Confused by Solar.

[Wobs53]

Hallo All
New member here and as title says I'm a bit baffled by some electrickery stuff and hope that somebody who knows more about this stuff than me can help.

I've got an MB LWB sprinter built by SC Sporthomes. Had it for years and love it to bits. It's equipped with a CBE PC200/DS300 for the 12 and 240 v electrics. I've also wired in a NASA BM2 battery monitor connected direct to the parallel wired battery bank of 3 x 120AH flooded batteries via a shunt on the -ve lead on the end battery. So it records every bit of power being used either through the CBE system or wired direct (ie inverter and compressor fridge) A few years ago I stuck a 100W solar panel on the roof with a PWM dual battery solar controller also wired direct to the leisure batteries. All have worked well. Leave solar on permanently to keep the van and leisure batteries topped up and alternator charges up both when on the road. Rarely need an EHU.

Decided to do away with satellite telly so dumped the dish on the roof which gave me room to add another 100w solar panel. Then I needed to upgrade the solar controller so went with an Epever duoracer 20A MPPT controller. All wired with 6mm cable, din mounted knock out switch on +ve and -ve and fused. Again connected direct to batteries.

Worked well at first but then noticed a couple of quirks. The battery monitor is permanently live which is what it's designed to do on boats. When the battery bank got to fully charged the monitor would occasionally show a discharge up to about 1.5amps for about 10 seconds or so. This was with absolutely no load on the batteries and PC200 off. Never done that before. Then occasionally it would show batteries charging at a higher rate than the controller was showing. Not by much, maybe up to 0.5 amp, but I'd become used to the Nasa monitor showing same charge rate as the old PWM controller. Just quirks or something to worry about?

But worse than that now the alternator on the van won't charge the leisure batteries when motor running. I've disconnected the solar panels and controller from the batteries but still no charge. Alternator still charges the van battery and EHU will still charge the leisure batteries. The double battery symbol and alternator symbol do not come on on the PC200 when motor running.

Putting these together I wonder if the DS300 has just taken it upon itself to throw a tantrum.

Any advice would be really appreciated.

 

[autorouter]

The method for charging the leisure batteries from the alternator is much like that in most MHs, except the newer ones. When the engine is running and the alternator is pushing out power, a relay (ie an electrically operated switch) will automatically connect the leisure battery to the starter battery. Since the alternator is charging the starter battery, the leisure battery gets charged by the alternator as well.

When the engine stops, the relay disconnects the leisure battery from the starter battery, so no danger of accidentally flattening the starter battery if the leisure battery is discharged too much. That relay is called the 'split charge relay', and is built into the CBE box.

Since your alternator is working, it looks like there's a problem with the split charge relay, or the wires to/from the batteries. There are two thick wires from each battery to the DS300 box. On each of those wires, near the battery, there will be a fuse, probably 30A to 50A. That's the first thing to check.

Also is there a fuse labelled with the double battery symbol, maybe a 3A one. Worth checking that too. This is for the 'engine running' signal that switches the split charge relay on and off. This signal is sent out by the alternator when it is running.

 

[Figaro]

 

[Wobs53]

The method for charging the leisure batteries from the alternator is much like that in most MHs, except the newer ones. When the engine is running and the alternator is pushing out power, a relay (ie an electrically operated switch) will automatically connect the leisure battery to the starter battery. Since the alternator is charging the starter battery, the leisure battery gets charged by the alternator as well.

When the engine stops, the relay disconnects the leisure battery from the starter battery, so no danger of accidentally flattening the starter battery if the leisure battery is discharged too much. That relay is called the 'split charge relay', and is built into the CBE box.

Since your alternator is working, it looks like there's a problem with the split charge relay, or the wires to/from the batteries. There are two thick wires from each battery to the DS300 box. On each of those wires, near the battery, there will be a fuse, probably 30A to 50A. That's the first thing to check.

Thanks for that. Checked the wires and fuse to and from the battery and nearly came to same conclusion. I just needed reassurance. I'm guessing that the split charge relay is the black box on the DS300 board which looks as though it's soldered so probably means getting a new DS300. Can't complain though as the conversion was done in 2005 so it's a 17 year old Italian relay.

 

[autorouter]

I'm guessing that the split charge relay is the black box on the DS300 board which looks as though it's soldered so probably means getting a new DS300. Can't complain though as the conversion was done in 2005 so it's a 17 year old Italian relay

That's always a possibility, but I find these relays are very reliable and the other bits like connectors and fuses are much less so. Do you have a multimeter, are you OK with taking voltage measurements? A few readings will soon narrow it down.

Also Apuljack Electronics will repair the DS300 if it's faulty, or sell you a new one if you prefer.

^{_{Subscribers  do not see these advertisements}}

 

[Verteuil Man]

Hola.

 

[Wobs53]

Also is there a fuse labelled with the double battery symbol, maybe a 3A one. Worth checking that too. This is for the 'engine running' signal that switches the split charge relay on and off. This signal is sent out by the alternator when it is running.

Checked that and even changed the fuse but no change.

That's always a possibility, but I find these relays are very reliable and the other bits like connectors and fuses are much less so. Do you have a multimeter, are you OK with taking voltage measurements? A few readings will soon narrow it down.

Also Apuljack Electronics will repair the DS300 if it's faulty, or sell you a new one if you prefer.

Having spent a very frustrating few hours yesterday taking the van apart and tracing what seemed like miles of wire and changing a helluva lot of fuses, I bit the bullet and ordered a new DS300 from Rainbow who I'd used before. Should be arriving tomorrow. I saw Apuljack when I was looking for one but never having been to them before went to Rainbow. These 2 suppliers were both same price; £80. Others were up to £170 or so. Just hope that this works. Good to know there's someone like Apuljack around that understands these things.

