Defender Source Forum banner
1 - 14 of 14 Posts

·
Premium Member
Joined
·
440 Posts
Discussion Starter · #1 ·
My truck has dual batteries in series,but within the last week at start up power is too low to turnover the engine.All I hear is the clicks coming from the starter but when I boost the truck It runs fine.I checked the output from the alternator and charged up the batteries ,which held the charge for about 3 days.The alternator is good so I suspect the batteries.How can I test the batteries as I think the bad battery is draining the good battery.
 

·
Premium Member
Joined
·
4,644 Posts
Jorge. I have a battery tester which tests the condition of the battery. YOu can pick one up somewhere or if you find someone with one near you, borrow it. It shows the state of charge and if the battery is still good. If you are in the Paramus area anytime soon, I would help you out no prob.


Randy:proud
 

·
Premium Member
Joined
·
4,789 Posts
You can also go to AutoZone and they will test them for FREE! They will bring the tester right out to you 90 so you don't have to take out the batteries. I would guess that one battery is bad and it is taking down the other. Oh yea, the batteries are in parallel not series, Series would give you 24 Volts. Autozone also sells Optima Batteries and keeps them in stock.
 

·
Premium Member
Joined
·
116 Posts
I actually think your problem might not be either of the batteries. Both of the Defenders I have owned had a similar problem with just the single battery setup. In both cases....the rectifier part of the alternator was bad, and allowed a tiny amount of ground to remain present even when the truck was shut off...which in about three days, drained the battery.

This also happened to a friend who drives a '97 SW. In all three cases the fix was a new alternator. In older cars..the rectifier was a separate box that could be changed out cheaply...but in most newer autos...the rectifier circuit (which changes the alternating current generated by the alternator into DC to charge the battery) is integrated into the alternator. It could also be a short in the setup you have for the dual battery configuration.

scot
 

·
Premium Member
Joined
·
4,789 Posts
If thats the problem then you could also install a battery cut off switch.
 

·
Premium Member
Joined
·
440 Posts
Discussion Starter · #6 ·
I purchased my truck about 8 months ago.Here some history on the truck, my tac sometimes works and sometime stays at zero then works again.I have tried to fix the problem by checking the alternator(160 amp hi output) hookup following the wire to the ecu and tightening all connections.I've used grease everywhere possible but problem still exist.This charging problem just started I already checked the battery connections and the alternator output and all appears to be normal.What I will try next is to check the output of the alternator when the tach is showing zero and see if there is a difference in voltage.
 

·
Premium Member
Joined
·
126 Posts
Be careful of testing the battery while in the truck. I had a friend who bought a used BMW and soon after, it started losing juice and not holding a charge. He checked through the alt and took it in. The real problem was a bad solder on a ground connection, but because they tested it in the car it looked like the battery was draining.
So he got a new one and guess what? The problem was still there. If you're losing power check all the ground connections and test the batteries outside of the truck, as well as obviously checking the alt.

Have you checked the alt. belt while the tach is at zero? Is it running? If the alt is spinning and the gauge shows zero, I'd suspect a connection somewhere as well.

pwc
 

·
Premium Member
Joined
·
4,789 Posts
I don't think its your charging system, if you can't bringit down to test the batteries then I would run it for a while then park it, disconect both batteries from each other and from the 90. measure the voltage. THen wait a few hours and check the voltage again. The voltage should not drop below 12 volts which is low. If you can wait 2 or 3 days then try reconnecting the batteries then one at a time and try starting off of each one on its own. This would rull out the batteries. If you think the alt is not charging I would hook up a Volt meter to a fuse and watch the voltage all the time while driving. It should not drop below 13.5 volts. If both of these check out OK then I would think that something isdischarging the batteries while the 90 sits overnight.
 

·
Premium Member
Joined
·
440 Posts
Discussion Starter · #9 ·
I check both batteries today and found one couldn't keep a charge when put under a load test.The batteries are connected with the main wire to the starter going to one battery and the alternator wired to the other battery with another wire conecting both positive posts .The ground wire is connected to the battery with the positive post going to the starter and another wire connecting to the other battery negative post.I know it sounds confusing but I need to rewire the batteries( buying optimas) any suggestions or should I keep the same wire scheme.
 

·
Premium Member
Joined
·
4,789 Posts
The only thing I would do is add a wire going from the Neg post of one battery to the frame for a good ground.
 

·
Premium Member
Joined
·
440 Posts
Discussion Starter · #11 ·
Well I did it, purchased two blue tops.I'm going to connect them as per the scheme on the expedition exchange tech site( thanks J. Lee).I'll be connecting the winch Hellas ect. to the stainless steel threaded stud and the battery cables to the regular post.I checked for power drain but found none as of yet ,so I hope my lose connection to the + battery post caused the batteries to fail.
 

·
Premium Member
Joined
·
4,789 Posts
Cool! are the blue tops OK for starting, I thought they were a Marine battery.
 

·
Premium Member
Joined
·
440 Posts
Discussion Starter · #14 ·
Same as the deep cycle yellow top but come with the threaded studs and the posts on top.
 
1 - 14 of 14 Posts
Top