Misinterpreting battery volt readings from solar panel
Tony Bev said
12:23 AM Nov 23, 2018
I am unsure if I should say, egg on my face again/some mothers do have them, or do as I say, and not as I do
I was in a free camp for three days with some cloud cover during the day
Each morning just before dawn, I was reading 12.4/12.5 at the el cheapo ciggy socket volt meter, of the house/leisure (2 x 120 AH) AGM batteries I doubled checked this reading by having two ciggy socket volt meters, in a double ciggy socket, about one metre from the batteries, both meters were reading the same
Assuming that I needed more solar, I purchased a portable 160 watt panel, to assist my 300 watt roof solar panel.
Knowing that my new portable solar panel did not have blocking diodes, (I looked, and they were installed as by-pass diodes) Not knowing what my single roof solar panel has, (too heavy for me to remove) I decided to place blocking diodes before my DC/DC charger/regulator, just before the batteries. This is to stop one solar panel from trying to feedback, to the other one
While testing with (three different) multimeters that the blocking diodes were working OK, I found that the el cheapo ciggy socket voltmeters were actually reading approximately 0.21 volts low
This meant to me that the batteries were actually between 12.6 to 12.7 volts, just before dawn With normal use of LED lights and 12 volt compressor fridge, which in my opinion as a layman, 12.6/12.7 is OK for the battery reading
The moral of this story is to point out, that if you suspect that the battery reading is low/high, it may pay to get a reading from a second source
Hope that this information is useful to someone in the future
Aus-Kiwi said
01:00 AM Nov 23, 2018
A good regulator has green, Amber and red LED lights as well as solar input, Battery volts and load . If connected through reg ? When the Amber starts flashing on overcast days . I start the generator for coffees . Thats enough time for the smart 50 amp charger to do its job . 2 or 3 times through the day . So have battery overnight, next morning . Only need to do this when theres been 2 or 3 overcast days . Not very often .
Tony Bev said
01:30 AM Nov 23, 2018
I only have a CTEK 250S Duel (DC/DC 20 amp charger/regulator), which lives under the table seat, with the batteries, AK
It is a fit and forget item, as far as I am concerned
Now that I know, that the el cheapo ciggy socket volt meters are reading 0.21 volts low, I shall not worry, until I see it/them at 12.2/12.3 volts
On engine tick over, my batteries receive the full 20 amp from the DC/DC charger
This suits my present situation, of only having a 12 volt compressor fridge/water pump, requiring 12 volt
I can work around lights by using rechargeable 60 LED work lights
There is nothing else that is 12 volt critical, which I can not do without
Aus-Kiwi said
11:32 AM Dec 25, 2018
Yep . Our build in sound insulated generator is much quieter than vehicle engine running . Not all generators are DC3s. Lol Although 6.5 turbo diesel with 4 exhaust ??
Bagmaker said
10:26 AM Dec 27, 2018
whats really going to blow you, Tony, is that your voltage is not a very good indicator as to the state of charge.
Although voltage can eventually indicate how full a battery is, its a pretty useless gauge when you have regular intermittant loads (fridge) and varied inputs.
Terryt said
07:57 PM Dec 28, 2018
Tony is reading just before dawn. ie no solar input. I often do the same. In my case if the fridge is running the voltage drops by .01 of a volt. I think it gives a pretty good idea of state of charge. Once the sun comes up it is a whole different kettle of fish
oldtrack123 said
08:32 PM Dec 28, 2018
Terryt wrote:
Tony is reading just before dawn. ie no solar input. I often do the same. In my case if the fridge is running the voltage drops by .01 of a volt. I think it gives a pretty good idea of state of charge. Once the sun comes up it is a whole different kettle of fish
For all practical purposes ,I agree
T1 Terry said
11:48 AM Dec 30, 2018
Agree fully with the "Test under load" method being the only truly accurate method no matter what chemistry battery is being tested. That also goes for circuit testing as well, but you need to know the correct load to apply to get a meaningful result without damaging the battery or the circuit.
