BMS suggestions for 48v Battle Born and MPP all in one.

[Daley]

Hi,

My set up has been working fine so my head has been out of solar world but I had an issue and am looking for some advice.

I have 4 100ah Battleborn batteries in series for 48v running to a 48v mpp all in one.
I also have a bus bar coming off the battery bank feeding 3 12v/24v dc dc inverters for my 12v/24v circuits.

Everything has been fine all summer long but we had a cloudy day or two and my system died, one of the batteries was at 10.5v and the others were at 12.5v.

I am charging the batteries via mains right now but was hoping someone might help me answer a few questions.

1) Is there such a thing as a battery balancer to prevent one battery going lower than the others?

2) Is there a recommended BMS that would work with my set up that allows me to set the low voltage and see what each batteries state of charge is?

3) Is there a safer way to run the 12v circuits that is protected?
the 12v circuits are not running through the mpp so I fear they may deplete batteries before/after the mpp has had chance to act.

4) Slightly off topic but is there a gauge/monitor that enables you to see the solar output re

 

[snoobler]

0) https://www.solar-electric.com/lib/wind-sun/Battle_Born_Manual.pdf

"Maintenance Battle Born Batteries require very little maintenance if any at all. If your batteries are in series and not being charged by a multi-bank charger it is recommended that you fully charge the batteries individually once a year. This will balance out the entire battery bank to ensure the batteries will reach its expected life span. If your batteries are in parallel this is not necessary. Our BMS has a built in passive balancing system that will take care of this for you. "

You should probably re-read that entire manual and maybe top balance them in parallel after the series charge.

Also 12.5V (3.125V/cell) resting after a load is likely very nearly empty as well as the 10.5V (2.625V/cell). This may be a complete non-issue.

1) yes

2) unknown

3) You need to adjust your MPP low voltage cut-off upwards.

4) I don't think you finished this question.

1. Did you notify Battleborn at the time of purchase that these were intended for a 48V series bank?
2. What are your 4 voltages when the batteries are fully charged?

 

[Daley]

Hi there,

Thanks for the input.
Do you have any suggestions for a good battery balancer?

If my 12v circuits are being supplied direct from the battery bank what use will adjusting settings on the mpp do? As far as I can tell there is no way to run 12v directly from or through the mpp. The only way I see that might be possible is to go to 12v from 120v via the mpp inverter.
I think this is an overlooked problem when using mpp, sure you can prevent low batteries from loads running through the mpps inverter but what about when running 12/24v circuits?

Please let me know if I am wrong?

I haven’t fully charged the batteries yet so cannot give the individual voltages.

I didn’t tell Battleborn they were to be used for 48v I figured mounting in series would be a common use.

My question that never completed was, is there a monitor/gauge that can give real-time readings in wattage that the solar array is Producing? I have 8 180w panels mounted in two banks of 4 so the voltage is pretty high. I haven’t seen a monitor that can go over 100v.

 

[snoobler]

Hi there,

Thanks for the input.
(1) Do you have any suggestions for a good battery balancer?

(2) If my 12v circuits are being supplied direct from the battery bank what use will adjusting settings on the mpp do? As far as I can tell there is no way to run 12v directly from or through the mpp. The only way I see that might be possible is to go to 12v from 120v via the mpp inverter.
I think this is an overlooked problem when using mpp, sure you can prevent low batteries from loads running through the mpps inverter but what about when running 12/24v circuits?

Please let me know if I am wrong?

I haven’t fully charged the batteries yet so cannot give the individual voltages.

(3) I didn’t tell Battleborn they were to be used for 48v I figured mounting in series would be a common use.

(4) My question that never completed was, is there a monitor/gauge that can give real-time readings in wattage that the solar array is Producing? I have 8 180w panels mounted in two banks of 4 so the voltage is pretty high. I haven’t seen a monitor that can go over 100v.

(1) Did you click the link in item 1?
(2) Sorry. I meant to say inverter low-voltage cut-off.

(3) from https://battlebornbatteries.com/faq/



(4) Many charge controllers provide this information. Understand that the incoming power from the panels equals the output power to the batteries.

 

[dRdoS7]

HI,

1) Is there such a thing as a battery balancer to prevent one battery going lower than the others?

Victron make them, you would need 3 for a 48V system.

Battery Balancer - Victron Energy

Equalize the state of charge of two series connected 12V batteries using the Battery Balancer. Find a Victron Energy dealer near you.

www.victronenergy.com

Has an alarm output that could be used to operate a disconnect.

https://www.victronenergy.com/upload/documents/Datasheet-Battery-Balancer-EN.pdf

You could devise your own with voltage controllers, and AC-DC chargers. They wouldn't need to be too big, just enough to balance a battery if needed. Probably run the system on a timer, so it's not being used all the time. The MPP would do most of the charging.

3) Is there a safer way to run the 12v circuits that is protected?
the 12v circuits are not running through the mpp so I fear they may deplete batteries before/after the mpp has had chance to act.

