classic car forum header
Classic cars forum & vehicle restoration.
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Register     Posting Photographs     Privacy     F/book OCC Facebook     OCC on Patreon

6 volt charging rate.
Goto page 1, 2, 3  Next
Post new topic   Reply to topic    Classic cars forum & vehicle restoration. Forum Index -> Electrical Restoration
Author Message
Ray White



Joined: 02 Dec 2014
Posts: 6286
Location: Derby

PostPosted: Fri May 11, 2018 3:56 pm    Post subject: 6 volt charging rate. Reply with quote

I have recently suffered from my ‘26 Dodge Brothers tourer failing to restart after taking it for a run. The 6 volt battery is quite recent but it had failed to hold it’s charge. On testing, the reading was 4 volts.

I checked with my workshop manual and was rather surprised to read that the dynamo charging rate in normal conditions is 14 amps. I would have thought this was too high; indeed, elsewhere in the same manual it is recommended that the headlights are kept on ‘dim’ to avoid over charging the battery.

Where I become confused is that I thought the reverse current cut out prevented the battery from becoming overcharged.

In the past, I have always ensured that the ammeter needle was just edging into the ‘charge’ side. Am I to assume the third brush on my dynamo needs adjusting?

If I need to, what should I set the tick over ammeter reading at?
Back to top
View user's profile Send private message Send e-mail
ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Fri May 11, 2018 7:44 pm    Post subject: Reply with quote

Hi Ray

A 6v lead acid battery is made up of 3 cells each with a nominal 2.1v, a reading of 4v suggests a short or very low electrolyte in one of the cells.

In terms of charging rate; it's very easy to overcharge a battery charged with a 3 brush dynamo as the regulation is a bit crude, but does work albeit that the battery would probably have a longer life if charged by an alternator.

Lead acid batteries prefer a low current trickle charge, 14 amps may be the charge just after starting, but it should drop, however if a cell in the battery has shorted, the dynamo will show a high current as it tries to bring the voltage up. I'd be inclined to load test the cells and or measure the SG in each cell to determine the battery state.

Dave
Back to top
View user's profile Send private message Visit poster's website
Ray White



Joined: 02 Dec 2014
Posts: 6286
Location: Derby

PostPosted: Fri May 11, 2018 8:19 pm    Post subject: Reply with quote

Hello Dave. Thanks for helping. I charged up the battery so I could get the car back in the garage then left it for a couple of days. When I hit the starter it fired up straight away. If there was a problem with the battery I would have thought it would not have held the charge.? The problem I had was after I had driven the car for about 12 miles. For what it’s worth the battery is a maintenance free sealed one.

I am thinking that the dynamo output is not enough to keep up with the battery. I have had the dynamo rebuilt and fitted an electric fuel pump and flashing indicators so there have been a few changes

Do you think I Should increase the third brush output?
Back to top
View user's profile Send private message Send e-mail
MVPeters



Joined: 28 Aug 2008
Posts: 822
Location: Northern MA, USA

PostPosted: Fri May 11, 2018 11:03 pm    Post subject: Reply with quote

Ray

I think I'd hook up a volt meter & see what's going on.
Just a couple of basics:
You won't see much happening at idle.
Once started & driving in daylight, you should see about 7.2V on the volt meter & quite a high charge rate on the ammeter.
The 7.2V should stay pretty constant & you don't want much higher.
The amp rate will drop as it re-charges the battery; this may take a mile or more.
If you turn the headlights on, the amp rate will drop anyway while driving. At idle you may well see a negative value.
Once you compare your experience with this, you'll be in a better position to see what needs adjusting.

This is probably far more data than you need!

http://forums.aaca.org/topic/278462-how-do-i-adjust-the-third-brush/

I hope this helps.
_________________
Mike - MVPeters at comcast.net
2002 MINI Cooper 'S'
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Ray White



Joined: 02 Dec 2014
Posts: 6286
Location: Derby

PostPosted: Fri May 11, 2018 11:17 pm    Post subject: Reply with quote

MVPeters wrote:
Ray

I think I'd hook up a volt meter & see what's going on.
Just a couple of basics:
You won't see much happening at idle.
Once started & driving in daylight, you should see about 7.2V on the volt meter & quite a high charge rate on the ammeter.
The 7.2V should stay pretty constant & you don't want much higher.
The amp rate will drop as it re-charges the battery; this may take a mile or more.
If you turn the headlights on, the amp rate will drop anyway while driving. At idle you may well see a negative value.
Once you compare your experience with this, you'll be in a better position to see what needs adjusting.

