Building My Home Made Caravan by JR

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J.REEVES
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Re: Building My Home Made Caravan by JR

Post by J.REEVES » Wed Oct 15, 2014 3:31 pm

Time to replace the battery and install an Inverter and up the Solar

The BMS can be very simple to very sophisticated, my system is very simple.

I used a Cell Logger supplied from Hobby King only $30.00
cell logger.jpg
This little thing can monitor up to 8 cell and is the backbone of my BMS.

Data as seen on the screen:
Top line: 4S 13.31V is the total voltage of the four cells
Top line: V 4mV is the largest voltage variation between cells
Second line: 1. 3.32 is the voltage of cell No1 and so on for the other cells

The cell logger can monitor cell max and cell min volts
Total of all cells max and min volts and max variation between cell voltages.
All these items can have a set alarm and all can operate a common 0.5amp contactor within the logger. The logger has its own audible alarm and can also output to a computer to display past data at preset time interval.

So from this little device you can operate other devises to protect your lithium battery.

I chose to output the cell logger to a 8amp latching relay which requires manual resetting so if any item goes out of limit I get an alarm and also a trip on the inverter which is a heavy current devise. Most other inputs and outputs to the battery are covered by the solar controller high and low trips. I have no trip on the C-Tek 240V charger but it is very rarely used and is set to supply mode (13.6V).
Latching Relay
latch relay.JPG
It is very important not to let lithium cell voltages go high or low or have variations between cell voltages. At $1200 for a 200AH cell set it’s worth the extra effort to protect them. The cells are completely sealed so if the cell is overcharged the cell will start to distort.

Basically there needs to be a trip on all inputs to the battery like solar and 240V chargers to protect the cells from over voltage and voltage imbalance. With lithium it is possible for a cell voltage to run away from the other cells so the total high voltage trip is not good enough as one cell may contribute a larger part of that high total voltage so each cell needs to be also monitored.
There also needs to be a trip on battery load to protect the cells from low voltage.

JR
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Re: Building My Home Made Caravan by JR

Post by J.REEVES » Wed Oct 15, 2014 4:14 pm

Time to replace the battery and install an Inverter and up the Solar

Extra solar
Now that I have a reasonable amount of power available I decided to upgrade the solar to accommodate the extra amp hours that we have and will probably use.
The original solar panel was a 125watt BP panel and is working as good as the day we installed it. At the time the BP panel was $1200.00 and now the two new 160watt panels were $220.00 each.

I had already fitted a 30amp MPPT controller in anticipation that I would upgrade to more solar. The only problem is that the new solar controller does not have a setting for Lithium. Most solar controllers don’t have lithium settings anyway.
The new solar controller is an Epsolar Tracer 30amp MPPT controller with a remote controller/monitor. Having the remote was a requirement that I needed so I could have control at the existing electrical control station in the van.

There are some good PWM controllers that can be set to control to your own settings so to accommodate lithium. The GEL setting on the Tracer has a lower voltage setting for bulk charge so I have set it to GEL. The lithium battery has not reached any of the alarm limits so it is looking OK to use GEL as a control setting.

I chose the 160watt panels as they are almost a perfect square 1mtr x 1mtr and fit better on the van roof. The remaining area on the roof is reserved for a sat dish, one of these days.
Solar on the roof.jpg
The solar will be the main source of charging for the battery and the old C-Tek will be used just to top up before we head off on a trip. The C-Tek may require a couple of days to accomplish this.

The solar panels feed separately down to one shottky diode each this is just in case one panel decides to back feed into another panel. Shottky type diodes are a better choice than normal diodes as they have less voltage drop when on.
shottky diodes.jpg
I have upgraded the analogue amp meter from 20amp to 30amp to display solar total output and have fitted extra 25amp switches above the analogue meter to switch individual panels on and off, mainly to test each panel from time to time to see each is working correctly.
Lithium cell logger.jpg
At this stage I will continue to use the C-Tek to charge the Lithium when on 240V but have selected the C-Tek to supply mode so the output is limited to 13.6Volts. 13.6V is a safe voltage for lithium but there is a small danger that one cell voltage may run away. When the van is at home and not in use it is best to charge the battery then switch all charging off.
These batteries can sit for many months and still hold a large percentage of their charge and don’t like to just sit there on a float charge so best to switch the battery off. I have a 250amp isolation switch on the battery so it’s only a matter of operating this switch to fully isolate the battery.

