LiFeP04 chargers

[camperdave]

I'm trying to understand all I can before going lithium. I've got most of the issues resolved in my head, but I'm struggling a little about the charging and how it relates to house loads.

My experience with lithiums is that you charge them constant current until they reach the desired voltage (say 3.6vpc) then the charger cuts off.

How does that work in an RV? If plugged in, I don't want to be floating the lithium batteries, but I need 12v available from the charger/converter at the distribution panel for on-demand usage (water pump, lights, etc).

Do you know how Progressive Dynamics or Boondocker handle this with their Li chargers?

[BFL13]

PD info was that if it went to 14.4 by itself it would stay there until batts nearly full then drop to 13.6 or until 4 hours, whichever was shorter. They said that if you used the CW to make it go 14.4 then it stayed there 4 hours no matter what and then dropped to 13.6

The 14.4 is converter voltage not battery voltage at the other end of the wires, which would be lower by how much depending on amps flow at the time.

[camperdave]

time2roll wrote:
9130 with the wizard might well be perfect all by itself.
What is your battery charging voltage spec? Wizard s/b very close at 14.4 volts. Did you say BMS cuts at 3.65vpc or 14.6 volts? I think you are already there. Do you really need to hit the cut-off or is that borderline over charging safety limit?

You might be right, it may be close enough. 14.4 is a little higher than I'd like to see, but to be honest I don't remember ever seeing higher than 14.2 coming into my lead batteries from the PD9130 anyway. I was using 3.5vpc (14.0v) when in my car and that worked very well, some of my cells are a bit damaged and would hit high voltage sooner than others (increased internal resistance in the cells, I'd have 2-3 cells that would hit 3.6v when the pack voltage was 3.5vpc even when the cells were well balanced) but in this case I'll be picking out 8 of the best testing cells so this will hopefully not be an issue (car was a 48 cell pack in series).

The flip side is I have no idea how long the charge wizard holds the voltage at 14.4 once reaching it (absorption mode). This is fairly important for the lithiums, if it immediately drops to 13.6 then the batteries would never be fully charged. Honestly it's difficult to get specific info on charging profiles.

[camperdave]

BFL13 wrote:
Needs a special disconnect to isolate the bank. Installed one leaves the LP alarm and radio connected. Also jacks and slides but just don't use those at the time if you can move the LP alarm and radio to the other side of the disconnect and then be able to use the installed one.

Entry step is direct wired too. I'm thinking those direct loads are low enough draws to not worry about, or items that will not be used while plugged in/charging. I would have to move the LP alarm over, but it's installed close to the 12v distribution panel so that would be easy.

I'm feeling closer to going for it. Based on measurements (but I have not yet physically tried it), I think I can drop in 8 cells where the current dual GC2s are which would give me 260ah @ 12v (~200ah usable, or double what I have now) with minimal wiring changes to the motorhome.

[2oldman]

camperdave wrote:

2oldman wrote:
What does another charger in parallel do?

My thinking is that it would let me use a charger with the correct charge profile and also keep the existing converter for 12v loads after the li charger cuts off.

Chargers in parallel with different characteristics are not likely to work well. I'd just be charging the Li's and when that shuts off the battery takes over the loads until it needs charging again.

[BFL13]

Needs a special disconnect to isolate the bank. Installed one leaves the LP alarm and radio connected. Also jacks and slides but just don't use those at the time if you can move the LP alarm and radio to the other side of the disconnect and then be able to use the installed one.

[camperdave]

2oldman wrote:
What does another charger in parallel do?

My thinking is that it would let me use a charger with the correct charge profile and also keep the existing converter for 12v loads after the li charger cuts off.

On more thought though, and based on what Gordonthree is saying above, I think I've come to a good solution. Keep the pd9130 wired to the load center as is, and add a new li charger at the battery pack for the pack charging. When plugged in, I believe all I'll need to do is disconnect the battery pack via the 'dealer disconnect switch' and I'll be able to cleanly charge the pack with no loads, and still supply 12v to the motorhome via the pd9130.

Seems perfect, no?

[GordonThree]

Google the following

Lithium ion parasitic load micro cycling

In a sense, powering a load with the battery charger will cause the pack suffer small cycles, say alternatively between 99 and 100%

If you're camping mostly with hookups, a situation where floating is going to be most of the time, then a battery isolation system is the best bet for the long term health of the cells. Once charged, disconnect the battery until shore power is lost. This is easily automated.

If you're mostly on solar, so seeing 5-8 hrs of charging a day, then isolation wouldn't be a big consideration.

Biggest benefit of lithium is you don't have to chase 100% soc constantly like lead acid. In fact 100% soc is rather bad for cells in the long term.

[time2roll]

9130 with the wizard might well be perfect all by itself.
What is your battery charging voltage spec? Wizard s/b very close at 14.4 volts. Did you say BMS cuts at 3.65vpc or 14.6 volts? I think you are already there. Do you really need to hit the cut-off or is that borderline over charging safety limit?

[2oldman]

camperdave wrote:
I'm thinking now maybe I keep the PD9130 (without the charge wizard attached), and add a separate charger in parallel for charging the lithiums. Could it be that simple?

What does another charger in parallel do?

[camperdave]

ok, lots of good info here. I'm especially interested in the 13.6v float (3.4vpc) since that's what my PD9130 that's in there already puts out constantly if I remove the charge wizard pendant.

I'm thinking now maybe I keep the PD9130 (without the charge wizard attached), and add a separate charger in parallel for charging the lithiums. Could it be that simple?

Full disclosure, I already have the 130ah cells, they were pulled out of my old electric car before it got towed to the junkyard. I will be using these batteries (they are a bit hammered after 20k miles of 500+amp hits, but still show decent capacity). I also have a Manzanita Micro PFC30 charger that I'm thinking I may be able to use as well, just in parallel with my existing PD9130 converter. I previously didn't think there would be a way to use the MM charger since it simply shuts off when charged (no ability to use as a converter for house loads when plugged in, and no ability to auto-restart).

[Lwiddis]

Won’t the battery seller install all you need and set it up properly?

[time2roll]

camperdave wrote:

2oldman wrote:

camperdave wrote:
I don't want to be floating the lithium batteries,

I'm not sure what your concern is. My Li pack allows float. Yours don't?

ok, maybe that's the part I need to look into more. I'm going to be using prismatic CALB 130ah cells, I was under the impression they should not be floated.

Unless stated by the battery maker... any float significantly below the charging voltage is fine. In effect the converter will supply no power until the battery is discharged to that level. Remaining at partial charge is not an issue for lithium as we are so used to with lead-acid.

Or having the converter shut down at full charge is not an issue either. The battery will supply power just fine to run all things 12 volts. The real question is when does the converter kick back on to recharge and does it do this automatically.

[Itinerant1]

Sorry, typed as you posted. Even better going with prismatic cells but same thing.

I'm 32 months on GBS prismatic cells (20 cells) 4s5p which have been in continuous duty 14.1v bulk, 14.2v absorb (10 min), 13.6v float since day 1. There are more than 330 cycles so far with no issues.

[2oldman]

camperdave wrote:
I'm going to be using prismatic CALB 130ah cells,.

Then you're responsible for the BMS too.

The info I found says your acid charger won't work properly, and you should disconnect after charging. I sent a couple chargers (not converters) back to the factory to have their voltages changed to charge my 48v 100ah pack. Free except for shipping.

I know you're trying to save a few bucks, but I'd consider a drop-in like a Battleborn or eq. Might be better in the long run.