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Looking for a 24V Dc to DC.

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(@the-blind-wolf)
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Joined: 3 years ago
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Okay, I want to use my AGM battts for the inverters, since they can handle the high loads better then my blasted lithuim batts.  Is there a way to convert a gs inverters from sawn to take the 14.4 system to charge the agm 12.8 or what ever the float level of the agm is?  I got over 200 ah of agm, and a ton of the other, just the many wires and bms and balancing is being too much to fool with, and if I can just use the Lyth to keep the agm charged and not provide the amps to run the system I think it would solve my issues. other wise I would have to redesign all the batts, and I'm not up to the task for it.

 

I've consider on takeing all the same batts, brand and all and just make one big are 24v bank, instead of having 10 12 v batts combine and then go to a bus bar.  I'm not sure if a 700 ah 24v single batter would be able to handle 600 amps output on its own or not. 

 

other wise I'm going to have to buy a bunch of Sids balancers and if they was already built with heat sink and wires I would gladly pay a little extra to get them so it can be a drop in.


   
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(@sid-genetry-solar)
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2 hours ago, The Blind Wolf said:

Is there a way to convert a gs inverters from sawn to take the 14.4 system to charge the agm 12.8 or what ever the float level of the agm is?

If you're asking about the battery charge settings on a GS inverter--of course, they can be fully configured to whatever charge voltage you need (for the appropriate battery voltage range, of course).

What's up with the subject of "24v dc to dc"?


   
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(@the-blind-wolf)
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8 minutes ago, Sid Genetry Solar said:

If you're asking about the battery charge settings on a GS inverter--of course, they can be fully configured to whatever charge voltage you need (for the appropriate battery voltage range, of course).

What's up with the subject of "24v dc to dc"?

I ment, I was looking for a 24v/ 24v dc to dc for the batts, to take from the ly4p 24v system and keep the 24v AGM batts topped off, but not be used to pull from them during the inverter being used, just charging only dc to dc isulation.


   
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(@the-blind-wolf)
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Joined: 3 years ago
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Topic starter  

the GS inverters would be running off the AGM batts, instead of the lythium, the lythuim would be keeping the AGM batts charged up since AGM batts I have can handle the amps output and not freaking over heat like the stupid lythuims with all the hundread wires to make it work lol.


   
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(@dickson)
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Joined: 3 years ago
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 the lythuim would be keeping the AGM batts charged up since AGM batts I have can handle the amps output and not freaking over heat like the stupid lythuims with all the hundread wires to make it work

I like to see a picture of your  hundred wires to the lithium  batteries .   My  60v  BMW car lithium ion battery only need 2 wires with a switch  a 400amp fuse a 65 v regulator with a DC choke connected to  the PJ  inverter and using for 2 years .  Off grid garage on youtube has hundred wires and all kind of problem  charging  his lithium phosphate iron  battery .   I  also has 4 AGM  battery connected is series for  48v  and is using the same BMW lithium ion battery to  charge to 14.4 v  each  with  voltage regulator . 


   
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(@thebutcher)
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Posted by: @the-blind-wolf
I ment, I was looking for a 24v/ 24v dc to dc for the batts, to take from the ly4p 24v system and keep the 24v AGM batts topped off, but not be used to pull from them during the inverter being used, just charging only dc to dc isulation.

Yes, they are available but you will pay good money for a decent one.  Obviously the link below is for products in Australia but there are internationally known names in the list such as Victron.  If nothing else it will give you an idea of what to put into your own Google search

https://www.mygenerator.com.au/24v-dc-to-dc-battery-chargers.html

 

Posted by: @dickson
I like to see a picture of your hundred wires to the lithium batteries .

Not litterally hundreds, it's a turn of speech.  'buckets', 'heaps', 'oodles'.  Reality, at least 1 wire per cell to BMS, high current wire from B- to BMS etc.


   
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(@thebutcher)
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If the isolation requirement is only there to prevent discharge of the lead acid battery back into the lithium battery / load there may be a cheap alternative.  If you have a spare solar charger you can get a CC boost power supply to feed the PV input on the solar charger and let it charge the lead acid battery.  The SCC will prevent backfeed.  It is important to use a boost power supply that is current limited to prevent the SCC potentially being able to overload the boost power supply and cause it to go bang or shut off.  For a 24V lead acid bank, 24 > 48V boost on the SCC's PV input would do the job.

