Solar Panel to charge a 52v 13.5 ah battery pack?

Thanks Amberwolf, That was the information I was still missing. I appreciate your help!!

Franko


amberwolf said:
BTW, to be more specific, to get the rough charger end voltage for 80% of the voltage of the battery, it's 80% of the difference in voltage between empty and full, added to the empty voltage.


However--if you want actual 80% of charge state, you have to know which cells are in the pack, then look at the actual cell specification sheet, which has a voltage-vs-state-of-charge chart. Then find 80% on that particular chart, and multiply by the number of series cells. Then use that for the charger's final voltage.


Just keep in mind that if you don't at least periodically charge to the full voltage, the BMS probably won't balance the cells. It won't matter if they're really good cells that are well-matched and used well within their specifications and not run down too far; if they stay balanced there's no worries. (but it would require manual checks to find that out).
 
MPPT BOOST low low price!
https://www.youtube.com/watch?v=omAhsQqwWSo&t=248s
see update too. set V, does not trickle.
similar version on ebay $33
very cool at such a low price! 300 watts! 24v up to 100v
 
What about the Victron 100 / 20 ?

https://www.victronenergy.com/solar-charge-controllers/smartsolar-mppt-75-10-75-15-100-15-100-20
https://www.victronenergy.com/upload/documents/Datasheet-SmartSolar-charge-controller-MPPT-75-10,-75-15,-100-15,-100-20_48V-EN.pdf

I just ordered ~150 euros (incl. taxes and shipping) which makes it 100 euros less than the Genasun on the European market.
There is a good-looking app to connect to it via Bluetooth and the output voltage can be set from 30V to 68V, to match any e-bike battey type. It can take solar power up to 290W (12V) to 1160W (48V). It claims 98% peak efficiency and weights 650g, with dimensions 10 x 11.3 x 6 cm.

In comparison, the Genasun for a 52V battery (https://genasun.eu/collections/genasun-boost-mppts/products/genasun-gvb-8-lithium-58-4-volt-wp-mppt, 250 euros including shipping) covers an input power range of 105-350W (60V max, 8A max from the PV), and claims peak efficiency of 99%. It weights 290g, with dimensions 14 x 8.1 x 5.5 cm

From these specs, besides the weight/dimension, everythings speaks for the Victron (input and output range, price, bluetooth interface for settings). Would anyone expect the Genasun to be more efficient?
 
One doubt I have though, is how well suited the Victron is for lithium battery. Here are configuration screens from Victron Connect app (demo 100 / 20):

Screenshot_20210213-115213.png

Screenshot_20210213-115250.png

Joseph from em3ev tells me absorption voltage, float voltage and equalisation voltage are lead-acid parameters, so the menu was probably designed for lead-acid battery. On the other hand, the default setting is "Li-ion 48V" so it seems as if it can accommodate for a Li-ion 13S. I just wonder whether that makes for a crude, good enough approximation or whether the charge profile of Li-ion can be fully determined by these parameters. In any case, if that works for 13S 48V, it will also work for 14S 52V.
 
Ok, so from what I could gather on the internet, the lead-acid charge is rather more complex than the lithium charge profile, and that every phase of the lithium charge profile is contained in the lead-acid curve, so I am becoming more confident that it can simply be adjusted.

FYI, see the following, supported by the pics attached

a) Li-Ion charge profile :
- CC phase with a constant current, while voltage increases in response (also called "bulk" phase)
- CV phase with a constant voltage, while current decays to zero in response. When the current reaches a low threshold, the charge is considered complete (note that the Grin Satiator uses a threshold for diagnostic only, to display "Charge Complete", but does not stop the current from flowing into the battery until it reaches a "real" zero)

b) lead-acid charge (second and third pic)
- bulk charge (same as Li-Ion CC)
- absorption phase (same as Li-ion CV)
- equalization phase (in third pic only): looks like a short step in current, that's the only difference with Li-Ion, as far as I can tell
- float (storage) : used for storage, not different from the absorption phase, but with a lower voltage

Anyway, from that it looks to me that Li-Ion actually needs only a single tension as a parameter, which is the threshold between CC and CV phase.
Mathematically, it would be enough to set the lead-acid parameters at the same tension, which is 58.8V for 100% charge, or say 56.8V for 85% charge (according to the Grin Charge simulator)

- absorption voltage : 58.8 V
- float voltage: 58.8 V

The equalization voltage does not need to be set because it is only activated manually (and should not be activated with Li-ion).