 

[autorouter]

If you've got the cover off that DS300, you could check 3 things. First, the starter battery voltage is reaching the big battery input terminal. Also the leisure battery voltage is reaching the other big battery terminal.

Then check that the 'engine running' signal, about +12V, is reaching the terminal of the fuse labelled with the double battery symbol, when the engine is running. Finally check that fuse with a meter, not just a visual check. If all OK then it's probably the DS300.

 

[Jo662]

 

[Wobs53]

If you've got the cover off that DS300, you could check 3 things. First, the starter battery voltage is reaching the big battery input terminal. Also the leisure battery voltage is reaching the other big battery terminal.

Then check that the 'engine running' signal, about +12V, is reaching the terminal of the fuse labelled with the double battery symbol, when the engine is running. Finally check that fuse with a meter, not just a visual check. If all OK then it's probably the DS300.

Thanks for reply. Voltage reaching big battery terminals B1 and B2 but no power at the fuse terminals labelled with double battery. So now I'm a bit lost. Any advice or suggestions would be welcomed.

Having read instructions that come with the DS300 box, it appears the black box is a relay. This does not click when engine started so either power not getting to it or relay is broken. I'm guessing that signal for the relay comes thru the fuse marked with 2 batteries and that has no power. But I may be wrong. So I'm still nowhere really.

^{_{Subscribers  do not see these advertisements}}

 

[autorouter]

Just to be clear, you say there's no power at either of the fuse terminals.There should only be power there if the engine is running, it will go off when the engine stops. To be more exact, when the ignition key is turned, the dash lights come on, but no power to that fuse yet. When the engine starts, the alternator light on the dash goes off, that is when the power should be seen at the fuse. It's called the 'D+' signal.

If you've tried that and get nothing, you could try a wire (with an inline fuse the same as the 'double battery' fuse, 5A?) touching between the starter battery terminal (B1 or B2, not sure which) and one of the terminals of the fuse. If you get the right one, the relay should click. That would tell you if the relay is OK or not.

While doing that test, you could measure the volts difference between the B1 and B2 terminals. with the relay open, it will be the difference between the two battery voltages, a fraction of a volt. When the relay closes, the voltage should drop close to zero. That would tell you that the relay is actually connecting the batteries, not just clicking to no effect.

 

[Wobs53]

Hi AR,
Yup, no power at either terminal when engine running. The difficulty is I'm not sure where these fused terminals (double battery) pick up power from. There's power at the big terminals (B1 and B2) so I figured there had to be an external source that was supplying power when the engine started that would trip the relay. B1 and B2 are obviously constant 12v. As luck would have it I traced back a likely suspect from pin 19A (small white one just above B1) and found a blown fuse where it was connected to the van fuse box under driver's seat. Replaced the fuse and started the engine but it blew straight away. So, should be straightforward but the guys that built the van had 2 wires going to this pin 19A so I need to now trace the second wire back and see if that's the source of the short causing fuse to blow. It still might be the relay as it's only a 3A fuse but I think now more likely to be no supply to 19A. And that's as far as I've got so far.

The power supply they picked up from is apparently heater boost according to Mercedes and I believe supplies power to a relay that diverts water to a secondary rad. I can't remember ever using it .
Great idea about using a fused wire to see if relay working. I'll also try the voltage drop test and report back.

 

[autorouter]

The actual D+ signal is very low power, so they usually have a method to boost it a bit. They get it to trigger a relay. Then connect the relay power contacts to the 12V supply, via a suitable fuse. If the fuse blows then things triggered from that relay output stop working, but the original D+ still works. So as you said, you need to find out what's blowing the fuse.

 

[GeoffnDee]

Wobs53 If you do not have the wiring diagram for your DS300 it is available in a manual that can be downloaded from Resources and is on page two of Manuals for Motorhome stuff .. It does show a Electronic battery sensor (volt sensing relay ? )that is linked to the ignition and a D+ simulated signal and I wonder if the problem could be in this area.

 

[Wobs53]

Thanks Geoff, very helpful. Makes me think I might just be on the right track. Probably more by luck than judgement but time will tell.

^{_{Subscribers  do not see these advertisements}}

 

[Wobs53]

Problem solved. After much wire tracing and false trails it finally came down to something as simple as a fault in the van wiring where the signal was picked up. I changed to another terminal 15 feed in the van's wiring (live when ignition on) and alternator happily started charging leisure batteries as soon as engine started.

Confusion in this case was caused by the original builders of the van tapping into the wire feeding this terminal on the DS300 board and using this to trip the relay to a 3 way fridge so 12v could be supplied to this fridge when the engine running. I had removed the 3 way fridge a few years ago and replaced it with a compressor fridge which I wired direct to the leisure batteries. But I left the wiring in for the old 3 way fridge in case I ever needed it in the future. This wiring ran from one side of the van to the other behind all the insulation and through the roof so I figured I might need it at some point. But I was too lazy at the time to trace it back to the board and batteries. I simply connected the wires at the fridge end to a junction box and left them for future use. Lesson learned.
I've now also disconnected and labelled these redundant cables at the DS300 and batteries.

 

[autorouter]

This wiring ran from one side of the van to the other behind all the insulation and through the roof

Great to hear it's sorted. What kind of insulation is the wiring running through? Polystyrene foam makes PVC cables go brittle after a few years. That's PVC as in PolyVinyl Chloride not Panel Van Conversion. One solution is to cut a channel, and line it with rockwool.