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diy solar

How to correctly install a ACTIVE CELL BALANCER to Lifepo4

The parameters are all adjustable, you can use it on any chemistry. All of the cell protection voltages can be set anywhere from 1.25 to 4.25 volts. The over current can be set from 10 to 200 amps. And it also gives you a delay for over current shut off and release from 2 to 120 seconds.

As for the caps being close to the FET's, I don't see the board layout as an issue. The large "super caps" are nearly an inch away, and the few other electrolytic can caps are even further. They are all labeled as 105C caps, and the BMS will shut down the current flow if the FET's get to 75C. That should give a fairly good life. And at the currents I am running, I have not seen the FET's get over 55C yet. I have found one of my old heat pipe Pentium 4 CPU coolers, I am going to mount it on the BMS case directly over the FET's and add a temp controlled fan if it get's warm at all. If I feel the case is getting too warm, I could cut a hole around the caps and add a small fan to move air through the BMS case to cool all of the components.

Once I have the battery bank inside the rack enclosure, it will also have another fan to move air across all of the cells. I have yet to see any of the cells even get to 40C yet. I have not hit 100 amps on cells rated to over 600 amps continuous. I was a bit torn on the case. I decided to go with a rack cabinet with vented doors to allow more air to move around the cells. If it ever does catch on fire, the chassis is still all steel. Smoke may get out of the vents, but I don't think it will catch anything around it on fire. And then vents will also allow a fire extinguisher to get in without having to open it up. I would expect the temp sensors to give me a decent warning before anything would burn as well. The cells should be as safe as they are when installed in a Chevy Bolt. People park them in their garage all the time.
 
GXMnow said:
I have to agree that any form of BMS is way better than no BMS. But you do have to make sure it is compatible with your cells. The smart ones do let you adjust parameters, most of the cheap ones do not. I have mine set to protect the cells, but the inverter/charger should be set to shut down well within the safe range so that the BMS is just an extra safety valve in case something goes wrong. If the BMS starts shutting down early, it may be a sign that the cells are going out of balance, and you may need more balance current.

I don't have my hybrid inverter/charger yet, so I still can't say how good my JiKong BMS is, but at 600 watts of test charging and loading, it seems good so far.

Ampster...
How long have you had the Skybox? I almost placed my order for a Schneider XW-Pro, but as usual, I study everything to death, and the Outback Skybox is looking very good. The 5,000 watts is enough for me, and having it all in one box actually makes it a little cheaper. I will be AC coupling 16 Enphase iQ7's to it. My peak solar output goes to about 3,860 watts when the inverters start to clip when it is cool and sunny. In the summer heat, I am peaking in the 3,500 watt area and producing 28 KWH a day. My main use of the battery bank is going to be "time of use" shifting. For ToU, the Outback software sounds better, especially with the external CT's included. Are you using that function? Have you had any issues?
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I'm planning on getting a Jikong BMS, how has yours been faring? Will you still recommend it as a good buy? Thanks a lot.
 
So far my JK BMS has been working perfectly. Th only odd issue I have had is when I turn on a cheap 48-12 volt DC-DC converter, the switching noise is causing errors in the cell voltage readings, but it returns to dead accurate when I shut the converter back off. I tried adding a filter on the input side and it helped some, I will next try adding one on the output, I think the noise is transmitting. This is not a BMS problem, it is the noise out of the cheapo buck switching converter.

Mine is the 200 amp rated, most I have run is 80 amps, it barely got warm. The bluetooth range is a bit short, but not really a problem. Biggest pain s getting it to turn on the first time. You need to supply a charging voltage that is at least 5 volts higher than your battery pack to trigger it to start. That is not well documented and some people, including me, think the board is dead when it does nothing. My battery was near full charge, so my CC CV charger, was only 1 volt higher so it would not fire up. Checking it right now, the BMS has been powered up for 139 days straight without an issue. The pack is balanced within 0.003 volts from highest to lowest cell. I have cycled 12972 amp hours in and back out of the pack. Air temp in my garage is about 21C right now. That is the same reading I am getting on the battery case. The mosfets are showing at 25C while it is carrying almost 30 amps right now. When I build another battery bank, I will likely buy another of these.
 
