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That is NOT a contradiction, it is a misinterpretation on your part.
If you are going to FLOAT a Lithium battery, do so at less than 100% SOC. It is that simple. That is where the 3.35 to 3.45 volt range comes from. Both 3.35 to 3.45 are less than 100%. It may take as much as 3.55 vpc.Last edited by Sunking; 07-20-2016, 03:41 PM.MSEE, PEComment
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Again you are misinterpreting what you are reading and being told. The Genasun Lithium MPPT controllers, all three of them operate exactly the same. The have a set voltage, and only 1 voltage period. You are not understanding what Genasun is telling you. There is nothing to adjust as for Lithium there is no reason to lower the voltage.
Victron is just giving you CYA answer. Can you use 2-stages like Victron suggest? Sure you can, but you are screwing yourself. Both Absorb and FLOAT are the exact same algorithim of CC/CV. In this case Absorb is higher voltage than Float. But what that gets you with Lithium is not desirable. What it does is charges your battery to nearly 100% SOC. Than reduces the voltage to 13.5 volts. So what happens is you end up effectively turning off the solar panels and now go on batteries until they discharge down to 13.5 volts. If there is any sun left at that point, only then will the panels supply any power. That is NOT WHAT YOU ARE ASKING FOR.
Back to Genasun. There are three models for Lithium
GV5 5 amp controller for a 65 watt panel
GV 10 a 10 amp controller for a 140 watt panel
GV Boost Controller which I will not address as it is made for Golf Carts using 36 and 48 volt battery.
Makes no difference which 2 models we talk about, either 5 or 10 amp. Both work exactly the same way. So here is where you get lost. The 2 Genasun MPPT Controllers come in 3 Flavors
12.5 volts for 3S Lithium Polymer (LiPo) cells
14.2 volts for 4S LiFePo4 or LFP
16.7 volts for 4S LiCo or Lithium Cobalt or NCO
You are confusing two flavors of the 3S LiPo and 4S LFP. You are comparing Chocolate to Vanilla. There is also Strawberry flavor for 4S LiCo. You are interested in only 14.2 volts for the LFP Flavor. FWIW 14.4 volts is 100% SOC. 14.2 is something less than 100%. GET IT? The Lithium models only have ONE VOLTAGE and you cannot change it.
Genasun Lithium MPPT is a very simple FLOAT Controller. No voltage changes. It is either 12.5, 14.2, and 16.7. You can also specify any of the two controllers with whatever voltage you want. Genasun PB batteries have 4 stages, but both use the same package as the Lithium. Lithium is just simpler and less complex.
Genasun MPPT Controllers has 3 ports
1. Panels
2. Batteries
3. Load.
The Load Port is an Optional Port as it contains a LVD and Limited to 5 or 10 amps depending on which of the two models you use. LVD disconnects the batteries if the voltage falls to low. DO NOT USE THE LOAD PORT in your application. You already have a LVD
Look at the SPECS
EDIT NOTE TO ALL OTHERS
You can make any good MPPT Charge Controller made for Pb batteries to work on Lithium Batteries. The controller needs to be able to set Bulk = Absorb = Float, in increments of 00.0X volts. Example 14.2 to 14.3 volts. Set the voltage to something less than 100% SOC. For LFP 3.6 vpc is 100% so a 12 volt 4S LFP battery 100% is 14.4 volts. You will have to play around with the voltages to get the SOC where you want. In the range of 13.5 to 14.2 volts. It is not a hard fixed number. Experiment until you get where you want. Start at 14 volts. If that is not enough, try 14.1. If it is to much lower it to 13.9. Repeat until you get where you want.
Simple...
Last edited by Sunking; 07-20-2016, 03:40 PM.MSEE, PEComment
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Do you have proof of this, or is it an assumption?
The LFP model does 12.5v. Check this page: http://genasun.com/all-products/sola...ge-controller/
Specifically, this section:
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OK so what? Who is talking about lead acid? You keep tripping yourself up.
You can FLOAT LFP at 100% if you are willing to sacrifice cycle life. You can Float PB at less than 100% if you are willing to sacrifice cycle life. But for charging them up is no different, they both charge the exact same way with CC/CV. You keep letting Words like Bulk, Absorb, and Float confuse you. They all mean the exact same thing, a voltage set point. Only thing that changes between PB and LFP is the Voltage set points.Last edited by Sunking; 07-20-2016, 04:02 PM.MSEE, PEComment
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Createthis here are some links on Float Charging Lithium cells. It is done everyday.
Electronics Weekly from 2006
Power Stream
Linear TechnologiesI can go on and on with Links. But they all say the same thing. You can extend cycle life of Lithium batteries by Float Charging them. Trick is to Float Less than 100% SOC. Find the voltage is the message I have told you now some 50 times. It is going to be in a Range from 13.5 to 14.2. Find it. at 0.0X increments is 7 optionsAvoid charging to 100% capacity. Selecting a lower float voltage can do this. Reducing the float voltage will increase cycle life and service life at the expense of reduced battery capacity.
13.5
13.6
13.7
13.8
13.9
14.0
14.1
14.2
See which one fits and buy it.
Last edited by Sunking; 07-20-2016, 04:07 PM.MSEE, PEComment
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You charge PB and Lithium the exact same way. Only thing different is VOLTAGE SET POINTS and Termination.
