Bigbattery 24v HWK not powering on?

[Coil]

I posted about this under All in Ones but I'm now leaning towards it being a battery issue.


My LV2424 Hybrid is connected to a 24v bigbattery HWK and a wall outlet with grid feedback disabled. The low voltage cutoff was set to 23.5V and the " battery stop discharging when grid is available" setting was set to 24v. Solar was set to be the only charging source for the battery so as to not waste power cycling grid power through the battery. The goal hear was to use up all the solar power generated by directing it to the loads first and then to the battery and using the grid when those were insufficient.

I had about 500 watts of consistent load connected to it (just a router and a small server) so definitely not pushing any limits.

This morning I found the whole system turned off. The loads appear to have gone offline around 4 AM. When I went to bed the LED panel on the LV2424 suggested the loads were running off AC power only and the voltage was around 24v which is what I would have expected at that time.

The LED voltage readout on the bigbattery is off (despite the power button being in the on position) but a volt meter across the disconnected battery contacts reads 23.5v so it's not so dead as that.

While the LV2424 is not powering on at all despite being connected to both PV and AC input my volt meter reads 26.1 across the battery lugs when the AC is disconnected and 27 When the AC is connected.

This behavior makes me think something internal to the battery has failed in some way although that's a very middling voltage so I can't think of what.

Update: bigbattery support confirmed that this was unusual behavior. They walked me through "resetting the BMS" by removing the top cover and unplugging it for 30 seconds. It still doesn't power on but now when I test the voltage it reads 1.735v (???). I have no idea what is going on with this thing.

 

[Diesel Pro]

Follow up?

 

[McRod]

The battery died. Take it off line and put a charger on it.

I have had this happen several times on mine. Even though I set a LBCO on my inverter to 22.4.

I have to completely disconnect any power source, turn off the batteries, then turn batteries back on and add a charging source. They come back to life and charge back up.

 

[Coil]

Yeah, it's definitely a bad BMS and not a dead battery. When I measure voltage across the cells themselves they read ~23 volts. Only when I include the BMS in the loop do I get an odd 1.7v reading.

Bigbattery support has been absolutely abysmal. I can't even get them to respond to email. Their "warranty" is not worth the paper it's printed on. I would strongly suggest avoiding them.

 

[Coil]

I may have been a bit hard on them. I'm going to charge it and that will probably be fine.


Customer Service 15:21
Hello. How may I help you?
Me 15:22
Hi, I've been emailing about a dead battery for a couple months and I've stopped getting response. What's the deal?
Customer Service 15:24
Hi Timothy, let me go take a olook at your email. We have been very short staffed lately so it's taking much longer trying to get to some of these emails
Me 15:24
I understand completely
Customer Service 15:31
So the battery reads 23.5V still, correct? It looks like we've already done a BMS reset. Are you using an ac charger for this or are you using a charge controller?
Me 15:32
I'm using a charge controller. The battery contacts read 1.7 volts. I only read 23 volts if I read across the cells directly
Customer Service 15:34
Alright, so my first thought is that the battery is just dead, do you have an ac charger you can use to get the battery back on?
Me 15:35
I don't... but how would it be dead if it's reading 23 volts?
Customer Service 15:35
Even if it's just one that you can borrow from a friend, you would just need it to turn the battery back on
So for tyhis battery, 25.4V is 10% of the battery life remaining, so it's not uncommon to have the battery die anywhere below that
Me 15:35
I see
That's lower than I though
*thought
Customer Service 15:36
I would recommend setting your charge controller to 25.4V so that it doesn't fall below that point, but for now, you would just need to wake the battery back up
Yeah, lithium works as a curved graph rather than a linear graph which makes it difficult to tell when the battery is low
Me 15:37
That makes sense. Can you hang on for a second while I look up one other thing?
Customer Service 15:37
Sure
Me 15:38
On the spec sheet for the 24V HWK at https://bigbattery.com/products/24v-hawk/
It lists 23 volts as the low voltage cut off for best cycle life
Is that just not accurate for this model?
That's really the main thing that's caused me confusion
Customer Service 15:40
That is correct, we did a lot of testing on our batteries to get the right measurements for the batteries and we need to update some of our spec sheets but we're so short handed right now that it's talking longer than we would like it to
Me 15:41
That's fine. I get it, I just wanted to clear that up for myself. Thanks for walking me through it.
Customer Service 15:41
Of course, sorry again for the delayed response
Me 15:42
No I understand. It's difficult right now.
You have a good one.
Read
Customer Service 15:42
You as well

 

[McRod]

Yeah, it's definitely a bad BMS and not a dead battery. When I measure voltage across the cells themselves they read ~23 volts. Only when I include the BMS in the loop do I get an odd 1.7v reading.

