Getting 36v from a 12v battery

On Sun, 01 Apr 2007 15:17:52 GMT, snipped-for-privacy@msn.net wrote:


There are dozens of inexpensive single-voltage models, but 36v isn't popular. Some medium-priced controllers like the Tristar are multi-voltage, but I see now that it's limited to 12, 24, and 48. The Outback MX60 (MPPT and $500) can do five voltages including 36. Compared to that, this 36V-only model might seem like a bargain at perhaps $100 http://www.solardepot.com/pdf/2007/SCI_ASC.pdf . These are all multi-stage chargers though, and their features would be wasted using the small supply you seem to have in mind.

Perhaps there's something on this page http://www.redrok.com/electron.htm , but it's a bit hard to tell. ;-)
You could wire 3 of the small HF $10 (on sale) 12V panels in series. Their output is so little that you could do without a controller.

12V garden tractor batteries were $10 each (plus an old core) at Walmart last I looked. Or, under $40 delivered for 3 of these http://www.batterywholesale.com/battery-store/proddetail.html?prodID68 .
Wayne
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wrote:

That's the ones she wants. With a simple overvoltage clamp (zener and resister) for a controller, just to keep the battery from complaining about high voltage - as a precaution. You may be right - might not need it, but simple and relatively cheap.
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snipped-for-privacy@msn.net wrote:

Around here we have Daylight Saving time more than 6 month of the year, so they should call that Regular Time and in the winter call it Daylight Losing Time ;)
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On Wed, 28 Mar 2007 17:11:05 GMT, snipped-for-privacy@msn.net wrote:

Since you seem to be enjoying the education value of the project :-) wire the batteries in series, and charge them with a proper controller (as little as $35) from PV or a power supply. Solar panels and controllers here http://beyondoilsolar.com/charge_controllers.htm and here http://www.solar-electric.com/charge_controls/solar_charge_controllers.htm . It's more than you need, but HF often has a 45W solar setup on sale for $200 http://search.harborfreight.com/cpisearch/web/search.do?keyword=solar+panel&Submit=Go. Can you say gate lights? :-) This controller http://www.discountpv.com/chargecontrollers/TS45 is overkill for your application, but I have a barely-used one for $75 if you're interested.
Wayne
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wrote:
Hi Wayne,

Yup, you got that right. I have seen the HF 45W units but for a little more than $200 I can get a mule opener all ready to bolt on. I have the bit between my teeth for a unique approach now that I have all these suggestions. Call me a masochist, but this IS getting interesting.
I thank Don for his boat lift philosophy "$20 in parts, $5K if anyone paid for my time."
Thanks for the generous offer on the charge controller but will pursue some more Golberg'ish approaches first.
--

Kind regards,
Jenny and her tribe of survivors.
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On Thu, 29 Mar 2007 16:14:46 +0000, Jenny3kids wrote:

I have seen some pretty simple voltage doubler circuits. Search Google and I'd bet you can find plenty.
I seem to recall a small IC used as a multi-vibrator to pulse the 12 VDC to make it able to drive a small transformer driving a diode bridge. For low wattage, it would be dirt cheap.
Ron Thompson On the Beautiful Florida Space Coast, right beside the Kennedy Space Center, USA
http://www.plansandprojects.com My hobby pages are here: http://www.plansandprojects.com/My%20Machines/
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On Fri, 30 Mar 2007 07:48:22 -0400, Ron Thompson
Hi Ron,

Yup, I gve that a psssing thought very early on, but current is the issue. On a really windy day, a gust may even stall the actuator for 20 seconds at a time with who knows what Amp-rise. I am sure the actuator can take it and I know the batteries will, but not so sure about simple elecrtonics.
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On Fri, 30 Mar 2007 14:42:39 GMT, snipped-for-privacy@msn.net wrote:

The electronics don't have to pull the load, the batteries will do that. Your alternator wouldn't start your car even if it were spinning, right? The battery does the short bursts of heavy lifting.
Elex (or small solar panels) supply small steady current to replenish batteries that supply heavy current very intermittently.
Low power boost circuits typically use a flyback topology, but I'd go with a foward converter here so peak supply current would be about the same as steady-state current. LM3524,5 or 6 running at 100 KHz, coupla $2 MOSFET's, a ferrite xfmr with 3 secondaries that'd easily fit in a shirt pocket, etc.
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On Fri, 30 Mar 2007 07:48:22 -0400, Ron Thompson

And not terribly efficient. With solar power, you want efficiency.

