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Forum Index : Electronics : Old Arlec Battery Charger
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Revlac Guru  Joined: 31/12/2016 Location: AustraliaPosts: 1024 |
Arlec PS439 After all these years it finally gave up........Ha, the damn thing is older than me, Its had a lot of use over the years and a few repairs, voltage selector switch and so on. Went to use it today to top up a set of 80 lithium 18650's, just to bring them up to about 4v or thereabouts, its been good for this sort of thing because of the select able voltage switch, something a smart charger does not have, or some do and I don't know about it yet.   I found it was not putting out any current when charging, and it had some stink coming out of it. This is the guts of it, The old style (I believe it is a) selenium rectifier.  And a check of the output with the little scope revealed some nasty half wave I was putting into the battery.  The transformer appears to be ok, I should check it properly after the rectifier is removed.... I think its worth the effort to repair it, already have more than enough things that need fixing, But as yet haven't seen anything that I like that would replace this charger. Time to find some rectifiers among the bits and pieces in the shed, busted Alternators etc.  Cheers Aaron Off The Grid |
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| johnmc Senior Member  Joined: 21/01/2011 Location: AustraliaPosts: 282 |
Good day Aaron. I always used auto alternator diodes no cost and easy to get. cheers john johnmc |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Golly !! Its been a very long time since I saw something with a selenium rectifier in it. Alternator diodes will work, but may be difficult to heat sink and mount. I would be using something like this: https://www.ebay.com.au/itm/MDQ-150A-1600V-Black-Single-Phase-Diode-Bridge-Rectifier-150A-Amp-High-Power/373228150516?hash=item56e6219ef4:g:C90AAOSw3uxfacbY Very easy to just bolt down into the case, because the heatsink is insulated. And it will be totally indestructible. Edited 2020-10-22 06:32 by Warpspeed Cheers, Tony. |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1024 |
@john, you have probably seen many automotive chargers over the years, things have changed a bit, much less of them in use now, for modern vehicles. Good to hear your still well. @Tony, those diode packs are nice and neat, would be good on a descent heatsink without any fan, would need a pair of them for the 2 windings I would also like to keep those bi-metal circuit breakers if possibly, they have done there job many times, might need a little adjustment, the 24v side was cutting out a little easy. When I was a kid, I had the opportunity to see (probably shouldn't have) a big old 600v Mercury-arc Rectifier in action, not many about anymore. Actually, I just saw the exact same one, The Brisbane Tramway Museum, There is a YT video of it. Cheers Aaron Off The Grid |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1024 |
Rectifier blocks arrived today, they are nice beefy looking things, will make up some heat sinks for them, don't think they will need all that much. Just another job that needs doing.....later.   Cheers Aaron Off The Grid |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Those rectifier blocks will survive anything up to and possibly including a direct nuclear explosion. Cheers, Tony. |
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| greybeard Senior Member Joined: 04/01/2010 Location: AustraliaPosts: 161 |
Cockroach rectifiers!  |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1024 |
The diode blocks are in and mounted on a small heatsink.  Give it test run and there is the ripple, I think the output voltage is a little higher than before. I tried it with a capacitor on the output and that flattened it out completely but that was running without a load on it.  With the filter cap on the output and charging the battery there is some ripple but not bad at 15Amp, I could filter it a bit more.  Its also putting out more current than the old diode set, so much better, run it for half the day and confirmed my heatsink is inadequate, it not too hot but could do better also about 3 hours in I burnt through the jumper cable I had connected to the back of the charger, been using them because they had a bit more length to play with than the others that were there. It is one of those cheap jumper/booster leads that are copper coated aluminium that always stuffup at the clamp ends, Anyway apart from all that, its up and running again, happy with it. Cheers Aaron Off The Grid |
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Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1057 |
Hi Aaron Good to see you got it going again. I assume the lower impedance of the diode rectiers would be the reason for the higher charge rate. RE Jumper leads. I say the only difference between a 200A cheap set & a 600A cheap set is the thickness of the insulation. I had to jump-start my old Greenfield Ride-on the other week. Battery had open circuit cell. Had to resort to welding cable leads I had made up years ago as "normal" jumper leads just didn't cut the mustard. I've sometimes wondered what the effect on batteries is to have a high voltage, high current charging pulse applied to them (in chargers without filtering). Some stuff I've read (when researching chargers for starter batteries for a diesel loco) suggest a low ripple rate for charging in order of only amps for a 1500CCA battery. BTW, what size capacitor is that you are using? From my limited experience, you would need at least 100,000uF for 10A to get a smoother input to the battery (~ 1V p-p ripple) itself. Also, somehow, your bottom DSO shot doesn't look right? Did you change your connection points or the load from the one immediately above? Enjoy the hot weather today & the next few days. (I hope to be down in Ipswich on Wednesday at QPSR. Will be nice & warm) Brian ChopperP |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1024 |
Hi Brian, I jump started the old tractor, battery was a little tired and the tractor hadn't been started for years and the fuel had just been primed, brought over a 250A tractorpack welder, lowered the voltage a little to suit, and hit the starter, she was up and running in 5 seconds, the starter was going a bit faster but it was ok. I checked one of the 12/24v pwm SCC, it had horrendous ripple, it a 250w panel VOC of 34V and charging a 12v battery, I guess most of then are like that. The arlec charger never had any filter in it originally, The cap I put in is 8700uf when the picture was taken with a load, without a load and cap in place its just a straight line. The DSO connection points are on the same wires, just on the out side of the case instead of inside. This photo today, I added a 22000uf and its made a difference, almost flat, (I was charging a 90Ah of 3.7v lithium 18650's at 15A) perhaps it could be improved with a choke fitted also it creates a bit of a spark and burns the clamps when connecting, easy fix was to charge the caps by switching the charger on low power before using it.  I haven't Checked any other chargers for ripple yet eg, the old Telecom rectifiers. The hot weather is something, so is the plague of mice eating the bait and stinking.  I'm going to check the starting current on the old greenfield, (Honda 13hp) I need to get a new rectifier for that as well. Cheers Aaron Off The Grid |
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