Ive installed a drok battery meter/monitor on my 120 ah second battery, all seems good but can an auto elec explain the display below, volts, amps, watts, engine idling battery receiving charge. Cheers

Alternator output is at 14.08V, battery is drawing 1.1A from the alternator, W = V x A so 14.08 x 1.1 = 15.48W of power consumption from your alternator bus. The Amp Hour reading at the bottom is basically how many amps have been put into the battery over a period of time in Ah so if all goes well you will get something similar to this out of the battery when discharged but look up Peukert's law to see how high discharge currents give you less battery capacity and you may not get as much back out for high discharge rates.

Can someone please explain this^^^^^ to me?

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Paddles B'mere said..
Alternator output is at 14.08V, battery is drawing 1.1A from the alternator, W = V x A so 14.08 x 1.1 = 15.48W of power consumption from your alternator bus. The Amp Hour reading at the bottom is basically how many amps have been put into the battery over a period of time in Ah so if all goes well you will get something similar to this out of the battery when discharged but look up Peukert's law to see how high discharge currents give you less battery capacity and you may not get as much back out for high discharge rates.

Cheers, so all good for a new agm battery ? Charging seems ok ? Using a Projecta isolator and 6 b& s cable to ute tray

Its putting out lots and you are using FA so the battery will be charging.

Yep, volts are high and current is low so your battery is pretty well charged

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Buster fin said..
Can someone please explain this^^^^^ to me?

Compuuer sez no.

so now gotta add mine, sorry for thread hijack


I wanna camp for 3 days and have solar replenish my car battery - I am only running a 39L Engel.
The solar puts out 21V.

Some people say bung that on the car battery as-is, just for a few hrs a day its all good at 21V
Most people use a regulator circuit to make it 14.4V or whatever.

I can see both sides.... I am sure the Engel is designed to accept 12-21V easily, and it could run on 12V most of the night and then 21V on the battery whilst being charged all morning...? chargers always put out more than the nominal voltage of the battery anyway. Is 21 too much...?

Do I just get another battery to run off and put solar on it for half a day whilst engel runs off car, then swap (ie: 2nd battery not in car,just next to the engel on the ground...)

Hey mark last big trip up north we bought a seperate battery and hooked the Engel and solar up to it, ran the Engel for two weeks like this no dramas.
the solar charged the battery during the day and the Engel ran 24/7 off the battery.
I thought it would suck it dry but it went ok, I don't know how many days you could push it for or How long the battery will last.
In my dingy I have pull start tiller steer 30hp but I wanted a sounder so my battery charges off a tiny little solar panel about 350x350.
this runs the nav lights and sounder.
i can run the sounder for around 12 hours at least before needing to put the solar out.

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Mark _australia said..
so now gotta add mine, sorry for thread hijack


I wanna camp for 3 days and have solar replenish my car battery - I am only running a 39L Engel.
The solar puts out 21V.

Some people say bung that on the car battery as-is, just for a few hrs a day its all good at 21V
Most people use a regulator circuit to make it 14.4V or whatever.

I can see both sides.... I am sure the Engel is designed to accept 12-21V easily, and it could run on 12V most of the night and then 21V on the battery whilst being charged all morning...? chargers always put out more than the nominal voltage of the battery anyway. Is 21 too much...?

Do I just get another battery to run off and put solar on it for half a day whilst engel runs off car, then swap (ie: 2nd battery not in car,just next to the engel on the ground...)

mate just by a cheap regulator of ali express (or ebay)
they are under $20 delivered. same ones will cost you $200 in shops
https://www.ebay.com.au/i/183242623273?chn=ps

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Mark _australia said..
so now gotta add mine, sorry for thread hijack


I wanna camp for 3 days and have solar replenish my car battery - I am only running a 39L Engel.
The solar puts out 21V.

Get two spare 6 volt batteries. Charge them in parallell, in series with the fridge during the day, Hook the batteries up in series to run the fridge at night.

21V will eventually kill your 12V battery Mark, you really should look at some sort of regulator for your solar. You might get away with something like Ian is suggesting and put two paralleled 6V cells in series with the 12V cell to give an effective 18V cell for charging (and then switch it all around to give 12V for driving the fridge). But remember that volts are only part of the equation, it's power output that rules the roost and if your solar doesn't put out enough power to actually put current into the batteries then it's a waste of time. The thing I hate with paralleled batteries without a good management/isolation relay is that if a cell fails in one battery, the good battery will feed the fault until it dies.

