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My 64kwh BYD battery bank

Maast

Maast

Compulsive Tinkerer
Joined
Oct 31, 2019
Messages
773
Location
Washington State
Finally got my 18 module BYD bank complete. It's the most polished turd you'll ever see. About 6 months of stripping, cycling, testing and correcting. 2160lbs. I ended up adding 65ish 15ah cells to correct the undercapacity cells in the modules.

Each cell is paralleled with 6 gauge wire and attached with a 100a fusable link thats soldered to the bar.

I'm rather proud of my turd. When I'm totally done I'll have plexiglass doors and the exposed copper will be painted with clear plastidip. It's a massive arc hazard as it is.

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What happens when your wife wants to move .... gonna have to get a LOT of help. LOL
 
Bob B said:
What happens when your wife wants to move .... gonna have to get a LOT of help. LOL
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hah, that thing's staying there forever. If we move I'll build a new bank - out of 280ah cells. I figured out I could fit 288 of the 280ah cells in the space the BYD modules take up. I figure I'll run on this for a decade or so then swap out with whatevers current at the time.

In a few years I'd like to add another parallel bank of around 60 kwh. I want to get as close as I can to time-shifting summer solar overproduction into my dreary PNW winter.
 
Nice work...I am running a similar wall and find the batts like 55v three hour absorption, 53.8v float..
 
Maast said:
Finally got my 18 module BYD bank complete. It's the most polished turd you'll ever see. About 6 months of stripping, cycling, testing and correcting. 2160lbs. I ended up adding 65ish 15ah cells to correct the undercapacity cells in the modules.

Each cell is paralleled with 6 gauge wire and attached with a 100a fusable link thats soldered to the bar.

I'm rather proud of my turd. When I'm totally done I'll have plexiglass doors and the exposed copper will be painted with clear plastidip. It's a massive arc hazard as it is.

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Looks great!

What did you end up doing for a monitor or management system?
 
solardad said:
Looks great!

What did you end up doing for a monitor or management system?
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Monitoring is a Chargery 16T with two Gigavac contactors and for balancing I went with the JK BMS (aka Heltec) 10A supercapacitor active balancer.

Now that I finally got all the paralleling connections done I can permanently mount them - up until now I've been using alligator test leads to connect things together.

Edit: I forgot to mention the SOC monitoring is being done by a Bogart Trimetric. The Radian/Mate3s has another set of shunts for it's SOC monitoring.
 
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Maast said:
Monitoring is a Chargery 16T with two Gigavac contactors and for balancing I went with the JK BMS (aka Heltec) 10A supercapacitor active balancer.

Now that I finally got all the paralleling connections done I can permanently mount them - up until now I've been using alligator test leads to connect things together.
Click to expand...
In regards to the balancer.

Have you found a bad crimp yet on your alligator wire set? Second time I used mine I had a bad connection and found the wires are Way over crimped on the terminals in the plug. So much so that they literally break right off with little effort. In addition to that, With the length of wire and gauge size I'm not sure we're getting the full 10amps to the battery.
As stout and nicely built that they look, they are unfortunately no good. I have also found that the 10a is just not enough for my packs even under lite use.
 
Maast said:
Monitoring is a Chargery 16T with two Gigavac contactors and for balancing I went with the JK BMS (aka Heltec) 10A supercapacitor active balancer.

Now that I finally got all the paralleling connections done I can permanently mount them - up until now I've been using alligator test leads to connect things together.
Click to expand...

I have the baby brother to the 10a (2a version) and I love it. I'll be interested in how the setup and operation works for you since I have not 'seen' it in action by a member or found a review. good luck
 
Huck said:
In regards to the balancer.

Have you found a bad crimp yet on your alligator wire set? Second time I used mine I had a bad connection and found the wires are Way over crimped on the terminals in the plug. So much so that they literally break right off with little effort. In addition to that, With the length of wire and gauge size I'm not sure we're getting the full 10amps to the battery.
As stout and nicely built that they look, they are unfortunately no good. I have also found that the 10a is just not enough for my packs even under lite use.
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You could double or triple up on the non-bluetooth 5A capacitive balancer Helec/JK has. Its amperage is proportional to the voltage differential but it'll do the full 5A and even a little above according to reviews.

