Man Portable, RF Quiet, LiFePO4 Solar Charge Controllers for /P

Absolutely, it's in the video. I'm just wondering why your cells are out of balance like that!?
The low voltage disconnect on the BMS has triggered. In this mode, the BMS has disconnected the battery from the load because the voltage was too low in 1 or more of the cells in the pack. That's why you get a red light on the charge controller.
Remove the charge controller, and use an external cc/cv voltage source, (14.4/0.5A) connected to the BMS power plus and minus, to bring up the voltage in the pack. The application of voltage to the BMS will release the protection state, once the cells have reached a safe operating voltage.

If the BMS from my video was used, the cells wouldn't be out of balance like that. Please ensure you have used a balancing BMS in your build.

73
Julian oh8stn

 

Thanks Julian! In fact I used the exact BMS you listed. I don't know why this happened. It's been working fine, and has had about 6 use/charge cycles since I built it. I'm going to check all the connections, perhaps one has loosened.

Also, the two OUTER cells are the higher voltage ones for some reason.

 

Quite the opposite is true. Where Bottom Balancing became popular is the DIY EV Conversion groups. At first being as an engineer with extensive battery background, I was skeptical up until about 6 years ago with my first racing golf cart. What I discovered like a hundred before me the BMS is what killed a cell. The Balance Boards aka Vampire Boards fail shorted and will destroy a cell.

The second issue we discovered is people are stuck inside a Full Charge Box. That is a lead acid battery leftover and stuck thinking batteries shall be fully charged. However fully charging (Top Balance) any Lithium Ion battery significantly lowers cycle life. Reducing charge to 90% SOC doubles to triple cycle life. If you do not fully charge the batteries BMS does nothing becuase it never goes into Balance mode. All it does is cause a parasitic drain which makes cells unbalanced. So the over charge and full charge is not possible in a Bottom Balanced system. You only charge to 13.6 volts or 3.4 vpc. Most EV Conversion and Off-Grid Solar folks charge to 90%SOC (13.6 or 3.4 vpc) ), and never go below 10 to 20% SOC (12 volts or 3 vpc). EV Conversion and Off-Grid Solar folks have way too much money invested in their batteries to take a chance of from a Vampire Board bleeding a cell to death, and/or shortening cycle life going to 100% SOC.

As for Over Discharge is impossible on a Bottom Balanced pack. The danger of over-discharge is when one cell reaches 0% SOC with the adjacent cells stil having energy in them and will drive the discharged cell into reverse polarity thus destroying it. That is the problem with Top Balance. No two cells have the same capacity or high tolerances. Example if you order CALB 100 AH cells and do capacity test you will find a range of 85 to 105 AH. In a Top Balanced system the voltages are only equal at the Top. However their capacity is NOT EQUAL. So in a deep discharge the lower capacity cell will bottom out before any of the other cells do in a Top Balanced system. slowing the stronger cells to destroy the weaker cell. This is where Bottom Balance shines.

In a Bottom Balanced system all cell voltages and capacities are known at 2.5 volts and 0% capacity. When you charge, every battery has the same AH capacity. So if an accident happens and the batteries go to 0% SOC, there are no cells charge to destroy weaker adjacent cells. Additionally I know of no 12 volt battery equipment that will work down to 8 volts. Some will argue that fully discharge is 2.5 vpc for LiFeP04 however that is mistaken because the 2.0 volts is dead bottom. Again EV Conversion and Off-Grid solar never go below 3.0 vpc or 12 volts 910% SOC) on a 12 volt system. Now if you want to debate the 2.5 or 2.0 vpc is a moot point with Bottom Balance because even if you think 2.5 vpc is bottom is 10 volts on a 12 volt system. bet no ones radio will be happy at 10 volts. For EV Conversion and Off-Grid LVD is of no concern because Inverter trip off-line at 10.5 volts, and EV Motor Controllers will shut down. There is so much cushion at the bottom of a Bottom Balanced system makes over discharge a thing of the past.

