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Charging issues (sp250)

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JSabah
Posts: 118
Joined: Mon Feb 15, 2016 9:27 pm
Location: Los Angeles

Charging issues (sp250)

Post by JSabah »

Electrical gurus needed. I’ve searched the forum but don’t really see what I’m in search of.

My battery (5 yr old AGM battery with very few cycles on it as I don’t drive the car much) seems to get very low after driving short distances (5-10 miles). If I park and then restart it it is slow to tick over. I’ve charged the battery every morning for the past few days and it goes down to about 65-70%.

I checked the residual voltage by starting the car and letting it fast idle for a few minutes. Then disconnected the Field and Arm wires at the dynamo and checked voltage between the Arm and housing expecting to see .5-.75 volts but I had zero. I then flashed the dynamo 1st at the Dynamo (arm to bat) then again at the regulator and re-checked for residual … still nothing.

Was my process correct? Do I need to get the Dynamo rebuilt? Do I need to have the regulator matched (it was restored when I rebuilt the car less that 1000 miles ago).

BTW while driving my voltmeter (yes I changed) reads 11+ v while at idle ant up to 15v while driving at speed.

Looking forward to hearing from all as I’ve been absent for a while.
Sp250, Sunbeam Tiger, MGTD, Jensen Interceptor conv, Jensen Interceptor Coupe', '49 Plymouth Woody and now a '65 Jensen CV8 Mk3 LHD

Ian Slade
Wise Man
Wise Man
Posts: 791
Joined: Sat Feb 13, 2016 9:54 am
Location: Sevilla Spain

Re: Charging issues (sp250)

Post by Ian Slade »

There is nothing wrong with your dynamo if it charges at 15v, your problem is the battery it shouldn't drop below 12.5 volts, from your description I would consider it has died, batteries don't die on the cycles it is a chemical action and batteries have a life span of 0 to7 years though they have warranties these basically cover manufacturing defects, the battery temperature when charging can seriously affect its life.
A fully charged battery should read new 13.2 volts if it reads 11v after charging and no use overnight then you have lost a cell, 2.2 volts ie 13.2v minus 2.2 equals 11volts, if you check after charging you will find the battery will drop to 11v within an hour
Owner since the 70's, Genghis is slightly to my left.

HenryC
Helpful Person
Helpful Person
Posts: 402
Joined: Mon Feb 15, 2016 8:31 pm
Location: Surrey / East Hampshire

Re: Charging issues (sp250)

Post by HenryC »

Batteries do not last long if they are not used. Lead acid batteries last longest if they are 'cycled' regularly, ie used everyday/weekly.

Time for a new battery. :(
Cheers, Henry Curwen
Registrar for Conquest & Century Saloons (DJ250/1, DJ256/7, DJ260/1)

Conquest (Drop Head) Coupe DJ252

Flinty
Posts: 90
Joined: Mon Sep 24, 2018 7:34 pm
Location: Scarborough

Re: Charging issues (sp250)

Post by Flinty »

TO flash a Dynamo you need to have a loose wire from battery to FIELD terminal of Dynamo just touch the terminal a couple of times.
To check voltage output you need to connect both Field a Armature terminal together on the Dynamo and take voltage reading to earth.

Steve.

JSabah
Posts: 118
Joined: Mon Feb 15, 2016 9:27 pm
Location: Los Angeles

Re: Charging issues (sp250)

Post by JSabah »

Flinty wrote: Wed Sep 22, 2021 9:49 am TO flash a Dynamo you need to have a loose wire from battery to FIELD terminal of Dynamo just touch the terminal a couple of times.

Steve.
Yikes… do you think I damaged anything by touching the Arm terminal?
Sp250, Sunbeam Tiger, MGTD, Jensen Interceptor conv, Jensen Interceptor Coupe', '49 Plymouth Woody and now a '65 Jensen CV8 Mk3 LHD

JSabah
Posts: 118
Joined: Mon Feb 15, 2016 9:27 pm
Location: Los Angeles

Re: Charging issues (sp250)

Post by JSabah »

Ian Slade wrote: Wed Sep 22, 2021 8:54 am A fully charged battery should read new 13.2 volts if it reads 11v after charging and no use overnight then you have lost a cell, 2.2 volts ie 13.2v minus 2.2 equals 11volts, if you check after charging you will find the battery will drop to 11v within an hour
I’m thinking you guys are right and that my problem is the battery. While charging on my charger, it got stuck for a while at 88% (but the voltage was just over 13v). After a about an hour it went to 100% BUT while putting a voltmeter across the bat terminals, it read 12.56v. After two starts and idling for a few minutes (wanted to recheck the residual voltage after correctly re flashing the Dynamo) the voltage across the battery reads 12.47. Battery is disconnected and will recheck later it tomorrow to see if there is a drop.
Sp250, Sunbeam Tiger, MGTD, Jensen Interceptor conv, Jensen Interceptor Coupe', '49 Plymouth Woody and now a '65 Jensen CV8 Mk3 LHD

JSabah
Posts: 118
Joined: Mon Feb 15, 2016 9:27 pm
Location: Los Angeles

Re: Charging issues (sp250)

Post by JSabah »

JSabah wrote: Wed Sep 22, 2021 8:19 pm
Ian Slade wrote: Wed Sep 22, 2021 8:54 am A fully charged battery should read new 13.2 volts if it reads 11v after charging and no use overnight then you have lost a cell, 2.2 volts ie 13.2v minus 2.2 equals 11volts, if you check after charging you will find the battery will drop to 11v within an hour
I’m thinking you guys are right and that my problem is the battery. While charging on my charger, it got stuck for a while at 88% (but the voltage was just over 13v). After a about an hour it went to 100% BUT while putting a voltmeter across the bat terminals, it read 12.56v. After two starts and idling for a few minutes (wanted to recheck the residual voltage after correctly re flashing the Dynamo) the voltage across the battery reads 12.47. Battery is disconnected and will recheck later it tomorrow to see if there is a drop.
Update : after about 24 hours the battery voltage is at 12.38, which is down from the 12.56/12.47. Probably enough juice to start it a couple of times, then I experience the slow/no turn over. Still sound like the battery?
Sp250, Sunbeam Tiger, MGTD, Jensen Interceptor conv, Jensen Interceptor Coupe', '49 Plymouth Woody and now a '65 Jensen CV8 Mk3 LHD

Bud
Posts: 318
Joined: Fri Feb 12, 2016 9:06 pm
Location: Rochester, NY

Re: Charging issues (sp250)

Post by Bud »

Well an easy test would be to start your car from a friends car or another battery and just listen to the difference in sounds,
Is it r-r-r-r like yours or is it zing spin and start like it should. If it is a sealed unit then you can't replenish the acid mix, so-o-o reach into the coffee tin and off to the parts store, Take the old one in for a load test and if it fails leave it for refund or recycle and bring home something shiny and new.

bobtills
Posts: 186
Joined: Wed Sep 25, 2019 6:05 pm
Location: North Wales

Re: Charging issues (sp250)

Post by bobtills »

I would suggest getting a friendly local garage to test it - preferably one that employs elderly mechanics.

Take it out of the car, charge it up fully then take it to be tested. Having it fully charged and out of the car eliminates any other possible interference with it's state of charge.

A good friendly local garage can test it in a minute or so and (in my experience) they would be happy to receive a box of biscuits and a big 'thank you' but even if they want to charge something it won't be much. Or you could take it to a local battery supplier and they could test it.

Then you will know :D

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