Battery suggestions for a remote Prop with solar recharge?
koehler
Posts: 598
Project is still taking shape, so not quite sure of actual power needs.
Project is going to be:
Remote Prop running low speed (RC Fast)
1x small server being driven intermittently, maybe 2-3 times per hour for 10 sec
Small MP3 player/speaker (unless there is an OBEX component that can play MP3/WAV)
A Ping or other motion sensor
And of course some LED's.
I think the servo might require the most power as a 3030 seems to use 220ma. Although mp3 player plus speaker may exceed that.
I know I am going about this backwards trying to think of the best or cheapest battery I should/could use for this.
Am assuming a 4" round .5 - 1.0 A cell can run a boost circuit with enough power to charge some NiMH or Lipoly.
I can source decent NiMH (not Eneloops though) or some cell phone Lipoly.
Since I will have a small solar cell, I am thinking I can run the cell output almost directly to the NiMH since charging would be well below even C/10.
Prop won't have much to do, may be able to get away with 32Khz.
Any suggestions or ideas would be cool.
Comments
What voltage are you running the propeller and MP3 player at?
kwinn,
Everything is semi-theroretical ATM.
Cell is a single .5 v cell, considering using LTC3105 to boost now.
The MP3 player would be a nice to have, however most of the eBay boards are set to use 3.7v http://www.ebay.com/itm/GPD2846A-TF-Card-MP3-Decoder-Board-2W-Amplifier-Module-for-Arduino-/201480994126?hash=item2ee933fd4e:g:m~4AAOSw8-tWZm~5
Was planning on run the Prop low and slow with RCFAST, however I now see Parallax recommends not doing so if running servos.....
Prop diletante here for sure.
I will have to revisit the Limbo thread to get up to speed on Props low voltage capabilities.
In reality, I think what I am hoping to do could be done with a simple AVR or PIC with their nano/LV series.
But I have the Prop, and I really need to stop being a poseur.
Of course, NiMH doesn't have the same issue so can be as many cells as you like for the same charging circuit.
Imbalance can be a problem in NiMH and NiCd cells, although to a much smaller degree than it is in Li-Ion. In multi cell battery packs the contacts between cells can corrode and cause problems unless they are soldered or welded together.
Battery operated designs tend to be an iterative process for me. First I look at what is needed in the way of electronics, estimate the voltage, current, and total power draw of the system. At that point an initial battery selection can be made and then In may re-evaluate the electronic design.
As per User Name's earlier post the ambient temperature the system will be working in is also an important factor. A battery provides a lot more power at room temperature than it does at very low temperatures.
12 volt solar chargers/panels are also easy available.
Might be overkill, but in times where it rains, dark sky or in the winter solar panels output way less and batteries do usually not like it when it is cold. Having some 50+ AH can keep your system running over weeks of wintertime without problem.
All of them Lithium/NiMH and other small batteries are good for mobile applications like copter/cellphone/robot. But not needed at all for a stationary system. First of all they are quite expensive per AH compared to Lead Acid. Second they do not last as long, third they are more picky about charging.
And you will not need to worry about switching to RCSLOW and back to crystal when using serial communication links.
my 2 cents
Mike
I have to disagree on this a bit. A well maintained Lithium-Phosphate (As opposed to the common Lithium-Cobalts) will easily outlast any Lead-Acid ten times over. And only needing a single cell means the charging requirements are basic - use a lead-acid charger but disable the boost circuit. The voltage is obviously different but that's settable on any decent charger. Price on good deep-cycle lead-acids aren't that much cheaper per AH and it's recommended not to used the full depth anyway so they have to be de-rated.
Sorry for the late reply, pneumonia struck.
User Name, good guess. I am hoping to initially build a Power Flower first, with some additional Portal Sentry/home security features afterwards. Good question about temp as well. Just moved from CA back to NY, and the oddly warm weather this year had me overlook that.
JLocke- Thanks, I may go with one of those if the cheapo eBay ones are too power hungry or poor quality.
evanh and kwinn- I was thinking about the Li-Ion, however the lower recharge cycle count is making me look at that again. It would be nicer though to have only 1 battery.
Just checked and Eneloops are now supposed to work down to -40 (did I read that right???), and cycle count is multiples better. I'm thinking 4x1.2v Eneloops at ~2000mah should last for a day or two if sunlight is not abundant.
For cells, was hoping to use these http://www.goldmine-elec-products.com/prodinfo.asp?number=G17923
for cells.
I guess I jumped the gun a bit, thinking this thing through more.
For solar recharge with the cell inside the flower as I originally wanted, that would require the unit to track the sun, and/or be rather useless for its intended function. I could have it track during the day, and go 'active' at night, however that halves it usefulness/geek appeal. I think I may have to get some of those cells, some fresnel lenses and give concentrated solar a shot as a semi-remote unit. 2d tracker and maybe MPPT to.
Boy, this is getting involved..... cool.
msrobots- I hear you on the SLA's, however my experience with the ones that come with APC UPS's seems to show them as rarely lasting more than a year or two, and thats when they are 99.9% just in charging/bypass mode.... Even at $20 they are rather more expensive than a set of Eneloops from Costco.
I'm most likely going to go with bog standard NiMH to start, simply because I have them and can afford to see them die. However for the price/power I am looking at, at least initially, I am wondering if LiFePO4 might not be an alternative as they offer 2000+ cycles and enough power for this moderate project.
Only thing I think I might need to add is some sort of insulated box for the batteries, though this article seems to show that cold may not be quite as bad as it sounds: http://www.batterystuff.com/kb/articles/battery-articles/shorai-lfx-lithium-iron-phosphate-batteries-abuse-test.html.
I am wondering how much power I would actually save running RCFAST vs PLL x1?
I'm gonna guess those 12 volt Li-phosphate batteries, being intended for drop-in cranking purposes, will have internal bleed resistors for self balancing the cell voltages. Intriguing, I just read a user review that stated nine months of storage and still had good cranking! There is a risk of eventually going out of balance. I now suspect that's the most likely reason why they are only lasting 2x life of a lead-acid according to that website. They should be able to last much longer.
I presume you are able to purchase individual cells for your special application?
Yes, seems pretty cheap:
Tenergy 3.2V 1450mAh LiFePO4 18650 Rechargeable Battery
$2.99
http://www.onlybatterypacks.com/product/tenergy-3-2v-1450mah-lifepo4-18650-rechargeable-battery/