Smart Battery Chargers

Good, simple idea, I will make one up when I get a spare minute!! There is plenty of room inside the ring charger, so it would be nicely unobtrusive and shielded from accident.

Reply to
MrCheerful
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MrCheerful explained :

In my early days of electronics, I had the bright idea of using a very large diode, instead of the usual warning light relay - to charge caravan batteries whilst towing. I soon learned about forward voltage drop of diodes ;o)

Reply to
Harry Bloomfield

Thanks. ;-)

I was just thinking of the RW implication (considering these compact / semi sealed chargers) but you are right, there should be some spare space for a fairly small SP relay in the output line, inside the case of the traditional workshop style charger.

I have an old but good Halfords branded automatic charger that could take such an upgrade but I'll have to test if it does discharge the battery when not being mains powered first.

Cheers, T i m

Reply to
T i m

There must be a reason why this simple method isn't used to prevent reverse connection damage.

I'd guess the voltage drop make it more difficult to sense the battery voltage under all charge rates.

Reply to
Dave Plowman (News)

Dave Plowman (News) explained on 05/10/2018 :

Well I managed it easily enough, in the charger I designed. Diode on the output and sense the voltage at the battery side of the diode, as well provide reverse polarity protection. You cannot get away entirely with zero discharge, but a sensitive circuit would allow for a very low discharge, a couple of Mohm or so.

Reply to
Harry Bloomfield

The Lidl charger in question (cheap as chips) uses the more common relay operated by battery volts. Diode in that relay coil to prevent reverse connection. But it is far more than a simple charger. Once the battery is full, it switches to a maintenance charge. It also seems to run at constant current until the battery is charged - with its modest 4 amp or so output, charges a battery to full in less time than my older and much larger/heavier one which claims 11 amps peak.

Reply to
Dave Plowman (News)

That was what I have found too. Some of the old chargers had really wild claims, current outputs measured under shorted output conditions, rather than when charging a battery and the were not able to sustain that level of current without inflicting permanent damage on themselves. You only needed to look at the small cheap transformer and rectifier fitted.

Reply to
Harry Bloomfield

Yes - the older design Optimate chargers left the battery monitor circuit connected to the battery and the LEDs all lit up, when the mains failed. I measured a discharge current of 140mA. Having been caught out once I used to disconnect the charger from the battery if I was going to be away more than a day or two. We had a long standing cable fault in the road outside the house that meant the power would go off, the RCD for the garage would drop out (as they are meant to do!) and the bike battery would go flat over a week. Ok if I was at home, but not fun to come back and find a defrosted garage freezer and flat bike battery!. Only happened once - the freezer was scrapped!

it was this old model of Optimiser charger:

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The cable fault was eventually traced and fixed when the local substation cut out leaving the whole village without power and me on a

20KVA diesel generator for 3 days!
Reply to
Kellerman

I suffered from flickering house lights for a few months that I eventually traced to vehicles driving over a particular spot in the road. That used to cause quite a few (incandescent) bulbs to blow, one or two at least per week, after the cable was fixed the bulbs lasted as they should.

Reply to
MrCheerful

OOI, are you suggesting that the Oxford and TecMATE OptiMATE products were (or are) from the same stable?

I had one of the original OptiMates (the one will more of a grille case and a txfmr rather than smpsu) that died after a good few years use.

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probably the III

Cheers, T i m

Reply to
T i m

MrCheerful explained :

We had some of that a few years ago, the fault location was easy to spot - by the steam rising out of the footpath :-)

Reply to
Harry Bloomfield

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