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Old 11-28-2016, 10:55 PM   #1
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Default there is a small drain on my battery

Hi, hoping someone here can help me, it seems that just recently there appears to be a small drain on my chassis battery, I went to go start it yesterday, and the battery was drained enough that I couldn't start the van, I proceeded to put my battery charger on , and charged it for a good 8 hours, it started up no problem, my battery meter shows it at a full charge, I took it out for a good 1 hour ride, when I put it away , the meter showed11.9 volts, today I came home from work and decided to check it with the meter, and its only reading 11.2 volts, I have not had this discharge problem before, I went through the whole van, making sure everything is turned off, I know there is a small wire to the radio to keep memory, but I doubt that would be the reason, its a 6 month old battery form Costco, any ideas would be greatly appreciated, thank you,,,
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Old 11-29-2016, 12:11 AM   #2
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Check to make sure the light inside the rear doors is off if you haven't already.

Next up would be to test the isolator. Googling the brand of your isolator + diode + ohm + meter should result in instructions for testing the isolator.
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Old 11-29-2016, 12:45 AM   #3
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Hi, hoping someone here can help me, it seems that just recently there appears to be a small drain on my chassis battery, I went to go start it yesterday, and the battery was drained enough that I couldn't start the van, I proceeded to put my battery charger on , and charged it for a good 8 hours, it started up no problem, my battery meter shows it at a full charge, I took it out for a good 1 hour ride, when I put it away , the meter showed11.9 volts, today I came home from work and decided to check it with the meter, and its only reading 11.2 volts, I have not had this discharge problem before, I went through the whole van, making sure everything is turned off, I know there is a small wire to the radio to keep memory, but I doubt that would be the reason, its a 6 month old battery form Costco, any ideas would be greatly appreciated, thank you,,,
Make and model year?

Before doing anything else, rule out an alternator issue. With the engine running, what voltage are you measuring at the chassis battery? It should be in the whereabouts of 14 volts.
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Old 11-29-2016, 01:21 AM   #4
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... my battery meter shows it at a full charge, I took it out for a good 1 hour ride, when I put it away , the meter showed 11.9 volts...


Your alternator is not charging.



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Old 11-29-2016, 01:48 AM   #5
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a battery once discharged will not recharge to it's previous capacity.

you have a costco warranty- take it in and exchange it.

before you use it, charge the battery fully- this will extend it's life.

a charger is a charger a "battery tender" is a tender- is tends to an already charged battery.

it is good to have both.

you can also get a battery disconnect to use when the vehicle is parked for a time if you don;t care about he alarm, power door locks and radio memory.

it is possible your alternator is at fault, once you have a known good battery in the vehicle you can test at autozone for free- a bad alternator diode may allow the battery to drain back thru.

below is cut and paste from earlier post in another thread:


My Chev 3500 used 1.4 amps when sitting when I first got it...the things which stay on are doorlocks, alarm, power mirror, speedo cluster and radio.

by pulling each of my fuses and cleaning the contact legs, I reduced this draw by 1/2. it now draws 700mA when sitting.

even so, I don;t need alarm, doorlocks or radio memory, I disconnect the battery when parked behind our gate.

cleaning the fuses is a fun task- I also have fuses under the driver's seat ( much cleaner)...to make it easy- with battery disconnected i did all the reds, all the blues, all the greens- makes for less label reading of who goes where.

clean the legs with a fine file, scotchbrite or emerypaper- I found the file quickest- and then add a little dielectric grease.

these are the fuses out of one of my bikes- after about 4 years use in a dry climate, before and after:








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Old 11-29-2016, 07:05 PM   #6
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Thanks for all your replies, the meter does show 14 volts when the motor is running, that is why I didnt think it would be the alternator,
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Old 11-29-2016, 08:09 PM   #7
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Thanks for all your replies, the meter does show 14 volts when the motor is running, that is why I didnt think it would be the alternator,
An alternator can show the correct operating voltage but have a leaky or shorted diode (there are typically six) than can result in a battery discharge when the vehicle is shut down but this is fairly unusual and is less likely the cause than a bad battery or some excessive parasitic load.

More likely either the battery is defective or there is a higher than normal parasitic load on the battery when the engine is off. A couple of simple tests can provide some clues.

After bringing the battery up to a fully charged state, remove the positive cable and measure the battery terminal voltage after 24 hours. If it's in the vicinity of 12.6-12.8 volts. the battery is most likely not the problem. The next thing to check is the parasitic load on the battery which can be done if you have a digital meter that can read amperes. With the meter in the ampere mode, connect the positive (red) lead to the positive battery terminal and the negative lead to the disconnected positive battery cable. Start with the highest ampere scale, (typically 10 amps) and measure the draw.
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Old 11-29-2016, 09:33 PM   #8
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an alternator should put out 14.8 VDC...the stator will produce AC volts which is rectified ( turned into DC) by diodes and regulated to below 14.8 VDC to the battery*


IF an alternator diode is bad aside from a possible drain back there will be AC on the line- so a voltmeter set to AC will get a reading - if the diodes are good there will be no AC, just DC. an easy way to check.

