Nissan leaf 16v battery floating and inverting questions - Page 1
Forum section: electronics / general

author: badjob
author_rank: Contributor
timestamp: July 20, 2019, 11:26:38 am
content: So I got 2 leaf modules to replace my lead acid in the solar setup and they are phenomenal. Unfortunately, I've now run into the issue that most good inverter manufacturers cut off at under 16V.Anyone know of a pure sine wave that will run at up to 16.4v?I have a cheap inverter that doesn't seem to cut off but it's modified sine wave. Only 500w which is right where I like it. Yesterday I blew some caps on it but that was an easy fix. Still chooching along but it makes some power supplies whine.If such a thing doesn't exist, what are my other options? Can I modify the over voltage cutoff easily? Some kind of step down?The second question relates to charging. I asked all the solar guys but they weren't the nicest. I use an EPever MPPT that doesn't turn off float. I'm only charging the battery to 16.2v which is 4.05v per cell (80%). Some information says to float at 4.0V, some says to float way below where you are charged. Will Prowse, the youtube solar guy says to float at .1 below where you charge and then go back to boost at .3 below that. Nobody has an answer backed by any science.When I charged the thing up and used 3.9v per cell, all charging stopped (good) but then my loads were taken up by the battery instead of the panels. 4.0 was slightly better but I saw some .5 amps tickling the battery for a while longer which I'd rather not have and it still took a while to start using the solar instead of the battery. I might try the prowse suggestion today.If the floating isn't going to overcharge my battery, will it have any other negative effects? After all this thing will take 65A+ in both directions. Can such tiny currents .5A at most degrade it?

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 20, 2019, 04:46:52 pm
content: Could the MPPT be programmed to just hold the voltage at 4V/cell? Standard lithium charges to 4.2V/cell and settles back to about 4.15V/cell so a constant 4.1V/cell is OK. Nissan Leaf batteries are LiMn which charge to 4.1V/cell, so 4V/cell should similarly be OK. Maybe stick to 3.9V/cell to be conservative.Have you considered hacking your cheap inverter to increase the duty cycle, then adding a LC filter on the output? Or go straight to DC. That boosts efficiency when using it to operate electronics. You can also connect the HVDC to a VFD and then get fancy V/Hz control for motor loads, at a fraction of the price of ready made solutions.

author: badjob
author_rank: Contributor
timestamp: July 20, 2019, 07:54:13 pm
content: I thought the leaf batteries went to 4.2v per cell just like other lithium. Everywhere says that is their max but I have never seen a datasheet in the wild. Like 4.16 was 99%. You might know better than me though. Anyways, with this profile I am hitting 4.04 per cell max, my solar puts out 7A at best. Perhaps I will back it off all by .1V? Want to be in the 80-85% range, not fully charged.I'm all open to modifying the inverter and have a bunch of scraps lying around. I'll start searching to see if anyone has done something similar, too lacking knowledge to come up with it on my own.This is what I have:https://www.amazon.com/Boost-Truck-Automotive-Power-Inverter/dp/B0051PULH6As for DC/DC stuff I use buck and boost converters for whatever I can, some stuff is not really adaptable. The most useful part of this system is charging my radios and 18650s right now and that's all DC/DC.Must say though, these batteries rock. They ran my corded drill and didn't lose much charge at all. Compared to lead acid was definitely worth it if they don't degrade. Thinking of doubling up on capacity even.This and the seller is where I got 4.2 from :https://www.summet.com/blog/2015/10/31/how-to-build-a-16-volt-battery-module-from-six-nissan-leaf-cells/

author: john61ct
author_rank: Regular Contributor
timestamp: July 20, 2019, 11:09:34 pm
content: LiNiCoAlO2 (NCA) or (more likely IMO) LiNiMnCoO2 (NMC) was the Leaf chemistry for 2014 and earlier, depends on who you believeApparently Lithium-Manganese, LiMn2O4 aka LMO (IMR?) afterwards.afaic 4.2V is the "danger do not exceed" maximum for charging voltage.Stopping anywhere near 4.1V, say 4.11V, is very very close to full capacity, much safer (boom bad!) and more conducive to longevity. As is charging at a low rate, say 0.2-3CI recommend using a current-limiting charger with adjustable voltage setpoints and ideally allowing for a CC-Only stop-charge, or at least one where holding the Absorb/CV stage can be reduced to a pretty short mimimum.Ideally allowing Float to be set to None, otherwise maybe set to 3.6V or so to carry concurrent loads, should be well below resting voltage after fully charged.