T1 Terry
oldtrack123 said
03:17 PM Dec 30, 2018
T1 Terry wrote:
Agree fully with the "Test under load" method being the only truly accurate method no matter what chemistry battery is being tested. That also goes for circuit testing as well, but you need to know the correct load to apply to get a meaningful result without damaging the battery or the circuit.
T1 Terry
It is not really that complicated !,
It is the the voltage drop under actual working conditions that is the concern .
No point in doing the test with any more or less load!
The best load to test at ,is the actual max load that could be on the circuit & therefore easy to do [arrange]
No damage can be done unless the system is poorly designed[ fuses in excess of cable current rating]
The important thing when testing , is to include the voltage drop in both pos & neg. of that circuit[ where to take the readings from]
Then, if the voltage drop is excessive, to test at various points [connections] back towards the source to find the individual locations of lost voltage
[again ensuring you are reading the voltage of both pos & neg of that circuit at that point]
However , the battery test should be done directly onto the battery posts[ not the connecting lugs]
-- Edited by oldtrack123 on Sunday 30th of December 2018 03:29:57 PM
T1 Terry said
04:56 PM Dec 30, 2018
oldtrack123 wrote:
T1 Terry wrote:
Agree fully with the "Test under load" method being the only truly accurate method no matter what chemistry battery is being tested. That also goes for circuit testing as well, but you need to know the correct load to apply to get a meaningful result without damaging the battery or the circuit.
T1 Terry
It is not really that complicated !,
It is the the voltage drop under actual working conditions that is the concern .
No point in doing the test with any more or less load!
The best load to test at ,is the actual max load that could be on the circuit & therefore easy to do [arrange]
No damage can be done unless the system is poorly designed[ fuses in excess of cable current rating]
The important thing when testing , is to include the voltage drop in both pos & neg. of that circuit[ where to take the readings from]
Then, if the voltage drop is excessive, to test at various points [connections] back towards the source to find the individual locations of lost voltage
[again ensuring you are reading the voltage of both pos & neg of that circuit at that point]
However , the battery test should be done directly onto the battery posts[ not the connecting lugs]
-- Edited by oldtrack123 on Sunday 30th of December 2018 03:29:57 PM
It does become complicated when computer control comes into the picture when circuit testing, hence the warning.
Hope the New Yr is kind to you Peter
T1 Terry
oldtrack123 said
09:57 PM Dec 30, 2018
T1 Terry wrote:
oldtrack123 wrote:
T1 Terry wrote:
Agree fully with the "Test under load" method being the only truly accurate method no matter what chemistry battery is being tested. That also goes for circuit testing as well, but you need to know the correct load to apply to get a meaningful result without damaging the battery or the circuit.
T1 Terry
It is not really that complicated !,
It is the the voltage drop under actual working conditions that is the concern .
No point in doing the test with any more or less load!
The best load to test at ,is the actual max load that could be on the circuit & therefore easy to do [arrange]
No damage can be done unless the system is poorly designed[ fuses in excess of cable current rating]
The important thing when testing , is to include the voltage drop in both pos & neg. of that circuit[ where to take the readings from]
Then, if the voltage drop is excessive, to test at various points [connections] back towards the source to find the individual locations of lost voltage
[again ensuring you are reading the voltage of both pos & neg of that circuit at that point]
However , the battery test should be done directly onto the battery posts[ not the connecting lugs]
-- Edited by oldtrack123 on Sunday 30th of December 2018 03:29:57 PM
It does become complicated when computer control comes into the picture when circuit testing, hence the warning.
Hope the New Yr is kind to you Peter
T1 Terry
Happy new year to you & yours too
I must be slipping
I did not know that Google Home had got into the van & motor home electrics industry ,only thought that Computer technology applied to vehicle management systems.
Unless you class simple electronics technology as computer control???
