Pulsing when charging

[mack3737]

I noticed when charging my batteries with the engine, service batteries fed from port alternator and engine start fed from the stbd. alternator, that my volts and amps needles were pulsing!
Amps going from 5-10A and volts showing 14.6-14.8.
In the opinion of the forum does this indicate there is a problem and why is this pulsing showing up on both the service and engine circuits? The volts and Amps meter are common with change over swithces to select their function.

 

[VicS]

I think I would be looking for an unintentional interconnection between the two charging circuits, perhaps as the result of the wiring of the voltmeter and ammeter and the associated switching.

Not clear from your post however if you are referring to two alternators on the same engine or on two separate engines. If the latter do they behave normally if only one engine is running.

Also not clear if you mean a voltmeter and an ammeter that can be swtiched to monitor one circuit or the other or whether you mean one instrument that can be swtiched between both functions on both circuits.

Or two instruments, one for each circuit, that switch from volts to amps.

 

[CPD]

Assuming there is no load variation (R) during the charging, then the variation in voltage (V) will directly affect the current (I). V=IR with R fixed means that v is directly proportional to I in other words if the voltage doubles then so will the current which isnt happening in your case. This, my dear Watson, leads me to believe that there is a potential problem with your instrumentation, however in order to conclude the matter, more evidence is required.

I am guessing that you don't have digital readouts, ie you have traditional meters from which you read against a scale. When you say pulsing, what is the frequency of the pulsing - is it very rapid, or very slow, and if slow, over what time period ?

 

[Cliveshep]

Old type instruments do show "pulsing" until the engine revs go up when they stabilise. Quite common. Is that the scenario with yours? Slowish revs pulsing, higher revs stable?

 

[mack3737]

Re: Pulsing when charging- more info.

In response to your learned comments, one engine fitted with two alternaters, pulsing at cruising speed eg 2100 rpm, frequency of pulse about 1 sec., have two meters fitted( analogue), one for amps one volts, the change over swicth is in between reading service or engine start battery function.

 

[William_H]

[ QUOTE ]
V=IR with R fixed means that v is directly proportional to I in other words if the voltage doubles then so will the current which isnt happening in your case. /quote]

Just so we don't confuse our dear readers Mr Holmes (i am sure you understand the shortcomings of your statement)

I=E/R but of course a battery on charge is not an R it is a very non linear kind of resistance which varies with voltage. So if voltage is 5v and you double it to 10volts you still won't get anything into a charged battery.
But if voltage is 13v and you double it to 26v the current, if able to, will rise to huge amount limited only by the battery departing for heaven.
Or put another way a battery on charge at 13v might take 3 amps but at 14v might take 30 amps.
So in the case of the op any small change of voltage is likely to give a large change in current.

Assuming that all circuits are isolated from one another (and you should check) then the only likely common factor is the earthing of the engine to the batteries and alternator to engine. Any small resistance here may cause interaction one to the other. good luck olewill waffling again

 

[cliff]

Do you have "smart" regulators fitted such as a Sterling alternator regulator or similar?
These will pulse the charge after they sense the battery is "full" or nearly "full".
---------------------

Artificial Intelligence is no match for Natural Stupidity.

 

[halcyon]

Re: Pulsing when charging- more info.

First thing is get your multimeter and check if the voltage at the batteries are pulsing. If pulsing check engine to battery negative, only common circuit.

If stable check the voltage at the input to the selector switch, if this is stable the fault is switch or meter.

Check input to output terminals on the switch.

If this is stable, check between the switch output terminal and the meter terminal.

If this is stable disconnect the meter and connect the multimeter and see if stable, if so the meter is the fault.


Brian