ZIG CF8 Never giving green LED for Leisure Battery

[longwori]

Hi everyone,

This is my first post having just bought my Bongo on Saturday. i have done a search but I could not find this issue.

As I have just bought this I am trying to understand the wiring. It has a Zig CF8 panel in it and a leisure battery that I believe is new. I have measured the voltage at the leisure battery and if my multi-meter can be trusted it says that it is 15V with the engine idle and 17.5V with the engine running. Is this correct? I was expecting 12V and maybe 14.5?? (it is also showing as the same voltages on the main battery too).

However my main question is, why even after a long (200 mile journey) does the LED stay on Red on the Zig panel. I have not managed to get the LED to show as green. Any idea where the fault may lie? I thought it would maybe only go red when the voltage dropped below say 10V or something.

Thanks for any advice,

Ian

[wormey]

That sounds high to me, I'd have thought a max running of 14.8. volts. I thought the leisure battery on its own and charged should read 12.5 volts. info from mmm.

[longwori]

Im going to get batteries for my digital multi meter and try and measure it again. I still dont know why the green LED doesnt come on though. I would have thought if the voltage exceeds n.nn volts then it would show green. When it drops it shows red so why am I only getting red?

Strange. I would appreciate anyones comments or if they have experienced anything like this.

[g8dhe]

If you really are seeing a charging voltage of 17.5 volts then your batteries will be expiring VERY shortly!
When you have new batteries in the DMM, start by measuring the voltage without the engine running at all, preferably without the engine having been run within the last hour or two. You should expect somewhere between 11 volts and 12.8 volts. Then start the engine, you should see the voltage rise to no greater than 14.5 volts (the battery will have started to create gas at about 14.4 volts).
Do you have a manual for the CF8 ? The Green LED should light once the voltage is over 11 volts on the leisure battery, however that will depend if you have any loads switched on and how long the cable run from the L/B is, even quite small loads will bring the voltage down quite rapidly when measured at the the Zig unit itself, make sure that all the connectors and fuse connections from the L/B are clean and well made.

[longwori]

Hi,

OK, I now have batteries in my digital multimeter and have measured the voltage more accurately. I have 12.75V at the leisure battery and 12.7 at the terminals 3 & 4 where it connects to the Zig. When I turn the Zig on to its 12V setting I get the red LED and the voltage at the Zig drops just a touch to 12.65V. As you say, the manual says I should get a greeen light for anything over 11V so i'm confused!

It would be a useful feature to have if I can get it working. At the moment I only have the water pump connected to the Zig but i'm intending to add the lights, blinds, stereo etc.

I will give Zig a call too and see if they have any ideas.

Cheers,

Ian

[tallbongo]

If the diagram in this topic here is correct, it seems the battery condition is indicated by a comparator (IC1). It could be that some other component has blown giving too high a reference voltage to it, or the comparator itself is faulty. Either of these should be reasonably cheap to fix if you can DIY it (although if it is a surface mount component that needs replaced it will be difficult to solder).

Have you opened the Zig unit up? If you can identify IC1 you should be able to find signals to it of 11V and whatever the voltage of your leisure battery is currently.

One other thing to check is that the ground of the Zig is shorted to the ground of the leisure battery. If it isn't there is no common reference and voltages cannot be compared by the unit. Of the two electrical faults that my Bongo came with, both were due to poor ground connections (fuel tank gauge and leisure battery not charging).

[longwori]

Thanks for that link as it may well be useful in the future. In a past life I did electronics and am quite happy to wield a soldering iron and as I have only owned the Bongo for a week now, I havent yet opened the Zig up. However, I called Zig themselves today and got to speak to a techie guy there who reckons the problem is a 2 minute one to sort out and is just the adjustment of the potentiometer that sits on the same PCB as the LED's to correctly switch the LED's at the desired voltage.

So, he said I need an 11V input to the LB terminals and then tune the potentiometer to be at the point of flick over between the LED's. I guess I can use this potentiometer to set the low voltage indicator to be anything I like in the range that it offers. As I dont have an 11V feed, I may need to run the LB down a bit and use that as my input.

The nice man at Zig saidd if I want he will sort it for me while I wait but unfortunately I have not plans to be headed in their direction.

It sounds like an easy self fix anyway, it will just be the removal of the unit which will be a bit of a pain. I will report back when I have tried this out incase it benefits others in the future.