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Paddles B'mere said..
21V will eventually kill your 12V battery Mark, you really should look at some sort of regulator for your solar. You might get away with something like Ian is suggesting and put two paralleled 6V cells in series with the 12V cell to give an effective 18V cell for charging (and then switch it all around to give 12V for driving the fridge). But remember that volts are only part of the equation, it's power output that rules the roost and if your solar doesn't put out enough power to actually put current into the batteries then it's a waste of time. The thing I hate with paralleled batteries without a good management/isolation relay is that if a cell fails in one battery, the good battery will feed the fault until it dies.

WTF? by three batteries or you could get a solar regulator for $15

I never said it made economic sense, just said that it might work

Mark set it up for next question about solar, cheers

Im thinking about a 110w solar panel on ute canopy, L x W dimensions about right, any more watts and panel will be too big, I drive about 1 hr a day during normal week and ute usually parked outside all day, I want 60lt fridge running off second battery 24/7, would have solar panel thru regulator to second battery, also heading off soon on 6 week central oz trip, any thoughts ?

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myusernam said..

WTF? by three batteries or you could get a solar regulator for $15

A $15 regulator will just throw those extra volts ( times the current ) away as waste heat. What a waste of solar power!

@surfer62, what's the max current draw of the fridge? (look in the book) For your usage, I would not bother with solar and just charge with the alternator whilst driving, take a decent battery charger with you and whenever you're somewhere with power and not moving charge it all up properly. Check the alternator size/output for your car. You also need to make sure your battery size is adequate for the load/charging cycle. An AGM can be safely cycled at 80% of capacity, lead/acid about 50% and not affect long term battery life.

Another key question is temperature, ie what fridge temp is required and what the ambient temperature is. I can run our car fridge pretty well indefinitely on a 120AH battery, with a 180w solar feeding it during the day. I adjust the fridge temp lower during the day, (when the sun is shining) to to minus 5 or 8, that keeps the frozen stuff at the bottom, (slowly defrosting meat etc) and the beer is perfect in the top. At night I set the temp of the fridge up to say 2 degrees...reduce the load on the battery at night... Also limit fridge openings, and keep it in the shade... 2 week camps on the beach up north in sept / oct no additional charging required... we also have a gas dometic fridge, which I reckon are awesome, but that's another story.....

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Ian K said..

myusernam said..

WTF? by three batteries or you could get a solar regulator for $15

A $15 regulator will just throw those extra volts ( times the current ) away as waste heat. What a waste of solar power!

its an mppt microprocessor controlled regulator.

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myusernam said..

Ian K said..

myusernam said..

WTF? by three batteries or you could get a solar regulator for $15

A $15 regulator will just throw those extra volts ( times the current ) away as waste heat. What a waste of solar power!

its an mppt microprocessor controlled regulator.

Back in the day an LM309 cost about that much. It's all done with induction! Now I know.

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myusernam said..

Ian K said..

myusernam said..

WTF? by three batteries or you could get a solar regulator for $15

A $15 regulator will just throw those extra volts ( times the current ) away as waste heat. What a waste of solar power!

its an mppt microprocessor controlled regulator.

I think MPPT is meant to get the maximum energy transfer from the panel as the optimum voltage for the panel will be very different to the battery voltage.

Are the cheapish solar chargers on ebay MPPT? I assumed they were just linear regulators.

^^^ Oh now you've done it Ian hahahaha
I wanted to get a cheap reg but didn't know which one would be cheap but work..... so the one posted above would be good
Now u make sense about wasting power. Especially as i only have 40W

Hmmm

The car is going to be run each day for 15min anyway so maybe just the solar and reg onto car battery as insurance.

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FormulaNova said..

myusernam said..

Ian K said..

myusernam said..

WTF? by three batteries or you could get a solar regulator for $15

A $15 regulator will just throw those extra volts ( times the current ) away as waste heat. What a waste of solar power!

its an mppt microprocessor controlled regulator.

I think MPPT is meant to get the maximum energy transfer from the panel as the optimum voltage for the panel will be very different to the battery voltage.

Are the cheapish solar chargers on ebay MPPT? I assumed they were just linear regulators.

Nah for a while they were $5 extra now theyre all mppt. Same ones in shop over $200. Talk about rough end of he pineapple. Have a look theres various types. Mine has a nice lcd dispay that shows load current, batt voltage etc. Can specify low voltage cutout etc might cost u $19 for that one

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Mark _australia said..
^^^ Oh now you've done it Ian hahahaha
I wanted to get a cheap reg but didn't know which one would be cheap but work..... so the one posted above would be good
Now u make sense about wasting power. Especially as i only have 40W

Hmmm

The car is going to be run each day for 15min anyway so maybe just the solar and reg onto car battery as insurance.

