12v and 24v loads on a 24v powerwall

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lifepo4_powerwall

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I need some help confirming the wiring on this project.
To recap from other postsI have 10 packs of LiFePo4 calls, each with 12v in 4s19p arrangement.
I am going topower a 6000w 24v inverter to run loads in the house when I lose power during a storm in Florida. I have an interlock which isolates the line supply when I use this inverter. I connected each pair of packs to get 24v.The nickel strips on the picture below links two packs for 24v. For simplicity I'll ignore the Headway38120 cells under the blue inverter.
During a normaldayI also want to run a 1500w12v inverter so I have wires coming off each pack to powerthis inverter. This inverter will run some loads in my house such as my office equipment in the day while my 4 renogy 100w panels charge the array.
All wire runs are the same length and I up sized the wire AWGa bit to lower losses.

My concern is the wiring the 12v inverter and the 24v inverter. Is this going to work without frying my 12v inverter?The red and black wires are for the 12v inverter. Wiring for the 24v inverter is not shown (they connectat the top of each pack).

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Also how can I attach these voltage meters?I can't figure outa screw small enough.

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Thanks for the guidance.
Andrew
 
This cannot be really done. You won't fry the inverter, you'll fry the batteries.

You can't connect cells in series to get 24V, and at the same time connect 1/2 of the cells in parallel to get 12V. You have common ground and will short things out.

Also, even if you use 3 inverters (1x 24V, 2x 12V) where the 2 12V inverters connect to 1/2 of the string, this is heavily not advised. You will severely unbalance your battery string and make it nigh impossible for the bms to keep things balanced.

If you want to run a 12V inverter AND run 24V inverter, then have two separate battery banks with different chargers. Keep them completely isolated. Otherwise you're asking for troubles.
 
I hadthe same issue. My original system was 12V and then I saw the error of my way.
So I took the dive and went to 48V but what to do with a perfectly good 12V modified sine wave inverter.
At this time I was a newbie and didn't know much about battery balance and such so as my let acid battery bank consisted of 12 12V batteries I figured to just hook up the inverter to 1 of the 12V batteries and the balancers would take care of the rest. Wrong. just about killed one string of my pack.
So the short answer is no it can't be doneunless youfigure out a way to relay switch between each 12 volt cell in a very consistent manner to spread the load across the whole pack. They did that in WW2 on the subs. Quite a wiring nightmare.
My solution was I found some 2V 200AhAGMbatteries got 6 of them cheap ($150.00) including the holder for all of them.(also going to buy another set to have 400Ah available for those cloudy days :D )I amusingone of my arrays to charge it and power my 12V inverter with them. I did notice you have 4 100 watt panels so you may need to get some more.
Good thing is now I have a 200Ah battery that powers all my little projects. Li-Ionchargers, cell testers. anything that requires 12 volts or below and with proper DC buck converters you can get any voltage you want at a reasonable price.
Hot glue for the mini meters. If they are adjustable be sure to set them before you mount them :)

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Wolf
 
wattwenger said:
I hadthe same issue. My original system was 12V and then I saw the error of my way.
So I took the dive and went to 48V but what to do with a perfectly good 12V modified sine wave inverter.
At this time I was a newbie and didn't know much about battery balance and such so as my let acid battery bank consisted of 12 12V batteries I figured to just hook up the inverter to 1 of the 12V batteries and the balancers would take care of the rest. Wrong. just about killed one string of my pack.
So the short answer is no it can't be doneunless youfigure out a way to relay switch between each 12 volt cell in a very consistent manner to spread the load across the whole pack. They did that in WW2 on the subs. Quite a wiring nightmare.
My solution was I found some 2V 200AhAGMbatteries got 6 of them cheap ($150.00) including the holder for all of them.(also going to buy another set to have 400Ah available for those cloudy days :D )I amusingone of my arrays to charge it and power my 12V inverter with them. I did notice you have 4 100 watt panels so you may need to get some more.
Good thing is now I have a 200Ah battery that powers all my little projects. Li-Ionchargers, cell testers. anything that requires 12 volts or below and with proper DC buck converters you can get any voltage you want at a reasonable price.
Hot glue for the mini meters. If they are adjustable be sure to set them before you mount them :)
Wolf
Click to expand...

I appreciatethe responses; glad I reached out before continuing. I'll consider getting a2000W 24vpure sine waveinverter that I can run loads without using my main breaker panel.
At this point I just want to get it working!, spent enough already.
I don't have a BMS, I think the Batrium solution is too expensive, was planning to bottom balance instead and use voltage meters on each battery bank to monitor their state.
Any other BMS suggestions?
Andrew
 
lifepo4_powerwall said:
I appreciatethe responses; glad I reached out before continuing. I'll consider getting a2000W 24vpure sine waveinverter that I can run loads without using my main breaker panel.
At this point I just want to get it working!, spent enough already.
I don't have a BMS, I think the Batrium solution is too expensive, was planning to bottom balance instead and use voltage meters on each battery bank to monitor their state.
Any other BMS suggestions?
Click to expand...

If you haven't bought the inverter, I'd recommend as jdeadman said and go 48V. You'll save money in the end and headaches. Plus, a lot easier to expand.
The inverters don't cost that different, either.

For the bms, there are a few out there. A few here on the forums, too. Stuart Pittaway's (I think Stuart is the designer, could be the revisioner too) bms is one that is in current development. Each pack has it's own module and communicates back to a master hub. Fairly straight forward. But it's not exactly a "solder up 2 wires and your good to go" kind of thing. Requires a little bit of know how.

Btw, Stuarts is free and I think the PCB gerber files are freely available.
 
Deligreen might do balance yes but thats ALL. You dont know what they balance or why. They dont do any protection either. In normal setup the balance is not the biggest issue if you have dont your homework on the batteries. You need the protection when it goes bad becaues it will go bad some day.
 
OK, understand that - I'm a Batrium user too - but can gear be combined to get a reasonable but lower cost option like the OP is looking for?
Eg some of the above 1s balancers & a cheaper BMS doing monitoring & contactor control?
There has to be some reasonable lesser cost 8S BMS out there?
 
The 1s balancers are very expensive for what you get! You can get a cheaper bms from the start yes and several is out there. I would say they start from around 50USD unless you go the Ebike route :)

LifePo4 is a bit more uncommon but they are out there for 8s as well. I have not digged into the 24V range but they should exist and people should be able to shime in on the area and what is out there. As said if its balanced good enough from start the balancing current do not have to be that big. Then its more a matter of what functions is wanted and needed. For instance user-setable voltage levels is nice to have for sure!
 
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