Posted: 2/20/2015 8:16:05 AM EDT
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http://www.ebay.com/itm/141351712551
not affiliated, just linking from a reddit post. 
discuss |
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Quoted:
http://www.ebay.com/itm/141351712551 not affiliated, just linking from a reddit post. http://thumbs1.ebaystatic.com/d/l190/m/mH-F2cAqRACb303WFUa1NRA.jpg discuss this product is simply a 12vdc automotive relay. it's not a novel solution by any means, but comes pre-assembled nicely with connectors etc. note that a PWRgate also charges the battery when the power supply is powered. the relay approach does not do this, and a separate charger is needed. just from a financial standpoint, (a Battery Tender Jr + the linked relay switchover) is less, quite a bit less, than a basic PWRgate. be advised that a relay has a much longer switching time than a FET; said another way, there is more "off" time during switchover with the relay approach than with the PWRgate approach. the ebay vendor states 7 milliseconds. whether this is important/critical is application-dependent, although i can't see a lot of reasons that the longer switching time would have any ill effects on a radio setup. on the other hand if you were powering a small form factor PC from 12Vdc, or some such, it could be a problem since unless the motherboard has enough bulk capacitance to carry through the brief power interruption, the computer will be hard reset as a result of the switchover. ar-jedi |
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Does twice as much make it twice as good? (that is a serious question)
this is the unit I have considered. LLPG by KI0BK 
they installed a West Mountain Unit in the Club Trailer, that appears to be flawless-and it was costly to say the least. |
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Quoted:
Does twice as much make it twice as good? (that is a serious question) this is the unit I have considered. LLPG by KI0BK http://ki0bk.no-ip.com/~pwrgate/LLPG/Site/LLPG_files/shapeimage_2.jpg they installed a West Mountain Unit in the Club Trailer, that appears to be flawless-and it was costly to say the least. that is the exact unit i have it. i have never "noticed" it after i installed it because it works 100%. ar-jedi |
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Quoted: Does twice as much make it twice as good? (that is a serious question) this is the unit I have considered. LLPG by KI0BK http://ki0bk.no-ip.com/~pwrgate/LLPG/Site/LLPG_files/shapeimage_2.jpg they installed a West Mountain Unit in the Club Trailer, that appears to be flawless-and it was costly to say the least. |
| For my use I don't want or need charging. Just the transfer. I do need to find an adjustable low power cut off. Say if it falls below 11 volts etc it cuts. What I want to do is run 2 batteries and when one falls below a certain level it cuts off. Then the switch can transfer over to the next supply. I can find a few online but most are $40 - 80 plus. |
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Dr_Dickie
correct, and my thinking as well. it's an all in one answer, just like the $150+ West Mountain Radio SuperPwergate. All three can net the same solution (or pretty dang close), I was just wondering if the $50 answer would work well too. I can see merits for all 3 in differing situ. |
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Quoted:
For my use I don't want or need charging. Just the transfer. I do need to find an adjustable low power cut off. Say if it falls below 11 volts etc it cuts. What I want to do is run 2 batteries and when one falls below a certain level it cuts off. Then the switch can transfer over to the next supply. I can find a few online but most are $40 - 80 plus. the relay-based units will have varying cutover voltages. said another way, one relay may let go at 5V, another at 7V, and so on. this is the result of a somewhat crude mechanical solution to an electrical problem. the FET-based units will have a far more deterministic cutover voltages, as this is set by the drive voltage applied to the FET gate. with the schematic of such a unit in hand, you could play with the resistor values that define the FET gate drive voltage, and get pretty much any cutover value you want between about 0.25Vdc and (power supply input voltage - 0.25Vdc). ar-jedi |
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that is the exact unit i have it. i have never "noticed" it after i installed it because it works 100%. ar-jedi Quoted:
Quoted:
Does twice as much make it twice as good? (that is a serious question) this is the unit I have considered. LLPG by KI0BK http://ki0bk.no-ip.com/~pwrgate/LLPG/Site/LLPG_files/shapeimage_2.jpg they installed a West Mountain Unit in the Club Trailer, that appears to be flawless-and it was costly to say the least. that is the exact unit i have it. i have never "noticed" it after i installed it because it works 100%. ar-jedi Have you noticed any problems with yours ? I bought one of those and I get horrible RF noise coming from it. I quit using it and haven't messed with it for a year or so. I think at the time I was going to try to see if there was a problem with it but never got back to it. I have a West Mountain Radio Power Gate and it works great. I had the power go off twice last week while I was sitting here in the shack and was actually on the air at the time and if the lights didn't all go out, I would have never even known I had a power outage. The guy I was working (on 2 meters) was transmitting and I never even heard a break in his transmission during the switch-over. |
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I've gone exactly the opposite direction. My primary power source for the shack, and a few other things, is solar-charged batteries. I only switch to utility or generator power to charge the batteries when the batteries get low after several days of no sun AND it looks like there won't be any sun in the near term. I keep looking at an automatic switch to go from solar to utility, but then I remember that a low-battery condition is never a surprise. There's lots of time to manually switch power sources.
