LiFePO4 Install

[Bear in NM]

yeah PV is cheaper than more LFP, and expected to last longer.. I freely admit I overdid solar, I'm good w/half of my capacity.. the fixed roof one still provides abundant power.

but I'm planning for a bit of future expansion still.. I want to work from boondocking camp indefinitely.. write some code out in the woods during the summer and just live a nomad.. Wife has to travel frequently enough for work we could end up anywhere if we tag along.. Running a nice giant monitor, cell phone repeater, and charging a laptop would take quite a bit of juice, and I need that times two for the wife who is a project manager.. and there's also the future potential of EV toys that could be on the table eventually, some electric dirt bikes would be sweet around here if I could charge em effortlessly w/the sun.. otherwise I'll stick w/Gas and never hope to see much wildlife on the trails.. I may consider a mountain bike w/Electric assist to help my old ass get up the mountain.

Also the excessive solar still produces very admirable output when the sun's not shining.. I can get in overcast what most here w/100AH of lead cant get in direct sunlight.

As to the EV part of the equation, I just did that to my system. With 270 watts on the roof, with an additional 100w portable and 160 amps of AGM, I went from more than enough all the time to "oh crap, how to add a 32 ah 60v E bike battery" to my load. My bike is a Sur-Ron, and requires a 1000 watt inverter (actually needs 750 watts), which was not even remotely on my radar a few months ago. Hey, I don't need a microwave, or AC or a drip coffee maker in camp.

I did a first run test a few weeks ago, and with my limited battery capacity it made sense to start charging before the sun was up full, to try and hit the low end of excess solar with full charging, and finish the bike charge with enough solar time left to get to float on the batteries. Worked pretty well. But having the bike means I might rather be riding earlier in the morning. My solar is pretty much maxed out out for my van, so it is either bigger house battery bank, or perhaps buy a second bike battery.

While I am not sure how I will be moving forward on the charging side of things, the one thing that is perfectly clear is that I will work the E-bike into my system. It is beyond fun to ride, and have as spare mobility when out.

back to the theme of having too much solar. Yea, maybe right now.......

Craig

 

[john61ct]

Charging a DC battery is much cheaper and more efficient without AC power in between.

Yes a lot easier if you plan ahead and design your packs to match the excellent DC-powered chargers and PSUs out there, takes a bit of creativity, but not rocket science.

 

[shade]

While I am not sure how I will be moving forward on the charging side of things, the one thing that is perfectly clear is that I will work the E-bike into my system.

I'm guessing this is your charger: https://lunacycle.com/sur-ron-li-ion-10-amp-battery-charger/

I'd start looking for a DC option. Someone has - or soon will - figure that out. There's such an obvious need that I'm surprised they don't already offer one.

I'm starting a parts list, and one of my goals is to give myself some headroom for just what you're experiencing with suddenly adding more loads to your system.

 

[john61ct]

There are dozens actually hundreds of charge sources that will do the job already.

Just not plug and play automated without modding anything.

But the ebike world is all about DIY, adapting stuff to save money.

endless-sphere.com and rcgroups.com is where the gurus live, a new thread with a properly worded title will get lots of suggestions.

Best approach IMO would be relatively slowly charging a larger bank at 5V higher voltage than you need, then using DCDC buck converters capable of fast-charging the bike packs, with a current-limiting feature.

If automated stop-charge is desired, then a separate HVC is needed, unless the pack BMS includes a robust one.

Balancing is also an issue.

The ideal would be custom packs at 2* 8S in series while in use, charge each separately @33V with a common cheap RC balance charger.

These usually run off a DC supply, but to get high current rates, want 24-40V input.

Obviously balancing properly every charge cycle will be of huge benefit to longevity.

Just be aware these LI chemistries are nowhere near as safe as LFP, boom bad, so

charge outdoors,

discharge to 3.7V before traveling,

discard packs when SoH drops 25-30% at the latest, etc.

 

[Bear in NM]

Shade,

Yes, that is the charger. I have just started to ponder this situation, and have finally figured out the connectors I need for the battery discharge and charge terminals. I have these on order now, so at least I have the connectors I need.

John, thanks for that information. I have only looked briefly at DC to DC for this application, and did not see much in the way of buck converters going up to 60 volts. That was my first thought, Dc to DC for efficiency, but I am not going to risk a 1500 dollar battery on a 19.95 dollar Chinese buck converter that may or may not really push constant voltage and/or constant amperage correctly. I need to do a LOT more homework, and I will check out the links you posted. Thank you.

