need more info on making a BTS from earlier info

elesaver · February 2016

In an earlier discussion, instructions were given for making a BTS that is immersed within the electrolyte to get more accurate temps. The forklift battery I am using does not have space to install a BTS in the "normal" way. So, here's where I am. I have the 3/8" glass tubes, the sensor, and the battery cap. I understand that I need to drill a 3/8" hole in the cap to accommodate the tube without altering the vent of the cap, so I feel confident I can do that. Here's where I'm unclear...the tube needs to be inserted into the cap with the right depth to be into the electrolyte without hitting the plates and then the top of the tube needs to be sealed with silicone. BUT, if the sensor is in the tube surrounded by air, is it really going to give accurate readings? So, is the sensor just suspended in the tube or does it need to touch the glass sides of the tube or do I need to put some kind of conductive material into the tube to surround the sensor? Clarity is a beautiful thing and I need some.

Thanks for the help.

vtmaps · February 2016

The the air in the tube will slow down the responsiveness, but it won't be a problem because changes in battery temperature occur very slowly... the temp probe will be able to keep up with the changes.

--vtMaps

Anawa · February 2016

elesaver, what sensor did you decide to use?

Paul
in Georgia

elesaver · February 2016

vtMaps, thanks for the info about air and temperature. That helps a lot.

Paul, I have two choices: I bought a thermistor from mouser electronics as mentioned by someone in another thread. Then if I can attach those leads to a phone wire and place the sensor into the tube, it'll be good. Then I can plug the other end into the charge controller so that the info is relayed. I am going to try this first.

As a backup and probably the better choice is to "dismantle" the Midnite Solar BTS and place its sensor into the tube. The other end, of course, would go to the cc. I hate to tear up the Midnite Solar BTS if I don't have to simply because it costs a bit. Plus, there's always that fun in "doing it yourself." Somehow that has always been my bent. We'll see.

Vic · February 2016

Hi elesaver,

Posted the following in the Building a RTS Battery Cap Thread, but just for you and your Classic you probably will want to confirm that your Thermistor has the 3988K Curve:

An Update on the NTC Thermistor Part Number at Mouser:

Just ran a Resistance vs displayed temperature for a Classic CC BTS. The following part number appears to be a very good Curve Fit:

http://www.mouser.com/ProductDetail/EPCOS-TDK/B57871S103F1/?qs=sGAEpiMZZMuBd0%2bwiCVS294ahU8xLN7tvHCHNluAMOI=

This part has a ' 3988K ' curve and is still 10 K ohms at 25 C.

Have not run the curve for the Outback RTS, BUT, it might well need a different curve 10 K NTC Thermistor.

Good Luck, Vic

vtmaps · February 2016

Vic said:

Have not run the curve for the Outback RTS, BUT, it might well need a different curve 10 K NTC Thermistor.

The Outback and Midnite temp sensors are interchangeable (according to boB).

--vtMaps

Vic · February 2016

Hi vtmaps,

Yes, recall seeing that said by boB, but, just trying to be a bit cautious, AND, after looking at the difference between one Classic BTS verses one OB MX-60 RTS, on the same battery at the same time, was not so certain.

Certainly, both the OB AND MN Sensors appear to be 10 K NTC Thermistors.

Just did not have the time to run the OB RTS last night, and would hate to suggest that someone buy an incorrect Thermistor for the application.

As an aside, it is more than a bit surprising that after asking twice on the OB Forum that OB Tech chose to NOT reply, to questions for the RTS Table, and weather there were any differences between any of the OB RTSes. These ALL must be Trade SECRETS!!

Thanks again for that RTS Table. There is a strong suggestion that this is also the Table for the MX-60 RTS, at the very least. YES, it would seem to be an obvious assumption that there would only be ONE RTS for one company's products, but was just trying to be a bit careful about assumptions.

More Later, Thanks, Vic

vtmaps · February 2016

Vic said
As an aside, it is more than a bit surprising that after asking twice on the OB Forum that OB Tech chose to NOT reply, to questions for the RTS Table, and weather there were any differences between any of the OB RTSes. These ALL must be Trade SECRETS!!

I don't remember where I got the table... maybe here.

--vtMaps

Vic · February 2016

vtmaps said:

Vic said
As an aside, it is more than a bit surprising that after asking twice on the OB Forum that OB Tech chose to NOT reply, to questions for the RTS Table, and weather there were any differences between any of the OB RTSes. These ALL must be Trade SECRETS!!

I don't remember where I got the table... maybe here.

--vtMaps

Hi vtmaps,

Well, I am very happy that you did grab that file, while it WAS there, but while that file does have size, it displays as a null file on my .pdf reader.

The other links that I found were also broken/non-functional, but this file may require a different reader.

Just ran an OB MX-60 resistance vs Count value, using the Table that you provided earlier. The resolution of the MX's A/D limits the MX to a nominal one-ish degree C resolution. But, it appears that the OB RTS, as supplied 11 years ago with the MX-60 is fairly close to the Curve of the 10 K NTC, Linked above.

