Renogy DCC50S dc-dc + MPPT?

I just bit the bullet yesterday on a 170ah renogy lifepo4 battery. Yesterday they were just over $1k.

Renogy Lithium Iron Phosphate Battery 12 Volt 170 Amp Hour https://www.amazon.com/dp/B07FDHRP45/ref=cm_sw_r_cp_api_i_7ZO5Db2EE8BCQ

Today it seems they're almost $1,300. Guess I snuck in.

I'm now of the need to upgrade my charge controller, and while I was going to go with victron I'm seeing that Renogy has this new MPPT and dc-dc charger all in one. Out of stock at the moment, but seems to retail at $299. Seems to be a good deal compared to buying a victron and something like a sterling.

Combines alternator charging with isolation, priorities starting battery and trickles it once house battery is full, alternator charging up to 50A, specs below:

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.

https://www.google.com/amp/s/www.re...50a-dc-dc-on-board-battery-charger-with-mppt/

Does anyone have any experience with that thing? Pros and cons of combining these functions? Am I simply better off with the victron/sterling combo? I know it's more tried and true but tech is always changing...

The only limitation, which is similar with the CTEK systems, is that solar input is limited to 25v, which means you must use smaller panels (like the Renogy ones) as opposed to a single large residential panels like a Sunpower or LG. Other than that, it just depends on build quality. A CTEK system with 140a capability will run you a couple hundred more; when it was a 100a output, I think I paid around $400.


Cheers,
Greg

The built-in controllers are nowhere near as good nor efficient as a dedicated unit.

Victron smartsolar is my reco

We can offer you the Kisae DMT1250 50A combination alternator/solar DC-to-DC charger for $290 but you'll need to contact Kim directly for that price. The Kisae has a maximum input voltage of 32V. MPPT tracking efficiency is better than 98%. For LiFePO4 batteries you'll want to set it for a constant charge voltage rather than a multi-step profile that is needed for lead-acid batteries. In stock and can ship immediately.

All the best,
Hein
DIYvan <-click for Kim's contact info
541 490 5098

Do you already have alternator charging in place? If so test that out first. You may get reasonable charge rates directly from the alternator, which is already at a great voltage for fast charging LFP packs.

Typically the combo chargers do not perform well compared to dedicated solar controllers.

Midwestdrifter said:

Do you already have alternator charging in place? If so test that out first. You may get reasonable charge rates directly from the alternator, which is already at a great voltage for fast charging LFP packs.

Typically the combo chargers do not perform well compared to dedicated solar controllers.

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I do have alt charging already, via a Battery Dr. isolater. I'm new to LFP batteries and trying to do it right the first time.

One other point that is necessary to consider is the fact that the Renogy BMS will lock out in certain cases, and you need a Renogy charger to unlock it. I've been wanting to go with victron due to the reputation/function/BT functionality, but if the BMS locked me out and I didn't have a way to unlock, well, that would suck. Lame compromise to make.

Apparently the NOCO genius G1100 has the unlock capability, per a review on their website. All a little cumbersome in my opinion, but apparently that's what I get for choosing their product. I obviously have more research to do in terms of my charger/monitoring setup, and I'm in no giant rush. I just want to get it right. Sounds like maybe the Renogy all in one package may not be my best bet?

Hein, I'll look into your suggestion about the Kisae, thank you for your offer!

We can offer you the Kisae DMT1250 50A combination alternator/solar DC-to-DC charger for $290

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Damn good price and I'm happy with mine

Z: It’s probably a bit different for their batteries as many brands use the same CN battery mfgs, but I’ve seen lots and lots of failures of Renogy components like charge controllers time and time again. Not this model though...

I have seen a few of those same style batteries torn down. I would treat the current limit as a short term max. 50% of the discharge current would be a safe number.

Midwestdrifter said:

I have seen a few of those same style batteries torn down. I would treat the current limit as a short term max. 50% of the discharge current would be a safe number.

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Well darn, I thought part of the benefit of LiFePo was the ~80%dod-ability. Oh wait, do you mean that only pulling out 50a for longer current draws would be safe?

V: Yeah I think this unit hasn't been on the shelf long enough have many documented failures. What I'm gleaning is that it's more desirable to have separate CC and dc-dc charging. If one goes down at least you have the other. Redundancy is cool.

