Anyone know of a 'dumb' BMS ?

Announcement - Help us fight the BOTS! Please report all spam including stuff in your inbox!

ng.sa

Member
Joined
Apr 4, 2017
Messages
88
The current BMS's are way to 'smart' and expensive.

What we do not want firstly

- An app. to connect to the BMS
- these apps are g8 to debug a pack, but way to complex for end users who just want to plug and play and walk away
- Multi lingual ( English only )
- LED screen
- WiFi connectivity
- Bluetooth connectivity

What our basic requirements are

- 29.xV and below 7s2p 1865 and 2170 cell monitoring
- Store output log to a FAT32 filesystem on a removable media
- Monitor cycles
- Monitor temperature
- Programmatically set high and low water marks

Obviously would prefer to COtS ( Common Off the Shelf ) but, I have designed and built hardware / software systems for dod.gov.au and private ent. so I understand how much time and effort to start from scratch.

One possibility would be for a current manufacturer to de-spec. a smart BMS, I have seen this approach with white goods that use remote controls, you only allow a few features of a unit to be accessed via the remote, but the chip set is the same in all of the units. We call this badge engineering, all units internally are exactly the same you re-badge and send a different remote in the packaging.

The only novel part of this projects is the writing to the media and the management of the .bms files.

We already have a soft. sys. that sends email due to monitoring alerts to NOC ( Network Oper. Centre ) so we just need to be able to read the .BMS files to gen. an email when the charge ( high water ) dis-charge ( low water ) marks have been meet.
 

Korishan

Moderator
Joined
Jan 7, 2017
Messages
6,527
There's LOTS of ebay/banggood/aliexpress dumb bms's out there. They are the ones that have only the wires needed for monitoring and maybe some resistors for balancing plus the 2 main power leads. They sell for a few $US to <$20USD.

The added expense of dropping a BT or wifi connection to the device isn't really that expensive. Those bms units most likely use, or a variant of, the esp8266 (like the esp01), which are almost dirt cheap. Also, the "smart" bms units can still be had for <$20USD.


If you do plan on building a unit from scratch, I would recommend going with the ESP modules anyways, just because they are cheap, easy to program, and highly versatile for what they can do. The ESP32 has enough pins for monitor various analog connections (not requiring i2c coms for example) and still would allow for wifi/bt connectivity if you so choose to do so. If going to have an sd card onboard, no need to "program" the esp with wifi credentials, just have a file on the sd card that's for the wifi settings that would include the ssid/pw/etc (or in a generic settings.ini file with everything else) so that the user can just open it up on the computer in notepad. No fumbling with the wifi ap on first boot up.

If you go down the road of building your own bms system that is "smarter than stupid, but not as smart as a smart unit", please keep us posted. It'll be interesting to see where you go with the project, plus you'd get a lot of help along the way.
 

Roland W

Member
Joined
Oct 9, 2017
Messages
136
What our basic requirements are

- 29.xV and below 7s2p 1865 and 2170 cell monitoring
- Store output log to a FAT32 filesystem on a removable media
- Monitor cycles
- Monitor temperature
- Programmatically set high and low water marks

You can split those tasks, use a very dumb, inexpensive hardware BMS to take care of the cells and limits, and the rest you just let a MC based Battery Monitor do.
On my systems I have exactly that implemented with inexpensive DIY builds. Voltages, Temperature, SD-Card...
 

ng.sa

Member
Joined
Apr 4, 2017
Messages
88
G'Day Guys

Thanks for the heads up :)

If I had to pick one mandatory it is the writing to the SD Card ( SDC ) so it can be removed from the pack and then analysed in a PC using our client.

So the power pack could be in a 4x4 which only has cell phone access and send a email to the NOC

But obviously as the .bms file is written to the SDC as text any desktop app., script etc. could anal. its contents, so do not need our system.

I found this device


It can write to a SDC

Do you know of an BMS that can do this logging to a SDC ?
 

