☆Doesn't Support Series Connection and parallel Connection

[hwse]

Any opinions as to what this statement means?

I was ready to order one of the new Hankzor JK-B2A8S20P-H BMS with Bluetooth /RS485 /Heat function which is the new 4s version of the JK BMS with 2-amps active balancing and 200A charge and discharge. Then in reading the description of the functions I came across the following statement
"☆Doesn't Support Series Connection and parallel Connection"
I really do not know what they mean by that.
Are they saying that you cannot build a 2p4s battery with (8) cells and a single BMS. Or does it mean that batteries built with this BMS cannot be linked to other batteries in either series or parallel. Both sound like a very heavy toll to pay.

Let's say some enterprising company wants to build 100A 12-volt drop-in batteries with this BMS as so many are now doing with the JBD. Does this mean that their battery could only be used as a single standalone batter and not connected with others to create higher amperage banks or in series to create higher voltage?

 

[Steve_S]

I have a feeling that it means that you cannot connect "completed" batteries in Series AND parallel.
Completed battery being the cells & BMS complete as a unit.
You can connect several batteries in Parallel as that has little effect on volts/amps passing through the BMS, but if connecting in series the MOSFETS have to be capable of handling 24/48V (see specs for particular BMS) but that can easily negate the use of Parallel due to the loading potentials.

The best option if 12V and staying that way, is to use larger cells (200AH instead of 100AH) to get the individual packs up to what you need, keeping the Straight 4S config, then adding packs in Parallel for more AH Storage.

If your intention is to go with 24V, then build a standard 8S Pack with appropriately sized cells. Setting "packs" in series to increase voltage can be a very tricky thing to do and quite often leaves folks disappointed and in rare instances they are left with "smoked" packs.

 

[hwse]

Thanks for the reply. I live in a 12-volt world. Everything on my boat is 12v and my plan is to use EVE 280K in either (8) cells in 2p4s with one BMS or two 4s batteries each with its own BMS for my boat. It will be connected to an EVO 1212 based on researching them after your nice reviews.

On my motorhome I need more power and have a Magnum 2000w inverter, so I plan to use (12) 280k cells to make three 4s batteries each with a BMS so that none of them are working near the limit. It has a coulomb counter and I often see loads in the 170A to 190A range so a 200A BMS in a 3p4s configuration might be working too hard.

 

[Steve_S]

Paralleling cells will not allow you to use more Amps which is capped by the BMS. With ANY Fet Based BMS, you are best to oversize by at least 20% of the max load you expect. 200A BMS should be 250A to prevent hitting the performance edge.

The EVO's are Great and for many too "deluxe" but as you've seen, that is worth it... Damn the manuals, really takes a LOT of study and so comprehensive to boot.

Do keep in mind as well, that Paralleled Battery Packs do indeed divide both Load & Charge and do so proportianaly. My stack of 6 Primary packs really shows that to be effective. This does not happen within a battery pack.

Like you, I do not use an AIO, I use Midnite Classic-200, Samlex Inverter/Charger but in between all of that I have a Midnite 250A E-Panel with a primary 250A Main Breaker... Even during my thrash test cycle I got it pulling 255A from Batt and the batts (4 at the time) did not even blink and the 175AH packs did discharge at a lower rate than the 280AH packs.

12V@250A = 3000W uncorrected and in reality you should not cross that magic 250A line.

BMS' are a bit tricky when it come to 4S High Amp and quite a few of the better BMS' need "help" to be used with 4S, usually an external power supply. Quite a few folks here have had to tackle that one.

Lastly I have to reiterate once again, that using any grade of LFP below the (A-) level is best to use only Straight #S Configuration will result in peculiar side effects and potentially (lower grade = higher occurrence) paired cell mismatches where one cell in a "pair" goes off balance (usually due to different IR levels at the same voltages.

 

[hwse]

Just to clarify. Everything DC powered that I own is 12-volt, so this is only about 12-volt systems. The BMS that I will use is the JK 4s 200A unit with 2A active balance. It is rated for 200A charge/discharge with 350A surge for 5 minutes. It uses seperate strings of (20) 100A FET's for both charge and discharge.

1. Boat with a need for 560A 12-volt for mostly 12v loads. I will charge the laptop and run the Shark vacuum from the EVO but the primary reason for it is the 60A charger plus 50A of pass through solar. The EVO will be the 12v 1200W and no consideration for anything bigger. This will either be 2p4s with one JK BMS or two 12-volt batteries each having its own BMS.

2. Class A diesel all electric motorhome. Almost everything is 110v AC so when I am not plugged in, I live on my Magnum 2000W unless I need air conditioning at which point I fire up the 10kW generator. If I need air-con, I need all three of the 15000BTU units and no battery system will ever be able to do that. Full stop. I want to have at least 840A @ 12-volts for this coach.

 

[wattmatters]

It is rated for 200A charge/discharge with 350A surge for 5 minutes. It uses seperate strings of (20) 100A FET's for both charge and discharge.

Andy's JK BMS blew when run at a little over 200A:

Looks like one of the FETs cracked and let out a little magic smoke.

