volt meter readings

David Olson

David Olson

Novice
Can anyone tell me what the volt meter should read for the battery level? Like what is 25% discharge, 50% discharge, and 75% discharge.
I have the AGM battery upgrade but can't remember what volt meter readings are good and bad other than it should never read more than 15 volts. I believe that means your charge controller is no longer working.
I thought I had seen it on here some place but can't find it.
Thanks for any help.
 
On the back of my volt meter is says:

12.6 -> 100%
12.4 -> 12.6 75%
Can't remember the 50% and 25% values but do know that it should not drop below 12 if I can help it.
 
Mick was shocked that I knew 11.6 was about 20%, and sent me this chart to share. It will be handy to have!

voltagechart.jpg
 
I'm curious how to "use" this data, short of timing my prayers accordingly.

If your meter is creeping down toward 60% do you (a) hook the TD to the TV and run the TV for an hour?; (b) increase the temp on the fridge? (3) stop using lights/radio/fan.

Do any of these really make a difference? (obviously it would make a difference if you could remove ALL drains on the battery)

Any other suggestions?

(yes, hook up the solar panels, etc.)

-Al
 
Here is what I experienced this summer when my car wasn't charging my trailer while driving (turns out there was a short in my wiring which Mick has fixed since we have been home after speaking with Land Rover about the issue, but I digress).

The drop for 12.7-12.2 seems to happen quicker than any other drop. I am not sure if this has anything to do with the voltage reading higher right after being unplugged and settling into it's actual charge or what, but that drop happens quicker. I have 3 batteries on board, so I usually see this within a day or so. I usually keep my fridge in the galley, and have the temp set to 27, but on my trip with the battery issues I raised the temp to 32, which I wasn't happy with, but it helped with power.

Then I check 2 times a day what my voltage is. I have sat parked for 8 days with no charging on the new batteries, these days I can go 4-5 days depending on temps. The temperature will effect the battery drain as well. I am pretty stingy with my power usage, so the fan stays off until the evening unless I am plugged in, and the fridge is plugged in.

I don't worry about my voltage until I start getting down around 11.6-11.7. Mick tells me to be careful around then because there is a point where the battery can be damaged by going too low. I take the fridge out of the galley at this point and plug into a battery back-up I have or into the car if I am driving. I am usually ok down to 11.4, but it really should be charged before that.

At that point, I either plug in, go for a drive, or just turn the car on for a bit. I struggled with that this summer, but we did the best we could. I made it over a week without charging, and it was a lot of work and stress.

There might be electrical engineers here that can explain it better. I know this stuff only through experience and marriage to an EE. I just try to keep up!
 
Dometic Fridge was Re: volt meter readings

The Dometic CF-35 has a selectable Low Battery cutoff with 3 choices. The manual describes
this "Battery Mode". It is the other SETting along with with the 'desired' temperature.
Press the Set button multiple times until the display shows HI, Med (NEd?) or Lo.
Press + or - buttons to change it. After a bit the panel returns to displaying the actual temp.

Mode__ Off below Re/Start above
Hi______ 11.8v _____ 12.6v ___ Only starts if full or charging (safest shut-off if in car)
Med____ 11.4v _____ 12.2v ___ can use 90% but safe for CI battery (charge soon/24hr)
Lo_____ 10.1v ! ____ 11.1v ___ uses 100% but can damage battery (severely shorten life)

Note: low batteries are also more prone to freeze at low temps.

The High setting is the one most likely to lose a quart of milk by shut-down occasionally.
Watch for the flashing power indicator when you walk by.

Be watchful if you unplug the DC cord below 75% charged. High and even Medium mode
may not restart when plugged back in and the power indicator will flash instead.
Who ME unplug to reroute the cord? ha ha...

If Mode was set to High and stopped with battery at 11.8v, you might have to set it to Low to
get it to re-start so you can keep the milk & steak cold until you can recharge (in AM) or Ice.
Try to re-set it to Medium once it is running. Otherwise, watch the voltage and don't leave it
indefinitely on Low. A cooler full of food is not worth the price of an AGM battery.

Obviously keeping the lid closed AMAP will help the battery.

Note: don't depend on the Xenon cabin/kitchen lights to show a low battery.
Mine seemed to look OK when the battery was down at 10%.

Mark - BSEE
 
Sarah, if I didn't know any better I'd think you were the engineer! I need to go back to school to understand all of this! Lots to learn!
 
Well, I had about 2 weeks of stress over this on our big trip this summer, so I had to learn on the fly. When I am thrown in, I can sometimes pick some stuff up. The numbers mean certain things to me, but everything else goes right over me. You should see all of the things Mick builds. He is a master at this stuff from chicken feeders with remote controls to raise and lower them to keep rats out, cranes that work for the Lad, special water tables with spigots and pumps for the preschool nature garden, full on control modules for the lad, and now he is working on conveyor belts, because the Legos need to make it into the dump truck somehow. He is always up to something, but it keeps him out of trouble...mostly. Not sure what his desk looks like, but his work bench is a bit of mess since he is in the middle of a project. He cleans between them! :)
 
I admire your really fun family. You seem like an awesome Mom with your genius husband and the little Lad is a joy. I love hearing about the projects and your adventures with Laddy traveling. Looking forward to seeing you all again.
 
