diy solar

diy solar

Help with Understanding BMS amps

Here is the big idea.

Make three independent systems that only peer at the ac output.

The benefits are a individual cell monitoring and balancing.
COTS=common off the shelf components.
Fault tolerance.
Easy OAM=operations administration and maintenance

If anything is not clear just holler.
I can also make some ascii art if you wish.
 
smoothJoey said:
Here is the big idea.

Make three independent systems that only peer at the ac output.

The benefits are a individual cell monitoring and balancing.
COTS=common off the shelf components.
Fault tolerance.
Easy OAM=operations administration and maintenance

If anything is not clear just holler.
I can also make some ascii art if you wish.
Click to expand...


To be honest all this bms talk is foreign to me. Ive been googling about 48 volt bms running 3 strings for 2 weeks and havent found much. Havent seen much on youtube unless their premade lithium that cost 12k like the one engineer775 on youtube uses in his home.


practicalpreppers.com

Fortress eVault 18.5kWh Lithium Battery - Practical Preppers

Fortress Power’s engineers are on a mission to provide you with the most advanced Lithium Iron Phosphate Battery available! Not only is the new Fortress eVault 18.5 kWh battery safe, long-lasting and affordable, but is also equipped with a brand new LCD screen that displays voltage, state of...
practicalpreppers.com practicalpreppers.com



They connect together and talk. In his video when he hooked em up 2 of em one was recieving the bulk charge and then when full the other got the rest.


If i could have a bms thats communicating with one another like SteveS was talking about that would work.

I want something simple, that works, and i dont have to fool with. It needs to operate on its on because i wont be around to babysit it.

Dont want to overcharge the cells or have em getting below 20%. If its too cold or hot it shuts off, something wrong with the cells it protects it. Etc

I hear its good to charge and discharge the cells a couple of times before i start using them. How do i do that on a 48 volt system?
 
Here are the instructions
The systems are independent except at the ac peering.
Code: 
... = repeat last element
mrbf = marine rated battery fuse
bms = commodity battery managment system not in the current path
battery = {
    + disconnect_switch<->mrbf_fuse<->cell_in_series<->...
    - shunt<->bms<->cell_in_series<->...
}
subassembly = {
    + battery<->inverter_charger
    - battery<->inverter_charger
}
system = {
    subassembly->|
    subassembly->|->ac_panel
    subassembly->|
}
 
Last edited:
smoothJoey said:
Here are the instructions
The systems are independent except at the ac peering.
Code: 
... = repeat last element
mrbf = marine rated battery fuse
bms = commodity battery managment system not in the current path
battery = {
    + disconnect_switch<->mrbf_fuse<->cell_in_series<->...
    - shunt<->bms<->cell_in_series<->...
}
subassembly = {
    + battery<->inverter_charger
    - battery<->inverter_charger
}
system = {
    subassembly->|
    subassembly->|->ac_panel
    subassembly->|
}
Click to expand...


Here is something that i was looking at originally its kinda the same thing i have now on my trojan setup.

Screenshot_20200604-192159_Samsung Internet.jpgScreenshot_20200604-192159_Samsung Internet.jpg
 
@Bleedingblue
I think your tripping over terms in a sense. BMS' are not typically rated for the voltage handling, it's rather the Amperage Handling. You seem to be hung up on "48V". I use Chargery BMS that rely on external Contactor Relays, these can take 12VDC or 96VDC as the relays / contactors are rated for that but the Amperage passing through them is what really matters. Chargery is a great BMS but it's a techy system too and not necessarily what you "need" or want even for your usage. That Common Bus Topology diagram of mine you posted is the basics for building a bank with parallel independent packs and if you read the Victron Doc I posted previously, you'll see how that all comes into play.
** point of note: All wiring should be the same gauge & lengths to keep resistance & impedance matched. Battery Bank MUST be Voltage Calibrated with the Inverter/Charger & SCC systems. Meaning that Voltage readings at the BATT Bus Bars is matched / corrected by the devices.

Here is a Terrific Resource which discusses the different kinds of BMS' manufacturers, topologies & design types. Remember, I said there are many types for many use cases. http://liionbms.com/php/bms_options.php In fact there is much more info there than just on BMS' and a worthy resource to bookmark & use as reference.
 
