Victron charge controllers for lifepo4

[solaar]

So, I've got a 60Ah battery on the way (with BMS and BCU) and still have to order a controller to charge it from my panel.

The only option I am aware of are the Victron controllers, which are programmable (are there others?). I am going for the 75/15 variant and I will also order the ridiculously overpriced VE to USB cable to connect it to my laptop (I'm not going the bluetooth dongle option).

Is there anything I have missed?

Thanks

[Mike90250]

Most of the morningstar controllers are programmable - but you have to invest in an adapter cable to get to the computer. And the midnight solar controllers (Kid) are programmable, but higher cost for higher outputs

[karrak]

The EPsolar tracer-A MPPT controller (also sold under the name epever and HQST) is also programmable. Needs a cheap RS485-USB converter to connect to a computer.

I would be interested to know the make, model and specs of your battery.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

[solaar]

Hi Karrak, sorry didn't see this post. My battery is an EV Power 60Ah lifepo4 with BMS

[mike3367]

i have the victron 100/30 and you can set the voltages to what you need with the ve direct usb cable and their victron connect app

[Sunking]

Many controllers you can do that. You need 14.2 to 14.4 volts. The real qusetion is how you will turn the controler off or lower the voltage once the battery is fully charged.

[solaar]

Many controllers you can do that. You need 14.2 to 14.4 volts. The real qusetion is how you will turn the controler off or lower the voltage once the battery is fully charged.

I thought that was the point of the float setting in terms of lowering the voltage. My battery specs that it can be floated indefinitely at 13.6V I think. In terms of shutting it off, the BCU is there to prevent overcharge, or is this really only supposed to be there as a backup measure?

[karrak]

You are right that the float setting is there to lower the voltage. Doing this should increase the lifespan of the battery. Lowering the float voltage to 13.4V rather than 13.6V will still keep your battery around 100% full and might increase the lifespan further.

The BCU is there to stop any of the individual cells going outside their safe operating zone, 4.0V to 2.6V or to stop a charger fault causing the battery voltage going above 15.1V and to stop you discharging the battery below about 10% (11.9V). It is there to protect the battery.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

[karrak]

2 wires used for Power that connect directly to the battery term post after the fuse. This makes sure your battery will be completely destroyed if it operates and you do not catch it in time. The BCU keeps taking power from the batteries after the charger and load are disconnected from Low Voltage Disconnect. On the flip side the BCU will disconnect the charger and load if the voltage goes to high so it does not destroy the battery.

In the event that any of the cell voltages gets too low (<2.6V) or the overall battery voltage gets below 11.9V (average 2.975V/cell) the BCU will disconnect the load from the battery. If you had a 60A load on your 60Ah battery when this fault occurred your battery could be damaged within minutes. If the BCU disconnects the battery, the load on your battery will go from 60A to the power drawn by the BCU and BMS modules (<0.020A). At this current it will days or even longer before the battery is damaged by the current draw from the safety circuitry. It would be better to have two separate relays, one to disconnect the solar panels from the charge controller if any cell voltage gets too high and one to disconnect the load if the voltage gets too low. IMO and industry standard practice would say that it is better to have some protection rather than none.

Easy Peazy. Make it even easier. You do not need it if you are using it to power an Inverter. Your Inverter should have a Low Voltage Disconnect that triggers at 11 volts which is 1 volt Higher than your BCU will operate. You can charge it anywhere from 13.6 to 14.2 volts. Keep in mind those Vampire Boards used to protect your cells are the number one cause of failures and fire. They earned their nickname Vampire Boards. The industry calls them various names like Balance Boards or Bleeder Boards, in your case they are called BMS Modules in your drawing. . Simple device, they turn on when cell voltages reach 3.6 volts or so, and apply a Load to the battery to Bleed it or Discharge. The problem is when they fail, they do not disconnect and Bleed your battery to Death like a Vampire. If you are lucky it just destroys the cells and you get to replace them. Otherwise you have to repair the fire damage first before you replace them.

The BCU disconnects the load at 11.9 volts, not 10 volts as Sunking has stated. At 11.9V you will still have >10% of charge left in your battery.

As for failing, there are a number of people using these devices from this manufacturer in Australia. I haven't heard of any failures. I agree with Sunking that if they do fail they could damage your battery if you didn't find the failure in time. The BCU will give you some warning, but not much by disconnecting the battery if one of the cells is discharged by a faulty BMS board.

