Battery arrangement/wiring question.

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EA6LE-ONE
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54 x PANASONIC VBHN325SA17 325W

System 2:
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21 x PANASONIC VBHN325SA17 325W
Location: Providenciales, Turks & Caicos Isl.

Re: Battery arrangement/wiring question.

Post by EA6LE-ONE » Fri Aug 21, 2020 9:59 am

pss wrote:
Fri Aug 21, 2020 9:43 am
Okay, here goes. An 8048 can output sustained 8000 watts. At input of 50 volts, that's 160 amps. And from my research, 2/0 wire capacity is 190 amps.

I dug this up (https://www.ecmag.com/section/codes-sta ... electrical): "this section permits aluminum, copper-clad aluminum and copper conductors that are at least 1/0 AWG or larger to be connected in parallel if these parallel conductors are electrically joined at both ends to form a single conductor". then the amperage capacity will be doubled.

In my case, I used all 4/0 connectors from my batteries to the inverter and between batteries. You can use a single run of 2/0 to each inverter and be within specs. Or you can run a single 3/0 or 4/0. I think if you plan on expanding battery capacity in the future, the connections to the buss bar are more important than the connection gauges to the inverter as the inverter will only draw 160 amps at 50 volts, with momentary short period being higher for surges and startups. That is more of a breaker/fuse consideration than wire gauge.
is 160 amps for 2 modules, each module needs 80 amps, with surge 100 amps per module will suffice. gouge 1 is sufficient.

sjsamuel
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Re: Battery arrangement/wiring question.

Post by sjsamuel » Fri Aug 21, 2020 11:21 am

pss wrote:
Fri Aug 21, 2020 9:43 am
Okay, here goes. An 8048 can output sustained 8000 watts. At input of 50 volts, that's 160 amps. And from my research, 2/0 wire capacity is 190 amps.

I dug this up (https://www.ecmag.com/section/codes-sta ... electrical): "this section permits aluminum, copper-clad aluminum and copper conductors that are at least 1/0 AWG or larger to be connected in parallel if these parallel conductors are electrically joined at both ends to form a single conductor". then the amperage capacity will be doubled.

In my case, I used all 4/0 connectors from my batteries to the inverter and between batteries. You can use a single run of 2/0 to each inverter and be within specs. Or you can run a single 3/0 or 4/0. I think if you plan on expanding battery capacity in the future, the connections to the buss bar are more important than the connection gauges to the inverter as the inverter will only draw 160 amps at 50 volts, with momentary short period being higher for surges and startups. That is more of a breaker/fuse consideration than wire gauge.
Ok, so this is exactly how I calculated it initially and planned to run 2/0 from the combiner to the 8048s as well. Somewhere in there, I was told I needed 2 sets to match the 2 175amp breakers in the GSLC. I guessed the calculations were based in the potential momentary draw of an 8048, but I’m with you, in that the breakers need to be able to handle that short load, not necessarily the cables. Well, either way, I think I will spring for some 4/0 to each inverter and be done with it. Seems like it should be more than enough. I will use my 2/0 from the batteries to combiner as planned...I’ll have extra, but oh well.

Thanks for all the help folks. Now to get the install started!

I’ve been busy working on balance leads for my packs...this will not be going through a BMS, but I will be manually checking balance on a schedule and using an active equalizer capacitor balancer to keep cells balanced if needed. Hoping that with conservative cut off voltages balance shouldn’t be an issue. Here are some pics for those interested!

https://drive.google.com/file/d/18xvwFk ... p=drivesdk

https://drive.google.com/file/d/1mDQsx ... p=drivesdk

https://drive.google.com/file/d/1J1Cd39 ... p=drivesdk

Can I add pics to the post from files on my goggle drive instead of just a link? How do I do that!

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Re: Battery arrangement/wiring question.

Post by raysun » Fri Aug 21, 2020 11:33 am

FWIW, I'm a far bigger fan of "bottom balancing" lithium cells than of "top balancing".

The chemistry is fundamentally different than lead acid, and the approach to charging and usage should be too.

