Dual battery system Li-ion & LeadAcid powering house

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Bradz estuff   10 mW

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Dual battery system Li-ion & LeadAcid powering house

Post by Bradz estuff » Sep 11 2021 3:07pm

Hi all,
I currently run my house on 48v battery system (lead acid) and recently got hold of a damaged Tesla PW2. I have repaired the PW2 and modified it to be a 13s config rather than the original 12s it came out the factory with. Its inverter has been completely removed so because of that its essentially just a 13s Li-ion big battery and does not operate in same way a normal Powerwall would.
I don't want to change out the working lead acid batteries as nothing wrong with them but I also don't want to let PW2 be un-used.

What I was thinking was thinking was to combine the 2 systems like I have drawn in my very rough diagram-
HOUSE POWER PLAN 2 of 2.jpg
HOUSE POWER PLAN 2 of 2.jpg (275.02 KiB) Viewed 75 times
So I want to combine the output of the 2 different batteries but due to different charge capabilities they will each have their own charge system that wont effect each other due to power only being allowed to flow in 1 direction from PW2 into the line that is then fed into inverter before being converted to supply house.

Obviously they would need to be at the same voltage when connecting them together so thats why the PW2 has been increased to be able to be at higher voltage to come closer inline to where the lead acid ones want to be operating.

Will this actually work and be useable like this or is there something I'm missing?
I realize this probly isn't something that lots of ppl have setup so anyone who may have some insight and more knowledge on power systems in general would much appreciate your input.

Thanks
IMG_20210504_190258.jpg
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ZeroEm   1 MW

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Location: San Antonio, TX

Re: Dual battery system Li-ion & LeadAcid powering house

Post by ZeroEm » Sep 11 2021 6:28pm

The PW2 can flow in and charge the LA batteries. Long as you don't charge the PW2 above them. They are connected all the time so it should not matter. Just wondering your running your pair of inverters as 220V correct?
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Bradz estuff   10 mW

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Re: Dual battery system Li-ion & LeadAcid powering house

Post by Bradz estuff » Sep 13 2021 7:01pm

So im right in theory then, I can hook them together providing they each have their own charge capability's that's great, its quite confusing when some sources say yes its possible yet others tell you no its defiantly not.

The 2x inverters are paired together (one master and 1 slave) with an add on pairing board added into each inverter. They are running 230v actually must have mistyped that if say 220v.
The reason they are linked is due to fact sometimes have big loads and thought better to have lots more capability rather than running close to limits.
watch power shot.jpg
watch power shot.jpg (165.45 KiB) Viewed 55 times

This what looks like before add PW2
IMG_20201225_091859.jpg
IMG_20201225_091859.jpg (4.76 MiB) Viewed 55 times

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ZeroEm   1 MW

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Location: San Antonio, TX

Re: Dual battery system Li-ion & LeadAcid powering house

Post by ZeroEm » Sep 14 2021 1:01am

by Bradz estuff » Sep 13 2021 7:01pm

So im right in theory then, I can hook them together providing they each have their own charge capability's that's great, its quite confusing when some sources say yes its possible yet others tell you no its defiantly not.

The 2x inverters are paired together (one master and 1 slave) with an add on pairing board added into each inverter. They are running 230v actually must have mistyped that if say 220v.
The reason they are linked is due to fact sometimes have big loads and thought better to have lots more capability rather than running close to limits.
To me 220V and 230V are the same thing. Just looked it up and shows my age. They don't use 220v its now 240V in the USA unless your in the UK then it's 230V.

I have never mixed battery's but as long as the Voltages are kept in check. Extra inverters for loads is great. Like the idea of having one if the other fails. I think about 240v and know one leg is out of phase of the other and was not sure how motors would react to just two inverters. I know people do it, have not heard any bad stories.

I need to setup my house, been dragging my feet. The power here was so steady for years but now it has taken a turn for the worse.
I need a hybrid system still working it out but things change.

Nice setup.
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Hwy89   10 kW

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Re: Dual battery system Li-ion & LeadAcid powering house

Post by Hwy89 » Sep 14 2021 6:25pm

Adjust the charge controller to stop at 52V on the PW2 pack. The cells will live a little longer by being charged to 4V instead of 4.2 and makes a better match to the lead acid packs. You will not notice the slight decrease in capacity. I would advise finding a 13S BMS and regularly checking the balance.
Now the legal jargon. In the event of a fire your insurance company would pin the blame on the lithium batteries no matter where in the house the fire may have started. They do everything they can to pin the blame on you and avoid paying.

Bradz estuff   10 mW

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Re: Dual battery system Li-ion & LeadAcid powering house

Post by Bradz estuff » Sep 18 2021 4:37pm

Yes that was the plan for the PW2 to not get up to max voltage (54.2v) hence why I increased it to be a 13s battery. If was a normal 12s battery then the lead acid ones not be able to get fully charged and I know that's not a good thing. I have an ant bms fitted to the PW2 that can be seen in the pic of it. Its the blue screen, Ive used them before and found to be quite good(the old version anyway) due to ability to auto equalize at any time.

Recently got a newer model ant bms for a scooter and they have updated the app so that it looks much nicer ect, the problem with the newer version though is it has lost the best feature about the bms and can nolonger do the auto equalize function.
Isnt it awesome when they try improve a product and remove the best part only to give you a nice shiny app that looks better to distract from fact its crap compared to the old one

The Lead acid batteries also have a balancer on them that seems to work although at this point they are always seeing some load so cant quite tell 100% if all are level without shutting down the hole system and letting batteries settle a bit. When all still in use the difference between batteries is minimal so seems to work fine

Bradz estuff   10 mW

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Re: Dual battery system Li-ion & LeadAcid powering house

Post by Bradz estuff » Sep 18 2021 4:48pm

As for your legal disclaimer I have also tried to address that possibility too, I have installed in each battery box a fire suppression ball thing. Its ment to explode when either too hot or any flames and completely smother a 2sqm area in a powder to extinguish any fire.
There is not much space in the battery boxes so it should more than extinguish any fire. Cant really fit one in top of PW2 as Elon didn't leave me enough room for one so maybe ill mount one on top of it or something.

I also have smoke alarm mounted directly above and extinguisher at back door of house just as a backup.

Because I set all this up myself I know what insurance ppl would say even though its all very much overkill with cable sizes and capability. Anything to blame someone and get out of their responsibility. They happily accept payment for while things are good but if have problem then anything can find they quick to try get off the hook

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