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Author Topic: Grid Hopping  (Read 88035 times)
nowty
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« Reply #180 on: May 29, 2020, 11:07:22 PM »

Nickel2, I presume you donít have a datasheet for your battery ?
I am making an assumption itís an 8 cell LIFE or LIFEPO4 battery with a nominal voltage of 3.3v per cell which gives 26.4v.
If so, 22v will be down to about 5% or less. Shocked

The datasheet below is for a LIFEPO4 cell, so you want to make sure you are stopping discharge BEFORE the voltage goes off the cliff, not half way down it.

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12kW+ of PV installed and 60+ MWh's generated.
Home battery storage of 40+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage of 15+ kWh's.
6kW Ground source heatpump.
EV BMW i3 (another 30+ kWh's of storage).
290,000+ litres of water harvested from underground river.
Nickel2
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« Reply #181 on: May 30, 2020, 11:00:43 AM »

Hi Nowty, thanks for your reply. As you suggested, no manuals, can't find anything on the net either. The actual cells are 15Ah each,  the same physical size as headway 38120's configured as 8S-7P. I was given two packs, each of 8S-5P plus 4 spares, neither had any attention for two years. One pack had 26.4V residual open; the other was dead. I stripped both, did some measurements and tried putting 5A into each for a few minutes to see if they were still viable. 40 of one pack were ok, so put to one side.
The other pack cells were individually given 5A, just to see what happened; some got a warm area of the case so were put aside. Some took 5A but sagged to 0.0V as soon as the current was removed.
By nursing 16 of them, then exercising them I managed to get enough for a 8S-7P block, ie 26.4V @ 105Ah. The tinny coupling-plates were replaced with 1.6mm brass, (old door finger-plates), suitably cleaned after cutting to shape.
I have set the EpEver 4210A MPPT as per the screen shot.
So, here's some pics:










« Last Edit: May 30, 2020, 11:26:30 AM by Nickel2 » Logged

1.140kW mono south-facing at 49*
EpEver 4210A at 24v
New (Old) 8S7P LiFe battery, 105Ah @ 26.4V
EpEver STI1000-24-230 pure sine inverter
Of course it'll work. (It hasn't caught fire yet).
Nickel2
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« Reply #182 on: May 30, 2020, 11:06:48 AM »

Hi Scruff, thanks for your steerage in the right direction, I have downloaded and read multiple times to sink it into my brain. I have set lowest volts to 25.7 as per your suggestion.
I'm just mental-penciling out an idea that enables me to use the BMS that came with the batts, so that when the battery reaches voltage it doesn't remove the reference 24v from the MPPT and cause some variety of disaster. It will involve the use of stud rects, a stud Schottky lump, and a pair of UPS agm batts.
The poor cells that had suffered a traumatic experience of some sort will be nursed to see if any recover, as I'd like at least 2 spare. (there is a smelly incontinence going on somewhere in the pack)



« Last Edit: May 30, 2020, 11:44:27 AM by Nickel2 » Logged

1.140kW mono south-facing at 49*
EpEver 4210A at 24v
New (Old) 8S7P LiFe battery, 105Ah @ 26.4V
EpEver STI1000-24-230 pure sine inverter
Of course it'll work. (It hasn't caught fire yet).
Nickel2
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« Reply #183 on: May 30, 2020, 02:07:40 PM »

The 'pack' reference was more similar to 'rat-pack' rather than carry it about on one's back pack. Grin
I went out first thing and measured each cell-set and they are sitting happily at 3.29V each, from the fully-charged 3.3V per set. Basically it ran the PC/monitor/radio load of 110 W + Inverter quiescent of 10W for 4 hours til bedtime, then only Inv + radio overnight til dawn, ie dropped 10mV with the overnight load. With the sun back out, they are sitting at 3.29V each set, so neither giving or taking power.
I'm not actually 'floating' them, just not takin power from them by maintaining the idle off-load voltage.
I've had a sniffle around the wshop, it's the duffers that are the partly smelly jobs. I think I'll wash and dry them, leave them to really dry, then start nursing. I've already marked several tyhat get warm with 3A for 1 minute, so they are deffo scrap. Of the sickos, 2 of them hissed when voltage applied, so they live outside until disposal. Several are short = scrap, some are O/C =scrap. If there is one or two that can be eased back into life, then gently cycled, I'm hoping they may be saved, otherwise, scrap!
I am continually monitoring progress and adjusting preset voltages as required, see 'duff cells pic earlier'.
« Last Edit: May 30, 2020, 02:30:48 PM by Nickel2 » Logged