Without some form of BMS, bottom balancing is the only safe(ish) approach to cell maintenance. Do watch the cells closely and leave plenty of headroom for the inevitable variations in capacity, and make adjustments over time for capacity decline.

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EA6LE-ONE
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My RE system: System 1:
MATE3s, 3 x Radian GS8048A,
4 x FLEXmax 100, HUB10,
2 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 4 x FLEXware ICS Plus,
54 x PANASONIC VBHN325SA17 325W

System 2:
MATE3s, 2 x VFX3648,
2 x FLEXmax 100, HUB10
1 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 2 x FLEXware ICS
21 x PANASONIC VBHN325SA17 325W
Location: Providenciales, Turks & Caicos Isl.

Re: Battery arrangement/wiring question.

Post by EA6LE-ONE » Fri Aug 21, 2020 12:00 pm

sjsamuel wrote:
Fri Aug 21, 2020 11:21 am

I think I will spring for some 4/0 to each inverter and be done with it. Seems like it should be more than enough. I will use my 2/0 from the batteries to combiner as planned...I’ll have extra, but oh well.
So, how you will connect the 4/0 to the positive inputs in the radian? you will go to one module and then splice to the second one? each module in the radian will need to have one breaker on the positive lead.

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Re: Battery arrangement/wiring question.

Post by sjsamuel » Fri Aug 21, 2020 1:29 pm

EA6LE-ONE wrote:
Fri Aug 21, 2020 12:00 pm
So, how you will connect the 4/0 to the positive inputs in the radian? you will go to one module and then splice to the second one? each module in the radian will need to have one breaker on the positive lead.
I’ve got GSLCs with the 8048s, so both 175a breakers are actually busses together at the bottom with a plate. So I can land one 4/0 on this plate to supply both modules right?
raysun wrote:
Fri Aug 21, 2020 11:33 am
FWIW, I'm a far bigger fan of "bottom balancing" lithium cells than of "top balancing".

The chemistry is fundamentally different than lead acid, and the approach to charging and usage should be too.

Without some form of BMS, bottom balancing is the only safe(ish) approach to cell maintenance. Do watch the cells closely and leave plenty of headroom for the inevitable variations in capacity, and make adjustments over time for capacity decline.


I will be watching these cells closely for sure. I really wish there was an easier way to manage/monitor all these packs that are in parallel, and setup failsafes, but I haven’t found a solution yet. I’ve got six of these packs! Any suggestions!!? 😬

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EA6LE-ONE
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Posts: 284
Joined: Tue May 05, 2020 7:51 am
My RE system: System 1:
MATE3s, 3 x Radian GS8048A,
4 x FLEXmax 100, HUB10,
2 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 4 x FLEXware ICS Plus,
54 x PANASONIC VBHN325SA17 325W

System 2:
MATE3s, 2 x VFX3648,
2 x FLEXmax 100, HUB10
1 x EnergyCell 48V 2700RE,
1 x FLEXnet DC, 2 x FLEXware ICS
21 x PANASONIC VBHN325SA17 325W
Location: Providenciales, Turks & Caicos Isl.

Re: Battery arrangement/wiring question.

Post by EA6LE-ONE » Fri Aug 21, 2020 1:35 pm

sjsamuel wrote:
Fri Aug 21, 2020 1:29 pm

I’ve got GSLCs with the 8048s, so both 175a breakers are actually busses together at the bottom with a plate. So I can land one 4/0 on this plate to supply both modules right?
In that case, then you are good with a single 4/0 cable.

raysun
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Hyundai 355 watt panels (6 - 3 strings of 2 in series)
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Re: Battery arrangement/wiring question.

Post by raysun » Fri Aug 21, 2020 2:10 pm

sjsamuel wrote:
Fri Aug 21, 2020 1:29 pm
EA6LE-ONE wrote:
Fri Aug 21, 2020 12:00 pm
So, how you will connect the 4/0 to the positive inputs in the radian? you will go to one module and then splice to the second one? each module in the radian will need to have one breaker on the positive lead.
I’ve got GSLCs with the 8048s, so both 175a breakers are actually busses together at the bottom with a plate. So I can land one 4/0 on this plate to supply both modules right?
raysun wrote:
Fri Aug 21, 2020 11:33 am
FWIW, I'm a far bigger fan of "bottom balancing" lithium cells than of "top balancing".

