Lindsay

For anyone still following, the Canbus output above didn't seem to give me the data I wanted, instead I tried modifying Schallas's code for the Daly Smart BMS (https://github.com/tomatensaus/bms) to use the half-duplex RS485 connection on the PI hat I ordered from Micro Robotics (www.robotics.org.za/W14882). I had to modify the code so that I could send a command while in transmit mode then quickly switch to receive to get the response, however I would often miss the first few bytes so I had to allow for this (by filling in the missing bytes if we just missed the first couple since these are always the same) as well as modifying it to retry until the checksum is correct. However although I could get it to work there were a lot of retries which slowed down getting all the data I wanted. So instead I ended up buying an external USB to RS485 module (https://mantech.co.za/ProductInfo.aspx?Item=15M5345) which seems to handle the transmitting and receiving automatically. Then I was able to use more of the original code, but left the retry loops I added as occasionally the checksum does still fail. I have attached the Python code if anyone is interested, by default it should work for the USB to RS485 module, but see the comments in the script for instructions on how to modify it if you want to try use it with the half-duplex hat. dalyUsbRetry.py

For anyone interested, I realise I didn't use 9600, actually initialised as: "sudo ip link set can0 type can bitrate 500000"

I managed to get some data from canbus when I finally set the correct baudrate (I think i ended up on 9600). I seem to get data that is constantly broadcasted, doesn't seem like I can't request anything specific though. I can't tell what the data is, converting to int doesn't give me anything that looks like the battery or cell voltages. But interesting that one of the values spells out LBSACOZA (lithiumbatterysa.co.za) when converted to ascii, so looks like the data is being read correct, see attached image. @Schallas, your code seems to use Rs485, not canbus, but I think the Rs485 hat that you have on your PI runs in full duplex and this is why your code never gives me any values back. My hat is half duplex and I have to switch a gpio pin between sending and receiving. I also found I get more data back if I send with baud rate of 9600 and receive with 28800. However, the data I get back fails the checksum and most of the times I don't get the full 13 bytes back. Even when I do get 13 bytes back it doesn't look anything like I expect. I suspect that after requesting data by sending the bytes to the BMS that I miss some of the data transmitted by the BMS as my code is still busy switching to receive and changing my baud rate. I'm not sure if anyone knows a better way of doing this with half duplex?

Hi Schallas, I bought this but am struggling to get anything from RS485 or CANBUS after wiring up to Daly (A to A, B to B, Can-L to L, Can-H to H): https://www.robotics.org.za/W14882?search=485 I'm not sure if I should attach the ground from the Daly to the ground of this board, which I think is the ground of the Raspberry Pi, I was worried about something going wrong and it killing my Pi, which is why I haven't connected it 😕 I don't have a /dev/ttyUSB0/ but the Rs485 examples from Waveshare for my hat use /dev/ttyS0/ so I'm not sure if I should be able to just change this reference in your code and mine should then work? I also tried the Can examples for my hat and did get some reading back when calling can0.recv(10.0), but nothing that looked useful. Just wondering if anyone can shed some light on this, maybe I just need to connect the ground from Daly to the Pi ground? Thanks.

Awesome, this looks great. I've ordered a RS485/CAN PI hat from Micro Robotics, maybe the same as what you have, it passes through all the pins. Useful as I also have some relays etc that I need to operate from the PI (one of which, in summer, switches on a submersible pool pump to heat water on my roof depending on the temperature difference). My inverter sometimes spits out dodgy data or hangs/timeouts when I try access it's comms via usb. So I'm used to having to discard data (or move on if I don't get anything back) and then try again later Thanks again!

Thanks Coulomb, I'll take a look.

@Schallas Sorry to revive this old thread, but did you ever get the Daly working over RS485 to a Raspberry PI? I'm interested to know how you connected this up and any Python you wrote to achieve this Thanks!

