Redarc1240D vs Lifepo4 ?

[Bravo30]

A recent thread here (flat bed camper build) has got me thinking about my decision to go with a Redarc 1240D DCDC charger for my STARKPOWER 125AH Lifepo4 Batteries. I should start off by saying my situation is a bit different than typical van converison. I have a 2013 Mercedes Sprinters that's built out as a multi-use van. The majority of the time the van will be hauling furniture and then maybe 1-2 MONTHS out of the year ill be on road trips or van camping. This is what lead to my concerns with the Redarc. through my research here and online it seems that float charging a full or near full Lifepo4 can damage them. A phone call to STARKPOWER confirmed this.

Last night i called Redarc and their stance, contrary to most everything ive read is that i will have no issue with my batteries if i use the Li charge profile on their unit with a max charge of 14.5v and max float of 13.6v. (STARKPOWER recommends max 14.6) I just sent another email over to STARKPOWER to get their final take on the issue and after hearing from them i plan to call Sterling Power and discuss options with them. I also spoke with Victron and they recommended a Buckboost.

I think technically i could get by with the Redarc and could possibly make it work with some additional components but i want a drop in charger that i can walk away from. i dont want to install multiple pieces and then have to baby sit things. i dont have the technical background or patients for that.

 

[DiploStrat]

Scholars differ on charging lithium batteries and, as I don't have them, I have to caveat that my comments are based on reading, not on personal experience in my own vehicle.

That said, my impression is that lithiums, specifically LiFePO4, do best with a lower charge voltage, say about 14v, and then no, or an extremely low float voltage, say close to 13v. This is based on a visit to Starkpower and some long chats with their chief engineer. This is actually closer to the old gel battery profile.

Both the battery manufacturers and the charger manufacturers are under TREMENDOUS pressure to make it appear that LiFePO4 batteries are plug-and-play replacements for lead acid and that the profiles which the charger folk have worked so hard to perfect for lead acid will work for LiFePO4.

The good news is that LiFePO4 batteries have an extremely low self discharge rate. For the use you out lined I would simply but a brute force on/off switch ahead of the B2B. Charge up your batteries and then turn off the charger until you go camping again. Dead easy.

N.B. The REDARC charger, DCBC 1240D is a buck/boost device. This simply means that it can reduce (buck) voltage as well as raise (boost) it. The first generation of Sterling B2B were boost only products. According to their website, all of their current products can reduce voltage as well as boost it. If you choose to go with Sterling, you might try running a gel profile, which has more conservative voltages.

In the end, with chargers limited to 40A or less, the exact voltage is may not be that great of an issue, as long at it does, in fact, drop back below 14v once the battery voltage rises to around 14v. Also remember, a charger run off the vehicle alternator is only going to be charging about six hours a day, unless you have solar. And even with solar, you only get about 12 hours a day. That means that there are about 12 hours a day when your batteries are going to be sitting or discharging. The ideal float voltage is much more of an issue for a charger that is connected to shore power 24/7. So, in the real world, I suspect that it is simply not an issue.

But again, I do not have any real world experience. As you noted, Terra Ops is playing with a REDARC charger connected to Starkpower batteries.

Possibly the only way to get a truly plug-and-play lithium set up is to stay entirely within one manufacturers's universe, e.g. Mastervolt or Victron.

 

[CoyoteThistle]

[DiploStrat posted while I was typing - sorry for the redundancy]

Following along and looking forward to hearing your experiences with this approach. Couple comments:

- If you don't need the house batteries while in furniture hauling mode, you might consider just discharging the batteries to about 50% SOC and disconnecting the charger. They will sit happily for months and months. I assume the Redarc will get the batteries up to 14.5v every time you start the truck in the morning, which isn't real good for them. Turn the Redarc back on before you go camping and you're back in business.

- Very interesting that STARKPOWER told you (admitted) that float charging their batteries is bad. They sell these as being suitable to drop-in to systems designed for lead acid, which almost always have something equivalent to float charging. That's just an aside, but kudos to you for designing a more appropriate system and not just dropping-it-in.

- I look forward to seeing how the 14.5v and 13.6v settings work in practice. They both seem a bit high. I have my float (solar) at 13.40v now and I get zero current flow until the battery drops to about 98% SOC.

Thanks for posting. The Redarc might be a real good simple approach to charging LiFePo4, if not perfectly, much better then just dropping it in.

matt

 

[Bravo30]

Scholars differ on charging lithium batteries and, as I don't have them, I have to caveat that my comments are based on reading, not on personal experience.

That said, my impression is that lithiums, specifically LiFePO4, do best with a lower charge voltage, say about 14v, and then no, or an extremely low float voltage, say close to 13v. This is based on a visit to Starkpower and some long chats with their chief engineer. This is actually closer to the old gel battery profile.

That said, both the battery manufacturers and the charger manufacturers are under TREMENDOUS pressure to make it appear that LiFePO4 batteries are plug-and-play replacements for lead acid and that the profiles which the charger folk have worked so hard to perfect for lead acid will work for LiFePO4.

