[Fixed] Weird Aux Batt Issue...

[Phaedrus]

I'm pretty perplexed by this one.

This aux system has been trouble-free for the past 2 years. All of a sudden, one of my house batteries is refusing to take a charge, hovering at around 2.5 volts.

Here's a rough diagram:

Basically, solar charges both the batts in parallel during the day or the batts are charged via the yandina c100 while driving. The only time the batteries are disconnected from each other is when I do a maintenance shore power charge using a dual smart charger ~once/week. They need to be disconnected because they are different agm batts.

The current issue is that I accidentally disconnected the two one night while using power. One drained completely empty, the other stayed charged. Now, the one that drained won't take a charge at all. It's as if current is just flowing over the top of the terminals, but not actually entering the batt.

I stopped at sears thinking that the batt had died (it's a platinum series marine deep cycle), but they charged it up, said it was fine, and sent me on my way.

What would cause a battery to refuse to take a charge? Failed ground? Everything *looks* fine.
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1986 WBX (Tin Top Camper)

[bmdhacks]

You mean 12.5V right, not 2.5?
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88 Vanagon Westy w/ 2200cc + manual trans

[Phaedrus]

No, 2.5v. Won't charge, won't hold a charge. For all intents and purposes, it's dead.
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1986 WBX (Tin Top Camper)

[DwarfVader]

Can you put the battery on a standalone charger overnight?

I'm dubious that battery still lives if you can't get it to hold a charge over 2.5.
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- oderint dum metuant -

I'll find my van someday, or it will find me.

[Phaedrus]

Thrown 2 chargers on it. Voltage doesn't change.

Count me dubious as well. I see another trip to sears in my crystal ball.
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1986 WBX (Tin Top Camper)

[nocreditnodebt]

Read page 12 and 13.

http://www.odysseybattery.com/documents/us-ody-tm-001_0411_000.pdf

your chargers won't try and charge a battery reading 2.5 volts.

Parallel 2.5 volt battery with a known good12v battery via jumper cables. Put Charger on good battery.

Once 2.5v battery is above 10.5 volts, one can put charger directly on over discharged battery.

[djkeev]

[crazyvwvanman]

Its not just battery chargers that can have this limitation. Some ACR models won't let the alternator charge an aux battery if the aux battery has dropped below certain voltage. Like 10.8 for example or 9.5 for another.

Mark

[Alex Proulx]

Last winter my aux batt got completely flat. The van sat in the garage for a few months, I suspect it was drained by the charge indicator led on my solar controller because the previous winter, before I got the solar panel, it held its charge fine. I was reading 0 volt, completely dead.
I bought a battery charger and I too had issues charging it so I moved the van out of the garage in full sun and the solar panel did a better job at re-charging the battery than the charger. The solar controller was pushing 20 some volts in the battery in the beginning (probably thinking it was on a 24 volt system by default?). Three days of that treatment and I managed to recharge the aux battery to over 12 volts. Unfortunately the battery was never the same after, always struggling to keep a charge, so I replaced it by a new one yesterday.
So what I'm trying to say is in my case the solar panel had no problem recharging a flat battery a modern charger could not. Maybe it could work for you as well?
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Vanagon GL 1988 Full Camper, 4 speed manual, 2.1 stock engine
Audi A3 2.0T S-Line Quattro 2015

[SCM]

Just to add to what everyone else is saying, if something caused your battery to be drawn down below a certain voltage many different chargers won't charge it.

My friend just went through this with his snowmobile battery. He thought his 1 year old $150 battery was defective. The guys at the battery store brought it back to life with no problems (this was only the first time it had drained to that level). His snowmobile has a parasitic draw that caused the issue and his "smart" charger wouldn't work to bring it back up. The battery store guys had a "dumb" charger and were able to zap it with 10 volts for a day.
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'91 Westfalia GL Automatic (GTA "Turbo" Rebuild w/Peloquin) and 2.3L GoWesty Engine

[Phaedrus]

Huh... Go figure. Thanks for the info. Never would've guessed that my charger is refusing to charge it because its voltage is too low...

I'll try the parallel method; though, I have 4awg connecting them in parallel as it is and even with the smart charger chugging away at the good batt, the flat one isn't taking any juice. I'll try disconnecting all the peripherals from the dead batt and only connecting the 2 batts via jumpers.

Will follow up.

Cheers
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1986 WBX (Tin Top Camper)

[crazyvwvanman]

You should try measuring carefully to be sure what you think is the case is really the case. Try putting the meter probes directly on the battery posts that are part of the actual battery. Measure both batteries this way. Then with the cables fully connected and the charger running on the good battery measure both again, right at the integral posts. Write down the results. There should be a similar voltage at both sets of posts. If there is a big difference then measure between the + post of one and the - post of the other. Write down what you see and then measure between the - post of the one and the + post of the other. Write down what you see and let us know.

Mark

[Gnarlodious]

The solution to this deep discharge problem is an On-off-On switch on the green wire of the Yandina relay. This allows you to manually override the automatic action of the relay and force it to engage, thus boosting the voltage to a level where the charger sees something to charge.

The green wire when grounded disables relay action. No power leaves it on automatic. Voltage applied forces it to engage. In this configuration, the voltage needs to come from the cranking battery, since the auxiliary battery is essentially dead.

If pulling this stunt on a nearly dead battery you may want to feel the heat on your cables to get an idea of the meltdown risk. You might also want to run your engine in case the auxiliary battery pulls too much power out of the cranking battery to start up. Also bear in mind that the Yandina “COMBINER 100” relay is rated at 100 amps.

All this temperamental behavior of mismatched electrical systems has convinced me that ammeters are an essential part of the system. Voltmeters are a good addition but can only tell you so much. An ammeter requires the installation of a shunt, I installed this one:
PowerWerks - Current Shunt Resistor, 100 Amp 100mV output
Less accurate shunts are available on eBay for much cheaper, and come with matching digital meters. Even if you don’t install a meter, measuring voltage across the shunt will tell you how many amperes is flowing. In the case of this one the math is simple, a voltmeter reading of 37 millivolts (.037v) means 37 amps is flowing. If you just want a shunt to diagnose occasionally, get one with a simple ratio.
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Vanagon ’83 diesel AAZ w/Giles injection, 5spd 4.57R&P+TBD and a '78 diesel Rabbit

[Phaedrus]

Seems like the little terminal splicers that allow me to screw in all of my accessories might be the culprit. Voltage reads a strong 12.8v at the batter terminals. Voltage fluctuates between 2.9v and 12v when testing from the screw posts. Super bizarre. Something is causing a huge amount of resistance. Will try ordering some new posts and see what happens.
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1986 WBX (Tin Top Camper)

[Phaedrus]

Went round and about with this one for awhile. Hard to troubleshoot based on the symptoms, but managed to figure it out. Turns out, the cheap terminal adapters I use (ACDelco/OReilly's crap) are painted at the factory. This paint covers the entire adapter and then they toss a metal spacer plate on top.

There is no metal-to-metal contact going on underneath the spacer. So, if you follow your common sense and assume good will, the only thing connecting your ancillary electronics to the batt is the threads of the screw. This was causing my voltage to read 2.0 at the screws and full at the terminal posts.

Solution ended up being to sand off the paint, attach the ancillary items, and then use the spacer as a top washer to sandwich everything down. Problem solved.

Stupid product. If you have the above photo'd terminal adapters and are having strange voltage issues, pop 'em off and sand the paint off of 'em.
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1986 WBX (Tin Top Camper)