author: badjob
author_rank: Contributor
timestamp: July 21, 2019, 12:39:25 am
content: So then I'm doing good but maybe closer to 90 than 80%. The absorb is supposed to be 10 minutes only, the lowest. In practice I think it runs longer. But this isn't a plug-in charger, its a solar charge controller. I only have the options I have. Ones with all of these abilities will cost more than the batteries.I'll take another vote for float far below charging voltage. I kind of did this previously, but then the controller draws from the battery only and ignores the solar until the voltage drops to that level. I am in luck though, because I can't even reach .2c.

author: john61ct
author_rank: Regular Contributor
timestamp: July 21, 2019, 01:27:31 am
content: Remember, unlike lead you never need to get to Full wrt bank health you certainly don't want to sit there for any length of time.Best when loads are not actively pulling the bank down, keep it at SoC 50% or even lower if "in storage" for days or weeks.Ideally only go to near Full just before you know loads will be pulling SoC back down.I've seen good designs where the critical LI bank goes isolated from the charge source(s), and a cheap lead bat acts a buffer (alt load dump) while the sources carry the loads.Bank only comes online for loads drawing currents bigger than what the charge sources are putting out.

author: badjob
author_rank: Contributor
timestamp: July 21, 2019, 12:34:28 pm
content: It seems the Epever charge controller isn't even smart enough to run loads from solar while in float and just pulls on the battery. So I'm going to have to build/buy something for load diversion that acts like the battery being undercharged and fake it out while keeping the battery cut off until current exceeds the panel's capability. Know someone that sells something like that or has made one?

author: badjob
author_rank: Contributor
timestamp: July 21, 2019, 02:13:44 pm
content: So load diversion aside, I can set up 2 scenarios. Which one is better?1. Float at 16.00, restart the boost at 15.7. Somewhere in between on 5-10A loads the controller starts feeding in amps to the battery (in either float or boost, seems the same) and replacing what was lost. A micro cycle maybe? Battery sitting fuller longer but doesn't drop very much.2. Float at 3.8v per cell (15.20), use the battery until then and restart charging at 3.7v (14.. A bigger cycle but a lot less recharging in tiny spurts and the battery sits longer at a lower state of charge.

author: john61ct
author_rank: Regular Contributor
timestamp: July 21, 2019, 03:58:34 pm
content: Quote from: badjob on July 21, 2019, 12:34:28 pmThat should not IMO even be under control of the SC.Loads are directly attached to the circuit between the SC and the bank.If load current demand is lower than SC output, (A) that's where it's fed from, bank not touched, only leftovers go toward charging.Only when demanded current exceeds charge source production, (B) does the bank get tapped for the difference, has to come from somewhere.Do not use the load terminals of the SC, usually very limited capacity, maybe even restricted by appliance type.I would reco Victron MPPT SmartSolar series, but that discussion deserves a new thread IMO._____> So I'm going to have to build/buy something for load diversion that acts like the battery being undercharged and fake it out while keeping the battery cut off until current exceeds the panel's capability. Know someone that sells something like that or has made one?Look at Sterling DC-DC chargers, ideally BB series. But, as above I do not see how it would solve a problem that should not be happening anyway.Quote from: badjob on July 21, 2019, 02:13:44 pm#2As stated not a good idea to Float the batt, IMO at all, but certainly not that high a voltage.Sitting at say 60% SoC, dipping a bit when (B) occurs, getting recharged back up to say 95%, is very shallow cycling, will get 4-10x more cycles than going down to low SoC.But your description for #1 is not how it works.I reco getting a decent Ah totalizing SoC meter, check out Victron BMV-712.And of course to the extent you only use solar, do get your bank to a higher SoC by afternoon, to the extent overnight loads are pulling it down.You want to "sit low" but "cycle high".

author: john61ct
author_rank: Regular Contributor
timestamp: July 21, 2019, 04:01:11 pm
content: Note that LFP and LTO will have many thousands more lifetime cycles than other LI chemistries.Even from new, EV batteries just don't last in use more than a few years.And I consider the danger from thermal runaway conditions to be a much greater decision factor than longevity.Do not charge unattended, and only at low charge rates.Put in multiple layers of automatic OVC and overtemp cutoffs, LVC as well. Ideally at the per-cell level.Use nowhere near a living space, ideally a concrete & steel back shed. Certainly not suitable for a mobile living scenario.Discard at 80% SoH, residual capacity compared to new.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 21, 2019, 06:02:10 pm
content: EV batteries are already a far safer chemistry compared to what's used in consumer electronics.

