Finally decided to power up the van, since we now intend keeping it for a bit longer but not going to spend big bucks on this one. The new van is still in the near future and that will be set up at build.
We have 1 x 115ah AGM, but will be putting a 2nd one in as well.
Would 1 x 120 panel be enough to keep the system going or should I put up 2 panels @ 120.
Would we be better of with a 24vt panel system?
Will want to put in an MPPT controller.
Basically everthing is 12vt,
What we want to run is the just basically the lights, the Telly (which is converted) + charge up the lappy battery.
Hot water is gas only
Fridge is 3 way.
I always reckon an easy way is to match the battery Ah with the Solar Panel Watts. So, 2 x 115=230 Ah, so I would recommend about 230 Watts of solar, (two panels)
For lead acid batteries Jon has the numbers about right, match the watts to the Ahs.
A few things to thing about before settling on an MPPT controller.
If you go 24v and MPPT and anything goes wrong with the controller you have nothing, with 12v into a 12v battery you can at least rig it up with an on/off connection till you can get the controller problems sorted.
If you want to use any secondary charging system like alternator or mains or a mains charger via an inverter powered from the tow vehicle battery you can't use an MPPT controller, they just don't play well with others. So if you go MPPT, it's either that only or turn it off and charge via the other method, you can't have both. PWM control doesn't have that problem.
Don't be fooled by all the MPPT hype, the gains are small, 10% at best really, 230w x 70% for a PWM controller, about 160w but a few real life examples over on the CF have come up with better than 77%, but for the argument we'll stick with 70%.
230w x 80% for an MPPT controller, about 184w, that's 24w improvement. The average charging AGM battery voltage is around 13.6v, 24w divided by 13.6v = 1.76 amps. The aim is to have the batteries end the boost cycle and go into absorption mode by lunch time, a 5 hrs peak sun day says half of that is 2.5 hrs. 1.76 amp x 2.5 hrs = 4.4Ah. Once an MPPT controller goes into absorption mode it becomes a PWM controller anyway, that's the way they control over voltage so any benefit has gone.
A PWM controller can extract around 70% efficiency, that's 160w, divided by 13.6v = 11.76 amps. For a 2.5hr charge till absorption mode is reached that 4.4Ah gain from an MPPT controller means the battery will reach absorption mode 22 mins earlier than the same panels using a PWM controller..... is it really worth it?
Don't believe the B/S about them starting charging earlier or keep charging later than a PWM controller, it's nonsense, the same as them working better in poor weather, that control gear to converter from one voltage to another requires power to run it, that's some of the power the solar is generating, the PWM controller will still be charging well after the MPPT controller can no longer power itself and shuts down, the PWM controller will start charging as soon as any solar charge is available, the MPPT unit needs enough solar power to power up the circuitry to start working, logic says it's always going to be behind the eight ball in poor conditions.
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
Thesolar regulator will connect to the battery as usual, a PWM regulator will share the charging duties if the other unit is connected at the same time, no problems. don't forget to use heavy gauge cables from the panels all the way to the batteries and put a 50 amp fuse in the positive lead at the battery. Best to use 5ag fuses like the ones the car stereo people use because they have gold platinf and a larger surface area so less likely to suffer heat build up due to high resistance joints.
if you do a trip around the car stereo mobs or even a look through evil bay you will find kits with the fuse and big cable for mounting amplifiers etc, that would be enough for 230w of solar, you might need to go to Jay Car to get a length of negative cable, the one in the kits is very short.
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
even better than the 5ag fuses are the "short stop" mini breakers. They come in three types, manual reset, semi automatic reset and automatic reset. I like the manual reset type. http://www.burnstines.com/power/circuit ... i-breakers
I replaced the blade fuses on my set up with these when one of the blade fuses melted. The constant high current caused it to melt.
IMG_1580 (Copy).JPG
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The only problem there is when the positive lead is disconnected and then reconnected, the solar regulator goes into reset and to the default settings on a lot of the cheaper type regulators, a circuit breaker auto resetting would give the operator any clues that things had changed, suddenly the AGM's are being charged as flooded cell batteries and get cooked. The Plasmatronic series have a real issue with the positive circuit being interrupted while the solar is still passing through the regulator, they loose the plot basically Then they require a complete shut down reboot to get going again. That's why I like the fuse idea better, you know it's blown and you know you need to find out why and reset everything.
It's not an issue with the Plasmatronics stuff running through a solid state relay, the controller is powered through a separate wire so it stays alive and in control.
The melt fuse and holder is a typical scenario with anything much more than 15 amps running through them, no idea why they make 50 amp fuses for them, the holder catches fire long before 50 amps can be handled. The whole fuse box often turned into molten mess just by putting 100w globes in the headlights of a VL Commodore
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
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
Last Resort asks the question I was about to ask and Terry gives the answer.
Great service.
Thanks to both
Hi Baysidetas, I must have missed your arrival so welcome here from me as well. I asked Terry a question once upon a time and he was gobsmacked. That must have been the first time ever.
Queen of the Banal & OT chatter and proud of it. If it offends you then tough titty titty bang bang.