Battery Charging Circuit & Checks

[river]

Hi,

I have noticed there's been numerous posts over time questioning if there's an issue with the alternator not charging properly.

So, I did some digging around and found some diagrams that may help you see what the actual charging circuit looks like, but also some quick and simple ways of checking if the alternator and/or voltage regulator are operating within their specified limits.

These are from a 1977 service manual for the 18R - so it should be helpful to most, if not all, 1st gen Celica owners.

I also have the information in how to pull apart and check the diodes in the alternator but I didn't include that as I assume if the following measurements show your alternator to be stuffed then you'd get it serviced, as opposed to pulling it apart and fixiing it yourself. However, for the more gung-ho home mechanics, please let me know if you want this information and I'll put it into this thread.

I made these into thumbnails for those with 56K and also so you aren't shocked with overly large images.

Hope you find the following useful.

This is the cct if you have an external alternator regulator



This is the cct you have if you have an internal regulator in your alternator
]


Vehicle inspection





Alternator Inspection



External Alternator Regulator Inspection





Oh, in Fig11-24 the plug on the alternator is... E at the top and the two vertical ones is F on the left and N on the right.


seeyuzz
river

[kingmick]

Good post River.

[WiLo]

You must spread some Reputation around before giving it to river again.

good post, it has actually helped me work out what the wiring in the mini is for

[river]

Hi,

Hey!!!!! So it works for a mini!!!!

That's cool

seeyuzz
river

[timbosaurus]

Mate, You're a champion!

This was exactly what i needed last week, and even though i just swapped to some unknown late model bosch jobby, this is very interesting to understand.

When i get permanent net access i'm looking at doing a comprehensive write up/document of the RA28 electronic system with piccies and wiring diagrams. I've had to troubleshoot nearly every part of it on my car which was difficult at times without a wiring diagram, so hopefully it might help others out who aren't as electrically minded. I think i'll have to call some favours from ppl with circuit diagrams in a couple of weeks.

Would rep you River, but have to share the love. Plus, you don't need any more rep anyway

Timbo

[river]

Hi,

No wukkers. Besides, you're right, I got more rep than an 18RG!!!!

Looking forward to your write up.

seeyuzz
river

[timbosaurus]

Hi,

No wukkers. Besides, you're right, I got more rep than an 18RG!!!!

haha... at least you deserve it

j/ks

[LeeRoy]

Good write up River. It also notable that nothing has really changed on the actual way alternators work other than their design so this will help more people out than you think.

+ve - LeeRoy

edit:

You must spread some Reputation around before giving it to river again.

Sorry River

[LeeRoy]

Here is some good info on alternators also:
Wikipedia - Alternator
Understanding Alternators
Alternators and Regulators + general elictrical theory
Some good info in these links so get reading.

In basic, alternators produce alternating current whereas generators produce direct current.
Alternators are also more efficient than generators in producing electricity but cars run on DC (direct current).

This is where diodes come in. Diodes only permit current to flow in one direction which allows an alternator to be used by changing alternating current into direct current. However, because half of the electricity is being rejected due to being the wrong direction the output wave is a series of pulses, but due to the speed of these pulses, the current produced appears to be a steady stream of DC.

Now since an alternator is designed to charge more than the maximum usage a car would have it will eventually fill the battery up with all the electricity it can hold and if it keeps charging it will damage the electrical system. This is where a voltage regulator comes into play.

Since an alternator works by having its magnetic fields produced, the amount of current produced is determined by the strength of the magnetic field. In order to control the current output, this magnetic field is switched off when the electrical system is full of charge, and turned back on when it begins to fall resulting in the voltage regulator controlling the amount of current produced through switching the alternator on and off.

The ign post on the alternator is also a vital component in the charging system. When the ignition is turned on, a signal is given to the alternator to give it the OK to charge. This is here to only allow the alternator to charge while the car is running as the electrical system can be damaged if the car isn't running.

The battery light on the dashboard is also another thing to look at. This light looks at the voltage the alternator is producing and due to the importane of electricity in your car, will switch on to warn of an implending problem with your charging system so you don't get stuck somewhere.

If i've missed something or something is wrong let me know and ill add/fix it

- LeeRoy

[brett_celicacoupe]

which wire on the back of the alternator can i join to +12V to get full charging?

ive done it before as a roadside fix on someone else's car and i think it is the N pin.

someone is using my car and its not charging, they are 400km away.

ive found its usually the regs that play up, not the alternator

anyone care to confirm this for me?

[web]

if you want 20 blown light bulbs, a boiling battery stripping your paint and a blown ecu as well as the blown alt/reg, you should definitely do that. 18-20 volts easy!

OTOH it's probably safe because not charging at all is usually the brushes. Jumping 12V to that won't do any damage (or good).

Banging the alt with a hammer does sometimes help to get you home BTW, if it's the brushes.

EDIT: oops old post... oh well...