Caravan off grid set up.

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Caravan off grid set up.

Postby Al510 » Thu Oct 25, 2018 7:32 pm

Planning my electrical set up for a live in van construction and would like some advice on my options.
I am looking at a system that can run a small domestic inverter fridge, through an inverter,a microwave on occasion, as well as electric kettle and toaster. The biggy though will be a 2kw inverter domestic split system.
I am looking at between 700 and 1000 AH of lifepo4 in 12v or 24v with half the AH for the lower amperage required for solar and inverters. 24v would be my preference.
The cheapest option for cells just browsing the internet, seems to be CALB 100AH, but would require up to 40 cells. Larger winston cells would be a bit more expensive but simplify the instalation. Which would be the prefered, lots of smaller cells or fewer larger cells?
My next question is regarding solar regular/ inverter/battery charger. Victron make units that do all three functions. This would posibly make things more simple , but are there down sides to this? The cost seems to be similar to use seperate devices.
I am looking at around 2000w of solar to power all of this.
Cheers, Al.
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Re: Caravan off grid set up.

Postby davidg » Fri Oct 26, 2018 5:56 am

How much solar in kw and which MPPT charger controller?

Don't use a cheap MPPT charger controller.
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Re: Caravan off grid set up.

Postby Al510 » Fri Oct 26, 2018 6:59 am

2kw is about all i could fit. I like the look of the victron energy controller.
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Re: Caravan off grid set up.

Postby davidg » Fri Oct 26, 2018 7:33 pm

Al510 wrote:2kw is about all i could fit. I like the look of the victron energy controller.


Only use one of MPPT charge controllers otherwise it's a waste of time nowadays.
other very good brands, Midnite, Morningstar, Apollo, Outback.

A recent DC coupled system I installed, as an example (the MPPT charge controller in that system is a Midnite) post53770.html#p53770
Last edited by davidg on Fri Oct 26, 2018 8:38 pm, edited 2 times in total.
SPS Standalone Power System/Hybrid specialist - Store the Sun!
SELECTRONIC SPMC482-AU, 8.2kW's of Arrays
Selectronic Certified AC-Coupled Fronius 8.2kW Inverter
1900Ah 48V Bank

An OTT Genset for a house.
PVOutput Stats

Sparkys light up your life :)
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Re: Caravan off grid set up.

Postby Al510 » Fri Oct 26, 2018 8:29 pm

Thanks David.
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Re: Caravan off grid set up.

Postby Al510 » Sat Oct 27, 2018 10:19 am

https://www.victronenergy.com/inverters ... /easysolar

If i was to go with the 24v 3kva unit above, would it be possible to set up high and low voltage disconnects, where the low voltage disconnect allows the solar to keep charging , or would it be total disconnect? The high voltage disconnect could be between the solar and regulator, but the low voltage disconnect would need to be between the inverter and battery, which would also cut the solar?
Would it be better to go with multiple smaller inverters to suit the two main continuous loads, the fridge and aircon And seperate solar regulater?
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Re: Caravan off grid set up.

Postby davidg » Sat Oct 27, 2018 11:00 am

Al510 wrote:https://www.victronenergy.com/inverters-chargers/easysolar

If i was to go with the 24v 3kva unit above, would it be possible to set up high and low voltage disconnects


Hmm, don't know however typically I would do a system that is based what is required to supply the maximum likely load as may occur at some stage at a site, mobile or otherwise, I think all in one solutions are NOT the best option because if for instance the MPPT charge controller failed then the whole unit requires to be sent away, the same would go for the inverter, BTW remember KVA is a number that does not reflect the real output ability of an inverter, ie a 3KVA inverter is generally only be able to supply approx 2.4Kw's maximum.

The SPMC482-AU I listed in the system and I also have is a true 7.5Kw's 100% of the time, 8Kw's for an hour, 12Kw's for 30 mins, 18Kw's for 10 seconds, which I have tested they really do what they say, yes you pay for it but they are really great inverters and have really great warranty to boot.
Last edited by davidg on Sat Oct 27, 2018 11:30 am, edited 1 time in total.
SPS Standalone Power System/Hybrid specialist - Store the Sun!
SELECTRONIC SPMC482-AU, 8.2kW's of Arrays
Selectronic Certified AC-Coupled Fronius 8.2kW Inverter
1900Ah 48V Bank

An OTT Genset for a house.
PVOutput Stats

Sparkys light up your life :)
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Re: Caravan off grid set up.

Postby Al510 » Sat Oct 27, 2018 11:23 am

, I think all in one solutions are the best option because if for instance the MPPT charge controller failed then the whole unit requires to be sent away

Are the best options, or not the best option for those reasons? I did cosider the failure issue, ie if the solar reg failed and i had seperate charger/inverter, i could still run of a small genny.
That looks like a nice unit, they do a 24v 3kw one also that would suit me but almost $5000
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Re: Caravan off grid set up.

Postby Al510 » Sat Oct 27, 2018 11:50 am

Thanks David. The 3kw unit looks the goods for everything i would need to run, with the high peak loads available.
What solar controller would you recommend to go with it , for 2kw of solar? What else would you recommend to go with the system?
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Re: Caravan off grid set up.

Postby davidg » Sat Oct 27, 2018 12:31 pm

Al510 wrote:What solar controller would you recommend to go with it , for 2kw of solar? What else would you recommend to go with the system?


If we say 2000watt is the amount of PV and the nominal battery voltage is 24V then we divide 2000 / 24 = 83.33A. so you should look at an MPPT charge controller that is good for "80amps" or thereabouts at a nominal voltage output of 24VDC. In a Midnite Solar it would be say the Classic 150 for instance, Outback there version, in a Victron likewise and so on.

So when looking at charging rates typical for traditional lead acid the charge rate would be 0.1C of the 10hr discharge rate. For Carbon Lead Acid which are also typically PSOC (Partial State Of Charge) cells it would typically be 0.2C of the 10hr discharge rate, so a 400AH PSOC pack the charge current would be 80A max for instance. For LiFePO4 it would be whatever the manufacturer might state as the maximum.
SPS Standalone Power System/Hybrid specialist - Store the Sun!
SELECTRONIC SPMC482-AU, 8.2kW's of Arrays
Selectronic Certified AC-Coupled Fronius 8.2kW Inverter
1900Ah 48V Bank

An OTT Genset for a house.
PVOutput Stats

Sparkys light up your life :)
User avatar
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