LiFeP04 charge controller recommendations

john61ct

Adventurer
Really, best to buy best of breed single purpose, forget the combo gadgets.

A DCDC or smart-VR sized for your alt and bank type, always on whenever the engine is going

ideally able to be derated or turned off when full power is needed for propulsion.

And efficient MPPT SCs to get max conversion in all conditions from your panels.

Having both charging concurrently is NP.
 

ducktapeguy

Adventurer
Generally I'm happy with the system, but had one significant issue. I found it would favor the solar charging much too much, and not draw from the alternator, almost ever. I know that it is programmed to use the solar panels as much as possible. But I expected it would "top up" to the full 30A by drawing from the alternator. But it doesn't. There were times it would be getting 5A or less from the solar, and still not draw from the alternator. Did a lot of troubleshooting, but at the end of the trip, I learned to just unplug the solar if I wanted to be sure to draw from the alternator. The o
So far I'm satisfied with the Renogy. There are things that could be improved, but it works for my setup so I'm probably going to stay with it for now. Their bluetooth app is a little buggy and not as good as the Victron, but it gives me the basic information that I want to see.

I have read about an issue where the alternator input is limited when the solar is connected, but I seem to recall it was more of a 50/50 split (i.e. 15A from the alternator and 15A Solar), even when the solar was only outputting a few amps. The only issue I have seen is when the DCC30S is drawing from the starting battery when it shouldn't be. Engine off, night time, sometimes I still see it drawing power from the starting battery down to 12.3V when it should be cutting off at 12.7. I don't know if this is due to the IGN wire hookup for "smart alternators", I tested it with and without it and didn't see much of a difference so I left it off. It hasn't bothered me enough to really dig any deeper into it, since the house battery and start battery will eventually get charged from the panel everyday. Also, I also have never seen anywhere close to 30A output from it, even with a discharged lithium capable of charging at 50A.

Really, best to buy best of breed single purpose, forget the combo gadgets.

A DCDC or smart-VR sized for your alt and bank type, always on whenever the engine is going

ideally able to be derated or turned off when full power is needed for propulsion.

And efficient MPPT SCs to get max conversion in all conditions from your panels.

Having both charging concurrently is NP.
Possibly for a more complicated system then it would be worth the effort to set it up with independent charging from either source. But the dual charging inputs of the Renogy makes installation and wiring a lot easier for simple electrical setups like mine, especially on vehicles with already limited space in the engine compartment. The one thing I really like about the Renogy is it automatically switches the excess solar panel capacity to the starting battery when the house battery is fully charged. I'm sure something like that could be setup DCDC charger and MPPT, but with a lot more hassle and expense. I don't ever plan on upgrading beyond a single solar panel and battery, so having a more complicated setup is overkill.
 
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Superduty

Adventurer
Again, the canned profiles from all makers are not conducive to longevity.

User-custom profile adjustability is what makes a good LFP charge source

not marketing materials touting "Lithium compatible"

volts are volts, amps are amps

Do you have recommendation for a lifepo4 profile that would be conducive to longevity? I use a Victron MPPT and a 100ah lithium battery.
 

R_Lefebvre

Expedition Leader
So far I'm satisfied with the Renogy. There are things that could be improved, but it works for my setup so I'm probably going to stay with it for now. Their bluetooth app is a little buggy and not as good as the Victron, but it gives me the basic information that I want to see.
So what kind of information can you get from the bluetooth system? I can get the basics from from my battery monitor, though some of it is from inference. For example, I might see 10A coming in (typical for my setup) but I know the fridge is running which typically draws about 8A, so the solar must be taking in 18A. But it's far from perfect, requires more thought, etc. Very often I would actually have to manually shut off all the loads so that I could understand what was actually coming in. The flipside though is that, as I get more comfortable with living with the system I built, I really don't want to concern myself too much with this anyway. I've already done 4 days in a row with cloudy weather, no driving, and no shore power, and we only went down to 30% battery without too much sacrifice.

The big thing for me is more control. For example, telling it to take 30A from the alternator, or not, instead of having to actually go and unplug my panels, etc.

