Big Battery 24v 170ah hawk problems

pproducts

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May 17, 2021
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Hi guys

After talking to Billy today over at Big Battery and finding out that they would not provide/sell me replacement parts for one of my battery's, I need to find another source.

I have purchased 8 of the 24v hawks over the last few months and need to get some replacement cells since Big Battery will not provide/sell them and need to find a good replacement for them. I thought it would be cheaper just to buy the cells rather than pay for shipping every time the battery needs service. This is the second battery that you could not charge properly(the first one was replaced under warranty). I could scrap one of the battery's and use it for parts but since it was $1500 I am trying to avoid that.

Big Battery's warranty seems to be pretty good but they seem to be having some quality control problems. They replaced 4 of the battery's because of small problems like the handle screw was stripped out, missing screws on the case, missing QC stickers, i had 2 or 3 that wouldn't turn on when I received them and had to put them on a charger to wake them up, etc. I think I probably got a batch that did not go through QC.

The problem I am currently having is 2 of the cells are at 3.29v and 3.16 volts when the battery is fully charged. The rest of the cells are around 3.52.
I have attached a picture for you too look at, let me know if you think it may be causing the problem. It looks like they used too small of washers on the studs and they are not contacting the board very well. Some of the studs look like they are bent because of the wrong size washer and some look like you could pull the board off without removing the nuts. If you think this is causing the problem I will need to purchase some washers and check all 8 of the battery's and repair as needed.

Thanks for your assistance.
 

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snoobler

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Poor connections can cause balance issues.

If the low voltage numbers are reported by the BMS, confirm with separate meter.

If you think there's a connection problem, it's definitely worth fixing.

Personally, I would attempt to charge the two low cells individually with a suitable power supply to bring them up to a voltage consistent with their packmates.
 

pproducts

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Poor connections can cause balance issues.

If the low voltage numbers are reported by the BMS, confirm with separate meter.

If you think there's a connection problem, it's definitely worth fixing.

Personally, I would attempt to charge the two low cells individually with a suitable power supply to bring them up to a voltage consistent with their packmates.
Hi, thank you for your response

I currently only have a 24v charger, what would you recommend to charge the cells with individually.
Also what type of washers should I purchase?
Going buy the color I would think these are brass.
 

snoobler

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There are relatively inexpensive 30V/10A power supplies on Amazon. Will lists one on this page:


ANY washer of a suitable size and a conductive material is likely better than something that's way too small. I'm assuming the conductive face of the circuit board is being clamped down onto the terminal. If that's the case, then it doesn't matter what you use because the two faces in contact are where most of the conductivity will be. Even a big stainless washer will provide better continuity than that brass washer simply clamping on the corner.
 

pproducts

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Thanks for your help.

I ordered the power supply from Will's site and will try to charge the 2 cells like you recommended first.
If I have to replace the 2 cells will any 170 amp cells work ok?
 

snoobler

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Thanks for your help.

I ordered the power supply from Will's site and will try to charge the 2 cells like you recommended first.
If I have to replace the 2 cells will any 170 amp cells work ok?

I would attempt to source the exact same cells where possible.
 

pproducts

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Will mentions in one of his video's that they are lishen cells. It doesn't look like there are a lot of choices for 170ah cells.
Big Battery really needs to sell replacement parts for these battery's.
I bought these because they were supposed to be serviceable. I would never had guessed Big Battery wouldn't sell replacement parts.
You would think if someone is willing to pay for parts and save them the cost of doing a warranty they would be happy to do it.
They will probably loose me as a customer over this.
 

Q-Dog

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Is the cap in that first picture melting? Heat is a good indicator of a poor connection. I would get some big washers and see if that fixes the problem before spending money on new cells.
 

ereams65

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If you check the voltage with a meter and get a different, normal reading, then the washer/post is the problem. However, if the meter is close to what the BMS is saying, then it's not a connection issue.
 

pproducts

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Is the cap in that first picture melting? Heat is a good indicator of a poor connection. I would get some big washers and see if that fixes the problem before spending money on new cells.
Hi

I added big washers to all the cells but I did not think to check the temp's first. That would have been a good idea to check first.
 

pproducts

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If you check the voltage with a meter and get a different, normal reading, then the washer/post is the problem. However, if the meter is close to what the BMS is saying, then it's not a connection issue.
Hi

I might not be understanding correctly. I can check the readings of the cells but the BMS does not have a software interface. Is there some other way to check what the BMS is reading?
 

pproducts

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This whole thing sounds like another defective product reason to avoid BB. 🤔
Hi

They have been having some problems but I really have been ok with them. They have been nice on the phone and good to work with.
If they would just sell me some parts and help diagnose the problems instead of having to spend money on shipping I would be happy.
 

MrNatural22

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Hi

They have been having some problems but I really have been ok with them. They have been nice on the phone and good to work with.
If they would just sell me some parts and help diagnose the problems instead of having to spend money on shipping I would be happy.
That's what "good customer service" is supposed to be defined as. ALL defective hawk batteries you received should have been replaced. Nice offer to do their repair job for them but they sold you faulty batteries.
 

ereams65

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Hi

I might not be understanding correctly. I can check the readings of the cells but the BMS does not have a software interface. Is there some other way to check what the BMS is reading?
I didn’t realize you couldn’t connect to the BMS and thought that’s where you go your voltage.
 

pproducts

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That's what "good customer service" is supposed to be defined as. ALL defective hawk batteries you received should have been replaced. Nice offer to do their repair job for them but they sold you faulty batteries.
Hi

They will fix it if I ship it back. They also said I can dispute the shipping charges if it is there fault.
But the only way you can prove it's their fault is to open it up to find the problem. Since they have a sticker that says it will void the warranty if you open it they can easily say you caused the problem or just not honor the warranty at all.

Also I would actually like at some point to start using the battery's so I though it would be easier just to repair this one my self.
 

pproducts

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I didn’t realize you couldn’t connect to the BMS and thought that’s where you go your voltage.
Hi

Its really a bad design. You can't even tell the battery is working after you plug it in with the rest of the pack.
The battery can be turned off but it will show the pack voltage and the power light will be on so you thing everything is ok.
This one has probably been bad since I received it. The only way I found out it was defective was when I was checking the amps on the cables.
 

pproducts

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Thanks for the help everyone.

I put washers on all of the studs and charged the 2 cells up to match the rest and it seems to be working ok now. I did a 90 percent discharge and the voltage on the cells were still pretty close together.
 

pproducts

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Hi

I started having problems with another one and found 1 loose nut and 2 that look like the washers were going to pull through the board.
I added the correct size washers and balanced the cells out. The torque specs on the nuts were all over the place probable because they didn't use the correct washers.

Anybody that has purchased these in the last 3 or 4 months may want to check them out. All of the tear down videos I have seen on youtube they were using the correct size washers so this must be a more recent problem.
 

Just John

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If you weren't already aware, you probably need to read this thread.

 
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