The chemistry is fundamentally different than lead acid, and the approach to charging and usage should be too.

Without some form of BMS, bottom balancing is the only safe(ish) approach to cell maintenance. Do watch the cells closely and leave plenty of headroom for the inevitable variations in capacity, and make adjustments over time for capacity decline.


I will be watching these cells closely for sure. I really wish there was an easier way to manage/monitor all these packs that are in parallel, and setup failsafes, but I haven’t found a solution yet. I’ve got six of these packs! Any suggestions!!? 😬
Working without a net, I'd definitely keep the cell voltages conservative: maximum 90% and minimum of 20% SoC.

TBH, I did a lot of research and experimentation ahead of deciding to leave the battery design and integration to the professionals, and am opting for SimpliPhi batteries when the time comes.

Even if you choose to not top balance the cells (a good choice, IMO, unless there's a BMS tuned to the specific cell type) some sort of voltage monitor would be desirable. Unfortunately, each cell needs monitoring individually, and I expect the battery has a LOT of cells.

A monitor like the Flexnet DC (which integrates well into the outback ecosystem, of course), or a Victron BMS 7xx series (a good, relatively inexpensive unit) would be capable of monitoring overall battery voltage and provide some relay control to shut down the battery in an over voltage or under voltage event. Neither will monitor individual cells, so being very conservative about the charge and discharge profiles will be prudent.

Lead acid batteries hate being held in a partial state of charge. Lithium batteries love being held in a partial state of charge.

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Re: Battery arrangement/wiring question.

Post by Ampster » Fri Aug 21, 2020 3:47 pm

raysun wrote:
Fri Aug 21, 2020 11:33 am
FWIW, I'm a far bigger fan of "bottom balancing" lithium cells than of "top balancing".
..............
Without some form of BMS, bottom balancing is the only safe(ish) approach to cell maintenance. Do watch the cells closely and leave plenty of headroom for the inevitable variations in capacity, and make adjustments over time for capacity decline.
I guess it all depends on where you are standing. When I was hanging out on DIY EV forums bottom balancing was considered better and safer than having a BMS. I never subscribed to that theory and bought an expensive BMS. I did understand the theory because the most likely scenerio in an EV is that you will abuse it more often trying to get home with a low SOC on your pack than you would charging it to a controlled voltage consistently every time.

Once I bit the bullet and bought an expensive BMS I realized that I could control the setting for when the balancing took place and the BMS would either cutoff my motor controller or force it into limp mode if one cell got low. I became so accustomed to the data from the BMS that when I decided to install a Radian I just naturally installed a BMS. This time it was a little less expensive because it only had to cover 16 cells instead of the 36 in the EV. I have since sold both the EV and moved to another home but I sold the Radian and took the battery to my new home where I have installed a Skybox. Since I was going to charge my pack from solar and take it to near the top every day I parallel top balanced the cells before assembling them in my pack. That worked out well since I had picked an end of charge point for the Skybox that was about 90% of SOC and I never took that pack below 50% SOC.

Today I still use the same old 16 cell BMS that has a lot of features designed for an EV that I will never use and I rarely have to use the balancing function. I do look at the data almost as much as I look at what my Skybox is doing. What has changed a lot since I bought my first BMS is the quantity of 16 cell BMSs in the range of $100 to 200 and I do not see any reason why anyone would risk destroying an expensive Lithium pack by not running a BMS.

I do not agree there it is only approach to cell maintenance. I do see both sides of the bottom versus top balance argument. As far as whether bottom balancing is safer than top balancing, there is no need to debate that since everyone is capable of making their own decisions based on their own risk management profile.
Last edited by Ampster on Fri Aug 21, 2020 8:33 pm, edited 1 time in total.
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Re: Battery arrangement/wiring question.

