Battery charging

[Keith Clements]

I stumbled across thiswhilst trying to decide what fuses to put in the Dynamator circuit. It has an American slant but there are some good points in it. Notably:
The Bulk Charge Step , The Start of the Absorption Step , The End of the Absorption Step , The Float Step , Temperature Compensation
I did not understand where he said

there is no charger on the market that measures battery current!

Is he here talking about a short circuit battery current meter (one that measures in hundreds of amps)?
If you are setting up a regulator for a dynamo charging system then this information is very relevant as it monitors current and voltage and temperature compensates, but an alternator monitors voltage (not current) and its temperature compensation could only be close to the engine not at the battery so you have to trust it not to overcharge. This is OK if you use your car every week but for us classic owners a battery 'trickle' charge system is sensible to put on when the car is not being used. But care is needed not to over charge and a monthly discharge or car start up might be sensible to keep the battery healthy.

[Srenner]

"It has an American slant but there are some good points in it."

What exactly are you implying?

[Keith Clements]

Some of the words used may not be familiar to us in other parts of the world and some guessing may be required. I was actually trying to find out if a modern alternator blows up when not connected to the battery..which I never did but most say to put a fuse in circuit to stop you melting any wire.
The relays and fuses put in 30 years ago are being renewed in my SA and the system converted to run with a Dynamator with a tacho drive output. So out goes the complex switching needed for rallies to convert over to dynamo and the external battery cut off needed for racing. But I do still have a battery cut off on the earth (negative) side of the battery and a cut off on the feed from the alternator to stop the engine in the event of ignition switch failure which has happened in the past.
Having had numerous problems with cut off switches (as have others) a more accessible place has been found so they can be shorted in case of failure!
The worst I think was in Sweden in the rush hour in the rain carrying a tired and thirsty Jenny trying to find our Hotel without a decent map and no such thing as Satnav with the switch and its key having shaken loose on the cobble stones.

[Srenner]

Well yep, I reckon us Yanks might have a peculiar lingo compared to some.

My 1967 Sunbeam Alpine with a Chrysler (Rootes) alternator had a nasty habit of overheating a diode, allowing the diode to drop out of its cage fitting, causing a short that melted the wiring harness. Yes, this happened more than once with different alternators. I learned quickly to yank the cable off the battery to minimize the melting. A fuse would have been a good idea.

My understanding is that the battery acts as a big sink and if removed from the circuit, the alt/regulator can ramp up voltage and fail. I will check in the morning with the alt repair guy in the front of the other building.

[Keith Clements]

The other thing going in the electrics is the quite complex switching on the lights. This was put in for winter and night rallying to accommodate the varying conditions and failure modes. Two spot and two fog lamps complimented high power head and dip beams. The Hella spot lamps were able to light up half a mile away in the Scottish highlands in search of sheep. The fogs were able to look around hairpins on the forest stages. A hand held spot was also manipulated by the co-driver for this purpose as well. This device also acted as a flood light when stuck or when reversing or for repairs in the early morning. The car not only had the ability to dip the headlights but also dip from spot to fog or from spot to dip or head to fog. You could also run with all 8 lights on if you really needed to, but watch that ammeter as over 40 Amps was needed.
One issue with the position of the Jupiter headlamp is that you can have close shaves with on coming traffic because many drivers were not aware that there was more car on the outside of the oncoming light. They also misjudge the distance due to the closer spacing of the Jup headlights. For this reason my spots were placed in the sidelight apertures. Not very dignified or period but having them high up and widely spaced gave a wider field and length of view. Pictures from LeJog here.
The car went a lot slower with all the lights on due to the photons coming out of them. Some competitors complained of sunburn on the back of their necks when we came up behind them.

A wiring diagram and pictures of the other mods are on the old website here. You can also see the rally dashboard with Halda Speedpilot and Tripmaster.

[Srenner]

The alt repair guy and the fellow who is crew chief on a current Porsche Cup team say they never fuse the alternator wires. Better to fuse individual circuits.

The "measure current in the battery" question had them a bit confused as well. We never got a good answer.

Agreed "working" the battery is a good idea. I don't recall lead acid batteries having a memory, but might as well use up the battery as it will age out.

[Keith Clements]

The thinking behind the fuse is to protect the dynamator if the battery is fully discharged or shorted. I have each circuit fused 14 fuses in total already and have done for 30 years.