New system needed

[Raul]

The monitor is a must. The rest is for my needs. Yours are diferent and you should gear up for your needs. Not everyone will need the same. My goal was off grid capabilities for weeks on end. I can do without lpg for quite some time. I can heat water, cook and space heat if needed. The batt bank size reflects the discharge rate without hampering the health. Also capacity helps with those foggy days and no ehu. The control panel enables me to switch the inverter on/off without going in the cupboard, limit shore power (ehu)down to 0,5A if needed, and control the charge rate without accessing the inverter. Paid less than 70 quid used.
The batteries, carefully used, can be my last, or last the life of the van at least. By having extra capacity, they get worked less and greatly improve on their life. I know ppl with LiFePo4 Living off grid but used sensible. Over 8 years no capacity loss, no degradation, some are using them over 10 years, and these are early calb production. The inverter is used mainly for hot water, a 400w and a 600w fan heater( not at ones), press iron, microwave, induction plate, kettle, and some tools when needed. I tend to use big power in combination with solar, not battery alone. But many times it gets used of the battery if full and know next day is sunny. Living off grid is a lifestyle not for everyone. We love it.
Forgot about the dc charger( battery to battery) , yes it charges as you drive and is a must when you’re away from grid power and no generator. I don’t carry a generator.

 

[Minxy]

Wow that’s a lot of kit. My plan is:
Solar panels up to 600w or whatever I can fit
MPPT regulator - Victron 100/50 seems right
2 x Victron 12V/110AH batteries
Possibly Victron 702 battery monitor

Why are you going for AGM batteries?

 

[Sooz52]

Why are you going for AGM batteries?

They are gel. I’ll have a little look at lithium

 

[Raul]

Have a look at ultramax, they came down in price a little. And are a UK company.

 

[autorouter]

I've put together a spreadsheet calculator that lets you put in various solar setups. You can see how long you can last when wilding, or when the weather gets bad. It's in the 'Resources' section.

Solar Power Calculator

Using the Solar Calculator Spreadsheet. This spreadsheet allows you to type in values for all the things you can change in your solar setup, and view the likely result. Deciding on the hardware for a solar power system is extremely dependent on...

www.motorhomefun.co.uk

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[autorouter]

Do you have to have 1 monitor per battery? I can’t see anything clearly about what you need for 2 batteries.

With a battery monitor you regard the habitation battery bank as one big battery. There is a 'shunt' which usually goes next to the battery in the negative return wire, so that every bit of current goes through the shunt to get to the negative battery terminals. The shunt is the point where the current (amps) is measured.

The second input is not required for 12V systems. It's intended for measuring the midpoint on 24V systems, so you know the voltage of each 12V battery, and can check if one has a problem. In motorhomes it's normally used to watch the voltage of the starter battery.

 

[Raul]

You can also use the second input for a battery thermometer so you can have temperature compensated charge, very handy. On bmv smart you use a smart temp sensor via network.

 

[Sooz52]

Ok so I don’t need a 2 input model ok. I was intending to watch the house batteries to endure they don’t drop too low.

 

[Sooz52]

The plan:

Panels:
3x100 or 3x120 (if I can find the latter to fit on a spanish site)
1x160
Added to the existing 2x50 which I’ll move to smaller roof areas.

Batteries:
2 x Victron Gel 110AH

Electronics:
Victron SmartSolar MPPT 100/50
Victron SmartSolar MPPT 100/50
Victron BWV-712 (if needed)

Electronics I’ve found on Amazon.es
Batteries and Panels on a Spanish battery site

 

[autorouter]

The plan:

Panels:
3x100 or 3x120 (if I can find the latter to fit on a spanish site)
1x160
Added to the existing 2x50 which I’ll move to smaller roof areas.

Batteries:
2 x Victron Gel 110AH

Electronics:
Victron SmartSolar MPPT 100/50
Victron SmartSolar MPPT 100/50
Victron BWV-712 (if needed)

Is that two 100/50 solar regulators?

You have to be careful when mixing panels that are not identical. If they are in parallel, the voltages must all be the same. Connecting in series doesn't help that problem much, because in that case the amps must be the same (but the voltages may be different).

For three 100W panels you could use a 100/20 regulator.
For three 120W panels it's better to go for the 100/30 model.
For three 120W panels, plus one 120W or 160W, a 100/50 regulator is best, provided the voltages match.
If not, for a single 160W panel, a 100/15 or 75/15 will be OK.

You might find the voltages of the two 50W panels are not the same as the other panels. Maybe just keep the existing regulator for those. However if the voltages are the same, a single 100/50 will handle everything in one box.

Connecting the outputs of two or more regulators to the batteries is not a problem, they work together fine. There are advantages with two or more regulators. Panel shading is less of a problem, and a single fault won't stop the whole system.