T1 Terry said
03:31 PM Dec 31, 2018
:lol: Once you add IC's and microprocessors into a control circuits the whole game changes from the robust "good old days" Check out the inside of any of the newer Jayco, Avida and so on master control systems that run all the touch panel light switches and slideouts and bed slides as well as the inter battery connections and charging links and ignition lock outs and ....... the list goes on. They have a fuse panel and assorted auto reset circuit breakers fitted, but the smoke still gets out if anything gets over loaded. The common multi meter will fry a whole lot of things these days, so someone sticking a test light across the wrong wires creates havoc inside the magic box of tricks.
I've had a few magic boxes handed to me to see if I could put the smoke back in. After you spend a few hrs resoldering circuit boards and replacing components you need a magnifying glass to see the legs, you gain a respect for the old "gently as she goes" when testing anything, so best the know the particular circuits load limits or understand your limits when it comes to knowing what you don't know and leaving it to someone who does.
T1 Terry
oldtrack123 said
07:27 PM Dec 31, 2018
T1 Terry wrote:
:lol: Once you add IC's and microprocessors into a control circuits the whole game changes from the robust "good old days" Check out the inside of any of the newer Jayco, Avida and so on master control systems that run all the touch panel light switches and slideouts and bed slides as well as the inter battery connections and charging links and ignition lock outs and ....... the list goes on. They have a fuse panel and assorted auto reset circuit breakers fitted, but the smoke still gets out if anything gets over loaded. The common multi meter will fry a whole lot of things these days, so someone sticking a test light across the wrong wires creates havoc inside the magic box of tricks. I've had a few magic boxes handed to me to see if I could put the smoke back in. After you spend a few hrs resoldering circuit boards and replacing components you need a magnifying glass to see the legs, you gain a respect for the old "gently as she goes" when testing anything, so best the know the particular circuits load limits or understand your limits when it comes to knowing what you don't know and leaving it to someone who does.
T1 Terry
Thanks for that update Terry
All I can say is the world is going technology crazy
They would be great vans provided you hung around close to the big cities & Cps, but God help anyone who has one & wants to go bush
Yes, I am well aware of the care required when working with electronics & that you should not slap any old test light , voltmeter or ohmmeter on the control circuits. [that has applied for a looong time]
You seem to forget that was my field
T1 Terry said
04:17 PM Jan 1, 2019
Hi Peter, that bit about the multimeter and test light was for those reading along on this thread to realise the problems they could create for themselves if they weren't real careful. I mentioned what was in these magic boxes because I knew you would identify the problems immediately and the need for anyone to be very careful about how they fault tested circuitry. I've even had timer boards we use as part of our BMS control where a test light or standard multimeter was used to measure the output voltage that drives the solid state relays. Even though these timer boards have 10 amp mechanical relays, the circuit board tracks fail at anything more than a 1 amp load. To make it worse, this undersize circuit board track is underneath that 10 amp mini relay, so you can't see it, Chinese circuit board design and engineering at its usual level.
T1 Terry
oldtrack123 said
11:18 PM Jan 1, 2019
T1 Terry wrote:
Hi Peter, that bit about the multimeter and test light was for those reading along on this thread to realise the problems they could create for themselves if they weren't real careful. I mentioned what was in these magic boxes because I knew you would identify the problems immediately and the need for anyone to be very careful about how they fault tested circuitry. I've even had timer boards we use as part of our BMS control where a test light or standard multimeter was used to measure the output voltage that drives the solid state relays. Even though these timer boards have 10 amp mechanical relays, the circuit board tracks fail at anything more than a 1 amp load. To make it worse, this undersize circuit board track is underneath that 10 amp mini relay, so you can't see it, Chinese circuit board design and engineering at its usual level.
T1 Terry
Hi Terry
Great , we have found some more points that we agree on I was using high impedance meters for testing ,donkeys years ago. Fluke being about the only compact ones then available. or, as I also had ,a calibrated oscilloscope. for those instantaneous readings.
The Fluke still going well ,but the oscilloscope is in the shed, had it days
But what are your thoughts on the craze to have so much unnecessary electronics In things like vans & motor homes ,for those who go off the beaten track.?
