2108DS Lithium install: the trip report

[tinglett]

Originally Posted by al1florida

Knowledge is important when things don't work well, or as well as expected.

Exactly! It isn't a horrible thing I'm having trouble with one of my batteries. I figure when all is said and done, I'll understand a lot more, and hopefully may get out of a jam if I happen to run a battery all the way down. Of course I'm speaking with confidence (hopefully not naively) that if there is a mfg issue, BB will correct it.

I left the battery on the TT's charger and it charged with a fraction of an amp, and after an hour it was down to zero amps (at 14.55v). I decided to pull the battery and put it on a bench digital power supply and see how that goes. See attached photo. It's pretty much doing the same thing. It was at 0.10A and is drifting down. I'll be calling BB again tomorrow.

[Old Navy]

I'm not sure what voltage is required to get the Battle Born out of "safe mode", but it might be a little higher than 14.6. I would be concerned with how the battery ended up in safe mode, and why it would be so difficult to "wake it up". Hopefully Battle Born will be helpful.

[tinglett]

Yeah, hopefully they will be more helpful. The benchtop power supply isn't working either. It slowly drifted down to 10ma and I imagine it'll go down further. The Victron BMV probably rounds this down to zero.

I do wonder how the battery got this way. I have a hunch it's been in this state since I got it, which has only been a few weeks with two outings. I didn't think to check the battery voltages as they said they shipped fully charged. They've always been tied in parallel with a Y cable configuration so I don't see how one can drain flat while the other is perfectly charged.

So one lesson is when you are assembling a battery bank from new batteries, you should do some simple testing on each battery and perhaps even run on that battery exclusively a bit to ensure it's working as expected. I was too eager to get both of these working together.

On the plus side, I was effectively running with a single battery, managed to run it flat, and it stayed alive with no issues at all. That's a good thing. I'm hoping once this other battery is resuscitated, it'll behave in this good way from there on.

[creativepart]

In a comment below that thread from another website I linked to about waking up a LiPo battery in protect mode one person said they gave the battery a momentary 40v jolt and that worked. I’m not saying that’s OK to do, but maybe ask BB?

[tinglett]

Well, they are starting the RMA process. I forgot to ask about a spike in voltage. He just went "hmm" when I said it's resting at 14.05v, but when I put a little 0.3A load on it it drops below 7v. He floated a theory that a cell may have gone dead after the first use, but I bet these batteries are a bit more redundant than that. The box it came in and the battery's case are in fine condition so I don't think it was jostled around in shipping. But who knows. Lucky me.

Meanwhile, I'm drawing down the SOC on the other battery and it's behaving well. I'll charge it back up this evening and make sure the time that takes is consistent with what the Victron BMV is telling me.

[tinglett]

The "bad" battery is on its way back to the factory. Meanwhile I drained down the "good" battery as a test by running both MaxxAir fans on high. I was particularly interested in how voltage behaved as it ran down. I ran it down to 12% as I thought this was enough (note I did update the Victron BMV battery setting to reflect that I have a single battery).

The starting voltage at 100% SOC was 13.25v which Battleborn said is exactly what they'd expect. When I turned the fans on the voltage dropped to 13.20v and held steady until it got close to -30Ah. From there on it seemed to be drifting slowly down and as you can see it got to 12.73v. Plenty high. When I turned off the fans the voltage went back up to 12.80v. You can see that the fans were pulling a bit more than 5A the whole time. I probably should have measured the total runtime, but I had to do this over a long period of time and I didn't want to leave it running too long (i.e. overnight) without me paying attention. I didn't want to hit 0% SOC!

The final screenshot shows it back on the charger again. Note that it's pulling 41A. At 50% SOC it was drawing 35A @ 13.62v, and at 99% SOC it was 1A @ 14.52v. It took about 2.75hr to fill 88Ah so I guess it averaged about 32A.


Oh, and I learned that my PD4655LIV charger is hard-wired to deliver 14.55v. It doesn't go through other charge stages. I guess that's why it has a big warning to not use it on other battery types. Hmm...so if this is true, is the voltage drop (13.30v) simply due to the high current through my 6 AWG wire? I'd estimate a 15-20ft wire distance from charger to battery. Perhaps the charger still has some "smarts" about voltage to apply, though, that I simply don't understand.

[tinglett]

I think I can answer my own question! In my last post I observed the battery monitor showed 13.30v at the battery while being delivered 41.19A. I had learned that my charger model is specifically hard-wired to produce 14.55 volts for LiFePO4 batteries. So is the voltage drop a "smart" feature of the charger, or is it simply the drop over 6 AWG wire? It's the wire. Check the attached voltage drop calculation from the calculator at https://www.calculator.net/voltage-drop-calculator.html I had to experiment with the overall cable distance as I don't know it precisely, but 38 feet (19ft for +, and 19ft for -) seems pretty much in the ballpark. Hopefully I used the calculator right as that footnote is confusing to me.

