Checking Chargery voltage measurements

[Cal]

This is a heads up for Chargery as they are redesigning their BMS. Chargery has a red ribbon cable which attaches to each of the cells to measure cell voltage. There's a problem with this mechanism as power is drawn from the ground voltage sense cable and the last sense cable connection. There's a voltage drop in these two cables leading to incorrect cell measurements for the first and last cell.

I'm using a Fluke 87 III meter to measure cell voltage directly at the cells. The meter has 0.05% + 1 digit accuracy. It is calibrated each year.

Fluke vs. Chargery comparison:

Cell 1: 3.382V ... 3.361V
Cell 2: 3.380V ... 3.381V
Cell 3: 3.381V ... 3.380V
Cell 4: 3.381V ... 3.370V

The first cell measures 21 mV low and the last cell measures 11 mV low. This can become a problem when balancing.

Chargery needs to add separate power cables to the battery to eliminate this measurement error. Power is drawn to operate the BMS and relays, etc.

 

[JoeHam]

This is a heads up for Chargery as they are redesigning their BMS. Chargery has a red ribbon cable which attaches to each of the cells to measure cell voltage. There's a problem with this mechanism as power is drawn from the ground voltage sense cable and the last sense cable connection. There's a voltage drop in these two cables leading to incorrect cell measurements for the first and last cell.

I'm using a Fluke 87 III meter to measure cell voltage directly at the cells. The meter has 0.05% + 1 digit accuracy. It is calibrated each year.

Fluke vs. Chargery comparison:

Cell 1: 3.382V ... 3.361V
Cell 2: 3.380V ... 3.381V
Cell 3: 3.381V ... 3.380V
Cell 4: 3.381V ... 3.370V

The first cell measures 21 mV low and the last cell measures 11 mV low. This can become a problem when balancing.

Chargery needs to add separate power cables to the battery to eliminate this measurement error. Power is drawn to operate the BMS and relays, etc.

Tagging @Chargery to be sure Jason sees this.

 

[grizzzman]

This is a heads up for Chargery as they are redesigning their BMS. Chargery has a red ribbon cable which attaches to each of the cells to measure cell voltage. There's a problem with this mechanism as power is drawn from the ground voltage sense cable and the last sense cable connection. There's a voltage drop in these two cables leading to incorrect cell measurements for the first and last cell.

I'm using a Fluke 87 III meter to measure cell voltage directly at the cells. The meter has 0.05% + 1 digit accuracy. It is calibrated each year.

Fluke vs. Chargery comparison:

Cell 1: 3.382V ... 3.361V
Cell 2: 3.380V ... 3.381V
Cell 3: 3.381V ... 3.380V
Cell 4: 3.381V ... 3.370V

The first cell measures 21 mV low and the last cell measures 11 mV low. This can become a problem when balancing.

Chargery needs to add separate power cables to the battery to eliminate this measurement error. Power is drawn to operate the BMS and relays, etc.

Have you tried external power? I have the same issue cell one is around .12 low two and three are close. And cell four is .25 low. And that caused lots of issues with balancing. I think tomorrow ill power it externally. Charge and observe.

 

[Steve_S]

Concur with Grizzman, please try the BMS with an external power supply.
Do you have the B1- & B1+ on the cell with the NEG battery wire ?

 

[grizzzman]

This is a heads up for Chargery as they are redesigning their BMS. Chargery has a red ribbon cable which attaches to each of the cells to measure cell voltage. There's a problem with this mechanism as power is drawn from the ground voltage sense cable and the last sense cable connection. There's a voltage drop in these two cables leading to incorrect cell measurements for the first and last cell.

I'm using a Fluke 87 III meter to measure cell voltage directly at the cells. The meter has 0.05% + 1 digit accuracy. It is calibrated each year.

Fluke vs. Chargery comparison:

Cell 1: 3.382V ... 3.361V
Cell 2: 3.380V ... 3.381V
Cell 3: 3.381V ... 3.380V
Cell 4: 3.381V ... 3.370V

The first cell measures 21 mV low and the last cell measures 11 mV low. This can become a problem when balancing.

Chargery needs to add separate power cables to the battery to eliminate this measurement error. Power is drawn to operate the BMS and relays, etc.

Cal, I just hooked up external power to the BMS8T, and now the voltages are very close to correct. Could you hook your unit up to external power to verify? Thanks.

 

[Solarfun4jim]

:-( not another issue to deal with. Just when i thought i had resolved most....now we have to adjust set ups to compensate for inaccuracies.
So now i need a 24v3A power adapter....schucks.
I didnt mind so much SOC calculations being astray, but the voltages were paramount. Will be following this thread closely.

 

[grizzzman]

:-( not another issue to deal with. Just when i thought i had resolved most....now we have to adjust set ups to compensate for inaccuracies.
So now i need a 24v3A power adapter....schucks.
I didnt mind so much SOC calculations being astray, but the voltages were paramount. Will be following this thread closely.

