MPPT Charge Controller for LifePO4 Batteries

[s/v Jedi]

Originally Posted by dennisail

I just done a cost comparison for a high quality lithium setup VS an AGM setup. Note I costed various AH banks. The lithium setup with good controller etc costs about twice as much, but will have much better efficiency and more useable AH.

I will be doing this shortly for my new boat so I need to make a decision. So many things to think about. If I get 4 x 250W panels they will be 24V which means I need an MPPT controller. Otherwise I can use 4 x 200W 12V panels and use 4 x $50 ebay chargers. I can always upgrade later... I think the batteries are stuffed as well but I am hesitant to buy lithium right now as the cost will be huge and possibly not worth it as I wont be going permanent cruising for 3 years. I guess the price will come down for chargers and lithium by then. So maybe I can just get the cheap AGM 430ah bank for now...

Lithium
Solar 1000w.................$1100
Outback 80 controller....$1000
Winston 1000AH .......................$4400
Winston 700.................$3400
Winston 520..............................$2840
Winston 400..............................$2128
Misc.............................$300

Total for 700ah.............$5700


AGM setup.
Solar 1000w.................$1100
Controllers 4 x ebay......$200
AGM 430ah....................................$700
AGM 645ah....................................$1050
AGM 860ah...................$1400
Misc..............................$150

Total for 860ah..............$2900

Note per AH the lithium is only half the weight. Depends on if you use the usable capacity or not. If you say lithium has double, well you can half the weight and cost again. Depends on how you look at it.

Li: 1,100 + 1,000 + 2,128 + 300 = 4,528
LA: 1,100 + 1,000 + 1,400 + 150 = 3,650

both solar arrays are the same capacity and quality then and both battery banks equal in available power (yes with just the 400Ah Li bank) while the Li bank will last longer, gives higher voltage etc.

[downunder]

As Jedi indicated there is less than $1000 in it in your situation using your cost data as 400AH Li will provide equal if not better capacity than 860AGM.

Li should handle the non use better than the AGM also.

[noelex 77]

Battery costs vary significantly with location, so you need to the cost comparison yourself, but cheap flooded lead acid batteries often provide the cheapest option and would be a good stop gap considering your situation.

It is also worth considering high quality sealed batteries. These can have a very long life with simple well proven technology. Generally, these days lithium are a more attractive proposition to the expensive end of the LA batteries, but you do need to be reasonably technically savvy.

[dennisail]

Thanks. I know all those advantages, and the sizing thing (AGM bank needs to be bigger etc). Hence why I am considering it even though the initial cost is so high. My cost comparison was there just to get an idea. Various bank sizes are listed so you can pick which ever one you want to compare.

The costs were based on how much I can get all the stuff for in AU.

[goboatingnow]

Why people rate AgM as a good battery is beyond me

Dave

[jcapo]

+1

Marketing. :-(

[DumnMad]

Mainsail "Comparing AGM & Li Ah's/$$$ is like pitting Ronaldo against The Queen Mum in a one on one football game, not a very realistic comparison."

So is the Queen Mum the Li AH's/$$$ ? I know she had an exceptionally long life.

[dennisail]

The more I look into this, the more I find a single "high quality" charger appears to not be the best option on a boat where some panels will likely be in the shade and others will not. An outback controller will cost about $700, and to get the most out of it you will want one per panel unless they all get equal sun.

I have found these Victron controllers. They will do 200W each (400W @ 24V) and they cost $148 AUD. 4 of these will cost a little under what an outback costs. They claim ultra fast MPPT tracking. They have many variable settings.

The 75-15 even has a Lithium setting which has zero temp comp and a max of 14.2V charge setting. There is an option where you can hook it up the a computer with a USB cable and change many more settings. The manual is in my link, but the USB adjustable settings are not listed and I have asked them directly for more info on this.

Victron Blue Solar MPPT 70/15 (12/24V-15A) Solar Panel Regulator

This seems like it could be the way to go, but you must only use 200W panels.