So without another mod, I don't think I'm going to see many more charging amps out of this setup. I believe several folks in this thread were already observing this, but it finally sank into my head

[al1florida]

The voltage drop calculator you used is one that I like to use as well.

Note that the calculator specifies that you input the one way distance. This means it automatically calculates the round trip voltage loss. So the length you entered should be 19'.

You could have longer wire that you think, or the return path could be the frame of the trailer and the connections to the frame are not the best conductor of electric.

[al1florida]

If the charger is still putting out 14.55V when the batteries are fully charged, I would check with Battle Born to see if that is OK with them.

In general LiFePO4 is not happy with staying at 100% charged and constant voltage of 14.5V

These batteries prefer to be at 90-95% SOC or lower.

[tinglett]

Originally Posted by al1florida

In general LiFePO4 is not happy with staying at 100% charged and constant voltage of 14.5V. These batteries prefer to be at 90-95% SOC or lower.

I'll ask BB about this. Perhaps the PD4655LIV does this, but I can't say I've observed it. When it hits 100% SOC it stays there at 14.5V. What I really don't understand is why the internal BMS of the battery can't do this kind of thing.

It would be nice if the Victron BMV could be programmed to turn on/off the charger connection as needed to maintain 90% SOC -- provided the charger has shore power, of course. I've noticed that the Victron BMV has a relay control that perhaps could be programmed to drive a relay to drive a contactor of some kind considering the amps involved. I wonder if anyone has done this before.

I don't believe this is a big problem I need to solve, though, because I suspect we'll continue to dry camp and I'll probably charge the battery when we get home, turn everything off, and unplug from shore power until we head out again. The batteries will probably stay happy and healthy. Right now I'm mainly just playing with the new toys and learning how they work.

[tinglett]

I called BB this morning and asked questions about my PD4655LIV charger. I posted an update over on that charger thread, but the gist is that it indeed does always run in "boost" mode.

I also asked about overcharging and over-draining the battery and got a sigh. He insisted these are non-issues with their battery's BMS. He did, however, suggest that if the rig is in storage for a month or more he would recommend disconnecting from the charger. So there's a little waffling there, but he did say there was no reason to maintain less than 100% SOC for their brand of battery. He was clear he was not speaking for other brands.

As for discharging he said it was fine to run the batteries down until they shut off. The BMS leaves plenty of charge behind, BUT he highly recommended getting them charged up again soon after as they can't sit in this state for too long.

I think I'll still disconnect the battery (with the switch) if I'm on shore power for extended times (multiple days) and won't intentionally hit 0% SOC. But it's nice to know that BB, at least, doesn't think this is a problem and hopefully won't call such events "abuse" of any kind should they happen.

[al1florida]

Originally Posted by tinglett

I called BB this morning and asked questions about my PD4655LIV charger. I posted an update over on that charger thread, but the gist is that it indeed does always run in "boost" mode.

I also asked about overcharging and over-draining the battery and got a sigh. He insisted these are non-issues with their battery's BMS. He did, however, suggest that if the rig is in storage for a month or more he would recommend disconnecting from the charger. So there's a little waffling there, but he did say there was no reason to maintain less than 100% SOC for their brand of battery. He was clear he was not speaking for other brands.

As for discharging he said it was fine to run the batteries down until they shut off. The BMS leaves plenty of charge behind, BUT he highly recommended getting them charged up again soon after as they can't sit in this state for too long.

I think I'll still disconnect the battery (with the switch) if I'm on shore power for extended times (multiple days) and won't intentionally hit 0% SOC. But it's nice to know that BB, at least, doesn't think this is a problem and hopefully won't call such events "abuse" of any kind should they happen.

I have not run across a website that recommended leaving the LiFePO4 batteries at 100% or using them until the BMS shuts them off.

One thing that comes to mind: The recommendation from the support desk is not in writing as an official statement from Battle Born so if the batteries don't perform up to specs at the end of a year or two, a person only has the "he said xxxx" and the company can say, well he was mistaken IF he said that.

Personally I would do as you are planning, not keeping a continuous 100% charge and not running them down until the BMS cuts them off.

[tinglett]

Originally Posted by tinglett

The "bad" battery is on its way back to the factory.

Just as a follow-up, the replacement battery finally arrived today. It was a bit disappointing it went into a bit of a black hole and was difficult to get BB to respond, but I'll give them a break for covid. I know they are working hard.

The only info I got was "the BMS was bad." The lady I talked to seemed a bit surprised when she asked how long I had the battery and learned it was new. She said she'd follow up to try to get an explanation, but I doubt I'll hear more. The battery looks new, but she said it was repaired and would be shipped "as soon as the glue is dry." So I hope it's good. Clearly the case had been replaced as I know I had scuffed it up a bit.

I measured the battery and it's sitting at 13.35v as expected. It's cold outside, but on a warm (above freezing) day I'll take it out, run it down a bit, and then top it back off just to make sure all is well. Then it needs to come inside for the winter.