If they are MPPT regulators as myusernam says, you will get more energy from using them than you would tying them directly to the battery, or using an old style regulator.

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Paddles B'mere said..
@surfer62, what's the max current draw of the fridge? (look in the book) For your usage, I would not bother with solar and just charge with the alternator whilst driving, take a decent battery charger with you and whenever you're somewhere with power and not moving charge it all up properly. Check the alternator size/output for your car. You also need to make sure your battery size is adequate for the load/charging cycle. An AGM can be safely cycled at 80% of capacity, lead/acid about 50% and not affect long term battery life.

Awesome advice, I think fridge draws about 1 amp/hr, the agm is 120 ah, mq triton so I think the alternator pumps out 75 amps and 14.2 v at idle, the meter reads just under 14 v when on the road. cheers

A good regulator/charger is definitely the go, but the most important thing is to properly size your battery according to your load requirements and proposed charge/discharge cycle and then size your panels/regulator/charger to suit (remembering a rule of thumb for solar is roughly 5 hours at maximum panel output per day).

So if you have a load that needs 100Ah/day at 12V then you need a minimum 125Ah AGM battery (based on 80% discharge cycle) and you will need a solar system that will output the 100Ah back into the battery at 14.4V (or thereabouts) in about 5 hours. So this will mean an output of 20A (100Ah divided by 5 hours) at 14.4V which is 288W. This quick calc does not allow for losses and inefficiency, nor does it give you a fudge factor for a cloudy day. But you can easily correct by say doubling the battery/panel size to give two day's capacity between charge cycles and then apply an additional percentage to allow for inefficiency.

A big alternator like the oversized one in my Land Cruiser will pump out over 80A and not care if it's cloudy. In the case above, it will dump 100Ah back into the battery in just over an hour's driving. That's why I reckon if you're someone who is on the move a bit, use an oversized battery and alternator and don't bother with the solar. If you go to a camp for a week and don't drive the car then solar is the go.

I just saw your numbers above surfer62 and I reckon your setup will be fine, you'd probably get away with stopping somewhere for a couple of days as long as you manage the fridge and don't drink too much beer (hot cans will cost you more power to cool down) Something I should add is that you want some big cable to that battery too (if it's in your tray and not the engine bay) so you don't get a problem with voltage drop when it is charging when you're on the road.

Which lead acid batteries will accept 80Ah charge?

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Paddles B'mere said..
A good regulator/charger is definitely the go, but the most important thing is to properly size your battery according to your load requirements and proposed charge/discharge cycle and then size your panels/regulator/charger to suit (remembering a rule of thumb for solar is roughly 5 hours at maximum panel output per day).

So if you have a load that needs 100Ah/day at 12V then you need a minimum 125Ah AGM battery (based on 80% discharge cycle) and you will need a solar system that will output the 100Ah back into the battery at 14.4V (or thereabouts) in about 5 hours. So this will mean an output of 20A (100Ah divided by 5 hours) at 14.4V which is 288W. This quick calc does not allow for losses and inefficiency, nor does it give you a fudge factor for a cloudy day. But you can easily correct by say doubling the battery/panel size to give two day's capacity between charge cycles and then apply an additional percentage to allow for inefficiency.

A big alternator like the oversized one in my Land Cruiser will pump out over 80A and not care if it's cloudy. In the case above, it will dump 100Ah back into the battery in just over an hour's driving. That's why I reckon if you're someone who is on the move a bit, use an oversized battery and alternator and don't bother with the solar. If you go to a camp for a week and don't drive the car then solar is the go.

I just saw your numbers above surfer62 and I reckon your setup will be fine, you'd probably get away with stopping somewhere for a couple of days as long as you manage the fridge and don't drink too much beer (hot cans will cost you more power to cool down) Something I should add is that you want some big cable to that battery too (if it's in your tray and not the engine bay) so you don't get a problem with voltage drop when it is charging when you're on the road.

Ive also heard a full fridge is more efficient, take one beer out and replace

Used 3.5m of a single positive 6 b & s from battery/isolator and earthed to tray same size, 6 b & s to anderson plug beside 2nd battery for fridge, tried to keep all distances to minmum.

^^^true, keep it full and cold

Any battery bigger than 80Ah will accept 80Ah kk, you mightn't be asking what you want to ask?

Thanks paddles, owe you a beer

By the way the drok meter mounted in cab is wifi from shunt on 2nd battery, pretty handy to keep an eye on 2nd battery, $29 fleabay