Complete loss of coach power

I have a 2019 Unity CB on the new Sprinter Chassis. After using the RV for a long trip to AZ where everything was working fine I parked it by the side of the house for 2-weeks (with the main power switch by the door turned off) and when I went back to it yesterday the first sign something was wrong was that the retractable step did not extend when I opened it up. OK, that has happened before when I must have by accident left a light or something on and the coach batteries drained. Then I drove the RV around a bit to recharge the batteries and I got my power back. I tried that again this time but no luck. Everything is dead except the retractable jacks control panel, but that won't work and only lights up a low voltage light.

I have the 400w solar panels on the roof and that control panel is dead also. Not sure why they did not at least keep the batteries topped up while in storage.

I connected to external AC power through the 120v cable but with the exception of the microwave lighting up everything else is still dead.

I pulled the batteries out of the compartment and put a trickle charger on one of them but no luck so far.

Any clues or pointers? I am planning on going on a trip in a few days and need to get the DC electrical system back up. I am hoping this is something obvious. The manual is not very helpful. The circuit breakers all look OK for example. It is still under warranty but the dealer is booked out for months for service work.

Chris
 

lvuman

Member
Chris, I'm not sure about the CB model but in the Step Compartment in the MB model, there is a 200a Mega fuse located on the positive bus bar. You might check to see if it's blown.
 

SSTraveler

2014 LTV Unity Murphy Bed
Have you added any new electronics since you purchased your Leisure, if so what? That could be the culprit. Is your Chassis battery dead as well? I know on the 2020s the chassis battery trickle chargers being added to the Sterling DC-DC charger seems to cause issues and can completely drain both battery banks, house and chassis. If both batteries are dead then you have something that is connected across your two battery systems that have drained both batteries. There isn't anything that can do that outside some modification that was done after it was purchased. The chassis battery could have drained down, but not to zero, in just 2 weeks, although there are a lot of parasitic draws on the Mercedes side. But for the House side to drain off to zero with the battery switch off and 400w of solar should not have been an issue.

This thread has 2018 CB wiring diagrams, https://sprinter-source.com/forums/index.php?threads/92289/, that should essentially be the same for your 2019, you might want to use them to troubleshoot your situation.
 
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hoosierrun

Active member
The solar should have indeed kept your battery system charged, even if you had the main battery switch turned off. A common problem that I have read about that seems to match your problem has to do with an undersized fuse for the solar system. Check your battery compartment for an in-line fuse on a red wire. If you have that, lift the cover on the fuse holder and inspect for a blown fuse.

It sounds like the batteries have run down so far that the internal charger will not kick on. When that happens, running the engine sometimes works to bring the voltage up to a point where the internal charger will take over. At that point, you can shut the engine off.

Another option would be to just use an external charger on your house batteries to try to get them to re-charge.

Unfortunately, when batteries have been run flat like this, they experience some capacity loss which is permanent.
 

SSTraveler

2014 LTV Unity Murphy Bed
I don't know what your Solar fuses look like in your battery step box but this picture is from a 2020 UMB. The fuse covers Leisure uses makes it hard to tell it is a fuse. Some people also report the solar panel fuse behind the GoPower controller.
 

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msmolow

2019 Unity CB / 2018 Chas
Here's a picture from my 2019 Unity CB on a 2018 (older model) chassis. It's the small red fuse holder to the right of the large red multi fuse holder.

20190727_143952.jpg
 
Thanks all. The chassis battery is fine. I trickle charged the batteries overnight and the charger say they are fully charged. Still no power in the coach. I checked the fuse in the red wire holder and it looks fine. I have no idea what a Mega fuse is or how to tell it is blown or where to get a replacement. (Picture of compartment below which looks fine) If anyone has any other ideas I would be appreciative.

This vehicle is still under warranty but the RV dealer who I bought it from only gives me a "we are booked out for months" and won't even offer to have someone look at it for 5 minutes if I bring it up to at least give me a clue. Seems that an expert in these things could do that quickly from the questions they would ask. A bit disgusted with this dealer actually.

I am not new to RV's but have never had this problem before.
 

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msmolow

2019 Unity CB / 2018 Chas
I'm asking because I don't know, but your batteries are in series, shouldn't you be charging them as a group and not individually?
 

msmolow

2019 Unity CB / 2018 Chas
You can't tell if an AMG fuse blew by looking at it. You need to check with a multi-meter. If you remove it and the two ends wiggle it's blown, but sometimes they don't wiggle but the fuse still blew.
Have you checked your dc panel with a multi-meter? You should be able to bridge an empty dc fuse slot. If you're getting no voltage that points to the fuse, if you're getting low voltage that points to the batteries.
Are the levelers wired thru the dc panel or do they go direct with their own fuse? If the latter, then I would definitely check the AMG fuse to the panel.
 