The good news is that LiFePO4 batteries have an extremely low self discharge rate. For the use you out lined I would simply but a brute force on/off switch ahead of the B2B. Charge up your batteries and then turn off the charger until you go camping again. Dead easy.

N.B. The REDARC charger, DCBC 1240D is a buck/boost device. This simply means that it can reduce (buck) voltage as well as raise (boost) it. The first generation of Sterling B2B were boost only products. According to their website, all of their current products can reduce voltage as well as boost it. If you choose to go with Sterling, you might try running a gel profile, which has more conservative voltages.

In the end, with chargers limited to 40A or less, the exact voltage is may not be that great of an issue, as long at it does, in fact, drop back below 14v. Also remember, a charger run off the vehicle alternator is only going to be charging about six hours a day, unless you have solar. And even with solar, you only get about 12 hours a day. that means that there are about 12 hours a day when your batteries are going to be sitting or discharging. The ideal float voltage is much more of an issue for a charger that is connected to shore power and on 24/7. So, in the real world, I suspect that it is simply not an issue.

But again, I do not have any real world experience. As you noted, Terra Ops is playing with a REDARC charger connected to Starkpower batteries.

Possibly the only way to get a truly plug-and-play lithium set up is to stay entirely within one manufacturers's universe, e.g. Master volt or Victron.

That makes sense. so at the end of the day, even if a float charge is harmful it will be negligible. i can live with that. when im not camping ill probably swap out the Lifepo4 with a few AGM's just to keep the lights working in the van then store the lifepo4 inside at the correct SOH.

when you say ''brute force on'off switch'' your just talking about a regular on/off battery switch correct? i just googled brute force and got Kawasaki atv stuff.

 

[Bravo30]

[DiploStrat posted while I was typing - sorry for the redundancy]

Following along and looking forward to hearing your experiences with this approach. Couple comments:

- If you don't need the house batteries while in furniture hauling mode, you might consider just discharging the batteries to about 50% SOC and disconnecting the charger. They will sit happily for months and months. I assume the Redarc will get the batteries up to 14.5v every time you start the truck in the morning, which isn't real good for them. Turn the Redarc back on before you go camping and you're back in business.

- Very interesting that STARKPOWER told you (admitted) that float charging their batteries is bad. They sell these as being suitable to drop-in to systems designed for lead acid, which almost always have something equivalent to float charging. That's just an aside, but kudos to you for designing a more appropriate system and not just dropping-it-in.

- I look forward to seeing how the 14.5v and 13.6v settings work in practice. They both seem a bit high. I have my float (solar) at 13.40v now and I get zero current flow until the battery drops to about 98% SOC.

Thanks for posting. The Redarc might be a real good simple approach to charging LiFePo4, if not perfectly, much better then just dropping it in.

matt

ive gotten different answers from them for each time ive called STARK. i wouln't necessarily say they were being deceptive or lying or anything but more like playing a bit lose with the words. I think, as Diplostat stated, they are under a lot of pressure to produce a drop in product and i think that pressure can be seen in their differing replies. I get it, its business. they've been very helpful to and put out a solid product.


I called Sterling Power as well today an theyre saying that Mercedes specs no more than 40amps charging off of their alternators so they recommended the BB1230, a 30amp charger. thats not enough for what i need. 30amps on 20% SOc would be close 6 hours of charging. i need to be around 4 hrs so i will be sticking it out with Redarc and an on/off switch.

 

[Terra Ops]

I've just begun testing the REDARC with Stark Lithium batteries.
My observation so far; if I kill the batteries to the coach and just allow solar charging, I've seen a max charge of 14.1.
As soon as I turn the switch back on with no inverter activated just 12v units such as water pump, TV, and fridge,
the charge starts to gradually drop to 13.6 and seems to stay there all day. I have yet to do any traveling for real world testing.
I did turn the fridge on after sun down to see what the draw down looks like. I'll post on that tomorrow.

 

[DiploStrat]

That makes sense. so at the end of the day, even if a float charge is harmful it will be negligible. i can live with that. when im not camping ill probably swap out the Lifepo4 with a few AGM's just to keep the lights working in the van then store the lifepo4 inside at the correct SOH.

when you say ''brute force on'off switch'' your just talking about a regular on/off battery switch correct? i just googled brute force and got Kawasaki atv stuff.

I would not bother to swap out the lithiums. I would:

-- Install a proper, lithium compatible, battery monitor, and,

-- put a simple on/off switch, which might simply be a properly sized circuit breaker, between the starter battery and your camper battery, and,

disconnect the BCDC 1240D from the starter battery when you are not camping. You can probably ignore however much solar you may attach.

As Matt noted above, lithium batteries have extremely low self discharge rates and they will be happy to provide any incidental power you may need in the off season.

Keep it simple.