For a little background the EV Conversion guys came up with Bottom Balance for reasoned already explained. Where the idea came from is EV Manufactures like Nisan, Chevy, and Tesla. Commercial EV manufactures do not use Top Balance. They use Mid Balance and would never allow a customer to charge to 100%. Otherwise EV batteries would not last more than a year or two. They use Active Balancing where if a cell voltage should become low, take power from higher SCO cells and give it to lower voltage cells. The DIY EV Conversion crowd cannot do what commercial manufactures do because they do not have 10's of thousand of cells to match up in AH capacity. There is a very popular DIY EV forum and many of the members are engineers from commercial EV manufactures, and came up with a way to mimic what commercial EV manufactures do. Bottom Balance was born. Really simple to do. When you get your cells, connect them all in parallel like any Lithium battery. Rather than charge them all to 3.6 volts until current stops. Discharge them 2.5 vpc and you are ready to go. No need for the extra expense for a BMS, or take the risk. A 4S system (12 volt) is extremely easy to monitor with a periodic voltage check. All you have to do is charge to 13.6 volts, and turn the radio off when voltage drops to 12 volts. If you forget to turn the radio off when the voltage dips below 12 volts, your radio will do it for you when voltage drops to 10 volts or less, and no problem for the batteries. .

 

Did you balance the cells before you assembled them? A BMS cannot do the initial/bulk balance because it has high risk of destroying the weaker cells. To do the initial balance requires all the cells to be placed in parallel, and then charged to 3.6 volts before you make and assemble a battery pack.

 

You know what? No one's ever taken the time to explain bottom balancing like this. Usually the arguments are like "because it's better" without explaining why it's better, or the risks of other methods of balancing.
When you integrate solar charge controller into this bottom balancing equation, wouldn't it require a custom voltage on the conttoller!? In the perfect world, the charge controller for lithium iron phosphate batteries should only charge up to 90% capacity, to maximize the lifespan of the batteries.
It seems a bottom balanced pack with a charge controller having a custom voltage, which only charges the path to 90% of its capacity, would alleviate the need for BMS balancing. Perhaps now I understand why Genasun offers custom voltages. It still doesn't provide the short circuit protection equality BMS offers, but I agree on the over and under voltage protection. Besides the over and under voltage protection would be managed by the charge controller. Even I admit the BMS in this regard, is redundant.
I think I'm going to turn this discussion into a video.
I'm grateful for the lesson.
73
Julian oh8stn

 

Good question and glad you asked. Most charge controllers made for Pb batteries will work fine for LFP cell (LFP is short for LiFeP04), not all but most. There is a requirement to be met. The Charge Controller must be software programmable for voltages. In other words the controller allows you to set Bulk = Absorb = Float = 13.4 to 13.8 volts. When you do that you essentially turn a 3-Stage Algorythim into a simple Constant Current / Constant Voltage charger.

But here are some huge mistake charge controllers made for lithium batteries in a solar application.

a. They are stuck in a Pb battery mentality of Thou Shall Fully Charge Thy Battery. So for example Genasun controllers are fixed at 14.2 volts for 100% SOC. Well that just cuts cycle life in half of 500 to 1000 cycles.

b. If you use an integrated BMS that provides LVD and HVD will disconnect the batteries from the charger when the batteries are fully charged. You do not want that in a solar system. If your batteries are charged up by say noon means you are on battery power until the next day. That is foolish because you want to utilize solar power as much as you can and save the batteries until the sunset. Leave out the BMS and lower the voltage to 13.6 volts, the batteries charge to 90% SOC and the batteries FLOAT, while the panels are still on line until sunset providing power to the loads rather than battery.

In short all you are doing is Float Charging the LFP battery and only charging to 90% SOC. Bottom line is this. Pb batteries maximum life is fully charged. Li batteries maximum life is Partial State of Charge (PSOC). EV manufactures run EV batteries at 10/90 and 20/80 depending on manufacture. Use a BMS in the fashion you are accustomed too is charge to 100% every time which is killing your battery life.

Now having said all that for consumer products is the only workable option to use a BMS. Consumers are not knowledge enough to manage batteries. For a manufacture it is a LIABILITY ISSUE and SALES. If you fully charge, you shorten battery life and generate more $ALE$.

 

Thanks for the excellent information and again for the lesson. There are a few generalizations which are not always true in your comments. For example, using the Genasun for abut a year with my diy lithium iron phosphate packs, and my hand picked BMS boards. I have never seen a pack disconnected from the charge controller by the BMS once full. I have seen that happen with "import" charge controllers, and BMS boards with the wrong upper and lower limits. In fact one of the most common questions I get is from people who built one of my packs, but used a popular charge controller often mentioned in this forum, is the BMS disconnecting itself from the charge controller. That's companies advice was to use their charge controller because it was compatible with their BMS. Anyway, that's the whole point of making these DIY projects for people to follow exactly step-by-step knowing that it's going to work if they've wired correctly once done. Projects like this didn't exist, or if someone didn't do the testing over time to prove these things are working the way it said they do, we would all be neanderthals carrying lead acid batteries up to summits.

