BMS Choices

shonalex

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Joined
Oct 6, 2017
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Alright, I think I have seen a bunch of BMS solutions, but nothing as cool as Batrium. I want something as cool, but hopefully not $600. I wonder if anyone knows any of the choices that are available. Is there and in the US so I don't have to wait so long for shipping? Thanks, let me know.


Should I just bite my lip and buy the batrium system? Looking for options is all.
 
Batrium shipping is under a week now. And no there isnot many to compete with batrium if you want to be able to expand the system easily bu just adding slaves.

RecBMS and Tiny BMS is 2 other that is rather nice systems but not the same range.
 
There are other options, just not easy plug and play. You can build your own much cheaper, if you know electronics, pcb, and coding. Gotta work for the inexpensive stuff ;)
 
Looking for a balance myself too, not willing to spend the $500 for the batrium just yet. Was reading owitte's powerwall and noticed he used this chinese 1s balancer. $20 each so looking at $140 for 7s and $280 for 14s. No monitoring or anything, but if on budget then may be a choice. Once my pack goes up then I'll see how much fuss it is to maintain balance. I may just get one of those cellmons and alarm if they start to deviate
 
280 vs 500.... The batrium you get 15x as much functionality. The 1s balancers are not even close to be worth it on a 14s or bigger system. The only thing they do is balance. But do you really know if they do balance? You still need to complement with the most important part and thats is the voltage monitoring and the 1s doesnt have that.

Is it really cheaper then? :)
 
Honestly, the whole setup with 14 longmons and the shunt will be $600. It's just pricey. Yes batrium is the best bang for the buck in the long run. But if there's something that can be had in the under $100 range that just balances out batteries would be ideal. If they could do something like that for the leafmons to allow us to just program them and use them independently to balance out packs (without monitoring) would be really nice. That way once monitoring is needed then that module can be purchased.
 
You can run the longmons and only top balance as the chinese versions does but its kind of useless.

Though im presenting a video tomorrow (If youtube plays well) about another cheap ass bms that is ok for those that just dont wanna pay all the bucks for the better ones.
 
Korishan said:
There are other options, just not easy plug and play. You can build your own much cheaper, if you know electronics, pcb, and coding. Gotta work for the inexpensive stuff ;)

Why don't we start a project out of that? I'm sure there are people on this forum willing to work on that...
I offer myself as a volunteer ...my knowledge in electronics are not great but i can help with the software development.
 
cmg_george there are plenty of ongoing projects allready. Several on Github as well :)
 
@daromer i was thinking more on the hardware part like designing a pcb. software for the hardware part and so... I look some time ago after a project like that but i was not impressed with what i found... maybe i didn't found the best options (i will look again).
Personally i like the @jesusangel approach (with ESP) http://secondlifestorage.com/t-JAP-...or-Jesus-Angel-s-Powerwall?pid=18188#pid18188 his idea can be build even cheaper (with an ESP12)
 
I plan on building my own based off the TI BQ76940 www.ti.com/product/bq76940

But it will be awhile before I start working on it. I'm still learning all the stuff that I need to know before hand
 
As i mention my electronics knowledge/skills are not that good... but if i go this right that will read each cell voltage and send that information via i2C? Looks interesting... add an ESP32 and you have the monitoring hardware...
Looking forward for your BMS
 
It'll be nice to come up with something! The one thing I noticed with the chinese 1S balancer is that it seems to take the high voltage cells and dump into the low voltage cells. I'm not sure how they are doing this, possibly with a supercap as in intermediate storage. But that's a better design in a way than the batrium where I think it's just doing a load resistor dump. My idea initially was to keep the cost low by utulizing only a few balancers and attaching to the high and low cells through arduino somehow.
 
I didn't think about using a super-cap. That's an interesting idea. I will have to keep that on note. But we'll see how things progress as I put it all together. Again, it's a few months away before I get into it. I gotta start tinkering with other arduino stuff to get more familiar with it.
 
not2bme they use biderectional dc/dc on an isolated bus. Where all cells send their energy. The one with lower will take and the one with higher will give.

And then i looked at another alternative the other day:
 
daromer said:
not2bme they use biderectional dc/dc on an isolated bus. Where all cells send their energy. The one with lower will take and the one with higher will give.


Wow good review on the 1s balancer. That got me to look more into active balancers instead of a whole bms. It's more of a dumbed down version that just does the basics, and that active balancing (taking cells from high to low) is a better alternative than passive balancing (like a resistive load). This may also be better for smaller packs so there's less power loss since passive balancing is just dumping the load. Also active means very little heat generated since it's transferring the load (basically charging another cell, well i hope that's the case since it's claiming over 90% efficiency at 1A).

I found two that looks ideal. High active current transfer > 2amps.

8s balancer (scalable to 24s) - Capable of 4 amps active transfer, with serial connection for maybe future arduino BMS?

16s balancer - Has display, and limited bms to control over voltage (through small limited passive load) and a regular active balancer at around 2-3 amps

I only have a 7s so I may try out the 8s balancer, but both may be ideal starter balancers for under $100.
 
not2bme generally tha lost energy due to balancing is not a problem. On such systems you try to only balance in the top when they are full and you have excess or you are charging fast.
Doing so the lost energy is minimal and does not affect the overall functionality.

Meanwhile the active is on always in most cases "loosing" energy by transfering it back and forth.

For me Active balancing is for systems where you have battery banks with banks that are far apart in terms of capacity. Lets say you got 20Ah 20Ah 10Ah. Then an active will help you out so you potentially can use 15Ah instead of 10Ah in total. This a passive cant.
For a battery bank that have same amount of capacity in the packs you need to balance very very little per week and that should not be an issue. If it is the packs have a greater issue!

Note that active balancing tend to balance back and forth. So when you drain them they will balance to the cell with lower resistance. And when they are charged back up again they balance it back again. This is not really needed. Unfortunately on all the cheap ones out there this is what will happen and in long run you loose more on the active system


So my point is that you dont save energy on the cheap active balancers because they balance without a thought behind it. They tend to waste more energy than gained. And if you get one make sure you get one that can show how much energy have been transfered back and forth and you see what I talk about :D
 
In other words active balancing can be inefficient iif done incorrectly. so if there was some combination with some arduino voltage monitoring and some 8 relay boards to turn on when the deviation between the cells are withing certain set limits so active balancing isn't active 100% of the time then it will be a cost effective solution. Or is this still a foolish idea?
 
not necessarily foolish, just interesting ;)
 
Phew.. I was thinking that maybe it's just futile to even think about anything other than Batrium
 
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