12 Volt or 24 Volt?

[native pepper]

Well you've lost me with all that, does that mean you still use float etc. I tried using relays for shutting off charge when a cell reached 3.5v, but found there was still the float etc to contend with. So after the Stone kids started ignoring my questions, decided to get lifepo4 chargers built for the buying group Bob set up down here and bought a good supply of the equalisers as well.
The cell equalisers we are using move charge from one cell to another to compensate, rather than with balancers just bleed the higher cell. The newest inverter I have has an outlet for charging usb things, is that what you mean, or are you saying current inverters can't charge the higher and lower energy requirements at the same time. We charge phones, use tv, fridges and induction cookers all at the same time, so am a bit confused as to your meaning in that regard.

If i had the ability, would love to design a charge controller that incorporated equalisers and was fully programmable, but sadly have a blank space where the maths etc of electronics should sit. Even did a course in computer and electronics technology to try to get my head around it and after 3 years, hadn't got past the first set of maths, because it just disappears from my mind. Yet if I watch someone make up electronics, can then do it myself and have built a few projects years ago, including a 300w inverter back in the 1980's, which I still have and it still works. Got boxes of components, which have been bought or given to me to make things, but most times, just look at them with a blank stare, My mate used to say, now you've seen me do it, here's the stuff to do it yourself and then he would end up fixing the mess I created later on.

[T1 Terry]

Yes, there is still a float mode but it really only replaces what is used while the sun is up, when the cells are full they are full, so no charge goes in till the voltage drops.
The inverter issue is the 25w or so standby or light load current wasted to power up a 3000w inverter to produce 25w to charge the phone, some are even worse than that, the idea is to have the inverter start up in stages so only a minimal percentage of the total load is wasted in keeping the inverter running.

T1 Terry

[Kappy]

Back in the mix, recently I acquired 14 x 100 watt 12 volt panels seemed like a goo idea at the time better utilization of space than 1 large panel.

I had sorta decided to change to 12 volt system, currently my rig was set up to run 24 volt.

After some hand's on with a big rig owner feel I'm convinced to stay with 24 volt and wire my 12 volt panels, in series to give 700 watts @ 24 volts and approx 35 to 42 amps.

Already have a Victron BMV700 monitor, so now have to decide on what controller to use MPPT or PVM and then a new 24 volt PSW invertor.

Its been allude to me that say 2000 watt invertor with 2 x 240 v outlets is shared so each plug is only 1000 watt....................any true to this???

At this stage gonna stay with AGM's and increase from 4 to 6 maybe 8 batteries potential 300 to 400ah supply.

Slowly getting my head around all of this until someone comes along and mess it all up again.

Still have 3 x 200 watt 24 volt panels that I may set up on my trailer.

Cheers

[BruceS]

Make sure the controller can handle the 2 in series. Check the specs before you buy the controller.

[El Gringo]

Back in the mix, recently I acquired 14 x 100 watt 12 volt panels seemed like a goo idea at the time better utilization of space than 1 large panel.

I had sorta decided to change to 12 volt system, currently my rig was set up to run 24 volt.

After some hand's on with a big rig owner feel I'm convinced to stay with 24 volt and wire my 12 volt panels, in series to give 700 watts @ 24 volts and approx 35 to 42 amps.
Cheers

Sorry but that doesn't sound right to me.
Watts are watts and don't change - at least that is my understanding.
You should still have 1400 watts of solar energy, if this was @ 12v then you would have 1400 / 12 = 110 amps (approx)
The only thing that changes for you is the volts, so you now have 1400 / 24 = 55 amps (approx)
So you may need to consider this when buying a controller to suit.

Ps, I'm no expert by any means, so it would be good for somebody to confirm this or shoot me down in flames...

Cheers,

[Wilbor]

No you are spot on, watts are watts.

I have 1050 watts in series. Comes down at about 140v and about 8 or so amps through a Midnight Classic 200 pv controller and goes out at up to 66amps at 12v

I could be mistaken but I don't think a PWM controller will handle that voltage conversion

[T1 Terry]

On the money there, add the Vmp voltage together for the 2 x 12v panels you want to connect in series and if the figure comes to more than 34v you should use an MPPT controller that can handle all the open circuit voltages added together as MPPT controlers require all the panels in series to work properly. Generally 12v panels have an open circuit voltage of 21v so a controller that can handle 210vdc and an output of 50 amps would be required. Not cheap for a unit that will actually work but the likes of a genuine Midnight Solar or Outback Solar unit will do the job well, don't get caught with the Chinese knock offs, they don't work near as well.
No matter what those that have no idea of what they are talking about say, you can not expect 2 lower quality MPPT controllers to work together on the one battery pack, I have a few on the shelf removed from systems that didn't work no matter what Victron tried so if they couldn't make it work then there is little chance a few keyboard heros could eh They will work together till one reaches the end of boost, then the other unit/s simply goes into idle mode so much of the solar input is lost until the return to boost voltage point set in each unit is reached.
MPPT units that connect in master/slave configuration do work, but at over $1,000 each I can't see the value/sense in going down that path.
I have quite a few AGM batteries here with maybe a few yrs left in them if you want to set up the system and get a feel for it before upgrading the lithium batteries. The lithium batteries may be more expensive initially but I don't know of anyone who has gone from lithium back to AGM batteries by choice

T1 Terry

[Kappy]

Geez I'm confused again the plan is to wire 2 x 12 volt panel in series giving me 24 volts.

