Schaudt lr1218 solar data signal, or Votronic ebl signal

[SandraL]

There are 2 wires that convey a signal representing current generated by solar panel to the ebl and then onto the dt screen for display. One for leisure battery, other for starter battery.
Can anyone tell me what this signal is?

Votronic have a compatible system, although only one wire for leisure battery.

Perhaps a 0-5 v dc signal representing 0-25 amps?? Thats a wild guess!!

 

[Phill D]

judging simply by the size of the 2 wires its no where near 25 amps. i replaced my LR1218 with a votronic mppt and used the existing wires to the LT320. but it only shows current to the hab battery it is not capable of showing the Cab battery which is as you probably know a 1 amp trickle maximum from the votronic.

 

[Lenny HB]

Not sure what signal they send to the EBL but the reason the Votronic only has one wire is that they don't bother with the negative as it's already connected via the battery connections.

 

[SandraL]

Is there a chance either of you, and anyone else please, could measure the data wires with a voltmeter to ground. For any volt reading please add the amps displayed at that time if known, else sunny or dull conditions.
I am trying to establish if there is a relationship between volts on the data wire and amps displayed on the dt panel.
Ideally in sunshine but a no output reading would be helpful as well.
Have searched the web but not found any info on this.
Maybe with a series of readings it may be possible to establish how this works.
I did ask about this on the schaudt stand at dusseldorf a few years back but they were unable to give me an answer.
Thanks.

 

[Lenny HB]

Sorry can't help, I have Votronic controller but don't use that feature.
Normally I would try and help but my controller is not easy to get at. If I get time I'll try and get a meter on it tomorrow.

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[autorouter]

I did ask about this on the schaudt stand at dusseldorf a few years back but they were unable to give me an answer.

Sorry can't help on this, I don't have solar. Have you tried emailing Udo Lang at Schaudt Customer Services? They will reply to English-language questions.

 

[stevec]

Sorry can't help on this, I don't have solar. Have you tried emailing Udo Lang at Schaudt Customer Services? They will reply to English-language questions.

I tried that when I fitted my Schaudt solar controller. They wouldn't give details of data format as it is proprietary. It is digital not analog. If you had a storage oscilloscope and lots of time it would be possible to reverse engineer it, but life's too short!

 

[Lenny HB]

I tried that when I fitted my Schaudt solar controller. They wouldn't give details of data format as it is proprietary. It is digital not analog. If you had a storage oscilloscope and lots of time it would be possible to reverse engineer it, but life's too short!

Not much point in me having a look then as my scope died and there has been no sun anyway.

 

[SandraL]

Asked votronic what the ebl output signal was, their reply was


thank you for your inquiry and your interest in our product range.

The EBL terminal output is a current source, which supplies a current of 1mA per 20A charging current.

If you have any further question, don’t hesitate to contact me.

 

[autorouter]

The EBL terminal output is a current source, which supplies a current of 1mA per 20A charging current.

That's great, it's very useful information - not quite enough, but a very good start. The idea is, you put a 'sense resistor' into the circuit, similar to a shunt resistor but a larger resistance value. Then measure the voltage across it. Knowing the resistance and the voltage, the current source output amps can be calculated, and so the charging current can then be calculated.

You'd need to know the maximum voltage that the current source can put out (usually called the compliance voltage). That's the further information that is required. However I'd imagine it's about 5V, to pluck a figure out of the air. Here's one way to do the calculation:

Suppose the maximum current to be measured is 30A (max output of the solar controller).
The current source maximum will be 1mA x 30 / 20 = 1.5mA
Let's say the maximum compliance voltage is 5V.
Ideally we'd like a nice simple conversion factor, like 30A = 3V, so 10A = 1V etc.
This means the maximum likely voltage (3V) will be less than the compliance voltage (5V).
Since R = V / I, a suitable resistor will be 3V / 1.5mA = 2000 ohms.
So if you put the current source through a precision 2K resistor, the voltage across the resistor will be 0.1V per amp of charging current.
Measure the voltage across the resistor, and divide by 0.1V to get the current in amps. (In other words multiply by 10).

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