Self Sufficent for freedom camping, what do I need?

Discussion about any electrical topic except 240 volts. Solar, converters, inverters, lights, battery chargers, etc
User avatar
JohnM
Posts: 69
Joined: Tue Sep 06, 2016 6:50 am
Location: Burpengary

Re: Self Sufficent for freedom camping, what do I need?

Post by JohnM »

Hi Barry,
I among others, have tried various regulators, chargers and inverters, with a diversity of results, to start with regulators.
PWM V MPPT. I had no success with MPPT (various makes) charging the batteries, the main problem appears to be compressor type fridges, when they cycle off the reg sees the surge and reads this as fully charged, so goes to float mode and will not resume bulk charge until the batteries drop below 12.8v or the big light goes out, when it resets the next morning. Tried various regulators and settled on a simple programmable single stage PWM type as being the best for my use. When not in use the bus is parked in the back yard, I leave the fridge turned on, with a few bottles of liquid inside, and turn the Reg back to 14v the batteries, still float by midday, and then when we are traveling I set the reg to 14.5v.
The next problem I had was an all in one inverter charger, which was in fact a UPS type of system didn't last long, among the problems were the fact it was a, MPPT charger, with their inherent problems, then after about 12 months it died. the later models were branded not recommended for mobile use.
After that experience I decided that separate units with individual control were the better option.
I have a cheaper 60A ac charger which can be turned on as required, and a 1.2 KVA genny for those awkward moments.
I also have a Redarc BCDC 20 which is permanently connected, through the ignition,
It is normally not recommended that units with different charging regimes are connected simultaneously, however I don't find any conflict between the two, the Redarc and solar will work together while driving ( I have seen in excess of 50 A input while driving).
Life is a trip, to be enjoyed!
John M
native pepper
Posts: 1357
Joined: Mon Feb 23, 2015 8:21 am
Location: Tasmania
Has thanked: 5 times
Been thanked: 4 times

Re: Self Sufficent for freedom camping, what do I need?

Post by native pepper »

Used cheap ebay mppt controllers for many years and never had a problem with them, same with my dedicated lifepo4 mppt controllers, they work excellently and they are not ebay but specially build and not that cheap. We run 2 compressor fridges in the bus, 2 freezers and fridge in the house, all charged by mppt controllers.

When we had gel exclusively in the bus, the mppt chargers out performed the pwm dramatically when on the road. The difference may have to do with system setups, wiring and number of circuits in the system. I have 3 circuits in the bus, 1 and 2 are 12v for lights and 12v accessories, each side of the bus is on a separate circuit. Three is for 240v stuff and can be switched from the inverter to mains.
User avatar
T1 Terry
Posts: 15965
Joined: Fri Nov 23, 2012 3:44 pm
Location: Mannum South Australia by the beautiful Murray River
Has thanked: 50 times
Been thanked: 30 times

Re: Self Sufficent for freedom camping, what do I need?

Post by T1 Terry »

baysidetas wrote:I would be interested in advice re. solar regulators/chargers eg MPPT or PSW. I will have 400 watts of solar initially.
Two 200 Watt panels (V@ PMax 18.2v, V o/c 22.0v, Current @ PMax 10.99A and I may instal another 2 panels at some time in the future.

Battery capacity until I can relocate them to a larger and more accessible place.

Can I get a controller/regulator that will automatically switch between solar, MH alternator , portable generator.
Any recommendations and would I need to get a separate monitoring unit?

Barrie
My recommendation after 5 yrs of doing these jobs for other people and probably over 10 yrs of using them myself, unless you have a separate battery pack for each MPPT type controller and that controller has separate battery voltage sensing, avoid MPPT like the plague for 12v or 24v battery charging. They are more trouble than good and the possible gain if you did get it to work right is so small compared to a properly set up PWM controller the down sides far out weigh the good.
The very best set up in my opinion is a Dingo 20/20 driving solid state relays, the solar wiring goes directly to the battery compartment where the solid state relay is mounted, the Dingo goes where ever you want it and is connected by small gauge wires to the battery and solid state relay. The relay does all the work and is rated @ 100 amp each and you can run as many as you like, the Dingo only does the control part remotely to the solid state relay. This solves the long heavy cable runs through interior walls, shortens the solar cable run length and makes the system open end as far as solar capacity and it can control any other charging method at the same time, just mount a solid state relay/s for each charging source, the Dingo will control them all. It also makes the whole system future proof in regards to battery choice, it will work just as well with lithium batteries as it works with lead acid batteries because you get to program in the charging parameters, not the manufacturer who thought they knew better :roll:
As far as a battery charger, as I have said else where, the Projecta IC5000 is a great unit, not the cheapest but by far the most reliable and does have separate battery voltage sensing. The cable for this is threaded through the original charging cables but easy enough to fit new cables inside the charger if you need to change the main cable length or connect it into the system some where other than the battery terminals as it is the battery voltage the charger needs to see, not the system voltage which is affected by loads switching on and off.
The projecta IC2000 has UPS switch through so it can automatically switch from inverter power to shore power whether it is from a generator or mains supply, but the down side is it will limit supply to 2000w no matter if it's mains supply or inverter supply. The fix is a 3 way rotary switch to select the power supply you are after.
There is a 3,000w/9,000w peak inverter/charger that is also switch through commonly referred to as a W7 type, 3000 9000 inverter charger typed into ebay will find a few of them. These things are as tough as old boots, cheap so the QC is rather poor but you either get one that works well or one that dies within a few mths or straight out of the box, the odd one lasts for 13 mths and just out of warranty, but most just seem to work without problems. Their down side is a very high stand by current, so they can't be left turned on unless you have heaps of battery and solar to make up for the waste, up to 1000Wh over a 24hr period, savage, but turn them on when you want the microwave or air cond or induction cook top and they are great value for money.

