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NighPV - Batteries to use our solar power at night
#11
(11-12-2019, 08:28 AM)enki Wrote:
(11-12-2019, 05:38 AM)ajw22 Wrote: Generally, sharing batteries between inverters is not a problem, even if they are on different AC phases as the batteries are fully isolated from AC and Ground.  Unless of course the manufacturer states otherwise.  And best to consult a pro on this.
Certainly not wrong to use separate batteries, but you may(will) have some inefficiencies due to having too much/little energy stored on the wrong phase/battery.

If you have 3 phase net metering on the grid connection (which is very likely for the OP having PV and living in Switzerland) you can just connect the battery to a single phase on-grid inverter to any phase you like and the energy meter should still correctly account for the energy you produced. The 3phase net meter adds up the energy flow for all phases.
enki, this was very helpful!!
I just checked the power bill and phoned with my power grid provider. Looks like I can run the battery on just one phase as you mentioned and the meter will be calculating if I have excess power or lack of.
So as long as I don't want to go completely off-grid, I can at least on the cost side minimize things even with a single phase system Smile
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#12
So another process update:

Love it, if a plan works out well! The plan:



Basically the idea was, to have two bus-bars. I use solar bus bar (pre-tinned copper, used to lead the electricity inside a PV module to the connection box). Those are rated for 10A continuous (in a laminated environment). So in free-air use I should be on the good side with 10A aswell. 
First I solder short nickel strips to the busbars. I made a simple template for that. Then the strips can be spot welded to the negative side of the cell. Since leaks normally occur on the positive side (seal is there... except you pierce the cell mechanically or it suffers from really heavy corrosion) I want to make sure to have good visibility of the positive cell terminals, this is why the fuses went there. Fuses are also spot welded. 
The welder is made from two old lead-acid car batteries (one for welding, the other one to power the coil of the large 500A golfcart-solenoid and the arduino based timer, helping me to get consistent welding times. Aw, yeah, I made a 16cell pack for starters - just some of the worst cells I had around for testing... around 85Wh all together approximately...
Pictures of all the mentioned details below...


template to solder nickel strips to busbars


negative connectors soldered & ready to weld


welding test, fuse on defective cells


the welder... Smile



positive side soldered & ready to spot weld


negatives welded (was definitely on the hot side... must turn further down next time...)


fuses welded aswell...


finished test pack... Smile
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