Post by Ampster » Fri Aug 21, 2020 3:52 pm

sjsamuel wrote:
Fri Aug 21, 2020 1:29 pm
..............
I will be watching these cells closely for sure. I really wish there was an easier way to manage/monitor all these packs that are in parallel, and setup failsafes, but I haven’t found a solution yet. I’ve got six of these packs! Any suggestions!!? 😬
As I mentioned in the previous post there are some inexpensive BMSs that can remove one of the parallel batteries from your pack if it that battery has a problem. As mentioned by others there are also inexpensive monitoring devices that you may also be considering.

I did not see the particulars of what you were using. Tell me more about your batteries?
Are you off grid? I did see that the batteries were 14S so I assume the chemistry is NMC or something similar. I ran Nissan Leaf modules for several years that are similar chemistry.
Drive Tesla Model X and Model 3 which are charged at Super Off Peak rates.

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Re: Battery arrangement/wiring question.

Post by sjsamuel » Fri Aug 21, 2020 9:36 pm

Ampster wrote:
Fri Aug 21, 2020 3:52 pm
As I mentioned in the previous post there are some inexpensive BMSs that can remove one of the parallel batteries from your pack if it that battery has a problem. As mentioned by others there are also inexpensive monitoring devices that you may also be considering.

I did not see the particulars of what you were using. Tell me more about your batteries?
Are you off grid? I did see that the batteries were 14S so I assume the chemistry is NMC or something similar. I ran Nissan Leaf modules for several years that are similar chemistry.
Thanks for the info so far. This whole process actually kinda happened when I was able to get these batteries at an incredible price from a friend. He was buying some to use with his off grid setup and I went in with him and picked up 6 packs. These batteries are new Chevy Bolt batteries(LG packs) that originally came as 36v (10s) packs. My friend did the initial work in actually separating and rearranging these 36v packs to make 48v (14s) packs and these are what I have 6 off. Because of the reconfiguration, I have had to create my own balance leads and the factory balance ports are non functional. My setup with these packs will be to power 2 (eventually 3) Radian 8048s. It will be mostly used for backup power to our grid tied house and the radians are going to AC coupled to my enphase PV system so those can be used during grid outages As well. My wife and I also love the idea of potential for grid independence if necessary, so the expensive has been justified to us.
So when it’s all said and done with my balance leases I can now atleast check the individual cell voltages. When I get my Active Equalizer Balancer, I’ll be able to use to manually balance a pack that maybe out of balance. However, being able to automate balancing of the 6 packs individually or atleast monitoring with pack cut off or even just plain monitoring each pack remotely would sure make life a ton easier.

Not sure if this link will work, but here is a video of me checking all 14 cells of a completed

https://drive.google.com/file/d/1kmsAI ... p=drivesdk

Thanks for the help!

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Hyundai 355 watt panels (6 - 3 strings of 2 in series)
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Re: Battery arrangement/wiring question.

Post by raysun » Fri Aug 21, 2020 10:16 pm

Ampster wrote:
Fri Aug 21, 2020 3:52 pm
sjsamuel wrote:
Fri Aug 21, 2020 1:29 pm
..............
I will be watching these cells closely for sure. I really wish there was an easier way to manage/monitor all these packs that are in parallel, and setup failsafes, but I haven’t found a solution yet. I’ve got six of these packs! Any suggestions!!? 😬
As I mentioned in the previous post there are some inexpensive BMSs that can remove one of the parallel batteries from your pack if it that battery has a problem. As mentioned by others there are also inexpensive monitoring devices that you may also be considering.

I did not see the particulars of what you were using. Tell me more about your batteries?
Are you off grid? I did see that the batteries were 14S so I assume the chemistry is NMC or something similar. I ran Nissan Leaf modules for several years that are similar chemistry.
Yes, having a BMS is what most all the vendors integrate and gets the most from the cells most safely.

The OP stated he did not have one, and is already using cells for testing. "Boots on the ground" calls for bottom balancing with the current setup.

Adding a proper BMS is well worth the investment.

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Re: Battery arrangement/wiring question.

Post by sjsamuel » Sat Aug 22, 2020 6:15 am

raysun wrote:
Fri Aug 21, 2020 10:16 pm
Yes, having a BMS is what most all the vendors integrate and gets the most from the cells most safely.

The OP stated he did not have one, and is already using cells for testing. "Boots on the ground" calls for bottom balancing with the current setup.