We are talking Float Charging. Makes no diference if we are charging a Lithium or Lead Acid. For lead acid you Float Charge @ 13.2 to 13.8 volts depending on type and temp. For Lithium with respect to only LFP is 13.5 to 14.2 depending on type and temp. Only thing different is the VOLTAGE SET POINT you have to find.
With PB you use your Hydrometer to tell you what the voltage is. With Lithium you need a coulomb counter which you have.
There are a few different ways to charge both PB and Li, but they are the same. Some just Ffaster, some Kinder and Gentler. The Kindest and Gentlest method for both Pb and Li is FLOAT. Only thing that changges between them is the VOLTAGE SET POINT. The trade off is speed on Pb batteries will be slower if FLOAT charged vs 3 Stages of Bulk, Absorb, and finnally Float when charged up.MSEE, PEComment
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Ok, my 3.4v charge completed. I put in 98.91ah. Currently doing a discharge to see how many ah I get back out at that voltage, but I don't see a high knee on the voltage graph, so I predict I'll get 97% back out ( about 95.94 ah ). The MOST I've ever gotten back out of this cell is 103ah, so let's call that 100% SOC. In that case, using a ratio calculation, 98.91ah is about 96% SOC and 95.94 ah is about 93% SOC, depending on whether you compare discharge ah to charge or discharge ah.
I guess I'm not sure how this information works in practice though. It seems like I should set my midnite classic 150's bulk and absorb to 13.6v, leaving the float at 13.5v, if I want a 93% to 96% SOC charge. It seems like Victron's 14.2v bulk voltage is too high. I guess the only way I could really know for sure would be to use 14.2v bulk/absorb and 13.5v float on the midnite classic 150, let it charge up and float for an hour, then run a discharge test on the same cell using the powerlab 8. I don't think my powerlab 8 has programmable bulk/absorb and float settings. It just uses a single set point. Anyway, I don't really want to do that. I think I'm satisfied with 13.6v bulk/absorb and 13.5v float.
It's still unclear (no data) if a 13.5v float will trash my battery a lot faster than no float at all, but this plan seems to be the best compromise between automation and longevity.Last edited by createthis; 07-20-2016, 05:11 PM.Comment
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OK now you are making progress and zeroing in on your number. Looks like 13.6 to 14.0 is your number
OK this is where you are tripping yourself up and splitting hairs.
First Forget Victron and any specific voltage. You want to find your voltage. Understand this, THERE IS NOT SPECIFIC VOLTAGE. It is a range, not a fixed hard number. Even with Pb there is no specific voltage. Every battery owners manual list the voltage as something like 2.25 to 2.5 vpc. Hells Bells on a 12 volt battery that is a range of 13.5 to 15 volts. What is the right voltage? Th eome where the hydrometer says it is fully charged. Right now you have narrowed it down to 13.6 to 14.0 volts. You will find it.
I would not do that, just one voltage, the right one you find.
Then lets clear that up. What stresses a lithium battery is being taken to 100% and/or storing them at 100% which is a big No-No. Your Takeaway is do not go to 14.4 volts. Something less than 100% or less than 14.4 volts.. Ever heard that before? Take a hint from Genasun, they use less than 14.4 or 100%. Read the links I gave you. No problem floating Lithium cells less than 100%. It is the same as 2 or more cells in parallel.Last edited by Sunking; 07-20-2016, 06:43 PM.MSEE, PEComment
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I see how this could be true between different product lines or batches. I hadn't considered it before. I'll keep it in mind.
Hmm. I'm not sure I believe you because I read so much on the internet that says "thou shalt not float lithium", but I'll keep it in mind.
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Hogwash. You have NOT read any such thing from any reputable authority or source on the subject. Not even A123 Battery manufacture would say that. In fact it is just okie dokie to float Lithium.Read the SPECS.
RECOMMEND FLOAT VOLTAGE = 3.45 volts. Exactly what I have been trying to tell you over 100 times. The qualifier is not to float at 100%, something LESS THAN 100%. How many times do I have to tell you that? I have also provided as of now 6 links to manufactures and Authorities on the subject that confirm what I am telling you. What more does it take?
Lastly Genasun does exactly what I am saying Float at less than 100%.Last edited by Sunking; 07-20-2016, 09:08 PM.MSEE, PEComment
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I wouldn't if I was you, he claims many things which are wrong and shows has no experience or knowledge of large capacity lifepo4 packs, listen to those who actually use and have installed them over many years. Never float lifepo4, retailers claim you can so they reduce the life span of the cells and ensure return sales after a few short years. They did the same with lead acid, in the early part of the last century, you could get lead acid batteries to last decades becuas they were desinged and built to do that. After WW2, they changed the configuration of the batteries so they would fail after a dshort time.
Another claim of his is there are no dedicated lifeppo4 chargers available, when we produce them and know of 3 others here on Australia that produce and sell dedicated lifepo4 charge controllers. Everyone with real knowledge and many years of experience with this storage chemistry will tell you, charge your pack to 14, then switch off charge. the pack will settle at 13.8v which is where it should be for long life. It's the same with DOD, never go below 12v in your pack, and you will get a very long life out of them. It's not rocket science using lifepo4, just common senseComment
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