DC to DC charger / battery compatibility

[Master Dalor]

Hello friends, I am about to build my first DC power system, using Renogy's DCC50S Battery Charger and a 60Ah Lifepo4 battery from Amped Outdoors, based on this blueprint: https://www.mobile-solarpower.com/simplified-400-watt-fewer-wires-and-alternator-charging.html (in this case no solar panel or inverter for now).

Quick question, I noticed the label on the battery says "Max current: 50A" I assume this refers to the max draw you can put on the battery, but does it also apply to charging current?

I remember in Will's review of the DCC50S that the charging current might have slightly exceeded 50A at times. Just want to make sure that wouldn't be a problem for this battery.

Also I assume that if I set the DCC50S to the Lithium battery setting, it will charge this battery properly, even though Amped Outdoors says never to use anything but the AC charger they sell.

on here it states 25 amps from alternator

 

[John Frum]

on here it states 25 amps from alternator

In the manual page 15 https://www.renogy.com/content/RBC50D1S-G1/RBC50D1S-Manual.pdf
"1.3 The maximum alternator charging for the DCDC30 is 30A and the DCDC50 is 50A."

 

[Master Dalor]

The second battery will disconnect if starting battery is under 12.7 V with traditional alternator, 11.5V with smart alternator witch is connected to the controller with communication cable, so, the 50amps are given by the starting battery, not overloading the alternator.

 

[Master Dalor]

I can't see any model number, when I receive it, I'll tell you.

 

[John Frum]

The second battery will disconnect if starting battery is under 12.7 V with traditional alternator, 11.5V with smart alternator witch is connected to the controller with communication cable, so, the 50amps are given by the starting battery, not overloading the alternator.

DC to DC charger / battery compatibility

Hello friends, I am about to build my first DC power system, using Renogy's DCC50S Battery Charger and a 60Ah Lifepo4 battery from Amped Outdoors, based on this blueprint: https://www.mobile-solarpower.com/simplified-400-watt-fewer-wires-and-alternator-charging.html (in this case no solar panel...

diysolarforum.com

 

[John Frum]

Will did a video on this product.

A lifepo4 battery stunt doubles for the starter battery and an inverter/charger stunt doubles for the alternator.
The alternator better handle the load or the starter battery will be discharged which is obviously not good.

 

[Master Dalor]

Will did a video on this product.

A lifepo4 battery stunt doubles for the starter battery and an inverter/charger stunt doubles for the alternator.
The alternator better handle the load or the starter battery will be discharged which is obviously not good.

Ok, it pulled 51 Amps, but from a battle born which as no voltage sag, the lead acid starting battery will sag, and will rapidly get under 12.7V especially just after engine starting not being sucked off see at 4:10 the charge will resume from 13.2V. In the test he says that the charger senses voltage, but later, says to connect the bvs to the battery for better sensing, also at the beginning when the 2 batteries were close in volts, the pull was around 30 amps. Then he discharged deeply the house battery to get the max amp, it's true that we saw 51 amps, but those conditions would almost never occurre in normal use, with bvs connected an lead acid as source battery.

(So Miles, if you forget to cut off the house loads, and you deeply discharge the house battery, you should be careful. If it's night check the starting battery voltage, drive for 2 hours at high RPM without the house battery connected to charge the starting battery :D :D :D Then reconnect and drive again for hours hehehe, it could do the trick, but man, i wouldn't do that.)
Seriously I think as you sayed before, if there is volts in pv in the amp draw will be max 25 amps and it should be ok. Even if there's no solar imput the charger will sense the voltage drop and not kill the alternator. Maybe but I know joey wants to kill it. Let's ask will to do the test on a real car.

 

[Miles]

Ok, it pulled 51 Amps, but from a battle born which as no voltage sag, the lead acid starting battery will sag, and will rapidly get under 12.7V especially just after engine starting not being sucked off see at 4:10 the charge will resume from 13.2V. In the test he says that the charger senses voltage, but later, says to connect the bvs to the battery for better sensing, also at the beginning when the 2 batteries were close in volts, the pull was around 30 amps. Then he discharged deeply the house battery to get the max amp, it's true that we saw 51 amps, but those conditions would almost never occurre in normal use, with bvs connected an lead acid as source battery.

(So Miles, if you forget to cut off the house loads, and you deeply discharge the house battery, you should be careful. If it's night check the starting battery voltage, drive for 2 hours at high RPM without the house battery connected to charge the starting battery :D :D :D Then reconnect and drive again for hours hehehe, it could do the trick, but man, i wouldn't do that.)
Seriously I think as you sayed before, if there is volts in pv in the amp draw will be max 25 amps and it should be ok. Even if there's no solar imput the charger will sense the voltage drop and not kill the alternator. Maybe but I know joey wants to kill it. Let's ask will to do the test on a real car.

Agreed, I think adding a solar panel in the mix will keep the system balanced. My understanding from reading the manual is that the charger already samples the voltage from the starting battery on the main positive lead. They say to add the bvs if you're doing a long run between the starting battery and the charger, which I'm not planning to.

 

[Master Dalor]

Agreed, I think adding a solar panel in the mix will keep the system balanced. My understanding from reading the manual is that the charger already samples the voltage from the starting battery on the main positive lead. They say to add the bvs if you're doing a long run between the starting battery and the charger, which I'm not planning to.

Ok. It will be fine. Thank you, Miles, I've learned some more things, and thank you Joey, for digging, and make me dig too. See you.

