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Old 08-31-2017, 03:28 PM   #1
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Pace Arrow chassis battery being discharged

Hello folks,

I’m trying to help out an older friend, a retired Navy Commander, with an apparent problem in his 03 34’ Pace Arrow built on a Workhorse GM 8.1 / Allison 1000 chassis. He’s had it since new, has put 58K miles on it, and seems to have kept up on maintenance.

I have a background in electrical and electronic stuff, and have successfully done troubleshooting on a number of old cars and locomotives. While I’ve been in and helped drive various friends’ RVs, I’ve not owned one and have not had to think about fixing things and thus am new to this world. The various posts here on battery issues have been extremely helpful in getting more up to speed, so thanks, guys! This current one is a problem I haven’t seen mentioned.

I’ve done various voltage and current measurements over the past week+, and it looks like:

* both chassis and coach batteries get charged, presumably normally, from shore power, the generator, and the engine alternator
* when parked, shut down and no shore power, both chassis and coach batteries disconnected by the panel switches near the door, the battery voltages drop slowly – basically .15V in 43 hours for each starting from a fully charged condition
* the chassis battery, completely isolated by disconnecting the negative lead, shows no voltage change at all in 24 hours

So it would seem that the batteries are reasonably good, but I don’t yet know how old they are. Don’t yet know the brand, either, as the chassis battery has a big “AAA” sticker on the front face (which implies a past problem) and I haven’t yet found the coach battery – perhaps it’s under the removable step tread by the door.

But anyway, the issue is that, parked with no charging going on, the chassis battery gets discharged even when it is “disconnected”, as long as the coach battery is “connected”. “Connected” and “disconnected” in this case is via the panel switches by the door. Discharge currents are measured in the negative lead of the chassis battery. No known accessories are turned on. Here’s what happens:

* chassis and coach connected, .82A
* chassis disconnected, coach connected, .79A ** does not seem right
* chassis connected, coach disconnected, .03A
* both disconnected, 0.0A

So I suspect something wrong with the Battery Control Center. It is an RV Custom Products type GAS F73-1020.

Does this seem a reasonable conclusion? What other things should I know to be more informed when this goes to the shop? Or perhaps it’s a simple fix that I could do?

TIA,

Larry H.
Bend, OR
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Old 08-31-2017, 03:54 PM   #2
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Since the house batteries seem to be working fine and charging I wonder if there's a solenoid that is permanently connecting the two batteries together. I guess you could plug in and see if the charging voltage is getting to both sets of batteries all the time. Typically the converter only charges the house batteries. This is not always the case however.
You've been thorough and I'm sure help is on the way.

Good luck!
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Old 08-31-2017, 04:06 PM   #3
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If you give RV Custom Products a call they will email you the troubleshooting guide for the board.

14000 Anson Ave, Santa Fe Springs, CA 90670
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Old 08-31-2017, 04:35 PM   #4
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Batteries can discharge due to internal short. Can you take the batteries to local auto parts store and have due a "impedance" test? Don't rely on the results of a 'load test". If shop doesn't do impedance testing, then find another shop (they're too outdated in their shop technology/tools).

BU-902: How to Measure Internal Resistance – Battery University

I use a tester by Midtronics but there are plenty available - such as https://www.ebay.com/sch/i.html?_odk...ester&_sacat=0
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Old 09-01-2017, 11:15 AM   #5
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Hi guys!

thanks for your suggestions. I called RV Custom and they are emailing the troubleshooting guide but it hasn't shown up yet. Will ping them again. Did find one posted online but without schematics referred to in the text. Good to learn that some of the parts in the BCC are available. I see that the behavior of the BCC is different depending upon the ignition switch position. All of my tests were with the ignition off so I need to revisit that.
And to specifically check out the Aux Charging relay.

On a Fleetwood page I see that the house batteries are in the 220 A-Hr range; I think they discharge more quickly than that under load and so battery tests are indeed in order.

This is one of several tasks I'm juggling so progress will be slow. I'll let you know what I find.

Thanks again!

Larry.
Bend, OR
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Old 09-01-2017, 11:49 AM   #6
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i would look at the batteries and see if someone hasn't hooked something directly to the batteries bypassing the panel
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Old 09-01-2017, 12:21 PM   #7
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Some coaches rely on a trickle charger to charge the chassis batteries. It is plugged into a 110 volt outlet that is powered by the inverter when hooked to shore power or if the generator is running. When no outside power is available, the trickle charger can slowly drain the chassis batteries. The instructions are to remove the fuse to the TC when power is not available. I had this very problem with my coach. I remover the TC and installed an Amp-L-Start. No more dead chassis batteries.
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Old 09-02-2017, 01:01 PM   #8
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Guys,

I wasn't able to connect with RV Custom yesterday but did find another posting of their Fleetwood BCC Troubleshooting guide with schematic. Very helpful. I also learned that the coach batteries are only 4 months old.

