# Help picking a BMS



## Kingpen (Apr 18, 2017)

hello all- I'm kind of new to this and I feel like i'm missing something. I'm building a pack of 72 cells in series and I wanted to get something to balance the cells and let me monitor the individual voltages. The only thing I've come across are the Orion and Lithiumate - both of which are $2000+/- solutions that seem to be the Cadillac's of BMS systems. Is there anything more affordable? I really only need balancing and something to see the voltages.


----------



## madderscience (Jun 28, 2008)

AFAIK your options are those you mentioned and the Manzanita Micro BMS (which is also going to end up at a similar price). With 72 cells the incremental price per cell is $30 which certainly adds to the overall cost, but it is worth it to protect your pack. Some people go without BMS but they instead have to obsess over manual balancing and monitoring of the pack to avoid damage. It is possible to DIY a BMS (I've done it) but it is a lot of work.

a dirt simple thing you could do for monitoring which is better than nothing is put a 12V digital panel voltage display (powered by the voltage it samples) on each bank of 4 cells. You can buy these for a few dollars each on ebay. Unless you both a very high and a very low cell in one bank you will be able to see the voltage deviation and act on it.

For simple balancing, you can make a post-zombie-apocalypse LiFePO4 balancer circuit from 5 1n4001 diodes and a 1a minature fuse in series (total forward voltage drop about 3.5v) which will drag down higher voltage cells faster than ones at a lower voltage. This style of balancer is leaky (~10ma at 3.4v IIRC) vs the microcontroller powered ones all the major BMSs use which probably draw <1ma when "off", but if you are going to be using and charging the pack regularly it should be a nonissue for large format cells. (10ma would take 400 days to drain a 100ah cell, but in reality by the time the cell hits 3.0v the diode based balancer would be almost completely "off" so they could not totally drain the cells)

You would still want to check the voltmeters near the top of their charge often and use a fairly slow charger with a fairly conservative HVC. 

I have this exact described setup which has been running perfectly 3-4 years now powering my tool shed (24v, 60ah pack) and charged off a solar array. 

Good luck.


----------



## Duncan (Dec 8, 2008)

You need to think about what a BMS does

If you start with a balanced pack then I see almost nobody who has had any drift - however I have had cells fail 

So I believe that you need
(1) Balanced pack
(2) Some way of detecting a failed cell

I'm using a "Lee Hart - Batt Bridge 
http://www.evdl.org/pages/battbridge.html
This will show if one side of your pack is behaving differently than the other - or you could split the pack into smaller units

Otherwise be careful about going to the extremes of full charge and full discharge


----------



## Moltenmetal (Mar 20, 2014)

http://elithion.com/lithiumate_pro_controllers.php

Not an endorsement- I've never used it, but it seems more economical than other options now that the miniBMS is no longer sold.

If you're using Li ion batteries, you either need a BMS or YOU will be the BMS. And you'll get lazy sometime. Buying a BMS is cheap insurance.


----------



## Yabert (Feb 7, 2010)

Zeva also sell nice low cost BMS, but don't show the per cell voltage.
http://www.zeva.com.au/


----------



## Kingpen (Apr 18, 2017)

madderscience said:


> AFAIK your options are those you mentioned and the Manzanita Micro BMS (which is also going to end up at a similar price). With 72 cells the incremental price per cell is $30 which certainly adds to the overall cost, but it is worth it to protect your pack. Some people go without BMS but they instead have to obsess over manual balancing and monitoring of the pack to avoid damage. It is possible to DIY a BMS (I've done it) but it is a lot of work.
> 
> a dirt simple thing you could do for monitoring which is better than nothing is put a 12V digital panel voltage display (powered by the voltage it samples) on each bank of 4 cells. You can buy these for a few dollars each on ebay. Unless you both a very high and a very low cell in one bank you will be able to see the voltage deviation and act on it.
> 
> ...


