Lithium Battery

[PAH]

Hello fellow Tvanners. This is our first post since taking delivery of our new Murranji last November. We decided to take the lithium battery option to enable us to stay out in the wilderness longer but we are finding it very difficult to maintain a level of charge in the battery that will sustain us for more than 2 or 3 nights and forcing us to scurry off to find a 240v outlet.
We use a portable 120w solar panel to augment the rooftop panel and are cautious with our power demands. The only appliance running during the day is our fridge/freezer (40L Evakool). We seem unable to gain enough power to balance our usage, even on a good sunny day, and lose 20-25% of capacity each 24 hour period.
What do others do to maintain charge and what is a reasonable expectation for solar panels on a sunny day? What charge do lithium battery users consider a safe minimum?
Looking forward to your informed opinions and suggestions as we have 6 nights booked on Dirk Hartog Island later in the season and at our current rate we won't be able to do it.

[luke]

and lose 20-25% of capacity each 24 hour period.

Do you have one or two batteries ? For two, that seems really excessive to me so I'd be trying to find out what's using power, and how much it's using.
(We have two, and loose about 8-10% overnight, and up to ~15% if we're running three fans or the electric blanket (Don't judge me, I spend too much time up north))

What do others do to maintain charge and what is a reasonable expectation for solar panels on a sunny day? What charge do lithium battery users consider a safe minimum?

Do you know the make/model of the batteries ? I can't find anything on the track trailer website about which ones they actually use ?

For ours, the vendor specs say it's safe to routinely go down to 20%, but the lowest i've ever seen our's is 75%
(200AH of lithium, with extra solar on the tvan rear hatch, and another one on the car roof just in case . . .)

[doctorflat]

While using the two AGM option, we expect/plan to consume a net 10% in 24 hours. This has proved to be the case over a couple of years. More sun as we go north is balanced out by greater consumption by the fridge which the major load. If you have around 100 AH of storage your 20% is about the same. I feel with the AGMs I can bank on 5 days taking me down to 50% capacity. You can discharge deeper and charge more quickly so could not guess. See you at DHI.


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[doctorflat]

Back again. Had to dash for train!
I have also been applying my brain to the DHI difficulty of stretching the batteries far enough. Interested also in what storage you have. We are tossing up between extra panels(great if the sun shines) or our portable 110 AH LiFePO4 battery which travels and charges in the car which could be useful during the explorations. Have contemplated plugging it into Tvan auxiliary socket for some supplementary charging to stretch AGMs out for the full time on the island. Worst case scenario could see us charging Tvan from car.

Pete


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[chris_a]

I know it might be a real pain but have you considered turning the fridge / freezer off for a 24 hour period to see if it is the culprit in terms of excessive power use? With so few demands on the batteries, the loss over 24 hours should hardly register. If the loss is significant without the fridge connected you may have further investigation ahead of you.

If it is the fridge / freezer, try running it as a fridge only (no freezer) and see how that goes over a 24 hour period. Freezers typically place great demands on your valuable power source.

Ambient temperature will be another variable you can't control. We can go for ages in Tassie without seeking out a 240v connection. It's quite a different story in the tropics.


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[hulbyw]

We went to the BRB last year and were camped for 6 days. We only run a small fridge in the Tvan with 1 lithium battery of 90 ah. I had an 80w solar panel plugged in to the Anderson plug near the 240v inlet (regulator on portable panel disconnected). By lunchtime each day our lithium battery was fully charged (sunshine all day) . This raises a few questions for you. Are you running the fridge as a freezer? How many batteries do you have ( a Nov. build will have 100ah lithium) Are you connecting the portable panel to the Anderson plug with its regulator disconnected? BTW we have friends that went to Dirk Hartog and they really enjoyed it

[peter_mcc]

Do you charge the battery from the car when you're driving? I've found that the solar panel doesn't work all that well when we're driving because of trees.

