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Sat Jan 26, 2019 6:15 pm

I bought three Duracell 22Ah AGM batteries for use as auxillary power shortly after I got my Westfailia in September because the existing 44 Ah battery was dead @ 1 volt. I connected the new batteries in parallel and they did the job nicely for the one camping trip we took in early December. They are isolated from the main battery via a GoWesty isolator set up installed by someone before me. I installed a voltmeter as part of the new battery install and when I parked it after that first trip, the meter was showing 13 volts or so. All seemed to be working as advertised.

After the first trip I decided to go with bigger brakes, and so while I have been working on the brakes and new springs etc., the van has been sitting since early December. I noticed today the AGMs were not registering on the meter which is connected all the time. The main battery is fully charged.

I then wanted to charge the three AGMs as they tested at 4.5 volts as measured through one of those quick connector things people install so thay can connect solar panels. I wanted to charge them so I could do a parasitic draw test and start pulling fuses to find the draw.

I connected my charger to the AGMs via the quick connector which only puts out either 2 amps or 6 amps. I set the switch at 2 amps. As soon as I plugged in the charger, the fuse in the quick connector line blew. The connector is connected properly.

If there is a question in all this, I guess t would be how can I charge these three dead AGM batteries, and why does that fuse blow? Should I pull the whole deal out of there and test each battery individually?

Sat Jan 26, 2019 7:08 pm

AGMs are going to need aboat least 14.6 volts to charge properly. Hope that charger can put out than much voltage. AGMs that are not fully charged lose their charge rapidly. Your alternator is probably not good enough to charge that setup. If fuses are burning it is probably because the batteries are pulling more charging current than the fuse can pass.

Sat Jan 26, 2019 7:29 pm

You probably have a pretty bad drain on those batteries. 2 months isn't long enough for them to drain all the way down. I would not have a voltmeter running all the time without at least a shutoff switch but I don't know if that could draw enough power to be the issue.

Since your last Aux battery was completely dead and these are now dead, you probably have a wiring issue or big drain somewhere.

I think you will have to take the batteries out and charge them separately. Could be one is bad and is killing the other two. The cover doesn't hit the + terminals does it? The wiring doesn't look awesome with the cheap crimp on connectors but unless there is a short that probably isn't your issue. Is the ground point soild, it looks like just a small screw going into the sheet metal. There is a large bolt hole that makes a nice ground, but I still sanded some of the paint off before using it.

The batteries that low will want a large current to charge so maybe that is why the fuse is blowing. I would have thought the 2A charger would limit it, but not sure. How big is the fuse that is blowing. You should set it on 6 amps anyway to charge those. If you bench charge them separately and one won't charge up, that will be a quick answer. But I doubt that will be it.

Sat Jan 26, 2019 7:40 pm

It would only take a very small current draw to drain those batteries in 2 months of sitting.

Any batteries in parallel add an additional variable in that any one of those batteries can potentially draw down the others if it has a bad cell, etc.

I would recommend attempting to charge each one individually (disconnected from the parallel setup) with a decent digital charger that plugs into the wall. It needs to be one that can handle AGM as they generally want a different charge curve.

Once you've sorted the batteries, then you can go back to what you were starting to do; put an ammeter in series and hunt for parasitic draws.

Sat Jan 26, 2019 9:49 pm

If these batteries are dead, if fitting you might replace them with a single AGM.

Sat Jan 26, 2019 11:36 pm

OK guys thanks. I'll pull the whole set up and get a spare 12v in there for diagnostics. I'll see about charging the AGMs separately or take them back to batteries and bulbs.

Sun Jan 27, 2019 6:27 am

If they are dead Dead DEAD most modern chargers will not charge if they don't see a baseline voltage.

You might have to "fool" the charger by jumping a good battery to the charge terminals hooked onto the bad battery.
Once it charges for a few hours unhook the good battery and let the charger complete its task.

Dave

Sun Jan 27, 2019 7:51 am

Check the manufacturers website to see if they have a recommended "reconditioning" charge. If they do try that...it might help.
This is Optima's take on what to do:

https://www.optimabatteries.com/en-us/support/charging/resuscitate-deeply-discharged-battery

AGM's need a higher Float Charge when they are idle. They also need a battery charger made for AGM batteries that will do this higher float charge.
I'm replacing a whole bunch of AGM's right now that are only 2 yrs. old because the previous fellow working here did not reset the chargers for AGM mode.
Be happy you only have 2 batteries...this mess is going to cost close to 15g to fix! :x Boss isn't going to be happy!

Sun Jan 27, 2019 8:27 am

Maybe with all three connected in parallel like they are, and if the voltage is low enough (4.5v), the characteristics of the AGM battery is making the charger lead fuse blow? That fuse pops as soon as the charger is connected. I'll try connecting my fully charged spare 12v to see if they come up from 4.5 v.

Wed Feb 06, 2019 12:17 pm

Turns out the volt meter I installed which is always connected draws 40 milliamps and the propex heater draws 35 milliamps even when off. 6 weeks of sitting in the driveway was enough time to kill the batteries (3 x 20 Ah)

6 weeks (1000 hours) at 0.075 amps is 75 Ah = dead batteries.

I'll be installing a switch to isolate these components when the van is waiting around for me to finish the brakes.

Wed Feb 06, 2019 4:24 pm

Thanks for the followup up post. Always curious to hear the resolution. There was another thread here that discussed that the propex has a parasitic drain but I didn't realize it was 35 milliamps. A switch is a good way to go. If it was just the propex you could pull the fuse too I guess.

Wed Feb 06, 2019 4:38 pm

Igeo wrote: the propex heater draws 35 milliamps even when off.

That's good to know about these.

Wed Feb 06, 2019 4:49 pm

Steve M. wrote: Igeo wrote: the propex heater draws 35 milliamps even when off.

That's good to know about these.

That's odd.. my propex does not have a drain at all. When it's off, it's off.

J

Wed Feb 06, 2019 8:41 pm

Quote: That's odd.. my propex does not have a drain at all. When it's off, it's off.

Have you actually checked it?

With the switch on the thermostat in the center position, the Propex HS2000 in mine will blow its fan momentarily when the power lead is connected to the aux battery. It only blows for half a second; then the current draw is a steady 35 milliamps.

Then there's this thread....

https://www.thesamba.com/vw/forum/archive/index.php/o-t--t-662371--.html

Wed Feb 06, 2019 9:40 pm

Batteries+Bulbs is a great vendor.

Tell them you want to swap for a single AGM. The more batteries you add, the worse things get -- the troublesome concept of additive power here is only as good as the weakest battery.

Hearing the GW isolator is involved is not recent news.