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diy solar

Finally found a LiFePO4 BMS with Low-temp Charging Protection

I just talked to Battery Hookup about this BMS and got a lot of great info.
  1. They do parallel bank hookups all the time
    1578600642082.png
  2. They tested one of these BMSs for a week at 100 amps without seeing a problem.
  3. He says he finds that the price of higher amp BMS goes up so fast that it is lower overall cost to do multiple parallel banks to get higher amps.
  4. They do not recommend serial bank hookups. (I did not get into why with him... I wish I would have) However, see next point.
  5. They expect to get an 8S version of these in in 2-3 weeks. The price should be less than $20 more.
  6. These BMS are being custom programed for Battery Hookup to get the low-temp cut-off. (He did not say this but that means if you buy from the manufacturer, you won't get the low temp shut-off. The link in an earlier post to the manufacturers site seems to confirm this)
  7. The manufacturer of this BMS is the same manufacturer that builds the BMS for Valence.
He seemed like a nice guy and my BS detector did not go off while I was talking to him..... I felt I could trust his statements.

(I am not in any way connected to Battery Hookup)
 
Good info @FilterGuy I had been wondering if I should do a 2P4S setup and use one BMS or run 2, 4S and use two BMS's. I think running two independent banks give some redundancy should one BMS/Battery bank fail. Sure it cuts my AH in half but I still have power versus the potential to not have any.
 
Yeah, they are super cool. I like Tom from battery hook up and he's my buddy at this point. Great guy. A lot of the employees there are Tom's family.

They also test used/new cells all day, so they are very knowledgeable.
 
chevymike said:
I think running two independent banks give some redundancy should one BMS/Battery bank fail. Sure it cuts my AH in half but I still have power versus the potential to not have any.
Click to expand...

The guy at Battery Hookup mentioned that too.
 
@FilterGuy .... I'm glad you were able to get the information. I have sent 2 emails to sales@batteryhookup.com asking if the BMS could be configured on 2 seperate batteries in parallel ..... and have yet to get a response.
I was just about to the point to write them off. If I can't get support before a purchase, what chance is there to get support after a purchase.
 
I received my BMS today, no documentation just the bms, balancer cable, and BT dongle. I sent an email on Monday asking about best way to configure a shunt and relay for a high power inverter and so far no response. Maybe they will reply to my question about the documentation.....
 
Bob B said:
@FilterGuy .... I'm glad you were able to get the information. I have sent 2 emails to sales@batteryhookup.com asking if the BMS could be configured on 2 seperate batteries in parallel ..... and have yet to get a response.
I was just about to the point to write them off. If I can't get support before a purchase, what chance is there to get support after a purchase.
Click to expand...


lmwilco1 said:
I received my BMS today, no documentation just the bms, balancer cable, and BT dongle. I sent an email on Monday asking about best way to configure a shunt and relay for a high power inverter and so far no response. Maybe they will reply to my question about the documentation.....
Click to expand...

I just called them. They answered right away and answered all my questions.

My guess is they have been swamped with emails since Will referenced them.

@Will Prowse: if you have any sway with them you might want to gently point out that answering emails is important.
 
lmwilco1 said:
I received my BMS today, no documentation just the bms, balancer cable, and BT dongle. I sent an email on Monday asking about best way to configure a shunt and relay for a high power inverter and so far no response. Maybe they will reply to my question about the documentation.....
Click to expand...
I just hook the inverter directly to the battery (fused for safety). It's not going to drain me down to an unsafe level anyway as inverters generally cut out around 11V automatically disconnecting the load.
 
I am working on video right now, but it should be dead simple to connect to bluetooth. its the only bms that I can connect instantly. Video being edited right now.
 
FilterGuy said:
I just called them. They answered right away and answered all my questions.

My guess is they have been swamped with emails since Will referenced them.

@Will Prowse: if you have any sway with them you might want to gently point out that answering emails is important.
Click to expand...
Wow thats a bummer. Yeah they are probably swamped. They are all busy 100% for the whole day usually. They are working on a FAQ and new website. Should be up in 10 days.
 
