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Looking for ideas
#1
Hi guys,

my setup is now up and running.

My 3 Victrons are outputting 105 Amp when charging, which killed 3 out of 5 40Amp China-BMS because they can handle 40Amp when discharging but only 20Amp when charging. 5 multiplied by 20 is 100Amp in total... too much!

I will now switch over to 5 x 60Amp Daly BMS which should be able to handle 150Amp when charging, which shouldn't be a problem with the 105Amp coming from Victrons.

Next step is that I will add 16s 240Ah LiFePO4 in parallel. with 18650s. Managed by an AntBMS 300Amp discharge, but unfortunately only 50Amp charge.

I do worry that when Daly-BMS will switch off charging for any reason, full power is going into LiFePo4 pack with the AntBMS and this will die because of high current.

How would you handle this potential issue? Any ideas?

regards
Karl
30kWh 5x 14s80p with 5x40A China BMS. 14kWH LiFePo4 is in production.
1 x Fronius Symo 8.2 with 28 Jinko 340Wp panels east/west. 3 x Victron Multiplus II with Cerbo GX
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#2
Get a proper bms. One that can handle the load instead of bunch of smaller Ones.

You asked for advice Wink
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#3
My point is, that I would like to monitor 5 strings separately in order to find out when one pack becomes weak. having 14s400p will not be so easy to manage in that perspective...

I think going forward with diy bms on the basis of an esp32 will be the right approach. batrium or other bms systems will be too expensive.

What I don't know is whether diy bms can manage 5 strings 14s80p plus 16s4p lifepo... maybe some one can give an answer on that...
Can diy bms handle 6 relays (one for every string)?


regards
karl
30kWh 5x 14s80p with 5x40A China BMS. 14kWH LiFePo4 is in production.
1 x Fronius Symo 8.2 with 28 Jinko 340Wp panels east/west. 3 x Victron Multiplus II with Cerbo GX
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#4
(08-02-2020, 02:15 PM)Charly144 Wrote: My point is, that I would like to monitor 5 strings separately in order to find out when one pack becomes weak. having 14s400p will not be so easy to manage in that perspective...

I think going forward with diy bms on the basis of an esp32 will be the right approach. batrium or other bms systems will be too expensive.

What I don't know is whether diy bms can manage 5 strings 14s80p plus 16s4p lifepo... maybe some one can give an answer on that...
Can diy bms handle 6 relays (one for every string)?


regards
karl

Why don't you look into the diybms4 instead? That will give you monitoring and relays to kick off an external shunt trip breaker.
https://secondlifestorage.com/showthread.php?tid=8540

On one giant pack. My packs are linked together in 6x 60p to turn into a giant 360p so I only need to run one bms. If they do go out of balance then yes I will have to take some time disconnecting the interconnects but I should be able to zero in the bad cell packs relatively quickly. All this interconnects can be removed on a live system without disconnecting.
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#5
Maybe connect the three Victron chargers one each to separate battery banks?
Or configure the BMS to use an external switch to cut all or some solar panel output when needed?
Running off solar, DIY & electronics fan :-)
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