Which is what I have and despite the assurances that 13.8v will not damage batteries if left on permanently, having lost batteries before due to evaporated electrolyte when left on....
My regime now is to leave the PSU on, but disconnect the battery after a couple of days of non-use. I put it back on throughout storage, maybe once a month for a couple of days. Sometimes I will put it on a proper charger, just to bring it to a full charge. The battery is only there for the mover and as a backup to the mains and the PSU.
Not so. It's just a 13.8v power supply which both charges the battery and supplies low volts for whatever needs it. In this case mainly lighting.
Although in my pal's case he travels to his place in Spain and back a few times a year - with dog. And needs a working fridge for his medication. So needs it to work from gas, mains, car electrics, or leisure battery. To give the maximum number of choices.
No. It's is a simple 13.8v regulated supply. As has been used to charge SLA (constant voltage) from the year dot. Wet car batteries may well be a different matter.
The charger to my burglar alarm SLA battery is 13.8v regulated. And no mobile device is going to be on charge constantly like that. Battery lasts about 10 years.
Thanks (and to others who commented). And I can see that allows the batteries to meet peak loads which would otherwise demand a bigger PSU. Anyhow, clearly no turnip for me for my cunning plan :(
Nothing except it allows the cells to be restored to full capacity quicker and without damage. It's the kind of thing APC haven't been doing for over 25 years.
Sealed batteries *may* have different requirements but I seem to remember my leisure batteries (which are non top-up'able) had graphs showing the above sort of sequence for charging. They certainly seem to work well with my solar chargers which certainly do go up to 14.5 volts or so and then back off.
No, it's 32A. The PS3 was as powerful as a contemporary gaming PC, which often took 500W+. As time went on they shrunk to smaller silicon processes which reduced the power consumption substantially - that's why the early PS3s are best for getting a high current PSU.
I've been thinking about using a Lidl smart charger with a mobility scooter battery to power a dvr and a couple of security cameras since a local shop in a shed was broken into after the mains supply to the shed was torn out, leaving the cctv useless. The charger seems to cut in and out according to voltage being between 12.5 volts and 14 when used with the battery and a light as load. I'm asking myself if the voltage variations might adversely affect the cctv equipment. Any thoughts?
But, they are really easy to modify to output any voltage within a range. Lots of info on the web, usually just a fixed potential divider, providing feedback to the switching circuit. My shack has a 50v 50amp telecoms PSU, which I modified to output 13.8v.
That was my first thought too but, apparently and incredibly, that 32A rating is correct!! The description by 'The Engineer' mentions the use of power FET synchronous rectification which eliminates, in this case, a wasteful circa half volt drop in the 32A line due to the more typical of PC power supplies cheap 'n' cheerful shotky barrier diode rectifier forward volt drop, exchanging it for a more palatable 100mV or less volt drop of a power FET's N or P channel synchronously hard biassed on resistance of mere milliohms.
This is a feature more likely to be found on the 3.3 and 5.0 volt rails since the circa half volt drop of a shotky rectifier diode represents an even larger power loss on these low voltage supply rails. In this case, we could be looking at a PSU efficiency (mains input power to 12vdc output power) of better than 95%!
That PS3 power supply looks a very tempting substitute for my earlier
60A PSU described below, especially considering their very low price (I think I paid something like a tenner each for the pair of 5v 60A smpsus I bought some 30 odd years ago when a tenner was far from being the mere pocket change it represents today).
Just over 30 years ago, I bought some ex late 70s mini/mainframe 5v smpsus (10 and 60 amp units) which I modified to produce 7.05v (10A Advance units) and 6.9v (60A units) to provide a float charger for
400AH's worth of battery via a 20A Shotky rectifier and a 60A 13.8v transceiver supply respectively by wiring them in pairs to series connect their outputs.
Sadly, one of the 60A units blew up a year or two later (some 30 years ago now) but the float charging pair, much to my surprise, are still going strong despite the battery being retired from service and dismantled about ten years ago and my 10A 'charger' being left unused in a damp basement radio shack environment (along with a Kenwood TS140s and other kit).
I recently retrieved the Kenwood and the 'charger' from their basement home a couple of weeks ago to save them from further deterioration. I'm happy to say that the transceiver appears to have survived its ordeal by high humidity quite well - it only needed its slider and switch controls exercising to restore them back to their original operational state and all seems well.
I've not been able to check the frequency calibration against WWV on
10.000MHz but reception of Radio Merseyside on 1485KHz using either USB or LSB shows no perceptible shift of the demodulated audio frequencies which is an encouraging testament to the frequency stability of this transceiver after well over a decade's worth of 'irresponsible storage'.
Getting back to the issue of using/modifying smpsus, the higher spec units bring out their sense amp inputs to additional terminals so that they can compensate for the volt drop in the current carrying cables that feed the load. In the case of ATX psus, the 3.3v supply uses a sense wire connection to one of the three orange wires going to the MoBo connector. Ideally, there should also be a sense amp connection to one of the zero volt connectors as well which looks to be the case with the test rig ATX psu I have on my workbench.
When it comes to modifying such old skool smpsus for a higher voltage, the sense amplifier terminals prove to be a Godsend in that if offers a quick 'n' dirty way to boost the voltage output[1]. The sense amplifier input is normally a high impedance input and will normally be connected internally to their respective negative and positive output terminals via a hundred ohms or so resistor so that the output voltage remains regulated even when the sense wires are unused (perhaps rising by a millivolt or two in this case). Using the external sense wires will override the internal resistor's influence by virtue of their typically sub ohmic connection.
What this means is that we can leave the external sense amp connections open circuit and add a shunt resistor across the sense amp terminals which forms a potential divider with the built in resistor links which increases the output voltage to restore the sense amp input voltage back to the set voltage.
We can either 'measure' the resistance of the internal sense amp connections so as to calculate the required shunt resistor value or else just 'steam in' with a high starting resistor value to get an indication of what order of magnitude value of variable resistor will be needed to empirically arrive at a required resistor value. If the smpsu has an accessible voltage trimpot as mine did, then the closest E12 series resistor value can be arrived at and wired directly across the sense amp input, leaving any final calibration to the built in trimpot.
I suspect the mods described by the 'Experimental Engineer' are simply a variation of the above relying on leaving the external sense amp connections unused in their new repurposed configuration.
[1] Output filter capacitor voltage rating allowing - a point well made in those articles by the "Experimental Engineer". Also, another thing to consider is whether a 'damping load resistor' is wired across the output and what value and rating it is since it might need to be replaced with a larger value resistor of a suitable wattage rating. Last, but not least, is the issue of 'overvolt protection' which may limit the amount of voltage 'boost' you can apply.
Some O/V protection circuits simply work to an absolute set limit, others, more intelligently, work to a percentage overvolting factor (this was the type of AT PSU that could be tripped by voltages backfed through the PC's printer port during the initial voltage build up from switch on
- a level of 'intelligence' that was a little too effective for its own good).
The damping resistor loading was something else I had to consider with my own voltage mods. Indeed, the presence of such loading resistors was the reason I had to include a blocking diode between the battery and my '14.1v charging brick'. In this case, I'd replaced the original 8.2 ohm
5W resistors with 24 ohm 3W resistors.
Whilst modern low power designs of smpsu may have done away with such damping resistor loading, high power units such as those Play Station ones might still incorporate a damping resistor. However, in view of the use of high efficiency synchronous switching rectification, I'd expect such resistive loading (if any exists) to be a lot lower than was typical of more traditional designs so might not be an issue in this case.
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