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Feedback request Xuba battery build (HS senior project)

thisisnew

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Hi - I would really appreciate feedback. I’m a high school senior and have limited experience with electronics (i.e., I took AP Physics C - Electricity and Magnetism last semester). Due to Covid-19 we did not do many labs so I am hoping this project will take the place of the labs and more.

My relative has a remotely located camper and intends to build a shed/cabin. He was going to buy a generator but said he would provide me “funds” to put together a solar system for him to use. I have been lurking on this thread for months and watched many of Will’s posts and purchased an All-in-One 24 volt MPP system and will mount on a handtruck. I just received 8 3.2 volt Xuba batteries (280Ah). Looking back I probably should have ordered 1 or 2 spare fuel cells but too late for that.

Could someone read through my list and fill in any holes or add any steps I missed on the batteries? Thanks so much!!

1-I will first equalize all cells to the same charge then top balance them before I do a capacity test and recharge them. They arrived at 3.31 volts each and I have them all connected in parallel to begin to equalize; I’ve ordered a DC Power Supply which will arrive this week. Should I ensure each fuel cell is under pressure before I top balance it to avoid bulging?

2-I plan to use the double busbars and screws that were shipped with the package. I will also be sure to include copper washers and coat with no corrosion spray. How much torque should I use when I tighten the screws?

3-It looks like the Electrodacus BMS is the best/easiest? So I will wait and get one of those when available.

4-I read that I need to put the fuel cells in a box (with adequate ventilation) that is somewhat tight or under pressure so that the cells do not expand while charging. I will also buy a heater to ensure the cells do not get damaged if temp drops below freezing.

Does this fully cover the process? I will re-read some of the posts and re-watch some of the videos before I attempt but I believe these are the main things to keep in mind.

Thanks so much!
 
Tagging as you are a few steps ahead of me! We are doing the exact same build! I am in Indiana ... if you are close, I can order additional batteries for you to help on shipping if you still want them.
 
1-I will first equalize all cells to the same charge then top balance them before I do a capacity test and recharge them. They arrived at 3.31 volts each and I have them all connected in parallel to begin to equalize; I’ve ordered a DC Power Supply which will arrive this week. Should I ensure each fuel cell is under pressure before I top balance it to avoid bulging?
If you can charge them up as a parallel group to 3.5 volts would be best.

2-I plan to use the double busbars and screws that were shipped with the package. I will also be sure to include copper washers and coat with no corrosion spray. How much torque should I use when I tighten the screws?
Torque charts say 2 Nm but the terminal is aluminum. They don't have to be supper tight...

3-It looks like the Electrodacus BMS is the best/easiest? So I will wait and get one of those when available.
Get the biggest balancer you can. I have 17 280ah's you got and it took me 4 days at 2 amps to get them to balances to where they weren't over voltage with a 5 amp balancer. I didn't do what you plan in your item one above though.

In my experience they are balanced till you get to the full charged specs. Meaning, when they are under 3.4 volts they stay balanced but when you go above 3.4 they get out of balance very quickly....I was checking them all every 20 minutes when charging and still hit 4.5 to 5 volts on a couple cells a couple times.


4-I read that I need to put the fuel cells in a box (with adequate ventilation) that is somewhat tight or under pressure so that the cells do not expand while charging. I will also buy a heater to ensure the cells do not get damaged if temp drops below freezing.
It is best to make sure they don't go over voltage (3.65 volts) and they shouldn't expand.

Does this fully cover the process? I will re-read some of the posts and re-watch some of the videos before I attempt but I believe these are the main things to keep in mind.

Thanks so much!
[/QUOTE]
 
Tagging as you are a few steps ahead of me! We are doing the exact same build! I am in Indiana ... if you are close, I can order additional batteries for you to help on shipping if you still want them.
I really appreciate the offer. When do you plan to place an order? I am in NC which is not terribly far.
 
1-I will first equalize all cells to the same charge then top balance them before I do a capacity test and recharge them. They arrived at 3.31 volts each and I have them all connected in parallel to begin to equalize; I’ve ordered a DC Power Supply which will arrive this week. Should I ensure each fuel cell is under pressure before I top balance it to avoid bulging?
If you can charge them up as a parallel group to 3.5 volts would be best.

2-I plan to use the double busbars and screws that were shipped with the package. I will also be sure to include copper washers and coat with no corrosion spray. How much torque should I use when I tighten the screws?
Torque charts say 2 Nm but the terminal is aluminum. They don't have to be supper tight...