The Classics, with their tenth-degree C temperature resolution make curve checking much easier.

So - Thank You again! Vic

BB. · February 2016

Is this the right file? (attached PDF):

And, here is the Outback Forum count to temperature conversion info:

http://www.outbackpower.com/forum/viewtopic.php?p=14411#14411

-Bill

elesaver · February 2016

Thanks for all of this info. These things are far "above my pay grade," so to speak. But, the seat of my pants has permanent wings since I continue to fly with those wings quite frequently. I'll try to read and understand. I guess what you're trying to tell me is that this thermistor will work, even though that fact was unbeknownst to me.

The goal, of course, is to get some good temperature information about the electrolyte. We'll see what happens.

Vic · February 2016

BB. said:

Is this the right file? (attached PDF):

And, here is the Outback Forum count to temperature conversion info:

http://www.outbackpower.com/forum/viewtopic.php?p=14411#14411

-Bill

Hi Bill,

YES! That IS the File that vtmaps sent, and reposted. Thanks!

And, elesaver, I believe that you now have a 10 K NTC Thermistor. If so, was asking that you confirm the spec for that device.

If the Thermistor IS from Mouser, and is a 10 K Ohm NTC TDK Epcos 60 milliwatt device, then wanted you to try to confirm that the spec on the device matched the curve 3988K. There should be the exact part number on your Invoice. If the part number on the invoice matches the part number for the link in this Thread, then you should have a device that matches the MidNite sensor very well.

This should be the exact Mouser P/N for the 'correct' device, if you bought the noted device from Mouser:
871-B57871S103F1

That was all ... Thank you,

Vic

Dave Angelini · February 2016

elesaver said:

Thanks for all of this info. These things are far "above my pay grade," so to speak. But, the seat of my pants has permanent wings since I continue to fly with those wings quite frequently. I'll try to read and understand. I guess what you're trying to tell me is that this thermistor will work, even though that fact was unbeknownst to me. The goal, of course, is to get some good temperature information about the electrolyte. We'll see what happens.

I would think your goal is to make sure the corrected voltage is accurate at various temperatures. I tried to attach a file from Xantrex that pretty much covers the voltages one should see. Shooting the terminal with a decent electronic temp gage is also a way to check this.

elesaver · February 2016

Vic said:

BB. said:

Is this the right file? (attached PDF):

And, here is the Outback Forum count to temperature conversion info:

http://www.outbackpower.com/forum/viewtopic.php?p=14411#14411

-Bill

Hi Bill,
YES! That IS the File that vtmaps sent, and reposted.   Thanks!
And, elesaver, I believe that you now have a 10 K NTC Thermistor. If so, was asking that you confirm the spec for that device.
If the Thermistor IS from Mouser,   and is a 10 K Ohm NTC TDK Epcos 60 milliwatt device, then wanted you to try to confirm that the spec on the device matched the curve 3988K.   There should be the exact part number on your Invoice.   If the part number on the invoice matches the part number for the link in this Thread, then you should have a device that matches the MidNite sensor very well.
This should be the exact Mouser P/N for the 'correct' device, if you bought the noted device from Mouser:
871-B57871S103F1
That was all ...   Thank you,
Vic

Yes, Vic. That is the thermistor that I purchased. Dave, the document link posted will not open for me. Let's face ALL the facts, though I hate to, once again, face my inadequate knowledge base, I do not have an understanding of "matching the curve." Be aware, gentlemen (whom I hold in such high regard for the knowledge that you have), there are those on this forum (like me) who are continuing to grow and learn as we enjoy this venture that we call "solar." We are willing to explore into areas where most may shirk. Your help is so very valuable to us. I am not certain that you could go back to the days where you were just beginning to put two and two together to realize where some of us currently stand with what we know...or in my case, what I don't know.

It's all such a wonderful experience and to think that I can run parts of my household on the power from the sun! It's just a delight. Thank you for all your help! It is deeply appreciated. You make learning is truly a pleasure.

Vic · February 2016

Hi elesaver,

Since the Thermistor that you purchased is the one that matches, well, the one used in the Classic and OB BTS/RTSes, you should not need to worry about the exact details of the curve. The Thermistor manufacturer has done that for you!

The Chart that Dave posted is simply the Temperature Compensation values for different temperatures with different battery voltages.

The Classic will show you the voltage settings that you have, AND, the Compensated voltages for the battery Temperature, which the Classic will also display ... so the Classic tells you all you need to know, without the table.

At some point, it would be good for you to compare the temperature reading of your BTS (in the Classic's Temp menu), with a temperature reading of the electrolyte. This electrolyte temperature could be read, with a glass thermometer, if you have one available.

So, Good Luck with the project. And, please let us know how things are going. Vic

need more info on making a BTS from earlier info

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