hello From Zimbabwe

[Bud40]

hello Bud from Harare. Been an airline pilot for many years but interested in renewable energy and eager to learn. Im looking at build a 3 k or 5 k system, and id like to use LiFePO4 as the battery system. been watching a few videos on youtube to learn a bit more.. i have a question or two

i note the LiFePo4 batteries are made up in many of the videos. people add a BMS and some have cell balancing that is added to the battery with an lcd screen to show individual cells performance - very cool.

first question- what is the charging pattern of LiFePO4. is it constant voltage?
what should i look for in pairing up this kind of battery with an inverter. ? i want to make a 24 v battery.

ive seen Will P on youtube using an LV2424 from MPP. I contacted MPP to ask them what kind of inverter would be suitable , as we use 220/230 v ac in Harare, and they refered me to an inverter that was compatible to a certain bms only. So im confused. Is the important aspect that the charging ststem must be programmable to suit the battery in question or do i need an inverter that only takes a certain battery and BMS?

any help in my understanding would be great

Regards
Bud

 

[snoobler]

Welcome to the forum.

LFP is highly similar to lead-acid, CC/CV, but it doesn't really need an absorption phase. Charge it up to 14.4-14.6V and then let it float at 13.6V.

For a 24V battery, you need 8 LFP cells in series.

Pretty much no inverters are "compatible" with any kind of BMS. It's up to you to integrate the battery system with the inverter, charge controller, etc.

 

[solarsimon]

An inverter needs volts & amps. It doesn't care what they come from. Lead/Lithium/alternator/whatever
Suggest you look at Victron documentation - it will help you understand the technologies better.
But before deigning a system, ascertain what your typical & maximum load is. in kW.
Then work out how much storage capacity you need to get you through the shortest June days. Or the cloudiest days maybe.
That's your starting point.
I think running your cells from 20% to 80% capacity is a good starting point, to get max life from them

 

[Bud40]

Thank you to Snoobler and solarsimon

this helps a lot .

 

[Steve_S]

Many of your questions are addressed in this: Luyuan Tech Basic Lifepo4 Guide | DIY Solar Power Forum (diysolarforum.com)

Some Inverters are capable of interconnecting with a BMS system. This is usually done using the CANBUS protocol. Compatibility between BMS & Inverters is tricky. For example REC & Orion BMS can interact with Victron Hardware and a few others and have direct ports to do so. Just because a BMS has the protocol does not mean it is compatible.

The ability for an inverter system interacting with a BMS, is that it can better control situations such as Lo/Hi Volt disconnects and even charge throttling or boosting. Again this depends a LOT on the Inverter System and the BMS used, it varies a LOT, as there is no default "standard & protocol". For Example, Victron makes systems that can be fully integrated, right down to BMS Interaction & control. In more advanced (read as much more $$$) systems, some BMS' can even be controlling charge level to cell and throttle / control individual cells within a complete battery pack (did I mention more $$$) ie $200 BMS versus $1500 BMS.

If you want multiple assembled batteries in a complete bank for fault tolerance, load & charge sharing & increased capacity (Amp Hours) there are differing methods of deploying BMS systems. Generally, once we pass 4 battery packs within a bank, a decentralized BMS system is more practical because things get complicated managing each battery bank and ensuring uniform & consistent operations. This is an Extended Topic in itself.

The KISS rules applied is always best to be honest. Keeping it Simple causes much less hassle, especially if something goes awry.
12V battery systems can support 2000W comfortably but not more + Surge capability.

You will need to know how much electricity you will be drawing as a constant and what you surge / spike / high usage. Total Watts/Amps.
Then you will have to figure out which Inverter System can deliver the minimum, the constant & the max potential (In Watts / Amps) you can expect to use.
Then you need to figure out the Battery Sizing in Voltage (related to watts being drawn) and how many Amp Hours is required for a 24 hour period.
Then you need to decide how much reserve power you want on hand (meaning no charging from any source). Many people choose 3 days reserve.
Once you know how much battery you will want as in voltage & amp hours of reserve, you will know the Volts & AH you need. Then you can figure out how much solar is required to support charging the batteries. Also the Solar Controller(s) will have to output enough Amperage to charge the batteries up properly in a timely fashion. THE FACTOR TO CONSIDER Regardless of where you live, is to calculate for the Lowest Sun Hour Days of your year. IF you get 10 hours of sun everyday, 365 days a year GREAT but if you get 10 hrs in summer & 6 hrs in winter, then calculate for 6 hours, which means you'll just be charged faster in summer with 10 hrs a day sun.