I really don't like a relay-based power switching device for all the above reasons. If there's an objective to protect sensitive gear from spikes, then a relay is the wrong way to go. |
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Quoted:
Does twice as much make it twice as good? (that is a serious question) this is the unit I have considered. LLPG by KI0BK
they installed a West Mountain Unit in the Club Trailer, that appears to be flawless-and it was costly to say the least. I have one of the early beta test units. Only two output Powerpoles instead of three. But it works great. When switching over the radio does not even blink. The KI0BK LLPG and West Mountain PowerGate do exactly the same thing as the Samlex BBM (Battery Backup Module) or the BBM portion of the new SEC-1223BBM. Of course, those are rated for the 23 A power supply, and I think the West Mountain unit is rated higher. http://www.universal-radio.com/catalog/hamps/3382.html Samlex SEC-1223BBM power supply with BBM http://www.universal-radio.com/catalog/hamps/6037.html Samlex Battery Backup Module only, if you already have another supply. http://www.universal-radio.com/catalog/hamps/5603.html Similar unit from Astron. Edit: For 444, I have not noticed any noise from the KI0BK LLPG. Suggest you contact KI0BK about that. |
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Does twice as much make it twice as good? (that is a serious question) this is the unit I have considered. LLPG by KI0BK http://ki0bk.no-ip.com/~pwrgate/LLPG/Site/LLPG_files/shapeimage_2.jpg they installed a West Mountain Unit in the Club Trailer, that appears to be flawless-and it was costly to say the least. I have the LLPG in my storm-chasing box. Rock solid. We occasionally have to unplug the radio from the cigar plug in order to charge someone's phone or the GPS or whatever - not a hiccup from the radio. |
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Would something like this work?
powergate plans Not having a background in electronics, I like simple circuit stuff to build and learn on. Could a mosfet replace the schottky? Could the electrical connections be "potted" to weatherproof it? Is that large of a heat sink required? I'm not wanting to reinvent the wheel, I just think simple circuit projects like this could be beneficial to some of us. |
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Would something like this work? powergate plans Not having a background in electronics, I like simple circuit stuff to build and learn on. Could a mosfet replace the schottky? Could the electrical connections be "potted" to weatherproof it? Is that large of a heat sink required? I'm not wanting to reinvent the wheel, I just think simple circuit projects like this could be beneficial to some of us. the plans are fine as is. the arrangement shown in the schematic is known as "diode-OR'ing". the diode configuration is such that whichever input voltage (battery or power supply) is higher (by a slight amount, typically just 0.25->1V or so) will power the load (radios etc). if the two input voltages are quite close, the two diodes will carry more or less equal current. the upside of using a diode-OR'ing arrangment is that it is inexpensive and very reliable since there are relatively few parts, and modern power diodes are quite robust. the primary downside of using a diode-OR'ing arrangement is that the diode which is carrying the current has to dissipate (Ifwd * Vfwd) watts. so, for example, 20A * 0.25Vdc results in 5 Watts power dissipation (lost as heat) in the diode itself. this is why the heatsink is required, otherwise the diode will overheat and fail (open or shorted, it can go either way). the secondary downside of using a diode-OR'ing arrangement is that the diode Vfwd cuts into the battery voltage. ergo, 12Vdc at the battery results in (12Vdc - Vfwd) at the radio. depending on the type of diode (i.e. the semiconductor material used, and the junction area), and the circuit current (Ifwd), Vfwd can range from about 0.2Vdc to as much as 1.0Vdc. to your question... you can not replace