Optimate and inductance - beware

Thought I'd share this.

My last battery went in the bin after a short life of a matter of
months. This was because the Optimate said it was charged but in fact it
was flat as a shrove tuesday delicacy. I know, I should have suspected
the charger. Assuming the battery died of being left on the bike for a
long time, I decided that when not using the bike, it would be a good
idea to leave it connected to the optimate (off the bike).

Next thing, the Optimate starts telling me that the new battery isn't
taking a charge (permanent dim, yellow light). I'm thinking, "oh no -
another battery buggered".

Those of you that have Optimate chargers will know that the cables -
mains in and 12V out are very long. Well, mine were all twisted up
together. I un-twisted them and hey presto. All seems well again. I
haven't yet tested the battery - perhaps I'll attach it and go for a
spin tomorrow.

I can only assume that this is down to inductance betwen the cables? ie;
the 220V input was infecting the 12V output.

Am I talking out of my bottom?

--

Paul.
CBR1100XX SuperBlackbird (Buen mueble de patio)
BOTAFOT #4
BOTAFOF #30
MRO #24
OMF #15
UKRMMA #30

 

Paul Carmichael wrote

Probably not. It all depends on how Optimate do their checking and this
is something we simply don't know.

It has been noted before the Optimate system does seem to behave rather
oddly at times and quite a few reports have been posted here verifying
this.


As to what causes it, **** nose but in the death the best test of your
battery is to connect it to the bike and use it.


That said I use a very simple, very cheap, battery charger of my own
design and construction[1] which will charge any battery capable of
being charged enough to prove it is working in about 5 minutes. To say
that what I do constitutes a gross mistreatment of the battery in
question is an understatement but I don't get battery problems. Draw
your own conclusions.

Does Optimate have a "charge regardless" function? If so, use it.



[1] A 10V Hi-amp transformer and a full wave rectifier pack and bugger
all else. Crude, to say the least, but very effective.

 

Which is what all the traditional LA chargers used. I had an ancient
Wilmot-Breedon 4A charger that would rescue and recharge just about
anything with acid in it. Replaced by a Halfords jobbie of the same
design philosophy which is almost unbeatable.

Fairly raw and ripply DC that pisses in the sink is what LA plates want
to see, not a smooth New-Charger characterless Direct Current that eats
quiche, washes the dishes and doesn't wipe its knob on the curtains.

 

Actually you're not. I've had similar problems with the connectors.

 

Grimly Curmudgeon wrote

Well yes, although mine is capable of short bursts of 50A which makes it
useful for the larger batteries of the sort found on the Mongvan for
example.

Yes and no. Yer modern sintered plate battery things are supposed to be
designed for a slightly gentler approach to charging but how this
relates to what the alternator puts out I would not like to say. Other
than, batteries are generally tougher than the Optimate sales literature
would have us believe.

 

ian field wrote

A Cockcroft Walton Voltage Multiplier you mean? Unnecessarily over
complicated bollox for those who know little or nothing but who wish to
impress those who know even less. Have you never heard of KISS?

 

ian field wrote

Otherwise known as a diode pump, I believe.

Thus turning it into a diode pump.

Quite.

 

Pity you got the circuit wrong though. You add a couple of caps but you
also need to reconnect the transformer.

Just putting a big electrolytic capacitor across the output of a traditional
battery charger will give over 20v with no load. Of course, once you
connect it to a 12v battery the output drops to 13v or so.

 

Sorry, should have done more thinking before posting.
But my circuit will give 20v at a lot more current than yours.
How much voltage and current does a sulphated battery need?

 

Hey, I try hard to Rock & Roll All Night...

 

ian field formulated the question :

I don't think that advice will work with an Optimate, they use a switch
mode system producing a perfectly smooth DC output.

 

Paul Carmichael explained on 24/02/2007 :

More likely it will be a result of oxidation or corrosion on the
connectors, preventing the charger seeing the battery voltage.

This is the one thing I really dislike about the Optimate... I get a
full set of 3 LED's lit whether it is connected to the battery or not,
assuming the battery is fully charged anyway. It thus leaves you
guessing as to whether it is connected properly or not. I wonder if a
resistor connected across the Optimates output would pull its open
circuit voltage down enough, to make the LED display a little more
sensible?

 

Harry Bloomfield wrote

All a bit tenuous though innit?

There is obviously a rather big flaw in the way Optimate does the
checking and it seems to me they are looking at the battery as a current
sink rather than a voltage source (if that makes sense) and any extra
impedance in the circuit of the sort caused by corrosion or other poor
contact buggers it completely.

The fact that it is touted as The Ultimate Solution and folks come to
rely upon it when it most demonstrably isn't is a good enough reason for
me to dislike it.

Which further reinforces my view that it is not the battery it is
testing but it's own output.

Only one way to find out really. How about substituting a resistor for
the battery and see at what current things change?

 

Which Optimate is that? My Optimate II doesn't do it.

 

mb has brought this to us :

I'm not sure which model it is. It is about 12 months old, but provided
as a replacement for one which failed. All black plastic case and three
LED's with opaque square plastic covers over the LED's.

The LED's light up in an unpredictable way with mains, but no battery
connected, but do make sense once the battery is connected. Trouble is
that because they are so unpredictable that you can never be sure the
battery is properly connected or the in-line fuse sound.

 

You should be aware that Optimate is in fact a brand name and trade
mark, referring to a specific product. I've never seen a black one;
my Optimate III is grey, with normal round LEDs - they certainly do
not have square plastic covers. I believe that older designs are sold
under other names, which may have black cases and other cosmetic
differences.

FWIW my Optimate functions perfectly, as far as I can tell. One LED
if it's on and not connected, and two when it is connected, indicating
the relevant charge status.

 

DR pretended :

What I have has now been renamed a 'Maximiser' - which explains some of
the confusion.

Mine is the one at the bottom of this page:-
http://www.mandp.co.uk/productInfo.aspx?catRef=500070

 

Paul Carmichael formulated on Sunday :

Shocks from PC's, washing machines and similar high tech items will be
due to the mains input filters. They are connected between L and E plus
N and E. Some voltage can also be induced onto unearthed metalwork in
close proximity to mains wiring.

 

I was largely basing my assumption on recent experience with my house
electrics. I live in a house built in franco's era ie; stuff wasn't
available. There was no earth rod. All my stuff was plugged into
extensions that were wired for earth. We kept getting electric shocks
off the computer cases, washing machine etc. I put it to the test by
simply plugging an extension lead into a earth-less socket and testing
the earth core with my amazing Avometer. Sure enough, over a poxy 2
metre length of extension, there was a lot of welly being induced
(inducted?) into the earth wire. And I tried this with more than one lead.

--

Paul.
CBR1100XX SuperBlackbird (Buen mueble de patio)
BOTAFOT #4
BOTAFOF #30
MRO #24
OMF #15
UKRMMA #30