Author Topic: Can low coach batteries cause the battery disconnect latching relay not to work  (Read 843 times)

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Offline Captpar

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Can low batteries cause the battery diisconnect latching relay not to work , causing loss of 12 volt power?

Offline Captpar

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Additional info for above post. This morning when I tried to retract my jacks to leave rv park they wouldn’t come up. Finally got them up by cycling thru jacks down again then retract with engine running. After unplugging from shore power, I lost all 12 volt and the engine info center said low voltage on batteries. I had problem with latching relay in the past currently on my third in 11 years. Not having a spare , I bypassed the relay and immediately got my 12 volt back. Except for the refrigerator, which is on a GFI plug. About 10 min later I lost the tv in the bedroom and one additional outlet also the breaker popped for the bedroom circuits ( just the two mentioned above) battereries are 7 years old and I was goin g to replace them after this trip. Currently showing charge rate on magnum at 13.1. Currently in rv park on shore power everything works except refrig and two outlets in bedroom. Got refrig working via ext cord to pedestal. Will new batteries make latching relay work if I un bypass it. Thanks for any info.

Offline Brett Wolfe

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Yes, low voltage will cause a relay to not "pull in".

But I am confused by your discussion of 12 VDC and GFI's.  GFI's are 120 VAC, not 12 VDC.

When on shore power, your inverter/charger should have you in the 13.2 VDC range (float voltage).  Should be no problem IF the house bank is the source for signal to the relay.

But, if chassis battery is source and voltage is very low, certainly, that could be the issue.

SO, with a digital voltmeter, what are your readings at the chassis battery? house battery?

Offline Captpar

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Don’t have a voltage meter  am hunkered down on the gulf coast to ride out the storm.didnt think chassis batteries had anything to do on the house side. Do you think bypassing the latching solenoid caused the loss of  the 2 outlets and GFI?

Offline Captpar

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One more question what is any are the ramifications of leaving the latching relay in the bypass position. Tired of changing these out .

Offline pfhays

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I assume when you talk about low voltage on batteries you are talking about your house batteries and not the chassis batteries since you can start the rv.

If you had 12 volt power before the batteries died then the latching relay will not change status even if the battery goes dead.  Latching relays toggle between conducting and not conducting when the switch is toggled and power is applied to the coil of the solenoid.  If you have low voltage then it may not be possible to change the state of the latching relay so if the solenoid was previously in the off position to disconnect the batteries then you wouldn't be able to activate the solenoid and connect the batteries.

Your latching relay is working with a 12 volt system and has nothing to do with the 120 volt system on your rig.

When you unplugged from shore power and lost 12 volts with the engine running which batteries are low, the house batteries or the chassis batteries.

You really should invest in a 12 volt test light and a low cost digital volt-ohm meter so you can trouble shoot systems like this one.  Make a trip to Harbor Freight.  For about $10 you can get both of these items.

Someone might come on line that knows about the Magnum inverters.  There my be a problem with it as far as charging the batteries or passing 120 volts through to your outlets.






Offline Captpar

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House batteries are at 13.1 float charge is at 13.3 batteries are toast .will replace when I get home as well as the latch relay which I ordered. Also will replace chassis batteries. Thanks for all the info.

Offline Captpar

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UPDATE. short on 120 side was caused by a burnt quick disconnect on a electrical line under the refrigerator. Fixed that ,reset breaker all outlets working now. Installed new latching relay all 12 volt good. Again thanks for the assistance.