The smoke was blowing away from us so you could actually breathe outside, and I got in a productive hour of measuring. Found the coach batteries to be pristine looking Trojan T-125; when I disconnected the + lead the open circuit voltages exactly matched the Trojan spec sheet for a fully charged battery at the 90° ambient temperature. Not as insightful as an impedance test, but a hopeful sign.

Then I started probing the BCC, with shore power unplugged. Bottom line is that the Aux/Charge relay is pulled in whenever the coach battery is "connected", no matter what else is going on, resulting in a constant drain on both sets of batteries. Not what it's supposed to be doing. If the coach battery is "disconnected", then the Aux relay responds to the switch on the dash as it should. The contacts also seem to be OK, measuring .08V between battery bus bars when pulled in, less than the .1V limit mentioned in the troubleshooting guide.

On the BCC board schematic is a dashed box labelled "Bi-Directional Charge Relay Delay Control". Does anyone know of a schematic for what's in that dashed box? And what ballpark of delay are we talking about, a few seconds, or hours? The troubleshooter mentions in passing that the Aux relay doesn't drop out immediately after the engine is shut down. In this case though, it's been shut down for a week.

Absent info on the circuit, next I think I'll look for a shorted power transistor driving the Aux relay. Power handling devices are the more likely to fail, and a replacement board is about $250, so it's worth it if a little more time can ID a failed $5 transistor. The present board would have to come out in either case.
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Old 09-02-2017, 02:28 PM   #9
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Hi Larry! Welcome to IRV2! We're sure glad you joined the gang!

Sorry I can't answer your question.

Good luck, happy trails, and God bless!
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Old 09-02-2017, 11:58 PM   #10
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That's odd RV Custom didn't email the TSG and schematics they normally do it quick. Maybe because of the holiday they are short handed .
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Old 09-04-2017, 06:02 PM   #11
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It's partly my doing, since Friday was pretty clear and I was doing a number of other chores outside. Didn't call them until after 3 and discovered they are a "morning" company.

Yesterday I determined that the PC board logic in the BCC is probably bad. I disconnected the shore power and turned on every light inside, and watched the Aux relay drop out as the coach battery voltage decreased. But not until it was down to about 11.6V, as opposed to the 13.6V listed in the TSG. If forced to drop out by "disconnecting" the coach battery it would stay out, but once pulled back in after seeing higher voltage it would again not drop out until that 11.x voltage. This of course is bad news for the chassis battery, which is not a deep-cycle design.

With shore power reconnected (or generator running), watched Aux relay pull in at 13.2V on the way back up, as described in the TSG. Also saw a minute or two delay between the time the threshold voltage was crossed and the action of the relay, which helped explain some seemingly curious results I got last week.

The voltage measurements were taken right at the battery inputs to the BCC PC board with a known good meter, because along the way I realized that the meters on the inside panel were routinely reading .20 - .25V lower than the actual battery voltage. I have no idea where they are measuring but it's obviously not right at the batteries.

Found some service receipts, and he's been having chassis battery problems for some time, many years, but seems to think they were not abnormal. Staying at sites plugged in to power would have masked the problem, conversely after long periods of storage battery problems are expected. And given the various time-consuming "gotchas" I've encountered, it's easy to see how a service shop could have found no trouble. Once I'm sure of the results I'll post a list of the good measurement conditions.

So tomorrow I'll call RV Custom again and see what I can learn about the PC board. Given its age and the possible use of early lead-free solder, it might be smarter to just replace instead of trying to repair it. I'll check on that as well.

Following up on "Crasher"s idea, for completeness I wanted to look at the DC output of the AC converter to see if it's being a drain when off, but I can't find the bloody thing. The owners' manual says under the fridge or stove, but all I see there is ducting. The AC breaker and DC fuse panel is instead in a little cubby to the right of the bedroom TV. The space is deep enough that something could be behind the breaker panel, and the AC output from the generator heads right up toward that vicinity. Tomorrow I'll try to pull the panel and look. Anyone know for sure what's back there? This is an '03 34W model.

Thanks!
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Old 09-05-2017, 12:07 AM   #12
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Sounds like good progress in finds thd problem. The converter is most likely behind the panel.
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Old 09-11-2017, 03:07 PM   #13
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Hi guys,

I called RV Custom last Tuesday and received an email with the information packet in about 5 minutes. Yay Mary! It was much more complete than previous Troubleshooting Guides I’d found, covers up through Rev. P of the CB-115 board (the current one), and most importantly, corrects a significant typo in earlier versions of the document. That typo lead me to suspect the PC board in their BCC had failed. For Fleetwood applications, the correct value for dropout of the AUX/Charging relay is 12.6V coach battery voltage (ignition off), up through Rev N. But there is also a measurement technique involved, which the TSG doesn’t mention. More on that later.