Bleedingblue said:
Ive seen orion and watchmon 4 bms being tossed around. Which one or are those more than what i need
Click to expand...
I use an Orion since it was the least expensive (OrionJr) when I started five years ago. It has a lot of features for an EV that are not needed. It uses external shunts and contactor so it is more capable. I don't enable balancing but it has user setting for that. Also they have recently introduced a cloud based monitoring interface that allows me to look at trends in voltage, Amps, cell deltas, SOC and temperature. It has actually helped me understand what and when my inverter is doing something. If you are into data and want the ability to remotely check on your battery from anywhere in the world I recommend it. It is more expensive but the data is priceless.
 
Steve_S said:
@Bleedingblue
I think your tripping over terms in a sense. BMS' are not typically rated for the voltage handling, it's rather the Amperage Handling. You seem to be hung up on "48V". I use Chargery BMS that rely on external Contactor Relays, these can take 12VDC or 96VDC as the relays / contactors are rated for that but the Amperage passing through them is what really matters. Chargery is a great BMS but it's a techy system too and not necessarily what you "need" or want even for your usage. That Common Bus Topology diagram of mine you posted is the basics for building a bank with parallel independent packs and if you read the Victron Doc I posted previously, you'll see how that all comes into play.
** point of note: All wiring should be the same gauge & lengths to keep resistance & impedance matched. Battery Bank MUST be Voltage Calibrated with the Inverter/Charger & SCC systems. Meaning that Voltage readings at the BATT Bus Bars is matched / corrected by the devices.

Here is a Terrific Resource which discusses the different kinds of BMS' manufacturers, topologies & design types. Remember, I said there are many types for many use cases. http://liionbms.com/php/bms_options.php In fact there is much more info there than just on BMS' and a worthy resource to bookmark & use as reference.
Click to expand...


Well when i say 48 volt it just means a 16s bms in my mind not a 8s. Ive been reading on that doc and it is quite lengthy.
In my own 24 battery system i have all my 4/0 cables of equal length to each string. I use a bolt as a busbar.

And i bookmark all the items being discussed for future reference. All of it is welcome so i can get my feet wet using the lithium.


When the batteries are full does the hybrid charge controller/ inverter dump the remaining power back into the electric panel for house and shops to use?
 
Last edited:
Bleedingblue said:
When the batteries are full does the hybrid charge controller/ inverter dump the remaining power back into the electric panel for house and shops to use
Click to expand...
Generally that is the case. A lot depends on settings. For example if your panels panels are outputting 30 Amps and your charge settings are 25 Amps then 5 Amps are available for house at that moment. When batterires are full the house will get the full 30 Amps if it can use it. Otherwise the solar production is curtailed to match house load assuming you are off grid.
 
Bleedingblue said:
When the batteries are full does the hybrid charge controller/ inverter dump the remaining power back into the electric panel for house and shops to use?
Click to expand...
My equipment is not all in one. I use a Midnite Solar Classic 200 SCC and Samlex EVO-4024 Inverter. With mine, if draw is up to what the panels are generating that is used first and the balance over what is being produced falls to the battery bank. Fortunately the Midnites + WizBangJr you can monitor quite a bit of what's going on. From what I have read, Victron Gear does the same and pretty much all the "All-In-One" systems by decent companies like MPP-Solar, Growatt and better do. Some have better programming & flexibility than others but like all things, there is a cost for such.

There is a BONUS some people take advantage of as well. With certain gear, you can use the power coming off the panels once the batteries are full to Dump the power to heat Hot Water or use for other supplements that can save on energy costs. It is good to think of potential uses when planning your system and thinking longer term that can be done over time as well. So having the feature / capability available for later use can save you a bundle if you had to change / add equipment to use the ability. Like the foundation of a house, the better the foundation the more it can support, even if you add-on later.
 
Steve_S said:
My equipment is not all in one. I use a Midnite Solar Classic 200 SCC and Samlex EVO-4024 Inverter. With mine, if draw is up to what the panels are generating that is used first and the balance over what is being produced falls to the battery bank. Fortunately the Midnites + WizBangJr you can monitor quite a bit of what's going on. From what I have read, Victron Gear does the same and pretty much all the "All-In-One" systems by decent companies like MPP-Solar, Growatt and better do. Some have better programming & flexibility than others but like all things, there is a cost for such.

