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Newcomer to lfp. Oldtimer to sla. Need advice on bms

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Lutz1107

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Jan 9, 2022
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Hello all. I'm currently running 24 6v sla batteries in a 24v configuration. 4s 8p. Total 30kw roughly. I'm charging with 2 midnite classic 150 and 19 420watt qcells. The batteries are operating at below freezing most winter days in a small shed. I am hearing the shed but it's constantly a pain worrying about freezing. Soooooo I'm planning on replacing with some DOCAN 100AH lfps (amy zheng). Any one have any experience with a good bms. Planning on 8s 24v bms. I got a DALY clone but are there better options.. ALSO ANY ADVICE ON ANY COMPONENTS IS ALWAYS WELCOME.

3 cotek sd3500 inverters
19 420w qcells
120amp 24v chargers running off 8.5kw generator. ATP auto champion using propane.
2 midnite solar classic
24 6v 220ah batteries SLA

Running whole house for 4 years. I have no electric other than solar. Living in allegheny national forest. I have 0 issues with produced electric 120/240 90amp service from the setup.
 
A handful of people seem to like the JBD BMS a lot around here... Of course there are other brands that are great too. Are there any particular features you require in a BMS? App monitoring, cold temp charging cutoff, inverter communication compatibility, etc. There are a lot of factors that can go into deciding on a BMS.

But I really liked the OverKill BMS for my 4s 12v banks, and then I found out JBD makes them so I bought 4 more 16-20s ones for my 48v setup... But there are plenty of other brands that people like as well.

You definitely need a BMS where the low temp cutoff actually works in it (since charging lithium below freezing destroys them). You also need to figure out a solution for battery cell warming, or else they will never tend to charge, as the BMS will shutoff below freezing. So you will need to either insulate and warm the shed, or do a heater blanket, or heat pads (in insulated box), or something to that effect.
 
Well one of the reasons for changing is to bring the batteries inside. Temp should be 70s all year round. Just really need the bms to allow plug play with the sla. I know I'll need to change some charge settings on the midnite. I'll duckduck the jbd and see where I can pick one up. Thank you kindly for the input
 
Sounds great. I purchased my 16-20s JBD from AliExpress in China but I had wanted 200a, and OverKill didn't sell a 200a model in that amperage. AliExpress takes a long time to get them here though.

Depending on how many amps you need, you could check out OverKill's site and see if their 8s ones are big enough for you.

overkillsolar.com

Shop – Overkill Solar

This is where you can browse products in this store.
overkillsolar.com overkillsolar.com
 
Will do. Should get the battery's from you in a couple days and my first bms from Amazon next tuesday
 
Hi Lutz.
I think I'm kind of in a similar situation... But let me see if I understand correctly- It IS POSSIBLE to replace AGM or GEL batteries with LiFePO4 just by putting a BMS in between? The BMS will make the charger/inverter think it's an AGM Battery? Did I understand this right?

Thanks
 
Since I posted I set up an array of 32 lifepo4 Batteries. I have them configured as 24v. I'm using a jbd 8s on each pack I built. I have them connected right to my main power which is 24 220amp 6v golf cart Batteries. I dropped the absorption voltage to 29.6 and float to 26.4. Pretty cool. Just in the process of getting the balancing correct.
 
Lutz1107 said:
The setup
Click to expand...
OK, I think I get it. I'm located in Mexico, and this brand is basically what we can get fairly easily and with warranty, etc....




1643657678684.png

The "DC SYSTEM" part is where I would connect my DC Ports of the Inverter/Charger (MPP Solar LV2424)

1643657596506.png
So basically I will need one of those BMS thingies for each 12KW Batteries I want to attach to the system, right?
Why can't the batteries themselves have these electronics inside and just behave as a AGM/GEL Battery?


Thank you for your time, Lutz. Your setup looks like something I would have made! :love::love:


Screenshots taken from here:
 
The LYNX BMS connects to the LYNX Battery Packs with their internal electronics. (not a generic device)
There are BMS' which are compatible with Victron and connect to the system.
Be VERY CAREFUL as to what components you are buying and what exactly they do and in this case how they interconnect.

Myself, I am now changing my Entire Fleet of LFP batteries (30kWh Bank + utility packs) over to JKBMS with 2A Active Balancing, BlueTooth, RS485/CanBus. I'm replacing 7 Chargery BMS8T's with 300A Solid State DCC Contactors, and QNBBM-8S Balancers and the utility packs JBD BMS with Capacitive Balancer and another older JK With Capacitive Balancer. To put it simply, over $3K USD being replaced ! I am also the guy who wrote the Chargery BMS Manuals and helped dev some of their gear as well... and a lot of other things around here as well...

Here is what I am installing into everything now.
JK-BMS [24S 2A 150A BT] with BlueTooth Part Number: B2A24S15P $143.29 USD
Product Link: https://www.aliexpress.com/item/1005003104573871.html
-plus add: CANbus Module + RS485 Module $7.73 USD each
Product Link: https://www.aliexpress.com/item/1005003451100409.html
 
hartosol said:
Hi Lutz.
I think I'm kind of in a similar situation... But let me see if I understand correctly- It IS POSSIBLE to replace AGM or GEL batteries with LiFePO4 just by putting a BMS in between? The BMS will make the charger/inverter think it's an AGM Battery? Did I understand this right?

Thanks
Click to expand...
I know I am over simplifying this, but here goes:

I don't think you understand what a BMS is. It is part of your battery. In pre-made like Battle Born (or others) there is a BMS inside the case. It is part of the battery. If you DIY build your battery with LiFePo4 cells you need a BMS to group your cells together into a battery. It enables you to set charge/discharge parameters and protect the battery. A BMS does not go between a battery and your system it is a part of the battery. Your charger does not think your battery is AGM/LiFePo4/SLA. Your charger output needs to be set for each type. If using solar charge controller you set it for each type. BMS is a part of your battery. None of these pieces talk or coordinate with each other. You input battery type yourself manually into whatever charger you have. Some are specific to a battery type to give optimum voltages for each.
 
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