May be OK for the cp to cp jumpers in or near major towns, but not so ok if some thing goes wrong at the back of Wop Wop
-- Edited by oldtrack123 on Tuesday 1st of January 2019 11:32:56 PM
T1 Terry said
12:14 PM Jan 2, 2019
I was using a Fluke meter and a dual trace data logging CRO back in the early workshop day, roughly '86 I think, and earned a reputation around other mechanical workshops that I was the person to sublet anything that was computer equipped if it had any issues more than plugs and leads would fix. I guess I just carried that through to today. No need to use the CRO any more because I don't need to run cars up on the dyno to record faults under load, but using good multimeters has held through to today.
As far as the electronics in RV's these days, we are only in the early stages with Bluetooth control linked to the smart phone. What worries me is when it changes to linked to the cloud so the manufacturer can monitor the use pattern and push down updates. Trying to diagnose an issue that has only just turned up when they got back close to civilisation just adds another possible cause, a bad patch pushed through or because the contact was intermittent then only half an update done and the whole thing goes into disarray caused by system glitches. Anything built that interfaces with other programs for crossed data feeds and control will need to have program updates specific to the combination of other software used in that particular outfit ..... a nightmare.
After watching a brilliant Crane management system still in its infancy hit the wall because Cat changed their programming for the engine management and refused to allow access to any one not directly within the Cat empire, I can see the writing on the wall as far as what is coming and just around the corner. We already have a few problems arise with the Victron BMV that links to the customers smart phone. Victron in their infinite wisdom allowed for reprogramming via the same smart phone, yet no way to lock the customer out of it ... marvellous, simply marvellous, can you imagine the chaos when other manufacturers follow suit and some bored grey nomad decides to play with the setting "just to see what happens?"
T1 Terry
oldtrack123 said
12:44 PM Jan 2, 2019
Hi Terry
It seems we have much in common, but sadly ,my memory seems to be fading over the last 6 months
I am unsure if I should say, egg on my face again/some mothers do have them, or do as I say, and not as I do
I was in a free camp for three days with some cloud cover during the day
Each morning just before dawn, I was reading 12.4/12.5 at the el cheapo ciggy socket volt meter, of the house/leisure (2 x 120 AH) AGM batteries
I doubled checked this reading by having two ciggy socket volt meters, in a double ciggy socket, about one metre from the batteries, both meters were reading the same
Assuming that I needed more solar, I purchased a portable 160 watt panel, to assist my 300 watt roof solar panel.
Knowing that my new portable solar panel did not have blocking diodes, (I looked, and they were installed as by-pass diodes)
Not knowing what my single roof solar panel has, (too heavy for me to remove)
I decided to place blocking diodes before my DC/DC charger/regulator, just before the batteries.
This is to stop one solar panel from trying to feedback, to the other one
While testing with (three different) multimeters that the blocking diodes were working OK, I found that the el cheapo ciggy socket voltmeters were actually reading approximately 0.21 volts low
This meant to me that the batteries were actually between 12.6 to 12.7 volts, just before dawn
With normal use of LED lights and 12 volt compressor fridge, which in my opinion as a layman, 12.6/12.7 is OK for the battery reading
The moral of this story is to point out, that if you suspect that the battery reading is low/high, it may pay to get a reading from a second source
Hope that this information is useful to someone in the future
It is a fit and forget item, as far as I am concerned
Now that I know, that the el cheapo ciggy socket volt meters are reading 0.21 volts low, I shall not worry, until I see it/them at 12.2/12.3 volts
On engine tick over, my batteries receive the full 20 amp from the DC/DC charger
This suits my present situation, of only having a 12 volt compressor fridge/water pump, requiring 12 volt
I can work around lights by using rechargeable 60 LED work lights
There is nothing else that is 12 volt critical, which I can not do without
Although voltage can eventually indicate how full a battery is, its a pretty useless gauge when you have regular intermittant loads (fridge) and varied inputs.
For all practical purposes ,I agree
T1 Terry
It is not really that complicated !,
It is the the voltage drop under actual working conditions that is the concern .
No point in doing the test with any more or less load!
