hi all, see ebay item 230075728863, car has 12 volt batt, with 6 volt tap, ????????? is this possible?
how does it work ? a very perplexed Dai.

the glove is down!!!!!!!!!!!!!!!!!!!!!!!!

Hello Dai,

Not too sure what you mean about "the glove" - maybe I am just "uncool!"

(No, not maybe, I am!)

Have had a look at the Ebay item you referred to.

Basically I think that all that has occurred is that someone has fitted a 12 volt battery and used the full 12 volts connected to the Starter Motor, which would spin it quite quickly.

The rest of the electrics are fed via what looks to me to be a fairly inadequate piece of cable to drive the rest of the 6volt components from a 6 volt tap on the battery.

One would then presume that only the 6 volt "half" of the battery would be subject to charge (if any) fron the car's dynamo.

I would have to presume that the 12 volt battery would receive a charge from time to time from an external battery charger.

All in all, a bit of a lash up. I wouldn't rush out an follow suit.

Regards
Barry R.

Dia

I cant really see the point in what has been done?
Maybe I am missing something but I would either stick with all 6V electrics or change to all 12V , to have 12V start and 6V everything else seems a trifle pointless when you have a starting handle to swing on? As Barry points out how do you charge the other half of the battery?

Steve.

p.s I dont get the glove , so I am obviously "uncool" at 32!

I asked the Seller to explain what he meant by the 6V tap - here is what he said...

"The battery is an old fashioned one with the inter cell connectors on the outside, A 12 volt battery is made up of 6 2volt cells , a 6 volt one is 3 cells, So I have them made with a terminal half way along the battery, thus giving 6 volt supply to the original equiptment. Then only the starter main wire connects to the other 12volt terminal, sending 12volts to the starter, this makes it spin very fast & makes it start very easy plus this allows a constant 6 volt to the ignition side, points etc. if you have a 6 volt battery on once the starter is activated, there is not 6 volts available to power ignition system. I have used these on lots of 6 volt cars, it has nothing to do with the charging normally I fit them & every thing works as normal."

Not quite sure I understand what has been done, would like to see the installation and a diagram to make sense, but hope that answers the initial question that was raised on the Forum.

I'm sure Barry will reply, BUT I cant see how the other cells would be charged? Perhaps I am dim, but I think you would have a half charged battery?
I also think that the starter pullling across all the cells would drop their voltage down so you wouldnt have 6V for the coil etc anyway?

As you say it would be nice to see more wiring detail on this in case we are missing something?

Steve.

G'day all,
Although this battery business sounds like a "good" idea, it is fundamentally flawed, as mentioned in previous posts, as the upper cells are not charged (and the advert text admits that the charge light is on!). In them good old days, a similar but betterer solution inplemented to overcome voltage drops in VW wiring, was an 8V battery. Using the same battery style as shown in the advert (external links), a tap was made at the 4th cell and everything was run off that. A simple "tweek" of the voltage regulator spring mounts trimmed the charging voltage up an extra two volts, and all was OK (I had the best starting VW in town!).

I think that Dai was refering to the gauntlet rather than the glove. ie a challenge! (From the days of Knights of old).

Cheers,
DG

This seller is obviously on to something. He has managed to fit a battery into a vehicle which has "nothing to do with the charging"

Either he has brilliantly managed to provide a 12 volt battery on which one half never needsd charging, or else he has a makedhift lash up to overcome a poorly maintained 6 volt system.

290,000+ Austin Sevens are proof of the fact that there is enough voltage available in a 6 volt system to turn over and fire the engine, provided everything is up to scratch.

There is absolutely no doubt that a 12 volt system will do the job easier and with less risk of failure because only half the current for the same energy is required. This means that the resistive losses in the system are much less critical.

Let us assume that a poor connection provided a 0.1 ohm resistance

A 0.1 ohm resistance at 10 amps will drop 1 volt

If that occurred in a 6 volt operated circuit, 1/6th of the battery supply would be lost.

But in a 12 volts system, the resistance would still be 0.1 ohm, but the current to do the same work could be presumed to be 5 amps and only 0.5 volts woul be lost. And it might be observed that 0.5 volts is only 1/24th the battery supply.

So there are inherent advantages in a 12 volt system, and there are some excellent and well proven sytems which can be easily applied to an Austin Seven, but this particular seller has not applied them.

The principle of tapping batteries was well practised here in OZ in the late 1950's - 1960's when there were a lot of surplus 6 volt Car Radios around which appeared useless in a 12 volt vehicle which were then becoming the norm (this was in the days when the Asian influences in our electronics industries had not bitten, and radio gear was relatively expensive)

A tapped battery provided music in the car for the cost of a self tapping screw.

regards

Barry R.

I presume Dai means throwing down the gauntlet - right Dai? I'm obviously very cool and still young free and single, but don't expect me to tell you how old I am!

Jeff

Forsooth, and a gallant Knight such as myself should have needed no explanation.

regards


Barry R

yes gauntlet would have been better, just i wear gloves now i am getting older, but thank you all for raising to the challenge, think i will give it a miss and stay 6 volt, cheers Dai.

Due to all the questions about the 6- 12volt battery: The battery is an old fashioned one with the inter cell connectors on the outside, A 12 volt battery is made up of 6 2volt cells , a 6 volt one is 3 cells, So I have them made with a terminal half way along the battery, thus giving 6 volt supply to the original equiptment. Then only the starter main wire connects to the other 12volt terminal, sending 12volts to the starter, this makes it spin very fast & makes it start very easy plus this allows a constant 6 volt to the ignition side, points etc. if you have a 6 volt battery on once the starter is activated, there is not 6 volts available to power ignition system. I have used these on lots of 6 volt cars, it has nothing to do with the charging normally I fit them & every thing works as normal. Please see pictures. vender added this today, cheers DAI.

I fitted both battery terminals via cables from my 6volt battery to the starter (in otherwords I did not rely on the bodywork for the earth return), and it spins very well, in fact the Cornish lads said it sounds like a 12volt system.

So why prat about with 6/12v etc. I don't think I could get a 12v in my RP saloon battery box anyway.

In the 60's I mounted a lorry 6v battery on a plinth under the bonnet, it may not have spun the starter any better, but you coud drive all night on 'bright' headlights (this is a relative term).

Sandy

Me too, my earth strap goes to one of the gearbox top studs.

I drove from Kemble in Gloucestershire to Whitchurch in Shrops in the dark one night (with a v poorly engine). Started at 9pm, got home at 2am. Thankfully I only had to go down Birdlip. Theres nowt wrong with 6V

I have to go along with Barry R regarding the advantages of 12v.

During the late 30's ( I believe ) Lucas put out a publication, not only expressing the advantages of 12v but also indicating the methods to be used for conversions ( 2 brush dynamos ! ).

If 6 volt systems were adequate for motoring in an age other than when you were likely to be the only person on the road then they would be still with us today. Commercial vehicles have used 24 volt for many years and with modern battery technology the chances are ( if the petrol engine car survives ) that 24 v systems will appear in private cars ( if they have not done so already ).

As to the tapping 6v off of a 12v battery, it is fine to do so on a 12v system to achieve 6v as the whole battery is still receiving a charge.

With the tapping at 6v being the system voltage and the 12v only being used for starting problems may occur if the upper 3 cells of the battery are excessively drained then the flow within the battery could be reversed across adjacent cells causing damage to the battery.

As they say, you should never mix new and used batteries in appliances.

By the way, I used to have a battery lawn mower which had a 12v battery with an 8v tapping ( a propper battery round post, three posts in total ) which was made for the job, this allowed you to have a two speed mower.