24V battery system can support 4000W - 5000W + Surge Capability.
48V battery system can support up to 10,000W + Surge
Stacking Inverters can pick up the slack to keep things in safe voltage zones while providing more amperage out.
72V and Above systems can be deployed but these cross the line to High Voltage DC and so have different requirements & considerations.





SOURCE FOR THE ABOVE:
Solar Angle Calculator | Solar Panel Angle Calculator (solarelectricityhandbook.com)
Solar Irradiance - calculate the solar energy available on your site (solarelectricityhandbook.com)

Hope this helps you out, Good Luck
and WELCOME to teh Forum !

 

[Bud40]

Many of your questions are addressed in this: Luyuan Tech Basic Lifepo4 Guide | DIY Solar Power Forum (diysolarforum.com)

Some Inverters are capable of interconnecting with a BMS system. This is usually done using the CANBUS protocol. Compatibility between BMS & Inverters is tricky. For example REC & Orion BMS can interact with Victron Hardware and a few others and have direct ports to do so. Just because a BMS has the protocol does not mean it is compatible.

The ability for an inverter system interacting with a BMS, is that it can better control situations such as Lo/Hi Volt disconnects and even charge throttling or boosting. Again this depends a LOT on the Inverter System and the BMS used, it varies a LOT, as there is no default "standard & protocol". For Example, Victron makes systems that can be fully integrated, right down to BMS Interaction & control. In more advanced (read as much more $$$) systems, some BMS' can even be controlling charge level to cell and throttle / control individual cells within a complete battery pack (did I mention more $$$) ie $200 BMS versus $1500 BMS.

If you want multiple assembled batteries in a complete bank for fault tolerance, load & charge sharing & increased capacity (Amp Hours) there are differing methods of deploying BMS systems. Generally, once we pass 4 battery packs within a bank, a decentralized BMS system is more practical because things get complicated managing each battery bank and ensuring uniform & consistent operations. This is an Extended Topic in itself.

The KISS rules applied is always best to be honest. Keeping it Simple causes much less hassle, especially if something goes awry.
12V battery systems can support 2000W comfortably but not more + Surge capability.

You will need to know how much electricity you will be drawing as a constant and what you surge / spike / high usage. Total Watts/Amps.
Then you will have to figure out which Inverter System can deliver the minimum, the constant & the max potential (In Watts / Amps) you can expect to use.
Then you need to figure out the Battery Sizing in Voltage (related to watts being drawn) and how many Amp Hours is required for a 24 hour period.
Then you need to decide how much reserve power you want on hand (meaning no charging from any source). Many people choose 3 days reserve.
Once you know how much battery you will want as in voltage & amp hours of reserve, you will know the Volts & AH you need. Then you can figure out how much solar is required to support charging the batteries. Also the Solar Controller(s) will have to output enough Amperage to charge the batteries up properly in a timely fashion. THE FACTOR TO CONSIDER Regardless of where you live, is to calculate for the Lowest Sun Hour Days of your year. IF you get 10 hours of sun everyday, 365 days a year GREAT but if you get 10 hrs in summer & 6 hrs in winter, then calculate for 6 hours, which means you'll just be charged faster in summer with 10 hrs a day sun.

24V battery system can support 4000W - 5000W + Surge Capability.
48V battery system can support up to 10,000W + Surge
Stacking Inverters can pick up the slack to keep things in safe voltage zones while providing more amperage out.
72V and Above systems can be deployed but these cross the line to High Voltage DC and so have different requirements & considerations.


View attachment 33207
View attachment 33208

SOURCE FOR THE ABOVE:
Solar Angle Calculator | Solar Panel Angle Calculator (solarelectricityhandbook.com)
Solar Irradiance - calculate the solar energy available on your site (solarelectricityhandbook.com)

Hope this helps you out, Good Luck
and WELCOME to teh Forum !

thank You Steve . very sorry for the late reply but thank you none the less