Optical SG monitors now available

[BruceM]

I just got an email from jsaphotonics.com.  They are offering their fiber optic specific gravity sensors, electrolyte level sensors, and cell temperature sensors in small quantities for experimenters.  The SG or SOC battery cap sensor is about $40. $30 as an oem style unit. Plenty of options, reasonably priced.  It seems like a few of these would be handy for someone with a diy system.  There's nothing more reliable than SG for wet lead batteries.

[Tom Reed]

That's an interesting product! There's an $8k battery bank in the basement that is nearing the 1/2 way point in it's life and I'd like to extend it as long as possible. They don't seem to have pricing on the site, where can more info be found?

[BruceM]

Tom, I've misplaced their emails with pricing-  send them an email and I'm sure they'll send you the pdf files with all the info, photos, and pricing. 

[BruceM]

 Here's the price list from the pdf file they sent me:

OEM SOC BATTERY SENSOR, w/  2.0" or 4.0" Probe ...................................$ 39.50 w/ on board temperature sensor  SOC SENSOR w/ BATTERY CAP HOUSING w/ 2.0" or 4.0" Probe Installed in standard bayonet mounting cap w/ 3'cable, on-board temperature sensor and regulator...............$ 49.50  OEM LIQUID LEVEL SENSOR, w/ 2.0" or 4.0" Probe .....................................$ 29.50  LIQUID LEVEL SENSOR w/ BATTERY CAP HOUSING w/ 2.0" or 4.0" Probe Installed in standard bayonet mounting cap w/ 3'cable, on-board temperature sensor..................$ 35.95  OPTIONAL FEATURES  w/RJ 45 Ethernet jack connector (battery cap version only) ..............................add   $15.00   w/on-board regulator for 6-37 VDC battery operation...  ...... .............................add   $10.00  w/immersion temperature sensor.......................................... ....................add   $ 30.00 . Cable and connector for OEM version...............................................................$12.00  Custom probe length (less than 10 units)...  .................................................... add 15.00  International Shipping Surcharge (less than 10 units)............................................add 10.00 . *Production prototype units. Prices and configurations subject to change without notice. E-mail us for quantity quotes. Taxes may apply. International duties and customs are responsibility of the buyer. Nominal S&H on all orders applies. Prepaid or Paypal orders only. Minimum orders may apply.

[Tom Reed]

Humm, so it's a SOC or level/temp but not both. That makes it a bit less attractive. Thanks for the info!

[Mad_Labs]

Very cool. Too expensive for me to use one per cell. Whadaya think, would one cell per battery give a good enough reading? I would think so.

JOnathan

[BruceM]

Yes, they suggest one per battery.  If you are careful about watching cell balance and regular equalizing I think you could get away with even less.  I was thinking of averaging just 3 for my series string of 10 12v batteries, and then watch for deviation via my controller software, and flag for either equalizing or re-calibration if they drift apart too much.

You'd have to compare to a physical reading with hygrometer yearly on those particular cells to adjust for LED/photodetector aging as well as drift of whatever analog circuitry you use.

Still, a heck of a nice tool for giving you true, utterly reliable SOC.  

Madlabs, I just sent the pdf files  to you to the email address you have listed on the forum.  Nice color pictures of the units, some notes on applications, etc. 

[Mad_Labs]

I had already contacted them and they got back to me quite quickly. But many thanks for sending me the info!

These units are so tempting to play with that I might have to get some. One way around using the level sensors is when the electrolyte gets low the SG will suddenly change, so by looking for that you could have at least an "oh sh$t" level detector. One small bummer is the SG readings are not temp compensated, even though there is a temp sensor. No big deal to code for that but still seems like they should have that done on the sensor level. But to do a decent job on my bank I'm looking at $290 just in sensros at least.

The other thing I wonder is about is calibration. The recommend 3 point. I guess get three solution of acid, alkaline and distilled water.

Jonathan

[BruceM]

The calibration is a pain, I agree.  I might get one to experiment with.  I was thinking of using an older battery which I could discharge deeply and mess with temperature for the calibration.

I'm still on the fence over these for myself, not for the cost but the amount of time I'd have to spend to incorporate them into my existing setup.  I have Peukert compensated amps in and out based software computed SOC already.  And plenty of other projects in the que.

[Mad_Labs]

Yeah, I don't really need the SOC either, but I do still want to play with the sensor, just cuz it's cool. I am considering getting a couple of the level sensors and make a stand alone system that blinks when getting low. My batteries tend to stay pretty even electrolyte-wise, so a couple should do it.

Now that I think about it, a couple of SOC sensors for the golf cart would be nice....

Jonathan