check the easy stuff first.
a duff battery will skew just about all readings- a known good battery is step 1

mike


*the diodes in many battery isolators ( if applicable) will often drop the voltage to the batteries to about 13.5 ( still sufficient for battery charging and good service life).
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Old 11-29-2016, 11:33 PM   #9
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Thanks again for all your replies, I checked it today after work , and it reads 11.1 volts, so it is dropping a little bit each day, I will try that battery test, and keep going from there, thanks again for all your input,,,,
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Old 11-30-2016, 12:59 AM   #10
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an alternator should put out 14.8 VDC...the stator will produce AC volts which is rectified ( turned into DC) by diodes and regulated to below 14.8 VDC to the battery*


IF an alternator diode is bad aside from a possible drain back there will be AC on the line- so a voltmeter set to AC will get a reading - if the diodes are good there will be no AC, just DC. an easy way to check.

check the easy stuff first.
a duff battery will skew just about all readings- a known good battery is step 1

mike


*the diodes in many battery isolators ( if applicable) will often drop the voltage to the batteries to about 13.5 ( still sufficient for battery charging and good service life).
Even if the diodes are in perfect condition there will still be ripple on the DC feeder for a couple of reasons. There is inherent AC ripple in the alternator output, the level of which is dependent upon the number of diodes employed and the state of the battery which acts as a primitive filter. There is also inherent diode leakage in the family of diodes typically used in this application. So there will always be a measurable AC component but if the level is less than 100 millivolts (20 mv would be ideal) it would be reasonable to rule out diode failure in the alternator.

Whether battery isolators drop voltage delivered to the batteries is dependent on the particular installation. Early on, the diode voltage drop (around 700 millivolts did result in lower battery charging terminal voltage with some long term consequences for battery life. Subsequently, this was addressed by a sensing terminal on the alternator that observed battery terminal voltage during charging and compensated for any losses by increasing alternator output voltage. Today, alternator operation is pretty much computer controlled. The computer is flashed for a target charging voltage, typically ambient temperature defined and if it sees a disparity between the target voltage and the actual battery voltage, it adjusts the alternator field current to compensate for it.
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Old 11-30-2016, 01:09 AM   #11
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Thanks again for all your replies, I checked it today after work , and it reads 11.1 volts, so it is dropping a little bit each day, I will try that battery test, and keep going from there, thanks again for all your input,,,,
Yank the positive cable from the battery. Put it through a charge cycle. The battery at this point should be around 13 volts and should gradually decrease to a resting point somewhere around 12.6 volts. Leave it for 24 hours without reattaching the hot cable and check the voltage. If it reads 11.1 volts at this point, the battery is kaput, most likely from a partially shorted cell. If it is still in the whereabouts of 12.6 volts the next step is to selectively start pulling circuit fuses to find the culprit.
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Old 11-30-2016, 01:33 AM   #12
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Cruising:
Very nice summary of the nuances of alternator behavior.

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Today, alternator operation is pretty much computer controlled. The computer is flashed for a target charging voltage, typically ambient temperature defined and if it sees a disparity between the target voltage and the actual battery voltage, it adjusts the alternator field current to compensate for it.
This has been true for awhile, but in the newest designs (e.g., the Sprinter I4 engine) it no longer works that way. These new "smart" charging systems have elaborate algorithms that dynamically change the target voltage in order to optimize engine power and fuel economy. For example, they lower the voltage (and thus the current) during acceleration, and raise it during coasting. Many of them initially deliberately under-charge the battery so there is room to harvest otherwise wasted energy during coasts (kind of like dynamic braking in hybrids).

These new systems can be problematic when used with traditional RV charging setups. My 2014 Sprinter I4 was quite poor at coach battery charging, despite having a 200amp alternator. This is one reason why I decided to install a second engine alternator. My coach is now happily independent of the exotic chassis electrical system.
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Old 11-30-2016, 02:22 AM   #13
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Cruising:
Very nice summary of the nuances of alternator behavior.



This has been true for awhile, but in the newest designs (e.g., the Sprinter I4 engine) it no longer works that way. These new "smart" charging systems have elaborate algorithms that dynamically change the target voltage in order to optimize engine power and fuel economy. For example, they lower the voltage (and thus the current) during acceleration, and raise it during coasting. Many of them initially deliberately under-charge the battery so there is room to harvest otherwise wasted energy during coasts (kind of like dynamic braking in hybrids).

These new systems can be problematic when used with traditional RV charging setups. My 2014 Sprinter I4 was quite poor at coach battery charging, despite having a 200amp alternator. This is one reason why I decided to install a second engine alternator. My coach is now happily independent of the exotic chassis electrical system.
Thanks for the heads up on the latest (and maybe not so greatest) advances in alternator control. Unfortunately, these innovations you cite seem to be more directed at Cafe standards and assisting lower power engines in delivering higher hp and torque figures, all of which seems to be at the expense of maximal battery health. But that said, this probably only becomes an issue when additional batteries are added during a coach build and there is no question that your solution is going to be pro forma in the near future.