Adding a proper BMS is well worth the investment.
I see what you are saying, and I do agree that ideally I would love to have a proper BMS. I guess this is where I’m not sure which direction to go. Does anyone have a recommendation for a proper BMS. I’m assuming I would have to get 6 of them, one for each for the 6 packs right? Anyone with good suggestions for equipment such as this? It seems to me that all BMS options I can find online are off brand Chinese units that I’m not sure I’m comfortable trusting? Maybe I’m wrong, but this seems like a higher chance of a failure point than manually monitoring the cells.

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Re: Battery arrangement/wiring question.

Post by Ampster » Sat Aug 22, 2020 10:07 am

raysun wrote:
Fri Aug 21, 2020 10:16 pm
......... "Boots on the ground" calls for bottom balancing with the current setup.

Adding a proper BMS is well worth the investment.
I am not sure who the "Boots on the ground" authorities you are referring to. Jack Rickard gave up on bottom balancing years ago. Every factory or OEM BMS that I am aware of balances their packs at the knee of the charge curve. That is the definition of top balancing. Bottom balancing is done at the knee of the discharge curve. It is not a convenient process in a production EV because you would have run your pack carefully to near empty and then wait as your BMS somehow continually discharged your cell groups to the same point on the knee of the discharge curve.

I am not sure what the process would be to bottom balance a pack that has the cells welded together. Any ideas about how the OP would do what you suggest?
As a practical matter bulk balancing a pack like that is impossible because the cells are welded together. The only way to bottom balance would be to individually take each cell to a minimum voltage. That could take weeks. It would be faster to individually take each cell to the top since they are already at a SOC of nearly full.

Of course the the important question is, does this pack need balancing? I would submit that it came out of a pack that was top balanced by the factory BMS because, as explained above, that is how all BMSs operate. They add or subtract current and the knee of the charge cycle. Therefore a good hypothesis is that this pack is already balanced at the top. That hypothesis can be checked by charging each pack while observing the voltage differences of the cells.

I agree that adding a BMS is worth the investment. I have been using an Orion Jr BMS but it costs $500 and that would be an investment greater than the OP probably has in his batteries for six of them. There are several tiers of BMSs at much lower prices but they are all manufactured in China. I have been participating in another forum in which many users have tested and are using multiple Chinese BMSs with some success. Those are "Boots on the ground" that might give the OP some comfort. Or as he has already assumed the role, he can be the BMS.
Last edited by Ampster on Sat Aug 22, 2020 10:24 am, edited 2 times in total.
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Re: Battery arrangement/wiring question.

Post by Ampster » Sat Aug 22, 2020 10:20 am

sjsamuel wrote:
Fri Aug 21, 2020 9:36 pm
......
Thanks for the info so far. This whole process actually kinda happened when I was able to get these batteries at an incredible price from a friend. ...........
Thanks for the information on your pack. I posted a response to the comment by @raysun above but most of the content was intended for you. I take issue with his insistence on balancing when there is no evidence that the pack is even out of balance.

On another note, I have an Outback Skybox and have been AC coupling it successfully to some Enphase IQ-7s and a Solaredge inverter. Several years ago I had a Radian but sold it when I moved and before it was capable of AC coupling. I currently live in the wine country of Northern California and my system is in my signature and sidebar. We often get power outages so one of the benefits of my system is to carry me through those.

We share the same goals of becoming more self sufficient. As you move toward that goal share your thoughts because it will become instructional to other readers as you analyze your consumption patterns.
Drive Tesla Model X and Model 3 which are charged at Super Off Peak rates.

raysun
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My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Battery arrangement/wiring question.

Post by raysun » Sat Aug 22, 2020 10:21 am

Ampster wrote:
Sat Aug 22, 2020 10:07 am
raysun wrote:
Fri Aug 21, 2020 10:16 pm
......... "Boots on the ground" calls for bottom balancing with the current setup.

Adding a proper BMS is well worth the investment.
I am not sure who the "Boots on the ground" authorities you are referring to. Jack Rickard gave up on bottom balancing years ago. Every factory or OEM BMS that I am aware of balances their packs at the knee of the charge curve. That is the definition of top balancing. Bottom balancing is done and the knee of the discharge curve. It is not a convenient process in a production EV because you would have run your pack carefully to near empty and then wait as your BMS somehow continually discharged your cell groups to the same point on the knee of the discharge curve.