I have read about an issue where the alternator input is limited when the solar is connected, but I seem to recall it was more of a 50/50 split (i.e. 15A from the alternator and 15A Solar), even when the solar was only outputting a few amps. The only issue I have seen is when the DCC30S is drawing from the starting battery when it shouldn't be. Engine off, night time, sometimes I still see it drawing power from the starting battery down to 12.3V when it should be cutting off at 12.7. I don't know if this is due to the IGN wire hookup for "smart alternators", I tested it with and without it and didn't see much of a difference so I left it off. It hasn't bothered me enough to really dig any deeper into it, since the house battery and start battery will eventually get charged from the panel everyday. Also, I also have never seen anywhere close to 30A output from it, even with a discharged lithium capable of charging at 50A.
Yeah, that's exactly the issue, and the system does not do what's expected. It's two 15A circuits, and if it's getting 0<x<15A from solar, it should take 15A from the alternator on the other circuit. But it does not. It won't even start to draw from the alternator until the solar is down really low, like 5A. So, I might be driving all day, and know the solar is not coming strong, and the batteries are low so I want to charge them as much as possible. I have to actually unplug the solar so that it pulls from the alternator.

On your issue, check your wiring. I had a weird issue, but it was a wiring mistake. I have a slightly different setup. My system is installed in a trailer, which has the standard 7-pin trailer cable, which includes a feed from the truck battery to the 12V bus on the trailer. I retrofit the trailer to make this off-grid system, and added a 50A umbilical to the truck for these high charging loads. So the Renogy DC-DC draws from that umbilical, and then dumps it into the 12V bus. I forgot in my retrofit, that I needed to cut the 12V wire from the trailer 12V bus to the 7-pin connector. So, I had this weird loop thing going on, where the DC-DC was pulling from the truck battery, boosting the voltage to charge the trailer batteries, which was backfeeding via the 7-pin connector into the truck... I'm surprised something didn't let the smoke out honestly. Over night, it was basically dissipating all the battery power as heat in the boost-buck converter in the DC-DC. The only reason I actually noticed this was happening, was I went to do some work on the batteries, disconnected the batteries, and the umbilical, and found I still had 12V coming from somewhere... the 7-pin connector.

Possibly for a more complicated system then it would be worth the effort to set it up with independent charging from either source. But the dual charging inputs of the Renogy makes installation and wiring a lot easier for simple electrical setups like mine, especially on vehicles with already limited space in the engine compartment. The one thing I really like about the Renogy is it automatically switches the excess solar panel capacity to the starting battery when the house battery is fully charged. I'm sure something like that could be setup DCDC charger and MPPT, but with a lot more hassle and expense. I don't ever plan on upgrading beyond a single solar panel and battery, so having a more complicated setup is overkill.
Agreed on all points. I may end up moving the DCDC to the truck, as I still intend on having a house battery in the truck, and then setting up the trailer with a stand alone DCDC charger plus a stand along MPPT. Or, move the 30A DCDC to the truck, and put a 50A DCDC in the trailer.
 

john61ct

Adventurer
Do you have recommendation for a lifepo4 profile that would be conducive to longevity? I use a Victron MPPT and a 100ah lithium battery.
Stop charging at 3.45Vpc maybe 3.55Vpc if current below say 0.2C

No CV / Absorb time needed, but I think those SC have a minimum, NP.

No need to shut off the solar, just isolate the LFP

if you have loads running use a cheap lead batt to buffer keep feeding them.

_______
On the discharge side, stop well before 3.1Vpc for light draws

3.0V absolute bottom if loads are high current, say over 1C.
 

john61ct

Adventurer
I saw this in another forum: Using an MPPT as DC to DC

Any reason why this wouldn't work or would be dangerous (I think this is along the same lines of what is being discussed in this thread)?


View attachment 681132
I've seen reports of Victron SCs acting weird trying to do that

but that may well depend on the characteristics of the input power "pretending" to be solar panels.

Higher than 21V might be better than lower.

