Thread: Electrical Alternator Charging Question

Does turning on the headlights under the same conditions also drop the voltage?

Originally Posted by Milton477

Does turning on the headlights under the same conditions also drop the voltage?

No I dont think so but will check. Nanocom output does not change at all in either circumstance only the volt meter. Trying to determine if it is a power drain or a dodgy alternator. Can not track any drain at this point.
Thanks
CraigE

Originally Posted by CraigE

I have an issue with flat dual batteries occurring. They are both fairly new with an AC Delco starting and a Optima Blue deep cycle. I have used a clamp meter to try and find any power drain with no luck. Have thought about alternator, but Nanocom is showing 13.7-13.9v and volt meter is showing around 14v when running. However when I turn on heater fan volt meter drops to around 12.5 and main battery seems to drain deep cycle battery. Anyone have any ideas.

craig, is this at idle? if you step it up to say 1500 rpm what is the voltmeter saying? i am willing to bet 2 things, firstly that the possibility is the heater fan motor is possibly to blame for excess current draw, and secondly the alternator may be requiring brushes/ slip rings etc.

jc

Are the two batteries linked in parallel ? If so could be a faulty cell in one draining the other.

Calcium batteries need about 14.5 volts to charge correctly (so my local sparky says) and he also tells me not to hook up batteries in parallel.

I had a similar problem a short time ago. The tests I did were:

1. Running voltage should be about 14.5V when charging if calcium battery was original equipment
2. Charging amp.
a) loosen positive battery terminal
b) connect jumper lead from main to aux battery (positive side)
c) start vehicle
d) disconnect loosened terminal
e) place meter between terminal and clamp (also connect earth side of meter to earth)
f) disconnect positive jumper lead and read amp being charged with & without lights etc. if sudden jump in amps when X is turned on then problem with X
g) stop vehicle and check for current draw, should only be very small.

Hope this helps

Disclaimer: I am not an electrician and there are people who are more qualified than me to answer so proceed with caution and use common sense. I had to carry out these checks recently to find a problem, and this was the only way I could do it, and it worked for me. However I take no responsibility for any damages caused.

Bad earth somewhere? Why does the nanocom does not read the same as the voltmeter?

Originally Posted by justinc

craig, is this at idle? if you step it up to say 1500 rpm what is the voltmeter saying? i am willing to bet 2 things, firstly that the possibility is the heater fan motor is possibly to blame for excess current draw, and secondly the alternator may be requiring brushes/ slip rings etc.

jc

JC,
Volt meter does not change with increase in rpm, seems to stay around 14v on gauge and 13.7-13.9v on Nanocom. When heater fan on today dropped to 12.5v. Turned off and back to 14v.
Are the brushes slip rings hard to replace?
With the heater fan I think could be an issue. Are they a big job to replace?
Cheers
Craig

Originally Posted by gruntfuttock

Are the two batteries linked in parallel ? If so could be a faulty cell in one draining the other.

Calcium batteries need about 14.5 volts to charge correctly (so my local sparky says) and he also tells me not to hook up batteries in parallel.

I had a similar problem a short time ago. The tests I did were:

1. Running voltage should be about 14.5V when charging if calcium battery was original equipment
2. Charging amp.
a) loosen positive battery terminal
b) connect jumper lead from main to aux battery (positive side)
c) start vehicle
d) disconnect loosened terminal
e) place meter between terminal and clamp (also connect earth side of meter to earth)
f) disconnect positive jumper lead and read amp being charged with & without lights etc. if sudden jump in amps when X is turned on then problem with X
g) stop vehicle and check for current draw, should only be very small.

Hope this helps

Disclaimer: I am not an electrician and there are people who are more qualified than me to answer so proceed with caution and use common sense. I had to carry out these checks recently to find a problem, and this was the only way I could do it, and it worked for me. However I take no responsibility for any damages caused.

Batteries are run through a dual battery system.

the heater blower motor is a bit of a pain as the a/c has to be dropped down to access the heater box lower bolts. i have replaced a blower fan in a defender before in situ, but it was a mission

i would take off the intake vent and stick your hand in there and see how easy the fan is to rotate. if it is quite stiff to turn then there is your answer

also, to test this theory, turn on the rear demister and the headlamps, if the volt drop is less then i would suspect the heater blower motor., have you confirmed the volt drop at the actual battery terminals or alternator output post?

jc