I am not sure what the process would be to bottom balance a pack that has the cells welded together. Any ideas about how the OP would do what you suggest?
As a practical matter bulk balancing a pack like that is impossible because the cells are welded together. The only way to bottom balance would be to individually take each cell to a minimum voltage. That could take weeks. It would be faster to individually take each cell to the top since they are already at a SOC of nearly full.

Of course the the important question is, does this pack need balancing? I would submit that it came out of a pack that was top balanced by the factory BMS because, as explained above, that is how all BMSs operate. They add or subtract current and the knee of the charge cycle. Therefore a good hypothesis is that this pack is already balanced at the top. That hypothesis can be checked by charging each pack while observing the voltage differences of the cells.

I agree that adding a BMS is worth the investment. I have been using an Orion Jr BMS but it costs $500 and that would be an investment greater than the OP probably has in his batteries. There are several tiers of BMSs at much lower prices but they are all manufactured in China. I have been participating in another forum in which many users have tested and are using multiple Chinese BMSs with some success. Those are "Boots on the ground" that might give the OP some comfort. Or as he has already assumed the role, he can be the BMS.
I looked at the Orions, and they looked the most promising, at least they looked the least sketchy. They seem more oriented to the EV crowd than the RE crowd, however.

I don't know the person referred to above or his experiences and motivations, however agree that "naked" cells is fairly high risk. While LiFePo4 isn't at risk to burn one's house down, it doesn't mean they are inherently stable. Without a minder of some sort, the likelihood of cell failure increases, one would think. Other Li technologies i would not touch with a 10 foot fire extinguisher unless there was a bulletproof BMS in place. Most of the one's I looked into seemed susceptible to bullets.

OP was asking for specific BMS and configuration recommendations for his system. With your Li DIY experience, do you have such a recommendation?

raysun
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Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Battery arrangement/wiring question.

Post by raysun » Sat Aug 22, 2020 10:31 am

Ampster wrote:
Sat Aug 22, 2020 10:20 am
sjsamuel wrote:
Fri Aug 21, 2020 9:36 pm
......
Thanks for the info so far. This whole process actually kinda happened when I was able to get these batteries at an incredible price from a friend. ...........
Thanks for the information on your pack. I posted a response to the comment by @raysun above but most of the content was intended for you. I take issue with his insistence on balancing when there is no evidence that the pack is even out of balance.

On another note, I have an Outback Skybox and have been AC coupling it successfully to some Enphase IQ-7s and a Solaredge inverter. Several years ago I had a Radian but sold it when I moved and before it was capable of AC coupling. I currently live in the wine country of Northern California and my system is in my signature and sidebar. We often get power outages so one of the benefits of my system is to carry me through those.

We share the same goals of becoming more self sufficient. As you move toward that goal share your thoughts because it will become instructional to other readers as you analyze your consumption patterns.
I'm not insisting on anything and take exception to your implications. I will say you claim and likely possess more practical experience with DIY Li, and have made some generalist statements regarding implementation. Nothing in the posts, however, are applicable without a considerable amount of experimentation by the OP. It would be far better if you laid out specific guidance for implementing a BMS on his battery packs.

Perhaps the conflagrations in your area are dividing your attention, and rightfully so, but when you have time to focus on specifics, I'm sure OP would appreciate more actionable guidance.

As for me, I've exhausted the sum of my experience in this area and sign off wishing everyone the best of luck for positive outcomes in their respective situations.

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My RE system: 5.7K solar system with Solaredge inverter. Heat pump water heater.
28 kWh pack of LFP batteries powering a Skybox which is used for load shifting and backup.
Location: Sonoma, Northern California

Re: Battery arrangement/wiring question.