Thanks so much Patty! We just do our best and are hoping for a good outcome when that kid turns into an adult. He is a pretty good kid so far...trying to make sure that sticks! Plus, having fun is fun, so we try to do that a lot! :)

Hopefully we will see you at the NWRU in July, if not sooner!
 
Mick'nSarah said:
Thanks so much Patty! We just do our best and are hoping for a good outcome when that kid turns into an adult. He is a pretty good kid so far...trying to make sure that sticks! Plus, having fun is fun, so we try to do that a lot! :)

Hopefully we will see you at the NWRU in July, if not sooner!
Click to expand...

I too think it is awesome you hit the road with Jr. Those are lifetime memories being created for both of you. I wish I would have done something like that when mine were younger. So, will just have to start that with the grand kids.

Enjoy because they grow up really fast.
 
You're welcome Sarah. I'm sure the time spent will pay big dividends in the future. I spent a lot of time enjoying my girls although when they turned into teenagers I just prayed every night for them to grow up and move out of my house. They turned out alright and are good honest people.
 
Jay_n_Valerie said:
I too think it is awesome you hit the road with Jr. Those are lifetime memories being created for both of you. I wish I would have done something like that when mine were younger. So, will just have to start that with the grand kids.

Enjoy because they grow up really fast.
Click to expand...

Thanks J&V. He has already grown up fast. He just hit 4'2, will be asking for his 2 front teeth for Xmas, and is currently trying to work out how the voting works and was telling me about climate change the other day. These kids are crazy smart and what has me baffled is I feel like we brought him home from the hospital a month ago. I can't believe it has been 7 years, and you would think it would seem longer since I have been awake for most of that time! Wasn't blessed with a good sleeper, but we kept him anyway. He is pretty darn cute, and as sweet as they come.

Patty, I have a feeling the teenage years will be hard on me.
 
I may have a problem.
When I plug into shore power, my volt meter reads 14.1 Volts When I plug in my solar (110 watts) the volt meter only reads 12.5 volts. I would think it should be reading at least 13.1 in full sun.
The light on my solar plug comes on as soon as the panel gets light, without being plugged into the camper. The light on my charge controller is on which means it is getting solar power.
Does anybody have any idea what may be going on?
 
How long is the wiring from the solar panel to the volt meter, and what gauge wire is being used? Long run, small gauge (high number) wire results in significant voltage drop.

Do you have the solar option from Camp Inn or are you using a panel system complete with their charge controller mounted to the panel? A 12V solar panel can put out up to 18 volts and the controller, which is designed to protect the battery, will reduce to a lower voltage (about 14.4 volts).

If the charge controller is attached to the back of the panel (not the Camp Inn option), the reduced voltage from the controller will incur further voltage loss in the wiring between the controller and volt meter, which is near the battery. The Camp Inn option puts the charge controller near the battery, minimizing the length of voltage drop between the controller and battery. Note voltage loss will occur in the long wire run whether driven by 18 volts or 14.4 volts, which is why heavy gauge is needed for long runs. A small voltage loss in wiring between the 18 volt source and inlet side of the controller, means the controller will deliver a decent voltage out. However, if the voltage loss occurs on the long run from the outlet side of the controller mounted on the back of the panel, the battery will see less voltage.

If this isn't the problem, check to make sure all the wiring connections and/or solder joints are good. If any of the connections or joints are warm to the touch (check when solar panel is charging the system), this could be an indication of a trouble spot (warmer than elsewhere along the total length).

Finally, current flows from higher voltage to lower voltage, like a river flows from higher elevation to lower elevation. The other important measurement in charging the battery is the amount of current flowing into the battery (amperage). The voltage meter does not inform you how much amperage is flowing into the battery; you need an ammeter to provide that information.
 
I think I got it figure out. I do have the Camp Inn solar option. First I found that I had a blown fuse which I am sure I caused. I wired up some new MC4 cable and think I got some wires crossed. I am only running 10 feet of cable with 14 Gauge but I did have to step the wire down to wire into the plug for the camper. I did not know there was a fuse by itself for the solar along side the battery. Upon replacing the blown fuse my volt meter is now reading 12.6 with my panel sitting inside my garage floor by the window. A direct reading off the battery gives me the same reading.
I recently went back to a rigid panel because my flexible panel was not giving me the results I wanted. Very very portable but to hard to position for the sun. Just waiting for a sunny day now to put it in full sun to see what I get. We just sold our motorcycle so now the camper is able to be in our house garage so I can keep the solar panel plugged in sitting by the window and no more having to use electricity to keep the battery topped off. Thanks for your help.
 
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