Korishan

Moderator
Joined
Jan 7, 2017
Messages
6,527
yeah, the diyBMS by Stuart Pittaway.
His even smart enough that if a pack gets separated from the others (the bms that is), it'll still continue to function independently to keep that pack safe. Then when it's reconnected, it'll report all the data back to the master.
Granted, it's not the "cheapest" solution, but it is by far one of the best inexpensive solutions. And he's making it better with each revision. He's up to V4.22 now.
Just for example, for a 14s bms solution, it would cost about $80USD for the PCB manufacturing, components and the PNP service, plus shipping. Which, all in all, is pretty good deal considering what it can do.
 

glyndwr1998

New member
Joined
Sep 8, 2018
Messages
29
Hi all, just joining in here,

does anyone offer a build service for the stuart pittway bms?
I`d be looking for a 16s set up and another one at a 13s set up.

Thanks
 

glyndwr1998

New member
Joined
Sep 8, 2018
Messages
29
Thanks floydR, much appreciated.
Have sent a request to the facebook page and looking at the avenues to buy a system for each of my batteries.
On a previous battery i used the ZEVA bms, and to be honest it has worked flwalessly now for nearly 2 years on a nissan leaf battery set up in a 3p7s configuration making a 58v battery.
The one issue with the ZEVA bms is the resolution for pack voltage control, it can only be adjusted in whole volts, ie 56v, 57v etc.... ideally with the leaf cells a setting of 57.5v is perfect.
 

Korishan

Moderator
Joined
Jan 7, 2017
Messages
6,527
Hi all, just joining in here,

does anyone offer a build service for the stuart pittway bms?
I`d be looking for a 16s set up and another one at a 13s set up.

Thanks
Why? JLCPCB will put the components on the board for you. That's what PNP means.
There are a few components that you'll need to do yourself, tho, to be honest, tho. Nothing too small, really, just a few header pins, possibly one of the IC's if they don't have it in stock (it's a short supply item, the ATTINY chip)

You would need to program them yourself. You may have to do that anyways for one you buy second hand in case they don't have the latest firmware.

Also by getting them from JLCPCB, you'll probably get them delivered to your door faster than someone else sending them. But that is dependent on their location.
 

glyndwr1998

New member
Joined
Sep 8, 2018
Messages
29
Ok,

Ive looked into the Stuart Pittaway diybms, and i am impressed with it.
Ive looked at getting the pcb manufactured via the links, at moment there a few shortages of parts.
Plus, it looks like the controller needs to fully manually assembled, something that may be out of my skillset, plus not having the right equipment, like magnifyer aid, high temp controllable heat gun, prof solder iron etc for the surface mount parts, thro hole i`m ok with.

Anyone know of any complete controllers for sale, or want to offer their skills for an assembly fee to make up 36 slaves and 2 masters, plus program / flsash them.

Thanks
Anthony.
 

Korishan

Moderator
Joined
Jan 7, 2017
Messages
6,527
You can solder smt components with a standard iron. You just need a fine tip.

Soldering the controller IC to the board is actually relatively easy as the pads are spaced apart. If you can solder header pins to a board, you should be able to solder these.
You don't need "professional" tools to do the job. Though, having them does make it easier. I don't have any professional tools and I was able to solder 0603 components. That's 6mm long by 3mm wide. Solder paste helps a lot, but you can do it with regular solder wire, too.
Have a look at this youtuber (https://www.youtube.com/c/Sdgelectronics) and search his videos for smt or smd soldering, also soldering tips (both as in tips for the iron and tips/hints). He does a really good job of explaining things.
 

Korishan

Moderator
Joined
Jan 7, 2017
Messages
6,527
0603 (imperial) is closer to 1.6mm x 0.8mm

And having good pointy tweezers helps a lot!
Ah yeah, that's right. I forgot those numbers were imperial tenths :p Thanks for the correction. So it's even smaller than I thought lol
 

cak

Member
Joined
Mar 14, 2021
Messages
54
I am USA based and planning on making a big diyBMS mostly assembled PCB modules and controllers but am waiting for some IC chips to be in stock. It is not much extra to get lots of boards so I figure I will share around the extra ones I don't need.
 
Top