They seem like a legit company.

http://www.victronenergy.com/contact/

[goboatingnow]

I couldn't agree more , for high voltage panels , seperate mppt makes loads of sense. Just be careful you have enough operating voltage available for given shading and derating for panel temp. If Vmp ends up just above battery levels , a simple non SEPIC DC DC convertor will not function effectively

Dave

[NahanniV]

Originally Posted by dennisail

The more I look into this, the more I find a single "high quality" charger appears to not be the best option on a boat where some panels will likely be in the shade and others will not. An outback controller will cost about $700, and to get the most out of it you will want one per panel unless they all get equal sun.

I have found these Victron controllers. They will do 200W each (400W @ 24V) and they cost $148 AUD. 4 of these will cost a little under what an outback costs. They claim ultra fast MPPT tracking. They have many variable settings.

The 75-15 even has a Lithium setting which has zero temp comp and a max of 14.2V charge setting. There is an option where you can hook it up the a computer with a USB cable and change many more settings. The manual is in my link, but the USB adjustable settings are not listed and I have asked them directly for more info on this.

Victron Blue Solar MPPT 70/15 (12/24V-15A) Solar Panel Regulator

This seems like it could be the way to go, but you must only use 200W panels.

They seem like a legit company.

Contact - Victron Energy

I do not see the "USB adjustable settings" in the product you linked or on the Victron website ??? Where are you seeing that ?

[dennisail]

Its in the manual which is available from both my links.

http://www.outbackmarine.com.au/productFile/download/87

3.7 Connectivity
Several parameters can be customized (VE.Direct to USB cable,
ASS030530000, and a computer needed). See the data
communication white paper on our website.
The required software can be downloaded from
http://www.victronenergy.nl/support-...oads/software/
The charge controller can be connected the to a Color Control
panel, BPP000300100R, with a VE.Direct to VE.Direct cable.

[NahanniV]

Thanks, I missed that.

Let us know if you find out what values can be changed.

Cheers,
JM.

[noelex 77]

Originally Posted by dennisail

The more I look into this, the more I find a single "high quality" charger appears to not be the best option on a boat where some panels will likely be in the shade and others will not.

The best controllers like the Outback use a fair bit of power to operate their complex tracking circuitry. Using one per each 200w panel is not likely to be the best option.

There are circuit designs that use less power and still track reasonably. Some of these are commercially available such as Genasun.
I think we need some more research on this topic. Will the slightly worse tracking of these simpler controllers, be compensated for by tracking each panel separately? I suspect the results will be similar, but there is little data to go on.

The cost of both approaches is similar. Multiple controllers give redundancy, but you loose some of the reported data and the set up has less adjustable battery parameters.

[dennisail]

I have no proof how much better tracking each panel separately would be, but it would appear impossible for one controller to do as good of a job as separate controllers unless the cheaper ones are truly woeful. The victrons appear to be decent and claim ultra fast tracking.

Its just going to be impossible for one controller to get the best out of a multiple array when every panel will most likely have very different operating conditions on a boat with booms, and shrouds etc shading various panels IMO. We need to remind ourselves what the whole point of MPPT is:

It is the purpose of the MPPT system to sample the output of the cells and apply the proper resistance (load) to obtain maximum power for any given environmental conditions.

When you consider that, it becomes clear that the system can NOT work as designed unless all the panels being controlled are operating under the same conditions.

http://en.wikipedia.org/wiki/Maximum...point_tracking

As for the setup, well I am waiting to hear back. As long as they do what I need the extra features of the expensive one won't be necessary anyway.

Note the charger I linked already has a setting for lithium.

[dennisail]

This seems intuitive to me, but here is is again.

Maximum power point tracking - Wikipedia, the free encyclopedia

Traditional solar inverters perform MPPT for an entire array as a whole. In such systems the same current, dictated by the inverter, flows through all panels in the string. Because different panels have different IV curves and different MPPs (due to manufacturing tolerance, partial shading,[16] etc.) this architecture means some panels will be performing below their MPP, resulting in the loss of energy.[1]

Some companies (see power optimizer) are now placing peak power point converters into individual panels, allowing each to operate at peak efficiency despite uneven shading, soiling or electrical mismatch.