I know my 63 amps circuit breaker has a breaking capacity of 6000 amps. I mainly went with the inline strip fuse as they look like they bolt down nicely, with very good contact to my lugs. Is there a type of ceramic or sand-filled fuse you recommend? I always thought the ceramic tube type fuses might not make a good connection in their holder (although I do use these on my solar panel strings). Yes, I understand, I should have clarified and said that I understand it's fine for at least a couple of seconds, I don't expect to overload it for any longer than a second or two

Well since I swapped out the fuse holder that was getting warm the battery voltage reported by the inverter doesn't seem to be going quite as low when the fridge kicks in, so maybe that made a difference. This is probably me just getting the terminology wrong. I've seen these fuse types names strip/flat/ane/anl/mega/midi etc, so I'm not sure what the correct name is for these with DC rating. I know that the National Luna fuse holder with 2x 100 amp fuses included that I bought was for "dual-battery systems" according to the packaging and most of their fuses are stamped 32V. So yes I believe it is for DC, however I will look at replacing it with this 60 amp one from Mantech since you said that the 60 amp fuses will be ok overloaded 100% above the rating : https://mantech.co.za/ProductInfo.aspx?Item=14M3521

Thanks for the responses Coulomb. Yes, it doesn't do it for very long as I don't seem to pick it up every time the fridge compressor starts up (as mentioned I only log every 15 seconds). I had the fridge off for half an hour last night and when I turned it on the voltage reported by the inverter went down from 26.2V to just over 25V for about a second. So seems like it's just a brief heavy load. After this it settles to under 10 amps, until it turns off again. My watts calculation based off the shunt might be slightly high as I use the (voltage from the inverter) x (amps across shunt) and could end up reading the inverter a few seconds before the shunt. But I wouldn't expect it to be out by more than 10% and I'd expect at some point to see 2000W+ reported directly from the inverter, unless it doesn't pick up on loads that are briefly that high. Not really a big concern though. I thought maybe when there's a brief heavy load though it might report lower at the inverter than the voltage at the batteries (for about 1 second). I haven't really had a chance to look at the voltage reported by the BMS when the fridge kicks on, but this is what I'll check next. Thanks, that makes me feel more relieved about my setup, I was worried about those peak loads blowing the 60 amp fuse. I've actually changed the fuse holder, even though my old fuse holder with moulded in cable was supposedly rated for 60 amps its cable was getting quite warm even when charging at 20 amps and seemed to be a bit thinner than 16mm2. So I bought a fuse holder at Outdoor Warehouse that takes those strip/flat fuses that NationalLuna and LittelFuse etc make, but I couldn't find a 60 amp fuse available locally so went 100 amp. Guess I will have to order from Joburg, or just move up to 25 or 35mm2 cable

Hi, I have a 24V Mecer (Axpert) inverter which I've only recently hooked up to my fridge. Before I did this I ran the fridge on mains and used a power meter to determine that when running it used around 160W and about 1.8kWh a day. However, now on the inverter, when the fridge kicks in I've noticed loads of over 2100W, calculated based on almost 80 amps being measured on the shunt to my battery bank. I haven't seen such a high number on the load reported by the inverter itself, only 600W and a bit over 1000VA at the same time with the battery voltage reported by the inverter dropping below 24.4V (and then bouncing back to 26V+ straight after). I measure/log my shunt and inverter values every 15 seconds, but these are the highest loads I've seen so far. I only have 16mm2 cable to my battery bank and originally had a 60 amp fuse (since when I originally set up my system 2 years ago I never used more than 40 amps) and a "C characteristic" 63 amps DC circuit breaker. I've since switched the fuse to 100 amp but have left the circuit breaker as based on its technical specs it should be ok surging to even double its rating for around 10 seconds. I had been a bit concerned that if it did trip that the inverter might be damaged since these Axpert type units apparently can get damaged if they are connected to solar panels with the battery disconnected. So I'm just wondering, is such a high load normal when a fridge kicks on? And is the battery voltage read by the inverter actually correct? Or is it likely that the there are losses along the 1 meter+ length of cable to my battery when the fridge kicks in the inverter is under-reporting the real value at the battery bank? Should I be concerned about my cable/fuse/circuit breaker choices due to these surges? Thanks in advance!

Only getting time to look at this now, thanks for sharing

After the first night pulling around 2 amps continuously, the cells were all around 3.18V. Was sunny and they started charging at a bit over 20 amps, falling to 12-13 amps later in the day, but the voltage of the highest cell never got much over 3.35V. They charged around 80Ah, so the cells I got for my 200Ah battery pack must have only been around 50% charged when I got them (which I believe is normal). While charging the difference between the highest and lowest cell went up to around 15mV, but the BMS seems to be set up to balance only when it's over 50mV. Last night the difference went down to 5mV. After another night of a 2A load, this morning before charging the cells were around 3.28V. I'll probably increase the charger settings by 0.4V, so 28V bulk and 27.6V float, which is more inline with (as GreenMan said) taking Coulombs values and dividing by 15 and multiplying by 8. Hopefully this will get the cells closer to 3.45V, which is what I'm aiming for.