1.140kW mono south-facing at 49*
EpEver 4210A at 24v
New (Old) 8S7P LiFe battery, 105Ah @ 26.4V
EpEver STI1000-24-230 pure sine inverter
Of course it'll work. (It hasn't caught fire yet).
nowty
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« Reply #184 on: May 30, 2020, 05:53:24 PM »

Charging settings I use are a constant voltage so I set both the Boost and Float voltage the same to the target voltage you want and then it does not matter how much time you set the absorption phase for. The current will then tail off as the target voltage is neared. The other setting is to set temp compensation to zero as lithium does not need it. Then disable EQ charge or if its automatic and you cannot turn it off, try and set the EQ voltage same as Boost / Float if it lets you. If it does not then set EQ to the smallest increment above the Boost / Float setting and for the smallest amount of time.
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12kW+ of PV installed and 60+ MWh's generated.
Home battery storage of 40+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage of 15+ kWh's.
6kW Ground source heatpump.
EV BMW i3 (another 30+ kWh's of storage).
290,000+ litres of water harvested from underground river.
daveluck_uk
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« Reply #185 on: May 31, 2020, 09:45:52 AM »

Should I bother demonstrating lead do as well for the same investment but with much more capacity?

Yes please! I for one would very much like to see the comparison and I'm sure there are many on the forum who would too.

(This is such an incredibly interesting thread.)



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stannn
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« Reply #186 on: May 31, 2020, 10:38:28 AM »

Another yes Scruff. By the way, have you seen Robert Murray-Smithís latest video, Making a Battery from Mud?
Stan
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2.45 kWp PV (Navitron supply), 40 evacuated tubes (Navitron supply), Clearview 650 log burner with back-boiler heating cottage and water, 2 off 50W border collies, 1 off 35W cat, 1 off 25W cat.
biff
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« Reply #187 on: May 31, 2020, 12:39:11 PM »

Yes, Go for it Scruff
      Biff
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An unpaid Navitron volunteer,who has been living off-grid,powered by wind and solar,each year better than the last one.
jonesy
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« Reply #188 on: June 02, 2020, 11:19:54 PM »

I couldn't see the li  Ah anywhere. Is it the same as the LA
If you fitted some decent battery cables instead of that junk ebay 'copper'  Grin that acts as a 130W heater, you'd  squeeze ~7% more efficiency. 12V systems suffer badly with volt drop at high current. More of a 48V man me.
Fancy doing a very quick check at no load, 300W and 600W. Inverters are generally poor in real world situations where they idle most of the time.
Good test method.
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1.1kWp PV & SB1700. 7kW log burner.
biff
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« Reply #189 on: June 04, 2020, 11:29:41 AM »

Interesting stuff Scruff,
                    I gave up on trying to save my No2 100ah Yousa, Too much effort involved, the success ration is now down to 1 out of 4  Cry
        I remember trying this years ago and thinking I should have baked a cake with the powder instead.
                                    Biff
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Tiff
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« Reply #190 on: June 04, 2020, 08:14:05 PM »

^^^ That 25mm2 was Aldi bargain jump leads. 6m for Ä25 iirc.

It's actually 35mm2  Grin Grin Grin

I once bought some jump start leads in a supermarket, they were reduced to something like £3 and a quick peek in the box showed some chunky looking cables. So a bought a couple and thought I had some nice cable that would come in handy one day. That was a few years back.

A couple of months back I had a need for a short length of thick cable and thought one of the jump start leads would do the job nicely.

As I picked up the cable to cut the clamp off the end I thought they felt a bit on the light side. Cutting the cable confirmed it was copper coated alumininium, still did the burn test just to be sure!

Not such a bargain after all.
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biff
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« Reply #191 on: June 20, 2020, 08:14:47 AM »

Is their any other method Scruff.
   How about the 30 second tongs with the meter on them.
   Garage men used to take them out to test the battery in the days of the dynamo.
        Biff
         
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An unpaid Navitron volunteer,who has been living off-grid,powered by wind and solar,each year better than the last one.
Countrypaul
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« Reply #192 on: June 22, 2020, 12:06:11 AM »

You've put that white box at the wrong side of the window - means you can't see out whe you enter the doorway. If there isn't enough cable from the otherside to reach the 13A you could always use an extension lead  hysteria
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A.L.
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« Reply #193 on: June 22, 2020, 04:25:46 PM »

hello,

If anyone has any bright ideas how to convert this horsepower into electrickery I'm all ears.
Decent flow, low head, we own 50% across the middle. Discrete options only.

legally to many problems, also probably very low output (l/s x 9.81 x head in meters gives output in Watts) likely no more than 50% efficiency, sorry.
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