by ericmark »
Fri Jun 08, 2018 9:27 am
There are many ways to control the charging of lead acid batteries, the simple method is voltage, we use for a 12 volt battery between 13.2 and 14.8 volt (OK an old two bobbin regulator was set at 16 volt open circuit voltage, but connected it never reached 16 volt.) At around 13.8 volt you can connect a whole series of batteries in parallel with no problem. However with stage chargers which could charge at 14.8 volt then yes each battery should be independently charged.
With a stage charger often the charge current as well as voltage is measured, so typical is.
1) Max output until volts reach 14.8.
2) Volts held at 14.8 until current drops to 5 amp, exact amp limit depends on amphour rate of battery.
3) Volts held at 13.4 volt to maintain the battery until connection lost.
You can get stage charger regulators for alternators, Sterling make some, but they are normally only used with boats.
You can also get battery to battery, and alternator to battery inverters, again mainly boats, it will allow for example two 80A alternators to combine outputs and charge 3 x 160 Ah batteries in parallel using pulse charging very fast, and the forth engine start battery is just float charged at 13.6 volt.
However in the main vehicle alternators from old cars i.e. not connected to engine management, use a simple voltage regulator, some tractors have a temperature sensor under the battery, but in the main you could have 20 batteries in parallel using a vehicle alternator without a problem.
What was often done was to fit relays, so batteries only connected in parallel during charging, but separated when being used. The typical split charging relay so popular years ago with caravans.
On the Falklands we ran out of regulators for alternators, so to keep the fleet running we fitted a tail lamp where the regulator should have been, and swapped bulb sizes to get charge rate some where near to what was required.
So the same method could be used to de-rate the alternators, a simple resistor between the supply to field, i.e. the brushes.
Yes there were some specials like the CAV 203 alternator where it was current regulated, but really these were only used on buses, unlikely to find on standard car or wagon.
The best way to regulate the output would be speed, so larger pulley on alternator (use a dynamo pulley) will slow down alternator so allowing petrol engine to speed up and produce more torque, or of course smaller pulley on petrol engine.
