would anyone know how to calculate how much 12volt power we would use over night when we arrive at a sight with a full battery load lets say 13 volts on the meter ours is in the cupboard,and the same meter is reading 12 volts in the morning,that means we have used one volt over night right?

thats how I thought it worked simple eh,but on our last trip that 13 volts died on a battery that was only one year old overnight,is there a way to know your exact usage overnight and a way to know your battery is completely full,the volt meter is a bit of a worry,were not big power users and at$400 dollars a battery every year .

Our car charges the battery 12v to 12v charger

we only have an 80w portable solar panel 

there must be a way to figure out battery usage than relying on the volt meter is there ?

Hi Ron

You ask a hard question that sounds easy

Using the voltage to measure the battery capacity is not reliable and needs experience with your own system to work at all. Batteriy voltage goes up when charging and down when being used, so can vary 0.5 V in 10 minutes between the two states easily and much more heavy loaded or charging.  Note that the battery is virtually flat at 12 v under no load but may recover to a higher V if left for a while. Over 14 is needed for full charging too and LA batteries need some time at full voltage to "fill up" completely or will not get properly fully charged.

The best way is a controller which measures the current going in and the current going out to give the best idea. Note you get back less than you put in also. So perhaps you could tell us what you have exactly to charge it and how long you drive.  Also tell us what you usually use each night, for how long and the current they draw so we could see what amp/hours is going in and out.  

Jaahn

 https://www.energymatters.com.au/components/battery-voltage-discharge/

Sorry.
Took it for granted.

The "Consumption", means AMPS, bit.

Leaving the "Voltage" levels on Battery readings.
Modern battery's are usually Ah or cca, for power.

Just take readings of AH consumption. per each item per av, hrs used.
Multiply the items usage.
Look at AH per each battery x battery. etc etc.

Or
Just be like me. Have a rough guess. Set some up.
If battery's too low in morn. MORE panels.

Till I'm floating by 11 .30 or so most morn's.
With trusty Genny to get me out of you know what, hey.


LOOOOooooooVE. My Genny with 40a charger.

Last van.

6.5 mtr. 340 w panels on roof. 2 x 110a AGm inside. 

with an 80w panel on roof of tray which I could link in.

That ran our van for 14 yrs with no problems. BUT No wash mach. etc.

Just Bread maker. Microwave. tv\box. 240 fans. etc etc.

Genny ran Air cond and topped up battery's.

while cooking dinner on Elect frypan. Stove.Kettle. 

NOT all at once.

Those people that say they run their complete rig. OFF Grid.  ALL the time on solar.

ARE fibbing....You HAVE to have alternative at times no matter what you have.

There have been enough of us over 50 odd yrs trying. We ALL run a genny.

Unless you going to outlay $10 grand or more. and a big roof area van.

Average people Don't.

Jaahn wrote:

---

Hi Ron

You ask a hard question that sounds easy

Using the voltage to measure the battery capacity is not reliable and needs experience with your own system to work at all. Batteriy voltage goes up when charging and down when being used, so can vary 0.5 V in 10 minutes between the two states easily and much more heavy loaded or charging.  Note that the battery is virtually flat at 12 v under no load but may recover to a higher V if left for a while. Over 14 is needed for full charging too and LA batteries need some time at full voltage to "fill up" completely or will not get properly fully charged.

The best way is a controller which measures the current going in and the current going out to give the best idea. Note you get back less than you put in also. So perhaps you could tell us what you have exactly to charge it and how long you drive.  Also tell us what you usually use each night, for how long and the current they draw so we could see what amp/hours is going in and out.  

Jaahn

 https://www.energymatters.com.au/components/battery-voltage-discharge/

State of Charge	Sealed or Flooded Lead Acid	Gel battery	AGM battery
100%	12.70+	12.85+	12.80+
75%	12.40	12.65	12.60
50%	12.20	12.35	12.30
25%	12.00	12.00	12.00
0%	11.80	11.80	11.80

---

 Thanks Jaahn and everyone else for your replies the Van is only one year old so it has a modern multi stage charge battery charger that brings the agm battery up to 14v and eventually settles to 13.7 volts ,and overnight off the grid comes  down to 12.4 Volts or less sometimes ,after 12month the AGM died, my thinking is that with an overnight load of 12v tv,water pump,led lights that should not be taken such a huge toll on the battery,maybe the answer is a second battery and more solar ,maybe the 80w portable panel is not enough although the same system worked for years in our old van,the only difference now with our power usage, with the current van compared to the old one is a larger Tv and a little more on the water pump,

The new battery just fitted is a 120 amp AGM and I will invest in a 160 watt panel to replace the 80w panel and maybe something to measure overnight current usage that's more accurate then the volt meter..