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On Fri, 30 Mar 2007 20:44:00 -0400, clare at snyder.on.ca wrote:

90% efficiency is not unusual even in a small switchmode converter. If diode rectification (rather than synch rect) is used then efficiency will be a bit lower, but Schottky diodes are inexpensive, readily available and commonly used.
Why do you want efficiency in a solar battery charger if it can get the job done? Sunshine is free.
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On Fri, 30 Mar 2007 21:56:33 -0500, Don Foreman

Primarily, up here, because the sun doesn't shine all the time, and the power output of the cells is not terribly high. If it's cloudy and rainy for a few days, you still need to get in and out through the gate. Also, big panels are not free!! Little panels means little power as stated above.
Worked on a solar electric home and office setup in West Africa. You didn't waste any more power than absolutely necessary during the rainy season!!
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On Fri, 30 Mar 2007 23:17:48 -0400, clare at snyder.on.ca wrote:

Jenny has 340 days of sunshine per year. The "right solution" may well be different in the Yukon or a rainforest. Her batteries will probably open and close her gate quite a few times between sunny days if necessary at about 0.133 ampere-hours per operation. "Little power" is all she needs on average.
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On Sat, 31 Mar 2007 11:55:36 -0500, Don Foreman
Hi Don and Clare,

I think that's the crux of it. I do have an abundance of sunny days and even those days that are not full sun, we still get a few hours. The opener will probably be only used twice a day. Once out and once in. Probably for less than 75% days of the year as I don't go out every day. Trickle with some waste would be fine.
OK, guys, anyone want to toss a schematic on their website? <grin> I wont be doing the battery side until later this week. I will test it with a spare car battery at 12v, albeit slow, then the 3 batteries and charging side will come later.
Hate to say it, but the chances of the batteries being closely matched to each other is slim. LOL Using what I got.
Thanks guys.
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I would think it is fairly simple. Charge the batteries in parallel, and then use your controller, to place them in series to run your actuator. Just needs a 4 pole double throw relay, and a diode in line with your charger, if it doesn't already have one. . snipped-for-privacy@msn.net wrote:

jk
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It might be considerate to try that with your own batteries before advising someone else to do it with theirs. <G>
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OTOH, "I" don't need the 36 V.
jk
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On Sun, 01 Apr 2007 15:28:41 GMT, snipped-for-privacy@msn.net wrote:

It could be useful to know a bit about how your 5W panel behaves. If you have a VOM (multimeter), get readings of open-circuit (no load) voltage and short circuit current in typical sunshine. For short circuit current, just set your VOM on DC amps, connect it to the solar panel and read the meter. You won't blow anything with a 5 watt panel.
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On Sun, 01 Apr 2007 15:28:41 GMT, snipped-for-privacy@msn.net wrote:

Used or surplus UPS batteries, 12 volt 8 amp hour are cheap and readily available. New they are only about $19 each in the USA. (30ish here in Canada - wouldn't you know) 20 amp hour are also readily available on the surplus market - AGM too, no watering to worry about.

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On Sun, 01 Apr 2007 15:28:41 GMT, snipped-for-privacy@msn.net wrote:

Awright, have a look at http://users.goldengate.net/~dforeman/solar_charge /
I did a SPICE simulation (circuit simulation program) of this circuit useing guessed-at parameters for your solar cell. It works as expected. If one solar cell doesn't have quite enough moxie to keep yer battery charged you could always add another one in parallel later -- parallel because the LMC555 doesn't want to see more than 18 volts and there is no reason at all not to parallel solar panels.
Efficiency of this circuit could easily exceed 90% if it's set up right.
The inductor could be a little wedding-ring sized toroid of about 330 uH. AxMan Surplus had a bunch of 'em on hand last I looked and I have half a dozen of 'em here. They'll handle a couple of amps without saturating. The power MOSFET is a garden-variety part. If I were to mail you an inductor I'd also mail you a MOSFET -- I have hundreds of them in my goodiebox. You can get everything else at Radio Shack and skip the minimums and shipping from guys like Digi-Key, Mouser and Jameco. The diode to the battery should be a fast diode like 1N4933 to 1N4936. I have a bunch of 1N4936 (1 amp 600 volts, fast) on hand too, more than I'll ever use.
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On Sun, 01 Apr 2007 15:13:36 -0500, Don Foreman
Hi Don,

I am not questioning the electronics knowledge of either of you as the discussion between you and Clare is now beyond my understanding.
I appreciate the effort you have gone to here, but if Clare is correct in that I can series the 3 HF panels and put them straight across the 3 batteries, why are we messing with a charge controller? I wasn't sure you could series them, but I guess all the little sub-panels within the big panel are series though.
Thanks for taking the time to do this.
Get them Taxes done man. I wimped out and got an extension, but have promised the Accountant I will have stuff done by May first. That date is now looking pretty shaky though. LOL
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