I think what I'm going to do is take the most useful bits of the information you provided, and come up with an advanced battery build using bottom balancing and a customizable charge controller.

The problem with these kinds oc discussions for the average Builder, is they confuse the heck out of most people. There are far too many conflicting arguments, for the newcomer to get their head around. In any event, I love this discussion and I've learned a lot from you.
I'll put something together.
73
Julian oh8stn

 

Thank you Julian, you always get into the good discussions!
Just about to purchase a controller that will be used with my Ft-891 go box ( 9ah lifepo )
Good stuff!
73, de KN2X

 

Perhaps "not entirely accurate" would be better than "not always true" which could be taken as a lie or misinformation. To your point I should have conditioned the statement and added more content.You just did not build your BMS to disconnect when the batteries were charged. That can come with consequences.

To start most Charge Controllers are fairly dumb devices and know nothing of the outside world. You set the voltages and it goes about its biz as a battery charger. On some of the higher end units like Morningstar and Midnite Solar are fully programmable and can communicate with the outside world via input/output ports and can be programmed because they have some PLC capabilities.

Genasun controllers are completely death and dumb. That is not saying they bad or poor quality CC's because they are not. They are tough as nails, but dumb and death they are. Only model I am aware of that has any outside function is the GV-5 as it has a LOAD TERMINAL which is a LVD none of the other Genasun Controller models have. They can be either Pb or Li. I would never use any Controllers LOAD TERMINAL because they are very low power and in the case of the GV-5 is well 5 amps. Go above that and you damage the controller. I always power loads form the battery. However it can be used to drive an External LVD relay if you want LVD functionality.However that is at pack voltage, not a cell voltage. Example 10.5 volts for Pb or 10 volts for Li.Genasun controllers do not see cell voltages.

Now more to your point. Define a BMS. Go ahead and try, but you cannot define a BMS or what it does. They can be as simple as Passive Balance Boards (aka Vampire Boards) you attach to each cell. They turn on when the cell voltage reaches 3.65 volts and bypass 150 ma of current until voltage is bled down to 3.5 volts and they turn off. That type has no clue or communication with other Vampires or anything else.

One Step further is a Vampire Board with a single wire and a relay contact that closes when it turns on to send a on/off signal. Wire all the Vampires in series, daisy chain, so when all contacts close sends the signal to the charger to do something like Turn OFF and Terminate Charge or reduce voltage. Then there are Active BMS systems that have LVD, HVS, Cell Voltage Monitors, Temperature Sensors for each cell, PLC logic and CAN BUS to communicate with a Charger or a Processor. Again what is a BMS? In simple terms it is a Marketing Term and has no definition.

Back to Genasun again for a moment, or it could be any charge controller for that matter, but with a Genasun Controller output voltage is fixed at some voltage. The models made for Pb batteries have more smarts because they use a 3-Stage algorithm plus Equalize function for FLA batteries. For Li batteries it is a Plain Jane CC/CV power supply with a fixed voltage. For LiFeP04 is 14.4 volts, or you can get whatever you want and just have to custom order, but you are stuck with it once received. Myself I have a problem with that. I do not want to charge my Li batteries to 100% and last thing I want is to Float the batteries 14.4 volts as that can cause serious damage including fire on LFP cells floating at full charge voltage. However I can float all day long at 90% SOC (13.6 volts) and significantly increase battery cycle life and not run the risk of a fire. When you go to 100% SOC on a lithium battery, you need to disconnect the charge source, or reduce the voltage.

Did you catch that sentence? Go back and read it again. This comment is not directed at anyone, but informational. If you are stuck in the Pb world and believe Thou Shall Charge to 100%, you can do that with almost any solar charge controller made for Pb batteries and simple Vampire Boards. It is real simple, you use the 3-Stage algorithm already built into all charge controllers made for Pb. You set Bulk/Absorb to 14.4 volts just like you would any Pb battery, and Set Float to 13.6 volts like any AGM Pb battery. Best way to do that is use Vampire Boards that have a 1-wire Signal Link (contact closure) and a charge controller with a Logic Input you program to drop voltage to FLOAT when all cells are fully charged. I would not do it that way, but hey if you insist on short battery life at 100% SOC, go for it. If you fail to reduce voltage on Li and FLOAT at 14.4, keep a fire extinguisher handy, Li is not Pb.

Hope that helps Julian, and explains why EV's and Off-Grid solar users are not crazy about a BMS. It one thing to loose a $10 cell and only have 4-cells to manage. Its another thing to loose a $300 cell and compounded when you use 16 to 35 cells. EV users are the trend setters in Li technology and most of the DIY EV Conversions use Bottom or Mid Balance like commercial EV manufactures use. Commercial consumer electronics use Top Balance as that is really the only option there is and good for $ale$.