I do not think trying to split charge would at all workable for my bike battery, as it is already made and sealed to the elements. Basically I have the charge port of the battery, which does communicate in some way through a data pin, or the top discharge side, which is two pin, positive and negative. Again, a lot to educate myself before doing anything other than perhaps add a second bike battery, perhaps a Cycle Satiator programmable charger, and try to not hammer my system too badly.

OP, I hope you are OK with this little sidetrack. Accessory E-Vehicles add a bit of complexity to our solar systems, for sure.

Craig

 

[john61ct]

I am not going to risk a 1500 dollar battery on a 19.95 dollar Chinese buck converter that may or may not really push constant voltage and/or constant amperage correctly.

100% agree, even charge sources costing $500+ should never be trusted.

Always monitor / periodically verify V&A with independent known-accurate tools.

Always have protective circuitry HVC in this case, for when the primary controls fail, in addition to a good BMS if your packs have them.

Temperature sense, imbalance detection

With high C-rate non-LFP lithium chemistries especially critical.

Burning down the house / shed / trailer etc is always a real & present danger, safety first.

_____
> I do not think trying to split charge would at all workable for my bike battery, as it is already made and sealed to the elements.

Sure, but packs are consumables, something to keep in mind. Could even build "travel use" packs specifically for off-grid, keep the stock one much longer for when charging off shore power.

Satiator is a **fine** product, all Grin Tech stuff is, and Justin very accessible in the forums. Bulk charging only relies on the BMS for charging though, which can get dicey as the packs get worn over time.

 

[Bear in NM]

John,

hey, cut that out. I was in very deep thought going through an Endless Sphere EV thread, when I got the email notification of your reply here.....That's a cool place, which is going to get a bookmark.

Thanks again for hammering safety. 18650's are typically considered safe from what I have read, but perhaps on a battery type spectrum, not really. I have been heeding your thoughts on safety thus far, and will continue to do so. I have debated about pulling the battery out of the bike for charging, thinking that may be undue wear on the main battery breaker and battery leads, but perhaps a burned up battery in the charger is better than a burned up battery and bike I ordered a spare breaker and battery lead terminals earlier today, thinking better to wear out a small part, and be safer.

yes, I understand the battery is very much a consumable. I am actually treating my entire bike as somewhat consumable in that there is only one place stateside to get parts. I had actually planned on educating myself on building "things" for my bike, in the event I am left without sources. Hey, now I know what a 18s 4p is now, so making headway. With my luck, about the time I get the tools and know how to build a proper battery, is the time the big "break through" in super capacitors hits, and I'll once again be a dinosaur.

For all of us here who dig solar and batteries and back country self sufficiency, E-support/fun vehicles seem like a logical next step. Charging our lights and fridges is cool, and very helpful, but having an e-bike to rip around the back country is cool, and about the most fun you can have with your pants on....

Craig

 

[john61ct]

18650 is just a size spec, the chemistry of the anode/cathode materials is what gives it various different properties.

You can get LFP in the various little cylindricals, much safer but about half the power density, so most would not consider for propulsion use cases anymore.

RC type LiPo and big pouch or prismatics are other options, but 18650s dominate.

Best way to go is source quality cells buy in bulk and assemble your own packs to your own specs. But ES also have good trusted pack builders that are competitive and far outstrip what you get on eBay / Ali / Amazon assembled in China.

Meantime do coddle your packs and you can get double the cycle lifetimes out of them.

And keep reading on ES, some older threads really have gold in em.

 

[dreadlocks]

So this last weekend, I needed the portable panel for the first time.. Parked right next to trees on all 4 corners, fixed panel only got about 45mins of direct sunlight and on the first day a big fluffy cloud came over right as it was cranking up the output.. was a losing battle until I setup the portable one out in the direct sun.

I also had not recalibrated the BMV in a while and it was off by about 11%, so I hit the LVD cutoff (~20% SOC) and it took me a lil bit to figure out why everything had gone dead @ ~30% SOC.. fixed the BMV so the solar will trigger a calibration once it hits 14.4v automagically.. Plugged it into shore power for first time in a really long time and let it charge up to 14.5v so it could balance all the cells properly.. dont seem like any harm was done, the LVD saved my ass since BMV was over-reporting the SOC.

