Power help - battery cables are hot

[RVFunlovers]

I lost power to the coach when not home and drained the house batteries down to the cutoff.

Started the coach and let the engine run about 20 minutes. Vegatouch rebooted.

I then applied AC power to coach. Inverted fired up and started charging.
After about 10 minutes I got a fault that say inverter fault - battery high temp.

I opened the coach basement doors but could not get the inverter to stay on.

When the inverter cuts out I loose inverted outlets as well not just charging.

I felt the inverter and it was not hot. I unplugged the BTS cable and the inverted started asap. It has been charging about 30 minutes.

I opened the batter compartment. The batteries are not hot. They are about 85 to 90 which is the temperature of the MH basement.

The cables are hot. They read 120 to 140 depending on where I point the laser.

I don’t feel this is normal. But I don’t know. My sense is my batteries are bad but they have been holding just fine until this event. I don’t know how long power was out.

Any power advice? Shut down the charger? Plug up BTS cable and hope the batteries will charge if I urn off all loads off. Maybe the inverter will cycle. I suspect the sensor is right near a terminal or cable and that is what is shutting down the inverter.

The battery box is not hot. The cable are hot.

I fear I have an issue and I have bypassed a safety feature.

[wolfe10]

Hot anything, including cables means RESISTANCE. Find the source and eliminate it.


Could be connection to battery terminal, could be bad wire to terminal connection, could be copper wire that has turned to copper OXIDE (green).

[RVFunlovers]

Seems like all the terminal and cables are about the same 120 to 135. At least all the cables or terminal I can get my laser to.

I shut down my fridge, outdoor fridge, and wine fridge. Inverter is humming at 17 amps now. The inverter is warm not hot. The fans are running.

House battery voltage is up to 13V.

My hope is to get the batteries recharged then barely use them on the next trip. Maybe I will get all new batteries and have all the cables checked. These are the original batteries but they are not 3 years old yet.

Definitely sleeping in the house not the MH tonight and turning everything off unless I can watch it.

[palehorse89]

I'm going to say they are hot due to the high amp charge rate to the dead batteries.............now that some time has past since you posted Hal, are the batteries getting charged back up some and are the cable's not as warm?

[RVFunlovers]

Volts are up to 13.3
Cables are still hot. In the 110 to 140 range depending on where I put the laser. The cable from the inverter cutoff switch to the batteries is the hottest. Maybe because tt has a good bend in it.

I checked the cables where they leave the inverter. Red is 110 and the black is 115.

For now, I am watching closely but letting the batteries recharge.

I kind of wish the Magnum / Inverter charger failed with allowing AC pass through to the fridge and outlets but that is not the way it works. When the Magnum shuts down the charging because of high BTS it is blocking the pass through loads as well so anything in the right hand AC power panel (inverted) is off even when connected to shore power.

[twinboat]

If your showing a draw of 17 amps AC, the charger outputting max amps DC to the very weak batteries.

You may want to back off on the charging amps to keep things cooler until the volts get up to 14.6 and the charger goes to absorb mode. It's going to take a few hours.

[RVFunlovers]

Batteries are up to 13.5

I don’t see a way to drop the current down from the vegatouch to charge slower.

[Pwdr Extreme]

Originally Posted by RVFunlovers

Batteries are up to 13.5

I don’t see a way to drop the current down from the vegatouch to charge slower.

You can tell the Vega touch your plugged into 10 amp shore power or something similar, it will cut the amperage output of the inverter.

[Solo_RV_Guy]

Use an outboard charger (automotive charger). Power off the inverter. You may want to follow the inverter manufacturer's instructions for disconnecting the inverter and charge the batteries separately.


The deep discharge of your batteries is why the high current draw and heat. I'm actually a little surprised that the system attempted to charge the batteries.

[RVFunlovers]

I found a way to adjust the inverter amps down.

Before I made the change the system reached the correct voltage or timed out and switched from absorb to float.

Looking good now.

I need to figure out if it is normal to have cables or terminals at 120 ~ 140 degrees. I don’t think so. I am going to baby my batteries on our next trip. We normally do anyway. I should have had auto gen start set so losing power would not have caused a deep discharge.

[Fergtiffin]

I would take the time to pull the batteries and check them. If you have a bad battery it very well could cause over charging of the others. I toasted 4 new batteries a little over a month ago. Definitely do not unhook BTS

[SafariBen]

120-140 is not that hot if it's hot outside, the cables don't cool off very fast, and a big load for a while could do that. I'd be most concerned that the heat is coming from the connections and not the length of the cable, so I'd check the next time you run the batteries low, after ten minutes, then half hour, then every hour, see where the heat is coming from by what gets hot first. The cables should be sized for 200a for a 2000w inverter, etc. so shouldn't be getting that warm from the charging, but the heat could be coming from connections, even the inverter itself heating up

[palehorse89]

Question Hal, do you ever have the auto gen set? Mine is always on and set up for low battery voltage........so this never happens.
Glad they are charged back up and ya are ready to go.......

[RVFunlovers]

Batteries / inverter are now setting on float like normal. The cables and terminals have no heat. The batteries are just a couple degrees above the basement temperature.

I reconnected BTS cable to the inverter. Heading out on a trip for a couple of weeks today. We plan to use the batteries sparingly.

I am going to see what happens over the next few days.

Cables and terminals were certainly hotter than I think they should have been to recharge the batteries. External temp was in the low 80’s and the system would have not have recharged with the BTS cable on. Limited airflow in the battery box area likely does not help. Once it got hot it was staying hot a while.

Overall I think everything else worked as designed with my power outage. Because I did not have AGS on, the system went down to the low cutoff voltage limit and cutoff. When I reapplied power nothing happened. So I started the coach and ran at high idle. The engine alternator put enough on the house batteries to allow the inverter to kick in. I then shut the coach off. Batteries were getting charged for a few minutes until the BTS lead shut the inverter off. I got that fault on the vegatouch. A few minutes after that the system was a low voltage cutoff again and shut down. I repeated the process again. This time letting the coach run at high idle for an hour. The inverter may have been on a minute or two before the BTS cut it off again.

Next test will be to test my batteries by letting them run the refrigerator and tv for a several hours down to 12.2 or so. Then reapply power and see if the system recovers normally without an overheat condition. I need to go have fun for a couple of weeks before I try that.

From what I saw last night even when the battery voltage was back to 13.x the system kept the amps high and the battery cables and terminals were hot. That makes me think I will overheat with normal battery use and recharge. But I have had normal battery use and recharge before without getting an inverter battery fault.

Question - The battery temp sensor line goes to the back section of my battery box. I cant really see exactly where the sensor is connected without pulling the front batteries out. Is the sensor supposed to be on a battery post, on the side of a battery, or just in the battery box?