 

For comparison, I purchased this but it is still un-used and un-tested. Note it is PWM, but 20A

Anself 20A 12.6V LCD Solar Charge Controller PWM for Lithium Battery Lamp K2K5
( 192129643909 )

Add note
ITEM PRICE:
US $14.89

73,
Howie, K2EIR

 

A few observations...

A manufactured battery labelled as a "3.6 volt cell" actually has a maximum rated voltage capacity of 4.2 vpc.

The manufacturer typically recommends charging the battery cell to 3.65 volts. This is what the manufacturers definition of a "100% charge" means even though we know the battery cell is actually designed and capable of accepting voltage up to 4.2 volts. (safely)

It is for this reason 4.2 volts and above is the danger zone where damage "may" occur to the cell resulting in shorter cell life which explains why the manufacturer recommends charging up to 3.65 volts instead. But there's more than just extending battery life to consider in the overall equation.

For example, there's not much difference in battery capacity and cycle life regardless if you charge the battery anywhere between 3.4 and 3.6 vpc. But look what happens when you only charge each cell to 3.3 vpc?

In this case your battery may or may not last longer than charging it at 3.6 volts, but we do know it will definitely be at the expense of a significant reduction in usable battery capacity.

 

LCO > LiCoO2, Lithium Cobalt Oxide are the bad boys of the Lithium Ion battery world that give lithium batteries all the negative press from fires. They are the cells used in Tesla EV's in 18650 form factor. They have a nominal cell voltage of 3.6 volts, and charged at 4.2 volts. LCO cells have the highest Specific Energy Density of 150 to 240 wh/Kg, the highest energy density of al the lithium chemistry types and thus the most unstable and dangerous cells made. Tesla has to use very strict thermal management of both heating and cooling

NMC, LiNiMnCoO2, Lithium Nickel Manganese Oxide are what the Nissan Leaf uses. They have a nominal cell voltage of 3.7 and charge at 4.2 to 4.3 volts. They are more stable than NCO, but have a lower Specific Energy Density of 120 to 150 wh/Kg and thus why the Nissan Leaf mileage is lower than Tesla.

LFP, LiFeP04, Lithium Iron Phosphate are what the OP is using. They are the second safest chemistry available. However they have the second lowest energy density of the Li family of 80 to 100 wh/Kg and why no commercial EV manufacture uses them Mileage range would be unacceptable. They have a nominal voltage of 3.2 volts and can be charged at 3.6 volts. There nominal cell voltage is why the specific energy density is low. If purchased in 18650 form factor 1500 mah is about as good as it gets (4.8 watt hours). Where as a 18650 cell in NCO run as high as 3500 mah or 12.6 watt hours in the same package and weight. FWIW LFP are the only Li cells that are compatible with Pb batteries.

LTO, Li4Ti5O12, Lithium Titanate are the safest, longest lasting, and most expensive of the Li family. Only military applications use them. Being the safest means the lowest Specific Energy Density of 40 to 80 wh/Kg and lowest nominal cell voltage of 2.4 volts and charge at 2.85 volts. They are every bit as heavy and big as Pb batteries. however they have the absolute highest cycle life and Specific Power. They can be charged and discharge extremely fast in minutes. One application for them is Rocket and Missile liquid propellant pump power where you only need just a few minutes to power the pumps.

As for your graph I am familiar with it, and you would never charge a LFP to 4.2 volts. They can withstand it, but not without stress and damage. Same for charging to 3.6 volts. What they are showing you and trying to get across is there is no useful capacity above 3.4 or below 3 volts per cell and in a 4S configuration is 13.6 volts and 12 volts. Now you know where 13.6 and 12 volts come from in my previous statements. You just confirmed what I have been saying. But if you need further proof there is a lot to be found like from Battery University White Paper called How To Prolong Lithium Ion Batteries and is backed up by manufacture spec sheets. Note Table 2 Notes

Further down you will read:

Thi sis why commercial EV manufactures do not allow customers to charge the battery to 100% capacity. Its the only way they can give 5 and 10 year warranties. If they allowed you to charge to 100%, they would go bankrupt with warranty claims because the batteries would only last 300 to 500 cycles. .

If you read data sheets on any lithium battery they all say batteries should be discharged to 50 to 70% SOC is stored or not being used because charging them to 100% stresses the cells and raises the risk of Thermal Runaway. There is no reason to charge to 100% as you are just asking for trouble.