According to the manufacturer specs the VOC is 21 volt and the imp is 5.72 amps.

As I understood 2 x 100 watt panels in series remains 100 watts as does the amps stay at 5.72, hence total amperage between 35-42 amps ???

So I gather because of amp I need something like this......http://www.ebay.com.au/itm/Outback-Flex ... SwImRYdAou

Can someone answer mu query regarding 2 outlets on an invertor, if only one outlet is used is the output still shared.

Cheers
Kappy

[T1 Terry]

The unit you mentioned by the time freight and PayPal currency exchange chargers are added will be up around the $900 plus mark and will only handle 150vdc, 21vdc x 10 panels is 210vdc. Watts are watts so they add together, 100w @ 12v will deliver around 5.7 amps, 200w @ 24v will deliver 5.7 amps or 11.4 amps @ 12v.
If you attempt to connect 2 x 12v panels to create 24v and connect 5 sets like this in parallel to the MPPT controller then any panel that is shaded will mean the loss of that panel plus its partner, 200w loss with each panel shaded. The pair of panels that put out the most will be the dominant pair and the others will either try to keep up or just stop putting much into the charging side, such is the way with an MPPT controller. With all panels in series the bypass diodes allow current to bypass the shaded panel so only 100w is lost for each shaded panel and the MPPT controller looks at the output of all the panels in the chain, not just the most dominant pair.
If you thought going 24v was going to be easier than 12v you are wrong, no idea why anyone would think going 24v rather than 12v in this day and age was an advantage is beyond me but there you go. I am just finishing off an upgrade on an off grid house that has 700Ah of lithium @ 12v, now runs 2 x 3000VA Victron inverters in parallel to power their new 7kW split system air con as well as everything else in the house. I have just finished fixing the poor wiring done by solar professional installers and the system is putting out just on 80% efficiency using a Dingo 20/20 to control 4 x 100amp solid state relays. 2720w of solar putting out 2200w @ 14v is good in anyone's books, considering the system is made up from 8 x 200w mono-crystalline panels, 6 x 140w poly crystalline and 4 x 120w poly crystalline panels it is way beyond anything that an MPPT controller could achieve.
Don't believe all the hyperbole and spin sellers pump out about how much their controller will supply, no one actually has a system that will meet the requirements to achieve their claims unless they pack their solar panels in snow yet have perfect alignment to full sun at all times with absolutely no shade at all..... and manage to not have the snow melt

T1 Terry
The bit about the multiple 240vac power outlets, good inverters have all the outlets wired in parallel, cheap nasty buggers don't as they are actually multiple small inverters in the same body. Really good inverters don't have power point outlets at all as they are designed to be hard wired into the system.... hope that helped

[Kappy]

The unit you mentioned by the time freight and PayPal currency exchange chargers are added will be up around the $900 plus mark and will only handle 150vdc, 21vdc x 10 panels is 210vdc. Watts are watts so they add together, 100w @ 12v will deliver around 5.7 amps, 200w @ 24v will deliver 5.7 amps or 11.4 amps @ 12v.
If you attempt to connect 2 x 12v panels to create 24v and connect 5 sets like this in parallel to the MPPT controller then any panel that is shaded will mean the loss of that panel plus its partner, 200w loss with each panel shaded. The pair of panels that put out the most will be the dominant pair and the others will either try to keep up or just stop putting much into the charging side, such is the way with an MPPT controller. With all panels in series the bypass diodes allow current to bypass the shaded panel so only 100w is lost for each shaded panel and the MPPT controller looks at the output of all the panels in the chain, not just the most dominant pair.
If you thought going 24v was going to be easier than 12v you are wrong, no idea why anyone would think going 24v rather than 12v in this day and age was an advantage is beyond me but there you go. I am just finishing off an upgrade on an off grid house that has 700Ah of lithium @ 12v, now runs 2 x 3000VA Victron inverters in parallel to power their new 7kW split system air con as well as everything else in the house. I have just finished fixing the poor wiring done by solar professional installers and the system is putting out just on 80% efficiency using a Dingo 20/20 to control 4 x 100amp solid state relays. 2720w of solar putting out 2200w @ 14v is good in anyone's books, considering the system is made up from 8 x 200w mono-crystalline panels, 6 x 140w poly crystalline and 4 x 120w poly crystalline panels it is way beyond anything that an MPPT controller could achieve.
Don't believe all the hyperbole and spin sellers pump out about how much their controller will supply, no one actually has a system that will meet the requirements to achieve their claims unless they pack their solar panels in snow yet have perfect alignment to full sun at all times with absolutely no shade at all..... and manage to not have the snow melt

T1 Terry
The bit about the multiple 240vac power outlets, good inverters have all the outlets wired in parallel, cheap nasty buggers don't as they are actually multiple small inverters in the same body. Really good inverters don't have power point outlets at all as they are designed to be hard wired into the system.... hope that helped

I hear the reference to 12V compared to 24V, is each panel really going to deliver the full VOC?

So running 14 x 12 volt panel at 21 VOC equals 294 vdc and approx 80 amp, is there even a single controller that can handle that.

One of my concerns was the thought of having to change all my internal low voltage wiring , which I may add is currently running 12 volt DC from 24 v to 12 volt convertor.

May have to arrange a time to give you a ring to discuss you comments regarding used AGMs.