dual bat and starting problem
Submitted: Saturday, Dec 27, 2003 at 02:15
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Andrew
Hi hope everyone had a great chrismas.
Great
forum.
I have a fj60 landcruiser with a dual bat system and have been having bat problems. One battery is almost new and the other i have had checked and tested perfect. I checked with a multimeter today and it charges the main bat at 14.6v but doesn't charge the other till i flick the switch on the dash then it drops to 13.2 on each battery (at highway revs). Is this normal when charging 2 batterys and is that enough to keep the batterys charged
well? I've noticed in the past that after doing long trips with spot lights on and the battery switch on it doesn't turn over as fast as usual but still starts.
It often have trouble starting from the main battery and have to flick the switch to start and i often drive with the switch on. It's only since i've been on holidays and only doing short trips for a few days that it wont start at all. I have checked if it is drawing power while the car is off and it _Affordable_Storage_Drawers.aspx 0.5 amp from the main battery which i assume is about normal.
Also when the backup switch is on it starts using both bat is that the normal thing for a dual bat system?
I know most of you are probably thinking i should see an auto electrician but nothing is open with christmas and all the public holidays. Any help would be greatly appreciated.
Andrew
Reply By: Member - Nigel (QLD) - Saturday, Dec 27, 2003 at 11:49
Saturday, Dec 27, 2003 at 11:49
as a battery (or battery bank) charges the voltages rises to until it gets to the maximum voltage of the alternator/charger (on a half flat battery this should happen in less than an hour). At this point the battery should be 70-80% charged. The input voltage then stays at the max while the current slowly drops off (due to increasing battery resistance) till the battery is fully charged (a few hours should normally do it).
When you only do short trips you battery may never charge more than the 70-80% but that is still plenty to start the car and starter batteries tend to cope with that (for a couple of years at least).
If your charge voltage is not rising about 13.2 then you definately have something wrong. It's always best to avoid charging batteries of different ages in parallel.
The problem could also be in the size of the cable to the second battery or the current rating of the switch.
0.5 amp residual current draw sound a bit on the high side - what have you got running constantly that would draw that much? A
UHF radio should only draw about 0.2 amp when idle.
AnswerID:
41151
Follow Up By: Andrew - Saturday, Dec 27, 2003 at 13:54
Saturday, Dec 27, 2003 at 13:54
Thanks for all the info nigel. I should probably replace the older battery but money is a bit tight at the moment. I'll look at it in a few weeks after holidays are over.
I've checked the cable it is a reasonable size but a lot smaller than the main battery and it is also long (it goes right around the engine bay). I think it'd be a good idea to replace it with larger cable and shorten it but i'm not sure on the current rating of the switch.
The only thing i can think of that would be drawing current when off is the cd player. I don't have any radios.
Thanks for the reply and info
FollowupID:
303714
Reply By: Bob Y. - Qld - Saturday, Dec 27, 2003 at 12:00
Saturday, Dec 27, 2003 at 12:00
Andrew,
HJ60's had starting problems, due to poor solenoid contacts. Don't know if FJ's have similar starter issue. Sounds like you need a longer run every day or so, or hook up to a charger. Might need to check whether battery terminals are clean too.
Hooroo...
AnswerID:
41152
Follow Up By: Andrew - Saturday, Dec 27, 2003 at 14:11
Saturday, Dec 27, 2003 at 14:11
Bob,
I might check the starter while i'm messing around with it. I know my old corolla had solenoid contact problems too. It usually get's a good run every day but still has problems. The battery terminals are clean.
Thanks for the reply
FollowupID:
303716
Reply By: Member - DOZER- Saturday, Dec 27, 2003 at 14:54
Saturday, Dec 27, 2003 at 14:54
Hi
If i were a betting man i would have an each way bet on your old battery being no good.
It explains why the voltage drops down when it is put into the circuit.
Try swapping them over and running on the now aux as the main.
If thesame happens as b4, it is a electrical problem. If it wont start on the aux, that battery is showing a surface charge only.
Sounds like you have a solenoid as an isolator for the aux?
Another way of check things is to look for voltage differences by earthing one voltmeter lead on the engine, and systematcally checking each joint from the batteries back to the alt for any change in voltage, which would indicate a bad joint.
Happy hunting
Andrew
ps i have a regulator (from my last fj80) to suit a toyota 3f alt if you find it to be the problem.
wheredayathinkwer mike?
AnswerID:
41158
Follow Up By: Andrew - Saturday, Dec 27, 2003 at 16:01
Saturday, Dec 27, 2003 at 16:01
Hi The old one is the main. At first i thought that was the problem but had it tested at a battery place under load and the guy asured me it was fine. Im going to try swapping them and i'll also check all the voltages.
Thanks for the help
FollowupID:
303720
Reply By: phil - Monday, Dec 29, 2003 at 14:27
Monday, Dec 29, 2003 at 14:27
Dear Andrew,
0.5 amp is way too high. Something is constantly drawing current that is supposed to be off. Think of this, 0.5 amp for 100 hours (4 days) will take 50 amp hours from the battery and this is about the capacity of a less than new battery. No wonder it is flat.
14.6 volts is a bit high for a charging voltage. These days 14.2 seems common. It used to be 13.8 but manufacturers seem to have adopted the higher voltage, possibly to reduce charging time.
Phil
AnswerID:
41242