Best BMS?? for DIY 560AH 12V Battery - VAN BUILD

[timmypt]

Hi all!

I'm a beginner trying to build a DIY 560 AH 12V battery (2P4S is my current thought) using 8x280AH cells for $1111 USD shipped to BC, Canada, from Alex at Basengroup. I spoke to Amy (who is well known on this forum) as well but it would cost $1296 USD through her and I've spoken to a few people who have recommended Alex as a reputable seller.

I'm struggling to decide which BMS to go with and would appreciate any advice! I've purchased a 3000w 12v inverter and will be using 4/0 cables, maximum load will be rarely used, but around 300 amps.

1. Daly LFP 4S 12V 400A Smart BMS with BT+ Module
- Not as keen on this one anymore due to it having internal mosfets and I've read that they are less reliable at high amperages.
- Some confusion as to whether or not this device really has low temperature protection, although Alex assured me it does have it...

2. Chargery BMS8T 600A with DCC-600HB relay
- I'm leaning towards this unit, but my main concern is that in Will's youtube the relay gets really hot. I've read that some people use a separate relay or "contactor" to keep the circuit closed if there is a fault. Can anyone share experience or resources about this and what would be the best way to set this up to have a reliable system?

3. Electrodacus Sbms0
- My main reason for staying away from the electrodacus is that it doesn't seem to be compatible with some of the components I've already purchased (Renogy MPPT)

Any help or advice is greatly appreciated!

 

[Haugen]

Hi all!

I'm a beginner trying to build a DIY 560 AH 12V battery (2P4S is my current thought) using 8x280AH cells

I'm struggling to decide which BMS to go with and would appreciate any advice! I've purchased a 3000w 12v inverter and will be using 4/0 cables, maximum load will be rarely used, but around 300 amps.

1. Daly LFP 4S 12V 400A Smart BMS with BT+ Module
- Not as keen on this one anymore due to it having internal mosfets and I've read that they are less reliable at high amperages.
- Some confusion as to whether or not this device really has low temperature protection, although Alex assured me it does have it...

2. Chargery BMS8T 600A with DCC-600HB relay
- I'm leaning towards this unit, but my main concern is that in Will's youtube the relay gets really hot. I've read that some people use a separate relay or "contactor" to keep the circuit closed if there is a fault. Can anyone share experience or resources about this and what would be the best way to set this up to have a reliable system?

3. Electrodacus Sbms0
- My main reason for staying away from the electrodacus is that it doesn't seem to be compatible with some of the components I've already purchased (Renogy MPPT)

Any help or advice is greatly appreciated!

My experience so far has been that the rating of the BMS I find that the wire size is usually a little small, (they get warm) but the electronics seem to handle the rated current without issue.
If you only want a system that will provide a maximum of 300A on rare occasions, then I would only be looking for a 300-400A BMS.
In your situation, I would probably go with two 200-250A BMSs and build 2 X 4S packs in parallel. This way, if a BMS fails, you have a spare you can wire up 2P4S and keep going on one until you can get a replacement.

I, personally, don't like the concept of the Chargery BMS. When I first started learning, it seemed attractive. It looks like a mature, finished product compared to some others. I soon recognized that I didn't want to power a screen that I wasn't going to look at all that often and the external relays meant more stuff to buy which turns into more money, more connections, and more time than a FET based solution.
I have a Heltec 200A I'll be using in my home solar setup with 280Ah cells. It's 16S, so a little different setup. Im not recommending this because I haven't received my cells to test it out. I'm just saying that there are more types out there that do a good job and are trusted.

Spend some time reading the Energy Storage forums and check out some of the mentioned products in Alibaba or AliExpress.

 

[Bob B]

What are you going to be using the battery for?

 

[timmypt]

My experience so far has been that the rating of the BMS I find that the wire size is usually a little small, (they get warm) but the electronics seem to handle the rated current without issue.
If you only want a system that will provide a maximum of 300A on rare occasions, then I would only be looking for a 300-400A BMS.
In your situation, I would probably go with two 200-250A BMSs and build 2 X 4S packs in parallel. This way, if a BMS fails, you have a spare you can wire up 2P4S and keep going on one until you can get a replacement.