I havent had any problems with the balancer so far in my test connections to play around with it - but it doesnt matter since the leads are too short for the unit to sit on the top row and reach down to the middle of the pack so I'm cutting the ends off and splicing in longer wires that'll be soldered directly to the copper paralleling bars just below row five.

I want it to pulse the entire cell group more-or-less evently. I used 6 gauge wire to parallel for the reduced resistance not for the carrying capacity. If I have more than 20a going to/from a single cell I have a problem. All the gross capacity mismatch inside the modules should have been already handled by me adding capacity directly to it.
 
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Maast said:
You could double or triple up on the non-bluetooth 5A capacitive balancer Helec/JK has. Its amperage is proportional to the voltage differential but it'll do the full 5A and even a little above according to reviews.

I havent had any problems with the balancer so far in my test connections to play around with it - but it doesnt matter since the leads are too short for the unit to sit on the top row and reach down to the middle of the pack so I'm cutting the ends off and splicing in longer wires that'll be soldered directly to the copper paralleling bars just below row five.

I want it to pulse the entire cell group more-or-less evently. I used 6 gauge wire to parallel for the reduced resistance not for the carrying capacity. If I have more than 20a going to/from a single cell I have a problem. All the gross capacity mismatch inside the modules should have been already handled by me adding capacity directly to it.
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From my experience you could not parallel the balancers. As one would pull current the other one would push current on the same cell. Unless.. there was some way to sync them or I'm entirely missing something?!?
 
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solardad said:
I have the baby brother to the 10a (2a version) and I love it. I'll be interested in how the setup and operation works for you since I have not 'seen' it in action by a member or found a review. good luck
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There are two members that I know of that have large BYD packs that are being actively used: @Darkstar and @jasonhc73 and both have said there has been zero further degradation. A guy on Youtube called David Poz also has a big BYD pack. David and Darkstar paralleled his at the cell level like I did and seemed happy with the results. Jason has not and has struggled with the available cycling window.

There guaranteed to be at least 1 or 2 15-20ah undercapacity cells in the modules, odds are cell 8 will be one of them. If you look closely you can see the green wires that go from the module connection bars to the correcting cells.
 
Huck said:
From my experience you could not parallel the balancers. As one would pull current the other one would push current. Unless.. there was some way to sync them or I'm entirely missing something?!?
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You've more experience with them than I have. I've just read about them.
 
Maast said:
You've more experience with them than I have. I've just read about them.
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Your turd turned out really nice. I'm moving 4 of my little turds into my cargo trailer real soon. I've gone to the shiny and new side with 280ah cells.

I really do recommend the balancer, it has made these BYD's super stable.
I can and regularly draw them down to 44.0V. But I still can't get them to charge much over 53.1.
I bulk at 58.4V, float at 53.1V, and cut off at 44.0V. On bright sunny days, the charge gets up to 54.1V or 54.2V, but discharges to 52.8V~53.1V pretty much instantly. I don't recommend the cut-off being lower than 47.0V without an active balancer.

Since you don't use the high-resistant tracing as I did, you will be able to get a lot more balancing current. These cells stay balanced with the active balancer a lot better than expected.

I use this one:
www.ebay.com

2S ~ 16S 2A Active Balancer Li-ion Lipo Lifepo4 LTO Battery Equalizer BMS APP JK | eBay

â Support all pool types such as : Li-ion, Lipo, Lifepo4, LTO, super capacitors and other batteries. It is only balancer, it is not protection board.
www.ebay.com
I am limited to 1 amp, and sometimes less because there is so much measured resistance from the line tracing being so small.

"Meta Grid" uses the 5 amp version on his entire "battery".
@solardad The 5 amp version in use:


diysolarforum.com

Another Cargo Trailer setup.

This is now officially a legitimate sickness. My 4th off-grid system: The players: This setup is actually cheaper than going with a PWM Hybrid all in one unit 48V unit. I have AC input to charge the 48V batteries with shore power. (The 21.99 charger) A way more than I will use MPPT battery...
diysolarforum.com diysolarforum.com

ps - 18 BYD packs is about 36 kWh.
 
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