[RE-wrenches] Switching to LiFePO4

Wed Sep 18 06:39:19 PDT 2024

There is a large misunderstanding about lithium battery LVD voltages vs type.

Simpliphi for example has a very high LVD at between 24-25v depending on DOD you want.  
And thats true, the VFX/FX you can’t set the LBCO that high so you have to get creative. 

Vs most of the better prismatic cells, at around 20-21v LVD ( which is all I use)
Which every legacy inverter I know of has a higher LBCO set point than that.

Jay

> On Sep 18, 2024, at 7:22 AM, Mac Lewis via RE-wrenches <re-wrenches at lists.re-wrenches.org> wrote:
> 
> Hi David,
> 
> This upgrade comes up a lot.  You are at a point where you have to decide; do I match my old equipment with a new 24V Lithium battery bank (thus limiting my battery bank options), or do I upgrade my equipment to 48V which opens up the brands available?
> 
> I have had good success matching older equipment with new batteries but my preference is always to try to get these systems to 48V if it's financially viable.  Ray describes a solution to get the LBCO high enough to shut off the inverter before the BMS shuts down and this works.  You can also hardwire a power supply to wake up the BMS directly from the generator.
> 
> Remote monitoring is very useful too, especially in a rental scenario like this.  It may be time for a full upgrade.
> 
> Very hard to know which companies will make it through...
> 
> 
> 
> On Tue, Sep 17, 2024 at 4:01 PM Jason Szumlanski via RE-wrenches <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at lists.re-wrenches.org>> wrote:
> I don’t want to stray too far off track, but it’s worth discussing how challenging it is to predict which manufacturers will be around in a few years.
> 
> I know this might be a touchy subject, but Enphase is beginning to offer full off-grid support. While I’m fully aware of the drawbacks of their system architecture for off-grid setups, it’s also important to acknowledge that no manufacturer is “too big to fail”—but Enphase is about as close as we have right now. If something were to happen to them, the reliance on remote access for the system functioning is concerning. It could essentially become a big brick if a service issue arises and there’s no support. On the other hand, Enphase may be a safe bet for certain off-grid systems if you think they will come out on top. 
> 
> But the reason I bring Enphase up is modularity. Building systems with interconnected components from various brands can spread the risk. Sol-Ark, with its “battery agnostic” approach, is a reasonable choice, as long as there’s a replacement all-in-one option if they were to go out of business. EG4 and Midnite seem to offer alternatives in that space now. As long as LiFePO manufacturers stick with 48V/51.2V standards, complete battery replacements should be straightforward. However, I do think that large battery sizes like 5 kWh (or even 13.5 and 14.3 kWh) could be problematic. Personally, I prefer the concept of smaller, 1 kWh chunks. In the case of a 40 kWh battery bank, for example, if one module fails and the manufacturer is no longer around, it’s a lot easier to deal with. That's similar to how we can drop one faulty 2V cell in a series of 24 lead acid batteries sometimes. Enphase, if you think about it, is the least modular approach in some ways, since it relies on a single manufacturer with a proprietary system. So the whole concept of modularity is not straightforward, either. It's a fantasy at this point to hope for a truly modular and manufacturer-agnostic system.
> 
> What I find interesting is that most of my clients who went off-grid 7-15 years ago are pretty understanding when I tell them it’s time to replace their systems. Realistically, fast-forward another decade, and we’ll probably see significant advances that make a complete system replacement worth it once again. I’m not saying we should be designing disposable systems, but that might be where we’re headed, just like so many other industries. Think of what Tesla is doing with the Powewall 3. They are making solar and batteries as cheap as possible (while maintaining high quality standards and keeping fuel in Elon's jet). However, when the PW4 comes out, the PW3 will be deprecated, and those systems will become essentially disposable. The warranty is only 10 years. So when the inverter insude the PW3 dies in year 11, guess what – the entire PW3, battery and all, may be rendered useless. But, people still flock to Tesla for backup systems. And for good reasons. 
> 
> The days of keeping systems running on old components while upgrading just parts of the system are probably behind us. The rapid evolution of technology, equipment, codes, safety, and consumer needs will make whatever we install today obsolete soon after it's up and running. 
> 
> 
> 
> --end rant--
> 
> 
> Jason Szumlanski
> Principal Solar Designer | Florida Solar Design Group
> NABCEP Certified Solar Professional (PVIP)
> Florida State Certified Solar Contractor CVC56956
> Florida Certified Electrical Contractor EC13013208
> 
> 
> On Tue, Sep 17, 2024 at 5:20 PM Ray Walters via RE-wrenches <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at lists.re-wrenches.org>> wrote:
> Honestly, that advice would seem to  be true, but the reality is: It is 
> not valid.  Just look at Blue Planet, that was supposed to be a top tier 
> offering.  Solar World?  AEE? Magnum has had serious issues, Outback 
> doesn't answer the phone, SImpliphi takes an attorney to honor their 
> warranty. Even long standing companies are not sure bets, at all.  They 
> do cost much more, so I'm not sure who to turn to anymore.  I'm about to 
> install Rubix LiPO4, which comes in a 24 v offering, BTW for Dave.
> 
> The biggest issue I've seen with old VFX inverters, is the LVD set point 
> can't go high enough for LiPO4.  I use the aux out on a charge 
> controller, to switch on and off the remote switch on the VFX.
> 
> I like the Fortress with Solark combo, but its not without its troubles 
> either.  If the Solark shuts off due to low voltage, so does your PV 
> input.  Then the no load draw on the Fortress eventually shuts down the 
> battery.  You really need some (at least 1 kW) of DC coupled PV to keep 
> that death spiral from happening.
> 
> Ray Walters
> Remote Solar
> 
> On 9/17/2024 12:23 PM, Sindelar Solar via RE-wrenches wrote:
> > Jerry,
> > Re your advice to never get startups or small manufacturers as so many 
> > disappear and now you are stuck, I guess we should stick with the big 
> > well-established manufacturers, like Outback, Magnum and Blue Planet, 
> > right?
> > As you would say, fun times...
> > Allan
> >
> > On 9/17/2024 10:58 AM, Jerry Shafer via RE-wrenches wrote:
> >> Dave,
> >> I would suggest stepping up to 48 nominal, fortress 18.5, battery 12 
> >> or 15 k solark inverter, re-wire the array to single or dual string, 
> >> make the wiring in the home capable of 240, this usually requires 
> >> main panel re-work and set up the monitoring.
> >> Batteries are like replacement heart valves, never get startups or 
> >> small manufacturers as so many disappear and now you are stuck.
> >> Fun times.
> >
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> -- 
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> 
> 
> Mac Lewis
> 
> "Yo solo sé que no sé nada." -Sócrates
> 
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