I, personally, don't like the concept of the Chargery BMS. When I first started learning, it seemed attractive. It looks like a mature, finished product compared to some others. I soon recognized that I didn't want to power a screen that I wasn't going to look at all that often and the external relays meant more stuff to buy which turns into more money, more connections, and more time than a FET based solution.
I have a Heltec 200A I'll be using in my home solar setup with 280Ah cells. It's 16S, so a little different setup. Im not recommending this because I haven't received my cells to test it out. I'm just saying that there are more types out there that do a good job and are trusted.

Thanks for the info! I do like the idea of having 2 completely separate packs in parallel, each using ~250A BMSs. Other than the DALY smart BMS I haven't been able to find any that are around that capacity. If the overkill BMS was rated for that I would go that route.

That's true about the cost of the Chargery. It certainly seems higher than most others when you add in all the extras that you end up needing. Reading and watching videos constantly, so hopefully I'll find the right fit for my system, but I appreciate your input.

 

[timmypt]

What are you going to be using the battery for?

The battery will be in a 2020 Ford Transit Campervan conversion. 500W solar on roof rack and Sterling 60A DC to DC charger (250A alternator on the 2020 transit). There will be a variety of 12v loads (lights, maxxair fan, water pumps, etc), as well as 120V AC loads through 3000W 12v inverter (AC outlets, 1800w induction cooktop, 1440w hot water tank, etc, though not all at the same time).

 

[Bob B]

It certainly gets complicated when there are several different charge sources and a mix of DC loads and AC loads.

I decided I wanted to be able to control the DC loads independently of the inverter .... and didn't want the BMS itself in the path of the main current flow .... So, I went with the Chargery.
I have found a way to adjust the shut down voltage in my inverter and plan to adjust it to shut off at a higher voltage level than the DC loads which I will disconnect with the Chargery and probably have a separate low voltage disconnect for redundancy.

The way I look at it, systems like the Chargery and the Electrodacus are better when you want more complex control. If you want simple .... just shut down everything at the same time .... BMS like the Daly would probably be the way to go.
I chose to build a 2P4S pack an only utilize one Chargery BMS .... I also plan to use all low current SSR's. The redundant shut-off for the inverter will be a low current SSR in series with the power switch ... my DC loads aren't very high current.
Controlling the charge side High voltage disconnect can also be done with separate relays or SSR's.
There are also smart shunts that can take action based on SOC.

There are "BMS police" who will say you don't want to have the BMS be the primary control for charge or load. I personally don't think that matters at all as long as there is redundancy in the protections.

 

[Haugen]

I was just reading through this thread:

looking for a good quality bms for my large 14s system

I have some large BMW batteries They range in 3s, 4s, and 5s packs, i have them configured so that i have 14s groups. i can make up to 6 strings, but for now i will start off with 2 and see how much more I can add in the future. But for now I am searching for a good BMS, one with active top...

diysolarforum.com

It seems there is some merit to the BMS being the last resort. The SolArk apparently doesn't like to have the batteries disconnected by another device.
You can get some nasty power surges that way.

 

[Bob B]

I don't intend to disconnect the batteries from any device .... I intend to disable the source power or turn off devices.

 

[timmypt]

It certainly gets complicated when there are several different charge sources and a mix of DC loads and AC loads.

I decided I wanted to be able to control the DC loads independently of the inverter .... and didn't want the BMS itself in the path of the main current flow .... So, I went with the Chargery.
I have found a way to adjust the shut down voltage in my inverter and plan to adjust it to shut off at a higher voltage level than the DC loads which I will disconnect with the Chargery and probably have a separate low voltage disconnect for redundancy.

The way I look at it, systems like the Chargery and the Electrodacus are better when you want more complex control. If you want simple .... just shut down everything at the same time .... BMS like the Daly would probably be the way to go.
I chose to build a 2P4S pack an only utilize one Chargery BMS .... I also plan to use all low current SSR's. The redundant shut-off for the inverter will be a low current SSR in series with the power switch ... my DC loads aren't very high current.
Controlling the charge side High voltage disconnect can also be done with separate relays or SSR's.
There are also smart shunts that can take action based on SOC.

There are "BMS police" who will say you don't want to have the BMS be the primary control for charge or load. I personally don't think that matters at all as long as there is redundancy in the protections.

Thanks for the info. I definitely want simple, I'd prefer to stay away from adding extra relays and SSRs - so maybe I'll look into the idea of having 2 separate battery banks each using DALY BMS or similar.. I do like the idea of a smart shunt - thanks for the suggestion.