This is probably far more data than you need!

http://forums.aaca.org/topic/278462-how-do-i-adjust-the-third-brush/



I hope this helps.




Thanks. Yes, I am very happy for any assistance. I tend to plough a lonely furrow here in deepest Derbyshire so when I get something out of the ordinary I tend to rely on you guys on the forum.

I have tried the volt meter and it reads less than it should. I am getting 6.5 volts and the ammeter reads about 6-8 amps. I can try going further than just down the road if it helps?

At idle the amps are just into the positive range. It doesn’t go into negative at idle.
Back to top
View user's profile Send private message Send e-mail
Keith D



Joined: 16 Oct 2008
Posts: 1127
Location: Upper Swan, Western Australia

PostPosted: Sat May 12, 2018 2:01 am    Post subject: Reply with quote

Ray,

My Chrysler is also fitted with a three brush Delco Remy generator and the charge from this does not vary because of the battery's condition. There is no regulation at all other than the normal idle cut-out. At any given engine speed the charge rate is constant. (about 10A at 70km/hr) Because most of our driving is on less congested roads than in the UK, I usually drive with my headlamps on after the first few kilometres. My last battery (normal lead acid) lasted over seven years.

If the car is unused for any length of time, I trickle charge the battery at least once a month. Many people of my acquaintance use solar panels to effect a continuous trickle charge.

My headlight switch has a rather crude pressed cardboard insulator that has warped somewhat with age. On the back of this there is a resistance coil that is activated when the "dim" is selected. Quite frankly, I am scared to ever use this as incredible heat is generated and I don't want a fire under the dashboard.

Keith
_________________
1926 Chrysler 60 tourer
1932 Austin Seven RN long wheelbase box sedan
1950 Austin A40 tourer
1999 BMW Z3
Its weird being the same age as old people.
You are either part of the problem or part of the solution
Back to top
View user's profile Send private message
MVPeters



Joined: 28 Aug 2008
Posts: 822
Location: Northern MA, USA

PostPosted: Sat May 12, 2018 3:22 am    Post subject: Reply with quote

Ray

I'd say the amps you're getting are OK, if maybe a little on the high side. Leave it for now.
The 6.5volts is sort of OK, but it's just a trickle charge.

You mentioned a 'reverse current cutout'. What is in that unit?
Is it possible there's some voltage adjustment possible with that? Be aware that if there is any adjustment, it has to be done in minute increments.
You might check that the contacts are clean, they oxidise rather than burn. You're supposed to use a 10/- note or crocus or flour paper, not a file or emery cloth.
_________________
Mike - MVPeters at comcast.net
2002 MINI Cooper 'S'
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Ray White



Joined: 02 Dec 2014
Posts: 6286
Location: Derby

PostPosted: Sat May 12, 2018 12:32 pm    Post subject: Reply with quote

Keith D wrote:
Ray,

My Chrysler is also fitted with a three brush Delco Remy generator and the charge from this does not vary because of the battery's condition. There is no regulation at all other than the normal idle cut-out. At any given engine speed the charge rate is constant. (about 10A at 70km/hr) Because most of our driving is on less congested roads than in the UK, I usually drive with my headlamps on after the first few kilometres. My last battery (normal lead acid) lasted over seven years.

If the car is unused for any length of time, I trickle charge the battery at least once a month. Many people of my acquaintance use solar panels to effect a continuous trickle charge.

My headlight switch has a rather crude pressed cardboard insulator that has warped somewhat with age. On the back of this there is a resistance coil that is activated when the "dim" is selected. Quite frankly, I am scared to ever use this as incredible heat is generated and I don't want a fire under the dashboard.



Keith




Keith.

It sounds like your Chrysler and my Dodge have the same kind of headlight
‘dim’ switch and like you I don’t use it for the same reason! As Chrysler bought out Dodge (in a world record for a business deal) I don’t suppose it is surprising there are similarities.