T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
User avatar
T1 Terry
Posts: 15965
Joined: Fri Nov 23, 2012 3:44 pm
Location: Mannum South Australia by the beautiful Murray River
Has thanked: 50 times
Been thanked: 30 times

Re: Self Sufficent for freedom camping, what do I need?

Post by T1 Terry »

Missed the monitor part, must have been so long even I fell asleep :lol: My recommendation would be the Victron 700BMV, avoid the 702BMV as the added complication stuffs up more often than it helps, if you need to monitor 2 batteries buy 2 monitors, don't expect one monitor to do both jobs, it becomes a compromise that isn't worth the added false alarms it often creates

T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
baysidetas
Posts: 61
Joined: Tue Dec 18, 2012 10:24 am

Re: Self Sufficent for freedom camping, what do I need?

Post by baysidetas »

In answer to question by BruceS my house battery comprises two FullRiver 6v 224 amphours nominal capacity (in series connection).
They have a fairly hard life and I expect they will need replacing in the not too distant future.

Barrie
native pepper
Posts: 1357
Joined: Mon Feb 23, 2015 8:21 am
Location: Tasmania
Has thanked: 5 times
Been thanked: 4 times

Re: Self Sufficent for freedom camping, what do I need?

Post by native pepper »

Suppose all the off grid installers, users and travelers I know must be wrong in using mppt controllers, yet don't know one who has had trouble with their systems. We have a regular stop where it is fully shaded during summer and the difference in input from the mppt compared to the old pwm we used to have, is enough to make them worthwhile and as none has caused any problems ever, find it hard to believe this century technology is worse than last centuries. We only changed to mppt when the pwm charger collapsed and on good advice, the results are excellent, but everyone to their own approach.

My lifepo4 systems is very simple, dedicated lifepo4 mppt solar chargers, cell equalisers and that's it. Never have to balance them, they all just work, no more cell balancers, relays to compensate for using lead acid controllers and no expensive brand name lead acid crap, just simple cheap systems that work. Anyone can install them and the only thing that may be hard to get is a dedicated single stage mppt lifrepo4 controller, but they are available.
User avatar
JohnM
Posts: 69
Joined: Tue Sep 06, 2016 6:50 am
Location: Burpengary

Re: Self Sufficent for freedom camping, what do I need?

Post by JohnM »

I know that MPPT works well in domestic systems, both grid tie and off grid systems, I have been told umpteen times , how much better they are,by people that should know, which is why I persevered with them so long.
All I know is that in my case my batteries never became fully charged, what I perceive to be the problem may not be correct, but it is what I see. I know that a 12v DC system is totally different to, to a 240v ac system driven through an inverter, I will admit that the problems I have encountered may be from the way that I have set up and wired the system.
I have several books on 12v wiring, such as the 12v Bible, I wired my bus as I would a boat, that is, all electrical circuits are stand alone coming back to a common earth "Buss" at one end, connected by a short 10 mm link to the Battery, and a fuse connection at the other, with the exception to the inverter which is in a stand alone circuit, as are a couple of Anderson plug circuits, the earth side of the battery is connected to the chassis of the vehicle through a common earth stud with motor batteries, which is needed for a DCDC charger to work, Each circuit has been checked and double checked for any leakage to the body / earth.
As I said MPPT doesn't work for me, I know that a simple PWM system does work, and that any loss of efficiency can easily be compensated, for many times over, at a fraction of the cost by the simple expediency of adding another panel, and every thing works as it should without having to continually check the monitor.
Life is a trip, to be enjoyed!
John M
bagmaker
Posts: 886
Joined: Sun Jan 20, 2013 4:56 pm
Location: Victoria

Re: Self Sufficent for freedom camping, what do I need?