[Elkman]

All the lithium phosate batteries I checked out included a battery isolation manager or BIM built into the battery. A surge could damage this device very easily. For my lithium phosate batteries I added the Precision Circuits Li-BIM 225 that is sold by Battle Born Batteries and other vendors. It is designed for use with lithium phostate coach batteries.

From the Amazon listing:

• Under normal charging conditions, the BIM will connect for 15 minutes every 35 minutes. That means that the BIM will connect for 15 minutes, disconnect for 20 minutes, and repeat this cycle until the coach battery is charged.
• If the coach battery resting voltage exceeds 13.4V than the BIM will disconnect. A resting voltage greater than 13.4V indicates a fully charged battery. Note that “resting voltage” means that no current is flowing to the coach battery. The BIM will disconnect if the alternator voltage exceeds 14.4V. This protects the coach battery from over charging.
• The BIM will disconnect if the voltage difference between the alternator and the coach battery is less than 0.1V. If the voltage difference is too low, then there is a negligible charging current, and no need to connect to the coach battery.
• The BIM will disconnect if the alternator voltage drops below 13.3V. If the alternator voltage is too low, than it cannot adequately charge the coach battery, so there is no reason to connect.

[al1florida]

Originally Posted by Elkman

All the lithium phosate batteries I checked out included a battery isolation manager or BIM built into the battery. A surge could damage this device very easily. For my lithium phosate batteries I added the Precision Circuits Li-BIM 225 that is sold by Battle Born Batteries and other vendors. It is designed for use with lithium phostate coach batteries.

I believe the thing that comes with lithium batteries is a "BMS", (Battery Management System) that is built into the battery. This protects the battery from over charging or over discharging. As to what kind of surge it would take to damage the BMS I would think that what would damage the BMS would also damage most of whatever other 12V devices you have such as lights, 12V control boards for the fridge, etc.

[thataway4]

The Precision Circuits Li-BIM 225 is for the vehicle charging circuit, and avoids stress on the alternator. It does also isolates the LiFePO4 battery from the vehicle starting battery and avoids a "dump" or surge into that start battery. Not at all the same function as the BMS as above.

It would not protect from a lightning induced surge for example.

[tinglett]

BTW, my battery did check out fine. I ran it down to ~66% SOC and charged it back up. Behaved good, so I pulled it out and put it indoors in storage for the winter.

I haven't looked into a DC-DC isolation circuit to protect my alternator. So far the max I've measured when powering off the tow vehicle is 17.88A, but it dribbled down to 6A pretty quick. I suspect this is a combination of the wire gauge from the alternator all the way back through the 7-pin connector into the trailer, along with the fact that the alternator sense circuit is assuming a standard FLA battery of some kind. So I doubt if I'm ever going to hurt the alternator unless I somehow improve the situation (if that's the right word ).

I have found that my 12v power pin on my trailer connector has a relay so it's only connected when the vehicle is running, and it has a 40A fuse. That's a much higher rated fuse that I was expecting to find. I'm not sure if continuous 40A draw would hurt the alternator or not. I suppose it might.

[al1florida]

Originally Posted by tinglett

BTW, my battery did check out fine. I ran it down to ~66% SOC and charged it back up. Behaved good, so I pulled it out and put it indoors in storage for the winter.

I haven't looked into a DC-DC isolation circuit to protect my alternator. So far the max I've measured when powering off the tow vehicle is 17.88A, but it dribbled down to 6A pretty quick. I suspect this is a combination of the wire gauge from the alternator all the way back through the 7-pin connector into the trailer, along with the fact that the alternator sense circuit is assuming a standard FLA battery of some kind. So I doubt if I'm ever going to hurt the alternator unless I somehow improve the situation (if that's the right word ).

I have found that my 12v power pin on my trailer connector has a relay so it's only connected when the vehicle is running, and it has a 40A fuse. That's a much higher rated fuse that I was expecting to find. I'm not sure if continuous 40A draw would hurt the alternator or not. I suppose it might.

If you are lucky you have 10 gauge wire for the 12V (and ground) in the 7 pin connector, but it could be #12 or even #14 wire.

Either way you are not going to get much current (as your numbers already show) down the long wire run from the alternator to the trailer battery.

In the spring when you go out in the trailer again, be sure to check the amps after you have pulled the battery down to 40% or 50% SOC.

[Old Navy]

Remember those numbers you saw were from a single battery. You should see higher numbers once you hook the two batteries in parallel.

[tinglett]

Originally Posted by Old Navy

Remember those numbers you saw were from a single battery. You should see higher numbers once you hook the two batteries in parallel.

Good point! As far as I know, the 2nd battery never was pulling a charge all along. So it's possible I could hit 2x, but I have no idea how heavy duty the wires are in the SUV short of doing a bit of digging. Too cold for that right now. But I'll need to do an experiment in the spring and watch for trouble.