I wonder why the default settings for Li-Ion look different, but I trust the Grin charge simulator to be accurate and the meaning of the parameters is clear enough. Note there is a "Max Charge current" set to 20A by default, which should probably set to 7A (like the Grin Satiator), though whether that matters or not depends on the size of your photovoltaic panel. With a 110W panel (like the Sunpower one that I am waiting to arrive), 110W / 56.8V (for a 85% charge) is just under 2A, and that will only be reached with perfect solar condition. You'd need 4 such panels to threaten your battery and require the max current setting.

EDIT: the value of the float tension is subject to debate and it related to whether or not a Li-ion battery should be kept for a long time at a certain tension. On the constructor forum, someone recommends setting the float voltage to the nominal voltage instead (I believe that corresponds to somewhere around 70% change). That means, the charge will stop after absorption, then start again whenever the battery voltage drops below nominal. Just make sure the absorption lasts long enough (set tail current to 0.1C, meaning 10% of the numerical value in Ah from your battery, and possibly use a long fixed absorption time, but maybe adaptive is OK too) Here some more info about float charge for Li-ion (unclear but not too bad).

Anyway, these are details about settings, the bottom line is, this solar charger should work just fine, leaving plenty of freedom to fiddle with your desired charge behaviour. On the Genasun vs Victron question, I retain that Genasun is lighter but is not programmable. I expect efficiency to be similar but that remains to be tested.
 

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Hi Mahe, those Victron MPPT controllers look like bucking units, as in they drop from a higher panel voltage to a lower battery voltage. That means they are not directly comparable to the Genasun boost controller. I'm trying to figure out MPPT for a solar bike project and it's a mess because I can put two panels in parallel and get too much voltage for the controllers I like, or two panels in series and get too much current.

This is the closest match I've found so far to what I'm looking for, FWIW: https://www.ebay.com/itm/MPPT-Boost...-Charger-Controller-48V-72V-Blue/184562363524
 
Hi k2orbust,

(edited a previously erroneous post)

it seems that you are right. The victron i was talking about (100 / 20 48V) does NOT work as boost controller, and requires a voltage +5V more than battery voltage to function.

FYI, a friend who participated in thesuntrip.com used genasun. If you PM me I can put you in contact.

Mahé
 
k2orbust said:
I'm trying to figure out MPPT for a solar bike project and it's a mess because I can put two panels in parallel and get too much voltage for the controllers I like, or two panels in series and get too much current.

Looking at the datasheet, https://www.victronenergy.com/upload/documents/Datasheet-SmartSolar-charge-controller-MPPT-75-10,-75-15,-100-15,-100-20,-100-20_48V-EN.pdf

the Victron 100 | 20 48V takes up to 1160W for a 48V kind of output (it actually takes 60V batteries, maybe even 72V as far I can judge by the settings on the companion software).

Take a sunpower 110W panel of ~19V as an example. Having 6 of them, three in series and two in parallel would provide you with 57V and 660W. Adding 3 more, for a total of 9 (3 in series and 3 in parallel) give you a max 990W of power at 57V. Isn't it what you are looking for?
 
Hi Mahe, in my particular my case I bought the solar panels first and then played catchup finding a charger controller that would work with them. A new option came up (https://ebikes.ca/shop/electric-bicycle-parts/solar/adjustable%20400w%20boost%20mppt%20with%20led%20display_cg-mppt_el400.html) and it looks like that is going to work!

It's true, if you can put enough panels in series then the voltage rises above the battery and you can use a buck converter. You do need to be mindful of voltage dropping as the panels heat up or when they are shaded, tho.
 
Is low current an issue when charging these packs? Even if you keep voltage steady, wont a very slow amperage degrade the battery and/or components if it needs to be ran + 7 days for a charge (which during that time the amperage would probably be 0.5c to 0.1c then divide by 5 since its a 5p pack)?

I live in an apartment with 'electricity' included, but ive been wondering if I could charge my battery easily (for fun). I got a 52v (15s5p) from em3ev that is charged with a grin satiator. I also got an old portable "allpowers 80w" panel (that has a 18v output, but probably can't even give me 40 watt as its in a window without direct sun). Even if I got a DC booster converter with some sort of solar charger im worried it might damage the battery in the many days it needs to spend charging.

My second idea would be to buy a a 12v 35ah lead acid battery, a solar charge controller for that battery, then an 12v inverter (so I can use my 12v battery with the satiator to charge my 52v battery). But at that point im spending +$200, introduce lots of inefficiency, and have a lead acid battery...
 
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