 

[hwse]

Not quite what happened. Andy's JK ran at loads over 200 for exactly 200-seconds (5 minutes) which is what the Max Discharge Current Delay was set to. The FET blew when the BMS did a full stop shutdown while under a 205A discharge. It still worked perfectly well although it now had 19/20th of the total capacity in the FET string given that one of the twenty blew. He went over all of this in his follow-up video. He ran it at discharges from 203A -242A and it stayed cool showing a 44ºC max FET temp. Then at 200s it shut down as it should and that is when it blew the FET. I would like to see what a Daly or JBD would do in those conditions.

 

[740GLE]

If it’s meant to open up and break load exceeding its rating, shouldn’t it handle breaking that load?

 

[wattmatters]

Not quite what happened. Andy's JK ran at loads over 200 for exactly 200-seconds (5 minutes)

300 seconds.

If it’s meant to open up and break load exceeding its rating, shouldn’t it handle breaking that load?

This.

 

[rhino]

I think this is a case of giving the user too much power with the settings. Keep in mind the settings were configured to not turn off until 5 minutes of continuously exceeding the limit of the BMS. The safer option would have been to drastically limit how long it could exceed its limit and/or shut off when the FETs got too hot. Five minutes is pretty long for exceeding the stated limit. The app showed MOS temp of 65C when the BMS turned off and FET blew. We aren't even sure where that temp sensor is since there are 20 FETs just for discharge so an individual one could have been much hotter. I don't think there would have been an issue if you set the limit to a much shorter time.

 

[wattmatters]

I think this is a case of giving the user too much power with the settings.

I think this is a case of when the product doesn't perform as per its own specifications.

The 200A / 300 seconds cut off were the BMS's default settings.

 

[Steve_S]

The 200A / 300 seconds cut off were the BMS's default settings.

Maybe no one cross checked, most BMS' will handle a surge as above BUT have their DEFAULTS set to 30 Seconds, not 300. And extra 0 typo is a pretty good possibility The Over capacity is just for Momentary Surge handling, not for long use....

Sometimes Andy comes to Conclusions based on biased assumptions. IE the Assumption that "Over Current" can run for more than just a burst is ONE such ASSumption. Worst part, He Knows Better.

 

[YYDS]

Battery pack can not be string parallel because the capacity of the battery is not completely consistent, there are inconsistent materials, inconsistent battery string parallel may lead to bms failure, and the manufacturer to communicate the specific parameters is actually can be connected in parallel, the manufacturer is afraid that you randomly string parallel failure when the time needs to be repaired

 

[Manfredi]

It is possible that Andy was powering an inductive load at > 200A when one of the MOSFET blew. This will produce a voltage spike going well after the nominal 48V, and possibly beyond 100V which is the rating limit of the MOSFETs used. This phenomenon is controllable via some sort of spike suppression mechanism, and I do know if JK has implemented correctly this in circuitry.

Another possible reason is lack of synchronization: a large parallel group of MOSFET will not divide equally the current if some interrupt before the others. Suppose that for some reason 18 MOSFET go OFF in anticipation, and 2 are still ON connected, these two will bear more than 100A each at time of interrupt.

 

[hwse]

Maybe no one cross checked, most BMS' will handle a surge as above BUT have their DEFAULTS set to 30 Seconds, not 300. And extra 0 typo is a pretty good possibility The Over capacity is just for Momentary Surge handling, not for long use....

Sometimes Andy comes to Conclusions based on biased assumptions. IE the Assumption that "Over Current" can run for more than just a burst is ONE such ASSumption. Worst part, He Knows Better.

Here is the spec sheet. They clearly say 350A for 2-minutes

 

[hwse]

It is possible that Andy was powering an inductive load at > 200A when one of the MOSFET blew. This will produce a voltage spike going well after the nominal 48V, and possibly beyond 100V which is the rating limit of the MOSFETs used. This phenomenon is controllable via some sort of spike suppression mechanism, and I do know if JK has implemented correctly this in circuitry.

Another possible reason is lack of synchronization: a large parallel group of MOSFET will not divide equally the current if some interrupt before the others. Suppose that for some reason 18 MOSFET go OFF in anticipation, and 2 are still ON connected, these two will bear more than 100A each at time of interrupt.

His loads were his Telsa charger plus a power supply so that he could fine tune the amps used.
The lack of synchronization is the current general hypothesis.

 

[Manfredi]

A power supply with iron transformer is a good example of inductive load ...

 

[hwse]

A power supply with iron transformer is a good example of inductive load ...

Benchtop power supply with full control CC/CV control.

 

[gelmjw]

Any opinions as to what this statement means?

I was ready to order one of the new Hankzor JK-B2A8S20P-H BMS with Bluetooth /RS485 /Heat function which is the new 4s version of the JK BMS with 2-amps active balancing and 200A charge and discharge. Then in reading the description of the functions I came across the following statement
"☆Doesn't Support Series Connection and parallel Connection"
I really do not know what they mean by that.

Likely due to the heater(s). Will mentioned that recently in a video about the SOK heated battery.

 

[hwse]

Likely due to the heater(s). Will mentioned that recently in a video about the SOK heated battery.

It is listed for both versions of the 4s and Nami said in one of her responses that it applies to all JK BMS's