Seeking input: LiFePO4 charging

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ntsqd

ntsqd

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The system is an existing Victron solar charge controller and ~200W worth of solar panels. Panels pre-exist our ownership, so not sure what they are other than larger physically than the 100W panel that I installed on our first camper. Exactly which Victron I installed 3 years ago I need to look into. Batteries were two GC2 AGM's in series, so quite certain that the Victron was set up for them and will need to have it's parameters changed. The AGMs are now dead, Jim. No red tunics even!

I used to float the batteries with a NOCO 120VAC charger while the camper was parked. Pretty sure that's not a good idea with the LiFePO4's. Got to thinking that with the Victron set correctly for them that I could simply use a power supply to feed it power like if the solar panels were working. Something like this power supply (or similar so that I'm not exceeding the Victron's input amp limit).
Is this a viable solution?
 
The victron would need to handle 30 amps for the 200w of solar. From what I recall if it has ability to set parameters it is 30 amp or above, meaning I dont think the lower amp ones have the adjustable setting , just a batt type selection maybe. I agree that feeding the BMS of the Lipo batt with correct wave is important mfor batt life, don't just rely on the BMS, IMO.
 
Notwithstanding the issue of an MPPT seeing a fixed voltage, I don't think that this would work with that specific power supply or something close to it. IIRC, the Victrons typically need to have the MPPT input voltage sensor see something like 5V above the battery voltage. With less, it would not even start to do its thing, probably. And that supply looks like it'd be stuck at close to 12V, so not enough. A 24V or adjustable voltage giving 19V or more supply might work, but probably not great given the MPPT issues. And if you have a variable voltage supply, you could instead just set it to 14.6V, not have the Victron at all, and call it a day. But why is it you can't use the panels for maintaining the batteries?

My smallest Victron is a 75/15 and it is fully adjustable for all sorts of parameters.
 
If I were you I would get a new noco that supports LiFePo4. Way cleaner.

I'd also consider running your two panels together in series - lower amps to the Victron, simpler wiring (likely no panel fusing required), more efficient charging and resilience to cloudy days, etc.

I run 3 100w panels in series at ~54v to a Victron 75/15.
 
Where the camper is parked between trips is heavily shaded all day by a ginormous California Oak on the neighbor's lot. It is about 5' in diameter at the main part of the trunk, and being an oak tree in KA means even just trimming it is a gumbermental pain. Which is why a trickler is required.

My goal with this vehicle is for it to NOT be a project, it doesn't need to be the latest, greatest trickest set-up. It just needs to work. I have other vehicles that are projects (see sig file). The simpler, the better for this truck and the power supply feeding the controller seemed like the simplest but I was unaware of any NOCO's having a Li setting so I'll investigate that.
 
For LiFeP "12V" batteries, I've seen it mentioned to either cut off completely the charging after the current has gone down to the tail value while at 14.5V or so, or alternatively to decrease the voltage to around 13.5V which is basically also saying there won't be any more charging. Unfortunately, I have seen dedicated LFP chargers that don't have either the reduced voltage or cut-off feature, and you probably don't want to keep at it at 14.5V for very long periods. So, maybe worth checking the specs of the chargers you are looking at for that?
If you have something like 200W of panels, a good controller, and not much parasitic draw, is it possible that you would get enough power even with shade to keep the battery up? My panels typically give a few Watts even in fully overcast conditions or with discrete shading, that may be enough.
In fact, if there is no parasitic draw, your LiFeP battery likely won't go bad or self-discharge if left to sit without charging for a long time, unlike a lead acid battery, so is trickle maintenance even needed then?
 
I do this with my victron smart solar charge controllers, with a 54v 2kw power supply feeding the solar input on the charge controller. The controller needs ~5v head room above the charge voltage and will self limit current on its own to what ever is set in the parameter.

As long as you don't exceed the I out voltage on the charge controller you should be fine.

I do this or use my noco charger whichever is closer and easier, typically the power supply as it is just a little easier/quicker to hook up. And also higher charge rate than the noco.
 
Ultimately whatever the solution is, it will be a permanent install. At least for this set of batteries. I will be adding a dedicated 120VAC outlet for the charger/power supply so that when I plug in the camper it works w/o further input from me.

