16s2p with 100Ah on one string 130Ah on the other?

[Mikeyfromoz]

Hi,

Can I put 1 x 16s 48V 100Ah with 100A Daly BMS in parallel with 1 x 16s 48V 130Ah with it's own BMS (each string of 16 batteries has it's own BMS)?
I will be pulling a max of 95A in total with the inverter, so in my mind, it wouldn't matter if one BMS turned off before the other, because each individual BMS can handle the load all by itself (each BMS will be set to 100A max discharge... charging will be a lot less than that while both BMSs are on as they will be connected to 5Kw of solar panels, but they will also be set to 100A charging each) .
As for charging and discharging, in my mind, the voltages will always be the same (give or take milliamps) between both strings, so there will just be more amps going in and out of the 130Ah string than the 100Ah string as the voltages rise and fall...
I will have the inverter positive connected to one bank, and the inverter negative connected to the other bank, with short jumper cables between both banks (or BMSs).

So, will that work???

Cheers,
Mikey.

 

[Steve_S]

Most common & practical way to setup a Parallel Battery System is to use (+) & (-) Busbars.
Connect both batteries to the BUS and then the BUS to your gear.
Each battery pack should be fused, you could use either 150A or 200A fuses.
Typically, such an install will have a shutoff switch between the Common DC Bus and gear. Most folks use a BlueSea Switch.

NOTE! A 100AH LFP Pack will DISCHARGE @ 1-C / 100A but will ONLY TAKE 0.5-C Charge / 50A, do not attempt to shove 100A at it, the BMS will cut off.

When batteries are in Parallel, they will split the Charge & Discharge proportionately (based on their capacity).

 

[Steve_S]

A picture is worth a thousand words eh. I drew this up to make it a bit easier. Obviously, this is for a component system and not an AIO (All-In-One).

• Busbars used @ Battery should be rated for Maximum Current Potential. Avoid the cheapo deals on Amazon/E-Bay.
• Keep battery to busbar wire lengths identical, the Fuse is part of the length.
• If a Battery is capable of 100A but can do 200A surge output, fuse accordingly.
• Class T Fuses are preferred within their own holders. Alternatively, MRBF Fuses are quite acceptable
• Generally, a Smartshunt is used to monitor Power In/Out and the State of Charge of the battery bank.
• A Disconnect from the battery bank is prudent for maintenance work +.
• Solar Controller output should be fused to its maximum Amp Output (Too many forget this detail, req for inspection pass)
• A Separate Battery Charger if so equipped should also be fused for its Max Amperage output.
• Inverter/Charger also to be fused IE: a 4000W Inverter @ 48V would require 80A Fuse/Breaker. (#### Watts ÷ 51.2V = Amps) BUT remember that an HF Inverter can do 2X surge handling and an LF model can do 3X surge handling. (HF = High-Frequency, LF = Low Frequency)

* Fuses or DC Breakers will accomplish the same thing and allows some flexibility. Stick to Known Good quality components ONLY, this is one area where saving a few pennies buying cheapo offshore stuff can bite you really hard !

 

[Mikeyfromoz]

Most common & practical way to setup a Parallel Battery System is to use (+) & (-) Busbars.
Connect both batteries to the BUS and then the BUS to your gear.
Each battery pack should be fused, you could use either 150A or 200A fuses.
Typically, such an install will have a shutoff switch between the Common DC Bus and gear. Most folks use a BlueSea Switch.

NOTE! A 100AH LFP Pack will DISCHARGE @ 1-C / 100A but will ONLY TAKE 0.5-C Charge / 50A, do not attempt to shove 100A at it, the BMS will cut off.

When batteries are in Parallel, they will split the Charge & Discharge proportionately (based on their capacity).

Awesome, thank you, tons of info there, some I was aware of, some not
At this stage, I only have one 2.5Kw string of solar panels connected to the hybrid inverter/charger, and then to 1 x 16s battery string, so that will limit the charge to about 0.5C.
When the second set of batteries arrive, I will restrict the charge rate to 50A (or 0.5C) on each BMS.

Cheers

 

[Mikeyfromoz]

When batteries are in Parallel, they will split the Charge & Discharge proportionately (based on their capacity).

Thank you, I was 99.9% sure of this, but a couple of people said no... but I think that at least one of them confused parallel connection with serial connection (which we all know is completely different and obviously you can't mix battery capacities in series).
Some of the reasons why not to connect them in parallel were far beyond ridiculous, so I rejected their input LOL

Cheers

 

[Steve_S]

In Series, you increase Voltage only. Different Sized batteries in Series = BAD !
In Parallel, you increase the Capacity/Amp-Hours and you CAN use different AH Batteries BUT (there has always gotta be a "but") they can't be too different otherwise the bigger will try to Back-Charge the smaller when they get low.

I run 5 Battery Packs. 2x 174AH & 3x 280AH giving me 1190AH/30kWh. From 100%SOC down to 25% they are in lockstep without issues and then the 280's try to back charge a bit (it's minimal) but if I go deeper it gets noticeable. My setup is similar to what I drew up there, EXCEPT instead of two "intake" busbars with fuses, I have a Midnite Solar E-Panel with a 250A Master Breaker that connects the show to the inverter.

 

[Mikeyfromoz]

In Series, you increase Voltage only. Different Sized batteries in Series = BAD !
In Parallel, you increase the Capacity/Amp-Hours and you CAN use different AH Batteries BUT (there has always gotta be a "but") they can't be too different otherwise the bigger will try to Back-Charge the smaller when they get low.

Yeah, thanks, that's how it works in my head

"I run 5 Battery Packs. 2x 174AH & 3x 280AH giving me 1190AH/30kWh. From 100%SOC down to 25% they are in lockstep without issues and then the 280's try to back charge a bit (it's minimal) but if I go deeper it gets noticeable. My setup is similar to what I drew up there, EXCEPT instead of two "intake" busbars with fuses, I have a Midnite Solar E-Panel with a 250A Master Breaker that connects the show to the inverter."

Cool, noted, cheers