Getting 36v from a 12v battery

wrote:

As Bill explained the mechanism Spaco. I am sure there is more than enough grunt available. Thanks for the comment though.
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You might want to locate a 24V motor/gearbox, which I think are fairly common. The 24V motor will run a little faster at 12V, than the 36V motor will. If the motor were 12V, it would probably simplify the application.
Another option might be to gut/modify the existing motor case, and use the existing armature shaft as a driven arbor, driven by a belt and a 12V motor. The existing motor's shaft will likely have gear teeth machined into the end, so it would need to be utilized as an input shaft for the other drive motor.
WB metalworking projects http://www.kwagmire.com/metal_proj.html ...........

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On Wed, 28 Mar 2007 15:24:46 -0500, "Wild Bill"
Thanks Bill, but too much work.
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snipped-for-privacy@msn.net wrote in news:rl6l035d899l94q9idvl8gcsaq7oii834v@ 4ax.com:

3 deep cycle batteries and the charger(s). If the gate is used often, I would go with 3 chargers, if not, one and switching to charge all 3 batteries in parallel as Lloyd suggested.
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Anthony

You can't 'idiot proof' anything....every time you try, they just make
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wrote:
Hi Anthony,

That's what I am thinking at the moment. The gate is rarely used more than twice a day.
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snipped-for-privacy@msn.net wrote: ...

You should be able to get a 120v 200w inverter + a 120 - 36v transformer + a bridge for $50. You may have to use a couple of transformers in series to get 36v cheaply (e.g., 24 + 12, or 3 x 12). Probably cheaper than 2 more batteries & chargers.
Bob
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On Wed, 28 Mar 2007 17:11:05 GMT, snipped-for-privacy@msn.net wrote:

It just might. 150 watts for 2 minutes four times a day is 1200 watt-minutes or 20 watt-hours per day. Three 5-watt solar chargers (15W total) working on average 2 hours a day (including cloudy and rainy days) more than covers that.

It'd be simpler and cheaper to use three small DC-to-DC (12 to 12) isolated converters as chargers. One or 2 amps (12 to 24 watts) each should be way plenty. A single converter with 3 isolated secondaries would also work. The lowest battery would hog most current -- which would probably be what you want. The converter would only operate when there was solar power available to run it.
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On Wed, 28 Mar 2007 21:56:26 -0500, Don Foreman
Hi Don,

Are you saying to connect their outputs in series to drive the actuator? If that works, might be the best plan.
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On Thu, 29 Mar 2007 16:06:37 GMT, snipped-for-privacy@msn.net wrote:

I'm saying connect 3 batteries in series to drive the actuator, and have three small DC-to-DC converters in series to charge the batteries. The batteries always handle the payload.
This seems to fit because you have only very intermittent load with long periods of recovery time.
These converters could all be powered by your 12-volt solar source. The advantage here is that the converters need only handle charging current, which is a whole lot less than max load current, so they could be quite small and inexpensive. They would only run when solar power is available to run them, while the battery power would always be there to operate the gate.
It could even be a single converter with three isolated outputs if such a thing can be found surplus or whatever. Otherwise, it wouldn't be hard to build one since you seem to be comfortable working with elex.
If you have enough sunshine year-round the 5-watt solar chargers may well be the simplest solution.
Please feel free to email me if you'd like to pursue the other course. I'm retired and enjoy projects like this.
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On Thu, 29 Mar 2007 12:22:38 -0500, Don Foreman
Hi Don,

OK, got it, but isn't that pretty close to what I was suggesting to start with? Have the batteries in series and three solar panels to charge each of the three batteries. I might even be able to use 3 of those 1.5W chargers HF often has for around ten-bucks a piece. I wouldn't need any dc-dc converter would I?
At max load the actuator is rated at 140W, so on a windy day and at max load that may take 2 minutes to close but opening would happen quite smartish and virtually no load with prevailing wind assitance.
The no-load I measured at 36v and 0.7Amps, around 25W for 1 minute (the designed open/close times) which is what it would be with no wind or wind assisted. <grin>
Unless I am thinking wrong here, that is 140 / 60 * 2 = 4.6W/hr and 0.5W/hr. Approximately 5W/hr. and easily done with the 3 x 1.5 solar.

