Trickle charge?

Well, for three months I'd say the two are the same - and it's hardly worth buying a form of trickle charger which doesn't do both.

Yes - it says it can if you read the PDF - but not in the short description. However, since you'd got the Draper wrong I didn't at first read it.

Well, there's not much point in keeping the car's memories alive while you're away if on return and trying to start the car the battery won't - and you lose the memories. ;-)

I've often wondered why - there's so little to them. Despite the glowing technobabble descriptions.

OK, I am glad you have come round to my view.

The possible reason of why these memory savers are not in wider use and hence in the general public consciousness is that their usage is not critical or essential; the lost data can be recollected in a 15 min. drive. People are also resistant to change, abhorrent of new technology.

The Draper unit functions exactly the same as the Gunson save using a different power source: batteries are less dependable than mains electric supply, since the battery used in the Draper is understandably invariably a spare old one.

The car battery should always be fully charged before it is left to the topping up from the Memory Saver. It is only prudent to do so at any rate before one leaves for 3 months. At the end of this period, the car battery will *not* be in a discharged state: that is the whole idea of the trickle charge.

By the way, the Gunson unit has no more or less fire risk, in short term or long (years), than wiring up the mains to a proximity triggered alarm out in the garden shed.

Give it a bash, I would say. :)

I've not changed my view at all. ;-)

Seem to be a lot of posts about how to 'fix' a radio when you've lost the code.

And you're likely to have two knackered batteries at the end of the storage period rather than one?

Glad you've come round to my way of thinking...;-)

If you say so. But I'm not generally impressed with the standards of construction of Gunson stuff.

You could just connect a conventional charger via a cheap segment timer such as:

-- S.C.

Thanks for all the suiggestions. I'm now off to Halfords & my car accessory shop to see what they've got.

Henry

I did consider that however Iread somewhere that whilst the charger is not charging, whilst the battery is connected to it, the current will flow from the battery & discharge itself quicker than the charger will charge it it.

Most modern chargers will indeed draw current while connected but not charging. They have a relay fed via a diode off the battery to prevent reverse connection. Also perhaps some LEDs showing battery voltage. What you really need is a charger which automatically goes into maintenance mode after completing the charge, and don't bother with a timer.

Thanks for that. I went into Halfords this morning but they had hardly any stock so I'll go to a bigger one at the weekend....or I might see if I can get one online from them.

From another thread, Argos appears to do one.

It would be a poor design that would allow that to occur. As a test, I connected my unplugged battery charger to a regulated 12.5v supply and measured a current of

-- Stephen Chalmers

Correction, I meant to write 350 microamps, which was actually much more than I would expect for a silicon rectifier. My estimate was correct for 50Ah just in case anyone's bothering to work it out.

-- Stephen Chalmers

I take it your charger has no reverse polarity connection protection? This is usually achieved by having a relay on the charger output - the coil of which is operated by the battery via a diode. Also, many car chargers will have LEDs to indicate battery status, and these also work with the charger not powered up. The current drawn by this lot on my charger is as near as dammit 50 mA - so would approx double the quiescent load on the car battery.

It has circuit breakers that trip in the event of the overload current that flows on polarity reversal, unless the battery is totally dead in which case no voltage sensor would work either.

If I understand the circuit you describe, that means that when a correct connection is made, the diode is reverse biased, so no measurable current would be drawn regardless of whether or not the charger were operating.

Also, many car chargers will

In the configuration that I suggested, that level of current would not be an issue.

-- S.C.

If the battery is that dead it can't be recharged anyway.

The coil of the relay will draw current from the battery.

It would be on a car which is laid up for a long time - as per the topic.

Thanks to everybody who proferred advice. It appears that I do not need a battery charger after all.

I have just heard that my daughter is returning to the UK for six months on a work secondment. When she is in the UK her company pays for a hire car for her, they have agreed that they will hire my car for her on their fleet insurance policy, so she will have the car for the next three months.

Just in case there is a problem over the insurance I have added her to my own insurance as this cost me only £25.

Happy New Year everyone

Henry