Do not exceed the wattage spec' by more than say 20%

And def keep any eye on it all
 

R_Lefebvre

Expedition Leader
Do you have recommendation for a lifepo4 profile that would be conducive to longevity? I use a Victron MPPT and a 100ah lithium battery.
This is a complicated topic, but I've done a lot of research into it, and bring previous experience from the drone industry.

There's a lot of things that go into this. Basically, every charge cycle "damages" the battery by the formation of dendrites. Think of it like "cumulative damage". Every time you charge the battery, they accumulate damage, but there's things you can do to minimize it.

1) The lower the final charge voltage is, the less damage is done. If for example, you only charged to 13.6V instead of 14.4V, you make make major improvements to life cycle, while only losing a relatively small amount of capacity, on the order of 5-10%.
2) Similarly, the smaller your charge cycles are the less damage is done. This combines with point 1 above. For example, if you could cycle your batteries between 30-70% state of charge, you should get >10,000 cycles out of them. And cycling between 30-70% is better than cycling between 60-100%.
3) Also, the rate of charge plays a role. The higher the rate of charge, the more damage is done. Same for discharge.

When operating on solar, chances are, there's not much you can do here. You probably won't be charging fast in any case. And you'll probably need to use the full capacity of your battery in many cases. However, if you can withstand the weight, having extra batteries will help. ie: you could have one battery, it costs $1000 and weighs 50lbs. You use it to the max, and it's worn out after 3000 cycles, when you have to buy a new battery for another $1000. But if you bought two batteries upfront, and were stressing them less, they might last 30,000 cycles for the same amount of money, you're just carrying an extra 50lbs.

The real game gets started when hooking up to shore power. If you hammer them with a high charge current unnecessarily, you're doing damage you don't need to do. Also, and I'm still researching this, but considering setting up a float charge. LiFE batteries do not NEED a float charge. But they may benefit from one set up in the charger. But you wouldn't want to float at 14.4V. I'm thinking of setting up the shore power charger to only charge to 13.6V, and then float at 13.6V. The concept is to essentially "hold up" the system voltage when it's under load, so that the charger is supplying the power, rather than the batteries. Because right now, my charger starts at 13.5V, and then shuts off at 14.4V. Then the batteries carry the load until they discharge, and the charge cycles starts again. This is cycling the batteries in the 90-100% range, when really, they shouldn't be cycling at all.

I have reduced my shore power charge current to 15A from the max of 75A, because I find that if I have shore power, I usually have it for a long time, and the slower charge rate is just better for the batteries.
 

john61ct

Adventurer
Great to see such deep knowledge, some minor quibbles here.

Basically, every charge cycle "damages" the battery by the formation of dendrites. Think of it like "cumulative damage".
Ordinary wear and tear even under ideal coddling care conditions includes many incremental factors. Dendrites are drastic, signs of gross abuse, especially high C-rates. Of course that may be required by the needs of the use case, lower cycle life accepted as necessary.


> Every time you charge the battery, they accumulate damage

Every time you cycle, either / both charge & discharge usage patterns are at play.

And let's keep the term "damage" to mean "reduce longevity" as in departing from optimal coddling care conditions.

For example, a LFP pack lasting over 10000 cycles, or LTO 10x that, has not suffered damage as such, at all.

> The lower the final charge voltage is, the less damage is done.

This is only true down to 3.40V for LFP, and 4.05V for li-ion / LiPo. There is no detectable longevity increase by stopping charge before those points.

And assuming charging terminated before current trails to 0.01C, Floating **at any voltage** is likely reducing longevity.

See below for details


> And cycling between 30-70% is better than cycling between 60-100%.

Actually yes, sacrificing lots of capacity, and cycling around the midpoint is indeed optimal, but the cost is just not practical for private use cases much less consumer owners. Fine for NASA sending cells into space for decades long use cases though.

> The higher the rate of charge, the more damage is done. Same for discharge.

Yes, charging at 0.4C and discharging below 1C is very gentle, higher shortens lifespan. But very temperature dependent, this is at 77°F/25°C.

Pre-heating cells allows for much higher charge rates and much better discharge performance. Fast charging in Arctic ambients can instantly render a bank worth thousands into scrap.


