I know you can't expect too much from the ubuquitous little compressor/tyre inflators powered off a cigar lighter plug but from the two I've had one was a lot better made than the other (e.g. the con-rod pivot pin was supported on both ends on one model, only on one end on another). Anyone have any recommendations for decent models under, say £20?
Unless you're short of space go for a jump start pack with one built in. Far more convenient. For not a lot more.
I had thought about it. Do the jumpstart packs have a mains charger for the battery or do you have to charge them separately? F'rinstance the £50 screwfix one has something that looks as if it might be a wall-wart but it doesn't say. The downside is that when and if one part packs up you're lugging around dead meat for the sake of the other functions. And for a low price you're probably getting less well-made components for each function so more probability of one or other going duff.
Veering slightly sideways what's the cheapest "proper" sealed-gel charger? LM317 with some diodes thrown in to the reference voltage to get an appropriate temperature coefficient, or are there low-cost modules that do it all off the shelf? Or off-the-shelf delta-V charger fr a 12V stack of NiMH-es? Just want a 2-3AH supply for my work radio (a car radio/CD/USB player in a wooden box with couple of speakers).
Mine came with a 1.2 amp wallwart.
I bought mine on impulse from Lidl for 20 quid about 4 years ago and didn't expect much of it. Since then it's exclusively done the tyres on both my cars - as well as jump starting half the neighbourhood. And still holds its charge.
If it's to power a car radio and not actually charge a battery a raw supply should be ok - car voltages are all over the place. And I'd expect it to cope with the odd fault too - like an alternator turned hard on. Trouble is most of these ready made units designed for CB radios etc from the likes of Maplin seem to be priced accordingly.
Thinks - I bought a pile of car battery charger transformers off Ebay a while ago on spec. They're marked 13v - and look good for at least 3 amps. You're welcome to one (or a couple) for the postage cost.
CPC ones come with a wall-wart, but it's not a proper SLA charger, and it destroys the battery if you forget to unplug it, as a collegue did to his one (plugged it in in his garage, and then remembered about it a week later). I picked up a very nice microprocessor charger from ALDI some months back, and I charge it with that. Before that, I did it from a bench PSU with accurate voltage and current setting. I think mine's about 4 years old now, but I bought one a couple of months ago for someone else, and the quality is lower - had the feeling the tyre valve connector might not last more than 10 uses.
More recently, I modified mine to add a couple of insulated binding posts to connect up an inverter. (The cigarette plug got too hot when used for a long time.) I also took the opportunity to grease the gears and cam of the compressor. (Didn't grease the piston as I don't know what the seals are made of.)
The CPC ones cost less than you can buy the 17AH SLA battery for.
Cheapest I've seen was the microprocessor based one from ALDI, which was something like £13 IIRC. I tried to get some more, but they'd run out. You can find then on the net, but nearer £40. Case graphics vary, but they all have the same set of buttons and lights, and can be set for 0.8A or 4A charging max, with a 3-stage charger and also options for 6V batteries and very low temperature batteries.
there are quite a few laptop style 12v psu's on ebay
My el cheapo Lidl one switches off when charged.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) saying something like:
For long-term LA battery charging I use a 24hr plug-in timer coming on for an hour a day, controlling the charger. Nicely does it, at little to no cost, as I have a few of them knocking around.
As well as pukka chargers I also use a couple of wall-warts as unregulated rough DC sources instead. Works well, allied with the timer, if you have a charger shortage and need to keep a bike battery (for example) topped up.
Keep an eye on Lidl - they do a superb SMPS car battery charger that does
6 and 12 volts at about 5 amps - and small enough to go in a big pocket. Switches off when charged and has a maintainence setting too. IIRC, 12 quid.We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Plowman (News)" saying something like:
I've been doing just that and every time I see them in the weekend flyer I forget about it then find they're all gone when I do eventually get there. Next time, perhaps...
I keep an eye on their offers so next time it comes up I'll mention it here. They really are exceptional value - I've seen the same at four times the price.
Sounds like the same charger I picked up from Aldi some months back.
I'm sure I chucked one recently. But I don't need a 12V *supply* (I've plenty of wall-warts that do that) but a proper *charger* for 12V sealed lead-acit or NiMH.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Plowman (News)" saying something like:
Good stuff, thanks.
but you said it was for a car radio, or do you use the box away from mains? if not ditch the batteries and run of of pure mains
I need a 12V battery supply otherwise the radio loses its settings every time it's unplugged from the mains, plus it would be nice to be able to run self-powered for a few hours, with the option of going mains when available.
Ah - right. Car radios aren't ideal as portables as they aren't generally designed for minimum current consumption. But if you like what you have I'd say the cheapest way would be to search for a cheap jump start pack - perhaps Ebay - and use the charger and battery from that.
They've come a long way from the days of class A outputs with a TO3 bolted to the case ;-). I measured this one running and it takes about 700mA. Sure a pure portable radio should take a lot less (and a Pure one would get me digital radio as well :-)) but where could I get one which would play mp3s off a USB device, for £25?! (Recent offer at Aggros.)
But if you like what you have
Indeed. Though I've also got a Stinkpad PSU in the attic that says 16V DC, and it occurs to me I could use that dropped to 12V to run the radio and to recharge a stack of NiMHs at C10 rate - can one still do that the way one could with NiCds?
Well I do - but use a timer to prevent overcharging, and only recharge when they're near exhausted.
I've got a nifty little constant current charger circuit that only uses one transistor, a couple of diodes and resistors which I could email if any use.
Does your circuit use 2 diodes to provide a constant(-ish) base voltage, a resistor in the emitter to set the constant(-ish) collector current and another R to feed the diodes on the base?
I used to use those constant-current LEDs (18mA each, 3 in parallel for C10-charging AA NiCds). Dunno if you can still get them, but they were neat.
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