Builds 1988 BJ74 “Number 1” (2 Viewers)

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Maybe that's what happened to my brain. My batteries are not disconnected in any way. The system is 24V, the charger is 12V with two leads. I understand what you mean though.
 
You do not need to disconnect the batteries to charge them individually. You must however connect the charger leads to the actual battery posts. One pair on each battery. Never the chassis ground, only the battery posts.
 
Pulsing a sulfated battery back to life may take a long time. Apparently that happens to your one battery.
After the battery is back to a minimum charge and low internal resistance, the charger switches from pulse-recovery to a normal charging cycle. It is a controlled charging, though, thus might take longer on a somewhat affected battery, compared to a healthy battery. But it applies a normal amount of energy. If the battery is really unhealthy, this may still cause a sudden death, e.g. an internal subcell short-circuit.
Each "12V" battery internally is composed of 6x2.1V subcells and has actually 12.4 to 12.8V at full charge (that's what the lead acid chemistry is). So, one subcell passing out causes the unit's total voltage to drop by ~2V.
This may have happened.
> Disconnect both the chargers, allow 10min pause for internal balancing, and measure the questionable batteries' voltage. If below 11.0V: it's dead. Else: Give it another try.
Good Luck Ralf
 
Thanks FJBen for letting this discussion continue here. Good info. Just bought a Noco Gen5x2 and wasn't confident on the set-up.

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:rofl:




Glad it is helping! I don’t mind any hijacks. Lots of good tech and troubleshooting even if it doesn’t directly apply to my rig.


Tech wise , I bet that one battery is shot. Save the good one for another vehicle. Switching the charger is a great idea to rule that out. You can take the batteries to a store that can run longer tests to see what’s going on with the battery and how much “health” the good one has left, but it’s looking like 2 new batteries
 
Switch the leads to the opposite batteries and see if the light pattern follows the battery. If it doesn't there is a problem with the charger.
I think we can rule out the charger.
IMG_4426.jpeg

I'm not disputing that I likely do have something draining the batteries but it gets me to thinking. Is it possible that these batteries are old and one has completely failed (true) and replacing both with strong batteries would resolve the issue? Which is to say, is there a certain amount of drain that wouldn't affect strong batteries? Or will whatever drained these batteries just as quickly drain new batteries? I suppose that depends on what is causing the drain but for the sake of conversation, perhaps we assume normal things like the clock, doors being periodically opened, etc. Thoughts?
 
I think we can rule out the charger.View attachment 3232522
I'm not disputing that I likely do have something draining the batteries but it gets me to thinking. Is it possible that these batteries are old and one has completely failed (true) and replacing both with strong batteries would resolve the issue? Which is to say, is there a certain amount of drain that wouldn't affect strong batteries? Or will whatever drained these batteries just as quickly drain new batteries? I suppose that depends on what is causing the drain but for the sake of conversation, perhaps we assume normal things like the clock, doors being periodically opened, etc. Thoughts?
May or may not relate to your experience but then again it might. My Ute is 12V but has a second battery that is managed by a National Luna system. If I drove the truck everyday I never noticed an issue but if I let it set for 4-5 days it would be slow cranking. I assumed a parasitic drain was the culprit but as it turned out one of the batteries which was less than 2 years old was the problem. Since replacing the battery (the cranking battery in this case) I’ve had no further issues. Its it’s a parasitic drain the new battery seems capable of handling it.
 
what I have experienced is that if you are replacing batteries in a 24v truck, replace both at the same time with ones that have the same build date. One old and one new will cause what you see. Got so tired of this I am switching to 12v.
 
May or may not relate to your experience but then again it might. My Ute is 12V but has a second battery that is managed by a National Luna system. If I drove the truck everyday I never noticed an issue but if I let it set for 4-5 days it would be slow cranking. I assumed a parasitic drain was the culprit but as it turned out one of the batteries which was less than 2 years old was the problem. Since replacing the battery (the cranking battery in this case) I’ve had no further issues. Its it’s a parasitic drain the new battery seems capable of handling it.
This is exactly what I was thinking about. I do plan to replace them both at the same time.
 
Battery #2 took 14 hours to recharge. Battery #1 took 24 hours MOL. I suspect they'll both need to be replaced but I'll leave them on the battery tender until I can drive it with some consistency and see what happens. Thanks as always for the great advice. Nice to see those green lights anyway. View attachment 3228160
MOL?
 
what I have experienced is that if you are replacing batteries in a 24v truck, replace both at the same time with ones that have the same build date. One old and one new will cause what you see. Got so tired of this I am switching to 12v.

This is the way to do it. The batteries need to be as close to identical as possible to keep the bank balanced. It also helps to maintain the balance by charging them individually, like the way you are now doing, as opposed to a single 24 volt charger.
 
We have a solution!

In my experience, every time a battery does something odd like being low for no reason, it usually is bad or goes bad quickly.

I have a feeling my battery is going to 💩 out soon. Especially since it will be -8F tonight. Not even trying to start it.

I will say, 3 glows on my 98 tdi jetta that’s sat for a week cold soaking, started instantly. The heater starts working super quick. So far quite the bargain at $1,200.
 
That's one (of many) things that I miss about my '97 Jetta. I started it a couple of times at -18ºF, no trouble at all. I was lucky to get my Prado started yesterday at 0ºF, it refused the morning before at -11ºF.
 
The X2 AGM?
I put one in the LX and loved it.
I just replaced it a few months ago.
We ran that battery down to the point where the truck died when the alternator was dead.
I charged it on an AGM charger for several days and then it lived a few more years.
I ran the fridge off it as well. It got down to 11 volts multiple times and then still started the truck.
It lasted ~5.5 years. It still worked, but the cranking was slower. Coincidentally, the amp died a month later, not sure if it could have been pulling on the battery?
2 thoughts - prices have gone up, and they went from I think 4 year replacement to 3 year.
Update, I got a replacement amp that worked for a short time, and now exhibits strange behavior (cutting out at certain frequencies and levels). THis one put quite a draw on the battery when the vehicle was OFF. So now I am wondering if our old battery was fine, but the amp was drawing it down w/ a parasitic draw.
 
I hope I’m not interrupting my thread with some tech on my vehicle…. :flipoff2:

Anyway, after the Koito H4 upgrade I did…2 years ago,…I’ve been without a bright light indicator. The Koito upgrade only has you use one connector for the factory harness which upsets all the electrical magic and makes your bright light indicator not work.

Enter @CruiserTrash
HBIM - High Beam Indicator Module for Koito Headlight Upgrade Kit - https://cruisertrashparts.com/products/hbim-high-beam-indicator-module-for-fj60-koito-headlight-harness

I was slumming in the 60s section and saw mention about the Koito upgrade, and since well I thought maybe at some point I could have some tech to bring to my thread…I reached out to cruiser trash.
He was willing to do a full refund if it didn’t work but thought it should looking at a schematic. I thought that was a great of a vendor and for $30.00, I wasn’t worried about a refund, I could always donate it to someone else. He’s also in Denver so about an hour away, local cruiserhead too.


Quite a nice little piece.
7C74AD87-18E9-425C-ADBD-AA3BA51A96D4.jpeg



Success!
9DD85E36-AD24-4DC0-AA23-BD3C29744821.jpeg


Some tech notes…

3E3EA6A4-3394-4796-B8C3-D4F3DF6077A9.jpeg



So for 12v only, it appears to work on the 70 series in this age range/wiring setup. It’s about as simple as repairs get. Plug it into the factory harness, boom done.

I have my off-road lights tied into my bright switch and everything so far seems to function just fine.
 

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