 

[timmypt]

My experience so far has been that the rating of the BMS I find that the wire size is usually a little small, (they get warm) but the electronics seem to handle the rated current without issue.
If you only want a system that will provide a maximum of 300A on rare occasions, then I would only be looking for a 300-400A BMS.
In your situation, I would probably go with two 200-250A BMSs and build 2 X 4S packs in parallel. This way, if a BMS fails, you have a spare you can wire up 2P4S and keep going on one until you can get a replacement.

What are your thoughts on this?

I could go with 2 entirely separate 4s packs, each with a DALY 250A BMS ($124/USD each) with low temp cut off protection. This would give me redundancy in case a cell or BMS failed. MY question is should I rather go with larger capacity BMSs (like 300A each, though higher cost), even though my max typical load would be around 200A so the system should be able to function just fine on one of these batteries. Then I could just add a Victron BMV-712 Smart or similar battery monitor right? Do you have any other battery monitors you'd recommend?

 

[Haugen]

I like the idea of using two BMSs that each could handle your load itself. That is good advance planning for redundancy. A little extra cost up front saves a lot of grief and money later.
I'm not well versed on the battery monitor
My SolArk will handle all that for me. Future projects will probably find me digging into that realm, but not yet.

 

[bobakers]

Hi
have just set up my camper truck with a REC ABMS on 2p4s xuba 280A cells. Working with victron ccgx, 3000 240v multiplus & 525w of solar (3x175w in series) with 100/30 mppt. (another 525w & controller will go on when more panels arrive in aus)
REC was easy to set up and very adaptable. Only downside so far is the$$$.
Regards
Bob

 

[MedSailor]

@bobakers I’m about to spec the config of a REC ABMS for a very similar configuration as yours. Would you care to share the details for your REC parameters?

 

[bobakers]

@MedSailor here are the settings I'm using:

Parameter	Default Value	Set Value	Unit
chemistry	3 (LiFePO4)	3 (LiFePO4)	n.a.
capacity	200	560	Ah
balance start voltage	3.45	3.45	V
balance end voltage	3.58	3.55	V
maximum diverted current per cell	up to 2.5 (5 pp)	up to 2.5 (5 pp)	A
cell over-voltage switch-off per cell	3.85	3.65	V
over-voltage switch-off hysteresis per cell	0.25	0.25	V
cell end of charge voltage	3.58	3.55	V
End of charge hysteresis per cell	0.25	0.25	V
SOC end of charge hysteresis	5	5	%
cell-under voltage protection switch-off per cell	2.80	2.80	V
under voltage protection switch-off hysteresis per cell	0.10	0.10	V
cell under voltage discharge protection	2.90	3.00	V
pack under voltage protection switch-off timer	4	4	s
cells max difference	0.25	0.25	V
BMS over-temperature switch-off	55	55	°C
BMS over-temperature switch-off hysteresis	5	5	°C
cell over temperature switch-off	55	55	°C
cell over temperature switch-off hysteresis	2	2	°C
under temperature charging disable	-10	-0	°C
under temperature charging disable hysteresis	2	2	°C
voltage to current coefficient	0.0078125	0.0078125	A/bit
current measurement zero offset	0.0	0.0	A
maximum charging/discharging current per inverter device	120/250	120/300	A
number of inverter/charger devices	1	1	n.a.
charge coefficient	0.6	0.6	n.a.
discharge coefficient	1.5	1.5	n.a.
relay 1 voltage level	3.60	3.60	Not using
relay 1 voltage level hysteresis	-0.2	-0.2	Not using
optocoupler 2 voltage level	2.9	2.9	Not using
optocoupler 2 voltage level hysteresis	0.2	0.2	Not using
CAN communication frequency	250	250	kbit/s
SW version	2.6	2.6	n.a.

I still need to connect the 40a DC/DC charger to relay one (allow to charge) for charging whilst driving (if required)


Bob

 

[Samsonite801]

So I just bought same battery cell setup for my RV, 8x 280ah cells, and had originally planned to run with one large BMS using a 2P4S as 12v configuration. But none of the higher amp BMS I could find have the low temp cutoff actually working on them. So I switched my strategy and instead bought 2x of the highly recommended OverKill 120a BMS which DO fully support low temp cutoff:

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So now will just run as 4S2P and 2x BMS. Just for safety I'm clamping them in aluminum plates/threaded rod with aluminum floor (ordered the plates on Friday), and will put the heat pad under it and thermostat control:

Heat pad:

Amazon.com: FYSETC 3D Printer Parts and Accessories 120X120 mm/4.7X4.7 inch 12V 120W Silicone Heater Hotbed Mat Heated Bed Pad with NTC 3950 100K Thermistor Strong Adhesive Backing for Reprap Davinci Mini V2 : Industrial & Scientific

Amazon.com: FYSETC 3D Printer Parts and Accessories 120X120 mm/4.7X4.7 inch 12V 120W Silicone Heater Hotbed Mat Heated Bed Pad with NTC 3950 100K Thermistor Strong Adhesive Backing for Reprap Davinci Mini V2 : Industrial & Scientific

www.amazon.com

Thermostat:

Amazon.com

Just trying to build a set and forget battery. My RV has a Magnum Inverter 2800w (MS2812) and it calls to use battery cables that can handle max 250a (charger is rated at 125a), so my thought is that the 2x OverKill 120a BMS should be plenty of continuous load/charge rating to supply the inverter... I switched all lighting in the RV (both 12v and 120v) over to LED which helps a lot too. Hope to get this new bank built soon so I can get the SLA bank out of there. Or I might leave it there and stand up the LiFePO4 along side and make them switchable (just keep it as extra backup reserve )...

 

[Samsonite801]

What are your thoughts on this?

I could go with 2 entirely separate 4s packs, each with a DALY 250A BMS ($124/USD each) with low temp cut off protection. This would give me redundancy in case a cell or BMS failed. MY question is should I rather go with larger capacity BMSs (like 300A each, though higher cost), even though my max typical load would be around 200A so the system should be able to function just fine on one of these batteries. Then I could just add a Victron BMV-712 Smart or similar battery monitor right? Do you have any other battery monitors you'd recommend?

You might want to check Will's videos on the Daly and low temp cutoff, but he bought that one I think, and he tested the low temp cutoff and it didn't actually function (he said it was advertised as having low temp cutoff protection). He did test the OverKill 100a BMS and it does work. I went with the OverKill 120a one and they say they guarantee the low temp works on that one as well (that is, if you care about it, you can also get low temp cutoff via external means by using Victron MPPT charger and battery monitor, or the shunt solution, w/ temp probe, that can go with their brand stuff)...

 

[MedSailor]

@MedSailor here are the settings I'm using:

Parameter	Default Value	Set Value	Unit
chemistry	3 (LiFePO4)	3 (LiFePO4)	n.a.
capacity	200	560	Ah
balance start voltage	3.45	3.45	V
balance end voltage	3.58	3.55	V
maximum diverted current per cell	up to 2.5 (5 pp)	up to 2.5 (5 pp)	A
cell over-voltage switch-off per cell	3.85	3.65	V
over-voltage switch-off hysteresis per cell	0.25	0.25	V
cell end of charge voltage	3.58	3.55	V
End of charge hysteresis per cell	0.25	0.25	V
SOC end of charge hysteresis	5	5	%
cell-under voltage protection switch-off per cell	2.80	2.80	V
under voltage protection switch-off hysteresis per cell	0.10	0.10	V
cell under voltage discharge protection	2.90	3.00	V
pack under voltage protection switch-off timer	4	4	s
cells max difference	0.25	0.25	V
BMS over-temperature switch-off	55	55	°C
BMS over-temperature switch-off hysteresis	5	5	°C
cell over temperature switch-off	55	55	°C
cell over temperature switch-off hysteresis	2	2	°C
under temperature charging disable	-10	-0	°C
under temperature charging disable hysteresis	2	2	°C
voltage to current coefficient	0.0078125	0.0078125	A/bit
current measurement zero offset	0.0	0.0	A
maximum charging/discharging current per inverter device	120/250	120/300	A
number of inverter/charger devices	1	1	n.a.
charge coefficient	0.6	0.6	n.a.
discharge coefficient	1.5	1.5	n.a.
relay 1 voltage level	3.60	3.60	Not using
relay 1 voltage level hysteresis	-0.2	-0.2	Not using
optocoupler 2 voltage level	2.9	2.9	Not using
optocoupler 2 voltage level hysteresis	0.2	0.2	Not using
CAN communication frequency	250	250	kbit/s
SW version	2.6	2.6	n.a.

I still need to connect the 40a DC/DC charger to relay one (allow to charge) for charging whilst driving (if required)


Bob

Thanks Bob, very helpful. I have placed my order based on this and other info. I will probably get the cable and software to be able to tune the settings when I get even more insight.