Thanks, I actually did plan on doing something similar to this. I'm just going to use some simple volt meters to watch/compare voltages across several cells in series. It would have been nice to be able to see individual cells at a glance but that seems to be to expensive for what I'm doing. Charging was an issue at first but I think i sorted that out and it involves using a parallel board with one of my high powered hobby chargers. Should be able to charge and balance all of them at once.


----------



## Kingpen (Apr 18, 2017)

Yabert said:


> Zeva also sell nice low cost BMS, but don't show the per cell voltage.
> http://www.zeva.com.au/


Those actually do look to be one of the cheapest but is still very expensive once I buy all of the 12s boards. Looks like they 3d print the cases too, kind of cool.


----------



## Kingpen (Apr 18, 2017)

Moltenmetal said:


> http://elithion.com/lithiumate_pro_controllers.php
> 
> Not an endorsement- I've never used it, but it seems more economical than other options now that the miniBMS is no longer sold.
> 
> If you're using Li ion batteries, you either need a BMS or YOU will be the BMS. And you'll get lazy sometime. Buying a BMS is cheap insurance.


These guys actually came out to be the most expensive of all.


----------



## dimitri (May 16, 2008)

Thunderstruck will be offering their new BMS soon
http://www.thunderstruck-ev.com/bms/

Call them and ask for "early adopter" discount 

Their system scales nicely to 72 cells, in multiples of 12 per LTC chip.

EVen better if you get their charger too, it integrates with BMS natively over CANBUS


----------



## dr.ona (Dec 27, 2016)

dimitri said:


> Thunderstruck will be offering their new BMS soon
> http://www.thunderstruck-ev.com/bms/
> 
> Call them and ask for "early adopter" discount
> ...


Any idea of how much these will cost?


----------



## Ampster (Oct 6, 2012)

dr.ona said:


> Any idea of how much these will cost?


I am interested also. I have their Charger for my stationary pack. That would be a nice addition to that system.


----------



## dimitri (May 16, 2008)

I'm not associated with TSM and not privy to their release plans or pricing. If you are interested, pick up a phone and call the number listed on their Web site...


----------



## Ampster (Oct 6, 2012)

dr.ona said:


> Any idea of how much these will cost?


I called Thunderstruck and the 24 cell module is going to be priced at $440 and the guy on the phone said they are available now. The website has the manual for download but I couldn't find any click to order. I am a few months away from pulling that trigger anyway.


----------



## PeterS (Jul 30, 2013)

I´m not saying you should buy one, as you already disgarded them in the first post as beeing too expensive.

But I was in the same seat as you a month ago, needing a BMS for my 86S pack for my DIY electric car.

Having spent more than 25k$ on the conversion itself, I decided that an additional 2k$ for a Orion BMS to protect my investment of time and money wasn´t that big of a deal after all.

It hurt some in the beginning, because it is a lot of money, but after installing it and learning all of its features, I cant say that it was expensive. A lot of money, but not expensive...

Using the Torque app for Andriod, you can customize a display (or several) to your liking.

The Orion keeps the cells in balance, have numerous outputs that can be configured to do just about anything you want, controlling chargers, motor controllers over CAN. It monitors the internal resistance of the cells, state of charge, you have bus bar resistance compensation, temperature compensation and much much more.

That´s my five cents.

And of course I am in no way associated with Orion, it´s just my honest opinion.


----------



## Moltenmetal (Mar 20, 2014)

I definitely swapped the Elithion and Zeva offerings in my mind. Sorry for misdirecting you.

To my mind, all you need is an alarm trip module on each cell. Balancing isn't something you really need in my opinion. But you do need an alarm trip module on each cell...I found that out.


----------



## Ampster (Oct 6, 2012)

Moltenmetal said:


> .......
> To my mind, all you need is an alarm trip module on each cell. Balancing isn't something you really need in my opinion....


I agree. Some offerings allow you to switch off the balancing function. I run a reconfigured Leaf pack with 6 modules in parallel. On my Orion Jr I often switch off the balancing function. If I find a need to balance I also have an extended low Amperage finishing taper that I run when balancing.


Sent from my SM-N910T using Tapatalk


----------