Post by Ampster » Sat Aug 22, 2020 11:07 am

raysun wrote:
Sat Aug 22, 2020 10:21 am
..............
I looked at the Orions, and they looked the most promising, at least they looked the least sketchy. They seem more oriented to the EV crowd than the RE crowd, however.
Yes, that is my issue with the Orion, it has many features that I do not need since it was designed for EVs.
I don't know the person referred to above or his experiences and motivations, however agree that "naked" cells is fairly high risk.
Jack Rickard is the founder of evtv.me. He has published hundreds of videos about converting EVs. Several years ago he gave up on that, bought several Teslas and moved on to renewable energy. He sells Tesla packs bundled with inverters and his own software arduino based BMS. I am still waiting for you to explain who the "Boots on the ground" you were referring to, or how you suggest that the OP bottom balance those batteries?
.........
OP was asking for specific BMS and configuration recommendations for his system. With your Li DIY experience, do you have such a recommendation?.
There are some choices below the cost of an Orion but on a multiple of six, considerably more expensive than the Chinese products. Zeva in Australia has one. Thunderstruck Motors has one. Emus has one with a 100 Amp cutoff that would disconnect an individual battery from the pack if it was getting stressed. Unless the OP has a budget of $2000 for the above, my only suggestion is to go to diysolarforum.com and read the reviews of BMSs like Daly, Chargery, Electrodacus and others. Some of those are sub $100 and have basic functionality without all the bells and whistles of those that are designed for EVs. There are many examples of successful implementations.

One has to be willing to be a DIYer to find value in that kind of implementation. My 28 kW pack of new LFPs cost $125 per KWh which is significantly less expensive than SimpliPhi at around $700per kWh. The difference is the economic reward for taking on the task of understanding how to assemble a pack, wire a BMS and interface it to your inverter. I am not suggesting one path is better than the other. As I often say, it all depends on where you are standing.
Last edited by Ampster on Sat Aug 22, 2020 12:08 pm, edited 1 time in total.
Drive Tesla Model X and Model 3 which are charged at Super Off Peak rates.

Ampster
Forum Guru
Posts: 119
Joined: Sat Apr 11, 2015 5:14 pm
My RE system: 5.7K solar system with Solaredge inverter. Heat pump water heater.
28 kWh pack of LFP batteries powering a Skybox which is used for load shifting and backup.
Location: Sonoma, Northern California

Re: Battery arrangement/wiring question.

Post by Ampster » Sat Aug 22, 2020 11:39 am

raysun wrote:
Sat Aug 22, 2020 10:31 am
.........
I'm not insisting on anything and take exception to your implications. I will say you claim and likely possess more practical experience with DIY Li, and have made some generalist statements regarding implementation. Nothing in the posts, however, are applicable without a considerable amount of experimentation by the OP. It would be far better if you laid out specific guidance for implementing a BMS on his battery packs.
I did not mean to chase you off. You have made important contributions to the wiring part of this thread.

You did repeat the recommendation about bottom balancing with an appeal to some anonymous authority that you have chosen not to identify. Perhaps insistence was two strong a word? You said you were a fan of bottom balancing but I gather you have had no practical experience with Lithium batteries and are just repeating some things that you have read. Your opinion is noted, but I assume no specifics about how he should bottom balance will be forthcoming?
.....I'm sure OP would appreciate more actionable guidance.
I am happy to give the OP some guidance but you are correct, I can't assume he wants to take on that task. At this point we don't even know if the batteries need balancing. Since for the moment he has decided to be the BMS I would suggest that he make observations of the cell voltages as he slowly increases the maximum voltage (Absorb or Constant Voltage) setting on his inverter.

The hypothesis about the pack balance will be clear if one cell group starts to rise more than 20 millivolts above the others or approach the maximum voltage per cell of that chemisty of 4.20 volts before the others do. The following manual top balance approach has worked for me. I use a one Ohm 50 Watt resistor attached to alligator clips to pull down that cell until it is close to the value of the other cells. The resistor will get hot. This only works at the knee of the charge curve where the voltage rises quickly for that chemistry. That point is probably above 3.9 volts. The charge curve below that is too flat to give you any meaningful data to compare voltage of each cell. That process is known as manual top balancing. It is what a shunt based BMS does but on a much slower basis. I am happy to elaborate.
NOTE to @sjsamuel
After rereading this thread i realize you have already bench tested these batteries and are running them at a conservative voltage range. If you have not notice any cell drift when you took them to 4.05 per cell you can presume that those batteries are fairly well balanced and you can ignore my advice above. I had a Nissan Leaf pack consisting of various vintage used modules and I ran it with conservative values like that with no issues. Also my apologies for any hijack of this thread. Ping me if you want to continue any discussion on monitoring or management strategies of your pack.
Drive Tesla Model X and Model 3 which are charged at Super Off Peak rates.

sjsamuel
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Re: Battery arrangement/wiring question.

