Conext Battery Monitor ?s

[hammick]

Looking for a couple tidbits of info from anyone using the Conext Battery Monitor with their Schneider charge controller. Schneider is sending me their Monitor to install with my new XW system. I will continue to use my MPPT-60-150 charge controller.

With the latest firmware does the battery monitor take over the charging parameters of the CC and control when it goes to float? For example, can I configure it to put back say 110% of the amp hours removed from the previous charge cycle? To do this currently (using my Bogart battery monitor) I have to set the CC float voltage to the same as my absorb voltage (during the summer I use a lower voltage than absorb).

This battery monitor has leads for midpoint voltages. Obviously this is a great feature for parallel strings of batteries. I only have one string. The manual though shows an illustration for installing the midpoint battery leads in both parallel strings and just one string. What would I possibly gain by knowing midpoint voltages in my single string of batteries?

Thanks for any info.

[hammick]

Here are the illustrations for how to wire the midpoint voltage sensors. They are Va1 and Va2. The parallel illustration makes perfect sense to me. The singe string illustration makes no sense to me.


Single string illustration:



Parallel string illustration:

[hammick]

Using the single string illustration would VA2 read the voltage of the first two batteries (12v) and the VA1 read the voltage of the first four batteries (24v)? If this is the case it might make some sense if there was a third sensor to read the voltage of six batteries.

I'll call Schneider and see what they have to say. These sensors are optional and I won't hook them up if they don't give me any useful info.

[Sunking]

Mid point is a Balance Check Point. Greater than 1 volt, time to EQ batteries. Pretty simple.

[hammick]

Mid point is a Balance Check Point. Greater than 1 volt, time to EQ batteries. Pretty simple.

So helpful even on a singe string bank? So from the single string illustration if one read 12.8 volts and the other read 26.6 volts I would see a 1 volt difference (12.8 x 2 = 25.6v) and equalize?

[Sunking]

So helpful even on a singe string bank? So from the single string illustration if one read 12.8 volts and the other read 26.6 volts I would see a 1 volt difference (12.8 x 2 = 25.6v) and equalize?

No Sir. It measures the first have of the cells. Call it V1. then it measures the second half and let's call it V2. Then makes a simple calculation of V1 - V2.

Ideally you want to see 0 Volts. Depending on the number of cells you have, I am assuming 48 volts, when the voltage difference is greater or less than 1 volt, you have a problem. Most DIY EV guys use this method to determine overall cell balance because they are not using a BMS. Think of it as a Check Engine Light. You know you gotta problem that needs looked into.

[hammick]

No Sir. It measures the first have of the cells. Call it V1. then it measures the second half and let's call it V2. Then makes a simple calculation of V1 - V2.

Ideally you want to see 0 Volts. Depending on the number of cells you have, I am assuming 48 volts, when the voltage difference is greater or less than 1 volt, you have a problem. Most DIY EV guys use this method to determine overall cell balance because they are not using a BMS. Think of it as a Check Engine Light. You know you gotta problem that needs looked into.

Sunking please explain it like i'm a 2nd grader. I have eight batteries in series making a single 325ah 48v bank. Does this midpoint monitoring do anything for me and if so how?

Thanks.

[Sunking]

Sunking please explain it like i'm a 2nd grader.

Careful what you ask for.

I have eight batteries in series making a single 325ah 48v bank. Does this midpoint monitoring do anything for me and if so how?

OK class is in session children. sit down, be still, shut up, and listen.

OK you have 8 6-Volt batteries wired in series to make a 48 volt battery. We put Number Stickers on them from 1 to 8. The Negative Output is battery #1, and Positive Output is battery #8. We connect the Monitor to Battery #1 Negative post, Mid Point on the Inter-Cell Connector between Battery #4 and $5, and last connection to the Positive post on battery #8. With me so far class?

OK your Monitor takes two voltage readings: 1 is the voltage of batteries 1 to 4 and let's call it V1. It also measure the voltage of batteries 5 to 8 and call it V2. In a perfect world both V1 and V2 are equal. Example V1 = 27.2 and V2 = 27.2. Now you do some simple math in the Black Box Monitor:

V1 - V2, and V1 +V2

so

27.2 - 27.2 = 0 volts. Batteries are Balanced or at least leads us to believe they are.

27.2 + 27.2 = 54.4 volts. This is your total battery voltage. Your Monitor will then use that voltage to determine State of Charge. Pretty useless IMHO. Only a hydrometer can do that on a working system. We have covered that ground already.

