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diy solar

the easy way to keep your cells balanced is...active balancing

So, I'm new to all of this, is it best to use a "active balancer" for balancing and a BMS for the temp/overcharge/undercharge protections and leave the balancing part off?

And, why do Lithium batteries not self balance?
 
So, I'm new to all of this, is it best to use a "active balancer" for balancing and a BMS for the temp/overcharge/undercharge protections and leave the balancing part off?

And, why do Lithium batteries not self balance?
yes...that is what I always do now.
After spending some time watching what the BMS balancers do (which is basically nothing); I just turn it off so it cannot interfere with a real balancer.
You definitely want A BMS for all those other great functions that will keep your batteries from doing "bad things"!
 
So, I'm new to all of this, is it best to use a "active balancer" for balancing and a BMS for the temp/overcharge/undercharge protections and leave the balancing part off?
Yeah, that works. That's actually what I have been doing. I have the balancing function of the BMS turned off. However, that's mainly so I could test the active balancing without the BMS participating.
And, why do Lithium batteries not self balance?
Each cell doesn't know the state of charge of the other cells. How exactly could they "self balance"?
 
Yes, I've been using the v1.3 hardware (8S) as well. In my testing it has done a good job of balancing.
Thanks on that. Any special instructions? I was planning the same cells as the Daly leads; B- then each positive.
 
Thanks! This is the one I got a month ago and plan to install over the weekend. J
looking at the picture you have an inductive balancer instead of capacitive(maybe) so make sure to post how well it does...
if you have a good multimeter check each of your cell voltages so you know exactly what is going on before you plug it in.
You should be able to quickly (well, relatively quickly hehe) see your max voltage cell dropping and your min increasing.
Some balancers have start/stop trigger points instead of "always on"; its hard to get actual design specs so often the only way to figure it out is to test it.

check you voltages hourly and you should see a difference. If nothing is happening you may be in a balance inactive zone (the worst case cell difference is not enough to trigger the balance circuitry). When I was testing some balancers I have to use a resistor and purposely drain one cell to cause a big enough imbalance for them to kick in.

I did my first tests with the batteries disconnected fromthe charger, then I tested with the charger. Active balancers are NOT like the resistive ones that are just burning off energy. Actives should be moving energy from high cells to low cells so no need to have the charger connected AND you should not see all the cells only dropping in voltage; high cells should be dropping, AND low cells should be rising.
 
looking at the picture you have an inductive balancer instead of capacitive(maybe) so make sure to post how well it does...
if you have a good multimeter check each of your cell voltages so you know exactly what is going on before you plug it in.
You should be able to quickly (well, relatively quickly hehe) see your max voltage cell dropping and your min increasing.
Some balancers have start/stop trigger points instead of "always on"; its hard to get actual design specs so often the only way to figure it out is to test it.

check you voltages hourly and you should see a difference. If nothing is happening you may be in a balance inactive zone (the worst case cell difference is not enough to trigger the balance circuitry). When I was testing some balancers I have to use a resistor and purposely drain one cell to cause a big enough imbalance for them to kick in.

I did my first tests with the batteries disconnected fromthe charger, then I tested with the charger. Active balancers are NOT like the resistive ones that are just burning off energy. Actives should be moving energy from high cells to low cells so no need to have the charger connected AND you should not see all the cells only dropping in voltage; high cells should be dropping, AND low cells should be rising.
Hey 123! Thank YOU for taking the time to share this info. I have a basic Fluke multimeter and will do a 'before and after' chart on my iPhone notes and share that back here. Jerome
 
Thanks on that. Any special instructions? I was planning the same cells as the Daly leads; B- then each positive.
Yes, the leads go on the same as the BMS.

I've been doing something a little different, and maybe a little unorthodox. I took a hobby board (PC solder-able version of the standard breadboard) and wired in four separate 9-pin JST connectors. Then I put 9-PIN JST female connectors on the leads to my BMS, my Heltec capacitor-based balancer, my QNBBM-8S balancer, and my iSDT Q8 balance charger. Then I made one last cable with my balance lead ring terminals on one end, and a JST female on the other end. This lets me hot-plug any of the above in at once (up to 3). I can also unplug the balance leads on the hobby board all at once.

I did all this after trying to disconnect the leads from the QNBBM-8S from my battery, and the lead slipped out of my hand and briefly shorted to another cell stud. The QNBBM made some noise and there was a big spark, but fortunately it didn't harm the balancer or the cells.

Here's the pic of the hobby board and the plywood several of the items are mounted to. I should point out that - although it may not be obvious in the photo - there is a lexan shield over the hobby board to prevent me from accidentally shorting any of the cells. Also, I haven't mounted the Heltec balancer to the board yet.

IMG_20210618_090031532.jpg

IMG_20210618_090011341.jpg
 
Nice clean package and great idea! I see you have an Overkill BMS. I did too, but I mis-wired the sequence to the batteries
and absolutely fried it. That's why I have a Daly now! Overkill was out of the 48V versions.
 
