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Old 05-14-2008, 11:41 AM   #1
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Hi all, I have a 2005 MADP with 4 6-volt house batteries. I replaced the batteries with "better" Interstate batteries, because the original batteries began to lose their ability to maintain sufficient charge. The new batteries only slightly improved the condition, and certainly did not restore my boondocking capacity to the level of the original batteries when they were newer.
In an effort to determine why my capacity is not what I think it should be, I double checked the wiring for the new batteries.
There is a single, flat, black wire wired to a negative terminal that tests as 6 volts. It is not for the inverter, as the inverter works when it is disconnected. It does not show resistance as a ground, nor does it show voltage when disconnected, so I think it is not a wire for the charger. I have not checked it with the engine running to determine if is from the alternator.
Because it is connected to a terminal emitting 6 volts, I am thinking it is connected to the wrong terminal. If it is a ground wire for something, it should be connected to a "true" ground, not a ground terminal emitting 6 volts. If it is a "hot" wire, it should be connected to a positive terminal emitting 12 volts.
Due to the length of the wire, the most available alternative terminal is a "true" ground. Connected as is (to the ground emitting 6volts), all systems appear to function, although my battery capacity seems poor.
Can anybody identify this wire for me? Better yet, can anybody tell me whether it should be connected to a terminal with a 6volt output?
Thanks for you help.
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Old 05-14-2008, 11:41 AM   #2
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Hi all, I have a 2005 MADP with 4 6-volt house batteries. I replaced the batteries with "better" Interstate batteries, because the original batteries began to lose their ability to maintain sufficient charge. The new batteries only slightly improved the condition, and certainly did not restore my boondocking capacity to the level of the original batteries when they were newer.
In an effort to determine why my capacity is not what I think it should be, I double checked the wiring for the new batteries.
There is a single, flat, black wire wired to a negative terminal that tests as 6 volts. It is not for the inverter, as the inverter works when it is disconnected. It does not show resistance as a ground, nor does it show voltage when disconnected, so I think it is not a wire for the charger. I have not checked it with the engine running to determine if is from the alternator.
Because it is connected to a terminal emitting 6 volts, I am thinking it is connected to the wrong terminal. If it is a ground wire for something, it should be connected to a "true" ground, not a ground terminal emitting 6 volts. If it is a "hot" wire, it should be connected to a positive terminal emitting 12 volts.
Due to the length of the wire, the most available alternative terminal is a "true" ground. Connected as is (to the ground emitting 6volts), all systems appear to function, although my battery capacity seems poor.
Can anybody identify this wire for me? Better yet, can anybody tell me whether it should be connected to a terminal with a 6volt output?
Thanks for you help.
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Old 05-14-2008, 01:52 PM   #3
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927palmetto,

Does your unit have high and low light switches for the ceiling lights? On the high setting, the lights experience 12 volts. On the low setting (dimmer lights), it's 6 volts. Perhaps that's what the cable is for.??

I'm also interested in why you think your battery capacity is poor. What type (mfg.) batteries did you have before? And why do you think that the interstate U2200's are better?

The reason I ask is that since day one, our Essex has had 4 interstate U2200's. They have been changed once, with no significant change in apparent capacity. I've been complaining about lack of capacity for two years, and Newmar says that they can't find anything wrong.

On our coach, if you park it without shore power, we're lucky to get about 8 hours out of the batteries before the generator auto-starts to recharge, and that's with only the inverter on and nothing else. If you turn on an appliance (coffe maker, toaster, etc..), the voltage normally drops to about 11.3 volts with a fully charged battery bank. When you stop using the appliance the voltage will rebound back to about 12.3 volts. If you continue to use any appliance, you'll get 15 to 20 minutes use before the inverter trips off due to low voltage (11.0 volt cut-off). Does yours respond in the same manner?

I've concluded that the problem is one of an under-sized battery bank, and probably junky (interstate) batteries. I'm probably going to replace the flooded wet cell batteries with Lifeline AGM's. Although they have the same nominal rating, I believe they will perform substantially better under heavy amp draw conditions.

Let me know if you find some way to improve the performance of the interstate batteries. I'm real interested in doing the same.

Sebastian
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Old 05-14-2008, 04:28 PM   #4
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by 927palmetto:
Hi all, ...........
There is a single, flat, black wire wired to a negative terminal that tests as 6 volts. It is not for the inverter, as the inverter works when it is disconnected. It does not show resistance as a ground, nor does it show voltage when disconnected, so I think it is not a wire for the charger. I have not checked it with the engine running to determine if is from the alternator.........
......
........Can anybody identify this wire for me? Better yet, can anybody tell me whether it should be connected to a terminal with a 6volt output?
Thanks for you help. </div></BLOCKQUOTE>

My guess it is a battery temperature wire that goes to the inverter, to allow cutting off the battery charging inverter function should the batteries over-heat.

Check your inverter to see if the wire terminates at your inverter.

Good luck - Glenn.
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Old 05-15-2008, 02:16 AM   #5
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Sebastian, thanks for the reply. The original batteries were U2200's. I replaced with U2600's (I think), which were represented to have "better" capacity. They definitely were more expensive, and they weigh more.
My capacity slowly declined the third year of the original batteries. When I changed them, the "boondocking" capability was similar to that you describe for your Essex. The auto gen set would activate after about 8 hours.
My capacity is better than that now, but probably only about 50% of what it was when the coach (and U2200's) were new.
Since I didn't get the expected improvement with the new, bigger batteries, I began to suspect that there was a malfunction somewhere, hence the wiring check.
I checked each new battery with a load tester, all OK. Thus, I have come to two possible conclusions:
1. The newer, bigger batteries are not as good as the original U2200's; or
2. I have a wiring/device problem that has developed a parasitic load, and may have been the problem to begin with (before I replaced the U2200's).
The situation you describe with your Essex is indicative of a bad battery or a significant parasitic load. I assume you have load tested each battery, shut off the LP detector, and have gone through the "fuse pulling" regimen that might help identify the problem. There are a lot of threads available here on these issues if you need them.


Glenn, thanks also for the suggestion. That is a good guess, and if I can trace the wire (looks like that is going to be very difficult)and it goes to the inverter, I think you have nailed it.

Any other ideas on my original questions?
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Old 05-15-2008, 05:35 AM   #6
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927palmetto,

I had the unit at Kamp Newmar just last week. They said they checked and tested everthing. No abnormal parasitic loads (about 2 amps with the inverter off), batteries charge OK, and electrolite specific gravity OK. Since the unit has exbitited this same problem since it was brand new, and the batteries were changed (in kind) with no appreciable difference, I have to conclude that the battery bank is undersized and/or my batteries become junk after a few discharge/recharge cycles.

Whenever I calculate the amp-hour capacity of the battery bank (under usage), I come up with a value on the order of 100 amp-hours. This set of batteries is rated at more than 400 amp-hours. I seem to be getting only about 25% of the rated capacity.

If you figure out what the problem is, and how to get more capacity out of your batteries, please let me know.

Sebastian
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