the schottky diodes with just a set of FETs. every FET needs a drive circuit in order to turn on/off. whereas a diode is basically the electrical equivalent of an automatic spring-loaded (one-way) check valve in plumbing, a FET is a little more complicated valve and basically has a handle which someone/something has to turn to operate the valve. there are FET circuits known as "ideal diodes" because they have very low Vfwd and very high reverse breakdown voltage. the aforementioned PWRgate type products use these sort of "ideal diode" FET circuits primarily because it does away with two downsides illustrated above, at a slight increase in cost and complexity. ar-jedi ETA since i am probably too used to nomenclature here: Ifwd is pronounced "I forward", and is the current going through the diode. Ifwd(max) is the maximum current the diode can handle at a given temperature. exceed this and you'll damage the diode junction. Ifwd(max) is typically a function of the diode cross sectional area, and thermal conductivity to the environment. Vfwd is pronounced "V forward", and is the voltage lost across the diode. Vfwd is a function of Ifwd; the more current through the diode, the larger Vfwd is. this is due to several factors related to doping and depletion region holes. these are the two primary parameters of specifying a diode for an application. |
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Thanks for the reply Jedi! I see how the voltage drop (vfwd) could be an issue with some radios. I may put one together and try it. Cost is minimal. I have everything but the schottky diode and the resistor for the charge circuit. btw here are some diode basics... https://learn.sparkfun.com/tutorials/diodes/all here is an example "ideal diode" controller... http://www.linear.com/product/LTC4358 and also see... http://www.linear.com/product/LTC4355 you will note from the parts above that some low current (e.g., <10A) ideal diode controllers have the FET (or FETs) on board. other ideal diode controllers use external FET(s), which gives the circuit designer complete latitude over how much current can be handled, and at what cost. ar-jedi |
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Does twice as much make it twice as good? (that is a serious question) this is the unit I have considered. LLPG by KI0BK http://ki0bk.no-ip.com/~pwrgate/LLPG/Site/LLPG_files/shapeimage_2.jpg they installed a West Mountain Unit in the Club Trailer, that appears to be flawless-and it was costly to say the least. I have one and it does work great! On my Icom 746 pro it is really touchy about voltage, and small voltage drop through the mosfet causes power to drop to about 75-90 watts. I use it on my VHF radio's to maintain the battery bank and give me uninterruptible power. ETA: mine is also an older one with two power pole outlets. Oh and the Ebay auction for the relay, yea it is way over priced. Im sorry but wire nuts do not belong anywhere near radio's. |
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For my use I don't want or need charging. Just the transfer. I do need to find an adjustable low power cut off. Say if it falls below 11 volts etc it cuts. What I want to do is run 2 batteries and when one falls below a certain level it cuts off. Then the switch can transfer over to the next supply. I can find a few online but most are $40 - 80 plus. If you want to pull from two isolated batteries or power supplies, always using one with the highest voltage (to draw down evenly, for instance), some large diodes would work. You know how the battery isolators for trucks/RV's are set up as Schottky diodes in an epoxied heatsink? Well, if the diode directions are reversed, you get a passive power combiner instead. If you can live with a 0.3-0.5 voltage drop, no problem. Nothing to wear out. http://baymarinesupply.com/store/newmar-automatic-power-selector.html To protect batteries from too much drawdown, use Low Voltage disconnects at the battery terminals. http://www.rogue-engr.com/12-Volt-30-Amp-Low-Voltage-Disconnect_p_15. Sounds like a DIY project to me. |