Will Prowse said:
I am working on video right now, but it should be dead simple to connect to bluetooth. its the only bms that I can connect instantly. Video being edited right now.
Click to expand...
Just a tip for the Bluetooth connection in case anyone has issues. You have to connect ALL the wires to the battery. I made the mistake of thinking it would work with just the balance wires but it doesn't you need to connect the B- wire as well. It will kind of work without B- connected but it will never complete the Bluetooth connection. After all the wires are connected it works perfectly.
 
Will Prowse said:
I am working on video right now, but it should be dead simple to connect to bluetooth. its the only bms that I can connect instantly. Video being edited right now.
Click to expand...
It would be great if your video will address how to connect the BMS and battery with a shunt and a 2000W inverter so that all of the charge/discharge current goes through the shunt. I am wondering if I connect the shunt to the battery neg terminal and BMS B- to the shunt load side if the voltage difference between the B- and the balance lead black wire dues to voltage drop across the shunt will casue any issue with the BMS.
 
lmwilco1 said:
It would be great if your video will address how to connect the BMS and battery with a shunt and a 2000W inverter so that all of the charge/discharge current goes through the shunt. I am wondering if I connect the shunt to the battery neg terminal and BMS B- to the shunt load side if the voltage difference between the B- and the balance lead black wire dues to voltage drop across the shunt will casue any issue with the BMS.
Click to expand...
I would not recommend that. A lot of the shunts are designed for 50mV (at max rated current). I would not want a possible .05 volt error in the BMS circuit. (Note: The BMS usually has a balance wire to the battery negative so the .05 volt *may* not matter, but why chance it?)
 
FilterGuy said:
I would not recommend that. A lot of the shunts are designed for 50mV (at max rated current). I would not want a possible .05 volt error in the BMS circuit. (Note: The BMS usually has a balance wire to the battery negative so the .05 volt *may* not matter, but why chance it?)
Click to expand...

Put the shunt before the BMS

1578682560081.png
 
lmwilco1 said:
In this diagram the inverter would have to connect to the battery terminal directly as the BMS does not support 200A. Then the shunt would not be able to measure the inverter power.
Click to expand...
Right, and personally I don't see any issue with putting the shunt between the BMS and the battery. I can't imagine a 50mV impact on the pack voltage making any difference at all. The BMS can still do its job of balancing and protecting from over/under charge/discharge.

Another thought would be to use a hall sensor rather than a shunt.
 
lmwilco1 said:
In this diagram the inverter would have to connect to the battery terminal directly as the BMS does not support 200A. Then the shunt would not be able to measure the inverter power.
Click to expand...

Yes, if you are not putting all current through the BMS, then you should put the shunt on the battery like this.

1578685093455.png
Please keep in mind that if you wire like this, the BMS can not control the over-voltage.


However you can change it to this (But if the BMS shuts down for under-voltage, you can not charge any longer.
1578685254251.png
 
atatistcheff said:
Right, and personally I don't see any issue with putting the shunt between the BMS and the battery. I can't imagine a 50mV impact on the pack voltage making any difference at all.
Click to expand...

You may be right. If the BMS does all it's voltage measurement through the ground balance wire, there should be no problem. However, if it is measuring the voltage at the main negative. I would think .05 volts could make a big difference. I typically want the cells to balance to well less than .05 volts difference and sticking a .05v error in would prevent that. I don't know where the BMS is measuring from so, like I said earlier, why take the chance.

(Yes, I sweat the details)
 
FilterGuy said:
You may be right. If the BMS does all it's voltage measurement through the ground balance wire, there should be no problem. However, if it is measuring the voltage at the main negative. I would think .05 volts could make a big difference. I typically want the cells to balance to well less than .05 volts difference and sticking a .05v error in would prevent that. I don't know where the BMS is measuring from so, like I said earlier, why take the chance.

(Yes, I sweat the details)
Click to expand...

Actually, this brings up an important question about the BMS. When it does a low-voltage shut-down, can it still take a charge current or do you have to reset it?
 
FilterGuy said:
Actually, this brings up an important question about the BMS. When it does a low-voltage shut-down, can it still take a charge current or do you have to reset it?
Click to expand...
I'm almost positive it shuts off all the power (in and out) during a LV cutoff. Mine is all connected with patch cables right now so I'm not in a position to test it. Plus my Chinese isn't what it used to be ;-)

I believe the cells would have to recover above the "Undervoltage release" value (3.0V by default) or this would have to be adjusted down to allow the charger to work.
 
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