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2x 12v Daly Battery banks in Parallel OK?

Choco

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Feb 14, 2021
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Hi, I started building up a 12v camping setup, then decided to add some more battery capacity.
I'm now wondering if the Two Daly BMS would have issues working in parallel?
Basic image attached...
 

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I have two 25 ah 24 batteries in parallel with a Daly BMS sized at 15 amp charge, 30 amp discharge. I would check the specs and then if not available contact the seller about your particular size. I think its OK, but Daly makes at least a couple different models.
 
I have 105ah + 125ah battery 12v battery packs in my own travel trailer, with "100A" and "120A" Daly Smart BMS units respectively. Both have BT comm interfaces. When the cellphone App starts up, it shows two compatible devices by address. (You can't give the addresses names, but you can distinguish one battery from another by the AH size parameter. In my case they're genuinely different - but for two identical 100Ah batteries you could just set the size of one as "99Ah", with the other set to "100ah".)

The 100A Daly has slightly different hardware and software than the slightly newer 120A. From the App, I am unable to set "SOC" within the 100A unit. But that's not a significant issue, because the Daly "SOC" display seems pretty worthless. (Maybe that's because "SOC" is based on voltage, rather than coulomb-counting, or maybe it's because Daly BMS doesn't pay attention to loads or charging with lower current levels. Or maybe both.)

In any case, Daly BMS is not a reliable coulomb counter meter - you will need a different one. I use just one meter on the entire bus, although meters for each individual battery would be more informative in the case of one battery developing performance issues due to a loosening connection, or a change in internal resistance. The case of a failing cell is well-covered already, with the cellphone App displaying the voltage of individual cells with the batteries upon connection.
- - -
Lots of people hate "Daly SMART BMS" units, recommending other brands. But I have not had any bad experiences with my pair of units (yet). I do not know how easily they may recover from shutdowns caused by over-current, over-voltage, or over-temp. I also don't know whether they are more (or less) prone to having the charge/discharge control circuits fatally "burned out" before executing the disconnection, in comparison to other brands.

I have not yet abused my batteries with any of those situations, and have no intention of "testing" BMS by creating such abuse. I have, however, left my batteries charging through a few sub-freezing nights - and I have observed (carefully, the first time) that the shutdown of the "Charge" circuitry does work correctly, preventing battery charge at temps below about 4C. This auto-recovered when they became warmer on the following day.
 
Thanks all, this gives me piece of mind.

When I noticed they had a Daly BMS within (unexpected, sealed case), I looked for a hidden Bluetooth module or port, but unfortunately they siliconed the port making it impossible to potentially plug anything in.

One last question, will these separate 12v cases self balance between each other, considering they will be on the same busbars?
 
They will all receive the same charging voltage, and SOC should generally become VERY balanced when the two (or 3) battery packs approach that voltage. (For the individual cells inside each case, balancing is up to the BMS). But incoming current may not be in balance during earlier SOC States of the charging process, because the internal resistance of each battery pack might be a bit different. It is good to keep those differences very small, when battery packs have the same size.

Similarly, in discharge, one battery may be "more willing" to provide current than the other at a given power draw and bus voltage.

When a set of parallel batteries all fall to significantly low in SOC, they may begin to differ moret. The shared bus will be drastically reducing power draw from the more discharged and less capable battery, pulling power from the "more capable "battery at higher SOC instead. But this situation should be very uncommon (because you should not make it a habit to drag down your LFP batteries to such low SOC on a regular basis).
 
Similar question, so joining in this thread rather than starting my own.

I have a 16s 200AH 48V battery using second hand CALB cells which only store around 6kWhr (Daly 150A BMS, BT, Powerboard).
Needing a little extra storage so want to add 16s 100AH 48V battery using second hand Sinopoly (green) cells (Daly 150A BMS, BT, Powerboard).
Max load 50A, which either battery pack can easily handle on it's own.

Any problems connecting these 2 BMS in parallel ........ I know Daly say NO (but they want to sell parallel kits).
I can't see any problem as long as I charge them to the same voltage before connecting together.
 
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