A CC power supply will continue to output power, but the voltage will fall to hold the current at the power supply's limit.  This will allow the SCC to find the 'Vmp' and perform a normal charge cycle instead of constantly seeing the 'PV' voltage drop which will probably cause it to reset the charge cycle.

It would also be possible to use a boost converter that will supply more watts than the SCC will ever draw to avoid this issue as well.


   
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(@the-blind-wolf)
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Posted by: @thebutcher
If the isolation requirement is only there to prevent discharge of the lead acid battery back into the lithium battery / load there may be a cheap alternative. If you have a spare solar charger you can get a CC boost power supply to feed the PV input on the solar charger and let it charge the lead acid battery. The SCC will prevent backfeed. It is important to use a boost power supply that is current limited to prevent the SCC potentially being able to overload the boost power supply and cause it to go bang or shut off. For a 24V lead acid bank, 24 > 48V boost on the SCC's PV input would do the job.

 

yes, but most cc are AC chargers right? so it wouldn't work for dc to dc.  unless I take  3k inverts that are 12vdc and run 24v chasrgers to the lead batts to keep them top off.  I mean I got plenty of 12vdc inverts that are pure sign, I would just need to buy a 24vdc charger or I could just  use 12v chargers on each lead batt to save money as 24vdc chargers are stupidly priced. though the conversion ratio would suck doing that though, from dc to ac, then back to dc seems it would be bad.

 

Oh well.

 

Yeah the wire issue,  lets see, I'm soldering 4 to 5 12 awg wires between each battery cell packs then one balance wire per cell pack for the stupid bms, then the neg and postive wires going to the lug  nearly 28 wires per 12v battery and then 10 12v built, that not includeing the presmatic batts I got and the Ion batts either.  Then the wires going between each bank and serie lugs.

 

See what I'm gtetting out, too many wires and all it takes is one wire or conection to go bad, and either you got a fire, or something worse.

 

I am trying to figure out how to stream line the setup, I want to go Sid way, but that still leaves issue with so many wires and adding balancers I would need over 50 of them to even make a dent into redoing the system.  I don't have the money like I did, and until I know something going to work for sure, I've not had the system going for a bit, 

 

It was fun for a bit, until I nearly had batteries started over heating and among other things going on, that I stop, cause I wasn't getting any where with what I have, I got enough power to run the setup, it just getting it configured to be stable and less wireing to keep it safe.

 

I've though about running each battery bank to a bus bar, but there are no bus bar big enough to handle 600 amps at 24v, and I would need one that can handle that, 

 

That would elemate some wires, instead of having wires ging to battery bank to battery bank, and then branching off to a small bus bar to the inverters.

 

If I knew what type of metal I could use for a bus bar that can handle it, I would go grab it at the local hardware store, drill all the holes for 3/8 bolts and go with that, I've already melted a three layer copper bar bus bar i made from too much power.


   
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(@thebutcher)
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There are more chargers with DC inputs available than I care to mention.  I linked you to a site that sells them, in Australia admittedly.  Do a Google search if you want a DC-DC charger.  If you can't find one, well you just are trying.


   
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(@dickson)
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I've though about running each battery bank to a bus bar, but there are no bus bar big enough to handle 600 amps at 24v, and I would need one that can handle that 

 

You are  right  about no bus bar to handle  600  amps  .  The  wire  size needed  will be  1 and 1/8  inch  copper  or 700 kcmil  .   The  cost of wire  and breaker and fuse and switch for  24 volt  and 12 volt  inverter  will cost more than one GS inverter .    Has to go with  48 v or 60 v  inverter .    Thank you for your information  as I did not know your situation before  and why  the fire  and the melted  bus bar .     


   
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(@dickson)
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For your information the copper bar size to handle 600 amps is 1 and 1/2  inch  square  and  cost  700 dollars  for 6 feet .    How many feet  do you think you need ?  Has to go with  48v or 60v inverter  .    


