Dc-Dc chrg control for solar and alternator management of Lithim batt.

[CougarCouple]

Hello all
So a little back ground info, for my Question. We have ATC solar system 150 watt panel (added 100watt panel) pwm 30amp charge controller, and a isolating device for alternator charging. 120v battery charger. 2-12v 79amp hr batteries

Want to install 1-100 amp hr lithium ( battle born or one of the quality ones with a warranty. )

If I use a dc-dc charger with solar charging controller seems like that might be all I need. That and a battery monitoring device

So looking for feedback, am I missing something or is this a reasonable device to use.

Thanks Russ

 

[rando]

You are on the right track. You don't necessarily need the DC-DC charger, you may be fine with the alternator charging. What size wire do your currently (hah!) have between the truck and camper?

It would be good to have a solar charge controller that you adjust for the correct settings for LiFePO4, but you current one may do that.

A battery monitor is always a good idea. Maybe but the battery and battery monitor first (Battle Born and Victron are fine choices) and just plug it in to your existing system and see how it works out. Then you can add a DC-DC charger and change the solar controller only if necessary.

 

[CougarCouple]

Hello Rando
Ok to start with my alternator works ok on F250. 10 gauge wire that said I don’t have to charge with the truck as the 250 watts seem to keep the batteries full. Might be at 12.5 volts in morning but at 13.6 by night fall.

In going to lithium my thinking was these dc-dc chargers do several jobs
1 control battery charging from alternator
2 control solar charging
3 if I’m on the road and lithium battery takes a dump, can get a LA of gel battery and this can manage the different type battery.

My batteries seem ok and was thinking I can get all the prep work done for the lithium and wait another year or so to get the lithium.

I’m still reading and looking seems to only be a couple multi dc-dc chargers out there. What would be the negative to do what I’m looking at.

Thanks Russ

 

[rando]

So you are thinking a DC-DC charger that does both alternator and solar (ie a REDARC) ?

Personally I don't think they are a great idea - they are not very configurable, with only a few pre-canned settings and the solar charge controller is not great. Given that you are doing fine with solar at the moment, and probably will do even better with a lithium battery and MPPT, why not just stick with that and upgrade to a configurable MPPT charge controller:
https://shop.pkys.com/Victron-Energy-SCC110020060R-Smart-Solar-MPPT-10020-Charge-Controller-with-Bluetooth_p_7182.html

 

[CougarCouple]

Hi Rando
These are some of the questions that I need to answer. So if I understand lithium correctly Lithium batteries want to be charging at 14.? Till charged. I don’t think my ford alternator does this so I want to find that out. The Renogy company has a product which is selectable, mppt solar charger, battery type selectable ,will charge truck battery with alternator while solar charging the house battery. If no solar availability will charge with alternator. Can top off truck with solar automatically. If the mppt part is charging at correct voltage wouldn’t the alternator side also provide proper voltage knowing there is a lithium battery on the receiving side. I’m not opposed to a charging controller which you can program, but the pwm controller I have now is not and does it’s own thing and the batteries are from 2016 January.
I’m just starting with the dc-dc and if one piece of equipment is gunna
do it all Im ok with that. I used to not like printer scanner fax machines. The one my wife bought just works so well you get the idea.

Russ


https://www.google.com/amp/s/www.renogy.com/amp/dcc50s-12v-50a-dc-dc-on-board-battery-charger-with-mppt/

 

[rando]

LiFePO4 batteries will charge at any voltage above about 13.3V and are essentially full at 13.8V. The 14.X V that you see on some of the specifications are to activate the internal balance circuitry. This only needs to happen once in a while (kind of like the equalize cycle on a lead acid battery) and your solar can do that. So your alternator will charge the Lithium battery, maybe not quickly but it will do it. My stock Tacoma alternator (which is a 'smart alternator' know for low output) still puts 7-10A into my lithium battery. I would wait until you get the lithium battery and see how it goes with solar and your current alternator before spending a bunch on a DC-DC charger.

 

[billharr]

I was looking at this new DC/DC and MPTT controller. My batteries are 6 years old and still holding up, I think because they have always been on the solar controller. If I was building a new system something like this at $299 might be the way to go.


DESCRIPTION
Renogy's DCC50S DC to DC MPPT on-board Battery Charger is designed to give you options! This multi-stage, multi-input battery charger can charge a service battery from an alternator connected to a starting battery or by utilizing solar panels connected directly to the unit. While your vehicle's alternator prioritizes your starting battery, this unit will allow your solar system to charge your service battery first! It's the smart way to keep yourself fully charged and off-grid longer! And with multi-stage charging and multi-chemistry functionality, Renogy's DC to DC MPPT Charger has you covered whether you're using Flooded, Gel, AGM, or Lithium batteries.