 

[Rando]

I am not sure you need the Redarc, unless you alternator voltage is really low. A simple charge relay should be fine, and easy to override when you want the lithium batter to just sit. I use and SI-ACR and solar set up with my 150Ah LiFePO4 and it works beautifully. It seems to be a common misunderstanding the lithiums need high charge voltage. 13.6V will get you to 98% SOC.

 

[Bravo30]

I am not sure you need the Redarc, unless you alternator voltage is really low. A simple charge relay should be fine, and easy to override when you want the lithium batter to just sit. I use and SI-ACR and solar set up with my 150Ah LiFePO4 and it works beautifully. It seems to be a common misunderstanding the lithiums need high charge voltage. 13.6V will get you to 98% SOC.

unfortunately, i'm already heavily invested in the Redarc both mentally and $$$. sometimes im not sure which costs more.

 

[Terra Ops]

I too was using an SI-ACR "https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A"
but was concerned about the possibility of frying my trucks electrics when battery banks were combined. The REDARC is a one way street
from truck to coach battery and also serves as a solar controller. I'm still testing my system out, but so far it seems to be working.
Overnight voltage dropped from 13.6 to 13.2 running the fan and frig. Boiled some water on the induction and it dropped to 13.1.
Should be a sunny day, so we'll see how much juice only solar will provide.

 

[Rando]

Why would you fry the truck electronics with the SI-ACR?

The one possible draw back to the relay is that it does keep the main and aux batteries connected most of the time due to the higher resting voltage of the LiFePO4, but this is not really a major issue, and it typically true of any system with solar. They do isolate when you load up the lithium battery.

 

[CoyoteThistle]

There are at least a couple problems using an SI-ACR (and other regular battery combiners) with Li house batteries.
1) Keeping the Li connected to the starter battery/alternator when ever the vehicle is running will lead to overcharging of the Li battery. You need to be able to disconnect from the alternator when your Li is "full". See Cytrix Li-ct combiner for one way.
2) If your alternator doesn't have internal temperature sensor/current limiter it could fry itself trying to serve the Li bank. Battery combiners don't help with this.
The Redarc (in Lithium mode) seems like it will do a good job with both these challenges.

 

[Terra Ops]

There are at least a couple problems using an SI-ACR (and other regular battery combiners) with Li house batteries.
1) Keeping the Li connected to the starter battery/alternator when ever the vehicle is running will lead to overcharging of the Li battery. You need to be able to disconnect from the alternator when your Li is "full". See Cytrix Li-ct combiner for one way.
2) If your alternator doesn't have internal temperature sensor/current limiter it could fry itself trying to serve the Li bank. Battery combiners don't help with this.
The Redarc (in Lithium mode) seems like it will do a good job with both these challenges.

This is my understanding as well. Although the lithium is "branded" a drop in replacement, it has different chemistry and charging profile.
I'll bow out of this for now and post results on my build thread

 

[Rando]

There are at least a couple problems using an SI-ACR (and other regular battery combiners) with Li house batteries.
1) Keeping the Li connected to the starter battery/alternator when ever the vehicle is running will lead to overcharging of the Li battery. You need to be able to disconnect from the alternator when your Li is "full". See Cytrix Li-ct combiner for one way.
2) If your alternator doesn't have internal temperature sensor/current limiter it could fry itself trying to serve the Li bank. Battery combiners don't help with this.
The Redarc (in Lithium mode) seems like it will do a good job with both these challenges.

I haven't found either of these to be issues with my LiFePO4 set up using an SI-ACR. My alternator puts out 13.6-13.8 which is about where the lithiums want to charge to. The current tails off to about zero once the lithiums are full. I have also not had an issue with over loading the alternator - on the rare occasions when my lithium has been run down (say 50% SOC or so), I see 25 - 30A charge current. As I have solar I am usually pretty full to start with so typically see 5 - 10A, tailing off to 1-2A once full. Leaving a LiFePO4 cell on a float charger at 13.6V around the clock would be bad, but a couple hours here and there while driving won't make a big difference.

Have you experienced issues?

 

[CoyoteThistle]

That's really interesting info Rando, thanks for sharing. I think this suggests that lots of different vehicles will behave differently in charging house Li batteries. Sounds like your vehicle is really playing well with your house batteries. What vehicle is it?

For me (2010 Nissan Frontier), my "plug and play" set up would not even really charge the house battery (never more than about 5 amps at high-13 volts). I removed a certain fuse and got a constant ~14.3v with an alternator that regulated its current (got about 70 amps at start-up and then dropped to about 35 amps continuous). I have a home-brew set up to control charging, not a battery-to-battery unit like the Redarc.

Feeling like we're well in to hijack territory here Bravo , but this is a good reminder that there isn't a one-size-fits-all approach to good battery management for Li house batteries across different vehicles. I think spreading a wider understanding of the basic parameters needed for proper LiFePO4 charging would be of benefit to the larger community. Then, people could figure out what their vehicle is doing and design a cost effective system that achieves proper charging.