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| Thread ID: 70004 | 2006-06-19 04:40:00 | Using a PSU for other appliances | Feelers (10034) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 464378 | 2006-06-21 06:01:00 | No, they are 12 . 6 volts (2 . 1 volts per cell fully charged) after you let the float-voltage from charging dissipate . Cheers Billy 8-{) Billy . . . . If battery chargers put out 12 . 6, they'd take forever to impress a charge into a battery that when tested SHOULD be holding 13 . 2 to 13 . 6v . Even batteries that have been on the sales shelf are at 13 . 2+ after months of sitting there . If they aren't at about that value, we refuse to sell them to a customer . We are talking about lead-calcium "service-free" batteries here, not the good ol' lead-acid types . Open ended, a charger will probably climb right up to about 20v or so until a load is put into the unit . Alternators will actually destroy themselves if a battery isn't on the other end of the line . . . I've seen it happen in 1/2 a second on some cars . And Graham . . . you are right about auto alternators charging at about 14 . 8 . . actually that is at about room temperature . I see them get to 15 . 2 once in a while as the load increases . At any higher or lower temps the alt is controlled to keep the charge rate down to not overheat the battery . Very cold batteries explode when charged hard, and a hot battery will just drop plate material into the bottom of the battery case . Most new cars have ambient air temp sensors and also contact-type sensors to measure the battery temps too . Charging rates are so modeled to compensate . Modern alternators are digitally-regulated . . . they use an "on or off" pulse of varying length and amplitudes to charge a battery . Remember that newer cars have sophisticated computers that require good and regulated voltages to work with . One sidebar here: General Motors uses a 400hz "exciter" to activate the field in the alternator at low rpm's to compensate for lowered output at those times . One can hear it humming at idle if it's working . Other times, you can hear the fields cutting and also be sure that the alt is being excited . This is a portent to the newest 42v systems coming out soon . There will be no belts to drive water pumps, p/s pumps and other accessories including the a/c . There will also be no more camshafts or lifters or rockers either . Be sure to ask about that . Anyway . . stepping off my "brain surgery" soapbox again . . . sorry . |
SurferJoe46 (51) | ||
| 464379 | 2006-06-21 06:15:00 | Hi Feelers. No advice from here - just interested in what you plan to grow under that hood? | Scouse (83) | ||
| 464380 | 2006-06-21 07:00:00 | Billy....If battery chargers put out 12.6, they'd take forever to impress a charge into a battery that when tested SHOULD be holding 13.2 to 13.6v. Even batteries that have been on the sales shelf are at 13.2+ after months of sitting there. If they aren't at about that value, we refuse to sell them to a customer. We are talking about lead-calcium "service-free" batteries here, not the good ol' lead-acid types. Sorry SJ, but you are taking a very simple question to a completely alternative place. I didn't suggest that the charging voltage was 12.6, and I was referring to lead acid, not anything fancy like lead-calcium, which I assume is a fully sealed unit. A lead acid will drop to 2.1 volts per cell (12.6 volts for the battery) after the charger has been off for a while. Nice and simple. As for the question about 8A + 4A Feelers, that is possibly (bit of a maybe) OK if it is all from the one supply, but if using two supplies I would go for 8 + 8 to keep the impedances of the two sources reasonably well matched. Cheers Billy 8-{) |
Billy T (70) | ||
| 464381 | 2006-06-21 07:11:00 | OK | SurferJoe46 (51) | ||
| 464382 | 2006-06-21 08:58:00 | Hi Feelers . No advice from here - just interested in what you plan to grow under that hood? Haha I know what you're thinking . :D I'm taking plant biotechnology at uni, and have grand plans to grow Salvia Divinorum in tissue culture . My ultimate goal is to produce a Salvia plant that is "fitter happier and more productive" - but can also form seeds . As it is at the moment, Salvia can only be produced through growing cuttings, as there is an inhibition on the genetic/molecular level in producing viable seeds . Even when you intentially pollenate the flowers seed set is 4%, and of those seeds produced only 1/4 will actually grow . And of course - I know how to fix this problem(well I think I do) :D , and I'm applying for Government funding to do it too - my lecturer said he would approve my application, so that means I'll get $3000 of University epuipment/technican time . The funding is only for graduates though, I'm in my last year, so it will be soon . So in summation - its not for growing weed :lol: Anyways back to my situation - where can I get 2 old 8Amp power packs? how much should I be looking to pay, and is there a chance they will blow up haha? Having too much flow is not really a problem - I can use a venting system to block/ lower some flow . From what everyone else says what about two car battery chargers in parallel? |
Feelers (10034) | ||
| 464383 | 2006-06-21 12:36:00 | I picked up a 6 amp 230 volt to 13.8 volt switchmode supply at the Warehouse the other day, for $25. Designed for supplying "automotive cooler" fridges from the mains. It was built in the same case as the cheap battery chargers. Car battery chargers in parallel would be OK, they are reasonably "high impedance" and would balance fine. But 8 amp ones are rarer, the common cheap ones are 4 amp rated, but only 2.2 amps continuous. |
godfather (25) | ||
| 464384 | 2006-06-21 22:30:00 | Thank you Feelers for a very courteous reply to my rather nosey question. Very interesting - good luck with the funding and the research. | Scouse (83) | ||
| 464385 | 2006-06-23 03:54:00 | Apart from any opinions about the actual operating voltage of car electrical equipment, I have thought of a far more serious problem . I suspect the fan you have will have a brush motor . Brushes do have a limited life . If it's a secondhand unit, it may have used up quite a lot of its "time to fail" . I'd guess that your application requires the air flow for a considerable time, continuously . What will you do if it fails a few months into a research programme? Cheap is fine, but you will find that reliablility is priceless . In a practical research project, you've always got less time than you think . If you are growing something for weeks or months, you don't want to have to start again . One thing I learned long ago is that if a piece of equipment is essential you have to have two of them . Three is better . ;) I still think you'll be better off to go for a mains powered ( preferably new) fan or three . Have a look at the tangential flow fans in some heaters . They can move quite a lot of air, and they have induction motors, so no brushes . If you built two or three (or four) of them into the housing, simple switches will give you airflow control, and redundancy . Have a look at what the Warehouse has got, or the Council recycling shop . Speed control of DC motors with rheostats isn't straightforward, and if you are talking 100 odd watts, fairly expensive . Even a PWM electronic speed control might be a bit expensive, and (I've done it ;) ) not a Good Idea to plug in to a switchmode power supply . Even if you haven't got technician time officially yet, have a talk to the technicians in your department . They should be happy to talk about what you want to do, especially if they might have to work on it . ;) . |
Graham L (2) | ||
| 464386 | 2006-06-23 08:26:00 | This is just for my personal use, I can tissue culture in the flow hood - the chemicals required to do the actual lab work are highly restricted - they hve to account for every mL in the bottles! One of the chemicals used transports the important chemical through cell walls easily - which also makes it perfect for bioterrorism, thus the restriction . Otherwise I would do it myself, but if the government wil pay for it sweet! :D Actually you guys might be able to help - I am looking for a squirrel cage fan, that can blow between 300cfm and 500cfm . This is what I'm looking for, . grainger . com/Grainger/wwg/productIndex . shtml" target="_blank">www . grainger . com Can you get these things here? |
Feelers (10034) | ||
| 464387 | 2006-06-24 04:09:00 | Try people who do real airconditioning (not the Warehouse) . . . the sort with sheetmetal ducting . A chemical which helps transport through cell walls would make even more of a mockery of the "Correction" department's institutions . |
Graham L (2) | ||
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