I spoke with someone at Renogy yesterday to inquire about unlocking a battery when the BMS locks it out due to low voltage. He said renogy chargers would do it, and then he said that PROBABLY victron or EPEVER could also do it. Said that once the BMS locks it out, it requires a certain voltage signal sent to unlock it, and that most of the larger companies' chargers would have that function. He could or would not tell me however, which ones would or would not. A bit frustrating, I'm starting to regret this purchase.

He echoed the benefit of having separate CC and dc-dc.

I also spoke with Hein to inquire if the Kisae DMT-1250 has this capability, and he wasn't sure but he's looking into it for me (Thank you Hein!!!).

So, all of my options as they are on the table now, and to those of you who have built successful LFP-based systems, what are your suggestions? Especially those of you who have used renogy batteries? I should have mentioned in the original post, I have 200w of solar. 2 100w panels in parallel. 2006 sprinter.

I've been wanting I get the Victron/Sterling combo but the Kisae also has great specs, seems to be well liked, and that price point is very attractive. Just tryna get my ducks in a series...

The BMS doesn't need a special signal or anything. Simply raise the terminals above about 12.5V, and the BMS will reconnect. Not all chargers will start charging without a voltage already present. A way around this is to have a ~5AH sealed lead battery connected in parallel with the lithium one. This will allow charging and thus reconnect the BMS after a lockout.

Yes, I am talking about current rate (not SOC/DOD).

I will reiterate my point, that LFP will charge rapidly and without issue from the alternator directly. You may need to put slightly smaller cable or fuse on the charging run to reduce current if its a bit higher than desired. You do not need to worry about "overcharging" unless you drive a ridiculous amount.

I'm in a similar boat as you, since I started purchasing Renogy products I found it made more sense to do most/all Renogy for compatibility. For ~$230 I was able to pickup the 20A Rover Charge Controller and the B2B Charger. With my 200W solar setup and 200Ah Lithium battery bank, I think our setup is somewhat similar. We estimate our power needs at about 55Ah (we are pretty light energy users). We will also have a 11 lb propane tank for cooking inside the van too (with a very safe/secure vented locker of course).

Power need: ~55Ah
Solar: 200W (x2 100W 12V poly panels in series)
Battery: 200Ah (x2 100Ah Renogy LiFePO4 in parallel) - $129
Inverter: 1000W PSW
Charge Controller: 20A MPPT (Rover) - $100
Battery Isolator: 20A B2B Charger

Midwestdrifter said:

I will reiterate my point, that LFP will charge rapidly and without issue from the alternator directly. You may need to put slightly smaller cable or fuse on the charging run to reduce current if its a bit higher than desired. You do not need to worry about "overcharging" unless you drive a ridiculous amount.

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I'm sure if you say it was enough times I'll get it through my thick skull eventually.

In doing my research about the use of LFP batteries, I'm seeing that it's beneficial to keep them charged at or around the 90% level? I do do a fair amount of driving, definitely daily, and since I'm only running a little minifridge and some led's, with the occasional tool or electric kettle, and then a camping trip once a month or two with some slightly heavier usage and the 2kw diesel heater, I'm thinking that if I always have alternator charging I'd end up overcharging. Do I have that right? I of course have a circuit breaker pre-battery Dr isolater, which I can use to manually shut off current if I'm driving a lot. Would the benefit of using the Kisae DMT1250 be that it's more of a set and forget solution, vs manually monitoring SOC and alt charging input?

Right now I'm thinking on the lines of the Kisae DMT1250 and the victron bmv-712 battery monitor. Anyone have thoughts on such a combo? Given my situation could it be a better idea to go with victron charge controller and battery monitor combo, since it seems they do some amount of communication together rather than mixing too many things together? I'm sure it comes down to personal preference to some degree, but any input appreciated...

Well I think I'm gonna go with the Kisae DMT1250 and Victron BMV-712. Seems like a good combo that does all I need it to from my research thus far. In all of my internet searching I came across this page that I thought might be helpful to reference here regarding alternator charging, LFP battery banks, vans and so on:

https://www.promasterforum.com/threads/anyone-charging-lithium-with-the-alternator.79506/

Hein sent me a reply from renogy about their BMS low voltage shutdown feature and what it takes to wake it up again:

Using the Noco to wake up the battery I have viewed the Noco pulse the battery once every five seconds for 14.4v on and off. The time frame for the battery to wake up with these pulses can take anywhere from 10 seconds to 30 minutes.

