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MPT 7210a charge from car 12v
#11
(07-12-2020, 09:26 PM)2weiund2wanzig Wrote:
(07-12-2020, 04:09 PM)OffGridInTheCity Wrote: I'm building a cargo trailer -> camper with a 14s/48v 18650 battery bank and have been noodling on how to charge it while driving.   I'm hoping for at least 13.5kwh or even 27kwh if I can fit in enough packs...   but this requires a 'next level' of charging watts capability beyond a  typical RV. 

27kw? Just... why? I run a 400sqm house with 10 people for a 5 days with that haha. Is that still called camping? :-) What do you want to run with that?
And... wouldn't it be easier to use solar panels and / or grid power to charge it?

My DIY powerwall batteries are 14s100p'ish - 13.5kwh - each.  I've gotten good at building them with 6 in operation (81kwh) and I have enough cells for 2 more (27kwh).   

I just got my 7 x 14 cargo trailer - and I think I can put the batteries in the floor (like an EV car).    I plan to make the batteries compatible so I can plug the trailer into side of the house when parked and expand my home powerwall.  This will make them useful to the house and be 'ready to go' when taking the trailer out - e.g. keep them in regular use and regularly monitored. 

I haven't scaled out the system - but I want to plan for a 9000'ish BTU mini-spit cool and heat 24hrs/day in moderate climate.   Not sure yet what I need - several things to figure out starting with power needed to run a mini-split 24/7 - but with the knowledge I've gained from home powerwall I can figure it.     Maybe I'll have to go scale back to 12hrs/day etc - not sure yet but a typical RV setup with a couple of 12v BattleBorn(s) is not nearly enough, will need a level or 2 bigger system. 

There are 2 base situations - e.g. driving all day / camping at night (less mini-split needed) and boondocking (24/7 minisplit maybe).   The driving all day - seems like such a natural thing to want to harness that vehicle engine power for battery charging since gas (gas mileage) is not an issue for me.   Boondocking all day - then panels take top focus.

The trailer can go up 5,000lbs - so its a matter of space rather than weight I'm pretty sure.   Panels on top (maybe 4 x 300w) and perhaps panels stored in the trailer for another 1200w deployed alongside trailer.   Ya de ya da....   we'll see Smile
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#12
(07-12-2020, 04:26 AM)completelycharged Wrote: Guessing the toolbox battery is >12V. 24V.

Use a 1200W boost converter, set the input voltage limit to say 12.8V. Set output current limit to say 8A. Plug it into the cigaretter lighter outlet as Daroma said.

If you use the 1200W or 1800W units connect the battery pack to the output first as connecting the 12V from the car may in some instances blow the unit. They are great handy units but are designed with solar in mind (constrained input amps).

I have one of these: https://www.ebay.de/i/232461793739?chn=ps&norover=1&mkevt=1&mkrid=707-134425-41852-0&mkcid=2&itemid=232461793739&targetid=896427593016&device=c&mktype=pla&googleloc=9068348&poi=&campaignid=10203814986&mkgroupid=101937416117&rlsatarget=pla-896427593016&abcId=1145992&merchantid=138391959&gclid=CjwKCAjw9vn4BRBaEiwAh0muDE0eA84rTtNzPz8H-mFtqsjX0NF35aI4fafK0LP3L4rtkiGINXAY5hoCX5gQAvD_BwE

I am a bit confused by the ratings. When i power it from maybe a 12v server-psu with 2kw and want to charge a battery pack of 24v with it i can only charge with 12v*20a = 240w and the same as i want to charge a 48v battery because it is the input voltage that matters?
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#13
(07-27-2020, 05:00 PM)2weiund2wanzig Wrote: I have one of these: https://www.ebay.de/i/232461793739?chn=ps&norover=1&mkevt=1&mkrid=707-134425-41852-0&mkcid=2&itemid=232461793739&targetid=896427593016&device=c&mktype=pla&googleloc=9068348&poi=&campaignid=10203814986&mkgroupid=101937416117&rlsatarget=pla-896427593016&abcId=1145992&merchantid=138391959&gclid=CjwKCAjw9vn4BRBaEiwAh0muDE0eA84rTtNzPz8H-mFtqsjX0NF35aI4fafK0LP3L4rtkiGINXAY5hoCX5gQAvD_BwE

I am a bit confused by the ratings. When i power it from maybe a 12v server-psu with 2kw and want to charge a battery pack of 24v with it i can only charge with 12v*20a = 240w and the same as i want to charge a 48v battery because it is the input voltage that matters?
As I read it, it says input current = 20a max.   So it limits input amps regardless of voltage.   Which means you're right - 12v input @ 20a will limit you to 240w.   
The MPT 7210a chargers have a similar concept - they are limited to 10a output regardless of the input power or output voltage Smile
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#14
For one of my projects ill need 500w charging minimum. I think i could use 2 of these in parallel. Or is there some other option in that price range?
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