Moving Battery Temp. Sensor to new battery.

[dRdoS7]

Hi,

The BTS IS a Thermistor.  It has a nominal resistance of 10 K Ohms at 25 C

Jaycar have: Thermistor NTC 5MMDIA 10KR for $1.75.

I'll buy one, use an old POTS cable, and try that. May take a knife to the MNBTS if I can't get to town today, which is unlikely as my wife wants me to put down laminate flooring in the bathroom. I was hoping it would rain, so I couldn't set up the power saw outside!

i have got an unused temp sensor and i am based in australia. ready to send it to you if you want it.

Thanks for the offer. I'll see how I go making one.

Thanks all,

dRdoS7

[Vic]

Hi drd..,

Making one's own BTS is a  bit of an Engineering project.

Choosing among the various curves for seemingly identical 10 K NTC Thermistors IS  important.

Having a functioning BTS to use as the reference,  and exposing this reference and the candidate Thermistor to the same temperature environment (and allowing some "soak time"),  should make the task easier.

Even if the candidate Thermistor has an identical curve,  there is still the Tolerance specification,    that one needs to consider.

Does the source for the 10 K NTC Thermistor that you are considering,  have a specification available?  If there is a link to that spec available,  I would love to look at it.

After spending some time looking at the details of Thermistors and BTSes that use them,   IMO,  you would probably be ahead by accepting australsolarier's generous offer to send one to you ...   but that's just me.

FWIW,   Good Luck,   Vic

[dRdoS7]

Hi,

You could try to diagnose it as follows:  do a continuity test across the  sensor leads it should not have continuity. If it does have continuity trace down and locate the short. Then,  measure resistance and it should have around 20-50 ohms, probably closer to 20 as it's summertime in AUS.

I found a "slight" problem with your instructions, if you look at the picture (thanks Vic), which I saw after I had done as you suggested, you'll notice there are actually 2 shorts already.

http://forum.solar-electric.com/discussion/comment/354561#Comment_354561

All that aside, I made up a BTS, it was 11 @ 22C.  The measurement dropped when I held it with my fingers. Didn't register with the Classic. I disassembled the Classic's BTS, soldered it to the now shortened cable and connector, tested same as the one I made, but still no indication on the Classic. I tested that there was power coming to the themistor, there was.

australsolarier has sent me his spare BTS (thanks AS), I'll be interested to if it works.

Thanks,

dRdoS7

[Vic]

dRd..,  Thanks for the reply.

I did participate in several of those wind-sun discussions on the BTS/RTSes.

And,  do know that some of these seemingly identical BTSes use paralleled outside conductors,   at some point someone in either OB or MN Engineering mentioned that only the outside conductors on the 4-pin telephone were used.

The resistance of a single conductor of that cable is probably negligible,  compared to the range of resistance of the Thermistor.   Using two paralleled conductors could add reliability to the connection point of the BTS to the device that uses it.

Just for simplicity,  mentioned using just the two outside conductors on the phone plug.   Either approach should be generally reliable.

FWIW,   Vic

[dRdoS7]

dRd..,  Thanks for the reply.

I did participate in several of those wind-sun discussions on the BTS/RTSes.

And,  do know that some of these seemingly identical BTSes use paralleled outside conductors,   at some point someone in either OB or MN Engineering mentioned that only the outside conductors on the 4-pin telephone were used.

The resistance of a single conductor of that cable is probably negligible,  compared to the range of resistance of the Thermistor.   Using two paralleled conductors could add reliability to the connection point of the BTS to the device that uses it.

Just for simplicity,  mentioned using just the two outside conductors on the phone plug.   Either approach should be generally reliable.

FWIW,   Vic

The point of the first part of my reply was that with instructions, and that there is "conductivity continuity" inherent in the design, that would cause some-one to cut up a possibly not faulty BTS. The first 2 conductors I tested had conductivity continuity, so I (wrongly) assumed there was a fault. There was no mention by laszlo of using "outside", or any particular pins for testing. By the time of your post, I'd already cut up my cable.

When I get a chance, I'm going to test the voltage & current to the BTS, just need to find some more 4 wire POTS cable with suitable connectors, and a phone plug/socket combo I can attach a DMM to measure both. I was planning on making an externally accessible socket anyway to save taking the Classic cover off and on again.

Thanks,

dRdoS7

UPDATE: I checked the voltage, without a BTS it's 3.3v, with a BTS it's 1.7v.

[laszlo]

Hey Drd,

I did not take a BTS apart before,  but my approach was to eliminate the wire having a  short first. Then, checking resistance of the thermistor.

  With the photo that you attached, it is showing two wires going to each terminal on the thermistor. You are correct, these joined wires would show a short.   

Do let us know how you come out with the replacement BTS, as well as the build.

[dRdoS7]

Hi,

I did not take a BTS apart before,  but my approach was to eliminate the wire having a  short first. Then, checking resistance of the thermistor.

  With the photo that you attached, it is showing two wires going to each terminal on the thermistor. You are correct, these joined wires would show a short.   

Do let us know how you come out with the replacement BTS, as well as the build.

Teach me to not act on advice so quickly.

Maybe a lesson to not offer advice, unless you know exactly what the situation is.

Anyway, no batteries were harmed during the making of this epic. The original BTS has survived, just needs some tidying up of the wires: maybe a blob of silicone.

On to the BTS:

BTS arrived yesterday.

This morning, I plugged it in, and not showing up!

I tested it, and it read the same (15. as my orig. (disassembled & re-assembled) BTS.

I did a lot of head scratching.

After a while, looking through the Classic settings, and I don't know how/why, I saw the Temp. Comp. setting was "Disabled". I changed that to "-0.5", and the sensor shows up!

Maybe I had set it to "Disabled" when I was swapping over to the NiFe from AGM, changing charge settings, etc., and forgot.

I didn't even realise that "Disabled" also turned off the BTS: it still gets voltage. I would have thought it only turned off the compensation.

Very embarrassing!!

As a bit of info, the BTS I made, when plugged in, was about 4C higher than the 2 Classic BTSs.

Thanks,

dRdoS7

EDIT: I turned on logging of BTS in LA, and it actually displayed a temperature on yesterday's graph, even though it was "Sensor not installed" in LA.

EDIT #2: I forgot to mention in the Classic, under "Temps" it displayed "N/A 25C" when it was "Disabled": A trap for the unwary/unaware.

[TomW]

Teach me to not act on advice so quickly.

Maybe a lesson to not offer advice, unless you know exactly what the situation is.

Exactly my concern(s) with online advice.

You never know the recipient's skill or knowledge level.

Many small "gotchas" exist in this field that the experienced person just knows to look out for.

Who is at fault when something goes awry? The advisor who was trying to help in good faith?

The advised who blindly followed the advice?

A bit of both, I think.


Many years ago I saw advice on how to fix a windows install on a laptop on an IRC channel. The advisor said type in "deltree C:\".  The questioner blipped off of IRC a few seconds later, just as another user posted "DO NOT DO IT. Most of us knew it was a joke. The advised did not. It was a Debian Linux support forum so the question was inappropriate and the advisor was probably being an arse in that case. Everyone with experience knew it was not a fix in the usual sense of the word and would wipe out the install.

A few days later the advised got on the IRC channel and posted a very angry diatribe about having wiped out his install and having to re install and demanded the person who posted it be banned from the IRC channel and the entire internet. Yeah, right!. The advice led to a fix but not what the person wanted.

Just an example of how online advice can be misunderstood and not what you want.

Not taking any sides here but always look before you leap, especially on irreversible actions.

Tom