Post by bagmaker »

as I understand it, general rooool of thumb- use MPPT for high voltage solar and KISS for low voltage -i.e. -panels under 20v max.
But always happy to hear the debate :D
User avatar
T1 Terry
Posts: 15965
Joined: Fri Nov 23, 2012 3:44 pm
Location: Mannum South Australia by the beautiful Murray River
Has thanked: 50 times
Been thanked: 30 times

Re: Self Sufficent for freedom camping, what do I need?

Post by T1 Terry »

It only requires a read through the manufacturers literature and they will tell you that MPPT does not work well if the panels are subject to high temperature as the Vmp (Voltage maximum power point) drops as the panel temperature increases above 25*C by roughly -0.5% per *C over 25*C. Id imagine the effect would not be as great in Tassie, but here on the mainland panel temp in full sun climbs to around 70*C in the full summer sun. 70 - 25 = 45 x 0.5% = 2.25 volts. This means the STC figure of 17.5v shown on the rear of the panel when at 70*C will be 17.5 - 2.5 = 15v. As the maximum voltage for lithium battery charging is 14v and likely minimum voltage charging lithium batteries is most likely to be 13v, the max differential the MPPT controller has to work with is 2v or a 0.15% differential.... less the energy used by the MPPT controller to converter the 15v down to 13v and increase the amps by .... less than 0.15%.
Looking at the same thing when lead acid batteries are used and the figures are even worse, sensible people will not discharge their 12v batteries below 12v, when the start recharging the battery voltage is not 12v but a min of 12.8v due to the high internal resistance of lead acid batteries. Within an hr that voltage will be higher than 13.8v and the requirement for flooded cells is 14.8v to reach fully charged, 14.4v to 14.8v for AGM batteries and this voltage needs to be held for a a few hrs at least to effect an absorption charge period. Not much differential available between 14.8v and 15v and the losses within the MPPT controller while attempting to extract anything will be greater than the losses through a PWM controller.

Now let's look at the requirements for current to flow from the solar panel and into the battery, if it were 13v at both ends no current would flow, just like water in a pipe, the difference between the in and the out will effect the rate of flow, 15v into a 13v battery terminal voltage will be sufficient to overcome some cable resistance, so the charging voltage must be higher than the battery voltage for any charging to occur and remain high enough even after the cable resistance is taken into account.

When will an MPPT controller be an advantage?
If the cabling between the solar panel and controller is under sized there will be serious resistance and this will greatly affect battery charging as the voltage that actually reaches the battery is reduced by this cable resistance, not much difference between the battery voltage and the solar voltage at the end of the cable, so very slow charging. If the panels are rewired to a series connection rather than parallel connect the voltage is greatly increased but the amps greatly reduced, this will be pushed far easier through the undersize cables to the MPPT controller, it then reduces the voltage and increases the amps and supplies that to the battery, the result is much faster charging.
This does not mean an MPPT controller is a better form of solar regulator, what is does mean is it can be used as a work around for poor wiring, if the wiring is done correctly there will be no advantage in using an MPPT controller.
Some claim that higher voltage solar grid connect panels are cheaper and better panels for RV use, a rather questionable claim, the physical size of the panel would make placement difficult on most RVs and limit the number of panels that could be fitted. Shading across a panel will result in virtually a total loss of output, the effect on 3 x 100w panels would be the loss of 100w on the shaded panel, the same shade across a 300w panel would result in no output, that doesn't sound like a good choice for an RV as there is any number of possible shade issues due to the number of different places RVs will be parked. It's not like cutting down trees that shade a house roof top panel or careful placement o put them in non shaded areas, shading is just one of those things that can happen when parked in a freedom camp spot and maybe only for part of the day. The ideal set up for an RV as far as I see it is the max number of smaller panels all wired in parallel will reduce the shading effect, correctly wired will minimise resistance in the cabling resulting in a solar set up that produces the best possible output throughout the day. The important thing to keep in mind, spot input reading are of little value, it is all about the total days harvest that counts.

T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
BernieQ2
Posts: 8257
Joined: Thu May 07, 2020 7:57 pm
Has thanked: 13 times
Been thanked: 25 times

Re: Self Sufficent for freedom camping, what do I need?

Post by BernieQ2 »

My batterys have been disconnected for the last 3 weeks I just at this time 3.20pm connected the up they were sitting on 12,4 with a phantom -o.6amp daw haven't found the culprit yet . the sky is hazy from farmers burning off smoke every where .
I use a MPPT solar controller (40amp)when I just came out of the bus it was putting 13.8 amp's in and SOC was at 68% .
There is nothing on except the -o.6amp . 600w on the roof .
Outside temp is 34degrs.
I will look again in about a hour from now .
Bernie .

Return to “Low Voltage Electrical”