Bigbattery support has been absolutely abysmal. I can't even get them to respond to email. Their "warranty" is not worth the paper it's printed on. I would strongly suggest avoiding them.

Curious,. Have you considered just replacing the BMS with one of the ones Will promotes here on his website?

I was noticing that the BMS's don't play nice with each other when in series, so I was considering something like that.

 

[Coil]

Curious,. Have you considered just replacing the BMS with one of the ones Will promotes here on his website?

I was noticing that the BMS's don't play nice with each other when in series, so I was considering something like that.

That was going to be my ultimate solution if nothing else worked. It just would have sucked to pay the premium for a pre-built battery and end up with a DIY one.

 

[McRod]

They still have one of my batteries for 3 weeks, can't get in touch with anyone. Probably at lunch, I'll call this afternoon.

Problem with their mislabeled spec sheets is that their Tech Support (which is also sales dept) will swear by them until they are proven otherwise.

They told me to set my LBCO to 22v. I have it at 22.4. looks like I need to raise it up more.

 

[Coil]

I only waited in their chat for about 5 minutes before they answered. Maybe give that a try.

 

[McRod]

That was going to be my ultimate solution if nothing else worked. It just would have sucked to pay the premium for a pre-built battery and end up with a DIY one.

I totally agree. But looks like most of us who have problems with these are going to have to just ignore the warranty and fix them ourselves.

Like you said, it's not worth the paper it's printed on.

On the bright side, they are easy to work on and look better than a milk crate!

 

[McRod]

I only waited in their chat for about 5 minutes before they answered. Maybe give that a try.

I can't do chat with them anymore. Did that when I was having problems and can't communicate effectively like that. By the time they respond I forget what I was going to say or ask. Then I call, finally get someone live in "sales" and it's the same dude I was talking to in chat....mother@#$_&-!!

I about pulled my hair out...what's left of it.,?

 

[pproducts]

Yeah, it's definitely a bad BMS and not a dead battery. When I measure voltage across the cells themselves they read ~23 volts. Only when I include the BMS in the loop do I get an odd 1.7v reading.

Bigbattery support has been absolutely abysmal. I can't even get them to respond to email. Their "warranty" is not worth the paper it's printed on. I would strongly suggest avoiding them.

You will need to put it on a battery charger to wake it back up.
If it doesn't come back on you will need to send it back in for warranty or repair it yourself.
You need to fully charge it again and see what voltage it actually shuts down. If you have a bad cell or 1 that is out of balance it will shut the battery off at a higher voltage than expected. I have 8 of the hawks and had some with similar problems as yours. I got tired of sending them back and starting fixing them my self.

 

[Coil]

You will need to put it on a battery charger to wake it back up.
If it doesn't come back on you will need to send it back in for warranty or repair it yourself.
You need to fully charge it again and see what voltage it actually shuts down. If you have a bad cell or 1 that is out of balance it will shut the battery off at a higher voltage than expected. I have 8 of the hawks and had some with similar problems as yours. I got tired of sending them back and starting fixing them my self.

That's very helpful. I'm pretty sure it's just a matter of the whole unit having discharged too low. The difference between the highest and lowest cell is only .039 volts. I'll test again once it's charged though to be sure.

I still don't really understand why the low voltage cut off would be so much different for these batteries. I thought it was dictated by the battery chemistry and therefore pretty universal.

 

[labeeman]

That's very helpful. I'm pretty sure it's just a matter of the whole unit having discharged too low. The difference between the highest and lowest cell is only .039 volts. I'll test again once it's charged though to be sure.

I still don't really understand why the low voltage cut off would be so much different for these batteries. I thought it was dictated by the battery chemistry and therefore pretty universal.