The voltage regulation is also very primitive with just a cut out (similar to many other cars of the period) but what interested me was that you are charging at 10 amps. M.V. Peters, as you will have seen, thought my 6 -8 amps was a bit high. It is not charging the battery enough but I am assuming the battery, being only a few months old and seems to hold a charge is in good condition. My manual infers that the charging rate that I have would be more suited to a 12 volt battery but mine is 6 volts and as I have said the manual suggests 14 amps which just seems too high but then they they suggest using the lights. I understand half the volts = twice the current so presumably the manual is right The difficulty I have is that I have always had the charge just into the positive range on the ammeter on my 6 volt Austin Seven and that has been sufficient. Do bigger cars take more from their batteries than small ones? It’s just something I have never considered before.
Back to top
View user's profile Send private message Send e-mail
jp928



Joined: 07 Jun 2016
Posts: 249
Location: Australia

PostPosted: Mon May 14, 2018 3:41 am    Post subject: Reply with quote

I have a Lucas 3 brush unit on my 26 Rover, and I have adjusted its brush to minimize the output. These genys are different from US units, in that the 3rd brush holder is held in place inside the genny by 3 screws, one of which is difficult to get at with the unit on the engine, but it can be done. It seems that 3 brush systems have no charge regulation, just a cut-out. FWIW there is a firm in the US who make a solid state regulator/cutout for T-Fords -http://www.funprojects.com/products/5055r.cfm. If this unit is fitted between the battery and the original cut-out (with its cut-out points shorted)it will act as a cut out, and dump excess current when the battery is full. It comes in 6V,8V, 12V , but only negative earth.
jp 26 Rover 9
Back to top
View user's profile Send private message
Ray White



Joined: 02 Dec 2014
Posts: 6286
Location: Derby

PostPosted: Mon May 14, 2018 10:17 am    Post subject: Reply with quote

Thanks for replying, J.P. I have possibly got to adjust the dynamo output a bit more to keep the battery charged up. I was wondering if perhaps there was a standard formula for determining the dynamo output for a given voltage at a particular r.p.m.? Or is this a trial and error thing?

My first job, I think is to make sure the cut out contacts are clean. I have a brand new spare one so it might pay me to fit that instead.
Back to top
View user's profile Send private message Send e-mail
jp928



Joined: 07 Jun 2016
Posts: 249
Location: Australia

PostPosted: Mon May 14, 2018 12:40 pm    Post subject: Reply with quote

Dont know of any way to calculate - so many different dynamos etc. I have had trouble keeping the cut-out points clean - its built into the Lucas central switch, and very difficult to get more than a narrow length of emery paper in there. I know now that when a voltmeter across the battery shows fast changes in voltage I need to clean those points again. The only safe thing is to turn on loads like side or headlights so that the current is minimal for most of the running time.
jp 26 Rover 9
Back to top
View user's profile Send private message
Ray White



Joined: 02 Dec 2014
Posts: 6286
Location: Derby

PostPosted: Mon May 14, 2018 2:04 pm    Post subject: Reply with quote

It is my understanding that you should avoid using emery cloth. Apparently carbon can become embedded in the soft metal of the points and set up resistance. This weakens the effectiveness of the points and can cause faster wear through arching.

Fine sand paper works o.k. But you might only need a piece of clean writing paper.
Back to top
View user's profile Send private message Send e-mail
jp928



Joined: 07 Jun 2016
Posts: 249
Location: Australia

PostPosted: Mon May 14, 2018 11:24 pm    Post subject: Reply with quote

I have never struck any 'points' that I would describe as 'soft'. I have used fine wet'n'dry paper a few times with the desired results. Ignition point files are pretty hard and sharp- why would the cut-out points be any different? Paper certainly wouldnt make any impression on them.

jp 26 Rover 9
Back to top
View user's profile Send private message
47Jag



Joined: 26 Jun 2008
Posts: 1480
Location: Bothwell, Scotland

PostPosted: Tue May 15, 2018 10:04 am    Post subject: Reply with quote

JP,

Ignition point are making and breaking constantly when the engine is running there have to be harder to survive. The cut-out however closes when the engine starts and that’s it until the engine stops. You will find they are silvery and softer in comparison to the ignition point so the advice given previously stands.

Art
Back to top
View user's profile Send private message
jp928



Joined: 07 Jun 2016
Posts: 249
Location: Australia

PostPosted: Tue May 15, 2018 1:38 pm    Post subject: Reply with quote

You live and learn, thanks. Is there a way to reduce burning due to current through these points?
jp 26 Rover 9
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Classic cars forum & vehicle restoration. Forum Index -> Electrical Restoration All times are GMT + 1 Hour
Goto page 1, 2, 3  Next
Page 1 of 3

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
OCC Merch link
Forum T&C


php BB powered © php BB Grp.