JR
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Re: Building My Home Made Caravan by JR

Post by Milton477 » Wed Oct 15, 2014 10:53 pm

Much more food for thought JR. You must have thought long & hard about your design. I seriously considered installing a small PLC controller with a touch screen to control all aspects of my van electrical & water but hey, it's only a caravan. Don't need to be sitting on the beach modifying PLC code to change the way things work.

I have installed a 200W, 24V solar panel with Victron controls:
20141015_214644 (Medium).jpg
Management is achieved with this:
20141015_214635 (Medium).jpg
Charging is also by Victron:
20141011_132225 (Medium).jpg
Victron is conveniently supplied by Springers located not far from me. I am led to believe that the Solar Charger strategy can be changed with a laptop, software & the correct cable. Maybe one day when I am bored & I thought caravans were simple.
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Re: Building My Home Made Caravan by JR

Post by J.REEVES » Thu Oct 16, 2014 1:14 pm

Hi again Rory,

Looks like you are moving along with your build!

Yes you don't need to be sitting on the beach modifying PLC code to change the way things work after all it’s a caravan not a power station control panel.

I think the Victron equipment is a good option and as you say there is a way to program different settings into the controller. Not sure if a large range of settings can be adjusted but at least there are some setting available to play around with. I believe controllers like the Dingo is the one that the enthusiasts go for as you can create an algorithm to suit your needs.

I have found the Tracer is working well on the GEL setting to charge the lithium. Bulk charge to 14.2V then sit for two hours at 14.2V and then drop back to 13.8V float. Each cell has not drifted into the danger area (4.2V and higher) and usually all sit at around 3.55V to 3.58V (alarm 3.65V) when on bulk charge and by the time two hours is up the current has almost hit zero.

I will be getting a Victron BMV 702 but at the moment I only have the compact BM-1 which can only handle a 100amps which is OK but when I run the inverter via a separate circuit I will need to be able to handle 250amps. The BM-1 is not in the inverter circuit so cannot know what power is being used there.
BM-2.jpg
Some people have taken up lithium in a big way and are almost obsessed with getting there BMS to the ultimate level.
Really to charge a lithium battery is simpler than charging a lead acid battery, the lithium takes everything and then when the volts start to move above a certain value stop.

In the next couple of years I think we will see these lithium batteries take over in a big way and then there will be chargers and BMS flooding the market.

The small amount of experience I have had with lithium suggests they are a very good battery and a big step in battery technology.

P.S. T1 Terry has been a great help with his knowledge and has given me some good advise.

JR
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Old Techo
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Re: Building My Home Made Caravan by JR

Post by Old Techo » Thu Oct 16, 2014 4:57 pm

J.REEVES wrote:Time to replace the battery and install an Inverter and up the Solar :razz:
Very nice looking work JR :)

You set high standards ;-)
Regards, Old Techo
2007 Prado Grande Diesel Auto
2004 Roadstar Limited Edition

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Re: Building My Home Made Caravan by JR

Post by Old Techo » Thu Oct 16, 2014 5:22 pm

Speaking of building a caravan, I thought of Bussy. As a very regular project updater he is noticeably AWOL.

Checking his last log-in it was Aug 6th and that's a bloody long time ago :shock:

Anybody heard from Bussy lately?
Regards, Old Techo
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J.REEVES
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Re: Building My Home Made Caravan by JR

Post by J.REEVES » Thu Oct 16, 2014 7:40 pm

I dropped in to see how Bussy’s build was going in early September when down in Melbourne. Everything was going well but he had a hold up with material that he was going to use on the roof but seemed to be going good. I must say that his van will be a real power house four 200watt solar panels and two sets of batteries with two solar regulators.

Also he was talking about going on a holiday over to Thailand I think.

JR
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Re: Building My Home Made Caravan by JR

Post by J.REEVES » Fri Oct 17, 2014 11:39 am

Time to replace the battery and install an Inverter and up the Solar

The Inverter
The inverter is a full sine wave inverter and has a rated capacity of 2500watts. The inverter is a Mishto and is at the bottom of the ladder price wise and probably quality wise.
The first one of these inverters when under test lasted about 30seconds with a 500watt load. Due to the speed the inverter started to burn I have fitted a 250amp fuse and a 250amp isolation switch beside the replacement inverter.

To the suppliers credit they immediately relaced the failed inverter but made the comment that they had never had a failure before now that a bit of a surprise!
Mishto inverter.jpg
My first Inverter
Inv Full View.jpg
As the inverter is not exactly the pick of the crop I am keeping my eye out for a better inverter but need something of similar size to fit in the location. To get an inverter that is a pure sine wave and 2500watts and have some quality I could be looking at something possibly five times the price of this one. To date the second inverter has performed faultlessly and I am starting to gain trust in the product.

