shadowmaker
Solar Addict
Well, I am dumb as left foot rubber boot, so I'm thinking of using their BBMS.
My 44kW vertical and bifacial set in Finland.
- Thread starter shadowmaker
- Start date
Thanks for that - I learned something new today!
Also, I don't fully agree with what he says about lithium charging.
Edit: are those FLA's you have? In that case, you might have an issue. A 48V FLA sits at 50.58V when 100% charged. At that voltage, you're at 3.16V per cell with LiFePO4 which is way too low. Typically, 3.6V per cell LiFePO4 '48V' pack sits at 57.6V. That's way too high for FLA and will cook them. So the principle he describes won't work for your set-up if they are FLA. With AGM you're typically around 58.8V, or 3.675V per cell if it were LiFePO4 - too high, but they're much closer to one another and if you shut down charging like he describes, yes, you can get away with it.
Personal opinion: don't mix chemistries.
Last edited:
shadowmaker
Solar Addict
I understood that the whole point of their BBMS is to have two overlapping voltage ranges. LFP ranging 48-55,2V (cell voltage 3,0-3,45V) and FLA 48,28-50,58V (50% to 100% SoC). With their gadget you start by charging both at first, but after FLA gets full, it disconnects from charger and you continue charging LFP only. I don't think it is going to harm LFP in anyway, but FLA can suffer if there is no absorption or float (don't know if there is, haven't read that much). In any case I think I could be able to add some "lead acid" features to it myself after FLA disconnects from charger, if needed.
There's still a long way to get everything working, even without any batteries connected. BBMS is not top priority just now.
Looking from stable window, a lot of energy was wasted today...
In the video he said it would stop LFP first, and then keep charging the lead acid (iirc) because lead acid needs a long absorption stage. Anyway, it's been a long time since I've dealt with lead acid so I could be all wrong; maybe these ones you have are fine at 58V.
Bluedog225
Texas
- Joined
- Nov 18, 2019
- Messages
- 3,103
Sounds very cool. I wish the pics would show up. Are they working for y’all?
edit-disregard. They came through.
edit-disregard. They came through.
Last edited:
Off topic, isn't it great we see the sun again
shadowmaker
Solar Addict
I have to read a bit more and watch their videos, but actually I just need a reliable contactor that disconnects FLA from charger/LFP at certain voltage level charging up. When discharging connecting needs to be done at the same voltage level and both can use the same low voltage setting of 48,28V (=LFP@3,018V). FLA absorption and float (and equalization) can be made by totally separate charger while disconnected.
Off topic it is great, but on topic I hate that just now. It feels I'm loosing money every time I see sunshine until I get my system working.?Off topic, isn't it great we see the sun again
Bluedog225
Texas
- Joined
- Nov 18, 2019
- Messages
- 3,103
Come on down, we can give you all the sun you want. Summer sucks.
Sverige
A Brit in Sweden
That’s definitely how it is designed to work - I looked into this device when it first came out but decided it was not going to be useful to me. Still have a couple of relevant pages of the manual saved:
shadowmaker
Solar Addict
That's not going to work with my FLA. Can't see the point disconnecting LFP as it has BMS to take care of that in it. It would be really hard to really misuse LFP. Maybe I could make their BBMS work by using it "wrongly".
Sverige
A Brit in Sweden
The guy behind the product used to be a member here, but when I try to tag him I draw a blank, so maybe he left the forum. Nonetheless I know he’s pretty engaging and a smart fella, so would no doubt try to help if you contacted him via his YouTube comments.
Someone really needs to come out with a generic bidirectional DC/DC charger which can sit between a lead acid and LFP bank and keep them both in their happy place. Some of the new Seplos server rack style batteries have this built in but I haven’t seen an off the shelf version yet.
shadowmaker
Solar Addict
Some progress.
shadowmaker
Solar Addict
There's a new video about BBMS that was published yesterday.
I like everything else in this video but to stop charging at 100% at the start of LFP upper voltage elbow. Although it is fine capacity wise as you really don't gain much Ah going further/higher to that voltage elbow, you still need to go over 3,4-3,5V to get cell balancing started by BMS. I think that is critical in the long run.
I like everything else in this video but to stop charging at 100% at the start of LFP upper voltage elbow. Although it is fine capacity wise as you really don't gain much Ah going further/higher to that voltage elbow, you still need to go over 3,4-3,5V to get cell balancing started by BMS. I think that is critical in the long run.
Last edited:
Sverige
A Brit in Sweden
Having read the pinned comment thread in the comments section of that video I’m fairly sure this product has been designed around a faulty understanding of how lithium batteries should be charged, because if Clark who designed it and who has chosen to pin it at the top of the comments agrees with the pseudo science user Conrad Grillo is coming out with, he’s trying to solve problems which don’t exist IMHO.
shadowmaker
Solar Addict
I did that too and also read some parts from the manual. Fortunately you can choose how to stop charging. You don't have to use upper voltage elbow (I think that might be the pseudo part of this gadget). Instead you can use normal voltage setting. Also I think it is essential to have a big lead capacity compared to LFP, so that LFP charges up first and gets disconnected. Then slower lead continues from that. I think this would work with my system with 30kWh lead (15kWh usable though) and 3x5kWh=15kWh LFP. The other Deye gets 60kWh LFP only.
shadowmaker
Solar Addict
Going slowly forward with solar corner installations. Main electric panel is about 70m from here so this only half of the work needed. Plus the solar array needs a lot of wiring too and some of it is 5m high. It's -20C outside, so working inside...
Scrapyard busbars ~10m (alu 80x10mm) 40e.
Scrapyard busbars ~10m (alu 80x10mm) 40e.
shadowmaker
Solar Addict
Well there is one meter of small copper busbar in the picture, but that's all they had at the moment. So going to use alu instead.What? No copper? Perkele...
Have to respect anyone capable of expressing the inner most feelings in Finnish language... Saatana! ?
shadowmaker
Solar Addict
It was the years of famine here and over one tenth of the population was killed. For many it was either get out or die.
On more positive side, you are free from the cold winters. On the negative side, I'm not...
Similar threads
