redarc bcdc1250d stuck on 13.6v with lifepo4?

[airbats801]

So I got my 200ah lifepo4 in my 4wd. I have it setup for lithium, and solar. the problem is. It wont go past 13.6v. The led shows its in boost solid red on stage, lithium, is show, and vehicle is lit up, the controller gets quite hot, but my voltage is only 13.55 to
13.6v at the house battery while im getting around 13.9 at idle on the engine battery and if I idle up a few hundred rpms its around 14.3 The redarc stays at 13.6. I dont think this thing is actually charing my new battery.. I'm about to head out on a 10 day camping/fishing trip and need this thing working Am I missing something or is this thing defective?

 

[john61ct]

Is this a dropin, where you do not have access to the BMS nor per-cell voltages?

Maybe it's become unbalanced, one cell/group is hitting the top setpoint early causing the BMS to isolate, protect the internal battery.

The good new is, 13.6V is already Full, and in fact a much healthier stop point than 13.8V or higher, good for longevity.

So you are likely fine for your trip, and can resume dealing with the imbalance issue when you return.

 

[DiploStrat]

I'm with john on this - I suspect that your battery is fully charged.

The engine voltage is a bit irrelevant as the whole point of the REDARC is that it takes from 9 to 32v and outputs according to its profile. I assume that you have tied off the correct jumpers and the beast shows it to be in Lithium mode.

Sounds like a new setup and a new battery. So:

-- What was the state of charge of the battery when you got it? Not the voltage, but the state of charge.

-- How big is the battery? 100Ah? Larger? Your REDARC will only charge at about 25A.

-- Assuming you did not bench charge the battery first, what kind of time are we talking about? If you are talking engine charge, how many hours? If a 100Ah battery, deeply discharged, with a 25A alternator, you are looking at over four hours of steady charge.

-- How much solar? You can expect about 5A of energy per 100w of panel in good sun. So, 5A into 100Ah = how long?

Most B2B's from any manufacturer tend to be pass/fail. If they are not dead on arrival, or soon after, then they tend to work forever. I suspect that you have a new battery that has not received a full charge.

Going on a trip is probably the best thing you can do.

With all the usual caveats about remote diagnostics and guessing, I hope this is useful.

 

[airbats801]

Its a 200ah lifepo4. came in with a voltage of 13.18

I decided to toss a load on it over a day of 2 fridges 45 and 35 engel. one running freezer and 1 running fridge just to take some juice out of it. solar im running 2 100w newpowa in peak light they are doing about 65w from testing, but its been sitting between trees at the house. The lowest I saw the battery everything unhooked was 13.08 the next day It is a sealed battery with internal bms

itsthe 50amp bcdc so should be able to do 50 amop. im running 6awg from the battery to the bcdc as it should be well within spoec for 50amp max draw, looking at maybe 8ft hydraulically crimped on both sides. the bcdc is sitting around 1.5ft from the house battery. Unfortunately I havent got a chance to wire up anything to monitor the amount of charge getting used or received yet as im out of time for it, but it's on the list.

it's just weird the bcdc says its in boost mode and not float mode but the voltage is only 13.6, and from what im reading boost mode should be around 14.4 or so

 

[DiploStrat]

...
it's just weird the bcdc says its in boost mode and not float mode but the voltage is only 13.6, and from what im reading boost mode should be around 14.4 or so

Lithiums don't work that way. They sit at around 13.3 - 13.5v all day long. The voltage does not vary like a lead acid. I have three 280Ah lithiums in parallel, in months of use only one has ever cracked 14v. But according to both the BMS's and the battery monitor, the batteries are fully charges. And based on running the air conditioner all night, that appears to be correct.

EDITED TO ADD: There is a difference between the output of the charger, in the case of the REDARC, about 14.4v and the voltage of the battery. The charger may well be putting out 14.4v but it can take days for the battery to actually reach that voltage.


If you have 200w, then you will get 10A of charge. Maybe 15A if the sun is perfect.

Even with the engine running, you will only see 50A from the REDARC if the battery is really hammered. (Sorry, I misread the size of B2B you installed.)

Sounds to me like everything is working properly, it just going to take a few days of driving or solar to complete the charge. But even then, you may not actually see 14v at the battery.

 

[john61ct]

Please answer the other questions I asked.

it's just weird the bcdc says its in boost mode and not float mode but the voltage is only 13.6, and from what im reading boost mode should be around 14.4 or so

It is common for "LFP compatible" sources and BMSs to be set way too high, right at the cells' spec sheet maximum.

Very stressful, zhortening lifespam of the cells by a lot.

One reason I do not recommend dropins and Redarc in general is afaik they do not accommodate user-custom adjustable setpoints.

The fact that your voltage at the posts does not exceed 13.6V may be unintentional

but afaic it is a happy accident.

The only issue is balancing, but with a functioning BMS worse case consequence there is slightly reduced capacity

deal with that after your trip.


BTW on discharging, do not let the batt dip below 12.4V for good longevity. The BMS LVC probably does not kick in until much lower, which is not good for longevity.

 

[airbats801]

Please answer the other questions I asked.

It is common for "LFP compatible" sources and BMSs to be set way too high, right at the cells' spec sheet maximum.

Very stressful, zhortening lifespam of the cells by a lot.

One reason I do not recommend dropins and Redarc in general is afaik they do not accommodate user-custom adjustable setpoints.

The fact that your voltage at the posts does not exceed 13.6V may be unintentional

but afaic it is a happy accident.

The only issue is balancing, but with a functioning BMS worse case consequence there is slightly reduced capacity

deal with that after your trip.