KEY FEATURES

• Designed to charge service batteries from two DC inputs—solar panels and alternator.
• Built-in Maximum Power Point Tracking (MPPT) to maximize the solar power.
• 3-phase charging profile (Bulk, Boost, and Float) ensures your service battery will be accurately charged at the correct voltage levels to 100%.
• Built-in Voltage Sensitive Relay (VSR) for easy setup with traditional alternators.
• Compatible with smart alternators (with variable output voltage).
• Trickle charges the starting battery via solar panels if the service battery is fully charged.
• Isolation of the starting battery and the service battery.
• Temperature and voltage compensation features prolong battery life and improve system performance.
• Smart Protection Features: battery isolation, over-voltage protection, battery temperature protection, over-current protection, overheat protection, reverse current protection, solar panel and alternator reverse polarity protection.
• Compatible with multiple battery types: AGM, GEL, Flooded, and Lithium.
• Compact with a sturdy design, it was built tough for all conditions.

 

[Stokeme]

Mr Cougar here’s some thoughts with LFP4 & my eventual system plan.
I called/talked to 4 different battery companies to learn about lithium planning. There were concerns about an alternator/LA truck battery to LFPO4 house battery connection. It’s important, I was told, to understand your alternator. Not my strong suit. I needed to KISS for me. Also, at that same time, a WTW thread alluded that the differences in battery chemistry, specifically resting voltage, between truck LA (lower) & house LFPO4 (higher), caused some overnight V drain of a house LFPO4 battery. A Dc-Dc battery charger seemed to be the solution to enable safe truck to house charging & prevent unwanted collateral drainage. Sterling was a top choice. At ~$300 +/- it seemed steep & added more wiring/mounting.
I went with a 100 Ah battery from a different battery company (@~$800). With more thought, I decided to add another 50 Ah battery (@~$500). My plan was to go with solar charging only & increase my overall Ah storage to meet my needs. I did not spend too much more on 150Ah vs a 100Ah battery/dc-dc charger combo. My goal was to simplify things while keeping my batteries healthy. This was my solution. It’s worked well for almost 2 years. So far, it’s actually been overkill. But, it’s been sunny more often than not, so not really stressed yet. I did plan ahead, with my Shell build, for low Ah usage. I really like my Victron controller. I will definitely upgrade my cheap commodity flex solar panels at some point.
PS ... the Renogy multipurpose unit is very intriguing. Perhaps Rando will comment about it.

 

[Stokeme]

Here is a Will Prowse video & his take on the above mentioned Renogy unit. He is positive about it. It does combine both aspects of a charger & a controller in one unit. But, it seems, you might need to be able to isolate dc/dc while driving, & then likewise mppt for solar usage when not driving, to get the most out/full benefit of each without some inherent limitation. Above my full understanding.

 

[Vic Harder]

I was pretty stoked about this product until 5:00 minutes into Will's review.... you can only use 12v panels in parallel in your solar array with this unit. My 395w single panel on my roof would not work. Most folks with multiple 100W panels on the roof will be fine though.

Stokeme, the ignition wire is no more than a wire going to anything that is "hot" in your truck when it is running. And it might work fine without adding that.

Otherwise, I'm totally in agreement with rando on his comments.

 

[ricardos]

Very useful information. Thank you for your answers. By the way I found article about How to Get the Cheapest Solar Panels? | Websolarguide.

 

[lostcreek]

I can (tentatively) recommend the Renogy Onboard DC-DC charger. I've just installed the 20-amp version. I already have a good solar system, all I needed was a dependable DC charger for those infrequent times when solar is not enough. There aren't many reasonably priced automotive DC chargers w/o solar CCs, but this seems to be one. I'm assuming that Renogy uses the same DC charger tech inside the ones that also have solar CCs.

I say tentatively since
a. There were problems getting it to consistently operate correctly, eventually they resolved
b. Renogy has not replied to my Help requests for installation questions
c. my camper is off the truck at the moment, so I've only been able to do engine-idle tests

However, it does now correctly charge the house battery (120 AH Lifeline AGM) at various SOCs from 70 to 100% (bulk, acceptance, float). I got the temp sensor too. The ignition sensor wire (D+) is def. required but does not have to come from the engine if you already have some sort of relay/voltage switch on your positive coming from the alternator/battery; since I do, I just tapped off my positive wire input just before the charger's input terminal.