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Setup for 2 battery types
#1
Hello All
I am currently running 48v 2 x 14s72p diyPowerwall, epevers 50A charge controller and 3kw inverter.
i have come into some AGM lead acid battery which i can make up to 48v and build up to larger bank then the DIYpowerwall

Now i am wondering how to set them up as i have 2 different battery chemistry.

I know i could set up 2 systems and run them into different parts of the house. i just wondering is there other ways i can set up the second battery type and put them onto the same busbar and send them to the same inverter. 
I know i am going to need a 2nd controller, i prefer not to get a 2nd inverter.
I do have some ideas, just need to put them on paper, wondering what others thoughts are.
Thanks
Andy
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#2
I thought, it was possible to have both chemistries at the same 48v line/inverter but both with there own bms and charger.
To avoid one chemistry is drain to low there must be a cut off for that bank.
From my experience(or simple luck!) i can tell that my agm batteries where quite forgiven, several times discharged to 10v.
More people will chime in for sure
Best
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#3
You can't really mix chemistries easily. The only way to do it would be to use massive buck converters between the battery banks and the common inverter. But this isn't feasible in the long run.

It'd be better to utilize the PbA's in their own circuits and keep them separate from the Lithium system. UNLESS! your inverter can take 2 different battery inputs. Then the inverter handles the hard/difficult work.
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#4
Beyond the comments above, perhaps you could do a switch (manual or ATS) so that when one battery bank goes low you switch over to the other. You'd have to have to think thru the daily charge/discharge cycle - e.g. reset this each day kind of thing.
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#5
You could use a Dual Battery Isolator , either manual or auto but finding a 48v Dual Battery Isolator relay could be hard. Manual 48v Dual Battery Isolators are available.
48vdc is 48vdc the voltage range is different. Since he would have different charge controllers hopefully he could set the upper and lower voltage on both banks the same.

Later floyd
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#6
You loose alot of capacity and so doing it. Your better of running Them One by One or just selling the la batteries in favojr for lithium instead
Korishan and Ibiza like this post
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#7
Photo 
Thanks for everyone thoughts. 
(If was i able to get/afford 140kwatts of 18650's here in Australia, we are so backwards here on e-recycling, I wouldnt need to go the cheaper route of getting AGM's)

I will be speaking with my auto electricians about dual battery system and see if i can find one that is 48v dc.

I also had a further thought and come up with this schematic, i am not sure if the diode's will be needed. I am just concern about when the AGM controller goes into equalization, my understanding this will push it up close to 64 volts.
Does it look ok or am i going to blow something up.
Thanks
Andy
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#8
Pete from HBPowerwall & several others are located here in Oz & have sourced & built large 18650 powerwalls, so cells are available.
If you're in a hurry, you could look at buying LiFePo4 prismatic cells.

Like others have said, mixing LA & Li-Ion isn't a good idea - it won't end well because the voltage ranges & useful SoC are too different, the SLAs will quickly die (<12 months) if they get cycled >50% DoD &/or charged hard.
You can't charge SLA's as fast as Li-Ion only 1/10C amps typically vs Li-Ion which is fine with higher current charge.

Issues in your diagram:
With the contactors closed, assuming both types of batteries are in parallel at the busbars, one charger will dominate & charge to a higher voltage, overcharging the other side. The diodes & other contactor even if it opened are not going to help, might as well just have one.

If you really want to keep the LA's you'd be better to split system in half, Li-Ion only in one half + LA only in the other with a 2nd inverter for the LA side + split your loads between them (ie separate 240V circuits).
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