Do you park the Tvan in the sun when you're camped? It doesn't take much shade to kill the solar panel output, especially if you shade a "whole row" of cells.

That amount of power consumption seems excessive - I'd try unplugging the fridge and turning everything off to see how much power is being used. Then start reconnecting things. Perhaps the fridge has problems that cause it to run more often than it should.

[monktm]

Why not use the VictronConnect app and start checking what's drawing power and how much ? Start unplugging things one at a time something is sucking the power ? Or your solar isn't working correctly what do you put in using solar ? How many amps

[Gumb]

All good suggestions but we need more information from the original post.

How many batteries do you have ?

Is the fridge running as a freezer ? What's the temperature set at ?

[Harry Lissimore]

And the ambient temperature!

[robstevens]

Lets do the maths:

Fridge/Freezer consumption: 3 Amps per hour (assuming on half the time) = 72 Amps consumption over a 24 hour period
Solar Input: 120W (6A) for 4 hours / day + portable panel 120W (6A) for 4 hours / day = 48 Amps input over a 24 hour period.

So each day you are discharging the battery or batteries by: 72-48 = 24 Amps per day.

With one Lithium you have about 80Amps usable, so I'd suggest you can last about 3 days before you need another source of charging for the batteries!

(Assuming you only have one lithium battery)

[Nomadic]

I agree with Rob, you will struggle with the amount of solar you have.
As an example this is my average solar requirements to run two fridges (85L and 30L drawer type). On a cold but sunny day I only require approximately 350 watt/hours to run fridges and get a lithium battery (180ah) back to 100%.
On a warm day it's more like 700 w/h and if I am playing around in the camper I may need 1 to 1.5 Kw/h. As you can see by my graph, everyday is different depending on temperature, loads and cloud conditions.

My main solar array is 390 watts but at this time of the year it doesn't put out anywhere near this amount.
In the summer months when the sun is higher it puts out more but then it can be degraded with temperature together with much higher loads on the fridges the net gain isn't that much better.
In summary,  with 390 watts solar it takes 4-5 hours in bulk to get the batteries back to 100% at this time of the year. Lithium's are great but whatever you take out of them you have put that same energy back in. It can be difficult with a small array, low sun angle in winter and any shading.

[monktm]

Hello fellow Tvanners. This is our first post since taking delivery of our new Murranji last November. We decided to take the lithium battery option to enable us to stay out in the wilderness longer but we are finding it very difficult to maintain a level of charge in the battery that will sustain us for more than 2 or 3 nights and forcing us to scurry off to find a 240v outlet.
We use a portable 120w solar panel to augment the rooftop panel and are cautious with our power demands. The only appliance running during the day is our fridge/freezer (40L Evakool). We seem unable to gain enough power to balance our usage, even on a good sunny day, and lose 20-25% of capacity each 24 hour period.
What do others do to maintain charge and what is a reasonable expectation for solar panels on a sunny day? What charge do lithium battery users consider a safe minimum?
Looking forward to your informed opinions and suggestions as we have 6 nights booked on Dirk Hartog Island later in the season and at our current rate we won't be able to do it.

Some great and informative information here . So what have you worked out is wrong ?

[Firetail 17]

One thing to always remember is that your solar panel set up is only as good as the weakest panel. What this means is that if you have 2 solar panels, one on the roof of the TVan and a portable one plugged into the Anderson plug near the 240 volt plug on the drivers side, if one of the panels is in the shade this will bring down the performance of both panels.
I have installed a Schottky diode (rated to the current of the panel) on the positive output of both my fixed on the roof and portable panels. This will stop the above issue. Schottky diodes are available from Jaycar.
I have also bypassed the regulator on my portable panel as this is not needed with the Redarc bcdc charger in my Firetail.
Trevor

[robstevens]

Yes - if you have a Redarc DC DC chrager with solar input, then definitely remove the cheapo regulator on the solar panel (if it has one)...