GXMnow said:
So far my JK BMS has been working perfectly. Th only odd issue I have had is when I turn on a cheap 48-12 volt DC-DC converter, the switching noise is causing errors in the cell voltage readings, but it returns to dead accurate when I shut the converter back off. I tried adding a filter on the input side and it helped some, I will next try adding one on the output, I think the noise is transmitting. This is not a BMS problem, it is the noise out of the cheapo buck switching converter.

Mine is the 200 amp rated, most I have run is 80 amps, it barely got warm. The bluetooth range is a bit short, but not really a problem. Biggest pain s getting it to turn on the first time. You need to supply a charging voltage that is at least 5 volts higher than your battery pack to trigger it to start. That is not well documented and some people, including me, think the board is dead when it does nothing. My battery was near full charge, so my CC CV charger, was only 1 volt higher so it would not fire up. Checking it right now, the BMS has been powered up for 139 days straight without an issue. The pack is balanced within 0.003 volts from highest to lowest cell. I have cycled 12972 amp hours in and back out of the pack. Air temp in my garage is about 21C right now. That is the same reading I am getting on the battery case. The mosfets are showing at 25C while it is carrying almost 30 amps right now. When I build another battery bank, I will likely buy another of these.
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Thank you for your informative reply. I'm planning on getting same 200A active BMS for my 8s battery system and will surely have need to get this boost DC converter which I'm hoping won't add noise that may affect the working properties of this JK BMS.
 
My 48 to 24 volt buck converter is not causing any problem, only the 48 to 12 volt one is. I don't need it on all the time now, so I have not been in a hurry to test adding more filters. From the few tests I have done, it does seem to be output noise radiating to the balancer cell leads. My input side filter virtually removed any measurable noise on the battery input side, but I still can see the 150 khz spikes on the output and the wires are only 6 inches apart. I will try unbolting the panel with the buck converters and see what happens with it a few feet away from the BMS. If that works, I may just put them in a separate box on the wall instead on inside the battery bank enclosure.
 
GXMnow said:
My 48 to 24 volt buck converter is not causing any problem, only the 48 to 12 volt one is. I don't need it on all the time now, so I have not been in a hurry to test adding more filters. From the few tests I have done, it does seem to be output noise radiating to the balancer cell leads. My input side filter virtually removed any measurable noise on the battery input side, but I still can see the 150 khz spikes on the output and the wires are only 6 inches apart. I will try unbolting the panel with the buck converters and see what happens with it a few feet away from the BMS. If that works, I may just put them in a separate box on the wall instead on inside the battery bank enclosure.
Click to expand...
Thank you for this, will definitely be mindful of these when mine arrives. I'll also consider installing it separately too.
 
I have a test pack of 8 cells and I just ordered the 8 cell balancer. I am interested how it interfaces with my BMS before I go all in on a 16S balancer.
 
TGPB said:
Will this work sufficiently for my 280ah 4S batteries?
Heltec 3S 4S 5A Active Equalizer Balancer Lifepo4
Click to expand...
This board does do "active balancing" but it does not use the switching converter like the larger Heltec/JK units. So the balance current is directly related to the voltage difference. At a full 100 mv difference, it can still only provide 1 amp of balance current. At a 10 mv difference, the current drops to just 0.1 amp. The one advantage it does have is that it can pull and push current from multiple cells at the same time. My JK active balancing BMS can only pull or push just one cell at a time, but it can do the full 2 amps even at just a few mv difference.

Here is the inductive version. It can move more current at a lower difference voltage.

But it is still limited in that it only moves to the adjacent cells and still stops at a 30 mv difference. To get the switch mode super capacitor active balancing that can balance to under 10 mv, the cost jumps up a lot.
 
I have one cell that is taking off just before my cells get to 3.4v so the BMS is stopping the charging. I am hoping it will keep that one cell in check long enough for the other 3 cells to reach 3.4v
 
GXMnow said:
This board does do "active balancing" but it does not use the switching converter like the larger Heltec/JK units. So the balance current is directly related to the voltage difference. At a full 100 mv difference, it can still only provide 1 amp of balance current. At a 10 mv difference, the current drops to just 0.1 amp. The one advantage it does have is that it can pull and push current from multiple cells at the same time. My JK active balancing BMS can only pull or push just one cell at a time, but it can do the full 2 amps even at just a few mv difference.