Cheers,

Ian

[tallbongo]

That potentiometer sounds like it's adjusting the reference voltage to the comparator.

11V sounds low to me. A fully charged battery should be around 12.8V and according to this link 12V is empty. If the link is correct I think I'd want my warning around 12.2V. With your electrical knowledge you could easily rig up a suitable reference supply to your desired voltage with a couple of very high value resistors (to minimise current draw) as a voltage divider (e.g. 50k and 1M will give 12.2V from a 12.8V supply yet draw only microamps).

However, before starting it'd be worth turning the potentiometer to both extremes to ensure that you can get a green light. As you have a LB at >12V you should definitely be able to get this.

[longwori]

It didnt help anyway. I tried adjusting it from extreme to extreme and the green led never came on. Never mind, it would have been nice if it worked but I guess I will know the leisure battery is getting low when the lights start to dim! Or, I could get a separate battery monitor from ebay.

[tallbongo]

My previous post neglected voltage drop across the cables, so 11V may be more suitable. It depends on the current flowing (as g8dhe pointed out).

However, you should have been able to get a green light by adjusting the trim with a charged LB connected, so something is either connected incorrectly or the Zig is faulty. It could still be a relatively simple problem so I wouldn't give up yet. Some other things to check:

1) Are all the ground connections at the same voltage?
2) Now you know that the potentiometer is to be adjusted to calibrate the switchover, can you measure the voltages at its terminals with it adjusted to each extreme?

A circuit diagram (or photo of the circuit) would be very useful in diagnosing the fault.

[longwori]

Hmmm...... it may just be possible to measure the voltages at its terminals but it isnt easy to work on. Maybe I will take another look tonight. The difficulty is that the tiny PCB (about 1.5 inch square) is soldered to the end of the LED's that are stuck in the facia of the panel and you access the internals of the Zig by removing this facia. The components face the back of the facia so they are only an inch away but luckily there is a small hole drilled in the back of this tiny PCB to allow a screwdriver to be inserted and adjust the potentiometer from the back of the circuit board. This may all sound ok but the internal wiring only allows the front of the zig to be moved a few inches from the back giving very little room to work in and I blew two fuses by my metal precision screwdriver touching live points inside the case while trying to manouvre it into position to insert in the tiny hole.

After replacing the fuses and checking there was no lasting damage, I wrapped the screwdriver in cling film to insulate it and tried again but couldnt get a greeen LED. It will be hard to test the voltage and adjust the potentiometer but I will have a look and see if it is feasable. It would be nice if it works as I dont really want to fit an extra gadget to do the same job.

Thanks for your continued interest!

Ian

[longwori]

Hi,

OK I have taken some measurements and pictures (click for full size). I was not exactly sure what I was doing but feel free to tell me where I went wrong!





My understanding of a potentiometer is that it has three terminals. Lets call them A, B and C. In the pictures that I hope will attach, B is earthed to the chassis so I measured from a 12V +ve source in the Zig to point A as the negative with the potentiometer at each extreme. (At least that is what I think I did but I faffed around for ages trying to get readings).

Note that the Leisure Battery voltage at its terminals under the bonnet is 12.58V and the Main Battery is 12.44V.

Well I dont know if it is a conincidence but at one extreme I got 12.58V and the other I got 12.44V if I did it right. I also think I got 12.44V between C and the positive source on the Zig no matter what I had the potentiometer set to.

Do my readings make sense? Does this help!!?

[g8dhe]

Can you take a close up (use Macro if your camera has it) of both sides of the board ? The critical thing is to read the values / colours of each component.
If so I'd be happy to sit down and try to work out the circuit, and see if we can try and work out the problem as a I have a few days spare at the moment!

[Rhinoman]

That looks pretty knackered to me, I can see two copper tracks that are broken, C doesn't look like its connected to anything anymore. You need to link across those tracks but before powering it all up again you need to find out what melted them, although maybe you did that with the screwdriver. Can you give us a picture of the top of the board so we can see what comparator is being used?

[g8dhe]

Actually I might be able to see what the problem is look closely at the track below;

That looks to me like the track has burnt out and evaporated, in which case, it will need to be replaced with a wire and possibly might need to think how or what caused a large current to flow thru it ?