Hi,
I recently posted asking for advice about a battery I bought from Battery Hookup. It is a A123 Prismatic Module that is 26s6p made up of 78 A123 3.2 volt 20ah pouch cells. My original plan was to cut the bus bars to make it into 3, 8s 24 volt batteries but my issue is there does not seem to be a good way to attach leads to the existing bus bars. Now I am thinking about making a 72 volt system using the 26s6p battery (83.2 v). I never built a system so I wanted to ask for some advice on this. I see on aliexpress I can buy a 26s lifepo4 bms.
www.aliexpress.com
I also see that I can get a 72 volt inverter with a voltage range of 60-90volts
www.aliexpress.com
The purpose of this system is as a back up to keep the refrigerator, oil burner and some lights running in case of a long term black out.
The questions I have is:
1) I never programmed an MPPT solar charger. Is there a way I can program it for this battery voltage. I would actually like to limit the charge to 90 volts to stay in range of the inverter as 3.7 volts per cell would be 96.2 volts, so I was wondering if I can limit to 88 volt charge (3.4 volts per cell), knowing I will not have full capacity available? I think this should give me 90% capacity and this battery is almost 5kw so it should be a good trade off. Is this the case and is there a way to do this?
2) When it comes to solar panels, I bought 4, Q-cell 290 watt panels. Each is 39.19 open circuit voltage, and 31.96 voltage at maximum power. If I was originally going to parallel connect these for a 24 volt system, however for a 72 volt system I am thinking I can series connect the 4 of them and get an mppt that can handle the voltage. Is this ok?
3) I want to be able to charge the battery off grid. I saw on Will's videos how he used a variable voltage power supply and want to do something similar. Do you know the voltage I would need to charge this connecting the power supply directly to the battery or should it be connected to the MPPT. I like the idea of being able to do solar and grid charge at the same time.
I am sorry to ask all of these questions. I originally thought I would build a simple 24 volt system using Will's blueprints so all the thinking would already be done for me. In this case I cannot even find any examples of people using a 72 volt inverter but it stands to reason to me that it should work. I am used to working with AC wiring so the voltage does not bother me from a safety perspective. What I am most concerned about is that I can do this with a 26S battery.
I really appreciate any insight or guidance you can provide. I have been watching Will's videos for years, I finally decided to pull the trigger and bought this battery because it was a great price for a big capacity and now I am trying to figure out how to manage it since cutting it up may not pan out. I was also thinking about maybe using a step down transformer to 48 volts for a 48 volt inverter but I would still have to deal with the charging aspects.
I recently posted asking for advice about a battery I bought from Battery Hookup. It is a A123 Prismatic Module that is 26s6p made up of 78 A123 3.2 volt 20ah pouch cells. My original plan was to cut the bus bars to make it into 3, 8s 24 volt batteries but my issue is there does not seem to be a good way to attach leads to the existing bus bars. Now I am thinking about making a 72 volt system using the 26s6p battery (83.2 v). I never built a system so I wanted to ask for some advice on this. I see on aliexpress I can buy a 26s lifepo4 bms.
123.25US $ 15% OFF|LiFePo4 BMS 26S 84V 100A120A150A200A with balance for 3.2V LiFePO4 batteries connected in 26 series solar power inverter ebike|Battery Accessories| - AliExpress
Smarter Shopping, Better Living! Aliexpress.comwww.aliexpress.com
I also see that I can get a 72 volt inverter with a voltage range of 60-90volts
412.0US $ 20% OFF|Hot Sale 5000W Solar Power Inverter 24V to 220V Pure Sine Wave Inverter 12V/24V/48V/72V DC to 120V/230V/240V AC Remote Control|Inverters & Converters| - AliExpress
Smarter Shopping, Better Living! Aliexpress.comwww.aliexpress.com
The purpose of this system is as a back up to keep the refrigerator, oil burner and some lights running in case of a long term black out.
The questions I have is:
1) I never programmed an MPPT solar charger. Is there a way I can program it for this battery voltage. I would actually like to limit the charge to 90 volts to stay in range of the inverter as 3.7 volts per cell would be 96.2 volts, so I was wondering if I can limit to 88 volt charge (3.4 volts per cell), knowing I will not have full capacity available? I think this should give me 90% capacity and this battery is almost 5kw so it should be a good trade off. Is this the case and is there a way to do this?
2) When it comes to solar panels, I bought 4, Q-cell 290 watt panels. Each is 39.19 open circuit voltage, and 31.96 voltage at maximum power. If I was originally going to parallel connect these for a 24 volt system, however for a 72 volt system I am thinking I can series connect the 4 of them and get an mppt that can handle the voltage. Is this ok?
3) I want to be able to charge the battery off grid. I saw on Will's videos how he used a variable voltage power supply and want to do something similar. Do you know the voltage I would need to charge this connecting the power supply directly to the battery or should it be connected to the MPPT. I like the idea of being able to do solar and grid charge at the same time.
I am sorry to ask all of these questions. I originally thought I would build a simple 24 volt system using Will's blueprints so all the thinking would already be done for me. In this case I cannot even find any examples of people using a 72 volt inverter but it stands to reason to me that it should work. I am used to working with AC wiring so the voltage does not bother me from a safety perspective. What I am most concerned about is that I can do this with a 26S battery.
I really appreciate any insight or guidance you can provide. I have been watching Will's videos for years, I finally decided to pull the trigger and bought this battery because it was a great price for a big capacity and now I am trying to figure out how to manage it since cutting it up may not pan out. I was also thinking about maybe using a step down transformer to 48 volts for a 48 volt inverter but I would still have to deal with the charging aspects.