author: badjob
author_rank: Contributor
timestamp: July 21, 2019, 07:11:11 pm
content: These puff, they don't burn. Has been tested, even with punctures. They aren't LFE safe but pretty good. Not a bunch of 18650s. Guy is running a workshop off many many leaf cells with no BMS/crazy safeties. Although watching adam welch, he did just fine with 18650s, some monitoring and fuse wire.Also, its a small system. 200W in, only 66ah of storage (probably 80%'ed already guess I should throw them out). Not running my whole house off it. I just want to prolong that cycle life. But lets be real, I can't get a $300 victron when I paid that much for the whole system, much less to save $140 worth of battery. I can't not float at all, the epever doesn't support this. All I can do is float below charge level or float really far below charge level. In either case I don't really see amps flowing to the bank but not the load either, so there is that. I set up version #2 and will see how it goes next couple of weeks.Load terminals are 30A and loads <30A, the only other place to hook up would be the battery in which case I'm still draining it all the same. Unless you mean put another charger in between the SC and the bank which would mediate, in that case the voltages on the epever wouldn't really matter at all as it wouldn't be controlling the bank.QuoteThis is probably how house sized SCs work but it is not how mini all in one controllers work. Instead the Epever lets the battery drain a bit before any solar kicks in. It will feed the leftovers to the battery from either float or boost but at that point the bank has gone down. Eg, right now I have .10A load and enough solar to cover it but its still coming out of the battery. I will have to time just how much time it will take before a decent 2A or so load gets the solar going again.edit: so here is an example, ran for 15 minutes with a lamp on. there is solar but no juice.and all the parameters I can control:

author: john61ct
author_rank: Regular Contributor
timestamp: July 21, 2019, 08:03:26 pm
content: Yes IRL budget considerations can dictate abiding sub-optimal infrastructureKeep your eyes open on eBay, can often over time collect top-notch gear at crazy low prices.True I am more risk averse than most.Ability to test for changes in capacity & resistance is just as important as live operating protections.RCGroups and Endless-Sphere are also good resources.

author: badjob
author_rank: Contributor
timestamp: July 21, 2019, 09:25:52 pm
content: I have, might score a cheap pure sinewave inverter that way. The controllers are unfortunately $$$$$, especially with MPPT. This was the best I could do to be able to expand the system or use different battery chemistries.I've gotten this controller to effectively stop charging at the set point, but I can't make it leave the battery be and use solar as much as it can. So all I can do is constantly re-fill the battery or cycle while leaving the panels fallow.Even if I go to 3.92 or lower the behavior will be the same just at a different SOC. Btw, this guy had the best explanation for this charge controller:and he is "floating" at 16, re charging at like 15.9, but he is using way more energy overnight and I'm not. Its more of a backup/experimentation setup. I have room for 1 more 200w panel and that's it. So all I had in the future was buying a 200w bifacial from a local supplier and adding 2 more leaf batteries topping me at ~14-20A max current in and 120AH storage. Enough to cover me in a power outage for vapes/phones/computers/radio.The only other thing I can think of is to get the correctly sized one of these :https://www.ebay.com/itm/332644017121 and just dump the PV into a buck converter once the battery reaches where I want it to be.

author: john61ct
author_rank: Regular Contributor
timestamp: July 21, 2019, 10:11:59 pm
content: SmartSolar 75/15, handle any 200-260W panel just fine, ideally 40+Voc BT connectivity to the phone app built in$119 new from many sources

author: john61ct
author_rank: Regular Contributor
timestamp: July 21, 2019, 10:28:49 pm
content: Quote from: badjob on July 21, 2019, 09:25:52 pmUnlike wind, there is no real reason to switch-divert solar to a load dump.Or are you thinking to use this to isolate your LI bank take it offline?I'd want a firm assurance about the bottom end of the setpoint range.

author: badjob
author_rank: Contributor
timestamp: July 21, 2019, 11:59:21 pm
content: That's 1/2 the charge controller for $20 more and I wouldn't be able to expand whatsoever. Plus it can't turn off float either. I end up in the same place for more money.QuoteBasically. Take the charge controller/batteries offline and use the panels by themselves to power whatever through a buck converter.

author: john61ct
author_rank: Regular Contributor
timestamp: July 22, 2019, 12:26:34 am
content: I've come across so few decent charge sources of any type that allow Float=None, better to design as if that does not exist.You'll need a cheap batt to buffer output anyway, maybe use Starter or a decent little lead Reserve bank for that.Tripping a relay/contactor to take the LI bank offline based on hitting a HVC setpoint does not require anything specialized, hundred ways to skin that cat.And the SC stays on the load carrying side, not sure what a converter's needed for?The Victron's adjustability, flexibility, build quality and feature set are way beyond that Epever, IMO cheap enough to use 1:1 with well-matched panels to optimize partial shade handling.But different budget ranges, I understand. . .