All of this setting of charging parameters or at least knowing what they are is what put me on the path of just routing all charging thru the solar controller. I figured then there's only one set of parameters that need setting or being aware of.

I wonder if the power supply will be unhappy about the solar panel's output while on a trip if I simply wire them in parallel at the input to the solar controller. I know that it won't work in reverse, but I do worry that something in the inverter might get hot. Everything that I've read says that the panels won't care about the power supply when it is operating. I suppose that I could use a couple 'sugar cube' relays in parallel to set up an automatic change-over function when the power supply is turned on.

I had hoped that the solar would keep the batteries up, but experience has proven that to not work. Unfortunately the other parking spots are periodically in the way, which results in much vehicle shuffling and the tree is big enough that shading will still happen for roughly half a day at the least.
 
You really don't have any settings or parameters to worry about when adding a second dedicated charger like a noco. It would be plug and play. Pull out the AC cord, plug it in, and walk away. This is far and away the cleanest way to do this electrically speaking.

If you decide to go down the power supply masquerading as a solar panel route, you'll want to match the voltage on your panel array (probably 18-20v if in parallel, 36-40v if in series, but do look at your panel specs to be sure) and understand how your power supply handles / regulates amperage.

A Victron 75/15 for example is rated for 220w of solar panel input power. You can go over that a bit but you wouldn't want to have your power supply melting the solar controller or tripping its own circuit protection. You also would want to avoid having the power supply in parallel with the panels, because then you'd have to do some unusual fusing and probably include a diode as well.

I have a Victron and a Noco wired to my house battery and it is as simple as can be.
 
What kind of algorithm do these NOCO LFP chargers use?
 
It was admittedly a quick look, but I didn't find any of that sort of info on the NOCO page. This was all that I found: NOCO - 10-Amp Smart Battery Charger - GENIUS10 - https://no.co/genius10/specs

There seems to be this idea floating around that a BMS manages the charging and that all that is needed is a constant voltage charging source. From my limited reading on the topic (so far only this morning) that is not the case. The BMS does a lot of protection functions, but it doesn't manage the actual charging profile. In a way it would be handy if it did.

I did manage to glance at some of the paperwork that came with these batteries this morning. I think Bulk voltage was 14.4VDC, but I don't recall what Adsorption voltage was. It only had those two steps and voltages listed., no float.
 
e9999 said:
What kind of algorithm do these NOCO LFP chargers use?
Click to expand...

I honestly don't know and I mentioned Noco really because of their reputation. I have one for my AGM house battery and if I were running Lithium onboard I would start my research there.

I use a charger from PowerWerx to charge the small 10Ah Lithium battery on one of my projects.

There seems to be this idea floating around that a BMS manages the charging and that all that is needed is a constant voltage charging source.
Click to expand...
I've never heard of a lithium battery with a built-iin charge function. I would expect to need a charger with the right profile and capacity for your battery chemistry and size.
 
I'd never heard of that either, and no one has outright said that, but I have seen it said that the BMS supervises the battery and the context implied that they thought it controlled the charging.
 
Coming back around to this, my existing NOCO does have a Li setting and I was able to bring both up to full charge individually before connecting them together. I was careful to make the jumpers exactly the same length, and I've used the diagonal connection scheme (pos on one battery, neg on the other).

I use that charger for other vehicles, so I'll need to buy one for the camper. At 10A I feel that it is a bit large for regular use in the camper. Am thinking more like a 2A-5A charger for permanent mounting in the camper.

I did adjust the Victron charge controller for these batteries, but that was a month ago and I don't recall what the exact settings were, just that it won't try to float the batteries any more.
 
my (superficial) understanding of LiFeP batteries' BMSes is that they ensure cell balancing, and limit charging current during the charging process (for excess current and overly low or high temps). I have never heard of them controlling charging voltage profiles. That would require significantly more hardware than just the former, I would think. So, if that is right, yes, they do control charging -sort of- but not like an external charger would, where the voltage will change with time.

(FWIW, I don't think you want/need to "float" LiFeP batteries like you do lead acid ones, with some excess voltage.)
 
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