3-It looks like the Electrodacus BMS is the best/easiest? So I will wait and get one of those when available.
Get the biggest balancer you can. I have 17 280ah's you got and it took me 4 days at 2 amps to get them to balances to where they weren't over voltage with a 5 amp balancer. I didn't do what you plan in your item one above though.

In my experience they are balanced till you get to the full charged specs. Meaning, when they are under 3.4 volts they stay balanced but when you go above 3.4 they get out of balance very quickly....I was checking them all every 20 minutes when charging and still hit 4.5 to 5 volts on a couple cells a couple times.


4-I read that I need to put the fuel cells in a box (with adequate ventilation) that is somewhat tight or under pressure so that the cells do not expand while charging. I will also buy a heater to ensure the cells do not get damaged if temp drops below freezing.
It is best to make sure they don't go over voltage (3.65 volts) and they shouldn't expand.

Does this fully cover the process? I will re-read some of the posts and re-watch some of the videos before I attempt but I believe these are the main things to keep in mind.

Thanks so much!
[/QUOTE]


Thanks very much. I will charge them all as you suggest. I still plan to build some sort of box to put them in so I will try to get them "snug".

Did you not do a capacity test on your cells?
 
I am still working to get them all to the same voltage at the full charged state. I have them at the same voltage up to 3.4 volts per cell, once I go above that they are spreading apart. At 3.5 volts charge state average I have a spread of .100 volts.

I have a Victron BVM 700 and can do capacity, just haven't yet.
 
I really appreciate the offer. When do you plan to place an order? I am in NC which is not terribly far.

I hope to do so today. Else I will fuss and such about it. NC will be extra shipping. if I was racing hard, I would be heading down there in a couple of months. But with all the fun this year, not much off-road triathlons happening. Probably not worth the effort.
 
The batteries should not bulge at all while parallel top balancing as long as you don't overcharge because you will be charging with a low current compared to the capacity of the cell. And they should be charged fully to 3.65 volts for a proper top balance.

The cells do not need to be compressed but should be mounted in a box that fits them to prevent bulging. There are other ways and I am sure you have noticed other suggestions since you have been following the forum for awhile.

The cells do not require ventilation per se unless charging at high charge and discharge currents. I have seen many builds of drop in batteries using prismatic cells and they are sealed.

Best of luck with your build. I am hoping to have 8 of these same cells on the way shortly. The fun has already started planning for this, that, and the other thing...lol
 
The batteries should not bulge at all while parallel top balancing as long as you don't overcharge because you will be charging with a low current compared to the capacity of the cell. And they should be charged fully to 3.65 volts for a proper top balance.

The cells do not need to be compressed but should be mounted in a box that fits them to prevent bulging. There are other ways and I am sure you have noticed other suggestions since you have been following the forum for awhile.

The cells do not require ventilation per se unless charging at high charge and discharge currents. I have seen many builds of drop in batteries using prismatic cells and they are sealed.

Best of luck with your build. I am hoping to have 8 of these same cells on the way shortly. The fun has already started planning for this, that, and the other thing...lol

Thanks, I started thinking about charging to 3.5v and I can understand that would be prudent but it seems like I would not get an accurate capacity reading if I did that?

Another issue I just thought about is that we purchased 4 100watt Windy Nation Solar Panels, I think they are 22 volts. I wanted to get more solar panels and there is a person nearby selling 270 watt panels ($100 each) that are around 44 volts each. Can I have 2 sets of 2 Windy Nation Panels in series and then have those two sets wired in parallel to three of the other panels that are also in parallel? That should still be under the capacity of the MPP Hybrid Inverter:

MPPT Max. PV Array Open Circuit Voltage 145Vdc
PV Array MPPT Voltage Range 30~80Vdc

I guess not ideal as the WN are new and these I hope to purchase are not...but seems like it should work, right? I think there was a section in Will's book, I will try to go back and find it, but just thought I would ask.
 
Thanks, I started thinking about charging to 3.5v and I can understand that would be prudent but it seems like I would not get an accurate capacity reading if I did that?

Actually the cells are pretty full at that point. However the spec sheets say 3.65 is fully charged. And that's the voltage most are parallel top balancing to. Once you connect them in series charging to 3.5 volts per cell will be fine. Some do a little less, some a little more. But yeah to check the capacity I would want to fully charge.