Battery charger Projector 7 stage switch mode

Dc/solar battery charger 25 amp 3 stage

projector low voltage disconnect...

Again good information thanks swamp so I gather a 120 Amp battery half equals 60 amp,so would that then mean we could use 60 amps of a fully charged battery overnight ,and still have a half charged battery say 60 amps in the morning, left for the solar panel to top up during sunlight hours.

Ron-D wrote:

---

Again good information thanks swamp so I gather a 120 Amp battery half equals 60 amp,so would that then mean we could use 60 amps of a fully charged battery overnight ,and still have a half charged battery say 60 amps in the morning, left for the solar panel to top up during sunlight hours.

---

Gday...

Ya gettin' the hang of it now Ron.

So, once ya get a good handle - probably a conservative handle - on just how many amps ya gonna consume during a day ... particularly between sunset and bed time/overnight, ya half way there.

THEN ... and this quite probably the real 'portant bit. Ya gotta have sufficient solar on the roof to provide the incoming charge required that will ensure the battery is fully charged before you want it all that night. OH, and hope ya got enuff sunshine to drive that amp input for enuff hours to get it back to fully charged.

So, in a nutshell -

• know just what amperage your set-up (watts used by EVERY appliance divided by 12V multiplied by hours used) will consume from sunset to bedtime/overnight;
• have enuff battery/s so that you don't use more than (ideally less than 40%) of what the battery can provide; 
• have enuff solar on the roof to fully re-charge the battery/s before the sun gets low on the horizon; and
• hope there is enuff all day to provide that charge rate.

Simple ain't it

Of course when doing all this figurin' ... underestimate your solar's charge ability by about 25%; overestimate your power requirements by 15%; and keep a generator in the boot for those days when you don't get full sun all day.

OH ... and the problem with askin' us mob on a forum, is that we are all totally different, with different needs/wants, and different lifestyles. Wot works for one sure 'nuff don't work for everyone.  

Cheers - John

[edit: and seeing as I have been a bit long-winded in the above - my set-up is one 120Ahr battery, charged by 360watts of solar panels. The battery is usually only down to 80% by first light in the morning, from 100% charge the night before. Even on overcast days my set-up keeps my battery fully charged (ie float charge 13.4V with 0.00amp coming from panels by mid-arvo at worst). This set-up works well for me .. but then again, I don't watch much TV or DVDs. Van is fully LED lights, fridge on gas when camping. OH and probably fairly importantly  I travel alone. ]

hi
RonD

solar wattage vs battery AH size

*****No body ever complains about to much solar or battery capacity****

160wattor better 200watts for every 100-120ah of battery

Why a good system recharges with plenty of time to spare
The suns PSH peak sun hours determines this also
PSH varies generally the more north in ozzy u are the greater the peak sun hours GOOGLE IT

U will hear of 1watt per ah of battery THIS IS A LOW PERFORMING SYSTEM eg 100watts =5 amps to charge 100ah battery way slow [recharging 50ah takes 10hrs + !!!]
2watts per ah of battery PERFORMANCE 200watts =11amps to charge 100ah battery [recharging takes 5+ hrs for 50ah ]

U need to get batteries back to as close to 100% every 24hrs as this will maximize there life span .

VAN solar is not domestic and does not have huge amounts of spare batt or panels similar to a house system .
Van systems are highly stressed and need to be charged well .

U can only use what u recharge 

Hi Ron

Some good ideas given here in every answer. But the summary is, more battery and more solar cause no problems and does solve most peoples problems. 

There is some difference in the battery capacity verses resting voltage from different sites. The answer for those who think some must be wrong or right, is this Go to the supplier or preferably the manufacturer of YOUR BATTERY and see what they say. Different chemistries give different results.

Cheers jaahn 

Wow what a wonderful response there's plenty very good information here even Johns trying to do my head in  thanks everyone ,I never had a problem with batteries when we had our avan pop top over the years ,so I did not have to expand my knowledge of solar power,now I really know what's going on great information not only for myself ,but others that might be tuning in to this post...

You Want longer life out of battery's.

Go two Battery's and more solar.

I ran 2 x 110a AGM's. with 340w of panels.with 80w one on roof of ute for backup.

Which gave us plenty of leeway. NO Wash mach. Coffee makers etc.
NEVER went below 12.5 by daylight. often much less drawn.

