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BMS 200ah separate ports for 24v 280ah battery, low temp disconnect

Lorenzo90

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Nov 27, 2020
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Hi,
I'm looking for a BMS that can handle 200-250a of discharge and at least 130a of charge.
It needs to have low temp disconnect.
It needs to have a separate ports. The battery will be in a van, and I still want to power the heater (so to heat the batteries as well) at low temps, instead of having a dead battery.
What are my options on the market?

If ther's nothing like that with low temp disconnect, what is a good way to integrate an external low temp disconnect on my charging side?

Cheers
 
Hi,
I'm looking for a BMS that can handle 200-250a of discharge and at least 130a of charge.
It needs to have low temp disconnect.
It needs to have a separate ports. The battery will be in a van, and I still want to power the heater (so to heat the batteries as well) at low temps, instead of having a dead battery.
What are my options on the market?
Starting with what won't work. If you need >100A @ 24V and low temp disconnect, you can rule out the standard Daly BMS and the BMSes sold by Overkill Solar.

A BMS that uses external switching (Chargery, SBMS0, TinyBMS, 123smartBMS) and has low temp protection (all these options have some form I believe but you'll want to check into specifics) would fit the bill. But range from somewhat more advanced to much more advanced.

There are likely FET based BMSes that would fit the bill. I would look into Heltec and JBD / LLT power, a forum search will return a bunch of results. I believe both may offer >200A plus models with LTP.

If there is nothing like that with low temp disconnect, what is a good way to integrate an external low temp disconnect on my charging side?
The answer to this will depend somewhat on your charge sources. If Solar will be your only charge source a MPPT controller with low temp protection would fit the bill, Victron MPPT controllers can do this.

Its possible (probable) that some combination of Victron products like the Battery Sense, BMV-712, and/or Battery Protect devices could be used for a more sophisticated solution for multi-charge-source low temp protection, but that is over my head and beyond my knowledge. @HaldorEE has spent some time understanding the BMV, he may be able to help.
 
Still theoretical since I am still building my battery pack. Top balancing the cells this weekend!

I bought the Heltec 3.2V, 8S, 300A FET based BMS that claims to have a low temperature disconnect. I will be testing this to see if it works. My design should never draw more than 150A so I am confident the BMS can handle that.

I am a believer in belt and suspenders so I am also adding a temperature sensor to my Victron BMV-712 battery monitor. The BMV-712 is controlling all of the charge sources in my system. Victron Multiplus, Victron MPPT Smart Solar and Victron Orion-TR DC-DC alternator charger.

The BMV-712 has a relay output that I am wiring to control the Multiplus and the Orion. The Smart Solar will be controlled via Bluetooth from the BMV-712. God I love Victron equipment.

The loads are being handled with individual low voltage disconnects at 10% SOC.

My intention is that the BMS should only ever disconnect if the cells get very unbalanced. The load and charge sources should never push the battery pack to the point that the BMS has to intervene. I am glad to have it as backup, but it should only be that, a last chance to save the battery pack if something else goes wrong.
 
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So, i already have a b2b charger that sadly doesn't have a temp disconnect and I will use an all in one mppt inverter that again doesn't have a temp disconnect.
Could I use the victron bmv-712's relay output to regulate the chargers input?

Btw I just realized that probably the all in one inverter has only one lead for charging and discharging the battery, so a separate port probably won't work for this set up.
That would be another reason for regulating the inputs externally.
If the battery goes -0° and I can cut out the all in one mppt inverter and the b2b with the bmv-712. (I could isolate just the solar array from the all in one inverter, but that would leave vulnerable if connected to shore power)
I will lose the inverter but I can maintain the AC system active and be able to start the heater.

I still have to figure out how to deal with relays and contactors for high currents (120a for the charging part and 200a discharge)
Could anyone point me towards some good guides/articles regarding that?
 
One of these Blue Sea 500A remote control battery switches would be perfect for this application. It is a magnetic contactor with a manual control switch and has very low on-current draw (13mA). The low current consumption means it won't get hot and it won't run down your batteries.