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[Sooz52]

Is that two 100/50 solar regulators?

No just one regulator but I can’t remember to edit it now.

This is just the sort of advice I need thank you.
I was just going to stick the old in parallel with the new (re previous advice not to put them in series).
I’ll be ok matching voltages of the new panels (all 12v), but I have no idea what I have with the old panels. So yes it’s simple maybe to leave the old panels on the current regulator as you suggest. Or they’re probably 12v but I have to remove them anyway to place them somewhere else so hopefully I’ll see the spec underneath.
I’ll get back to the schematic.

 

[Sooz52]

Actually I’m looking at lithium again and I see the Victron Lithium super pack 12.8/100 does not need a controller and would cost pretty much the same as 2xgel 110ah plus the mppt controller... and I wouldn’t need the battery monitor either as it’s all in the Bluetooth app. Thoughts?

 

[Sooz52]

That’s what I got on my van, two panasonic 295w, total 590w with a victron 100/50, a bmv 700 batt monitor, a GX digital control panel, a1600va/12v inverter charger and a victron Orion 12-12/30 dc charger from the alternator and 400ah LiFePo4.

That really is a super sized LiFePo4 - how come you went so large? Looking at how they work wouldn’t a 100ah or 200ah work in this set up?
Also how come you have a controller and monitor if they seem to do this themselves?

Edit - maybe it’s just the victron super packs that don’t seem to need anything else - I like this idea! I hope that’s correct, I feel a call to a specialist may be needed.

 

[Minxy]

Wissel ... any comments you can add ref lithium etc?

 

[autorouter]

I’ll be ok matching voltages of the new panels (all 12v), but I have no idea what I have with the old panels.

Solar panel voltage - the voltage on the input side of the regulator, not the output - is not the same as battery voltage. The solar panel voltage is at least 4V higher than the battery voltage, and usually a lot higher. It will be written on the panel label, or in the panel spec list.

Of the various voltages, Voltage at Maximum Power (Vmp) (aka Peak Power Voltage) is the relevant one, but the Open Circuit Voltage (Voc) is not much different. Typically they are between 18V to 40V, but those designed just for 12V are typically 18 to 28V.

Edit: If you're keeping the existing regulator, you could connect the 160W panel to the second input (PF2). I wouldn't worry that it's over the 150W limit - on the rare occasions it exceeds the limit, it will simply waste the extra power, with no damage to anything. The inputs PF1 and PF2 are separate, so the voltages don't need to match.

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[autorouter]

Also how come you have a controller and monitor if they seem to do this themselves?

Edit - maybe it’s just the victron super packs that don’t seem to need anything else - I like this idea! I hope that’s correct, I feel a call to a specialist may be needed.

Lithium batteries need more care than lead-acid ones. The individual cells within the battery can go out of balance and cause problems. Because of that, lithium batteries need a 'battery management system' (BMS) to rebalance the cells, and cut off the current if the voltage gets too low/high or the charge/discharge is too high.

These Victron 'Superpacks' are lithium batteries with a built-in BMS. Ordinary Victron lithiums need an additional BMS. That's what they mean when they say 'no additional components needed'. Unfortunately you still need a solar regulator and a battery monitor.

 

[Sooz52]

Unfortunately you still need a solar regulator and a battery monitor.

Darn, ok thanks. Back to gel then otherwise it’s too expensive

 

[Sooz52]

Victron or Votronic? The former seems a lot more expensive... worth it?

It looks like I’m going for 4x120w panels with new MPPT charger controller, 2 per input channel in series, and leaving my current 2x50 with existing MPPT in place. I called Sunstore a couple of days ago and he said balance was really important so 3x120 + 160 wouldn’t work as well. He also said series was much more effective than parallel...

I don’t understand the limits of the controllers though - for instance this is the largest Votronic, max 430wp (watt power?).

VOTRONIC - MPP 430 Duo Dig.

Innovative Elektronik für den mobilen Einsatz

www.votronic.de

I know 4x120w will never actually make 480w, but I must be looking at it wrong... do I have to do some calc to get from w to wp? The guy at the shop mentioned voltage was key here.

This is the spec per new panel:
Panel Size 550mm(w) x 1450mm(h) x 35mm(d)
Weight 10kg
Peak Power: 120w
Open Circuit Voltage: 23.4V
Short Circuit Current: 5.45A
Power Allowance Range: 3%
Max Power Voltage: 22.0V
Max Power Current: 5.45A
Max System Voltage: 1000VDC
Number of Cells: 44

 

[Richard n Ann]

Power is measured in Watts ??

Therefore 420 Watts of power. Normally written 420w ?