Don't let people con you.
12.1\2\3v is a very low battery.
Which equates to lots of deep recharges.
Which also equates to short life of your battery's.

As you finding out.


Compare us all and sort out yours.
Jus DON'T go too low on panels.
ALWAYS... More panel power than battery capacity.
For longevity at least.

Have fun.


HEYYYYYYYyyyyyyyyyyyyyyy...
How about the COWBOYS then.

G.F next week with Melbourne.
Who have at least 7 Q'LAnd players in there and a LOT of islanders.

Just wonder how many "Actual" Victorian born are on that team hey??.

Most of the good players in Aust.

Are Queenslanders. Aboriginal. And Islanders.

So it's BASICALLY another Queensland Final again. YES....

Chuckle.

Off to bed. Early night and start tomorrer.

The final piece of the puzzle I have worked out the amp hrs on everything we use and it comes to approx 25 amp  hrs in theory .

Is there any way of seeing the load on a device ,say have a device connected to your battery to measure the amp draw when you physically switch on and off an appliance , is a simple amp meter the way to go or is there a better device available .

thaks Ron....

Gday...

Ron, I offer the following .... however, I defer to others who may follow who know much more about this stuff than I.

I would assume your solar panels/system is providing charge to your batteries via a Solar Controller. 

This is what I have on my system -

SBC-7130 Solar Charger/Controller

I shows me -

• Battery SOC - float/absorb/bulk
• Battery Voltage - eg 13.4V float/14.3 during bulk and absorb -
  at dusk - battery SOC eg 12.8V - and as the night progresses down to usually 12.5V by morning
• Voltage available at the solar panels
• Amps going into the battery
• AmpHrs used Today
• AmpHrs used yesterday
• AmpHrs used two days ago

Hope that helps until someone else comes along that knows more and either confirms my comments ... or tells me to pull me melon in

Cheers - John

[edit: rocky can't spell ]

Hi,

Hi,

Don't forget to factor in the power still being used during daylight hours when you expect the solar panel to be recharging your battery.

David  

That's a great instrument John but it's expensive and it's makes a lot of sense especially if your on the road full time,were only on the road two to three months of the year,probably an amp meter or a digital volt  meter like warren suggests would give an indication of a gremlin in the system ?what  I would like to do is physically watch the current draw as things are turned on and off .

sounds like this will probably be impossible without an expensive high tec instrument and maybe it's worth the investment...

Ron-D wrote:

---

That's a great instrument John but it's expensive and it's makes a lot of sense especially if your on the road full time,were only on the road two to three months of the year,probably an amp meter or a digital volt  meter like warren suggests would give an indication of a gremlin in the system ?what  I would like to do is physically watch the current draw as things are turned on and off .

sounds like this will probably be impossible without an expensive high tec instrument and maybe it's worth the investment...

---

 Hi Ron

You can get a meter like this; http://www.ebay.com.au/itm/like/262896923486?chn=ps&dispItem=1

I just found that with a quick search, there are similar ones available commonly from retailers of batteries and 4WD places etc. They will tell you what is going on, Volts, Amps, Watts and the AHrs too. If you get two, you could put one in the battery charging input wires too. Then you would know everything coming and going  Probably not super accurate but close enough on holidays  I have two that I got with a pair of deep cycle batteries on special and use them on and off if I need to check something. They only read current going one way.

Jaahn

-- Edited by Jaahn on Wednesday 27th of September 2017 10:33:38 AM

Thanks  Jaahn now that digital watt meter is very interesting and might well work I think. I might buy one ,but here's another question and hopefully a final one as This saga is probably probably boring people by now,where I attach the solar panel to the outside of the van it's simply an Anderson plug connected straight to the battery .

now this little meter has two wires front and back would I be able to attach two of those wires too the external Anderson plug that goes to the battery to feed information into the meter,but then the the other two wires must connect to something that's the problem eh..

Ron-D wrote:

---

Thanks  Jaahn now that digital watt meter is very interesting and might well work I think. I might buy one ,but here's another question and hopefully a final one as This saga is probably probably boring people by now,where I attach the solar panel to the outside of the van it's simply an Anderson plug connected straight to the battery .

now this little meter has two wires front and back would I be able to attach two of those wires too the external Anderson plug that goes to the battery to feed information into the meter,but then the the other two wires must connect to something that's the problem eh..

