HI,

I've got an old style battery charger which is effectively just a plate rectifier and transformer so I guess there's not actually a lot to go wrong.

For some time the ammeter hasn't seemed to be working correctly in that although it does move ever so slightly when you turn on the charger it certainly doesn't indicate more than a fraction of an amp.

There is definitely a DC output but I don't have any way of checking the actual current produced and with a modern battery I can't even see if there are any bubbles coming off the plates.

I don't really want to buy a new charger as this is used on my 6-volt vintage Austin and smart chargers seem to have issues if the battery voltage drops significantly which does tend to happen when the car isn't used much.

I was going to order a new ammeter such as:

https://cpc.farnell.com/hobut/f3pam602-10a/ammeter-0-to-10a/dp/PM11548?ost=f3pam602-10a

It's not that expensive at just under £9.00 including carriage but am I just wasting my time?

Any advice,
John.

It sounds feasible, they can be found cheaper
https://www.ebay.co.uk/itm/DC-Amperemeter-Voltmeter-Analog-Panel-Meter-Ammeter-Voltmeter-50uA-50A-5V-50V-OT/313443086775?hash=item48faa9f1b7:g:9osAAOS wWuNgQKuB

Does it charge the battery though? Maybe flatten it by leaving your lights on and then see if it will charge in the normal time

I've got exactly the same issue with my old charger, ammeter moves slightly but it does still charge fine. Both our daily drivers have suffered from flat batteries in lock down, but the charger has saved the day.

plate rectifiers do fail over time, I would replace the diode bridge with something like

https://cpc.farnell.com/multicomp/kbpc1504/diode-bridge-rect-1-ph-400v-module/dp/SC15168

mounted on a suitable heatsink

note many of the modern 'smart' chargers do 6v as well.

edit to add, you can test the old-school charges by connecting them to a spare headlamp bulb

edit 2: actually, get both ammeter and rectifier, and change them both.

[Edited on 5/3/21 by gremlin1234]

I also have exactly the same issue with an old 12v charger, Ammeter doesnt really do much, but if you briefly touch red and black together it goes full deflection, and returns

Ive not used mine in years, and even when i did, i just got to the point of i could start the car, and i certainly wouldnt just leave it switched on overnight

I just use a cheap hand held multimeter and check the voltage is above 13v, usually is around 15v and charge till the battery is fizzing. I'm sure there's more scientific ways but it seems to work and once in the car a quick run and it's done. If you are leaving the car a while a basic trickle charger is ideal but you need to check iy can regulate itself for that purpose.

if you short the wires does it then move to full output current?

if you short the wires does it then move to full output current?

Buy a new charger 🙈🙈 greedy sod. Hehe
Graham