 

[john61ct]

Making Your Battery Monitor More Accurate - Marine How To

Program The Ah Capacity This article features the older Victron BMV-602. The 602 has been replaced by the BMV-7oo series (700, 702 & 712). Everything in this article is still relevant to the current series of BMV-7xx battery monitors. WARNING: This article

marinehowto.com

Other good articles, search "monitor" on the FP

 

[shade]

So this last weekend, I needed the portable panel for the first time.. Parked right next to trees on all 4 corners, fixed panel only got about 45mins of direct sunlight and on the first day a big fluffy cloud came over right as it was cranking up the output.. was a losing battle until I setup the portable one out in the direct sun.

I also had not recalibrated the BMV in a while and it was off by about 11%, so I hit the LVD cutoff (~20% SOC) and it took me a lil bit to figure out why everything had gone dead @ ~30% SOC.. fixed the BMV so the solar will trigger a calibration once it hits 14.4v automagically.. Plugged it into shore power for first time in a really long time and let it charge up to 14.5v so it could balance all the cells properly.. dont seem like any harm was done, the LVD saved my ass since BMV was over-reporting the SOC.

That brings up something I wanted to ask you. Have you experienced this problem?
"Victron MPPT controllers consistently fail to fully charge batteries in intermittent sun, due to a bug in their "smart" Absorption timer algorithm." - from the Victron Energy forum

Also, I found an article about BMV auto-calibration that describes your experience. Makes sense that it would need to see the battery fully cycled to know what's there to work with, but it'd be nice if there was a less precise manual method for recalibration.

 

[dreadlocks]

yeah that don't affect me on LFP as absorption time is kinda moot, once the battery hits 14.4v I'll consider it charged, Ive got float set to 13.3v.. what I see is the battery charges up to 14.4v, and will now trigger a recalibration for SOC (before it was set to 14.6v and was only recalibrating when I was externally charging it completely to balance cells), it will hold it there for a whatever it determined.. dont matter to me how long really (max 30m) and then the loads will bring it back down to 13.3v once its in float which is ~90% SOC, then the solar will power everything and the battery will basically sit at 90% until solar output has gone and its back to battery.. I suspect even if I was running lead, with my 60v panel it would not reset itself with a cloud going over.. it produces +5v over output until its completely dark.

Based upon discussions here and further research, maintaining a LFP at 100% SOC will result in reduced cycles.. so mine is setup to normally operate in a window between 20% SOC and 90% SOC based off the 14.6v calibration, now that its going to calibrate at 14.4v those may shift a little bit since it will now consider 14.4v 100% SOC.

Not sure how often I should take it up to 14.6v and 0.00A input for cell balancing purposes, but I'm not doing it very often.. so far only twice this season, today and back in April when I brought it out of storage.. I do this manually and once battery stops taking any input I pull the disconnect and let it sit for a few hours, then put the battery back into service.. So it had been quite a while since the BMV had been calibrated.

 

[shade]

yeah that don't affect me on LFP as absorption time is kinda moot

Good to know. I wasn't sure if the reset was doing anything else that would interfere with LFP charging.

I'm a little surprised Victron doesn't make that shade-reset absorption timer a manual parameter. Seems like that would solve the problem for people like that OP.

 

[dreadlocks]

I think its something in the pipeline, I found a similar issue w/multi-controller setups which they were gong to address with some new config options as well as syncing the controllers so they all have same absorb times.. with multi controllers the first array to come online for the day would get the correct absorb time calculation, but any other arrays would come online even moments after would make a bad calculation because they are already seeing a charge current going to the bank.. so part of syncing all the controllers was figuring out which one had the right absorb calculation.. I seem to recall them mentioning a new option in the works that was supposed to allow you to just disable the absorb calculation all together and just use a fixed configurable value for those whom dont like the way they calculate absorb time.

 

[dreadlocks]

Found my main ground had worked its way loose from all the forest roads I been traveling.. almost convinced me my LFP had gone bad.. freak out moment, fuuck.. this is probably the reason why LVD was kicking on on me this weekend.

weird it was the output of the shunt that was not as tight as it shoulda been was causing the BMV to read low voltage too.. you'd think it'd be getting ground from the battery and still showing good voltage?

Bad Ground vs Good Ground


Ive got a ground bus bar here that I have been lazy to install, well guess now I better get too it.