Carl L
Moderator Emeritus
wylecoyote said:
Sure they do. How do you think they pick that cotton before the bolls get rotten in those old cotton fields back home? 8)
12 volt
- Thread starter janpaul
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Sure they do. How do you think they pick that cotton before the bolls get rotten in those old cotton fields back home? 8)
I have a fifth wheel with 2 ultima deep cycle batteries. I do a lot of dry camping and short drives between stops ( 2 hours ). I bought a battery isolator and ran a #4 wire to the back bumper and a separate 50 amp plug direct to the trailer batteries. I can pretty well run the trailer batteries down and charge them in 2 hours of driving. My problem is two years in a row now my isolator has failed a month after our 20,000 mile trips. Never while hooked to trailer batteries - both times it has failed when driving around without the trailer. Warrentee has replaced both isolators and I bought a different brand the second year even though I have a guarantee replacement. Any one else have this happen? I travel 8 months and run just the truck 4 months. I get 40 amps at trailer batteries with the heavy wire rather than the 8 amps through the 7 pin connector. I would not pull without and isolator even if I have to buy a new one each year. Alan Day 2005 HD 8.1 liter gas (Diesel smells).
Karl
Moderator Emeritus
What kind of isolator - diodes or solenoid? Do you ever use a regular battery charger for the trailer battery while hooked up to the truck? Where is the isolator - in the trailer or in the truck?
it is a diode 120 amp isolator mounted within 18 inches of the alternator. No I have not used battery charger while hooked to truck or plug into shore power while hooked to truck. Both isolaters failed after about 3 months of driving without a trailer. Alan
Karl
Moderator Emeritus
Hmmm... If your alternator is not too large for the isolator, that doesn't leave too many things to go wrong. The most obvious is excessive heat. Most isolators (and other electronics) are rated for 75 degC. That works out to about 167 degF. - not uncommon in some areas of the engine compartment. I suggest you check your mounting placement and make sure it isn't directly over any exhaust manifolds or in the flow of radiator heat. Also mount it vertically so the cooling fins are straight up and down; not horizontal.
How does it fail? Does it cook itself? Some diodes and power transistors will go into avalanche mode or thermal runaway (respectively) when they reach a certain temperature, and destroy themselves. Surprisingly, when a diode fails, it will usually short out completely rather than blowing like a fuse. If you still have one of the failed units, you can run a simple test. Connect a multimeter set to Ohms, positive lead to the alternator terminal and negative to one of the battery terminals. It should read a low resistance. Now reverse the leads. It should now read a very high resistance. If both readings are either very low or very high, you've found the failing diode. Do the same with the other battery connection. Chances are good that only one has failed; the one that feeds the truck battery. Of course that won't solve your problem, but if only one diode is bad, you could use the good side as an emergency backup should your new unit fail too. You can test the in-vehicle unit that way too, but make sure you remove all the battery and alternator leads before doing so, and pull the negative cable off the battery before doing that.
It's also possible that you simply got two bad isolators; not likely, but possible.
Let us know what you find.
One more thing: Make sure the isolator case is electrically connected to the chassis. Run a separate wire if necessary.
How does it fail? Does it cook itself? Some diodes and power transistors will go into avalanche mode or thermal runaway (respectively) when they reach a certain temperature, and destroy themselves. Surprisingly, when a diode fails, it will usually short out completely rather than blowing like a fuse. If you still have one of the failed units, you can run a simple test. Connect a multimeter set to Ohms, positive lead to the alternator terminal and negative to one of the battery terminals. It should read a low resistance. Now reverse the leads. It should now read a very high resistance. If both readings are either very low or very high, you've found the failing diode. Do the same with the other battery connection. Chances are good that only one has failed; the one that feeds the truck battery. Of course that won't solve your problem, but if only one diode is bad, you could use the good side as an emergency backup should your new unit fail too. You can test the in-vehicle unit that way too, but make sure you remove all the battery and alternator leads before doing so, and pull the negative cable off the battery before doing that.
It's also possible that you simply got two bad isolators; not likely, but possible.
Let us know what you find.
One more thing: Make sure the isolator case is electrically connected to the chassis. Run a separate wire if necessary.
I still have the second isolator and will run ohm test. Both units quit allowing charge to go through to Battery and I got a not charging warning on the dash. The first unit was mounted horizontally on firewall and somewhat above exhaust manifold. Second unit was mounted to plastic and vertically. May have been heat on first one and lack of ground on second. I thank you for your suggestions. Will let you know what I find. Alan
Karl
Moderator Emeritus
Alan,
Your welcome, but I hope that's the problem. I will suggest you mount the diode to a piece of aluminum about 4" or 6" square (or any shape, really) and at least 1/8" thick, then mount that to the chassis. Compared to aluminum, steel is a very poor conductor of heat. Let me know if that takes care of it.
Good luck!
Your welcome, but I hope that's the problem. I will suggest you mount the diode to a piece of aluminum about 4" or 6" square (or any shape, really) and at least 1/8" thick, then mount that to the chassis. Compared to aluminum, steel is a very poor conductor of heat. Let me know if that takes care of it.
Good luck!
I am about to head out with my battery isolator installed but when I mount the isolator away from heat (actually on right fender well) I will need a longer wire from allternator to isolator and back to truck electrical system. 2005 Chevy 8.1 liter 2500 HD. I need a circuit breaker between allternator and isolator. But what size???? There is a fusable link now from allternator to truck system but no clue as to amperage. I stopped at Chevy dealer and service guy did not know amperage of link and did not have any suggestions to help me. I know I have a 90 amp allternator but am thinking of a 50 amp circuit breaker in the line between the allternator and isolator. Any thoughts? or suggestions?? Alan in Gatlinburg
Karl
Moderator Emeritus
Why not just splice in a piece of same size or preferably larger wire to the fusible link wire?
Splice is a good option. I did not want to have another joint that might get corroded or? But cutting the end off and soldering a wire onto that will be long enough and big enough, (and heat shrinking insulation on joint). Since I cannot find the rating on the fusible link. Thanks. Alan
Karl
Moderator Emeritus
Alan,
Don't just solder the joint, use a copper screw clamp connector found in the electrical department of any home supply store. Seal the finished connection with several coats of Plasti-Dip, the stuff used for coating screwdriver and plier handles.
Don't just solder the joint, use a copper screw clamp connector found in the electrical department of any home supply store. Seal the finished connection with several coats of Plasti-Dip, the stuff used for coating screwdriver and plier handles.
