75 Series Troop carrier auxiliary <span class="highlight">battery</span> charge problem
Submitted: Thursday, Apr 13, 2023 at 13:08
ThreadID:
145528
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4
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Chris L28
Hi, I run a duel
battery setup in my 75 series troopy which charges a 60l engel fridge and only a few small lights in the evening. The starter
battery and aux
battery are near new. The alternator was only replaced a year ago too.
The problem I have is that the alternator only seems to be charging the aux
battery up to 12.9V max, even after I have been on the road for hours. My
battery monitor is set to shut the system down when the aux charge drops down to 11.9V to save my aux
battery from being damaged. Last time I camped, I drove for three hours and I parked up at 4pm. I woke up at 6am the next morning with a warmish fridge full of food. It was reading at about 8 degrees which means that the aux
battery charge would have dropped down to 11.9 and shut the fridge off quite a few hours earlier on in the night.
Has anyone had this sort of problem?
Shouldn't the alternator be charging my aux
battery to a higher voltage after I have been on the road for so many hours? Surely it should be reaching up to a high enough voltage that I can at least park up in the evening and keep a fridge running for one whole night easily.
Thank you!
Chris
Reply By: Member - LeighW - Thursday, Apr 13, 2023 at 16:54
Thursday, Apr 13, 2023 at 16:54
When you write 12.9V I assume that is the
battery voltage after you ahve turned off the ignition?
What is the actual charge voltage the alternator is putting out?
AnswerID:
643306
Follow Up By: Chris L28 - Thursday, Apr 13, 2023 at 17:24
Thursday, Apr 13, 2023 at 17:24
Reply to LeighW
Sorry for the confusion
12.9V is the actual charge voltage that the alternator is putting out.
The
battery voltage only sits at 12.3V when ignition is turned off.
When I’m camping for days without moving, I use solar panels which increase the
battery charge to over 14V.
FollowupID:
922957
Follow Up By: Member - LeighW - Thursday, Apr 13, 2023 at 22:05
Thursday, Apr 13, 2023 at 22:05
12.9V is way to low unless the alternator is very heavily loaded.
I'm assuming you don't have the equipment to
test the alternator properly so I would suggest you do a basic
test as follows:
First fully charge the both the aux and cranker with a 240V charger. Then start the car and hold the engine speed at 1800RPM and see what charge voltage you get. I would expect the charge voltage to be between 13.8V and 14.4V. If the charge is ok then turn on the headlights on high beam, the airconditioner and the rear screen heater if you have one and again the charge voltage should remain as per above. If the charge voltage is lower or collapses with or without the accessories turned on the alternator is faulty.
Forgot to add, if voltage is low across the
battery posts
check it on the clamps themselves as the posts or clamps may be dirty. Also
check for voltage drop across the connection between the negative
battery terminal and the body work as it is not unheard of for the connection between the negative
battery cable and the body work to delovope a high resistance which causes a voltage drop.
FollowupID:
922958
Reply By: Allan B (Sunshine Coast) - Thursday, Apr 13, 2023 at 18:13
Thursday, Apr 13, 2023 at 18:13
.
Hi Chris,
We are going to need some more information to address this. Can you answer the following:
a) Did the system ever work correctly to your satisfaction?
b) After driving for a time, and with the engine still running at idle, what is the voltage at the aux
battery terminals and what is the voltage at the engine
battery terminals?
c) What is the size in Amp-hours of the aux
battery?
d) What is the wiring connection that charges the aux
battery. Is it connected to the engine
battery/alternator directly or is there a relay/solenoid between them?
e) When the aux
battery is charged to 14V by the solar, does the
battery then maintain the fridge adequately for the overnight?
AnswerID:
643307
Reply By: Mikee5 - Friday, Apr 14, 2023 at 06:58
Friday, Apr 14, 2023 at 06:58
How is the second
battery connected into the charging system? I have a Redarc SBI Smart Charger. This week my second
battery would not come above 11.5 for the first time ever. As a quick fix on the road I put a jump wire across the two big terminals on the Redarc. Solved the problem until I got
home.
AnswerID:
643309
Reply By: qldcamper - Friday, Apr 14, 2023 at 08:07
Friday, Apr 14, 2023 at 08:07
Personaly I would start at the beginning which is your alternator, as suggested earlier with increased engine speed
check the voltage at the start
battery, even a smart alternator should be at least low 13s, then carefully take a reading directly at the alternator, it should be just a little higher than at the
battery depending on the current flowing, 0.5v ish tops.
Extreem care around the alternator, slip with the probe and you will be seeing a
bright spot in the middle of your vision for a while and probably blow your main fuse.
Also that drive belt wont stop for fingers, just chew them up and spit them out in an instant.
If thats ok follow it through one step at a time till you find where the voltage drops off checking the negative side as
well.
Feel connections for heat after you have been driving for a while with a flat acc
battery.
Dont rule out a faulty new
battery.
AnswerID:
643310