Take what you like, discard the rest.

 

I really don't think any of this has added any value to the discussion.
There is fact and there are opinions regarding what something is, or how something works. That is why we need to do the component research. What someone calls a Vampire BMS, I call "The cheap Chinese trap". Most operators get stuck on that trap, when price is their main requirement, ahead of functionality. Still, just because one has a bad experience with a crap board or stupid charge controller, doesn't mean we should blanket label all components in the discussion.

This is why these discussions are often unhelpful. One has an opinion, but it is based upon an incorrect conclusion about a product or products. This is why I do my testing in the real world, with the gear I am talking about. Reading the specs, won't always give us the answers we want, especially, when the conclusion has already been assumed. So I avoid making blanket comments about a particular product until I have tested it. With that said. I use both the GV-5 and GV-10 for LiFePO4 packs. They are connected to PowerFilm solar panels in the field or the 80 watts mono- on the tower.. When the battery pack reaches 14.2 volts, the Green light comes on on the GV-5/GV-10, telling the end user, the battery is "fully charged". If I have a device connected to the pack from either the GV-5 load port, or the GV-10 battery port will regulate the voltage coming from the panel. It then diverts it to power the connected devices- It never "force feeds" the battery, and the battery will never get over-charged, (unless your BMS has some credulously low, high voltage shut off point)! If there is no device connected, that same green light comes on, but the the energy harvested is simply wasted, because the charge controller won't over-charge the pack. With Genasun controllers, you don't need to sit there ans monitor your system, because it will never over-charge your pack. This is true, regardless of what one believes is true or not.I was with you until the insistence upon "Not entirely accurate" facts to back up agreements. I'll take what was useful and leave it there. I'll also make a follow up video (as soon as it stops raining in KP25), because this discrepancy regarding Genasun controllers is "not entirely accurate". A demonstration is definitely in order.
73
Julian oh8stn

 

Julian the term Vampire Boards is just a term used to describe the function of how Balance Boards work and is the basis of how all Passive BMS work. If you look at the dozens of integrated circuits like from TI and other chip manufactures all use the exact same Balance Circuit concept where the circuit detects a voltage and turns ON (3.6 volts in the case of LFP) and Shunt Bypasses (bleeds) a fixed amount of current. TI chips use 150 ma. When the voltage bleeds down to 3.5 volts the circuit turns OFF. So the term Vampire Boards is just describing the action of how it works. The failure mode is the device fails shorted and never turns off and bleeds the cell to death like a Vampire would do. That is not an opinion, but just how Passive Balance Boards work.

Active Balance circuits work entirely differently by taking power for higher SOC charged cells, and gives that power to lower SOC cells. Only place you see that is on commercial EV's because they are expensive and complex circuits used in BMS that Mid Balance rather than Top Balance.

Julian there is no magic going on inside the GV5 or GV10, Ohms Law regulates what and where power is going. The controller has no clue what is going on outside of it or where power is going. It works like any battery charger and is CC/CV. You are right the green light comes on when the charger voltage reaches 14.2 volts which means the voltage reached 14.2 volts, but that is all it means and is now basically a DC Power Supply. It holds 14.2 volts and power goes where ever Ohm's Law takes it. If there is no load demanding power, no current will flow and is purely regulated by Ohms Law and the controller has nothing to do with that. The issue I take with the controller or any controler is it goes to 14.2 volts and holds (aka FLOATS) at 14.2 volts. That is the constant voltage phase of any charger or DC Power Supply. It is holding 14.2 volts or 100% SOC that I take issue with because I never want to take a lithium battery to full charge and then float it at full charge voltage. That sets the battery up for possible thermal runaway.

That is why I said if you are in the Thy Shall Fully Charge my Lithium Ion Battery camp, you would be better off with a 3-Stage charge controller made for Pb batteries. You get the same CC/CV charge to 14.2 volts, but when that point is reached, the voltage is lowered to 13.6 volts that is referred to as Float. When that happens the voltage on the battery is BLED down to safe voltage, and still allows the panels to supply power to the loads to save the battery for later after sunset.

 

Sure and I completely agree charging a battery to its "100%" maximum rated voltage limit may reduce the life cycle of the cell.

However, what comes into question is what constitutes and defines what "100 %" maximum voltage capacity is exactly?

The battery manufacturer already knows there's no significant benefit charging a battery cell with a maximum rated voltage capacity of 4.2 volts above 3.65 volts.

I don't think a further reduction in charge voltage provides any significant benefit than what the battery manufacturer already recommends.