Community Forums

VanDiemen23 · 06-21-2011, 10:39 PM

I have a 99 Beaver Monterey, and the first thing I did was upgrade the headlights to Hella e-code units. The factory sealed beams were pretty useless. Unfortunately, there's so much voltage drop between the batteries at the back of the coach and the power distribution panel at the front of the coach, that the lights are not only dim, but when the brights are on I get worried that I'll glitch the engine and tranny ECUs.

I also have six 55W docking lights spread around the coach to help in parking at night. When they're on the voltage is really low - there's probably 50A of 12V all together at that point.

Being the short DP model (30') it also is pretty light on the front axle. I had intended to make a big tube bumper (the area under the cap is completely empty) and fill it with rebar to help with the weight distribution and windy handling, and figured while I'm at it I can weld a couple of battery trays to the bumper and put two more chassis batteries up front, tied into the switched/unswitched power solenoid in the electrical bay. More usable power, and the weight is in the right spot.

The batteries will charge at relatively low current but supply additional power at peak demand without the voltage drop across 35' of cabling, because the lights are only 8-10 feet away. I tried this with a small battery from my start cart this evening, and the lights were noticeably brighter and a meter showed more than a volt higher than with the coach batteries alone.

Does anybody see any unintended consequences of this? The only thing I can think of is a potential ground loop between the front and rear batteries, and that could be taken out with an isolator, but then you drop a half volt across the diode in the isolator, and that's what I'm trying to avoid. An isolator would also prevent them from helping with starting, but that 35 ft of voltage drop at cranking current would probably render them pretty useless anyway.

Anybody try something like this before?

Kurmudgeon · 06-21-2011, 11:37 PM

A much simpler solution would be to run larger wire from the batteries in back to the distribution panel in front.

I had a similar problem with a 5th wheel once. The batteries were in front and the distribution panel was in the rear, and the wiring from front to back was only 12 gauge. I moved the batteries to the rear, right next to the panel, and wired them with less than 2 feet of 10 gauge to the distribution panel and converter. It completely solved the problem. For your 30 foot run, I would suggest at least 8 gauge, and 6 might be even better. Even if you put additional batteries in the front you are going to have to run wire from the rear.

JP

VanDiemen23 · 06-22-2011, 07:02 AM

It's already "0" gauge. I can't imagine dragging 000 up through all the nooks and crannies to the front, as well as putting loom on all the chafe spots.

hdossett · 06-22-2011, 05:21 PM

Quote:

Originally Posted by VanDiemen23

It's already "0" gauge. I can't imagine dragging 000 up through all the nooks and crannies to the front, as well as putting loom on all the chafe spots.

So... just run another pair of '0', in parallel, That would double the current carrying capacity

H

RJay · 06-22-2011, 05:45 PM

Hi Rick,
Suppose you mounted a converter close to the center of your load. It would be much cheaper to run AC wiring compared to 00 wire which is $15/ft. The only problem would be space to fit it. I'm sure you could find a physically small unit since it doesn't have to have 3 stage charging just 120 volt AC to 12 volts DC. An 800-1000 watt unit should do it for you.

Kurmudgeon · 06-22-2011, 09:02 PM

Quote:

Originally Posted by VanDiemen23

It's already "0" gauge. I can't imagine dragging 000 up through all the nooks and crannies to the front, as well as putting loom on all the chafe spots.

If you already have "0" and that much voltage drop, I think you have some other problem you need to be looking for. A bad ground or an area of high resistance in the circuit. Even the 50A load you mention should be handled easily by "0" wire. I believe it's rated for more than 200 amps. If the distance from the source to the load is 30 feet, and the load is 50A, using "0" wire you should see about a .3V drop at the load. If it's greater than that, you need to be looking for some kind of problem.

We have at least a couple of members here who are electrical engineers. Hopefully one of them will have something to offer.

JP

pkmesser · 06-22-2011, 09:31 PM

Quote:

Originally Posted by Kurmudgeon

If you already have "0" and that much voltage drop, I think you have some other problem you need to be looking for. A bad ground or an area of high resistance in the circuit. Even the 50A load you mention should be handled easily by "0" wire. I believe it's rated for more than 200 amps.

