and Temperature overload. I specifically asked about connecting it to a deep cycle marine battery because I believe I have read someplace that connecting a power inverter to a deep cycle marine battery could be problematic.

[Chesapeakegem]

I should have also mentioned that I do not have shore power capability. My only other battery (a conventional marine starting battery) is dedicated to my outboard motor.

Thanks...

[Hirilondë]

Are you saying that your only means of charging is to take the battery home and do it? There fore you want something easy to take apart? The bottom line is that what ever you do it must be protected (fused). It is also good if the battery terminals are protected from an accidental direct short. Mine are in plastic boxes with strapped on lids.

[Chesapeakegem]

Yes, I do have to remove my battery's to charge them. Shocking isn't it? Thanks for the help.

[Maine Sail]

A couple of thoughts. Yes you CAN connect directly to your batteries but the + cable should really be fused as close to the battery as possible. Not so much to protect the inverter but the cable from chafe and the possibility of a dead short and resulting boat fire.

As for charging small phone batteries and such be very careful with modified sine wave inverters. They can tend to fry batteries and often trick the chargers into never shutting off. Killed a $60.00 Nikon battery in a weekend using a friends MSW inverter, at his camp, which is solar powered.

For a laptop or phone using an inverter to charge is horribly inefficient (upwards of 30% +/- over direct DC) and with only an outboard to charge from you will be wasting a lot of Ah's. A laptop on an inverter can draw upwards of 7-8 amps depending upon program running and the state of the internal battery charge. Direct DC chargers are available for most every laptop and they will also consume considerably less current than going DC to AC back to DC. Laptops run off DC anyway as do cell phones. 12V cell phone chargers are dirt cheap these days at Wal*Mart and DC laptop chargers are also very reasonable compared to an inverter the fuse and the wiring needed to power it.


Even a little tiny Netbook running on a small 150W inverter can burn over 4 amps running only Mozilla Firefox.


That same Netbook draws about 25% less current when running direct DC.

[Chesapeakegem]

Thank you Maine for your excellent help. I'll be keeping the Power inverter (got too good of a deal on it) but will be heading over to Best Buy to locate a DC charger for the laptop and a good quality 12V (cig lighter) power adapter. In spite of it's age my boat does have a good "fused" circuit panel with a couple of available circuits. What size fuse and wire guage would you suggest?
Thanks again!

[Chris Campbell]

I also found that with my Xantrex inverter it was drawing power even when turned off. If I had needed it I would have put a heavy duty switch (battery switch?) in between it and the battery - as it was I just eliminated it from the boat, and never missed it.

For the few little things I needed AC power for the battery pack with inverter and whatnot that I carried as an emergency backup to get the engine going if all else failed did admirably.

[Snowfish3]

The gauge of the wire is dependent on the distance from the voltage source and the tolerated voltage drop 3%-5% as well as the potential amp load. Then fused to protect that wire from melting or fire, if there is a dead short. The fuse in this case protects the wire (as Mainesail stated) not the inverter.
I looked up the spec on the Cobra and it is a modified sine wave inverter. I would caution you that I had a similar one, cheaper to buy then a pure sine wave inverter. I learned my lesson after burning out a Mac Laptop charger $79.00 and a Dremel tool $80.00 now I have a 1000w pure sine wave one installed, no worries.

Kurt