Just a quick question and answer, I hope!! I put a multi-meter on my caravan 12 volt system and found it has a reading of 13.75 volts. I'm currently plugged into 240v and the batteries are hooked up to a smart charger. Batteries are AGM GEL. Should my lighting system, TV, etc be running at 13.75 volts and if not how do I rectify the problem (If there is one) On a side note I also checked my solar panels at the solar-controller and found they have an input of 20.4 volts which surprised me as it was a very overcast and rainy day. I would appreciated your comments.
I am not an Electrician, just going by my own observations
It is normal to see anywhere between 12.8 and about 14.4 volts, when the leisure battery is being charged
12 volt items such as TV/Radio/Fan etc, will accept whatever the 12 volt battery sends to it
As an example, if you put an el cheapo volt meter, in your ciggy socket, you will normally see around 14 volts, when the engine starts This voltage will run any 12 volt item, without any problems
Edit to say Batteries are normally AGM, or GEL, some salesmen call them AGM GELL They are made different, and their maximum charging voltage is slightly different
Edit again, (I have just returned from a nice day out), and perhaps a bit tired The solar reading of 20 volts before the regulator is correct, the regulator then cuts the voltage down, to what the battery wants One word of warning, it is possible for the solar regulator to think the battery/s are full when it detects the voltage of the 240 volt charger, and visa versa This scenario could mean that the battery/s are not being fully charged
I always disconnect the solar, if/when I am charging with 240 volt, and/or visa versa, depending on what I think is the best for the batteries
-- Edited by Tony Bev on Monday 4th of December 2017 11:32:24 PM
-- Edited by Tony Bev on Monday 4th of December 2017 11:41:18 PM
Yes 12v is the accepted voltage level . Even if you checked AC volts . Depending how far your away from sub station voltage varies there too !! ( 210 to 250v ) Mind you 12v DC doesnât give much to play with ! Less forgiving .DC Cable size is critical !! DC around . 12.5 to 14.2 v . Check at appliance it will be lower in most cases .
-- Edited by Aus-Kiwi on Tuesday 5th of December 2017 12:22:10 PM
Just been 3 days looking at this myself. Trying to find what goes where & what voltages & currents flow thru the van.
House battery is nominally 12V. The 12V control unit (Omegalec) in my van is basically a 30A 12V regulated power supply (240V mains) that will top the battery up to 12.6V on my panel. Voltmeter shows 12.8V. 12.8V is regarded as 100% charge in some circles whilst 12.2V is considered 50% charged. When connected to Solar or my ute, it will go to 14.2V on my panel. Voltmeter shows 14.4V. Drops to 13.4 - 13.8V quickly though. Ute supplies 14.6V, solar up to 14.4V.
A lead acid cell is nominally 2V (6 cells for a 12V battery). However they do range from 1.8V (poor charge) to 2.27V (good charge). Hence 6 x 2.27V = 13.62V for a good battery in full charge).
-- Edited by RustyD on Tuesday 5th of December 2017 01:52:47 PM
Hi
Rusty D
The meter is not entirely correct .
50% = 12.2v relates closer to **some ** flooded lead acid types . More typical of the old school RV industry .
50% = 12.05 v is more common for AGM
As usual check with your battery maker , voltage State of Charge sheet .
I am not an electrician, so do not quote me on this
I am led to believe that the first cells were measured at 2 volt, therefore 6 x 2 volts = 12 volts, so that is how they wrote it up
They also wrote that the flow of current was from positive to negative
Many years later they found that the current actually goes from negative to positive, but as the books were already written, they did not change the words
Perhaps an Electrician, can explain it better than I can
12 volt batteries are actually 12.8 volts AGMs have a max charge of 14.8, GELS and wet cells around 14.4. Once the end of the absorption stage is indicated (fully charged) the charger will revert to float mode and maintain the battery in a fully charged state. Normally 13.8 volts.
These numbers vary a little depending on who wrote the story!
Joe Jan I'm an electrician not an auto electrician. I'll just explain a bit about voltage. When you try to understand about electricity it is best to compare it to a water system. In a water system you have pressure some times measured as pounds per square inch or kilopascals if you want to talk metric and that water pressure is what pushes the water through the pipes.
In an electrical system the voltage also known as Electromotive force (EMF) is comparable to the pressure in a water system and it is the voltage that pushes the current through the wires and into the battery. Increase the voltage and you will push more current into the battery. Connect the solar panels direct to the battery without a regulator to reduce the voltage and you risk destroying the battery when you are charging a battery (depending on the wattage of the solar panel but I don't want to complicate it) and if you put your multimeter on the terminals while it is charging and switch the battery charger on and off you will see the voltage is higher when the charger is on than when the charger is off. The reason for that is in order to push current into the battery the voltage (which is like pressure) from the charger has to be higher than the voltage pushing back from the battery and as the voltage in the battery increases as it becomes more charged then the current being pushed into the battery is decreased. This is seen more so in the old fashioned chargers, the modern smart chargers are even more sophisticated. The 12volts is a nominal figure the voltage of a charged battery is more and varies slightly depending on what type of battery. Get your multimetre and measure the voltage on a new torch battery and you will see it is more than what it is rated. It is not a good idea to rely just on your multimeter to determine the state of charge on your battery as there is not much difference between fully charged and not charged. OK for a rough idea. There are more sophisticated devices for determining that and some can learn your system by monitoring what current is being put into your battery and what is going out when not on charge and will then let you know how many hours it will last.
I have this on my van https://www.youtube.com/watch?v=0wzINmtLVYQ it connects to your battery and not wiring through the van. I have an app on my phone and it blue tooths to the device. it is a little inconvenient as I have to wait 30 secs to a minute for my phone to connect to the device but I can go to my lounge room wall near the van without going outside and check the battery in the van and I can also check to see that my DC to DC charger is charging from my car when I pull over. There are other devices on the market that do a good job as well.
-- Edited by sandman55 on Thursday 14th of December 2017 12:24:53 AM
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To err is human but to really mess things up, you need a computer.
My take on it is it's not so much a description of the full capacity of what a battery can be charged too as that can vary, it's an indication that it the can run 12volt equipment...
-- Edited by Ron-D on Friday 15th of December 2017 04:39:07 PM
