Upgraded battery charger?

rmachin

New Member
Anyone think it worth upgrading to a smart(er) charger that can charge slower/within set limits? Worth it for battery longevity? Perhaps the included charger is smart enough..
 

Thomas Jaszewski

Well-Known Member
I bought a Satiator because i can charge any of my batteries from 12v to 52v at any percentage, at a range of amp rates. It was expensive but compared to owning 5 chargers with none of the parameters and doubling the service life of a single battery, paid back the $300 with my first battery. Also a warrantee beyond ant other.

DISCLAIMER. However, i now have sold several, so i do have an interest. I own a 48 and reetly added a second 72v ow my ackup is also a Satiator. Made by oe of most advanced eBike cotroller and display manufacturers available. Grin, ebikes.ca.
 

mrgold35

Well-Known Member
I would factor in your daily/weekly/monthly/yearly mileage to see if you need to stretch your battery longevity to save $$. It is around 12-13 miles round-trip for my commute at around 60 miles per week average for 3-4 commuter days per week. Even if my battery power is reduced to only 1/4 to 1/3 after 3 years, I'm well withing my range for work commuting. An added plus is I have two Radrovers (his and her) I switch off weekly to keep the mileage about the same. I thinking splitting the mileage between two bikes will also help with battery longevity since the charge/discharge cycles are half as much compared to having a singe bike.

I haven't done the math to see getting a second battery is just as effective as getting a smart charger? I sometimes take my wife's battery on longer rides of +30 miles and it has saved me a few times (a stiff headwind can really drain your power).
 

rmachin

New Member
Thanks for the input. It sounds like factoring in the potential drop in battery prices over 2-3 years and the fact that smart chargers for these types of batteries are pretty expensive...its probably a wash.
 

Thomas Jaszewski

Well-Known Member
Thanks for the input. It sounds like factoring in the potential drop in battery prices over 2-3 years and the fact that smart chargers for these types of batteries are pretty expensive...its probably a wash.
Unless you have more than one battery or are someone who uses their battery every day for some significant mileage. Even if not there are advantages to a better charger. 100% charges may actually shorten battery life, but the opinions there vary. Before I started selling chargers I used an advanced charger for several years. BUT I have 36, 48, and 52V batteries. That makes it a no brainer. Even so I've always been one for having the best I can afford and given the cost of batteries. I have several friends that accomplish 80% charges with a timer and multimeter. Two items every one of us should absolutely be using anyway.
 

rmachin

New Member
Well I did read that a big part of the prius battery longevity is the management, keeping charge and discharge levels between set limits, watching temperature, adjusting speed of charge etc. so I see your point.
 

Thomas Jaszewski

Well-Known Member
Well I did read that a big part of the prius battery longevity is the management, keeping charge and discharge levels between set limits, watching temperature, adjusting speed of charge etc. so I see your point.
It's the idea of spending $300 on a charger that bites. It's hard. Even for someone who's flush. It's a big price tag when a basic single voltage can be as low as $30. I like that I have a battery history on the charger as well. I'm to old and daft to keep track on my own. Especially with the number of batteries I own. But I jumped in when I had just 2 36V. They were the price of 52V batteries, or more, when I bought them.
 

jazz

Well-Known Member
If you didn't want to spend that much on the Satiator, which is probably the best aftermarket charger you can buy, you can always buy an outlet timer to shut off your charging after a period of time. So if you knew it took 4 hours to reach 100%, you could have it shut off around 3.5 hours or something like that. Not nearly as accurate but cheap
 

Thomas Jaszewski

Well-Known Member
If you didn't want to spend that much on the Satiator, which is probably the best aftermarket charger you can buy, you can always buy an outlet timer to shut off your charging after a period of time. So if you knew it took 4 hours to reach 100%, you could have it shut off around 3.5 hours or something like that. Not nearly as accurate but cheap
Absolutely! It works very well, and with just a little practice can be quite accurate!

That said, after spending nearly $3000 on a build, $300 for a charger didn't seem like over the top.
 

Embra

New Member
I have a phone app that claims to provide ongoing monitoring of the phone's battery charge status. It's provided some insights to me for best charging practices to prolong battery service life, and justification in my mind for buying a Satiator.

Two caveats to acknowledge up front:

(a) phone batteries and ebike batteries are not exactly the same thing. They're both li-ion, so I am presuming that the data I am seeing is at least conceptually applicable to my bike battery, so it's not an apples to oranges comparison. Rmachin's mention of prius battery management is indeed relevant; recommendations for the Nissan Leaf that we leased were to keep the charge between 20% and 80% as much as possible--the same stuff I hear and read for all different sizes of li-ions.

(b) I don't really know how valid the app's data are...I take them at face value. However, trends in the data seem useful even if it is the case that accuracy is less than ideal.

So I'm posting two screen shots that show charge and discharge histories. The number I would direct your attention to is the battery wear cycle associated with each particular charge. One full cycle would be required to charge from a depleted battery to 100%. There's variation in how many cycles a given battery can endure (affected by environmental factors like temperature), but here's an estimate table of how many recharges from http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Discharge cycles.JPG

So in the screenshot from my phone, note that charging from 5% to 20% (a 15% boost) took .02 cycles. Charging from 19% to 80% (a 61% boost) took .21 cycles. But the last 20% from 80% to 100% took .74 cycles. So holding the charge to 80% or so does appear to make a significant impact.

Charge cycles.png

My practice is to recharge to 80% whenever my batteries get down to 50% or lower.; The Satiator makes it easy for the one it works with, and I can also set it to charge slowly at 2 amps (supposedly makes batteries happier). I use a timer to charge the Copenhagen Wheel since it's got some complicated communication protocol that the Satiator can't figure out.
 

Doug Devine

New Member
I think it wise to question the charge and discharge limits. However, I think we're good with the stock stuff. Here's my thinking...

The charger says it outputs 2A. The data sheet for our cells states a capacity of 2.7Ah. That equates to a max C rating of 0.74 (= 2/2.7), well within the generic recommended range of 0.5 and 1.0 for our (18650) cells. Sure, a lower charging current will be better but *how* much better? To me, not enough to worry about. It already takes 5+ hours to fully charge a depleted pack. I wouldn't want to wait any longer (because I often times ride twice a day on the weekends).

As you know, charging rate isn't everything. So what's the upper voltage charging cutoff point? Every time I pull my pack off the charger, it registers 54.6V exactly. Seeing how we have a 13S pack (13 groups of cells wired in Series), that means each cell is charged to 4.2V (= 54.6/13). This happens to be the cell's upper charging limit, per its data sheet (attached). I'm comfortable with charging to the max every time because I ride frequently. But if I was going to take a hiatus, I would make sure the pack was 46.8V (3.6V per cell). You want some juice in there but not too much.

Regarding discharge, our controller says there is a 40V low voltage cutoff. Thus, the controller will not allow the cells to work if their voltage drops lower than 3.08V (= 40/13). Some people are adamant this is too low, others don't fret until the 2's. And quite a few 18650 cells' data sheets say their discharge cutoff voltage is 2.75V. Like a grade school teacher's answer key, answers may vary.

In real life action though, I haven't seen my pack drop below 44V, which is 3.3V per cell. And I push the limits of that last bar on a regular basis. (I'm guessing the BMS in the battery pack has a higher low voltage cutoff.)

Of course, all this is predicated on the fact that the stated limits are the actual limits. I can't speak to that.

By the way, I'm no expert but I do like to learn how things work. So if I'm off base, someone call me out. Or, on the flip side, if this is common knowledge, let me know and I'll keep my trap shut.
 

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