BTW on discharging, do not let the batt dip below 12.4V for good longevity. The BMS LVC probably does not kick in until much lower, which is not good for longevity.

cant tell you the state of charge as I has no bluetooth access to the cells as far as I know

specs are as follows coming from the seller.
Our battery parameters are as follows:
Rated voltage: 12.8V
Charging voltage: 14.4-14.6V
Cut off voltage: 10V
Depth of discharge (DoD): 100%
Standard charging current: 40A
Charging time: about 6 hours
Maximum continuous charging current: 100A
Maximum continuous discharge current: 100A
Peak discharge current: 240A (duration: less than 5 seconds)
Working Temperature Range:
Charge: 0°C--45°C (32°F~113°F)
Discharge: -20°C--60°C (-4°F~140°F)
If you charge a 12V 200ah battery using a solar application, please refer to the following data settings:
Charge
Charging limit voltage: 14.6V
Overvoltage breaking voltage: 15V
Overvoltage reconnection voltage: 14.2V
Equalizer charging voltage: 14V
Foating charge voltage: 13.8V
Boost charging voltage: 13.8V
Boost reconnection charging voltage: 13.2v
Discharge
Low voltage breaking voltage: 10.8V
Low voltage reconnection voltage: 12.4V
Under voltage warning voltage: 11.6V
Undervoltage warning reconnection voltage: 12V
Discharge limit voltage: 10.4V
Over discharge breaking voltage: 10.4V
Over discharge reconnection voltage: 11.6V

 

[jonyjoe101]

at 13.6 volts your battery will never get fully charged. Little by little it will drain to zero percent which happens quickly when the battery reaches about 20 percent. I might be the different one here because I charge my 220ah lifepo4 to 14.6 volts every day (for the past 3 years). While charging with solar I see 14.1 or higher all day long, if I saw 13.6 volts I be tearing everything apart looking for the problem. 13.6 volts is float voltage, with the battery getting very little amps.
Without the coulombcounter (to count the amps going in/out battery) there isn't an accurate way to monitor the battery condition. One thing about the lifepo4 they read about 13.1 volts the majority of the time between 20 and 80 percent, and at 20 percent it will operate as well as a full battery. Also the coulombcounter will need to read 14.4 or 14.6 volts to calibrate itself to 100 percent fully charge.
From your description, your battery can be anywhere between 20 and 80 percent, its such a large battery it will take several days to fully drain. 200 watt of solar will be very slow to charge your battery. From 50 percent discharged, it took my 240 watt panel almost 2 weeks to take my 220ah lifepo4 back to 100 percent. I would look at the redarc to see why its not reaching 14.4 volts. Maybe you have a modern alternator that doesnt stay at 14.4 volts all day long to conserve fuel.
With lifepo4 what you see is what you get, if you never see 14.4 volts while charging, your undercharging the battery. Undercharging is not bad for lifepo4, but your not going to know the accurate condition of the battery.

 

[john61ct]

at 13.6 volts your battery will never get fully charged.

Sorry but this is 100% false. 3.32-3.34Vpc at rest is 100% Full. You can charge at 100A available at 14.6V for days after that and add nothing to the actual energy stored, accomplishing nothing but unnecessary harm.

> Little by little it will drain to zero percent which happens quickly when the battery reaches about 20 percent

That will not happen unless the charger is not working, if it is outputting 13.6V (3.40Vpc) then that is perfectly fine to get the cells back to 100%.

OP, enjoy your trip, just keep an eye on your voltage, do not use the battery any further without recharging if it drops below 12V (3.0Vpc)

I won't get into a point by point argument on the rest of that post from jonyjoe for now, not relevant to OP, maybe another time after you get back.

As I mentioned , since this is a drop-in with no access to balancing info, that IMO is likely to be the cause of the problem, BMS kicking in, but that is something to deal with after the current trip.

 

[DiploStrat]

FWIW, and at least with my Overkill BMS, if you have a cell overvoltage, plugging in a decent load, e.g. a hair dryer/microwave/etc., for 30 seconds or so will quickly pull down a high cell.

 

[john61ct]

That is not being done by the BMS.

Imbalanced or balanced, only references a specific point in the SoC/volts curve

usually at the top.

go to a different SoC, the deltas are also completely different.

This is normal, not a sign of a problem.

 

[DiploStrat]

Agreed. I should have said, as measured by …

It is the load, not the BMS that pulls down the cell.

 

[jonyjoe101]

if you can get a dc wattmeter or something similar connected to your lifepo4 to see how much amps are actually going into the battery in real time. That will tell you everything you need to know.
On my system at 13.6 volts I get maybe 1 or 2 amps of charging power which is insignificant if your trying to charge the battery. The reason you need 14.4 volts or 14.6 volts to fully charge is the charger has to "force" the amps into your battery and that only happens at higher voltage.
If you just carry around the lifepo4 without ever using it eventually it might charge to around 80 percent at 13.6 volts, but as soon as you use it you need to replace those amps. And if everyday you use more amps then the charging is able to replace, the battery eventually reaches zero percent. Without a coulombcounter, this can happen quickly.
Charging your battery to 14.4 volts or 14.6 volts won't damage it, they are designed to be fully charge everytime. Charging to less voltage "might" get them to last longer, maybe you get 1 or 2 years longer life. I prefer "max" performance over "possible" longer life. 14.4 volts is recommended for drop-in lifepo4 since it wont trip the bms, and that is a better voltage then 13.6 volts.
This is the coulombcounter I been using for years TK15, they got them in different amp ratings, the 50amp model is in the 30 dollar range. With something like this you never have to guess what the battery SOC is.