Post by sjsamuel » Sat Aug 22, 2020 7:09 pm

@rayson
Thanks again for all the help! I have appreciated your input in helping me understand all this better. I honestly don’t understand the advantages/disadvantages of bottom vs top balancing, and this I will look into and research more as well.
I’ve been using Lithium Poly batteries in large RC helicopters for more than 10 years now, and although I know its not the exact same thing, and this is a lot larger scale application, the 12s 5000mah packs we use for these machines are abused pretty hard and we usually abuse the packs in charge as well pushing 3-5c a lot of times during charge cycles. Even with this kind of abuse, one thing I’ve noticed is that if you don’t over discharge or over charge the pack the cells tend to hold balance really well even after hundreds of cycles.
At this point I think I will be watching these six packs closely when I start cycling them with the Radians. I have done a little bench testing, but have not gotten the packs up higher than 3.9 volts yet. I spent the time and effort to solder balance leads and as seen in the video above I can easily check each cell voltage and will be manually doing so. In the meantime, I do plan to keep researching and looking for a BMS setup of some kind that will allow me some relief of having to manual manage the system, and hope to find it.

sjsamuel
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Posts: 30
Joined: Thu May 28, 2020 9:30 pm

Re: Battery arrangement/wiring question.

Post by sjsamuel » Sat Aug 22, 2020 7:20 pm

@Ampster
You have obviously spend some time in the same ditch that I am in now, and have a larger and better understanding of DIY battery setups, and I really thank you for all the info so far. I briefly looked at the Orian BMS system, and I looked good, but you are correct in that those are pretty expensive.
As I posted above to Raysun, I do feel at this point, I will be keeping a very close eye on the cells manually, and as you put it, I will be essentially playing the role of BMS myself.
I purchased on the these..still waiting delivery..
https://www.amazon.com/gp/product/B07SF ... UTF8&psc=1

My friend that sold me the batteries has been running 10 of these packs with this off grid setup now for several weeks and he has kept an eye on his cells to note that they are holding balance very well so far. His cut of voltages are 3.4-4.05.
I hope to have the same results, and will hope this above active balancer will be able to do essentially what you were doing with the resistor to fix any deviations I may see.

In the meantime, I will definitely check out all the options you suggested for BMS. I also will check out diysolarforum.com and do some research there for options.

I may take you up on some questions as I move forward and will ping if you as you offered. Thanks a lot for that.

This forum has been a lot of help, and I can’t wait to get all this setup. Still a LOT left to do on the AC side of the project and my load center, but I hope to have the batteries and inverters hung in the next week or so, and get the DC portion of it done before the electricians start on the AC side. Will probably start a thread in the Radian subforum on my progress if it will help some others with their projects as well.

Thanks again.

Ampster
Forum Guru
Posts: 119
Joined: Sat Apr 11, 2015 5:14 pm
My RE system: 5.7K solar system with Solaredge inverter. Heat pump water heater.
28 kWh pack of LFP batteries powering a Skybox which is used for load shifting and backup.
Location: Sonoma, Northern California

Re: Battery arrangement/wiring question.

Post by Ampster » Sat Aug 22, 2020 8:25 pm

Those batteries are made by LG Chem I believe and are good quality. It is good you have had experience with Lipos but I am glad you are not using them to power your home. I have heard good things about those balancers. The only negative thing I remember is don't leave them plugged in permanently because if they fail they can pull one cell down. I suspect you have already figured that out because that is the way Lipos are balanced and you have probably set up your balance wires with connectors.
Good luck with you system.
Drive Tesla Model X and Model 3 which are charged at Super Off Peak rates.

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