Battery chemistry determines what the battery is discharged to and it is NOT universal. How the BMS is set up is what the cutoff is if you have a cell that is lower than the others while discharging you will reverse charge that cell which will permanently destroy it the BMS will cut off the discharging so as not to damage the cells. You will need to set up your discharging device to cut off before the BMS does it for you.

 

[pproducts]

That's very helpful. I'm pretty sure it's just a matter of the whole unit having discharged too low. The difference between the highest and lowest cell is only .039 volts. I'll test again once it's charged though to be sure.

I still don't really understand why the low voltage cut off would be so much different for these batteries. I thought it was dictated by the battery chemistry and therefore pretty universal.

>I had about 500 watts of consistent load connected to it (just a router and a small server) so definitely not pushing any limits.
500 watts per hour plus inverter usage of about 60-65 watts per hour = 565 watts
So If your making it until 4:00 am your doing pretty good.
Here are my inverter settings for a growatt:
1 to SBU
14 to CSO
12 to 24v switch to grid
13 to 25.5v turn off grid
21 to 23.5v low voltage cutoff

It will only use grid when necessary and only start charging the battery's when they drop to about 10% and only charge them up to about 20% and stop. Then it will repeat as needed.

So long as your battery is in balance you can pretty much setup it up and forget about it.
I personally don't like taking them below 24v(10%).

 

[niktak11]

My HSKY did the same thing when I had my inverter LVD set to 44V. It appears that 1 cell hit the BMS LVD. Hooking it up a charger was not enough to get the BMS to turn back on. I had to bypass the bms and charge it up to a bit past 48V first, then hooking it up to a charger (across the BMS) finally got it to turn back on. I bumped my inverter LVD to 47V now and it has been fine since then.

 

[Coil]

My HSKY did the same thing when I had my inverter LVD set to 44V. It appears that 1 cell hit the BMS LVD. Hooking it up a charger was not enough to get the BMS to turn back on. I had to bypass the bms and charge it up to a bit past 48V first, then hooking it up to a charger (across the BMS) finally got it to turn back on. I bumped my inverter LVD to 47V now and it has been fine since then.

Battery charger comes in today so hopefully that resolves it. I was wondering if I would need to hook it up directly to the battery and bypass the BMS to charge it. Sounds like that is in fact the case until the BMS comes back to life.

 

[niktak11]

Battery charger comes in today so hopefully that resolves it. I was wondering if I would need to hook it up directly to the battery and bypass the BMS to charge it. Sounds like that is in fact the case until the BMS comes back to life.

Report back if it works. The guy I chatted with from support was convinced that their charger would turn it back on but I wasn't patient enough to wait for it to get delivered.

 

[Coil]

Disclaimer: Do not do what I did unless you know what you're doing. I'm not sure it was a wise idea.

So all I had was a little 5 amp smart charger that I bought on amazon for $30. This wouldn't charge my battery via the anderson connector but since the "smart" charger couldn't detect voltage through the sleeping BMS it woudn't start charging so I hooked the charge directly to the cells and checked the voltage of each individual cell every little while to make sure nothing was getting out of balance.

Problem is that the BMS still wasn't "awake" even after I got up to around 25.5 volts. Apparently in order to "wake" it needs that voltage to come from outside. Sooooooo, i just tapped the anderson connector cables to the cells directly and it popped right awake and displayed the 25.5v reading from the cells. Like I said before, there may be good reasons for not doing that.

 

[niktak11]

Disclaimer: Do not do what I did unless you know what you're doing. I'm not sure it was a wise idea.

So all I had was a little 5 amp smart charger that I bought on amazon for $30. This wouldn't charge my battery via the anderson connector but since the "smart" charger couldn't detect voltage through the sleeping BMS it woudn't start charging so I hooked the charge directly to the cells and checked the voltage of each individual cell every little while to make sure nothing was getting out of balance.

Problem is that the BMS still wasn't "awake" even after I got up to around 25.5 volts. Apparently in order to "wake" it needs that voltage to come from outside. Sooooooo, i just tapped the anderson connector cables to the cells directly and it popped right awake and displayed the 25.5v reading from the cells. Like I said before, there may be good reasons for not doing that.

This is what I had to do also. Charge the cells directly above 48V then connect charge voltage across the leads that go through the BMS. Do other BMSs work this way? This is my first time hitting a single cell LVD with any BMS.