We have at least a couple of members here who are electrical engineers. Hopefully one of them will have something to offer.

JP

Two items to note:
1. Another convertor will only help if you are running the generator all the time you need lights.
2, Wire size, you can look up, by running a search on the internet, what the voltage drop is in wire size vs amps vs distance. (you need to do this for dc, the voltage drop for ac is less) For a given wire size, as the amps go up, the voltage will drop, increase the distance, and the voltage drops more. Wire is rated at a given amperage, based on it's ability to survive, not on what will happen to the voltage drop. Now this sounds negative for you, but if you are running 50-60 amps, you should not have an appreciable voltage drop over that distance. If you were running 200 amps, the voltage drop would probably be at at least 2 volts.

VanDiemen23 · 06-23-2011, 12:04 AM

Actually, I am an electrical engineer - but theory and practice are frequently considerably different and without a detailed schematic pretty moot. I can see where the cable leaves the engine bay, and enters the distribution box, but there probably isn't six inches of visible cable anywhere else, so splices, taps, etc are a total unknown. There's no existing Beaver Monterey schematic that anyone on the BAC knows of, including the guys in Bend.

But you did get me thinking to attempt to draw the whole thing out using an older Patriot schematic as a point of departure, and check each node I can get to with a meter. Could be a high-resistance connection somewhere. If I was a betting man I'd guess one of the solenoids.

bigfeather · 06-23-2011, 12:35 AM

My money is on the high resistance... I agree that larger cable would be too stiff to route when all you really want to do is get your lights to be brighter. Maybe you can just isolate the lights power and feed them with a direct continuos cable (suitable gage, of course) from the chassis batteries instead of trying to cut the drop in half with a heavier main cable. Be sure to add a fuse or CB at or near the source (chassis batteries) and run the new lead through the lights' existing circuit protector as well so if it ever shorts along the run, it won't cause an electrical fire.

alvinc · 06-23-2011, 01:56 PM

Single 0 wire is good for 70 feet at 50 amps and a 3% voltage drop. Keep in mind that the 70 feet is the round trip distance, so it really is only 35 feet.

Also consider the ground system. Is the chassis ground in good shape.

If you do decide to run more wire, use wire that is made up of fine wires. It will be more flexible and easier to snake. An example:
Ancor Marine Battery Cable

Another idea might be to measure the voltage drop of the ground. That is, at the end of the 1/0 cable, use a voltmeter to measure the drop from the cable to the chassis ground. The run another wire from the battery to the end of the cable (IE an independent ground). If the voltage drop is lower using your independent ground, then the ground system is the problem.

Ray,IN · 06-25-2011, 09:40 PM

Another approach is to use the existing headlamp wiring system to control a relay energizing a new, separate heavy gage wire harness feeding the headlamps. This is very common on GM pickups.

Happycarz · 06-26-2011, 09:17 PM

A while back another poster discovered he had a poor splice in the cable mid ship, causing high resistance and low voltage. I did a search, to no avail. With the circuit under load, you might want to remove the bay storage ceiling covers and probe the cable at different points to see in there is a voltage drop caused by a splice.

VanDiemen23 · 06-26-2011, 10:54 PM

The headlight switch. 11.6V At the distribution panel. On the way to the lights it's 9.2. It's a huge switch - so it probably can handle the majority of the current, but it must be on its way out.

Funny thing is the coach voltmeter must use that lighting circuit as it's reference, because it's seeing around 9, but the Silverleaf reads 12.4 - probably getting it's reference from the engine computer's power.

Nuge · 06-26-2011, 11:42 PM

If it was me with this problem, I'd be installing the heavy gauge welding cables in steel conduit right under my unit, but I'm just a steel mill electrician, not an engineer....It's what I use for my trolling batteries when I run my 36 Vdc trolling motor. With my older vehicles I annually go through all my heavy battery connections; cleaning them and greasing them to keep the air and oxidation out of the connection.