Just to add, voltages of the batteries were between 3.261-3.268v on arrival (only 2 of the batteries were below 3.265). Here are the settings on the BMS, if you guys think I should change anything:

Thanks guys, @Coulomb, I found this quite old post where you approved of 27.6 absorb and 27.2 float for a setup similar to mine: This is what I've set mine to for now. @GreenMan, thanks, yes, I thought no equalise, so I turned it off. Also only set it to 30a maximum charge for now while I get used to things. My loads are quite low (and DC only) at the moment and I will only start using it properly next weekend. Haven't changed any other settings yet from my old settings for lead-acid (and the inverter is still in standby), so don't expect them to drain too low overnight. I only set up my batteries late this afternoon, so only charged a little bit, but will keep a close eye on the cell voltages tomorrow. Thanks again!

Ok, so how do I set up the Mecer and Daly to achieve that? Would I just need to set up voltages for absorb, float, equalise etc on the Mecer to apply the correct voltages for the Daly BMS and what would these voltages be? I saw there was a thread from a bit over a year ago that @Coulomb assisted with, but I'm not sure what the final settings were that worked 😕

Just to add to this, they are LiFePO4 cells

Hi, hoping someone can help me setup my Daly BMS with my 24V Mecer (Axpert) inverter/solar charger (SOL-I-AX-3MPLUS24). I bought this last week, but didn't come with any documentation other than a very basic connection diagram: https://lithiumbatteriessa.co.za/collections/diy-kit/products/24v-200ah-8s-daly-smart-100a-bms-lifepo4-lithium-iron-phosphate-diy-kit-new-a-grade-cells To start with I plan to take the batteries, check their voltages and pair up the ones with the closest voltages (since it's 2p8s). I've found some good videos on youtube on connecting up the batteries to the Daly BMS, so I don't think I'll have any issues there. Since this is the smart version of this BMS, it comes with the touchscreen and bluetooth etc, so first question is will I need to configure anything on the Daly BMS itself? When it comes to my 24V Mecer (Axpert) inverter/solar charger what setting do I need to change for absorb, float, equalise (and equalise period - every 30 days)? At the moment I think I have 28.5V absorb and 27.4V float. Also, where do I put the temperature sensor for the BMS, is it supposed to read the battery temperature, or the ambient room temperature? Thanks in advance

I was wondering if anyone had a link to a study of LiFePO4 batteries and differences in their capacity under light loads compared to heavier loads? I know LiFePO4 capacity is often stated at 0.5C, but what about at 0.1C? Thanks!

The guy who runs the powerforum store told me (at least for the 24V version) that it had been withdrawn from supply due to quality issues and when later I thought he had it for sale again he called them "untested". He also told me over the phone that they were 2nd life batteries. So based on that and what you say, it doesn't sound like a good option I'm still trying to find reasonably priced LifePO4 options for a 24V setup. I was about to buy from lithiumbatterysa, but with insurance and shipping to Cape Town it adds R 2000 to the price, which puts it over my budget. Would much rather buy something already in Cape Town, but struggling to find anything reasonable

There seem to be only a couple of concerns I could find online for adding more cells in parallel. That a faulty cell (shorted out) would lead to the multiple cells in parallel with it discharging into this cell causing a potential fire (although I'm not sure it would actually cause a fire with only 2 other cells in parallel and LifePo4 chemistry) and that you might need different charging settings for the BMS/charger if you have more cells in parallel (not sure what these would be in my case going from 2 to 3 in parallel): https://electronics.stackexchange.com/questions/431036/can-i-make-endless-parallel-li-ion-connections https://electronics.stackexchange.com/questions/161437/how-many-lifepo4-cells-can-be-in-parallel Ran into this while googling, which may be useful to people wanting to understand series/parallel battery packs: http://liionbms.com/php/wp_series_parallel.php

Yeah, I'm not going to be drawing more than about 1500W from my appliances and only then if I plug in the induction cooker or mini-oven. Thanks for the response, I was hoping some others might let me know what they think as well. I just don't want to spend R 20k and then find I can't up-size it if I need to I already felt like I wasted money last time on deep-cycle lead-acid, but a few years ago options were more limited.

