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LTO Powerwall
#31
It's my : Voltage Averaging Negating Differences at All Locations unit

VANDAL unit... cross connecting it the wrong way and it will wreck everything. "VANDAL, destruction with style" Big Grin
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#32
LOL

[Image: giphy.gif]
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#33
Finally have all 15 packs connected and around 13kWh of charge in them at the moment. Display unit is good for +/- 0.15V accuracy, mainly useful for wiring up the packs to get the connection sequence right and prevented me from cross wiring a few times.
 

Have ordered a separate 7-24s balancer that I intend to use to pull the 11s packs into line and use for the portable mode from a temporary hook up board to use while in the middle of nowhere.

Offtakes for two 3000VA UPS units, 12V fridge connection and 12V LED light arrays. Still to add some connectors/plugs and switches.
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#34
Well, project took a bit of a turn after being electrocuted off the case of one of the UPS units. Turns out the case is now live with 120V (240V normal output, will investigate further...) so all three units are going back after a not so polite request to the seller. That removes a big part of my rationale for staying with 72V so now I will be re-configuring the packs into 48V, which should take around 30 minutes :-)

My conclusion so far is don't use 72V for a pack design, never.... go 48V as it is well supported and only 96V if you need a large sustained power output, i.e. sustained above 5kW for hours. 72V is great for EV and eBikes but very big lack of support for renewables and any powerwalls. Off the shelf BMS systems for 33s upwards are few and over half of them are not really designed for large packs.
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#35
ouch I hate the AC buzz.
******Hi My name is Jason and I have SOCD (Solar Obsessive Compulsive Disorder)*******
Current Powerwall - 1400 Cells 7s200p (modular 40p packs) ~ 12kWh of storage     4x 315W Canadian Solar Panels

Working on the next 7s40p packs     ~2.5kWh

Waiting on 2000 Cells of unused Sony vt4 (2000mah 30A) ~ 15kWh      hehehehehe  More Power
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#36
Dang, that sucks. err, I mean, that stings Tongue Glad to see you are ok, as you returned and posted a reply and we can actually read and understand your post Wink

I've been nailed by 120V a few times. Not a fan of it, that's for sure. But at least you can pull away from AC zaps. Much harder to do so with DC.
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#37
Only a slight tingle compared to the 240v whack I had while talking to a customer hot working a distribution board years ago.. I think the customer thought I had something wrong with me, hahaha.

Found out the issue, or at least part of it. Reminds me of the inverter wiring with mike...

With the UPS when it switches to battery mode it disconnects the neutral line output from the input (or that pole in the relay has been blown away in a previous fault), which then leaves it floating and with a small amount of leakage from something this then makes (or tries to) the battery negative rail -113V relative to ground. Then, with my charger units connected and switched on which are mains powered and a continuous neutral/earth line to the battery pack the battery negative rail is pulled to ground and the UPS case then rises to 113V with the live side at 230V. One of the most strange issues I have come across, fortunately the leakage current seems quite low.. and a reason to separately earth bond the case, even on a UPS where this should never happen !

Earth pin to case... 120V...


Funny bit is it took three twitches to realise the case was live as I could not believe it...
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#38
(06-05-2018, 11:05 PM)completelycharged Wrote: Funny bit is it took three twitches to realise the case was live as I could not believe it...

LOL Threes a charm! At least it feels like one! Tongue

Yeah, that is strange the UPS case was live. Agreed, that shouldn't have happened. I'm guessing like you said, the relay blew out or something. Or maybe internally there is a solder joint bridging connections or something.
Wait, does that mean that your plug doesn't have ground wire included? I would think 240 would be Hot, Neutral, Ground and Ground is always connected to the case, regardless of the UPS power mode. Or am I missing something here?
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#39
Ground from the input power lead is wired to the case, but if that is lost via hot switching the supply or a simulated loss of power with a cut cable... your case no longer has a ground and can then float up to whatever voltage. Internally looks clean and the current flow is not enough to trip the RDC devices on my supply (think it's 10mA) while it is plugged in so suspect it is some of the electronics failing and leaking to the internal negative rail.

I was switching to battery mode by pulling the supply cable out.... and with it the ground...
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#40
(06-06-2018, 12:16 AM)completelycharged Wrote: I was switching to battery mode by pulling the supply cable out.... and with it the ground...

Ahhh! Gotcha Tongue Maybe you should have a switch, instead Wink

Well, a loss of power wouldn't disconnect the ground. Even throwing every breaker to off wouldn't disconnect ground. So I think you'd be safe on that side of things. But, like you said, if the cable was pulled out for any reason, it'd float. I suppose you could run an independent ground line and screw it to the box of the power coming in. That way it doesn't accidentally get yanked out.
Or you could put a twist lock on that cable to secure it in place.
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