We have around 320+ days of sunshine AND we don't do Daylight Saving so that's gotta help too, right??? LOL

Thanks for the offer, but I prefer the forum so everyone can look in and see what's what. Before I ask for suggestions on a project, I always do a google-group search. If we do emails it doesn't get included.
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On Thu, 29 Mar 2007 23:41:31 GMT, snipped-for-privacy@msn.net wrote:

With three small solar panels, it is exactly what you suggested to start with. You would not need any DC-DC converters.
It could also be done with a DC-DC converter with 3 isolated outputs, running from your existing 12-volt solar source. However, your initial suggestion of using 3 small panels would be considerably simpler and I see no reason why that wouldn't work very nicely.
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On Thu, 29 Mar 2007 21:57:42 -0400, clare at snyder.on.ca wrote:
Hi Clare,

Yeah, but 3 x $15.00 panels from HF is a lot chepaer than buying a charge controller and no wiring issues as it comes with a diode installed.
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On Fri, 30 Mar 2007 14:38:55 GMT, snipped-for-privacy@msn.net wrote:

Plus, the little solar panels are intrinsically current limited to a safe trickle-charge level. Further, while batteries can be used in series to drive a load it is best to charge them individually. Batteries are commonly used in series for 24-volt and 36-volt electric trolling motors. Good chargers for these have separate isolated outputs to charge the batteries individually without disconnecting them or overcharging any of them. The difference between a "good" charger and a "not so good" charger is at least a couple of years of battery life. My last set lasted more than 5 years.
The charge current from 5-watt solar panels presents no significant risk of overcharging at about 350 mA or so.
A little inverter with separate outputs and charge controls running from the larger solar power source would be better if higher charge current (faster charge) was necessary, but that does not appear to be the case here.
Said little inverter would probably cost less than $45 for parts, but it would only make sense here if one wanted to build a little inverter for the helluvit. It'd cost me zip because my goodiebox would supply the parts, but I'd spend a day doing it -- and enjoy the activity and maybe learn a thing or two.
Go with the little panels, Jenny. There's a lot to be said for simple. If that doesn't work then we'll devise something that does, but I'd bet it'll work just fine with 340 days of sunshine per year.
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On Fri, 30 Mar 2007 12:25:14 -0500, Don Foreman

Say again? A battery is a string of series connected cells. A 12 volt battery is sic 2 volt cells in series. You don't charge THEM separately. As long as the discharge in series, you charge them in series. If anything causes one to be discharged at a different rate than the rest, or they are of different capacities, individual charging is adviseable. However, when discharging in series, so all cells see the same amount of current, charging with separate chargers, particularly un regulated chargers that may not be evenly matched in output (read "solar cells") you could easily end up with one battery less charged than the rest, and then discharging them could damage the lower charged cells by reversing them. The rule of thumb is charge batteries in series, and dischrge them in series. If you need greater current capacity, buy bigger cells instead of parallel connecting smaller cells. That's why it is better to use two GC2H golf cart batteries in series than two 12 volt batteries of the same physical size (rougly group 22) in parallel.

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On Fri, 30 Mar 2007 20:43:01 -0400, clare at snyder.on.ca wrote:

Only because it would be impractical to do so. The cells in a particular battery are about as identical as they can be because they're manufactured at the same time in the same way from the same lot of materials -- and even then they are sufficiently different that usually one cell fails before the others do. Different batteries with different ages, capacities, brand or even just with different history will accept charge differently. Therefore, to charge the lowest one fully in series you must overcharge the others. Overcharging is the worst thing you can do to a battery.