Sorry I can't help you with solar. Not there yet.
 
Actually the cells are pretty full at that point. However the spec sheets say 3.65 is fully charged. And that's the voltage most are parallel top balancing to. Once you connect them in series charging to 3.5 volts per cell will be fine. Some do a little less, some a little more. But yeah to check the capacity I would want to fully charge.

Sorry I can't help you with solar. Not there yet.

I agree, I have a 17 cell 280ah pack I am trying to get all the cell voltages the same. At 3.5 volts I am close to having them with in .020 volts of each other right after charging to 3.5 volts, but when I try to get to 3.65 I have a couple cells get close to 4 volts which is not a good situation.

This is with a 5 amp active balancer on them that appears to be working really good because I can see it bring the voltages to within a couple thousandth on all the cells at the 3.5 volt level the next morning after charging.

Going to keep cycling them each day and see how they respond. I ran it down by 100 ah yesterday and am now charging them at 5 amps. Will see how close they are tonight.
 
In order to balance the cells you have to connect them in parallel and use a variable power supply set to 3.65V. Depending on the state of charge of your batteries it may take a long time to get to 3.65V but just wait. If you do this you can't get any cells above 3.65V and they will be balanced. Do some reading on the forum and you will fins several examples of people who tried to balance using some other method and destroyed one or more cells. The cost of the power supply is $63 on Amazon and it is cheap insurance.
 
This one arrives later today:

DC Power Supply Variable 30V 10A, 4-Digital LED Display, Precision Adjustable Switching Regulated Multifunctional Power Supply Digital with USB Interface, Disply with Output Power Lab Grade

This is one that I linked to off of Will's video. I feel reasonably comfortable with that process (after being a bit uncertain initially re how high to charge, but now feel ok about it) but the capacity test seems a bit more sketchy, but one step at a time.
 
another question:

I hooked up a DC motor to my mom's bike and bike stand and it seems to be generating electricity pretty well. It seems I have a bad battery though as it starts at 12 volts, then charges while I pedal but immediately drains down to 12 again. Any ideas on a cheap battery that I could use for this purpose? Ideally I will charge the battery up and hook up to feed the DC lights on a camper and use the bike to recharge when it drains down.

I also tried to run the voltage through a solar charge controller ( Steca PR 1515 - it said solar only but I thought it was worth trying to experiment ) but it puts too heavy of a load and I cannot pedal the wheels. Any ideas on how I could use the charge controller or I just need to be careful not to overcharge whichever battery I attach to it?

Thanks...
 
Do you have a BMS protecting the battery cells? Until you top balance the cells and assembly your battery with a BMS I would be very careful charging or discharging it.
 
I am in NC.

We have not bought the BMS yet. I tend to try to do exactly what Will's video shows since I have only a basic understanding and zero experience. He used the Electrodacus BMS so I was waiting for that one to come available. School starts back in a few weeks though so I was thinking of getting the Overkill BMS so I could get things together before then. My relative is not pushing me on this but I feel kind of bad that it is taking so long.

So you do not recommend doing anything until the BMS is attached? From watching Will's video it seemed I could do a capacity test on an individual fuel cell without a BMS.
 
This one arrives later today:

DC Power Supply Variable 30V 10A, 4-Digital LED Display, Precision Adjustable Switching Regulated Multifunctional Power Supply Digital with USB Interface, Disply with Output Power Lab Grade

This is one that I linked to off of Will's video. I feel reasonably comfortable with that process (after being a bit uncertain initially re how high to charge, but now feel ok about it) but the capacity test seems a bit more sketchy, but one step at a time.
Thanks for the great information.

I have this one already. I currently have it on (2) 100 ah cells and it has been 5 days and they aren't close to charged.

With (17) 280 ah cells I think it will take a month......but great process....I agree with you.
 
I am in NC.

We have not bought the BMS yet. I tend to try to do exactly what Will's video shows since I have only a basic understanding and zero experience. He used the Electrodacus BMS so I was waiting for that one to come available. School starts back in a few weeks though so I was thinking of getting the Overkill BMS so I could get things together before then. My relative is not pushing me on this but I feel kind of bad that it is taking so long.

So you do not recommend doing anything until the BMS is attached? From watching Will's video it seemed I could do a capacity test on an individual fuel cell without a BMS.
Go big or Go home.....
 
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