DIY Lithium

Derekoak

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It took a while but I have finally got an invoice and all questions answered and paid the invoice. The final invoice was for 8 number 100 Ah Basen cells @$35 and 2 number Daly 4s 100amp discharge/50 charge smart Bms with bluetooth @ $46 . With $168 shipping taxes and customs Total $540. This converted to pounds @1.362 was £395.01 I wanted to pay by credit card for security. my card gives 0.5% cashback there was a 2.95% fee to use a credit or debit card so it cost me £ 404.68.
Continuing to investigate my top balance procedure without a bench stabilised power supply. I believe I can get 5 of my 8 cells to near 3.65 volts by charging with my lithium option 12 volt charger and swapping out the highest voltage cell for a lower set. Having tested each cell with my new clamp multimeter or the Bms. The last 3 will be a little less. Then I plan to buy a step down buck converter, a suitable one costs less than £10. I can supply power to this from the 12 or 5 volt supplies from my old computer power unit. Then I adjust the buck converter to 3.65 volt and connect all cells in parallel and wait monitoring voltages. After 40 days or more shipping there is no need to rush.
 

Harryw

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I know Phil will do a more comprehensive test and report on this but after I left the conversation about discharging when the low temp charge Mos was triggered I did a quick experiment yesterday.
I set the low temp trip above ambient, thus tripping it. I then connected a load, only 2a+ I know, but still a discharge. The system detected the -ve current flow and let the discharge continue. See screen shots below;
24A9CF3A-85ED-4811-BFFC-430C0730400B.jpeg
9F4F2C73-B97F-48EB-BC1B-671A2B58280B.jpeg
 
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Harryw

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Whilst here, Phil where are getting the 1200/600 heat shrink tubing from, my google skills are not finding it...
 

Philip Tomlinson

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Whilst here, Phil where are getting the 1200/600 heat shrink tubing from, my google skills are not finding it...
 

Philip Tomlinson

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I know Phil will do a more comprehensive test and report on this but after I left the conversation about discharging when the low temp charge Mos was triggered I did a quick experiment yesterday.
I set the low temp trip above ambient, thus tripping it. I then connected a load, only 2a+ I know, but still a discharge. The system detected the -ve current flow and let the discharge continue. See screen shots below;
View attachment 95597View attachment 95598
I will do some testing.

FYI

All my cells tested over 285Ah on a calibrated discharge tester.

Between fully charge and a 12v reading (whilst under a 10A load) the cells tested a little over 276Ah, so I am happy to state that the batteries will have a usable capacity of 275Ah before they reach 12v under a normal load.
 

Philip Tomlinson

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I know Phil will do a more comprehensive test and report on this but after I left the conversation about discharging when the low temp charge Mos was triggered I did a quick experiment yesterday.
I set the low temp trip above ambient, thus tripping it. I then connected a load, only 2a+ I know, but still a discharge. The system detected the -ve current flow and let the discharge continue. See screen shots below;
View attachment 95597View attachment 95598
Did you set the discharge low temp cutoff or just the charge low temp cutoff?
Your fault shows chg low temp disconnect not Dischg low temp.
 

Harryw

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Did you set the discharge low temp cutoff or just the charge low temp cutoff?
Your fault shows chg low temp disconnect not Dischg low temp.
I had previous proved the charge low temp disconnect as I tried to pass a charge and it blocked charging successfully.

The latest example above was again with the charge low temp disconnect made (Mos grey) but I attempted to discharge at the same time. This time it allowed me to discharge, proving it does have current direction sensing and acts as you’d expect. Note though that Graphically it temporarily show the charge Mos as green, even though it was ‘disconnected’ but only for the period of the discharge current, as soon as I stopped discharging the charge Mos went back to grey.
100% successful test in my book.

I hope that makes sense.
 

Harryw

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Thanks ordered, I will put acrylic sheets between cells and on ends too but also hold it all together lightly with long pipe clamps.
I’ll then heat shrink the lot together with the above, belt and braces... haven’t decided yet, but I’ll probably put the clamp over the heat shrink should it need adjusting.
 
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Harryw

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I will do some testing.

FYI

All my cells tested over 285Ah on a calibrated discharge tester.

Between fully charge and a 12v reading (whilst under a 10A load) the cells tested a little over 276Ah, so I am happy to state that the batteries will have a usable capacity of 275Ah before they reach 12v under a normal load.
Phil are yours Eve or Lishen?

Be good to see a discharge graph of that.
I have a screen grab of a 280eve with a 20a cc discharge over 14hrs I find useful for understanding. Not a lot above 3.3v not a lot below 3.1v...

382C15B0-7B09-42FA-84FF-4FE05F127A0D.jpeg
 

Derekoak

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Before I order heat shrink tube as above. I need to order the heating pads I need as I imagine they need to fit inside too. Phil, Could you provide a link to the heat pad site you used? My need for heat pads may be greater than yours.
 

Philip Tomlinson

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Before I order heat shrink tube as above. I need to order the heating pads I need as I imagine they need to fit inside too. Phil, Could you provide a link to the heat pad site you used? My need for heat pads may be greater than yours.
I can give you a link to the manufacture with the details of the pads that they are making for me.
I am putting mine on after the heat shrink as they are silicon and I don't want the sponginess to affect the tightness of the heat shrink.
 

Derekoak

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Yes please I will follow your lead though so they do not affect the heat shrink diameter.
The bus bars provided must limit the space that separators like sheets of perspex/acrylic can take. Is there a maximum space?
I am way behind you 2 but any materials from afar would be best ordered so I have a kit ready.
 

Philip Tomlinson

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Yes please I will follow your lead though so they do not affect the heat shrink diameter.
The bus bars provided must limit the space that separators like sheets of perspex/acrylic can take. Is there a maximum space?
I am way behind you 2 but any materials from afar would be best ordered so I have a kit ready.
The bus bars have slotted holes, I will measure the max space between the cells. I am using 2mm between the cells and 5mm on the ends.
 
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