Look at the bright side, It will easer to put in a remote BMS on-off switch

 

[Solarfun4jim]

I take it the 'extra' power leads needed should have the negative connection past the shunt rather than the neg battery terminal, so that this parasitic load gets accounted for in SOC calcs?
I have zero knowledge of electronics, but would it be possible to hook up some kind of 3A current regulator between the positive busbar(on a 24v nominal system) and the shunt to power this chargery externally?
Thinking from a position of ignorance....help appreciated.

 

[grizzzman]

I take it the 'extra' power leads needed should have the negative connection past the shunt rather than the neg battery terminal, so that this parasitic load gets accounted for in SOC calcs?
I have zero knowledge of electronics, but would it be possible to hook up some kind of 3A current regulator between the positive busbar(on a 24v nominal system) and the shunt to power this chargery externally?
Thinking from a position of ignorance....help appreciated.

There is an external power port next to the battery/External power switch on the main BMS controller. This removes power from the battery through the balance cables. And yes the shunt needs to account for the current.

 

[Solarfun4jim]

There is an external power port next to the battery/External power switch on the main BMS controller.

Yes, but what do you plug into it, that is 15-60vdc and 3A ?
I do not want to power from ac adapter, but rather from the dc source of the battery pack....

or...is my lack of knowledge showing....i was thinking that the current needed to be regulated to exactly 3A, but if i connected to the 24v battery pack directly, through an push in plug, would it only draw 3A? This is where my ignorance is dangerous!
Dont want to fry my BMS this early in the game....lol

 

[Cal]

You need a buck regulator to drop 24V to 15V.

Connect regulator from 24V buss bar to other side of current shunt.

Edit: changed regulation from 12V to 15V.

Grizzman- I'll check those measurements tomorrow. I'm data logging my new DIY BMS the entire day.

 

[Solarfun4jim]

You need a buck regulator to drop 24V to 12V.

Regulator (just a suggestion, there may be better ones)

Connect regulator from 24V buss bar to other side of current shunt.

Grizzman- I'll check those measurements tomorrow. I'm data logging my new DIY BMS the entire day.

Im not understanding this as i thought the external supply had to be above 15VDC?

From the spec sheet page 6..
"The voltage of external power：15-60V, 3A"

But thanks for the idea....

 

[Steve_S]

15V/3A is so that the BMS can also drive the Relays/Contactor's attached.
If you are using a DCC you don't need so much at <0.5A, is Energy Saver Relays, you need a bit more about 1A or so pending on make/model.
The BMS itself will only pull in what it needs to operate + what it takes to run the relays.
The power spec is to be able to support two electromechanical relays. (the worst for energy usage).

 

[Cal]

You're correct. You need 15V for external power.

I'm not sure if connecting regulator ground to the other side of the shunt is OK. You may be mixing grounds within the BMS. Chargery should verify that's OK.

 

[grizzzman]

You need a buck regulator to drop 24V to 15V.

Connect regulator from 24V buss bar to other side of current shunt.

Edit: changed regulation from 12V to 15V.

Grizzman- I'll check those measurements tomorrow. I'm data logging my new DIY BMS the entire day.

Ok.Thanks. As far as external voltage, here is what the Manuel. States "The voltage of external power：15-60V, 3A" currently my boost converter doesn't work. ( inspection found that resister R1 is missing) It fired up the BMS at 13.11 volts.

 

[Steve_S]

Ok.Thanks. As far as external voltage, here is what the Manuel. States "The voltage of external power：15-60V, 3A" currently my boost converter doesn't work. ( inspection found that resister R1 is missing) It fired up the BMS at 13.11 volts.

Jason actually responded previously, that if the relays were low draw and lower volt (like the TE 9 volt ones) then you could get away with 12V external power. I looked but could not find it in the many threads.

 

[Solarfun4jim]

Perhaps something like this listed below, connected between the 24v battery pack and the external power input on the main unit???

DC 5.5-30V to 0.5-30V 35W CC CV Buck Boost Step Up/Down LCD Power Supply Module | eBay

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input voltage 24v ...output voltage 15v and 3A steady current.

 

[grizzzman]

Perhaps something like this listed below, connected between the 24v battery pack and the external power input on the main unit???

DC 5.5-30V to 0.5-30V 35W CC CV Buck Boost Step Up/Down LCD Power Supply Module | eBay

Find many great new & used options and get the best deals for DC 5.5-30V to 0.5-30V 35W CC CV Buck Boost Step Up/Down LCD Power Supply Module at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

input voltage 24v ...output voltage 15v and 3A steady current.

Yes

 

[JoeHam]

input voltage 24v ...output voltage 15v and 3A steady current.

What am I missing?

The Chargery can accept up to 60v correct??

No need for a buck converter at all then???

 

[Solarfun4jim]

What am I missing?

The Chargery can accept up to 60v correct??

No need for a buck converter at all then???

@JoeHam
Thanks Joe,
I'm totally inexperienced in electrics....so how would you connect the external power input to the battery pack to provide the required 3A
I just assumed you needed the converter to regulate the current to the required 3A???