| Author |
Message |
Henry Draper (146.129.147.36)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 27, 2001 - 3:14 pm: | |
Hi Folks:
Here's one for you electrical types.
I'm doing my reading in preparation for swapping out my perfectly good inverter for a more powerful one. (Seem that we busnuts do that frequently--change out a perfectly good item for a more powerful one. MORE POWER!!)
Anyway, my manual says that the inverter "...negative cable should be connected directly to the negative post of the battery bank.... Note: IF INSTALLING IN A VEHICLE, DO NOT USE THE VEHICLE FRAME AS THE NEGATIVE CONDUCTOR." (Caps mine.)
Why?
I recall no such caution in the wiring instructions for my current inverter--a Heart EMS-1800. In fact,the inverter negative and ground go to the same post on the frame of my Eagle right now. No problems, that I aware of, in the four or so years since I wired it that way. Have I just been lucky? I thought the frame of the bus provided the negative.
Thanks for any enlightenment you can provide.
Henry |
Jack Conrad (Jackconrad) (204.193.117.66)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 27, 2001 - 6:59 pm: | |
I just installed a Heart Interface 2500 inverter in our bus. My installation manual also said to run wire (minumum 2/0) directly to negative terminal of battery and maximum length of 5'. I think they want this done due to the amount of electrical energy that can be required by larger inverters. I used 3/0 cable. Manual also said to use a minumum 2/0 to interconnect batteries in house battery bank. If you connected negative cable from inverter to frame and had a smaller wire from the battery negative terminal to frame, this would be a weak link in system. Also you might create a longer path that energy would have to travel through. Longer distances= lower voltages/higher amps. Maybe some electrical engineers can explain this better, but this is my thinking on this subject. |
Jim Stacy (12.87.108.212)
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Votes: 0 (Vote!) | | Posted on Monday, August 27, 2001 - 7:58 pm: | |
The chassis ground is not necessarily a good electrical connection to the battery. Chassis grounds are often the cause of "come & go" problems in vehicles. Just a few ohms of resistance in the ground circuit could cause a voltage drop. That would be a big heat problem at the current levels drawn by a large inverter. You are ALWAYS better off with a hard wired connection to battery ground. It will eliminate a lot of problems in vehicle circuits. FWIW
Jim Stacy |
JayJay (152.163.201.209)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, August 28, 2001 - 12:12 am: | |
Henry... Jack and Jim are both right, but there is alot more to it than that. Voltage flowing thru the frame may create transient voltage spikes,capacitive reactance, or induced current aberrations in other equipment. In the newer "electronic- controlled" equipment this may affect proper operation. Older "dinosaur" (an Onan term)equipment was not as sensitive to these ailments. There is even more to it than this, but I won't delve into the more esoteric elements of sub-harmonics. Probably a good portion of the reason is to protect other equipment, as much as the inverter itself, since they tend to be rather sturdy. Cheers...JJ |
Steve Fessenden (63.27.89.1)
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Votes: 0 (Vote!) | | Posted on Tuesday, August 28, 2001 - 9:55 am: | |
I assume you are trying to keep the battery connnections manageable for removing batteries for service. I think that is a good idea if you can keep the wire sizes and lengths within specs.
If you are connecting to the SAME ground post as the battery ground with the lugs of the inverter and battery in direct contact, then you are not using the chassis as a ground circuit for the inverter and you can do it IF the total wire length and size is appropriate. The lugs have to be able to carry the high CONTINUOUS load, so no cheap thin lugs.
You could use a lug which has connections for two wires to connect to the battery negative and ground without any lug to lug connection to corrode and give trouble.
Here in Lakeland Florida there is one battery shop that has eveything you need in all size connectors, Batteries USA. The other shops don't have a full line of connectors and dont't tell you where you can get them. Probably the same in your area. You have to call them all.
Steve Fessenden |