author: badjob
author_rank: Contributor
timestamp: July 22, 2019, 12:32:16 am
content: I have a little Gel battery to buffer or if running a laptop I can use its battery. One of those $10 PWM deals would work too.

author: john61ct
author_rank: Regular Contributor
timestamp: July 22, 2019, 12:33:49 am
content: Again, why put loads through the SC?Set up a distribution box / bus, fed direct from the batteries' circuit.Some load terminals really are limited on what **type** of devices they support, and do not meet their current limit spec.Often designed just for streetlights, certainly not an inverter.

author: badjob
author_rank: Contributor
timestamp: July 22, 2019, 11:43:54 am
content: I have 30A load capacity on the epever (its legit, same size as the inputs), for a pwm deal it would depend on the load terminals, in that case probably directly off the buffer battery. Something would have to keep it from overcharging though.With no buffer it could just go straight from the buck converter on a sunny day. The point is to use the sun and not the battery, no?Epever is saying it should be powering the loads so I'm sending them info to see, maybe they'll fix their bug, who knows.

author: john61ct
author_rank: Regular Contributor
timestamp: July 22, 2019, 04:32:58 pm
content: Quote from: badjob on July 22, 2019, 11:43:54 amI do not know what that means.Nor this:> Something would have to keep it from overcharging though.With no buffer it could just go straight from the buck converter on a sunny day.> The point is to use the sun and not the battery, no?Yes, but that is what happens, no matter where in the circuit your loads tap in, as long asthe SC current output covers the active loads.Only when it doesn't, do the loads pull from the batteries.Another angle - when loads are high, battery charging stops. They only get the current "left overs" available net of what the loads aren't using.Again, do not use SC load terminals, best to run your distribution kit directly off the battery bank.

author: badjob
author_rank: Contributor
timestamp: July 22, 2019, 09:43:37 pm
content: It means the load terminals are rated for 30A current.QuoteIf the current isn't sagging the battery voltage, the SC won't feed anything from the solar. This is how it worked with lead acid but not really lithium. On the lead acid there was an immediate drop if I hooked something to load or battery that drew a lot of amps.

author: john61ct
author_rank: Regular Contributor
timestamp: July 23, 2019, 01:19:57 am
content: Sorry just not following, need more precision in the communications.But never mind, I stand by what I wrote, but carry on as you like, it's your rig.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 23, 2019, 01:46:59 am
content: Something else that might be worth trying is to program the charge controller to regulate at 4V/cell, but then have a separate circuit that starts putting on load when the voltage is over 3.9V/cell. In other words, it will attempt to match the load to the source. Something that is a kind of energy storage (e.g. a Peltier cooler) or that can run on an adaptive schedule would be a good candidate.

author: ejeffrey
author_rank: Super Contributor
timestamp: July 23, 2019, 04:29:30 am
content: Quote from: NiHaoMike on July 21, 2019, 06:02:10 pmA friend of mine burned down his garage with a repurposed Leaf battery module. The chemistry may be more stable, but the stored energy is high and you still have to use protective circuit. And when you are talking about used EV batteries from ebay or a junkyard with unknown history (e.g., might have been damaged in a crash), there is even more reason to be careful.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 23, 2019, 05:13:45 am
content: Quote from: ejeffrey on July 23, 2019, 04:29:30 amIt goes without saying that it's important to inspect batteries before use and to always use a BMS. (That infamous reused Tesla pack that caught fire was - you guessed it - used without a BMS.) Oh, and just as an extra layer of protection, are you aware of how cheap fire sprinklers are? In fact, given how an unwanted sprinkler activation is considerably less problematic in a garage than in most spaces, I'm surprised they're not required in new construction.In environments where water damage is of big concern, you can use something like CO2.

author: badjob
author_rank: Contributor
timestamp: July 23, 2019, 11:53:16 am
content: What were the circumstances of the fire? Did he overcharge it like crazy and something failed? I have heard of tons of tesla fires because they are just a ton of long 18650s. When searching for leaf fires all I can find is info how the battery did NOT catch on fire. Its why I didn't want to use that chemistry. Gen1 leafs have no cobalt AFAIK.Plus this:I can see how you can start a fire if you short and arc it, but that's true for any high storage battery with lots of current. You could probably weld with that arc.John, I don't understand what you don't understand. When you have a 20A circuit in your house what does that mean?