To charge a lithium on solar, all you need is a very simple charge controller that you can set the voltage to 14.2 volts. That is the Industry Standard voltage for LiFeP04 solar charge controllers. If the panel wattage is 140 watts or less Genasun makes Charge controllers for Lithium Batteries as well as lead acid batteries. The Lithium units are less expensive than Lead Acid as they are much simpler with only one function, 14.2 volts no matter what else you want. Just make sure you order the right part number. Lithium has 3 part codes one each for LTO (12.5 volts), LFP (14.2 volts), and LCO (16.7 volts). Additionally you can use any standard charge controller if you can dumb it down and set it to 14.2 volts For most Programmable models you set Bulk = Absorb = Float = 14.2 volts. That turns it from a Smart 3-Stage Charger for Lead Acid to a Dumb 14.2 volt lithium battery charger.

Charging and floating an 12V LFP battery at 14.2V (3.55V/cell) will reduce its lifespan and could damage it if there is no BMS system installed. A charge voltage of 3.55V/Cell is equivalent to an SOC (State of Charge, how full the battery is) of >99.8% (see my post https://www.solarpaneltalk.com/forum...679#post320679 for more details). With the BMS you have you will need to charge to at least 14.2V to make sure the battery stays in balance. For longer lifespan while still charging to nearly 100% a charge voltage of 13.8V (3.45V/Cell) is preferable. A float voltage of 13.4V (3.35V/cell) will keep your battery close to 100% full while the sun is shining.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

[Sunking]

I thought that was the point of the float setting in terms of lowering the voltage. My battery specs that it can be floated indefinitely at 13.6V I think. In terms of shutting it off, the BCU is there to prevent overcharge, or is this really only supposed to be there as a backup measure?

If you Float Charge at 13.6 volts, there is no reason to terminate the charger as the battery can Float continiously. In fact if you are going to charge with Solar, it would be foolish not to Float Charge at 13.6 volts. Example, very real example let's say by noon your batteries are charged up, and you terminate. You system from the point on is on batteries, despite you still have 6 hours of sunlight. If you were in Float, then the panels would supply all the power until sunset. Then you go on battery after sunset.

Your BCU is just a relay to connect and disconnect the battery. Your BCU does not really do anything. It is just used to provide your BMS (Vampire Boards) with a Means to connect or disconnect the batteries. If I had to guess your Vampire Boards can disconnect either for over charge or over discharge. If you Float at 13.6 volts, your BMS is pretty much rendered useless which is not a bad thing because you do not need it. Your BMS will not turn on until your pack voltage 14.2 volts,

FWIW ignore Karrak.

[karrak]

If you Float Charge at 13.6 volts, there is no reason to terminate the charger as the battery can Float continiously. In fact if you are going to charge with Solar, it would be foolish not to Float Charge at 13.6 volts. Example, very real example let's say by noon your batteries are charged up, and you terminate. You system from the point on is on batteries, despite you still have 6 hours of sunlight. If you were in Float, then the panels would supply all the power until sunset. Then you go on battery after sunset.

Big problem with this is that charging at this low voltage will mean that the battery will start going into the absorb (constant Voltage) phase well before the battery is full which will limit the charge current and increase the time it takes to charge the battery. As you can see from the graph below charging at a rate of C/5 at a charge voltage of 13.6V (3.4V/cell) will slow down the charging when the battery is only just over 70% full! Not very useful when you are charging from solar with a limited amount of sunshine.
ChargeCurves.jpg

Your BCU is just a relay to connect and disconnect the battery. Your BCU does not really do anything. It is just used to provide your BMS (Vampire Boards) with a Means to connect or disconnect the batteries. If I had to guess your Vampire Boards can disconnect either for over charge or over discharge. If you Float at 13.6 volts, your BMS is pretty much rendered useless which is not a bad thing because you do not need it. Your BMS will not turn on until your pack voltage 14.2 volts,

The BCU is there to protect the battery, it will protect it from too high a charge voltage, from over discharging and if the battery goes badly out of balance. The BMS modules installed on your battery will only keep the battery balanced if it is charged at a voltage equal or higher than 14.2V. It is important to keep the battery balanced as not doing so could reduce the storage capacity of the battery and decrease its lifespan.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

[Sunking]

Big problem with this is that charging at this low voltage will mean that the battery will start going into the absorb (constant Voltage) phase well before the battery is full

No chit Sherlock Holmes, you can say that about every battery. All your chart shows if you charge at a lower rate, it takes longer to charge . Duh!!!

