Okay So I am a cheap skat who collects junk and instaed of going out to buy some fancy car stereo i took a sony mini component system and a JVC RX 40 reciever and a bunch of speakers and went and picked up a 25 dollar 500 watt power inverter. I was shocked to here the sound but disappointed that it kept friggin cutting off the inverter was getting too much or too little power either way i had an idea when my power got cut off LOL i took two of my three batteries and hooked it up, thought to myself and i though this was gonna burn it out. SO i took that idea to my van My inverter is hooked up to two batteries, with two batteries hooked up what affects can this have on my electrical system you know a battery hooked up to another with a inverter in the middle. So far no drains no negative side effects!
landyacht318
10-02-2008, 08:45 PM
Cheap inverters produce a modified sine wave. Some electronics do not like it and will fail instantly or overtime through overheating.
I used to run my inverter to power my laptop for music. There was a loud buzzing.
Wire the inverter directly to battery with at least 10 awg cable. The ciggy plug is only good for light draw.
I have never had problems running my inverter while driving but I read that others have.
If the batteries are in parallel and of different ages and makes you will run into problems with the better battery getting overcharged and the weaker one undercharged. Basically the good battery will be brought down by the worse one. The overcharged battery will boil and bleed off acidic H20 and rot everything around the battery.
If you secondary ' house' batteries are a large distance from your chassis battery, you need fat(expensive) cable for any significant alternator charge to get to them.
If your batteries are of different ages and makes, I'd advise not paralleling them, or if you do, monitor them while charging and see if one is getting warmer than the other.
I used to have alternator problems with mismatched paralleled batteries.
Regular Flooded wet cell lead acid batteries should not be in the passenger compartment due to gassing. If you over fill the batteries and the hydrogen gas cannot escape, your batteries can become bombs.
AGM batteries are acceptable inside the Van but cost double for the same amp hours.
Wally world "deep cycle batteries" are a compromise between starting and deep cycle. Cheap and you get what you pay for. I wont make this mistake again.
A lot of people swear you get the best, longest lasting true deep cycle batteries with two 6 volt golf cart batteries wired in series.
Sam's club, Costco.
Trojan t 105s are considered the best/ longest lasting. but pricey.
Your alternator will have to work much harder to charge mismatched batteries. You could blow a fusible link. You could fry your alternator if starting the van with heavily discharged batteries.
Or you might not.
leeann
10-03-2008, 01:48 PM
I'd suggest putting a battery isolator between the two batteries - keeps one from discharging the other.
That's the setup on my RV and it works well.
BigBlackB250
10-07-2008, 04:21 PM
well ones a autolite big one too like 850 cc amps and like 1000 in normal temps the other is the battery a dodge is supposed to get not sure of the size but its a decent battery, I havent had any problems they are both about a year and a half old, No problems yet. Im guessing I can find an Isolater at an autoparts store. I havent had any fume problems either it seems to work really well but then again i have only had two weeks worth on them so well see. Thanks again
RamVanMan
10-09-2008, 12:32 PM
Uh, BigBlackB250, you said:
picked up a 25 dollar 500 watt power inverter. I was shocked to here the sound but disappointed that it kept friggin cutting off the inverter was getting too much or too little power either way i had an idea when my power got cut off LOL i took two of my three batteries and hooked it up, thought to myself and i though this was gonna burn it out.
Sounds like you went way undersized on your inverter to battery cables. Ditto what landyacht318 said, but even more:
You need minimun 8 AWG or maybe 6 AWG cable, not 10 AWG. The heavier the less voltage drop.
I wired solar system battery banks & industrial inverters for a living a while back, and we used 2/0 or 4/0 cables for battery interconnects or main cables.
I recall one guy burned his barn down, by using (relatively) heavy 10 guage romex to wire his battery bank.
As the inverters ramped up to supply his 100 amp AC draw, over 400 amps of DC draw **ATTEMPTED** to flow thru his puny little Romex. Effect ? Instant toaster - the wire fryed thru the insulation, set the battery on fire.....
Undersized wire is that big a risk. Problem is, if your wire is moderately undersized, you won't likely notice it at low to medium draw, only at higher levels of power, then the danger is extreme.
Here's the basic formula. The inverter is beginning with 12 volts DC and converting to 120 volts AC, so your DC draw will be AC amp draw times 10.
500 watts AC / 120 volts = 4.2 amps AC draw times 10 = 42 amp DC draw thru your battery cables.
If I recall my amp limits per cable guage, 10 AWG is good for up to 30 amps, so it's too small for safety on that load. I'd go up 2 guages minimun, to 6 guage.
Do a yahoo / google search on amp & votage limits for cable to verify, I'm doing this by 10 year old memory.
Cable type affects this too. There is solid, large strand & fine strand copper cable, the latter being commonly called 'welding cable', and only available from specialty electrical houses, not Home Depot or Lowes. I much prefer this type cable for inverter applications.
Hope this is of some help to you.
Best Regards, David B.
PS: I'm in the process of hooking up a Trace / Xantrex DR3624
(3,600 watt / 24 volt mod sine wave industrial inverter) & battery bank with Solar Panels for my workshop & for light utility outage back up. It would be equivalent to a large scale RV / Bus system, except that I plan to have 8 to 16 deep cycle batteries in series & parallel.
alloro
10-09-2008, 03:08 PM
http://www.desertelectric.com/knowhow/table3.htm
B-300
10-09-2008, 05:08 PM
RamVanMan is correct about wiring sizing.... 10 gauge wire is 30 amp rated at about a 2.5% voltage drop.
In addition to what has been states most inverters are rated for peak power and will produce only a portion of that running continuosly. Also all amplifiers aren't 100% efficient and will draw about 150-170% of there output.
