‘TRAFFIC LIGHT’ CHARGING INDICATOR

A problem with early cars is that you have no means of reducing the charge on your battery other than switching it off on the switch panel.
My ‘27 Chummy handbook says the need for charging is dependent on the use of the starter and lamps and in daylight hours with the charge left on this can lead to overcharging and gassing with a reduction of the electrolyte level (sulphuric acid). Overcharging also reduces battery life and causes overheating. The situation is made worse when LED bulbs are used as the current is only a fraction of that of original tungsten filament bulbs.
You can use a voltmeter to show the state of charge of your battery, but they are big, too modern and distracting, so some years ago I discovered a company called Gammatronix who supply a small LED model J battery level monitor bulb which changes colour with voltage and can be switched for 6v, 12v or 24v (for boats!) also quickly set up to give you the display that suits you best. Search for “Battery level voltage monitor J” on eBay, including delivery it is £13.48. See full description for details. This simple device allows me to have a small vintage style lamp, which I have mounted in a small bracket on the lower flange of the dash over toward the passenger side – it is not distracting either during day or night running and not as bright as the photo shows.

I have always used an isolating switch on the earth side of my battery so when I switch it on the lamp below the dash shows me the state of charge of the battery – it flashes once every five seconds or so, green if fully charged, orange if partly charged and red if discharged. As a bonus it might even deter the sticky finger brigade who think it is an alarm! When the car is running and charging, the green light changes to constant green and when it detects overcharging voltage it goes red. At this point the charge can be switched off for a suitable period until colour change reminds you to switch the charge back on before you get back home.
In practice you are not constantly switching the charge on and off as normal running only takes about two amps for ignition if you have a mag coil conversion or zero if you use a mag.

In conclusion, I have found it to be a simple and useful addition to my car that tells me the state of charge of my battery either green, orange or red and prolongs my battery life.

Phil Witter DA7C