I also got a call from their electronics guy, and we had a great and productive discussion during which we went over a number of circuit details. I learned that, for boards up through Rev. N, it shouldn’t be possible to see the difference in pull-in vs drop-out voltages that I had as it is electronically hard-wired, and he told me of the unmarked test point where I could measure when the monitoring circuit tripped. There is a 10 second delay between circuit tripping and relay action, in both directions, and meanwhile the measured battery voltage is changing.

So I remeasured the relay behavior and sure enough, this older Rev D board is just fine. The “gotcha” is that you can’t wait to hear the relay click and then quickly look at the coach battery voltage; you have to be watching the meter constantly as the voltage nears the trip point and then extrapolate back 10 seconds after the relay acts. In this case, the voltage immediately dropped to 11.6 after AUX dropped out and the chassis battery was no longer trying to charge the coach one. And so I misread the dropout voltage when I didn’t yet know about the time delay.

That 11.6V reading had been bothering me since the RV had been plugged into shore power several times over the past couple of weeks, so that now became the focus. I found the coach battery and measured discharge current there; just .15A when “connected” and obvious loads turned off, and zero when “disconnected”. And only a few Amps of charging current when plugged in to shore power. So I left it overnight physically connected only to a separate smart charger.

Finally found the AC converter; it was indeed under the fridge but essentially hidden from view through the vent grilles. It turns out to be a Progressive Dynamics 9100 series, without the Charge Wizard. (The items behind the AC breaker panel in the bedroom turned out to be the AC power transfer switch and the control module for the bedroom slide.)

The coach battery charged up better and I found the smart charger in “maintain” mode. That night I did a load test, turning on enough interior lights to make a 10A load. In the first 20 -30 minutes the terminal voltage dropped gradually and then maintained that value for the rest of the hour. The voltages suggest about 75% charged and an internal resistance of about .02 ohms, which seems high. I did another session with the smart charger while scaring up a Charge Wizard at a local RV dealership. Another load test with generally similar results except a suggested charge level of 80%. BTW all of the open circuit voltage measurements were done with a separate, known-good meter connected directly to either the battery terminals or the battery connections at the BCC board, after at least an 8-hour rest period, making for slow going.

With the Charge Wizard plugged in the AC converter went straight into “Boost” mode. After 4 hours of that I got a little nervous since it was also connected via the AUX relay to the chassis battery, which is a sealed design, so I manually set it into “normal” mode. A few minutes later I decided to just leave everything off overnight since it was the first time running with the wizard.

Next morning the open circuit voltage of the coach battery was right up there at 12.74V. I plugged in shore power again, the wizard went into normal charging mode, and I left it that way, making sure that I turned nothing else on to simulate storage. After 32 hours (vs nominal value of 30) it switched into “storage” mode, and is still there. I’m waiting to catch it doing the 15 minute equalization charge after an additional 21 hours. After that there’ll be another load test followed by watching for the wizard to switch out of “boost” mode back to “normal”.

These coach batteries are 4 month old Trojan T-125, a nominal 220 A-hr design. I don’t know their entire history, but I’m now thinking it is entirely possible that they’ve never been fully charged since installation. It’s also possible that at their last campsite, my friends were actually running off of battery when they thought they were running off of shore power. I suspect that because when I first plugged in the shore cable it kept tripping my GFI outlets. Thanks to various posts on this forum, I traced that to a bad ground circuit because of oxidized prongs on the power cord plugs from the refrigerator. After fixing that I got on with figuring out the chassis battery drain issue. Anyway, the 4-hour drive back home wouldn’t have been enough to recharge depleted coach batteries just from the alternator.

So it now appears that the answer to my original question is that it was depleted coach batteries that were draining the chassis battery. Both sets were down to 9V that morning before the eclipse that I almost didn’t get started, so I hope there hasn’t been too much of a hit on capacity.

Thanks for your helpful comments, and especially to “chboone” for the contact info for RV Custom, and to “CountryB” for the link to Battery University. I thought I knew a fair bit about batteries but there was a lot more there to learn about lead-acid designs, especially deep cycle ones. In addition to the RV Custom TSG and schematics, papers I found especially helpful were:
http://batteryuniversity “dot” com/learn/article/how_age_affects_capacity_and_resistance
http://www.trojanbattery “dot” com/tech-support/battery-maintenance/
http://www.progressivedyn “dot” com/service/battery-basics/

This is already way too long of a note, so in the next day or two I’ll post the measurement procedure I should have followed.

Thanks for your help!

Larry.
Bend, OR
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