The best load to test at ,is the actual max load that could be on the circuit & therefore easy to do [arrange]
No damage can be done unless the system is poorly designed[ fuses in excess of cable current rating]
The important thing when testing , is to include the voltage drop in both pos & neg. of that circuit[ where to take the readings from]
Then, if the voltage drop is excessive, to test at various points [connections] back towards the source to find the individual locations of lost voltage
[again ensuring you are reading the voltage of both pos & neg of that circuit at that point]
However , the battery test should be done directly onto the battery posts[ not the connecting lugs]
-- Edited by oldtrack123 on Sunday 30th of December 2018 03:29:57 PM
It does become complicated when computer control comes into the picture when circuit testing, hence the warning.
Hope the New Yr is kind to you Peter
T1 Terry
Happy new year to you & yours too
I must be slipping
I did not know that Google Home had got into the van & motor home electrics industry ,only thought that Computer technology applied to vehicle management systems.
Unless you class simple electronics technology as computer control???
I've had a few magic boxes handed to me to see if I could put the smoke back in. After you spend a few hrs resoldering circuit boards and replacing components you need a magnifying glass to see the legs, you gain a respect for the old "gently as she goes" when testing anything, so best the know the particular circuits load limits or understand your limits when it comes to knowing what you don't know and leaving it to someone who does.
T1 Terry
Thanks for that update Terry
All I can say is the world is going technology crazy
They would be great vans provided you hung around close to the big cities & Cps, but God help anyone who has one & wants to go bush
Yes, I am well aware of the care required when working with electronics & that you should not slap any old test light , voltmeter or ohmmeter on the control circuits. [that has applied for a looong time]
You seem to forget that was my field
Hi Peter, that bit about the multimeter and test light was for those reading along on this thread to realise the problems they could create for themselves if they weren't real careful. I mentioned what was in these magic boxes because I knew you would identify the problems immediately and the need for anyone to be very careful about how they fault tested circuitry. I've even had timer boards we use as part of our BMS control where a test light or standard multimeter was used to measure the output voltage that drives the solid state relays. Even though these timer boards have 10 amp mechanical relays, the circuit board tracks fail at anything more than a 1 amp load. To make it worse, this undersize circuit board track is underneath that 10 amp mini relay, so you can't see it, Chinese circuit board design and engineering at its usual level.
T1 Terry
Hi Terry
Great , we have found some more points that we agree on
I was using high impedance meters for testing ,donkeys years ago. Fluke being about the only compact ones then available. or, as I also had ,a calibrated oscilloscope. for those instantaneous readings.
The Fluke still going well ,but the oscilloscope is in the shed, had it days
But what are your thoughts on the craze to have so much unnecessary electronics In things like vans & motor homes ,for those who go off the beaten track.?
May be OK for the cp to cp jumpers in or near major towns, but not so ok if some thing goes wrong at the back of Wop Wop
-- Edited by oldtrack123 on Tuesday 1st of January 2019 11:32:56 PM
As far as the electronics in RV's these days, we are only in the early stages with Bluetooth control linked to the smart phone. What worries me is when it changes to linked to the cloud so the manufacturer can monitor the use pattern and push down updates. Trying to diagnose an issue that has only just turned up when they got back close to civilisation just adds another possible cause, a bad patch pushed through or because the contact was intermittent then only half an update done and the whole thing goes into disarray caused by system glitches. Anything built that interfaces with other programs for crossed data feeds and control will need to have program updates specific to the combination of other software used in that particular outfit ..... a nightmare.
After watching a brilliant Crane management system still in its infancy hit the wall because Cat changed their programming for the engine management and refused to allow access to any one not directly within the Cat empire, I can see the writing on the wall as far as what is coming and just around the corner. We already have a few problems arise with the Victron BMV that links to the customers smart phone. Victron in their infinite wisdom allowed for reprogramming via the same smart phone, yet no way to lock the customer out of it ... marvellous, simply marvellous, can you imagine the chaos when other manufacturers follow suit and some bored grey nomad decides to play with the setting "just to see what happens?"
T1 Terry
Hi Terry
It seems we have much in common, but sadly ,my memory seems to be fading over the last 6 months