   
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(@the-blind-wolf)
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Posted by: @dickson
For your information the copper bar size to handle 600 amps is 1 and 1/2 inch square and cost 700 dollars for 6 feet . How many feet do you think you need ? Has to go with 48v or 60v inverter .

Ouch. see the copper bar I made was at least a 1/2 thick and it didin't cost that much.  But it was three bars put together to make it that thick..

 

and no I can't go to 48 or 60v, already got the two gs inverters.  Might get a 48v 12k inverter though. . . just waiting on that one. . .


   
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(@the-blind-wolf)
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if I knew how much a pain 24v would be to deal with for the amount of power I need it wouldn't be a issue, I would have went with either 36 or 48v. and not able to see to change the wireing inside the GS plus I don't want to void my warrenty to change it.

 

After just thinking about it, I think I cam up with a better way to solve the high voltage issue, is by s;itting the battery banks each set of banks can handle 4400 amps each, so each inverter would get its own set of batts, what I need to do is get a DC to DC 24v to keep them balance, so if one bank gets power it can charge the other at the same level and back and forth.  I think I would need a non isulated dc to dc, or two islated dc to dc.

 

I got a set of presmatic cells that can outpuut 500 amps, I've tooken one of the cells and had a bolt wleded onto the outlets with a 3/8 stainless bolt, if I get the others done that way the other 7 cells, I can usethem as a buffer to the gs inverters.  wish I got more of them when  was lucky to get 8 of them at the time.  I almost got the 4 blaancer done and going to use them on just four of them then get another set of blanacers so i can have all 8 with its own balancer before I remove the bms and just rely on the cut off of the gs and the max dc charge of the solar charger as a bms, and the balncers to keep the volatge of each cell balance..  

 

From what Sid said he is basicly doing on his system.


   
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(@dickson)
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After just thinking about it, I think I cam up with a better way to solve the high voltage issue, is by s;itting the battery banks each set of banks can handle 4400 amps each, so each inverter would get its own set of batts, what I need to do is get a DC to DC 24v to keep them balance, so if one bank gets power it can charge the other at the same level and back and forth.

 

Yes  if  you sit each  separate battery banks  to handle  4400 watts  then  4/0  welding cable  will work .    I  have  12 separate  battery banks   using  4/0 welding cable  that each bank can handle  10 thousand watts  at 60 volts .    I  go  back and forth  by charging  one bank  and  using one bank  with the inverter  and  one bank  waiting  in reserve  already  fully  charge if  more power is needed  to connect  to the inverter .   I  use voltage regulator  or BMS on a few battery bank and  MSB  charge controller  instead of  DC to DC  converter or balancers  to keep the battery from  overcharge  and  causing a fire .    Sid balancers  will  work but  require many  wires like a BMS .     


   
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(@waterman)
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20 hours ago, dickson said:

For your information the copper bar size to handle 600 amps is 1 and 1/2  inch  square  and  cost  700 dollars  for 6 feet .    How many feet  do you think you need ?  Has to go with  48v or 60v inverter  .    

3 # 3-0 wires would handle that. How about soldering and crimping terminals on one end then strip the length needed plus the extra for the same terminals on the other end. Then insert in a 2" copper pipe. Compress the pipe till almost flat keeping the bundles loose on the end without the terminals yet. Crimp and solder on the terminals. Finish compressing the pipe. Solder the pipe full at the ends. That would give you a buss bar with 3 terminals on each end and just about equal the size you mention. I'm about to have to worry about the same sort of thing because the batteries to be delivered tomorrow can output 200 Amps per cell normally and they are in 7S3P configurations. And the idea is to use all four of them in parallel. If a string shorts, they can put out between 300 and 400 Amps per cell. That means between 900 and 1200 Amps per battery. I intend to solve that problem by fusing them for no more than 100 Amps each battery and then the buss itself at 300 Amps. Depending on what I find, I might change them to 7S4P units times 3 to save space as the single cell packs should be the same thickness as the doubles from looking at the pictures. They are SPIM08HP 3.7V 8AH 200A Lithium Ion Cells.

And these are what I had in mind when I ordered my order of Sid's balancers.


   
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