12vdc charger for 4s lifepo4 portable battery

gpn

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I'm looking for a 12vdc input charger that runs off the cigarette plug in a vehicle to charge a 37ah 4s lifepo4 portable battery. I'm also planning solar but I'd like to be able to run it off the engine when mobile. I've been searching around and so far have only come across lower power options (1.5 amp charge rate). I'd like something in the 5-10amp range so that I can charge relatively quickly.

This is a miscellaneous portable pack that will power QRP ham radios and cell phones. Nothing crazy just looking for diverse ways to keep it charged! Thanks.
 

DarkRaven

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Most RC smart chargers are DC-powered, just pick one of your choice. I'd recommend an iCharger 106B+ for this purpose. Or rather the new iCharger X6, I always forget about that one...
 

gpn

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Can those chargers be plug and play? I'd like to just plug in the cigarette port and then into my box.
 

DarkRaven

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No.

If you want a plug and play solution then I'd suggest buying a Victron PPP-40 battery. This one offers built-in, plug and play solutions to be charged from all kinds of sources.
 

Korishan

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If a charger can run from a range of like 6V - 16V (as there a lot of them that can have such a range, and even higher), then they will run on DC voltage from your vehicle. You just need to use the proper connector to hook it up.
I personally wouldn't use the cig lighter port for charging close to 10A. or even really higher than 5A. Unless the port is specifically called a "Aux Port" or "Accessory Port". Otherwise, the wires are usually fairly small and you'll get voltage drop on the wires under high amp draw.

If you don't have an Aux Port, then install another port that "can" handle those higher amps and use heavier gauge wire.

I've seen fuses for the "cig"port being only 5A.
 

gpn

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The main reason I want to charge off an aux port is for long trips in the Type 3 Wildland fire engine. Those are wired for like 20-amp ports! The problem is that when we stop or anytime the engine is off the entire battery system and aux power gets shut off. So being able to charge a large battery at a faster rate and then use that smaller battery to run electronics and charge accessories would be handy. Also being able to run QRP ham radios for a few hours would be nice! I bought some of those lifepo4 cells from battery hookup to make a 4s10p with 3700mah 26650 cells. Should net me around 475wh.


Can I just use a buck/boost and bulk charge it to close to the top end voltage? I was thinking about adding a victron mppt controller for remtoe operation. Can I just wire in the dc from the vehicle to the mppt charger? What would happen if I did that?
 

Korishan

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20A! Nice. Shouldn't have any issue with those then :p

That's a good idea to quick charge a pack, then run smaller stuff off that pack. Should work.

Or you could just sneak in a and turn the ignition key to On when ya wanna charge your cell :p
 

DarkRaven

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And then offer your generous assistance to start the engine with your battery when the starter battery is completely flat! :D
 

gpn

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Korishan said:
20A! Nice. Shouldn't have any issue with those then :p

That's a good idea to quick charge a pack, then run smaller stuff off that pack. Should work.

Or you could just sneak in a and turn the ignition key to On when ya wanna charge your cell :p

HAHA! Last time we were out we had to replace the batteries! Too much time on and totally killed them!! Good thing it only has 3 950CCA starting batteries.


DarkRaven said:
And then offer your generous assistance to start the engine with your battery when the starter battery is completely flat! :D

It would probably crank it over a couple times! That would be quite the load!
 

gpn

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Ok so looking at the hobby chargers I think that is what I am going to go with.

Here is the imax b6 https://hobbyking.com/en_us/turnigy-reaktor-250w-10a-1-6s-balance-charger.html
I like that one but it is only 50 watts of charge

I also found this one: https://hobbyking.com/en_us/turnigy-reaktor-250w-10a-1-6s-balance-charger.html
That has a higher charge current. Looks like I should be able to charge at 10 amps. This is going into a 4s10p lifepo4 26650 pack with 3.7ah cells. 1 amp charge per cell is conservative for the cell life but maximize my charge time. Does turnigy make a decent charger?
 

DarkRaven

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Turnigy usually doesn't make their own chargers, they are instead based on SkyRC or Junsi or other OEM units. This is pretty normal for the charger industry, it's a huge OEM business.
 

DarkRaven

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As far as I know there is nothing to worry about. I think it's fair to say that they are decent.
 

Crimp Daddy

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You could consider an appropriately sized DC-DC that has CC/CV modes at least thats how I charge from my cars 12v port. I have a fridge in the truck a 24v battery pack for it which charges while the truck is running. The pack is top balanced but the BMS is in case I have problems.

That said, I love RC / hobby chargers too. I use them to charge and maintain many packs I build.


gpn said:
So I came across this victron product recently. I thought that I would share it here. This is essentially was I was looking for earlier this year. I ended up with a RC charger which is nice because it can balance charge.

Had I found this I would have gone this route!

https://www.victronenergy.com/dc-dc-converters/orion-tr smart

Those are awesome units ... that's pretty much what I use (Victron Orion 12/24-10 step up DC-DC)

I never mention them because people generally dont want to spend the money on it and opt for the chinese stuff. The non-isolated ones are great too for battery charging, and you save a few bucks in the process.
 

gpn

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What DC/DC with CC/CV do you use? I'd check it out!
 

HughF

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it's a 4S LiFePo4, just hook it straight to the 12v outlet and let it charge...

That's the beauty of LiFePo4, provided those cells aren't totally mismatched it should stay in balance and the voltages are a perfect match for a 12v automotive system.
 

Crimp Daddy

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HughF said:
it's a 4S LiFePo4, just hook it straight to the 12v outlet and let it charge...

That's the beauty of LiFePo4, provided those cells aren't totally mismatched it should stay in balance and the voltages are a perfect match for a 12v automotive system.

Agreed... for LiFePO4, I would just top balance the cells and let it charge out of the 12v outlet. That said, if you start blowing car fuses you might want to get something to limit current for charging.


gpn said:
What DC/DC with CC/CV do you use? I'd check it out!

For most of those boards, I was using the DROK branded Chinese PCBs. Google "dc-dc cc cv buck boost converter" should give you some options. I ran a few of them in parallel to get the current I wanted and to keep the heat down because I dont trust them not to eventually burn out or catch on fire.

That said, I much prefer the Victron units. 10a is plenty of charge rate so I just size the unit based on the max charge rate I want. Check the manual, it allows for three step charging, bulk/absorbtion/float and the bluetooth models allow for setting management via a GUI. The other units I have used are pretty nice too. I also trust them to handle the advertised current continuous a lot more than the import PCBs.

That said, I am using these to step up from 12 to 24v for lithium charging.
 

gpn

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I like the idea of using a dc-dc so I don't need to worry about the fusing situation. Not all cars have the same 12v output. Are you just using the victron orion tr? I really like blue stuff. I'm going to be ordering my 3rd mppt shortly.

My pack is only 450wh or so so 10a (~140w) of charge is plenty for me as well.
 
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