 

[Miles]

I figured I'd get the Renogy perspective on this. Got a nonsensical answer:

My help ticket email:
On Thu, 10 Sep at 2:39 PM , Miles wrote:
I have just received a new DCC50S DC to DC battery charger (https://www.renogy.com/dcc50s-12v-50a-dc-dc-on-board-battery-charger-with-mppt/), and am planning to use it to charge my 60Ah Lifepo4 battery I purchased from Amped Outdoors (https://ampedoutdoors.com/products/55ah-lithium-battery-lifepo4-series-capable).

This battery says on the website: "Charge Current: 50A Max". I want to make sure the charger will not push more current than the battery can safely handle.

Another concern is that the website for the battery says to only use their AC charging device. Is it safe to charge this battery using the DCC50S?
"Charging: All Amped Outdoors Batteries should be charged with one of our offered LiFePO4 chargers for best results. SLA and other lithium chargers may not fully charge a LiFePO4 battery with BMS, or can give false charge indications."

"Charging: All Amped Outdoors Batteries should be charged with our LiFePO4 approved chargers. SLA and other lithium chargers may not fully charge a LiFePO4 battery or recognize the battery when the BMS trips."

Thank you, Miles"

Renogy response:
"Hi Miles, Thank you for you taking the time to reach out to us here at Renogy Solar, much appreciated. Now you wont have to worry as the DC50 max charging amperage is 50 amps at any given point. I would even say less than that because the DC50 is actually programmed to give 50% of its 50 max amps to the starter battery and then 50% to the aux battery which for you in this case is the lithium battery."


This answer makes no sense. Wondering if this guy is even talking about the same product?

 

[Master Dalor]

It makes some sense, he just read the description like we did first, having no other information.

 

[Miles]

I got my system assembled and it's working nicely so far! Getting ready to test alternator charging.

I also wrote to Amped Outdoors to ask them about charging, and they responded that it's better not to exceed 0.5c charging speed, which in this case would be 30A (I think someone said something to that effect earlier, but I'm still learning how this works).

@Master Dalor and @smoothJoey if you don't mind a brief follow up question:
If it's not convenient to connect a solar panel when I'm alternator charging, would it make sense to trick the Renogy charger by giving the solar positive terminal a small amount of power? That way it thinks there's a solar panel attached, and limits the alternator current to 25A.

Wondering if it's possible to connect to the same positive feed and divert say 5A of power to the PV input terminal, or is the DC to DC charger going to draw the full 25A from both lines anyway, thus defeating the purpose. Hoping there might be some kind of amperage limiter device I could install.

 

[Master Dalor]

As you said, if it's advisable to connect the car battery to both in, battery and solar, witch I'm not sure it is, it would most likely go to 50 amps, and the solar side wouldn't recognize the 12.7 volt low battery state, and maybe kill it and the alternator aslo, instead, you could go thru a little dc to dc cv cc (constant voltage, constant current) like those I bought, on the pics here, or another model if you want, and when you have solar, that module can be used for many other things. I think the combat ingeneer on YouTube manage to burn parts of his 3806, or was it a DROK , I'm not sure, but if you limit the current to minimum amp necessary for your solar imput, I think it could work. There are lots of reviews on YouTube about those dc dc converters to watch.

 

[Miles]

As you said, if it's advisable to connect the car battery to both in, battery and solar, witch I'm not sure it is, it would most likely go to 50 amps, and the solar side wouldn't recognize the 12.7 volt low battery state, and maybe kill it and the alternator aslo, instead, you could go thru a little dc to dc cv cc (constant voltage, constant current) like those I bought, on the pics here, or another model if you want, and when you have solar, that module can be used for many other things. I think the combat ingeneer on YouTube manage to burn parts of his 3806, or was it a DROK , I'm not sure, but if you limit the current to minimum amp necessary for your solar imput, I think it could work. There are lots of reviews on YouTube about those dc dc converters to watch.View attachment 22702View attachment 22700View attachment 22702

Thanks @Master Dalor! I'll look into this idea. Good point about the solar not having a low voltage cutoff.

 

[Master Dalor]

No problem. I might add that the small converter 0.5v 30v has built in diodes to not feed the current back in, in the case, later if you want to charge batteries directy with it.
You can add diodes on the 3806, but than the voltage reading wouldn't be accurate on his screen, because of the diodes voltage drop.
For your solar charge controller it doesn't matter, because it will not feed back in the converter.
Another point, the converter should be disconnected from the battery when not needed, otherwise, it will continue to discharge the starter battery.
To do that, you can simply put a manual switch, that can be forgotten to swich off, and on, not so good, or use a 12v source driven by the contact key directly, there is one for the autoradio, if you don't pull to much amps, I think its not a big fuse on that circuit, or use it to power a relay, it consume some electricity, but only when in use.
Voilà, that's all I can think about for now.

 

[Master Dalor]

Thanks @Master Dalor! I'll look into this idea. Good point about the solar not having a low voltage cutoff.

I just read renogy's response again, I'm not sure what he means saying it charges 50% in the starting battery and 50% in the house battery, but, it makes me think that the pv should recharge also the starting battery, and maybe there could be a conflict somewhere, when the starting battery is solar source as well, now using the dc dc converter could get over that, or it's not clear in my head right now, cause problems of common ground, let's hope Joey will show to tell us that everything will blow and burn in hell fire. Hehehe :D
That question could fry an Isaac Asimov's robot brain putting it into an endless loop.