For 12V systems: https://www.bluesea.com/products/77...Switch_with_Manual_Control_Auto-Release_-_12V

for 24V systems: https://www.bluesea.com/products/77...Switch_with_Manual_Control_Auto-Release_-_24V

These are not cheap ($170+).
 
The inverter/charger combination makes it more complicated. I am using a Victron Multiplus and I trust it to manage the low voltage disconnect by itself, so I am only using BMV-712 to manage charge control (with low temperature cutoff). The Multiplus has an input I can configure for this purpose and connect to the BMV-712.

The Victron equipment seems expensive when you first look at it. Then you find out how much it can costs and what a pain it is to make the cheaper stuff do the same things and suddenly it no longer seems expensive any more.
 
So, i already have a b2b charger that sadly doesn't have a temp disconnect and I will use an all in one mppt inverter that again doesn't have a temp disconnect.
Could I use the victron bmv-712's relay output to regulate the chargers input?

Btw I just realized that probably the all in one inverter has only one lead for charging and discharging the battery, so a separate port probably won't work for this set up.
That would be another reason for regulating the inputs externally.
If the battery goes -0° and I can cut out the all in one mppt inverter and the b2b with the bmv-712. (I could isolate just the solar array from the all in one inverter, but that would leave vulnerable if connected to shore power)
I will lose the inverter but I can maintain the AC system active and be able to start the heater.

I still have to figure out how to deal with relays and contactors for high currents (120a for the charging part and 200a discharge)
Could anyone point me towards some good guides/articles regarding that?
The BMV and the Blue Sea relay are good solid products by all accounts, but expensive and you would still need to factor in the cost of a BMS (probably >$500 when all is said and one), I think there may be better paths to take based on what you have and have not purchased so far.

The way I see it you have two problems to solve:
1. You need a BMS, high current, ideally with separate control of charge/discharge current
2. You need low temperature protection for multiple charge sources.

With the right BMS, you could kill all birds with one stone. The question is, is there a right BMS for your application that satisfies all of the above.

Here is where we should think about the third type of FET based BMS, 'hybrid port.' The most common example is the JBD Smart BMS sold by Overkill Solar. It is wired like a common port BMS but functions for the most part like a separate port BMS. This seems ideal for situations like yours. But can one be found with high enough current ratings for your needs? I'm not sure. One common issue with this type of BMS is charge current will be more limited in many cases.

@HaldorEE is your Heltec BMS the 'hybrid port' topology (wired like a common port, but separate control of charge/discharge)?
Another option to look into is the high current models of JBD BMS, I know they go up to 200A maybe higher.

Another option is a BMS like the SBMS0 which controls chargers and load control devices directly, but I'm not sure that the MPP AIO would allow separate remote control of Charging, inverting, and solar, most are not capable of this. The Victron Multiplus is the only Inverter/Charger I'm aware of that can function this way.

Finally you could just opt for a common port BMS and sacrifice the finer grained control of separate control for charge/discharge. In that case most relay based solutions would work, and probably some high current FET based solutions.
 
The BMV and the Blue Sea relay are good solid products by all accounts, but expensive and you would still need to factor in the cost of a BMS (probably >$500 when all is said and one), I think there may be better paths to take based on what you have and have not purchased so far.

The way I see it you have two problems to solve:
1. You need a BMS, high current, ideally with separate control of charge/discharge current
2. You need low temperature protection for multiple charge sources.

With the right BMS, you could kill all birds with one stone. The question is, is there a right BMS for your application that satisfies all of the above.

Here is where we should think about the third type of FET based BMS, 'hybrid port.' The most common example is the JBD Smart BMS sold by Overkill Solar. It is wired like a common port BMS but functions for the most part like a separate port BMS. This seems ideal for situations like yours. But can one be found with high enough current ratings for your needs? I'm not sure. One common issue with this type of BMS is charge current will be more limited in many cases.

@HaldorEE is your Heltec BMS the 'hybrid port' topology (wired like a common port, but separate control of charge/discharge)?
Another option to look into is the high current models of JBD BMS, I know they go up to 200A maybe higher.

