TheSamba.com :: View topic - 87 Syncro

Mon Jul 28, 2025 9:42 am

With my current set up, I have to keep my Aux battery on a trickle charge if I don't drive the Van at least once a week.
The Aux battery runs the interior camping lights, the propex heater, the radio, the usb port, and likely a couple other small things. Nothing is on when it sits, but it draws a charge and goes dead.
Both my van battery and aux battery are new, and the isolator and dcdc charger system is new in the last few years. I've had a couple mechanics tell me this is normal to have to do the trickle charge.
I don't necessarily want to have an extension cord running out of my house to the Van all the time. Someone mentioned I could install a shut off switch that could be utilized if it's not being driven.
Has anyone had this issue or used the shut off switch?

Mon Jul 28, 2025 9:47 am

I am running a battery switch that is also a combiner from Blue Seas I recall. Very common in the boat industry. It's also come in handy a few times when one of the two batteries died at an inconvenient time.

You can just make it out in this picture I uploaded long ago. It is the red thing.

Mon Jul 28, 2025 10:51 am

When I installed a LiFePO4 battery and DC-DC charger earlier this year, I also installed two circuit breakers: one to the DC-DC charger, and one to the auxiliary fuse panel. One press of their respective buttons (which I can access from the driver's seat) and power is cut off to the DC-DC charger and to the solar charge controller, both of which draw power when not in use while the van is sitting in the garage.

Mon Jul 28, 2025 11:00 am

We just got our '85 Westy in mid-June and I'm still learning where everything is and what everything does. The previous owner told me he installed an auxiliary switch for the starter battery so it wouldn't drain and located it on the lower left side of the front passenger seat. In the photo it is shown in the off position. When I want to crank, I rotate it clockwise and any time after starting I can turn the switch off or leave it on which I assume will let the battery charge.

Mon Jul 28, 2025 11:21 am

Serendipity87 wrote: With my current set up, I have to keep my Aux battery on a trickle charge if I don't drive the Van at least once a week...

I don't necessarily want to have an extension cord running out of my house to the Van all the time. Someone mentioned I could install a shut off switch that could be utilized if it's not being driven.
Has anyone had this issue or used the shut off switch?

Draining the battery in a week suggests decent parasitic draw(s). I'd first want to know what parasitic draws there are in the system. A Propex has continuous draw so that may be part or all of your issue.

An ammeter on a multi meter with leads can work but an amp clamp is considerably easier because it doesn't require disconnecting the circuit. I've found this Uni-t 210-e to be a decent meter at a reasonable price.
https://www.amazon.com/UNI-T-Multimeter-Voltmeter-..._1_1_sspa?

There are several ways to disconnect the battery: remove the fuse for the circuit with a parasitic draw, add a cutoff switch, use the battery's BMS to turn off discharge or add a circuit breaker.

Mon Jul 28, 2025 11:51 am

In my 1987 Westy weekender my house battery is a 50Ah agm. I have circuit #3 moved to the house battery fuse panel that I've added. I also have a Boss cereal box sized subwoofer under the driver's seat served by a different fuse on that panel. Because the 50Ah battery is fairly small, it doesn't take much parasitic draw to drag it down in a week or two. I've traced my parasitic draw to the stereo head unit (to keep it's memory for time and station settings), analog dash clock and the subwoofer, which is switched remotely when powering on the head unit, but still draws a few milliamps.

When it is parked outside in summer and not driven frequently, I keep a small solar panel on the dash plugged into the plug intended to serve the silly little dometic fridge that was original (also on its own fuse on the aux panel). It is located in the passenger seat base along the aisle. That keeps the house battery topped up.

When I park it in the garage for winter I pull the fuses from my aux panel that serve circuit #3 and the subwoofer. And, I do give it a trickle charge once a month or so just to top it up. I try not to let it drop below 12.5v or so.

Mon Jul 28, 2025 1:28 pm

You don't need a cut off switch- you need to find the load and fix it. Something is actively drawing power out of your circuits. Your battery should be able to stay well within operating range for maybe 3-5 weeks between any inputs if all you have is standard "Standby" parasitic draws (outputs).

Mon Jul 28, 2025 1:51 pm

I solved this problem on my own rig, after a lot of troubleshooting, when I discovered that the ground had high R. The various sources of otherwise very low amp parasitic draw (head unit, amp, inverter, ...) are now not an issue.

I also have a terminal knife disconnect switch

Tue Jul 29, 2025 9:36 am

I have found the 'electronic' stereo draws about 1 amp in standby mode.

I have the motor/aux bypass switch and leave it in MOTOR position when the parked for a long time to keep the batteries up

In MOTOR position the stereo power is managed correctly by the ignition switch, BUT the stereo 100% powered in the AUX position: which is what you want for camping! FWIW removing the detachable front of the stereo does not drop the draw.

interestingly the 12V 'cigarette' lighter output have new usb-B/C chargers in them, and they do not appreciably draw down the batteries.

I also have a 1.5 Amp maintainer permanently wired to the motor battery, so when plugged in the garage that battery is maintained. The renogy DCDC/MPPT charge controller will top up the lipo from the motor battery if the disconnect is ON (connected position)