Battery banks - possible short?

Question

Hello! I'm looking at getting something to keep the engine battery charged, since apparently the older RV's like mine (30' 1995 Winnebago Adventurer with a Chevy engine) have a drain on them. I found this, which seems like it might do the "trick" (lol) - http://lslproducts.net/TLSPage.html.

I'm worried, though, because using my multimeter - it read zero resistance between the positive terminal on the engine battery and the positive terminal on the house battery. That shouldn't be, right? Of course the negative terminals show zero resistance, because it's a common ground. Is there somewhere in particular that I should look for a short? Still - they're both reading separate voltages. The engine's really low right now (reason for the charger), but the house, which charges through shore power, is tip-top.

Suggestions? Thanks!

Johnny

enblethen · Answer

Reverse the leads! It is a diode unit.

wa8yxm · Answer

There is resistance but it is too small for your meter to measure.

When you are measuring positive to positive.. The entire system is still there.. current can easily flow. I'd not worry about it and do not test that way

To test With the engine off and shore power on test each terminal for VOLTAGE reference to ground. If the chassis (Engine) is 12.x and the house 13.xc YOu can use the Trick-L-Start.

drewe · Answer

Are you trying to measure resistance in the circuit? That doesn't work; the voltages present confuse the meter. Many multimeters can be damaged if you apply too much voltage to them in resistance mode--and too much isn't always a huge amount. Some good ones have quite robust input circuitry, and there has been at least once that I've been very thankful to have one in that category (a Fluke 73).

As others have said, even out of circuit it's generally troublesome to measure resistance of active semiconductor devices. As the term semiconductor implies, they conduct or not based on comparatively complex relationships, and generally do not act as plain resistors.

Since you see different voltages on either side, it's not shorted. You should be good to go.

mrwizard · Answer

what batteryhouse or engine/chassisthe chevy notorious for parasitic power drain in the start circuitat the starter relay/solenoid if measuring resistance between ciruitsdisconnect the batteries, all batteries, just measure the wiringlike stated above, easier to compare voltages on each side to grounda short between the two systems house and chasiss will show equal voltageat rest, with loads, and when chargingdifferent voltages, when charging from shore or with house loads on (lights and fans) (should be no change in voltage on the engine side) means no short

1995brave · Answer

Since this is a 95 Chevy it has the TBI system which has a parasitic draw when turned off.  The chassis and coach batteries are separated by a solenoid.  You can download the wiring and other diagrams for your RV from the Winnebago website.

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Battery banks - possible short?

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