Bonjour, je me lance dans la conception d'une batterie LiFePo4 de 200Ah. J'ai un BMS Daly 150A et j'ai également acheté un équilibreur actif : https://fr.aliexpress.com/item/4001...Detail6.0BottomMoreOtherSeller&scm=1007.13338 &scm_id=1007.13338.177756.0&scm-url=1007.13338.177756.0&pvid=9f29fbba-ca11-438d-b251-b57d9e0e36c8&_t=gps-id:pcDetailBottomMoreOtherSeller,scm-url:1007.133388.177756,0 tpp_buckets:668%230%23131923%230_668%238888%233325%2315_3338%230%23177756%230_3338%233142%239889 %231_668%232846%238107%231934_668%235811%2327188%2381_668%232717%237567%23911_668%231000022185%231000066059% 230_668%233422%2315392%2363
Ma question est la suivante: dois je connecter aux cellules les fils de l'équilibreur du BMS et les fils de l'équilibreur actif ou seulement les fils de l'équilibreur actif ? Merci pour votre aide.
 
You can connect both the bms and an active balancer, the active balancer will help balance the cells and the bms will protect the battery from over and under voltage at the cell level . The bms may protect the battery from low temperature if it has low temp. cutoff feature. The bms can protect the battery and your system in many ways and the active cell balancer will only help balance your cells.
 
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I use a Heltec Capacitor Active Balancer from amazon or aliexpress. Be careful when you use a capacitor active balancer , make sure you pre-charge the capacitors before you hook it up to your battery, I use a resistor on the negative lead to pre-charge the capacitors before I connect up the negative lead to the battery. With my first balancer I forgot to do that and I burned up one of the capacitor.
Sky when you used a resistor to pre-charge what was the value of the resistor? Also any body got an idea on what value resistor one should use on a 48 volt bank to precharge the inverter to prevent arcing and current inrush damage?
 

Anyone have experience with the HelTec SmartBMS? BMS with built-in active balancing and supports CANbus/RS485 communication. Seems like it would be good. I'm thinking of cancelling my order for Overkill 48V BMS and get these instead.

The website is hilariously terrible. But if the product is good and price is reasonable, who cares?


Category: SMART BMS SKU: 1026
Tags: 13-24S 200A Bluetooth Smart BMS with Active balance
Li-ion Lipo Lifepo4 LTO Smart BMS Lifepo4/LTO/Li-ion/Lipo
Support CAN / RS485 interface (optional) BMS


Edit: Oops I should have searched first. There's a dedicated thread for these:
https://diysolarforum.com/threads/heltec-jk-200a-smart-bms-with-2a-active-balance.17831/unread
 
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Yes, the leads go on the same as the BMS.

I've been doing something a little different, and maybe a little unorthodox. I took a hobby board (PC solder-able version of the standard breadboard) and wired in four separate 9-pin JST connectors. Then I put 9-PIN JST female connectors on the leads to my BMS, my Heltec capacitor-based balancer, my QNBBM-8S balancer, and my iSDT Q8 balance charger. Then I made one last cable with my balance lead ring terminals on one end, and a JST female on the other end. This lets me hot-plug any of the above in at once (up to 3). I can also unplug the balance leads on the hobby board all at once.

I did all this after trying to disconnect the leads from the QNBBM-8S from my battery, and the lead slipped out of my hand and briefly shorted to another cell stud. The QNBBM made some noise and there was a big spark, but fortunately it didn't harm the balancer or the cells.

Here's the pic of the hobby board and the plywood several of the items are mounted to. I should point out that - although it may not be obvious in the photo - there is a lexan shield over the hobby board to prevent me from accidentally shorting any of the cells. Also, I haven't mounted the Heltec balancer to the board yet.

View attachment 53312

View attachment 53314
On this note, doesn't that OKS bms do a pretty good job balancing? I've discovered I have 1 slacker in my 8s pack, but in a matter of, say 15 - 20 mins or so, it's brought up to the others. And I'm embarrassed to ask, but is it transferring from the high one to the low one? Or is it just burning off the high one? The app looks like it's transferring, but I've never really been sure. (I speak of the 8s 100A bms btw..the one in your pic)
 
The OKS BMS (and most BMS's) is only a passive balancer. That means that it only burns off the power in the highest cell. In the case of that particular BMS (and again, most) it is not capable of burning off much. Something like 200mA max. That isn't enough to get these big 200Ah+ cells balance quickly, but it might work over several charge / discharge cycles.
 
If I were to get an active balancer, I still use my BMS, but shut the BMS’s balancing off? I would also have to have an active balancer. Is there anything that changes on the wiring for the BMS if balancing is done by another device?
 
I believe that some people leave the BMS balancing turned on even though they have an active balancer. In my experimental hook-up, I've disabled the BMS balancing operation while testing the active balancers from QNBBM and Heltec, and that works fine. I think in my system I will leave the BMS balancing off, as I don't think it contributes much.

The wiring doesn't change to the BMS. The active balancer needs leads to the same points on your cells. There are multiple ways to wire the active balancer and BMS together, so that you only have one set of balance leads to the cells.
 
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