It is difficult finding a suitable BMS for off grid systems, that is why I designed my own. I have made it an open source project which you can find here github.com/simat/BatteryMonitor. There are some commercial systems out there but they all have their problems, IMO probably the best is called 123smartbms and comes from the Netherlands, battrium which comes from Australia and the Orion Jr BMS from the USA. The venerable Cellog8 is also useful and cheap but will unbalance a battery if it is not modified. Sorry about not posting links, this forum doesn't like links.
When you measure the cell voltages also makes a big difference as to how spread out they are. As you can see at the start of the absorb phase the voltages are close together. They are at the most out of balance when the solar controller goes from the absorb phase to float at around 130 minutes. During the absorb phase some of the cell voltages go down while some go up!
GeoffAbosrbVolts.jpg
Your English is very good, much better than my Romanian!
Simon
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Hi Karrak,
Thanks for answers. I don't have any kind of BMS because I can't find a BMS properly for renewable energy (PV, wind or hydro). All the BMS on market are for EV's. I have a friend in Romania who build a prototipe for our use, but I don't testing yet.
I find a forum in AUS for PIP4048, but they testing some modified software. As inverter is very good, but as charger it's not so good even for Pb. As you see in manual which I posted, you can set only Bulk and Float, but nothing for Absorb (voltage and time). There are many others who buy from Voltronic, like Giant (AUS) or Effekta (Germany).
These days I find something interesting: in a cloudy day my batteries was charged with small current and batts was very eguals in voltage (3.37V/cell x 16 = 53.9V). But if it was a sunny day I find batts from 3.35V, 3.37V, 3.4V and 3.43V (all pack at 53.9V).
P.S. Please excuse and correct me if I made grammar mistake.Leave a comment:
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Your settings for the Midnite look good for an off grid system where there are intermittent loads like fridges etc. turning on and off all the time. These settings will charge your battery up to around 99% full and keep it there until the sun goes down. Dropping the Float voltage to 53.6V will still keep your battery full and may increase its lifespan. The coulomb (current) efficiency of LFP batteries is around 99.5%. I am not sure if the battery voltage has to drop below the Rebulk voltage at night for the Midnite to start charging the battery the next morning. If this is the case I would set the rebulk voltage to 52.8V.
From the Midnite manual
Bulk MPPT
This stage of the Classic means that the Classic will be putting out as much current as it can to raise the
battery voltage to the absorb voltage set point. This is also known as Constant Current Mode.
Absorb
This stage means that the Classic will maintain the Absorb set point voltage until the batteries are charged.
This stage is terminated at the end of the Absorb time or the End Amps set point, whichever is reached
first. At this stage the Classic is not putting out maximum current, as that would increase the battery
voltage over the Absorb set point. This is also referred to as Constant Voltage Mode.
The absorb time is proportional to the bulk time (i.e. the time bulk takes to reach the absorb voltage). The
battery is considered full at the end of the absorb charge cycle.
From this I take it that Midnite's term "Absorb set point voltage" is the same as bulk/absorb voltage.
The PIP inverter-charger should work with your LFP battery. I know of at least one person in Australia who is using one to charge an LFP battrery. There are mixed reviews about this inverter. Do a search for PIP 4048 on the Australian Energy Matters Forum for more information.Till now I used internal solar charger from PIP inverter, but it has few options (manual). For PIP inverter-charger I can setup Bulk and Float, but no option for Absorb.
I am interested to know what other people are doing to monitor, protect and balance their LFP batteries. Would you mind posting information on what sort of battery management you are using.
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
Last edited by karrak; 05-17-2017, 07:47 AM.Leave a comment:
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Hello to all from Romania!
I came here because I need your help. I buy this month an Midnite Classic 150 and I want to know which are the best setup for parameters in every submenu.
My system is:
- panels: 20 x 185W Sharp mono
- charger: Midnite Classic 150 + Shunt (50mV 500A) + Whizbang jr.
- inverter-charger: PIP 4048MS (made by Voltronic Power and rebranded by MPP Solar)
- battery: 16s 48V 100Ah Sinopoly
Till now I used internal solar charger from PIP inverter, but it has few options (manual). For PIP inverter-charger I can setup Bulk and Float, but no option for Absorb.
Midnite has a lot of options and I don't know how to setup properly. Now I have this settings on Midnite:
- Absorb = 56V, time = 2Hr
- Float = 54V (I was inspired by Victron settings)
- End Amps = 5A (0.05C)
- Battery efficiency = 94%
- Rebulk = 51.2V
- No EQ
I can't find Bulk in menu.
Thank you in advance for help.Leave a comment:
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No I wont sell the design to you I will give it away, github.com/simat/BatteryMonitor.
Would you buy a car with no warning gauges or lights that tell you when something really bad is going to happen unless you stop and fix the problem, or how about an electric appliance that could burn your house down without extra fault monitoring circuitry built into it?Leave a comment:
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It was sarcasm to make a point that for consumer products with respect to Li batteries will always have some sort of BMS.
Currently in my position I have over 200 Lithium battery's in various forms. 150 or so for RC planes. dozen or so in cell phones and cyber toys. 30 large format cells installed in a racing golf cart Another 8 large format in my ham shack on solar. and a new set for the golf cart waiting to go in.
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> im not familiar with what Pb is?
Pb is the chemical abbreviation for Lead. H2SO4 is Sulfuric acid. So a lead acid battery would be Pb H2SO4 and abbreviated to Pb for simplicity
Simple is key here. You have a lot of energy stored in batteries. Lot's of $$ in a well engineered charge controller. then you take a couple dozen DIY balance boards, string them together and call it a BMS and sell it to neophytes. Problem is, the balance boards and all their wires are just more stuff waiting to go wrong, with uncertain failure modes.
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pb is short for Lead.
As for that lithium ion battery. lets take a look at what it says it can do and how much it will cost to generate power.
So it is a 48v 100 Ah battery. That calculates to a 4.8kWh at 100% SOC. The claim is 3000 to 5000 cycles of 100%. So lets say 4000 cycles which would come to 4000 x 4.8kWh = 19200kWh. The price (excluding installation or any other materials) is $5000. So $5000/ 19200kWh = $0.26/kWh. Not bad for CA or Hawaii but way too much for just about the rest of the US.
And the true cost is more than the advertised $5000 due to needing a charger and installation. Also if you get less than 100% discharge or less than 4000 cycles the cost goes up per kWh.
IMO it is not a financially smart investment.Leave a comment:
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not sure what a pb is...and i do know a bit about electronics ,btw or electric drilll batteries not multi cell? i have tons of them and never have a problem wasnt sure if they were any way my buddy suggested putting together my own cells buying a bms and putting digital monitors on each cell and adding fuses on top of what the bms uses ...but i was considering a prebuilt i wana post the link so i can get some input on it http://www.lithiumion-batteries.com/...on-battery.php any input would be appreciated ...Leave a comment:
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so i found a company i was thinking about using...heres the link to the battery i was looking at... http://www.lithiumion-batteries.com/...on-battery.php ......... any input would be much appreciated some one suggested to me the other day just buying the cells and bms then i could put digital monitors and fuses on each one on top of that ..but i dont see why this pack wouldnt work for me..? also i do know a good bit about electronics but im not a expertLeave a comment:
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