Another option is a BMS like the SBMS0 which controls chargers and load control devices directly, but I'm not sure that the MPP AIO would allow separate remote control of Charging, inverting, and solar, most are not capable of this. The Victron Multiplus is the only Inverter/Charger I'm aware of that can function this way.

Finally you could just opt for a common port BMS and sacrifice the finer grained control of separate control for charge/discharge. In that case most relay based solutions would work, and probably some high current FET based solutions.
mmm if I take in consideration a common port bms, could I bypass it for essentials loads like lights and diesel heater? without heater i wouldn't be able to heat up the battery, unless i hook them up to the van battery, and run them with the engine on until the temp is up..
is the charging rate on the common port bms the same as the as discharge rate?
(any product i should look into it?)

what about using 2 bms in parallel?

anyway i keep forgetting that the all in one inverter has only one cable for charging and discharging, so a separate port won't work..only a common port/hybrid

furthermore I'm not familiar with most of the bms brands/tipes (daly aside), so it would be of huge help to have direct reference to specific products (even better if they are available in europe)..
 
Still theoretical since I am still building my battery pack. Top balancing the cells this weekend!

I bought the Heltec 3.2V, 8S, 300A FET based BMS that claims to have a low temperature disconnect. I will be testing this to see if it works. My design should never draw more than 150A so I am confident the BMS can handle that.

I am a believer in belt and suspenders so I am also adding a temperature sensor to my Victron BMV-712 battery monitor. The BMV-712 is controlling all of the charge sources in my system. Victron Multiplus, Victron MPPT Smart Solar and Victron Orion-TR DC-DC alternator charger.

The BMV-712 has a relay output that I am wiring to control the Multiplus and the Orion. The Smart Solar will be controlled via Bluetooth from the BMV-712. God I love Victron equipment.

The loads are being handled with individual low voltage disconnects at 10% SOC.

My intention is that the BMS should only ever disconnect if the cells get very unbalanced. The load and charge sources should never push the battery pack to the point that the BMS has to intervene. I am glad to have it as backup, but it should only be that, a last chance to save the battery pack if something else goes wrong.
i just look those bms up, they don't say anything bout charging rate, do you know how much is that?
i could take 2 12v 300a common port bms from them and parallel 2 4s 12v batteries... could't I?
 
Look into 'Hybrid Port' BMS (a term used on this forum, not elsewhere)

I suggest reading this primer by @FilterGuy to get a basic familiarity on types and functions of BMS
 
i just look those bms up, they don't say anything bout charging rate, do you know how much is that?
i could take 2 12v 300a common port bms from them and parallel 2 4s 12v batteries... could't I?
150A Charge, 300 Discharge. Says so right on the label.

PXL_20210127_040836102[1].jpg

If you have more than 150A of charging at 24V on an RV, then I am going be serious impressed. That is 4000W!
 
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The different currents make me suspect this is a hybrid port version. That is great. Means a low voltage disconnect won't prevent you from charging.
 
The different currents make me suspect this is a hybrid port version. That is great. Means a low voltage disconnect won't prevent you from charging.
What about low temp disconnect? Does it stop charging only ora both load and charge? Does it have Bluetooth or some other way to monitor it/modify parameters?
 
What about low temp disconnect? Does it stop charging only ora both load and charge? Does it have Bluetooth or some other way to monitor it/modify parameters?
This one is braindead. Claim is low temp disconnect. I will be testing it this weekend. Hopefully I get as far as the cold temp disconnect.
 
This one is braindead. Claim is low temp disconnect. I will be testing it this weekend. Hopefully I get as far as the cold temp disconnect.
So you can't really check and see what is going on with the BMS other that checking each cells voltage with a meter?
 
Correct.

I will be watching cell voltages like a hawk during my capacity test.

If the BMS let's any cells get below 2.5V or above 3.65V, then I will not use this BMS.
 
Correct.

I will be watching cell voltages like a hawk during my capacity test.

If the BMS let's any cells get below 2.5V or above 3.65V, then I will not use this BMS.
Interested to see how this test goes. Looking to pick a couple of these up as well
 
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