Hi, Hoping someone can help me size my battery bank as I move from deep-cycle lead-acid to Lithiums. On my 24V setup on average I use 40Ah in a 24hr cycle, so about 1kWh. This is all DC and powers my security cameras, internet, laptop, DC water pump, 12V lighting. I am wanting to add a fridge that uses 1.8kWh as well as my TV, which I estimate 1kWh (TV is set to a power saving mode, but is on most of the time when I get home at night). So 2.8kWh total on AC (I got to these values using a power meter on the mains). I have a 24V Mecer/Axpert 3kVA (SOL-I-AX-3MPLUS24) and I already know the inverter uses a bit over 20W with no load attached, but what % will I need to add to the 2.8kWh to allow for inefficiencies in the DC to AC conversion? I was looking at the lithiumbatterysa diy kit: https://lithiumbatteriessa.co.za/collections/diy-kit/products/24v-200ah-8s-daly-smart-100a-bms-lifepo4-lithium-iron-phosphate-diy-kit-new-a-grade-cells This works out to 4.8kWh (with 100% DoD), but I'm not sure it would it be enough with allowing for the occasional rainy/cloudy days and not draining it fully? My load over 24hr would be at least 3.8kWh total for DC and AC loads, excluding inverter inefficiencies (I have just over 1500W solar array). This kit seems to be connected 2p8s, however I asked if I bought 8 more batteries for additional capacity, could I arrange it in 3p8s. They said it was not recommended on the included Daly BMS. Assuming that's correct, then is there another BMS I could get that would support this arrangement? Thanks in advance!

Thanks for the replies Coulomb. Just to let you know what I did after my original post. As I said, I removed the 6 deep cycle batteries that were now very low voltage and connected 2 charged batteries that I had removed a few months ago since I suspected they were no longer usable. After the sun went down their voltages also dropped off quick. So I had to quickly put 2 of the 6 batteries I had pulled out the night before, that seemed to have the highest voltages after resting for the day, onto a separate 12V charger and once charged swapped them in. They seemed ok overnight, so then I took the 2 with the next highest voltages of the 6 and charged them the next day and added them to the array that evening. After going from 6 to 4 batteries the voltage is higher overnight, so it seems the battery bringing the whole array down was one of the 2 I've removed. I've charged these as well and will see on the weekend if it's just one of them or both that are dead. I'm glad to hear that I can still use my unit, and I haven't heard that high pitch buzzing again so the unit seems to be working ok. I do plan on carefully opening it at some point to take a look and I'll post pics here when I do that. I gather it's out of warranty since I've had it over 2 years now. Thanks again.

Hi all, Last night my 24V Mecer/Axpert 3kVA (SOL-I-AX-3MPLUS24) popped while charging from mains. I known my batteries desperately need to be replaced, and last night the voltage was dipping quite low, even with only a couple of amps being used. So I plugged it into the mains to charge the battery and as usual the fans spun up and about 20 amps was being pushed into the batteries. A minute or two into charging I started to hear a slight buzzing should along with the fan noise that I had never heard before. Then pop, a flash came out of the right-hand side on the inverter and the trip switch for the plug tripped. However the unit didn't turn off and didn't show any error code on the screen. I wasn't going to try charge from mains again, so I disconnected it from the mains and also switched off the breaker to the solar panel since I didn't know what would happen in the morning when the panels would get sun. Overnight the battery voltages went very low and eventually the unit turned itself off. When I got up this morning I swapped out the deep-cycle batteries to some charged ones that weren't being used and switched everything back on again. The unit turned on and did its start up sequences, fans on, inverter on and then into standby like I usually have it operating (I don't use the AC output much, so leave it in "sense" mode most of the time). I switched on the breaker to the solar panels and the batteries (which were already mostly charged) went up to over 28v as normal with 1-2amps coming in. But a quiet somewhat high pitched buzzing noise started inside and gradually got louder until the loudness stabilised, but the pitch kept varying up and down randomly. The inverter was still on standby, so pulsing and not running fully and the noise continued even when I flipped the solar breaker to off. There were no error codes on the screen of the unit. I switched off the whole unit and the noise still continued for a few minutes and then abruptly stopped. After leaving for a few minutes after that and then turning on the unit again, the noise did not start again and the unit seemed to be working fine. So has anyone else had something pop in these units when charging from mains with this unit and what could it be? Any explanation for the initial buzzing (I thought initially it was an inductor with a loose winding but now I'm wondering if it's a faulty cap)? Is it safe to keep using the unit to charge my batteries and maybe run the inverter if I'm not going to connect it into mains again? Thanks in advance!