Other way round. For identical discharge amp-hours (by definition in series), the batteries may need slightly different charge amp-hours to recharge fully but not overly. The little solar panels won't overcharge because their current drops as battery voltage rises with charge, and even their max output current is a safe trickle or maintenance charge level.

Don't know what assumptions that assertion is based on, but it is not how it's done in at least one practical case: trolling motor batteries.
Check the setup in any pro's bassboat (Ranger, Triton, etc) with a 24-volt or 36-volt trolling motor. They use the best gear (including chargers) available (albeit sometimes limited to what's available from their sponsors) because they make their living in their boats and they need their stuff to work reliably all day every day upwards of 200 days a year on the water including competition days. Their chargers charge each battery individually. Accessories (sonars, GPS, power trim, livewell pumps, running lights, etc) are run off the engine's battery; the TM batteries only power the TM.

Yes.
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On Fri, 30 Mar 2007 21:49:13 -0500, Don Foreman

Next to "unequally yoking" them. Batteries, whether series or parallel connected, SHOULD be as identical as possible. Mix and match doesn't cut it.

And series charging satisfies that requirement as the resistance of the cells changes with state of charge. AN "equalizing charge" brings them all back to full .

The exception, rather than the rule. In Electric Vehicle applications, they are series charged with a charger of the proper voltage. The Bass Boat guys use the 12 volt chargers for the very reason you stated - because they are available from their sponsors. The low performance consumer trolling motors are 12 volt - so that's what the sponsors supply, stock, advertise and sell. There is no good engineering reason to use separate chargers. (at least from all the reading and research I've done in regards to electric vehicle applications and large Uninteruptible Power Supply applications. Even Telco battery sets are series charged at the bank voltage, not individually. ANd those things go for decades.

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On Fri, 30 Mar 2007 23:09:19 -0400, clare at snyder.on.ca wrote:

Both MinnKota and Motorguide offer 24-volt and 36-volt trolling motors, and that's what is found on high-performance tournament fishing boats. These motors are about as high-performance and efficient as DCPM motors get. They're electronically-commutated switchmode-controlled multipole motors with substantial rare-earth magnets. They'll pull a boat thru salad that is almost too thick to pole thru. They compete on performance first, then price.
MinnKota also offers excellent dual- and triple-bank multi-stage microcomputer-controlled chargers. Unlike some of the "consumer grade" chargers ala Wal-Mart, they work very well. They are often integrated into the boat. It would be cheaper and simpler to make a single 24-volt or 36-volt charger with a single charge control -- but that isn't what they do and this isn't because they don't know what they're doing.
Individual controlled charging is the more general case. If the batteries are truely identical such that series charging would work well, then the charging processes (series vs individual) would be indistinguishable. The current vs time in each battery and the total voltage of the stack would be the same either way. So series charging can't be "better", it's just cheaper and adequate under the best of conditions.
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On Fri, 30 Mar 2007 14:38:55 GMT, snipped-for-privacy@msn.net wrote:

You didn't rerad the rest of the post - the charge controller only needs to cost about $10 if you buy all the parts new. A good scavenger could likely do it for $2.(or free)
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On Fri, 30 Mar 2007 20:35:57 -0400, clare at snyder.on.ca wrote:
Hi Clare,

That is beyond my electronic capabilities to design much. I am comfortable at building kits, fault finding etc and I have designed some simple DC motor controls at times using Gottlieb's books. I did a search for charge controllers and came up pretty much empty in the 12v to 36v range..
Would you care to provide a schematic that will work? Maybe a website or two where I can get started?
I don't want to get between you and Don on the argument of series v parallel, charge/discharge, way out of my depth. But I do like the idea of a single 36v controller instead of the 3 HF units. I was planning on the HF units as the most simple solution I could handle. But a 10-buck 12-36 charger sounds good and I do already have the 5W panel.
Thanks
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