---

Hello Ron

I am not a Techi, and can only speak of my own personal experiences

Firstly and most important, you should never wire a solar panel directly to your battery

Most solar panels put out from about 17 up to 21 volts, this voltage will damage a 12 volt battery
You must have a regulator between the solar panel, and the battery
Most portable (fold up) solar panels have a regulator attached to them
Some roof top solar panels do not have a regulator attached to them, and some do

I have a watt meter like the one Jahhn put a link to

I fitted an Anderson type plugs to each end of the meter, then connected it between the Anderson type plug, which was connecting my solar panel to my regulator near the batteries

I think (not absolutely certain) that they must be connected to the solar panel first, and then to the battery
I set one up and it worked OK showing the volts/amps/watt etc, but next morning the current still went to the battery but the watt meter showed nothing
I had to disconnected it from the battery, and reconnected it

Therefore (for me) it was handy to see what was happening, but it was not a fit and forget piece of equipment

Hope that this info is useful to you

Ron-D wrote:

---

Thanks  Jaahn now that digital watt meter is very interesting and might well work I think. I might buy one ,but here's another question and hopefully a final one as This saga is probably probably boring people by now,where I attach the solar panel to the outside of the van it's simply an Anderson plug connected straight to the battery .

now this little meter has two wires front and back would I be able to attach two of those wires too the external Anderson plug that goes to the battery to feed information into the meter,but then the the other two wires must connect to something that's the problem eh..

---

 Hi Ron

Simple really ! The meter wires need to be connected to the two wires from the panel, + & - and the other end is then connected to the wires to the battery + & -. Just inserted into both wire circuits. 

If you put an anderson plug on each  end of the meter as Tony did then you can put it in the circuit or remove it any time you like.  You could also use it to read the power use from the battery too if you fitted some anderson plugs on that side. Again you could put the meter in the circuit when you want to read that side. That is what I did. Have a look at the pictures in this listing; http://www.ebay.com.au/itm/12V-150A-Digital-Volt-Watt-Meter-Car-Caravan-4x4-Outdoor-Solar-Power-Voltmeter-1/132271596966?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20150313114020%26meid%3Da405caf3ae5a47198ac8f1e8587a192d%26pid%3D100338%26rk%3D1%26rkt%3D30%26sd%3D262896923486&_trksid=p2141725.c100338.m3726

Or just cut the two wires where you want to measure and permanently fit the meter in the two wire runs by joining the wires together.  Note the meter must be oriented the correct way to read the current and power correctly.

Jaahn   

PS I believe Ron has a set of portable panels with a regulator on the panels. If not then there must be one in the system.

-- Edited by Jaahn on Wednesday 27th of September 2017 09:22:43 PM

The portable solar panels  came with a regulater standard fixture on them,you can buy  digital  watt meters with Anderson plugs already connected to both ends,I already have an Anderson plug connection directly to the battery so that end would be simple,

too sum up just too connect the meter directly to the positive and negative terminals of the battery ,via the Anderson plug that's already there but on the outside of the van would that give me any information,hard wiring the instrument to the battery terminals is nothing it's already there,hard wiring it to the panel that would be a problem its just a long tin box under the bed I don't want to go there 

thanks for your replies 

Tony and Jaahn...

This whole battery discharge - charge can be somewhat confusing. Well very confusing actually.

For example a 100Ah battery may have the quoted capacity at a nominal discharge rate - commonly 20 hour rate. ie. 20 hours at 5 amps will see it dead flat. Discharge it at the 50 hour rate it may well exhibit a capacity nearing 200Ah. Discharge it at the one hour rate and it'll probably exhibit a capacity of less than 20 or 30Ah. To add a bit more confusion these numbers vary wildly with age - a battery nearing the end of its service life will exhibit far less capacity and just measuring its open circuit terminal voltage will show a full charge. It's just that a full charge isn't much.

To add even more confusion if you take 50Ah out of a 100Ah battery (measured accurately) and then put 50Ah back in (again, measured accurately) you won't have the full 100Ah capacity. Even the best AGM's don't have 100% charge efficiency although some approach that. Usually for a new battery in good condition it's about 95% to 99% charge efficient.

Then to add even more to the confusion there's more than one type of AGM - standby, high current, deep discharge, etc., etc.

I don't have enough experience with any type of Lithium battery but I bet that'd only add more confusion.

My basic rule of thumb (pretty rough bit mostly workable) is that if the battery is nearly flat by morning when the sun hits the solar panels then you need more battery. If during the day in good sun you can't get to fully charged then you need more panels.

For what it's worth that's my take on feeding batteries. As always I stand to be corrected.