If there is a BMS, why do I need a solar panel controller?


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ynot

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May 28, 2021
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So my tractor has a 32 Volt nominal panel for a roof/sunshade. worked ok with LA batts at 24 volts, the charge controller failed a year ago so I connected up the panel direct, no problem.
Now with lithium batts powering the tractor at 40 Volts +/- I cannot put another panel on the tractor so am thinking about a solar charging station, so asked myself why do I need a controller?. Now I have quite a bit more information to ponder.
Thanks to all.
Tony
 

hbpowerwall

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Wolf here is one, there are more if you ask youtube for leaf modules with no BMS.


Tony.
A BMS isn't for all the good days, it's for the 12 seconds in a min/hour/day/week/month/year that you have a bad day..
 

ng.sa

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Apr 4, 2017
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G'Day Ynot ( g8 handle BTW )

You need to think about your design.

In the dim dark past I decided to double wire LIB packs.

1st was designed to connect to a solar panels as input - charge - no intelligence except CC for monitoring on the panel side.

2nd was wired to BMS - discharge - so if you connected this to an inverter ( no intelligence ) the BATs didn't get the guts dragged out of them !!!

If I want to use the pack to run a 24V fridge I discharged on the 1st circuit as fridges have a "Low Water Mark' will not discharge below approx. 22V.

I have only tested about 50 fridges so this might be found to be an ASSUMUPTION.

Edit : Obviously you have full control of the wire gauge on the 1st, but until a few days ago I didn't know how to control the wire gauge of the BMS
 
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Wolf

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I appear to have set off a firestorm, unintended I assure you.
Ah but you did. Which is OK as it engages the community into a discussion. Good work @ynot !;)
A BMS isn't for all the good days,
I was just about to post exactly that and you beat me to the punch.
Just because you can run a bank of batteries without a BMS does not make it right. As @daromer says it is wrong. Those are the same people that sneer at shunt trip breakers because they are too expensive. They are also the people that when they have fires, blame Li-Ion cells instead of their stupidity. Same folks would probably wire an outlet without GFCI into a bathroom next to the tub and run a15A circuit on a 20A breaker. Or maybe their fuse panel is so old that they still have pennies for fuses.
It would be funny if it wasn't so sad.
Wolf

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ynot

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Ah but you did. Which is OK as it engages the community into a discussion. Good work @ynot !;)
Thanks.
Same folks would probably wire an outlet without GFCI into a bathroom next to the tub and run a15A circuit on a 20A breaker. Or maybe their fuse panel is so old that they still have pennies for fuses.
It would be funny if it wasn't so sad.
Wolf
Whats wrong with that, pennies are good conductors. & I like to use my hair blower in the tub.

PS: Wired my house abuilding and passed the electrical inspection no prob.

Thanks to all for the info, trying to learn as much as possible, this ole dog is trying to learn some new Li tricks.
ynot.


 

Cheap 4-life

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This
Wolf here is one, there are more if you ask youtube for leaf modules with no BMS.


Tony.
guy in this video is doing work for people but he barely knows his *** from a whole in the ground. Sorry but that’s what I think every time I see his videos pop up on YouTube
 

ynot

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This

guy in this video is doing work for people but he barely knows his *** from a whole in the ground. Sorry but that’s what I think every time I see his videos pop up on YouTube
My first BMS arrived today, have two more on order.
Going to do a 10s2p pack so took my 10 modules and paralleled them with a small load (12 volt rv lamp) to equalize them. I will bring them down to 8Volts & then begin the assembly.

We under extreme fire watch alert tonight, hope I will still have them tomorrow.
 

J tech

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May 10, 2022
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Is simple meaning BMS work to avoid overcharging each cell and balanced voltage while the SOLAR CHARGE CONTROLLER control the surge of the output voltage from the panel??

Does bms can support the voltage output range of solar panel..


And does the Solar charge Controller give more efficient energy to battery or just spliting it volage that only exact to the battery pack?
 

Crimp Daddy

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Feb 21, 2018
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Let's simplify further, in terms of a basic function....

A good solar charge controller is a DC-DC converter and CC/CV charger.

A BMS is a CELL monitoring device and a switch.

There may be instances where one could see an overlap in features/function, just as as one would when comparing a breaker and fuse, but that does not mean one is a replacement for the other.

Rare to find an exception to a rule, ElectroDacus comes to mind, but it's niche and far from the majority example.

From a design/logistics/pricing standpoint it makes sense they would be two separate devices. Vast variations in solar configurations combined with endless battery configurations... it's clear you can cover more ground with separates than trying to accommodate everyone with a single solution.
 

Korishan

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Is simple meaning BMS work to avoid overcharging each cell and balanced voltage while the SOLAR CHARGE CONTROLLER control the surge of the output voltage from the panel??

Does bms can support the voltage output range of solar panel..


And does the Solar charge Controller give more efficient energy to battery or just spliting it volage that only exact to the battery pack?
In addition to Crimp Daddy's reply, the other thing to consider is that the BMS does not do any current limiting and voltage limiting at all. It is either On or Off. The Charge Controller (regardless if it is a Solar, Wind, AC, etc) monitors battery voltage and only applies the proper amount of voltage/current sufficient to bring the battery up on charge. Depending on how good of a charger it is, this can be in huge steps (ie, dead battery is starts out at 50% voltage level, ie 10V on lead acid, and then jump to 12V when that is reached) or it'll be more gradual where the steps are far more incremental (ie, keeps the input voltage just above battery voltage to keep dumping charge).

This is also true on the current input. Some chargers will just dump how ever much they have available, others that are much more smart, will slowly ramp up the current until a certain voltage is attained, and then ramp back down. This extends the life of the battery drastically, regardless of chemistry.

There are very few Charge Controllers that also have a BMS style component built in as well. It is far more common to have an Inverter/Charger combo with a BMS device off to the side.

So yes, you need both devices to properly charge and maintain/monitor the battery.

From a design/logistics/pricing standpoint it makes sense they would be two separate devices. Vast variations in solar configurations combined with endless battery configurations... it's clear you can cover more ground with separates than trying to accommodate everyone with a single solution.
Plus the cost of the unit that can do all of that, BMS/Charger/Inverter, would cost a LOT. Considering that it would be designed to handle a wide range of types of batteries, voltages, chemistries, etc and Solar configurations as well. They wouldn't want to make 50 different devices that did basically the same thing but handle different external components.
So this would get stupid expensive really quick.
Better to keep the devices separate to help keep costs down. Also helps to keep maintenance down, too. If one device goes bad, it doesn't completely cripple the system. Just replace the part that is down and cut downtime down
 

Crimp Daddy

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Plus the cost of the unit that can do all of that, BMS/Charger/Inverter, would cost a LOT. Considering that it would be designed to handle a wide range of types of batteries, voltages, chemistries, etc and Solar configurations as well. They wouldn't want to make 50 different devices that did basically the same thing but handle different external components.
So this would get stupid expensive really quick.
Better to keep the devices separate to help keep costs down. Also helps to keep maintenance down, too. If one device goes bad, it doesn't completely cripple the system. Just replace the part that is down and cut downtime down

Yes, the manufacturer needs to determine if it is a viable for marketability / cost.

I believe this research has been done, and it was determined: just because something can exist, does not mean it should.

Having a single device isn't going to be competitive solution.
 
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