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diy solar

Is this the correct way to wire 4S5P?

Roger that. Based on Will's review, I was planning on using the ElectroDacus SBMS120.
 
The cost of building that amount of packs will be excessive compared to alternatives.
What will 20 x 180AH cells cost you with delivery ?
Compare to 16 x 280AH cells for 1150 AH @ 12V for US $2,178.84 delivered to USA
- link under image.

Also it is very important to properly wire parallel packs in a bank to maintain balance for charge/charge loading.
Please refer to this doc by Victron: https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

xuba-280x16.JPG

 
1. Thank you for your input. You are correct. The system I have designed will cost approximately $4400. Your option is half that. 2. Yes, balancing is top of the list. I have seen a 4s5p 180ah 3.2v system using balancing leads in the "middle" of each string using the ElectroDacus BMS. Your option is, I think, a better one. Also, thank you for the PDF from Victron. This is exactly why I sought out info from this forum. I need the experts to opine. Take care.
 
1. Thank you for your input. You are correct. The system I have designed will cost approximately $4400. Your option is half that. 2. Yes, balancing is top of the list. I have seen a 4s5p 180ah 3.2v system using balancing leads in the "middle" of each string using the ElectroDacus BMS. Your option is, I think, a better one. Also, thank you for the PDF from Victron. This is exactly why I sought out info from this forum. I need the experts to opine. Take care.
Always happy to help folks make ththe jump towards freedom & independence !
AND this is easier than bein a freedom fighter or revolutionary LOL plus SAFER TOO !
I also have a severe aversion to seeing people waste good money, there is just never enough of the stuff IMO.

BAD NEWS THOUGH ! Xuba is all out of 280AH cells now till around April 5th, there are other vendors selling identical cells but none that I have dealt with. Some folks have bought them elsewhere and did good but I know a coupe of people got seconds / grade-B or even used ones. So always check & verify and go by recommendations from people who have bought, tested & verified that they got good product.
 
I heard its better to use parallel first and then put them in series
 
For a 24v system I could use an 8s2p layout.
To get the most out of your packs and most redundancy the "best" option is to built two independent 24V 8S packs each with it's own BMS and then parallel the packs into one bank. Should one cutoff for any reason the other will keep going, charge & discharge loading is shared equally across both IF properly wired to do so. This excellent doc from Victron explains it all very well. https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf
 
To get the most out of your packs and most redundancy the "best" option is to built two independent 24V 8S packs each with it's own BMS and then parallel the packs into one bank. Should one cutoff for any reason the other will keep going, charge & discharge loading is shared equally across both IF properly wired to do so. This excellent doc from Victron explains it all very well. https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf
Thank you Steve. This makes sense. I was drawing up designs that were series/parallel/series and was losing my mind. This type of design you describe would have both 24v banks of 8s cells going to their own BMS and from the LOAD of each BMS tying together on a single bus bar? Correct? This makes balancing each bank very simple. One step at at time. Many thanks.
 
Yes, using the common bus topology is the simplest overall and can be balanced properly.

Here is a simplified "doodle" from my XUBA thread (in my signature) whch puts a simplified picture on it. BUT the Victron Doc is much more detailed. (this drawing is out of date as my build is evolving now... there will be two 175AH packs & two 280AH packs. Each 8S with a Chargery BMS8T-300 and dual relays.

lfp-parallel-packs-jpg.6157
 
Steve,
Can you tell me more about the relays? Am I seeing one or two relays attached to each BMS? What are the specs for the relays you recommend? I am making two 24v batteries each consisting of 8 cells (100Ah), each with their own BMS, which I will then connect in parallel. I appreciate any help you can give me. Mike
 
ATM, I am working on the relay section & delay board section of the Chargery Manuals. The Standard Electromechanical Relays that Chargery provides are OK,, good for EV's but not so much for residential. The relays used also depend if being configured for "Separate Port or Common Port" operation. The "doodle" above is related to using a Chargery BMS with Relays, many of the smartBMS' are FET based and do not use relays but the wiring principles for BUS Topology are the same. I am in deep investigation of SSR (Solid State Relays) and alternative relays which consume less "running" power to minimize the drain on the battery pack. *1

*1 IN a properly configured & operational system with Solar Charging which is fully capable of recharging a battery bank within normal sun hour range, the heavy duty "thirsty" relays are fine as what they take out get's replaced. The HD relays become a liability IF there is no consistent charging such as an EV with no solar input. But with an EV, it's not on all the time and the BMS would be turned off with the vehicle and when the vehicle is being charged the BMS is ON so it can accept the charge to the batteries. In Residential applications, this has to be considered and planned for depending on overall config.

8x100AH cells = 24VDC/100AH and at 1C discharge rate of 100A that's the "usual" top of the draw capacity. If properly paralleled the discharge & charge get split between banks. Fusing should be able to support the full Inverter Draw amperage.

Additionally, if using a BMS with Relays, the Discharge Relay is the biggest as it handles the most amperage outbound demanded by the Load (Inverter). The Charge Relay needs to handle the maximum input charge Amperage from the charging sources. The "Small Charge" relays is used for pre-charging an inverter from dead cold (Inverters can have a huge start draw if capacitors are discharged). Depending on Config, these need to be adjusted appropriately.

Your next step is to evaluate what type of BMS you want, what features / function that you "need" have, what you would "want" to have. If you go with a "typical" FET based SmartBMS then relays are pretty moot.
 
Today I just received two Daly BMS. They are common port and rated at 200A discharge, 80A charge. I am in an off the grid house in Montana. I have plenty of summer sun but in the winter I can have thick clouds literally for months, so I charge my batteries in winter with an AC generator. I’m lucky in that my system (inverter/charger and SCC, made by Outback power, allows me to control many of the parameters which could be problematic such as maximum charging amperage, maximum discharge amperage. I had lead acid batteries But I am just getting started to change over to lithium iron phosphate. Everything about relays and shunts is completely new to me.
 
Today I just received two Daly BMS. They are common port and rated at 200A discharge, 80A charge. I am in an off the grid house in Montana. I have plenty of summer sun but in the winter I can have thick clouds literally for months, so I charge my batteries in winter with an AC generator. I’m lucky in that my system (inverter/charger and SCC, made by Outback power, allows me to control many of the parameters which could be problematic such as maximum charging amperage, maximum discharge amperage. I had lead acid batteries But I am just getting started to change over to lithium iron phosphate. Everything about relays and shunts is completely new to me.
There you go. relays are MOOT !
DO CALIBRATE for Voltage correction !!!
 
There you go. relays are MOOT !
DO CALIBRATE for Voltage correction !!!
Thanks Steve for your help. And thanks for that link to your previous post about voltage matching. It was really very clear and easy to understand. Take care, Mike
 
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