When the inverter is fully loaded it could be pulling up over 200amps from the battery so I needed to mount the inverter very close to the battery to limit voltage drop using 0 B&S cable.

I used a 63amp selector switch to switch the 240V between the inverter and the main supply this switch switches active and neutral and also with a third set of contacts switches the inverter on and off and operated a slave relay to switch some items off.

I have an AES fridge so when we are bush camping and the fridge is on gas and we turn the inverter on the fridge would see 240V available and switch to it. The slave relay switches a 240V relay to switch the fridge 240V supply off when the inverter is running.

I will not go into the 240V protection side of things as that can create some robust discussion at times only to say that area is covered.
Micro wave switches.jpg
I have already been caught out once when running the inverter to power the 1400watt microwave. The day before we were on power and today we are bush camping and forgot to turn the 240V off the 1440watt HWS so when we turned the inverter on to power the microwave the total power was now 2840watts so the inverter ran for one or two seconds and then tripped. Once we worked out the problem I was relieved to see that the inverter protection did what it was designed to do.

What I liked about the Lithium Battery:
The lithium battery holds its voltage no matter (well almost) how much current you drag out of it.

Charging is quicker as the battery takes almost full current available until it is near full or at least 90% full.

These batteries are said to take 2000 to 3000 recharges where as a lead acid is something like 500.
I think if I treat this battery right it will see me out.

Peukert’s law almost does not apply to these batteries and charge efficiency is very high.

Lithium is almost half the size and is half the weight.

When pulling about 150amps from the lithium the volts held at 13.1V.

I sound like a car salesman but really even now the price is not that much more than lead acid. A 200AH Lithium can virtually deliver 200AH’s whereas a 200AH Lead Acid is safe to deliver 100Ahs so if you really need 200Ahs from a lead acid battery you would need almost 400AH’s of battery and that will probably cost more than the 200AH Lithium.

What I didn’t like about the Lithium Battery:
Not a battery you can just drop into the shop and have fitted without some planning.

Availability of solar and 240V charges with a lithium algorithm is not that common.

Even with lead acid if you run them flat chances are they will be buggered but with lithium almost a certainty.
Over charging also means destruction of the battery as they can only accept their rated AH’s plus or minus a small percentage.

You do need a good battery SOC monitor as volts hardly change from full to empty from what I have seen. The Victron BMV 702 is the one most use.

Lithium does not like to be left for long periods on a float charge. When my van is in storage I left my C-Tek on float for long periods but best to completely isolate lithium after it is charged.

A BMS (battery management system) is a requirement for lithium so you need to add more hardware. You could take the gamble and not have a BMS are you game?

Each cell is almost a separate critter and the voltage can drift away on a cell or two but this is usually at the top end of their charge. I personally never seen this happen and following other peoples comments that have had lithium much longer it is not a common event.
Basically a 12V Lithium battery set fully sealed cannot be covered for a cell imbalance so must not be much of an issue.

Summing up
I have only had a five week run with the new Lithium battery but must say this battery is very impressive and very different to a lead acid battery.

I never seen the volts drop below 13.1V and we ran the Diesel Heater every night for around fourteen hours plus all the lights, TV and normal stuff plus five minutes run of the pod coffee machine and five minutes run of the micro wave and finally we have a toaster that works in the bush. I have never been happy with the toasters that sit on a gas burner and have tried them all and in the end made my own using 1/8” copper plate but even it is a problem to cool down when finished. Now we can use our 240V toaster and it works as a toaster should!

I would like to thank T1 Terry for all his help and advice as he would have more knowledge and experience with Lithium than most.

JR
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+AW01+
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Re: Building My Home Made Caravan by JR

Post by +AW01+ » Thu May 03, 2018 1:55 pm

Hi Mate,
Where did you buy the 'Top Cupboard shelf edge' trim - the one that slides of the edge of the shelf and has a lip to stop things falling/rolling ooff the edge?
Thanks,
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J.REEVES
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Re: Building My Home Made Caravan by JR

Post by J.REEVES » Thu May 03, 2018 3:44 pm

Hi AW01
The product is Shelf Edge (C2603) which is a Jayco part number. Not sure if it is still available as it was late 2006 when I purchased it. It is designed to take 9mm thick ply.
If you can still buy it best to try a large Jayco place that carries spares.

JR
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