BMS comparison

[CB-OTB]

Is there a comparison table of the more popular BMS options?

I’m building a 12v, 280Ah pack and would like to have the following capabilities, in addition to the safety functions.

- monitor battery SOC from phone.
- put multiple packs in parallel, at least up to four
- either high current capability (at least 250A cont.) or the ability to switch external devices
- for future upgrades I would like to be able to connect to a bictron charger/inverter.

it rarely gets below freezing here so I can monitor low charge temperature manually, so that capability is not critical. Although it is desired.

 

[Shinebox]

Are you looking at an external Bms? Or are you interested in a drop in?

 

[CB-OTB]

Are you looking at an external Bms? Or are you interested in a drop in?

I currently have no resistance to either one.

 

[svsagres]

In my case, I went with the REC Active BMS for the 2p4s 460AHr battery I'm installing in my boat. I did this mostly because a) it has an integrated 2A battery balancer, and b) it will tightly integrate with my Victron setup (inverter/charger and solar), as well as the wakespeed alternator regulator for engine charging.

Given that it's contactor based BMS, the current it can deal with is only limited by the size of the contactors. In my case, the high side bus (including the inverter/charger) is on a 500A contactor, but I've fused it down to 350A. My DC system is running off of a 65A Victron BatteryProtect.

Yeah, it doesn't do the phone app thing natively, but imho, more importantly it shows up properly, out of the box, in Victron's setup. That reports out to the internet, and I can monitor my boat's power system (and other things, like fuel/water/temperature/bilge levels) remotely over the internet.

The other downside is that the are definitely on the more expensive side, especially once you include the cost of the contactors, class T fuse, and other related support components. But hey, I'm an instrumentation geek, and this tickles that itch.

 

[Shinebox]

Rereading your needs, I think you’re looking for an external BMS. I have the same setup as SVagres. In addition the the Victron integration, I have a wakespeed regulator as well that is controlled by the REC bms. As for a chart that compares different BMSs, TaoBMS has one posted on their site:

BMS comparison chart – TAO Performance

www.taoperf.com

They’re obviously trying to sell their own product, so take it with a grain of salt, but it does list several well known options and breaks out their capabilities relative to one another.

 

[CB-OTB]

That sounds like a good option, but good lord, you guys went straight for the kill shot in terms of expense.

I would place higher priority on Bluetooth comms, at the moment, since I do not currently have victron equipment. I plan to down the road..

 

[Shinebox]

Well, if your looking for integration with Victron, then you want a bms with CANBus, and any BMS with CANBus is going to cost more. Lots and lots of BMSs have Bluetooth, even some of the cheapest ones with spotty track records like Daly. Overkill Solar sells a solid bms From Xiaoxiang that has Bluetooth, but no CANbus

 

[svsagres]

Well, if your looking for integration with Victron, then you want a bms with CANBus, and any BMS with CANBus is going to cost more. Lots and lots of BMSs have Bluetooth, even some of the cheapest ones with spotty track records like Daly. Overkill Solar sells a solid bms From Xiaoxiang that has Bluetooth, but no CANbus

There is a third party driver for the Victron GX line that will work with other BMSs via serial. But it means more hacking of the unit than just having it work out of the box.

The other thing to remember is that a lot of BMSs aren't all that accurate when it comes to computing their state of charge. I would expect that most of this inaccuracy is due to the various BMSs not having a proper shunt for measuring current in/out of the battery.

 

[gtstricky]

To answer your question... no, there is not a good comparison chart (that I have found).

I use a Daly and I am always looking for something better (but reasonably priced). There are not a lot of consumer friendly BMSs. Most seem to be geared towards battery manufacturers and are made to their specs. The build your own battery group seems to be a niche market and as you have found, those that are willing to supply it with nice BMSs charge for their work and the lack of a large market.

While I would like more bells and whistles, having working temp and voltage cutoffs is the main reason for my BMS and Daly does that for me.

 

[CB-OTB]

I am leaning towards the REC BMS.

Is the pre charge delay module recommended, or is it not necessary? I would’ve assumed that equipment from victron would address any issues with in-rush currents, but maybe this isn’t the case.

My first iteration of this will be for the battery to power only DC loads (bow-thruster, windlass, lights, water pumps, fridge, freezer) and will be charged from either DC-DC converters or a plug-in 120 Vac to 12 Vdc charger.

Later I will add more capacity and an inverter to power AC loads

 

[Shinebox]

I am leaning towards the REC BMS.

Is the pre charge delay module recommended, or is it not necessary? I would’ve assumed that equipment from victron would address any issues with in-rush currents, but maybe this isn’t the case.

My first iteration of this will be for the battery to power only DC loads (bow-thruster, windlass, lights, water pumps, fridge, freezer) and will be charged from either DC-DC converters or a plug-in 120 Vac to 12 Vdc charger.

Later I will add more capacity and an inverter to power AC loads

I have one. After repeated use, the inrush current will wear out the inverter. I’m also using a victron multi plus inverter/charger

 

[svsagres]

I am leaning towards the REC BMS.

Is the pre charge delay module recommended, or is it not necessary? I would’ve assumed that equipment from victron would address any issues with in-rush currents, but maybe this isn’t the case.

My first iteration of this will be for the battery to power only DC loads (bow-thruster, windlass, lights, water pumps, fridge, freezer) and will be charged from either DC-DC converters or a plug-in 120 Vac to 12 Vdc charger.

