Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
MPT 7210a charge from car 12v
#1
Hello,
i am building a portable LiIon battery for my van (simple diy camping build). I want to build it into a tool box to make it portable.
I already have a MPT 7210a charger that will be inside the toolbox and i would like to be able to charge the battery without  solar panel while i am driving. 
Can i connect (i would use powercon connectors) it to my car battery? 

Question: What kind of relay would i need to make sure it only charges when the motor is running to prevent my car starting battery from draining? I think it needs to be something like a voltage meter that opens a relay at the cars charging voltage when the motor is running.
Reply
#2
1. Your battery need to be atleast 17v or more. The 7210 is boost only.
2. You need any relay but connected to a source where you have Power like the 30+. Aka Power when engine is on. Depends on the car.

Why not just plug it into the cigaretter lighter outlet and instead of that 7210 use a standard Buck/bost converter?
completelycharged likes this post
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
Reply
#3
https://www.amazon.com/Battery-Isolator/...y+Isolator priced from the $17 dollar range up to over $100 dollars.
if you really want/need a permanent solution.
Later floyd
Reply
#4
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).
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
Reply
#5
(07-12-2020, 04:26 AM)completelycharged Wrote: Guessing the toolbox battery is >12V. 24V.


Yes, wanted to build it 24V or 48V

(07-12-2020, 04:26 AM)completelycharged Wrote: 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).


Thats cool, i didnt know they have an adjustable input voltage (low voltage protection). Thank you! And also all others for their good hints!
Reply
#6
The trouble with the cigarette lighter solution is they are limited to 8a - that's only 8 * 12 = 96watts.   Even a standard 7-way (trailer connector) will be in 25a max range - e.g. only 300w.

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. 

Obviously solar panels are part of this plan - but the other part is charging while driving on a trip.  Can I get to 750w/hour charge while driving?    750w/12v = 63a sustained. 

It seems like a battery isolator (as listed above) is a key piece so you make sure your vehicle battery is charged normally / not affected by secondary charging.   Then, how to get 12v to 48v?   Maybe a high amp 12v (say 80a = 960watts) 120v inverter -> standard 48v lithium-ion charger(s)?    
(Note: I already own 3 x 750w YZPOWER 48v lithium-ion chargers that I run from my generator as emergency power -> battery bank and I was hoping to use 1 or 2 of them in this situation).  

Do they make 80-100a 12vDC-48vDC boosters that one can afford?    Seems like you would still want the battery isolator as input to the 12vdc -> 48vdc booster or do you need a 12v battery as a buffer?
Reply
#7
You can most likely not get 63a sustained unless you got a larger gen like an 130-150 or even 200. Note beware that the average modern car easily need 40-80a continues. Like ignition, powersteer IF thats electronic. Ac and fans and so forth.

So before you plan anything before going above 20a you need to crosscheck what the car can handle. The generator on cars are also not made to run 100%
I know thos working with it for a bit Smile some rv based cars you can choose different generator versions due to this.

But för instance My car here with 160a gen they recommend max extra of 30a externaly. Like a caravan or headlights.
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
Reply
#8
>But för instance My car here with 160a gen they recommend max extra of 30a externaly. Like a caravan or headlights.
Yes, appreciate the return to reality.   An alternator can *over heat* if used much beyond its design - even if technically it can produce amps.     They do make higher amp alternators...  ones that supposedly will put out 240a (instead of 160a) type of thing...  but the reality is that it takes a lot of amps at 12v to get to 1000w range. 

Maybe a generator running on the tongue of the trailer is a better way to think about it.

I'll be interested to see if anyone comments on what they did that was sustainable. 
Reply
#9
People needing of high current /Power for rv or for instance audio tend to add an extra generator instead.

Not doable on all cars though Smile

If you have roof space add panels There Smile
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
Reply
#10
(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?
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)