There is, however, an unintended consequence of independent alternators which is the elimination of a bi-directional separator that maintained both coach and engine batteries from shore power.
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Old 11-30-2016, 02:29 AM   #14
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There is, however, an unintended consequence of independent alternators which is the elimination of a bi-directional separator that maintained both coach and engine batteries from shore power.
Easy to fix with an add on Trik-L-Start or Amp-L-Start, especially easy on the Roadtrek Sprinter models with an AGM house battery under the hood.
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Old 11-30-2016, 02:48 AM   #15
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Easy to fix with an add on Trik-L-Start or Amp-L-Start, especially easy on the Roadtrek Sprinter models with an AGM house battery under the hood.
How do you do this with an Etrek?
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Old 11-30-2016, 03:29 AM   #16
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How do you do this with an Etrek?
Never seen it done on the older Etrek with the 8 AGM system but it should be easy to do if there is a battery equalizer in the system and if the two series connected 6 volt AGM batteries under the hood are grounded on the negative side. Connect the Trik-L-Start between the 12 volt battery bank under the hood and the chassis battery jump start post under the hood.
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Old 11-30-2016, 04:41 AM   #17
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Never seen it done on the older Etrek with the 8 AGM system but it should be easy to do if there is a battery equalizer in the system and if the two series connected 6 volt AGM batteries under the hood are grounded on the negative side. Connect the Trik-L-Start between the 12 volt battery bank under the hood and the chassis battery jump start post under the hood.
What can accurately be identified as an Etrek is sort of getting a little muddled. Our 2017 210 has 800 ah lithiums, underhood generator, and voltstart but since it still uses propane I guess technically it isn't an Etrek. The engine battery is 12 volts and underhood. There is a good sized 12V AGM battery behind a panel on the rear of the passenger side. Of the four lithiums, three are nestled together in the vicinity of what used to be the Onan generator spot and the fourth is all the way up forward on the drivers side next to a fresh water tank. Considering the relative length of this cable, I wonder how adequately the entire battery array is balanced. Practically speaking, there isn't any way to address the lithium battery terminals to install a Trik L Start.

FWIW, this coach (July 2016 build) has about 7000 miles on it and so far the electric/electronics have operated flawlessly, so as you surmise, they may
indeed be succeeding in working out the major hiccups.
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Old 11-30-2016, 04:58 AM   #18
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What can accurately be identified as an Etrek is sort of getting a little muddled. Our 2017 210 has 800 ah lithiums, underhood generator, and voltstart but since it still uses propane I guess technically it isn't an Etrek. The engine battery is 12 volts and underhood. There is a good sized 12V AGM battery behind a panel on the rear of the passenger side. Of the four lithiums, three are nestled together in the vicinity of what used to be the Onan generator spot and the fourth is all the way up forward on the drivers side next to a fresh water tank. Considering the relative length of this cable, I wonder how adequately the entire battery array is balanced. Practically speaking, there isn't any way to address the lithium battery terminals to install a Trik L Start.

FWIW, this coach (July 2016 build) has about 7000 miles on it and so far the electric/electronics have operated flawlessly, so as you surmise, they may
indeed be succeeding in working out the major hiccups.
The Trik-L-Start is connected between the AGM and the chassis battery to also allow chassis battery charging from solar with the Ecotreks offline in addition to using shore power with the Ecotreks online. While this is easy on an Ecotrek Sprinter with the AGM under the hood it is not so easy to do on other chassis where there is a distance between the AGM and the chassis battery.

Battery module balancing is not critical on the current Ecotrek vans that use 200 AH modules so the cable lengths are not likely a problem. Cell balancing is handled internal to the module by the BMS.
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Old 11-30-2016, 06:08 AM   #19
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Battery module balancing is not critical on the current Ecotrek vans that use 200 AH modules so the cable lengths are not likely a problem. Cell balancing is handled internal to the module by the BMS.
Why would multiple battery balancing for lithium batteries be less critical than it is on balancing charge rates to multiple AGM batteries?
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Old 11-30-2016, 01:52 PM   #20
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Why would multiple battery balancing for lithium batteries be less critical than it is on balancing charge rates to multiple AGM batteries?
Because the Ecotrek modules do not require regular full charges like AGM batteries do. If they don't get to full charge it is not going to effect the life of the battery cells. The critical factor in lithium battery packs is cell balancing and this is handled internal to each 4 cell Ecotrek module by the Battery Management System. If the charge voltage is high enough and long enough then all the Ecotrek modules will reach full charge even if there is unbalanced charge voltage at the modules due to varying cable lengths. If some modules are not at full charge when the charge voltage drops it is not critical, only effect is likely some, probably small, reduction in usable capacity for that charge.

The more critical issue is the type of charge profile used which seems to be set up to be the most optimum profile for the AGM battery life and not the 14+ volt optimum charge voltage for the lithium cells. Roadtrek does not discuss the charge profile strategy and you don't have a reading of actual charge level for the ecotreks so hard to actually assess how well the charge strategy actually performs.
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