Later I will add more capacity and an inverter to power AC loads

I figured that for $70, why not? But I'm immediately starting with a Multiplus inverter/charger, so I already have the large capacitors to deal with. The reality is that if you design your system properly (all your charge sources controlled by the BMS) you'll probably never trip out your high side contactor, unless you shut down your power system deliberately. Our new paradigm is going to be leaving the DC system on at pretty much all times.

 

[CB-OTB]

The only response to the why not question is that I started out with a very complicated wish list and it was getting overwhelming. So I switched gears and moved towards trying to implement a very basic system and add to it, with the idea that whatever I purchase needs to accommodate the future expansion. Which is a benefit of the Rec BMS.

with the idea of leaving things “on”. Is there an issue with a charger plugged into my house bank and leaving the dc loads on all of the time? For example, I can power my refrigerator from 120v or 12v. Why not just leave it set to 12v and let the batteries/charger power it all of the time. is this detrimental to the batteries?

 

[svsagres]

The only response to the why not question is that I started out with a very complicated wish list and it was getting overwhelming. So I switched gears and moved towards trying to implement a very basic system and add to it, with the idea that whatever I purchase needs to accommodate the future expansion. Which is a benefit of the Rec BMS.

with the idea of leaving things “on”. Is there an issue with a charger plugged into my house bank and leaving the dc loads on all of the time? For example, I can power my refrigerator from 120v or 12v. Why not just leave it set to 12v and let the batteries/charger power it all of the time. is this detrimental to the batteries?

This is where things like Victron's DVCC come into play. On my system, the DC loads have their own smart shunt (separate from the battery shunt), so when we approach 100% on the battery, the BMS will drop its requested power to say 2A. At the same time, the DC loads on my boat are drawing say 7A (my refrigerator is running). With the way I have it setup, the power system should then deliver 9A into the positive bus. 2A of that will go into the battery, the other 7A into the DC loads.

I'm still just in the early stages of building the system out, but I'm definitely a system integration geek, so putting this all together is a heck of a lot of fun to me.

 

[CB-OTB]

gotcha. I got to go do some honey-do items, but I‘m probably going to snoop through your old posts later tonight And see what I can learn. My cells are also arriving today so I’m going to start balance charging them.

 

[mikefitz]

Try this company for a bms,

Home Page - LLT POWER ELECTRONIC

Mike

 

[wholybee]

I'll offer some less popular opinions. Consider what you *really* need. Many BMSs are full of feature bloat and needless complexity. The job of a BMS is to protect the battery in case other devices (alternator regulators, chargers, inverters) etc fail somehow. In a well designed system, the BMS should not need to do anything. A wakespeed regulator and victron chargers are perfectly capable of properly charging a Lithium battery without communication or help from a BMS.
I'm also a fan of FETs over relays. When properly sized and designed, they are more reliable and faster than a relay. Equipment I work on switched from relays to FETs decades ago, and my job got a lot easier. For huge loads a relay might be better, but for less than 250A or so, I would use FETs.
With that in mind, you said you want to parallel multiple packs. Two packs each with a 100A FET BMS would support 200A give or take, plenty to support your 150A expected load.
Battery SOC is better determined by a victron BMV-712 than a BMS. However Bluetooth on the BMS is useful to check protection status and balance status.
One feature of the overpriced high end BMSs is the ability to have a visual or audible alarm as a warning before a disconnect. This feature is required to comply with Abyc TE-13. But it's a crazy amount of money to spend to get just that one feature. I really hope it's added to some lower cost BMSs.
My own battery is a 300Ah battery with 12 100Ah CALB cells in 3p4s configuration and an overkill BMS. I've sailed about 4000 Ocean miles with it so far and it's something I've basically forgotten about, it's been trouble free and maintenance free and I only glance at my victron meter now and then to check SOC. Rarely, I check the BMS to see there has still never been a disconnect and the battery is still in perfect balance. AFAIK, that's the way it should be. It was a pita maintaining FLA batteries, why would I add more gizmos to subject myself to that if Lithium doesn't need it?
Anyway, I know more people would prefer contactors and the long list of features of the Rec BMS, but it's good to hear both opinions.

 

[Johnson]

I ended up going for the SBMS0, open source hard and software, but Dacian has problems sourcing the electronic parts due to shortages so it might take a while to get your hands on one.

 

[CB-OTB]

I figured that for $70, why not? But I'm immediately starting with a Multiplus inverter/charger, so I already have the large capacitors to deal with. The reality is that if you design your system properly (all your charge sources controlled by the BMS) you'll probably never trip out your high side contactor, unless you shut down your power system deliberately. Our new paradigm is going to be leaving the DC system on at pretty much all times.

What all is needed to run a Rec BMS as a standalone system, ie no victron etc integration.


I need the following:
- bms
- contactor
- wiring harness
- touchscreen or wireless module
- softstart module (optional)

 

[wholybee]

What all is needed to run a Rec BMS as a standalone system, ie no victron etc integration.


I need the following:
- bms
- contactor
- wiring harness
- touchscreen or wireless module
- softstart module (optional)

You also need a shunt, fuse and holder. And 2 contractors, not just one.

When I priced it all before deciding against it the price for a REC BMS and what's needed to go with it was about $1000.