There is a BONUS some people take advantage of as well. With certain gear, you can use the power coming off the panels once the batteries are full to Dump the power to heat Hot Water or use for other supplements that can save on energy costs. It is good to think of potential uses when planning your system and thinking longer term that can be done over time as well. So having the feature / capability available for later use can save you a bundle if you had to change / add equipment to use the ability. Like the foundation of a house, the better the foundation the more it can support, even if you add-on later.
Click to expand...


I also use a midnite classic 200 with the aims 10k inverter. With my 12-335 watt panels on the best of days in the summer i can generate 24kw. Only every so often will I turn the charger on the night before to charge the batteries so it can go into float and obsorb mode to burn the plates.
I just did a money order for the 48 280AH cells. I also asked on alibaba a company about prices on 48 340watt panels. Those combined with the ones i have now will have me close to 20kw on paper of panels.
Prob gonna buy 5 of the Revo II hybrid controllers. Have 1 as a backup.

This is my plan so far.



Thank you guys for all yalls help. I know it can be like talking to a rock but eventually i will understand how it all works.
 
Can I twist this question a little? I often see batteries for sale with continuous discharge rate at much less than their rated capacity. For example a 200ah battery continuously discharging 100A or 150A. I always wonder why they sacrifice output. Only two answers occur to me. #1 the maker wants to extend battery life or #2 the maker wants you to buy 2 batteries when one would suffice. Wonder if I'm missing something. Also, I'm wondering what the drawbacks would be to having a continuous discharge rate slightly ABOVE the amp hour capacity say configuring a 120ah battery to continuously discharge 150A. I know this is possible; but I almost never see a battery for sale configured this way.,
 
Magellan44 said:
Also, I'm wondering what the drawbacks would be to having a continuous discharge rate slightly ABOVE the amp hour capacity say configuring a 120ah battery to continuously discharge 150A. I know this is possible; but I almost never see a battery for sale configured this way.,
Click to expand...
Some batteries are better for EVs and some are better for stationary storage. I converted a VW to An EV and used Winstons. There were some moments when I am sure I was pulling 400 Amps out of those 100 Ahr batteries. I was getting zero to sixty feet times of two seconds and it was a lot of fun. I don't need that while I am on my couch at home when the power goes out or I am load shifting with my stationary pack. Most of the high power density batteries in China are going to the EV manufacturers. What we are seeing in the market is batteries designed for less power density that are used in street lights and sold to us for stationary storage.
 
Ampster said:
Some batteries are better for EVs and some are better for stationary storage. I converted a VW to An EV and used Winstons. There were some moments when I am sure I was pulling 400 Amps out of those 100 Ahr batteries. I was getting zero to sixty feet times of two seconds and it was a lot of fun. I don't need that while I am on my couch at home when the power goes out or I am load shifting with my stationary pack. Most of the high power density batteries in China are going to the EV manufacturers. What we are seeing in the market is batteries designed for less power density that are used in street lights and sold to us for stationary storage.
Click to expand...


In car audio they have just 100AH batteries that supplies amplifiers that pull over 1000 amps when playing music. Of course the alternator is taking up some of that say a 370 amp alternator.


Screenshot_20200610-170302_Samsung Internet.jpgScreenshot_20200610-170316_Samsung Internet.jpgScreenshot_20200610-170322_Samsung Internet.jpg


limitlesslithium.com

45ah

High quality high discharge Lithium Batteries for Car audio 12 volt stereo systems
limitlesslithium.com limitlesslithium.com
 
Last edited:
Bleedingblue said:
In car audio they have just 100AH batteries that supplies amplifiers that pull over 1000 amps when playing music. Of course the alternator is taking up some of that say a 370 amp alternator.
Click to expand...

What is the c rating on those batteries?
Are they prismatic or cylindrical?
Are they being cooled?
 
You must log in or register to reply here.

Similar threads

W
Will Solar charge controller work.
Replies
6
Views
192
Rednecktek
Rednecktek
sutton
24 volt van build
2
Replies
22
Views
928
Bop
B
C
To buy or to build
2
Replies
29
Views
1K
OffGridForGood
OffGridForGood
G
24 versus 12 V
Replies
12
Views
663
ZEUS-FL
ZEUS-FL
D
Class J fuses for battery bank
Replies
0
Views
95
DPC
D
Back
Top