Cheyenne

UK 2004 T1N 313CDi
I'm asking because I don't know, but your batteries are in series, shouldn't you be charging them as a group and not individually?
Totally agree!

You have two 6 Volt batteries in series so you either need to charge each one individually or them both as a pair.

You are currently only charging one of the pair so now need to move your charger onto the right hand battery and charge that one.

Keith.
 

msmolow

2019 Unity CB / 2018 Chas
Have you checked battery voltage at the terminals with a multi-meter? 12 volts across the group? I wouldn't trust the trickle charger indicator.
Also, looking at your charger, if your batteries are drained a trickle charger overnight isn't enough. You need to push more amps than the 4 max your charger provides.
If you are charging a single isolated battery it's 6 volt, if you're charging the group it's 12 volt, with what's shown in the picture (attached to a single battery which is still connected to the other battery) I have no idea.
I would suggest using a 30-40 amp charger. Better ones will also analyze your battery and will indicate if the battery is bad and unable to hold a charge.

 
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hoosierrun

Active member
So they are 2-6 volt batteries in series to get 12 volts. The charging setup as shown is not correct unless that is a 6 volt charger and you have charged both batteries individually.
 

Cheyenne

UK 2004 T1N 313CDi
And.... your charger is still set to 12 Volts so either battery or charger is likely to have been damaged!

Keith.
 

Cheyenne

UK 2004 T1N 313CDi
And it gets even worse!!!

You have the RED clip attached to the NEG terminal of the left hand battery!

Please disconnect the charger and BOTH batteries immediately and seek qualified help before reconnecting ANYTHING!

I THINK you may have charged your LH battery in reverse and Negative has become Positive and Vice Versa.

You will need to get this checked by someone who knows what they are doing with a volt meter.

Keith.
 

hoosierrun

Active member
And.... your charger is still set to 12 Volts so either battery or charger is likely to have been damaged!

Keith.
.... unless that charger has built in protection. Many do these days, including the El Cheapo Harbor freight unit. The protection could shut down any charging activity, assuming it really has it. I wonder if the water level in those wet cells have been checked.
 

autostaretx

Erratic Member
Look at your trickle charger ... what's its rated output?
2 amps is a fairly common number. (there's a reason they call it "trickle")
Now, what's your battery bank's ampere-hour rating? 200 AH?
Now we do the math: 200 amp-hours / 2 amps = 100 hours.
So it would take over 100 hours for a 2 amp trickle charger to bring up a fully-flat 200 AH battery bank.
You really want to invest in a more capable (higher output) shore-power charger as insurance.

This won't solve your root problem, but it might give you more tools to throw at it
(and a voltmeter is essential for probing into the various bits of the system).

For "where's the current going???" questions, a clamp-on DC ammeter is also very handy.
It grips around the wires without requiring disconnecting anything:
Clamp-clamping.jpg

Less than $50 (and also serves as a voltmeter and ohmmeter):

--dick
 

hoosierrun

Active member
Anybody else zoom in on picture #2? I believe that is the fuse for the solar panel. It appears to show a burn spot suggesting that it has blown. I can't tell 100% from the picture, but the bottom appears to be burned open. If so, that would explain the no charging from solar situation. I would suggest a mobile technician who knows electrical be called out for assistance.
 
Thanks for the feedback all - really appreciated. (It would have been useful if there was more information from LTV on properly charging batteries as not everyone has this knowledge - well I am learning) I did charge the batteries individually... anyway...

I took the RV to get some replacement batteries as the next step in the diagnosis, and as soon as I got on the freeway the charger started up under the passenger front seat. 35 minutes later the coach power is back. Perhaps the batteries were run down so far the internal charger would not kick in and the trickle charge overnight did the trick.

So far everything in the coach is still powered up, I am currently at 11.9 on the systems monitor and am thinking of changing the batteries or getting a spare set.
 

autostaretx

Erratic Member
11.9 volts is not a happy battery. Resting (i.e. all loads off, all chargers off) voltage should be 12.7 (if new) and you should start thinking about changing them out when it drops below 12.4 volts.

--dick
 

SSTraveler

2014 LTV Unity Murphy Bed
If you have Flooded Wet Cell batteries (FLA), they are gonners! If you are not in a quick need, like just storing for winter, then you have time to consider all the battery replacement options like AGM or Lithium battery. Many of us have been in your shoes and replaced the FLA batteries with AGM and then later with Lithium. Infact, a year and a half ago I replaced mine with Interstate AGM 210ah batteries and now I'm replacing those with a single Lithionics 315ah Lithium battery. Fortunately, I sold my practically brand new, in perfect condition AGM batteries to my neighbor. So take the time to decide what battery replacement is right for you. It might just save you time and money. These threads may help, https://sprinter-source.com/forums/index.php?threads/93361/ or https://sprinter-source.com/forums/index.php?threads/93929/.
 

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