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He also said that the Kisae DMT1250 has the capability to wake up a battery that has been locked out by providing such a voltage, so I think I'll feel better about my system if I have a dc-dc charger and the Kisae does seem to fit the bill.


Thanks for all the help everyone. Hein, you'll likely be getting a call tomorrow...

Another question: I already had bit the bullet on a Victron 100/30. Is it better suited as a charge controller than the Kisae? Since it'll already be here today and I have a departure date of Dec. 18th for a 2-ish week trip I might just opt to use what I've got already.

Kisae literature is a bit blurry on the specs. Can't find Vmp value in their specs. Says PV DC input nominal operation is 35Vdc for 2 panels in series, which is what I have. Are those the same values? Nominal and Vmp? Tryna learn here.

I also can't find Imp for the Kisae, while I know the Victron is 30A.

I have two 100W panels now but I will likely upgrade to two 175W panels in the near future.

At his point my decision might just come down to timing. If you were to choose between the two what would you choose? I can still probably have time to order the Kisae and install if it is in fact a superior product.

The solar charger thrown in "free" with a DCDC unit will never be as effective nor full-featured as a dedicated unit from a leading vendor like Victron.

Great for keeping batteries topped up when a vehicle's stored outside far from shore power, but not well suited to optimizing charging for deep-cycling, living off-grid for more than a few days at a time.

There is no technical reason the combo DC/MPPT chargers cannot be as good as dedicated unit. That being said I have not seen any unit that tests as such. Though testing like that is hard to find in general. I do know of several units (not the kisae unit) which tested significantly lower than a dedicated quality unit.

Nominal voltage means just that "about". 12V nominal means 10-15V for example. A 35V nominal array can output 50V in very cold weather with clear skies. I suggest you ask them for the max Voc for the PV input.

Most MPPT controllers are rated in charging output as the max current. The same goes for DC-DC chargers. They almost always will self limit to avoid exceeding the output current limit. So the current ratings of the panels do not come into play. Obviously the panel wattage will limit the output if its less than the controllers max output.

Unless you drive ridiculous amounts, or are using excessive charge voltages, you will not need to worry about overcharging. Many MFGs state to use 14.6V for charging. As mentioned this is unnecessary (unless the BMS is dumb and won't balance below that level). Charging to 13.8-14.1V will still get you 99-100%. Charging at those lower voltages improves longevity, and reduces stress on the pack if its allowed to sit on that charge after it reaches 100%.

That was the purpose of my previous recommendation, the alternator is 13.8-14.2V, and thus is well suited to direct charging (once you verify the current limits).

I have used the Renogy for a couple months. I got it on sale for $199. I have it hooked to 200 AGM and 200 watt solar.
I am very happy with it so far. I am a weekend warrior and plan on using the van for a few week trip at most. If I was a full timer I may have gone a different route. For my application I am extremely satisfied. I love the all in one unit, less wiring and less components.
Time will tell how long it last but for the low cost I would absolutely buy one again

https://youtu.be/JtAUrS4zNSA

Does the 2019 have a"smart alternator"?

I was looking at the Kisae DMT1250 thinking of upgrading my alternator charging from the Mercedes ACR. I like the longer term Lithium compatibility.....will likely switch over at some point.....I can see some decline in my Fullriver AGMs though they likely have many years left...

Then I saw the Renogy version (DCC50S). Seems to be similar but smaller and less customizable in settings. You cannot set as much...….not sure you can set anything specific on the Lithium charge profile. The wiring is simpler in that there is only 1 ground connection. The smaller size would fit under my drivers seat in the shorter seat base where my current solar controller is. Not sure I like the lack of adjustable settings though...…….

Midwestdrifter said:

I will reiterate my point, that LFP will charge rapidly and without issue from the alternator directly. You may need to put slightly smaller cable or fuse on the charging run to reduce current if its a bit higher than desired. You do not need to worry about "overcharging" unless you drive a ridiculous amount.

Click to expand...

With this strategy for Lithiums can one set charge to stop at 90% to increase life? I have a Victron BMV700......perhaps that can turn on and off an isolator.

Regarding the wire size and current limits, would one use a wires size that would limit current to say 100A or something like that? The idea would be to create a voltage drop that would taper charging at high current I guess. So say you had 200 Ahrs of lithium, and a 8 ft run of wire. With AWG 6, at 100A voltage would drop from 13.7 to 13.07V. Would that be a reasonable choice? Wondering if there might be some experimentation to get the right size. PS: I do have the 6 cyl.