Yes, use a 12V power supply running off the inverter AC.

My question that never completed was, is there a monitor/gauge that can give real-time readings in wattage that the solar array is Producing? I have 8 180w panels mounted in two banks of 4 so the voltage is pretty high. I haven’t seen a monitor that can go over 100v.

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Disregard the battery capacity section, it will probably be OK for your panels. Not too expensive. Can see it on your phone.

I've bought one, but don't have it yet, so can't tell how good it is.

dRdoS7

 

[HRTKD]

I'm not a fan of series connecting individual batteries that have their own BMS. This is mainly due to not understanding how the BMS will react.

Assume two 12v batteries in series. The first battery achieves full charge state before the second battery does. Does the first battery allow charge current to continue to the second battery? If so, how? That's the part I don't understand. How would it allow power to flow through?

 

[snoobler]

I'm not a fan of series connecting individual batteries that have their own BMS. This is mainly due to not understanding how the BMS will react.

Assume two 12v batteries in series. The first battery achieves full charge state before the second battery does. Does the first battery allow charge current to continue to the second battery? If so, how? That's the part I don't understand. How would it allow power to flow through?

No. It does not permit that, but each battery keeps its cells balanced.

Given that Battleborn indicates it's okay, and it's done routinely, is it really an issue? Beyond their recommendation of doing an annual parallel balance charge, there's no downside. The OP's situation could have possibly been avoided had he notified BB of the need for series connections. He likely got random batteries from stock with a possible 10% deviation in capacity.

As I linked above, https://www.electriccarpartscompany.com/Lithium-Lead-Acid-Battery-Balancers-Equalizers-12V, these would keep each 12V in balance with all other 12V batteries in series thus eliminating the need for an annual parallel charge.

There is a still a small tendency for "natural" top balancing of LFP as there is with Pb cells. Higher SoC has reduced Coulombic efficiency, so if there is a disparity between the string components, the lesser charged batteries will take on slightly more charge than the fuller batteries for a given current. This effect is small, but it can compensate for small capacity differences.

 

[GXMnow]

Here is a cheap balancer that can move around some power to balance 4 series connected 12 volt batteries. I do not have one myself, so I can't say how good it is, but the tech behind it is a solid design.

Amazon.com: KRXNY Battery Equalizer 48V Max 4 X 12V Batteries Voltage Balancer Charger for Gel Flood AGM Lead Acid Lithium Battery Bank Extend : Automotive

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[snoobler]

FWIW, I have 8 of the units I recommended for 12V and 16 of them for NMC cell balancing. I have actually used them. I can attest to their function.

 

[Daley]

I just wanted to follow up, I individually charged the batteries and equalized them before putting back into series.

I bought one of these as recommended above.

Amazon.com: KRXNY Battery Equalizer 48V Max 4 X 12V Batteries Voltage Balancer Charger for Gel Flood AGM Lead Acid Lithium Battery Bank Extend : Automotive

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It seems to be working great at balancing, all 4 batteries are at 13.61v

The device does make a high frequency noise though, any ideas on that or has anyone else got one of these that can comment?

 

[John Frum]

I just wanted to follow up, I individually charged the batteries and equalized them before putting back into series.

I bought one of these as recommended above.

Amazon.com: KRXNY Battery Equalizer 48V Max 4 X 12V Batteries Voltage Balancer Charger for Gel Flood AGM Lead Acid Lithium Battery Bank Extend : Automotive

Buy KRXNY Battery Equalizer 48V Max 4 X 12V Batteries Voltage Balancer Charger for Gel Flood AGM Lead Acid Lithium Battery Bank Extend: Battery Chargers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

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It seems to be working great at balancing, all 4 batteries are at 13.61v

The device does make a high frequency noise though, any ideas on that or has anyone else got one of these that can comment?

Did you determine that the balancer was actually necessary?

 

[Daley]

I believe so, when I had the batteries in series 2 were at a lower voltage than the other 2. It was the two that had connections going to the mpp that were lower.

 

[John Frum]

I believe so, when I had the batteries in series 2 were at a lower voltage than the other 2. It was the two that had connections going to the mpp that were lower.

You mean the the outer batteries as opposed to the inner batteries?
Did you first try just paralleling them?

 

[Daley]

Yes the outer batteries if you like, I have them numbered 1-4.
1 and 4 are where the + - going to mpp are and these two batteries were lower voltage than the others.

I did parallel them when I first set up and again when I just fully charged them Recently. I assumed because they were reading different voltages when in use that a balancer would be A good idea. Is there a reason not to have the balancer?

 

[CompMan2020]

Those balancers work great. I have 2 of the ZHC brand since they had more reviews than the brand you got. They do make a high pitched noise, but nothing crazy. You need to be right next to them to hear it. I haven't seen any issues with mine so far, seems like a very good investment.