New LifePo4 Battery box and charging question

[davecason]

Hi Gang,

I'm building a battery box with a Pelican case and four 272 Ah Baesun Cells ..... So it'll be used for 12v and 120 out more than likely. (still planning it)

Anyway, there a little matter of charging up the cells ...... here's where its confusing, I will want to charge it up when I'm in the truck cruising along of course.
So right there is a basic DC to Dc charger and I'll pull 20 amps out my butt for a range.

So truck alternator in to the DC to DC charger and off in to the BMS and on to the cells, so problem solved right? (grin) No ...... here is my question to you experts, since the BMS is going to sit between cells and literally everything else in and out of the cells, why do people buy DC to DC chargers at all?
I'm guessing that since the LiFePo4 cells will take everything you can toss at them generally, that DC to DC unit is more about protecting the vehicle and the alternator as opposed to saving the cells? Is that it? How big of a difference is a 20A DC to DC charger vs a 40A DC to DC one to for that matter?

So question 2 in with the same thing, I'm also going to add in a 200 watt folding solar panel for the battery box too ...... so same question, I'll get a MPPT charge controller that will match the panel output and add THAT to the mix as well. So question 2 is again - since the BMS is sitting between the cell and both charging types - the DC to DC charging and the MPPT .solar charging .... can I just use a simple Chinese charger to handle the solar side of things?

Lastly do you folks think I should step it up with something like a Victron BlueSolar MPPT 75/15 for the panel and then maybe a Victron Orion-Tr Smart 12/12-18A DC-DC Charger? It's really what quality of bits do I have before everything hits my JK BMS? For that matter what do you folks think of the Renogy 40A DC-DC Battery Charger with MPPT? I could kill two birds with one stone then so to speak?

SO, the two questions why DC to DC and for the panels what charge controller quality / brand please?

Any suggestions, thoughts, or comments are appreciated !

Cheers'
Dave

 

[pollenface]

why do people buy DC to DC chargers at all?
I'm guessing that since the LiFePo4 cells will take everything you can toss at them generally, that DC to DC unit is more about protecting the vehicle and the alternator as opposed to saving the cells? Is that it? How big of a difference is a 20A DC to DC charger vs a 40A DC to DC one to for that matter?

I say for controlled charging characteristics

So question 2 in with the same thing, I'm also going to add in a 200 watt folding solar panel for the battery box too ...... so same question, I'll get a MPPT charge controller that will match the panel output and add THAT to the mix as well. So question 2 is again - since the BMS is sitting between the cell and both charging types - the DC to DC charging and the MPPT .solar charging .... can I just use a simple Chinese charger to handle the solar side of things?

No, you want something you can adequately program for charging LFP

Lastly do you folks think I should step it up with something like a Victron BlueSolar MPPT 75/15 for the panel and then maybe a Victron Orion-Tr Smart 12/12-18A DC-DC Charger? It's really what quality of bits do I have before everything hits my JK BMS? For that matter what do you folks think of the Renogy 40A DC-DC Battery Charger with MPPT? I could kill two birds with one stone then so to speak?

Look at "SmartSolar" versions as they have built in bluetooth, Bluesolar come preprogrammed at 14.4v bulk/13.8v float & -16.8mv temp compensation which is a good plug and play option for AGM, there's usually a $1-$5 difference between Bluesolar & Smartsolar so no point getting Bluesolar if you want to program it with the app. I believe Will did a review on a Renogy dc-dc charger and gave it the thumbs up.

 

[davecason]

I say for controlled charging characteristics

No, you want something you can adequately program for charging LFP


Look at "SmartSolar" versions as they have built in bluetooth, Bluesolar come preprogrammed at 14.4v bulk/13.8v float & -16.8mv temp compensation which is a good plug and play option for AGM, there's usually a $1-$5 difference between Bluesolar & Smartsolar so no point getting Bluesolar if you want to program it with the app. I believe Will did a review on a Renogy dc-dc charger and gave it the thumbs up.

Hi! Thanks for the help!

I just started physically building this today so the minimal research I've done on the power-house that is YouTube (grin) basically says that using the DC to DCc helps to control the amount of current you're pulling from the vehicles alternator so that seems like a good thing.

I WILL go with one for sure but I don't really want to get past 20 Amps when charging because I have a set of 30A Anderson power poles and cable already run in my Xterra so I want to use that to "top up" the battery box when enroute to the places we need to go.

Plus I think staying around 20 will keep the heat down, right now it's just gonna be a pelican case with no vents or fans (so far...)

OK, for the solar side of things I'll go look at the Smart Solar products for the panel ........

Any suggestions for other choices for the DC to DC ? I'm on the fence about the Renogy model due to its 40A charging ....... but we'll see ! Thanks again.

Cheers'
Dave

 

[pollenface]

I've never used a dc-dc charger greater than 20a, always used solar as well and the draw from the alternator is usually minimal because the battery is already fully charged by the solar.

 

[davecason]

I've never used a dc-dc charger greater than 20a, always used solar as well and the draw from the alternator is usually minimal because the battery is already fully charged by the solar.

Well the alternator in the truck DOES have a 80 - 100 A alternator but I'm only gonna pull a max of 20A as s top-up mostly and the wiring I already have in place is great for a 20a draw ..... I have watched a ton now of vids and they all say put one in - it's actual going in the battery box directly with everything else - so ANY 12v DC source from anyplace can charge it. It can't hurt.

I'm gonna grab the victron DC to DC and a controller as soon as I get the specs for my panel but I am looking for alternatives like that renogy combo - I still might do it since it is handy as hell having both in one unit......