The V1 - V2 voltage can be used to determine battery health or Balance. Ideally it should be 0-Volts if every battery voltage is equal. It is basically a Lazy Man way to get out of measuring Specific Gravity and individual battery voltage so frequently. Think of it like a Check Engine Light in your car. Does not tell you a lot other than to take a closer look and see what is wrong. The issue I take with them is it has 24 huge holes you could drive a truck through. It does not tell you which battery or batteries are in trouble, and it can miss a problem.

Your 6 volt batteries are really 3 2-Volt battery cells crammed in a common box wired in series. A 48 volt battery are 24 2-Volt batteries in series. Your monitor cannot see those 24 cells. All it sees is 12-batteries grouped together x 2. However in theory with each cycle your batteries will get out of balance. As that happens in theory, it should see the V1-V2 go from 0 volts and keeps up to 1 volt, or down to -1 volt. In theory that means your batteries are in need of Equalization and further investigation nis needed to see what is going on. However it can as easily miss a problem like battery #2 and battery 7 are both bad and cancel each other out and you will not see a problem other than Total Battery Voltage would be either lower or higher than normal.

But here is a catch, There is no such thing as a normal voltage. When charging you will see voltages as high as 60 volts, and under discharge as low as 48 volts.

Any questions?

Class dismissed.

[hammick]

Sunking your explanation makes sense. Thank you. What was confusing me is the diagram from the Schneider manual I posted above (method no. 1). They hava Va1 on the positive post of battery no. 4 and Va2 on the positive of battery no. 2. Maybe that is correct but I cannot wrap my head around it.

A little time with my batteries and a multimeter and I'm sure I'll figure it out even if Schneider's manual is incorrect.

[Sunking]

Sunking your explanation makes sense. Thank you. What was confusing me is the diagram from the Schneider manual I posted above (method no. 1). They hava Va1 on the positive post of battery no. 4 and Va2 on the positive of battery no. 2. Maybe that is correct but I cannot wrap my head around it.

A little time with my batteries and a multimeter and I'm sure I'll figure it out even if Schneider's manual is incorrect.

Well then I understand why you are confused. I never looked at your diagram closely until now. I have no clue what diagram 1 is. For Crack Heads I guess. Then again I have never used your product. I would be on the phone with Tech Support and ask for the CHIC (crack head in charge)

[hammick]

Well then I understand why you are confused. I never looked at your diagram closely until now. I have no clue what diagram 1 is. For Crack Heads I guess. Then again I have never used your product. I would be on the phone with Tech Support and ask for the CHIC (crack head in charge)

Thanks. I don't feel like such a moron now. I will call them tomorrow. Schneider has pretty good tech support and you usually get someone pretty quick.

[Sunking]

Thanks. I don't feel like such a moron now. I will call them tomorrow. Schneider has pretty good tech support and you usually get someone pretty quick.

You are welcome. Your not a Moron, you seen something was not right.

Like I said I do not have experience with that product, but I damn sure know what Mid Point monitoring is, and Diagram 1 is not Mid Point. Don't give any thought as to why it is nothing connected to the Negative Battery Term post because it is common in the meter and already has that point connected

I have no clue what they show Diagram 1 with the connection between batteries 2 and 3 which cuts out battery 1 and 2. I can only assume it is an error.

[hammick]

OK I spoke with what I would consider lower level tech support at Schneider. They said I don't have to connect the Va2 wire if I have a single string. So I believe connecting the Va1 wire at the positive terminal of the fourth battery will give me the voltage of the middle of the string (four batteries). If this reading is more than 1v difference than 50% of the total battery string voltage then I should consider equalizing the batteries? I guess I could attach the Va2 as they describe and get the 12v battery voltage of the first two batteries and expect this to be close to 50% of the mid point voltage? They should have included a Va3 wire for us single string guys so I could have the sixth battery voltage.

Doesn't sound like a very helpful feature with a single string but it's there so I'll hook it up. SG readings seem like the only real way to know for sure.

Thanks for the seminar Sunking!


In a few months I'll hopefully have a review of the monitor and whether it can dictate float based upon a percentage of AH returned.

[hammick]

Turns out the shunt that comes with the XW Battery Monitor does fit nice and snug in the PDP, albeit inverted. Pics of the shunt install and of PDP attached.


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[hammick]

More pics



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