The point is you do not want to charge your battery to 100%.Bu tif you want to go as fast as you can is super easy You set the Bulk/Absorb to 14.2 volts and Float at 13.6. No BMS required as it will never be used.

Get lost Karak you do not know what you are talking about. You are a pretender.

[karrak]

No chit Sherlock Holmes, you can say that about every battery. All your chart shows if you charge at a lower rate, it takes longer to charge . Duh!!!

The point is you do not want to charge your battery to 100%.Bu tif you want to go as fast as you can is super easy You set the Bulk/Absorb to 14.2 volts and Float at 13.6. No BMS required as it will never be used.

Get lost Karak you do not know what you are talking about. You are a pretender.

Again reality doesn't match what you keep saying.

from a previous post on this subject

In summary using a charge voltage of 3.60 volts at an end current of 0.45A (C/200) as my 100%SOC reference i found that.
3.70V(14.8V)@C/50 end current = 100.15%SOC
3.60V(14.4V)@C/50 end current = 99.94%SOC
3.55V(14.2V)@C/50 end current = 99.83%SOC
3.50V(14.0V)@C/50 end current = 99.68%SOC
3.45V((13.8V)@C/50 end current = 99.41%SOC
3.40V(13.6V)@C/50 end current = 98.91%SOC

So if you charge at 14.2 volts (3.55V/cell) you can get to higher than ~99.8% full. Even if you charge to just 13.6V (3.40V/cell) you can get to higher than ~98.9% full.

If the battery is balanced when full there will be no problems charging to these levels. If the battery goes only slightly out of balance without a BMS/BCU to detect and correct the problem you could easily damage your battery.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

[Sunking]

Simon you are totally clueless. You do not even know how a lithium battery charges. You think there is only one way to charge a lithium battery, a outdated method you read in a science fiction book. You do not need anything special for 4S and 8S lithium. Your numbers are make believe. You do not even know how to read the graph and what it is telling you. Of course I can understand why, you are a salesman of cheap chi-com junk batteries you peddle to unsuspecting fools.

[PNjunction]

Hi Solaar - have fun with your 60ah bank. It is a great way to learn as long as you are safe.

I hope you have read through some of the GWL-Power blog articles, in addition to what you find here.

The overall mantra of solar with LFP, is to be conservative after you have balanced the cells with the BCU, but don't overdo it, like running a high CV voltage for normal use, as Sunking points out.

Unlike steady-state charging sources, which nearly ALL manufacturers and users alike consult charts with gusto, very little attention is paid to the damaging effects of TIME, when using a high CV voltage, like 14.2v with unstable solar. There's charts, and there is the "real world". You'll find out soon enough.

Huh? We know that LFP does not *have* to be charged to 100% SOC all the time. In fact, it is bad to do so, BUT you may not notice the effect right off the bat. But little by little, 5 mins a day of overcharge while the BCU does it's balancing trick adds up over the years!

Thus, for solar, it is best to purposely "derate" your cells by about 30%, and run with a conservative voltage, like 13.6 maybe 13.8v and never achieve a true full charge for daily operations.

Why? Since solar is unpredictable, there is a good chance of overcharge if you run a high CV even IF all the voltages seem to be within spec. Thing is, that spec assumes a constant steady state of power!

How? Let's say you reach your 14.2v CV point early on in the day. Normally this "absorb" would be pretty fast. BUT WAIT - clouds appear, and now you have nothing but basically a trickle. So let's say from noon onwards, with a high CV, your cells NEVER reach that point, not even enough for the magic balancers to activate, but you have kept the cells artificially high for 5-6 hours *trying* to achieve your high CV setpoint. These hours spent trying to achieve this goal, and failing to do so, adds up.

Maybe this link to GWL Power's blog might help explain the situation:

http://www.auto88.cz/_info/Doc/GWL-P...OverCharge.pdf

So dude, in the end with my 40ah system made of GBS cells, I purposely derated by 30% (20% on the low side to stay out of the discharge knee, and 10% from the top for my relatively low daily cyclic 13.8v CV) to amount to basically a 28ah battery in cyclic conditions for best overall life. With the high up-front price of LFP in the first place, this is a bummer financially.

Too much info, I know. The moral again with solar is that most information out there assumes a steady-state of power (AC, generator or such), and don't know a thing about clouds!