 

[Sooz52]

Solar panel voltage - the voltage on the input side of the regulator, not the output - is not the same as battery voltage. The solar panel voltage is at least 4V higher than the battery voltage, and usually a lot higher. It will be written on the panel label, or in the panel spec list.

Of the various voltages, Voltage at Maximum Power (Vmp) (aka Peak Power Voltage) is the relevant one, but the Open Circuit Voltage (Voc) is not much different. Typically they are between 18V to 40V, but those designed just for 12V are typically 18 to 28V.

So my new panels are 23.4v, voltage Max on the Votronic MPPT 430 is 50. I still have no idea if I can connect 4 of them up to it...

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[Sooz52]

Power is measured in Watts ??

Therefore 420 Watts of power. Normally written 420w ?

Ok thanks. So when people have more than 420w in panels what charges / controllers do they use?

 

[Sooz52]

For three 100W panels you could use a 100/20 regulator.
For three 120W panels it's better to go for the 100/30 model.
For three 120W panels, plus one 120W or 160W, a 100/50 regulator is best, provided the voltages match.
If not, for a single 160W panel, a 100/15 or 75/15 will be OK.

How do you get to those recommendations?

 

[Raul]

In therms of PV , Wp means watts peak, as in max installed power.

 

[Richard n Ann]

In therms of PV , Wp means watts peak, as in max installed power.

Yes that's probably a better explanation ?

 

[Sooz52]

The current list:

Panels:
4 x new 120w - connected to new MPPT controller
Added to the existing 2x50 which I’ll move to smaller roof areas - will stay connected to the existing MPPT controller

Batteries:
2 x (Victron) Gel 110AH

Electronics: (not sure of sizing)
either Victron SmartSolar MPPT 100/50 plus BWV-712
or Votronic MPP 430 Duo Digital plus LCD Battery Computer 200

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[denisejoe]

Have you measured the space you have for batteries?thats where you need to start and do you have an inverter to charge your laptop

 

[Raul]

In regards to your question about the LFP size. I did mention that one of my requirement is a discharge of 60-80A and need the size to cope with the discharge rate. If the bank is to small it will be discharged over the recommended rate( to high) and kill them prematurely. The discharge is limited by the internal bms as well. Also the storage capacity is needed for a week of dull weather off grid. The fridge( compressor) takes 0,3-0,4kWh daily, other items like fan heater, extractor are item used daily that adds up. Pump is intermittent.
In the end I calculated my total daily needs, times 5 to stretch it for five days with little solar harvest. Also I use the LFP on a very conservative voltages to prolong life. That means, I will not be using the entire 400ah capacity, more like 80% of it. So a 320ah at 12,8v gives me a 4kwh of usable energy, about 800wh per day for five days. IF needs must, I still have a reserve of 10% left that I prefer to never access it. The batt monitor helps me to keep track of what’s going in and out, and what I got left to play with. It is very accurate if set and fitted right, and helps me to NOT rely on bms. The BMS is a last defence mechanism, not used for everyday cycling. If you abuse the bms all the time, eventually something will fail and can destroy the batt. or leave you without power when you most need it. LFP, used sensibly and clever integration, could be your last battery you’ll ever need for that van. I know ppl with off grid homes in excess of 8 years of use, without any degradation. These ppl are experienced and run conservative voltages, ( below manufacture’s recommendations) and derate capacity for long health.

 

[Raul]

Ditch the gel and get half of that capacity in lfp. You don’t need bmv 712, a 702 will suffice.

 

[Raul]

Try to stay with one manufacturer that offers a better integration for future changes/ additions. I’m not knocking votronic, but, victron has endless options of integration that work together seamless.

 

[autorouter]

How do you get to those recommendations?

The idea is not to exceed the voltage and current limits. For a 100/50 regulator, 100 is the voltage input from the panels, and 50 is the current (amps) output to the batteries.

If the panels are in parallel - as usual on motorhomes - the voltage will be the same as a single panel voltage of 20 to 40V, so voltage is never a problem.

To work out the current, take the nominal panel watts and divide by the BATTERY voltage, then take about 70 or 80% of this if in Europe with the panel flat on the roof.

Example: three 120W panels: 360/12 = 30 amps, 80% of that is 24 amps. So if the choice is a 100/20 and a 100/30, it would have to be the 100/30.

Don't be misled by the 'max power current = 5.45A'. That's the PANEL output current, at the max power voltage of 22.0V. When the regulator steps down the voltage to feed the battery, it steps up the current to keep the power (volts x amps) the same.

So a 100/30 regulator can manage about 400W of panel if feeding a 12V battery, but can manage 4 x 400 = 1600W of panel if feeding a 48V battery. That's one reason for using higher battery voltage on a house installation, where the only thing connected to the battery output is the inverter.

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