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Old 07-19-2015, 12:39 PM   #1
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Alternator House Battery Problem

My house batteries are not adequately charging while underway (motor running no shore power). After a 6 hour run, and after connecting to shore power, the batteries recharge at a 50 amp rate for several hours, and then gradually return to full trickle charge. At the same time the shore power voltage drops to around 105-108 volts, and then gradually recovers to 120 volts overnight. The volt meter at the dash starts out at about 12.7 volts and during a 6 hour run drops to about 12.1 volts.

I replaced the house bank several days ago but the problem has not abated. I have checked all the connections that I can find, all were tight. The coach has 88K miles but is in good shape overall. Has anyone experienced a similar problem?

Thanks
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Old 07-19-2015, 01:22 PM   #2
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Alternator volts are low , should not drop below 13.2v and if battery state of charge is low the alternator should be putting out it's max, 14.2>14.4.
Possible poor connections between alt. and batteries or internal problems in the alt. it's self.

Note: A bad chassis battery can trick the alt. into thinking it's fully charged, so maybe the first and cheapest test would be to have the chassis batteries load tested.
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Old 07-19-2015, 01:33 PM   #3
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I'll add this in case you're reading my first post.

My coaches system ( BIRD ) for charging all the batteries , from the alternator , will not connect both battery banks to the alt. unless there is a 13.2v charge present from the alternator. Or when on shore power , the connection to charge the chassis batteries won't happen till the coach batteries are receiving a 13.2v charge.
If all your batteries are low , when you hook to shore power that would explain the convertor/charger running at max output and the load on your shore power voltage.
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Old 07-19-2015, 02:05 PM   #4
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Rob,

Not sure how the dropping shore power voltage relates, or if it even does.

So, let's start with the "alternator not charging" while driving. You mention that the house battery is not charging. Additionally, that 12.7 dropping to 12.1 on the chassis battery while driving (dash gauge) indicates that NEITHER battery bank is being charged.

Just need to do some basic troubleshooting of the alternator. What is the voltage reading at the B+ terminal of the alternator with the engine at 1000 RPM?

If 13.5 or more (should be around 14.2 VDC) check at the battery combiner. Should be the same.

Last check is at the battery for voltage at both house and chassis battery.

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Old 07-19-2015, 02:08 PM   #5
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Thanks for the reply Skip426

I suspect the alternator is the source of my problem. Both the house and chassis batteries are at 13.2 volts, with the charger off, as long as I am on shore power or running the genset. On the last leg of our trip (250 miles), I turned off the inverter and the batteries were still low (red light on remote panel) when we got in. I am wondering if I have some other load source that is depleting the batteries along with a weak alternator.
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Old 07-19-2015, 02:32 PM   #6
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Hi Brett

The voltage drop was due to the heavy load the charger was drawing to recharge the batteries.

The alternator is behind the radiator stack which is very cramped and inaccessible. I even tried to access it from under the coach. but you can't even see the back of the alternator from underneath. I can only reach one of the terminal wires (on the right side of the alternator) which is tight, but not the other one. I am 2K miles from home with limited tools etc. so this is a job for a professional.
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Old 07-19-2015, 03:22 PM   #7
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Rob,

Big caution: Do NOT take a chance on running the coach with low voltage on the chassis batteries. The engine and transmission computers do not do well on low voltage.

There is a work around if you do not want to address this until getting home.

Drive with the generator on. That will charge the house batteries. I would use a 24" battery cable-- 2 gauge or larger (any auto parts house and most Walmarts) to connect the house battery positive (terminal that goes to house) to chassis battery positive (either one since they are two 12 VDC batteries in parallel. Do this carefully and do not use jumper cables-- one of the jaws could jump off the battery post and the other end would still be connected to the other battery positive and would "arc weld" if it touched any piece of metal (ground).

With shore power at night and generator during the day, no problem.

Brett

This means that the two battery banks are now one.
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Old 07-19-2015, 06:07 PM   #8
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Three suspects:
1: If this problem affects both ENGINE and HOUSE: ALternator
2: IF it affects only HOUSE: ISolator 2B wires and connections
3: Excessive load on house batteries (IE: Residential fridge or absorption fridge on AC via an inverter.. I proved that one myself.)
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Old 07-19-2015, 06:18 PM   #9
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Think Brett is spot on--use heavy duty or double up jumper cables to connect house to chassis bats and run genny til you get to a repair facility--with alternator out, coach consumes a lot of bat power going down the road, so all symptoms appear normal and point to a failing/failed alternator.....
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Old 07-19-2015, 06:44 PM   #10
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One thing that my be worth a check , before taking the coach to a shop.
The alternator ; excite wire ( power from the ignition , to tell the alternator the engine is running) on some chassis , is protected by a fuse, as low as 5amps, so that fuse can be delicate.
Another member didn't know the circuit was fused or the location of the fuse box in the rear of his coach , until a new alternator was installed, his original was bad by a bench test and had blown the fuse, and the new alt. didn't work.
So a quick check of fuses may be in order.
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Old 07-19-2015, 09:01 PM   #11
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Thanks for all the help guys. I was wondering why I need to jump the house batteries to the chassis batteries. I thought the echo charger would charge the chassis batteries from the house bank if they were over 13.2 volts? My lowest chassis battery voltage has been 12.1 volts after a day's run.
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Old 07-19-2015, 09:29 PM   #12
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For clarity ... the Echo Charger passes charge voltage when the house charge voltage is > 13.0V and it is utilized to keep the chassis batteries charged while camping on shore power or when running the generator. The engine alternator can charge both battery banks via the battery isolator.

If the chassis batteries are not staying charged while traveling then the alternator is bad or perhaps you've accidentally disconnected or moved the "excite" wire that provides reference to the alternator. My coach charges at 13.9V - 14.1V while traveling according to SilverLeaf monitoring system.

I believe the suggestion of using a jumper cable is offered for emergency purposes ONLY. If both battery banks are charged while parked on shore power, then the Echo Charger is working and there's absolutely no need for a jumper cable.
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Old 07-20-2015, 07:48 AM   #13
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The echo charger functions based on a fully charged / actively charged chassis bats--above 13.6. However, the echo is little better than a trickle charger so it cant/wont keep up with a heavy draw like when the coach is being driven.

The reason for using the jumper cables while driving is so the genny can provide power to the house bats and the jumper cables can transfer it to the chassis to support engine and tranny ops while driving. It would be the same thing as keeping your "boost" button pushed while driving--no problem. Note: since the chassis and house bats are already cross-connected with a common ground, you only have to connect the positive posts on the house and chassis bats, doubling[using both cables] to connect the positive side ensures that std gauge jumper cables can withstand the continuous use until you can repair the alternator. PM me if you have concerns?????
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Old 07-22-2015, 12:09 AM   #14
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On this line. Does a 2002 have an echo charger. If so where would I look for it.

Maybe there is something with the echo charger wired wrong or something along those lines.
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