Here is the inductive version. It can move more current at a lower difference voltage.

But it is still limited in that it only moves to the adjacent cells and still stops at a 30 mv difference. To get the switch mode super capacitor active balancing that can balance to under 10 mv, the cost jumps up a lot.
Click to expand...
I thought this balancer was better, which one do you recommend quality / price? I only need for 4 cells and the active balancer of jk costs about 100eur, it is expensive for only 4 cells, if I had a bank of 16 or more cells it would be profitable. but it hurts to pay the same for the same device for 4 as for 20 cells.
 
Active cell balancers with inverters waste 15% of the power between the cells and do so by moving from Cell A->B->C->D when A is too high and D is too low. I'm using active cell balancers on all of my ShunBin batteries (without inverters) and not using any balancing on my two new home built 400ah packs. The new packs are remaining at 0.002v while the shunbin packs using the low current 1.2A max active balancers are 0.004v and 0.012v when both used to get so out of balance they would become almost useless.

If you need a 5a balancer, maybe it is better to look at why that one cell is so out of balance? If the internal resistance of one of your cells is so far out based on the rest of the pack, it is telling you that cell needs to be replaced. In this case, I would take that pack out of the bank and slow charge it until it is top balanced. If that didn't work, I'd perform a slow bottom balance followed by a slow charge / top balance. If that didn't work, I add the 1.2A active balancer and let it go until that no longer works and that would mean I have to replace or repurpose the battery.

BMS balancers usually only work during the charge or without a load, this is why I use active balancers on batteries beyond their 'honeymoon period'. Using the higher power balancers do not make sense to me because if the batteries are getting so out of balance to be 0.5v out, there is a much bigger problem that needs to be resolved.
 
mandrews44 said:
Take the next wire to the ground wire on the plug and connect to the next cell in the pack that would be the + side of the negative terminal.
Click to expand...
Hey there. Wondering if you're still around to answer a question or three about this process!

I'm getting ready to connect my home made (crimped and soldered, like yours) balance wires to my Watchmon 7 Batrium BMS. They are helpful to some extent but, very slow in responding to emailed questions.

Reading what you write above, I am confused. I think I get the logic of the ordered sequence of the wires, and want to address that separately but, you say "...connect to the next cell in the pack that would be the + side of the negative terminal." If the neg and pos terminals are joined by a busbar in series, does it really matter which terminal of the two the balancing wire's ring terminal goes on?

Any help will be appreciated!
 
Fallingaway said:
Thought I’d share this but I found that if you pull the insulation off the crimp part, crimp it, then Solder your wire in the crimp valley on top. It’s easy to solder, you can see if t ever comes loose unlike if it’s in the crimp, and at least for me I’m always running out of eyelets so I just unsolder old ones because it’s easy to reuse them that way.
Click to expand...
I have heard solder-only advised against for mobile applications though; can break easily in the bouncing... makes sense to me. I crimped, and soldered.
 
lance said:
If the neg and pos terminals are joined by a busbar in series, does it really matter which terminal of the two the balancing wire's ring terminal goes on?
Click to expand...
Anywhere on the bus is fine. I drilled and tapped my bars for a 6-32 brass screw to keep this connection separate.
 
lance said:
If the neg and pos terminals are joined by a busbar in series, does it really matter which terminal of the two the balancing wire's ring terminal goes on?
Click to expand...
No it doesn't matter. you can test your understanding by using a multimeter. Put the negative of the multimeter on the single negative of the pack and then sequentially touch the positive lead of the multimeter to each series connection. You should see the voltage increase by increments of about 3.3 volts. The last single positive will be your pack voltage.
 
lance said:
I have heard solder-only advised against for mobile applications though; can break easily in the bouncing... makes sense to me. I crimped, and soldered.
Click to expand...
You have heard correctly. Therefore I only crimp and do not solder. Any solder connection stiffens the wire so it is more likely to break.
 
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