> considering setting up a float charge. LiFE batteries do not NEED a float charge.

No, see above, Floating is for other chemistries, always damaging to LI.

Most of all, never leave any LI chemistry cells not currently being cycled at high SoC% for long periods of time.

If the charging / power source is used to feed loads, use a cheap lead batt as buffer and take the LI bank offline with contactors or manual switches.

Only charge the cells soon before loads need feeding, obviously within the constraints of practicality and the use case's needs.

> if I have shore power, I usually have it for a long time, and the slower charge rate is just better for the batteries

Generally true, but going **too low**, say under 0.05C risks overcharging, need to switch to CC only profiles, simple HVC, not holding CV / Absorb for long if at all.

And the voltage setpoint needs to be tweaked down, especially with LFP, say to 3.35V
 

john61ct

Adventurer
Check with the battery provider. They will tell you the ideal profile for their batteries.
No. Nearly the whole industry has adopted charge-termination voltage / endAmps profiles **way too high** for those striving for maximum longevity.

The cell manufacturers datasheets specify absolute maximum ratings for safety purposes, the maximum voltage you should ever subject the device to under any conditions, IOW stay well away

These are absolute stress ratings only, functional operation of the device is not implied at these or any other conditions in excess of those given in the operations sections of the data sheet.

Exposure to absolute maximum ratings for extended periods can adversely affect the device reliability.

Given LFP charged to 3.34V isolated and at rest is already 100% Full

there is absolutely no reason to go all the way to 3.60V

Just causes waste energy dissipating as heat and damaging chemical activity.

Keep in mind also, that planned obsolescence is pretty much universal in a "free market" economy.
 

4000lbsOfGoat

Well-known member
No. Nearly the whole industry has adopted charge-termination voltage / endAmps profiles **way too high** for those striving for maximum longevity.

The cell manufacturers datasheets specify absolute maximum ratings for safety purposes, the maximum voltage you should ever subject the device to under any conditions, IOW stay well away

These are absolute stress ratings only, functional operation of the device is not implied at these or any other conditions in excess of those given in the operations sections of the data sheet.

Exposure to absolute maximum ratings for extended periods can adversely affect the device reliability.

Given LFP charged to 3.34V isolated and at rest is already 100% Full

there is absolutely no reason to go all the way to 3.60V

Just causes waste energy dissipating as heat and damaging chemical activity.

Keep in mind also, that planned obsolescence is pretty much universal in a "free market" economy.
Battle Born gave me very specific instructions for how to correctly program a charger for their batteries. The batteries that they gave me a 10 year warranty on. Just stay away from cheap batteries from a faceless company....
 

ducktapeguy

Adventurer
I saw this in another forum: Using an MPPT as DC to DC

Any reason why this wouldn't work or would be dangerous (I think this is along the same lines of what is being discussed in this thread)?


View attachment 681132
Tried it, didn't work for me. I posted my experience earlier in this thread. In theory it should work, and it sounds like other people have made it work. I was hoping it would be that simple, but I guess if all it took was hooking up a cheap boost converter to a MPPT then specific DC/DC chargers wouldn't exist. I never tried to trouble shoot the issue because in my mind it wasn't worth the trouble and I didn't want to worry about the reliability or safety of my electrical system which is the reason I ended up with the Renogy
 

Superduty

Adventurer
Tried it, didn't work for me. I posted my experience earlier in this thread. In theory it should work, and it sounds like other people have made it work. I was hoping it would be that simple, but I guess if all it took was hooking up a cheap boost converter to a MPPT then specific DC/DC chargers wouldn't exist. I never tried to trouble shoot the issue because in my mind it wasn't worth the trouble and I didn't want to worry about the reliability or safety of my electrical system which is the reason I ended up with the Renogy

I'm sorry I missed where you said you tried it and it didn't work. I saw where you said you read about it. Did you set up your system exactly like the diagram I posted? It seems to work well for the user that posted it on the other forum, and after reading numerous posts from him, he seems to know a little bit about electrical and solar.

What problem did you run into?
 
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