Is my 48v 15Ah LifePo4 battery (from Sun-Thing) healthy?

Hi Guys & Girls, I have a scooter and had SLA's and when it was time to change them, I bought a 48v 15Ah LifePo4 16s battery from Sun Thing @ 2 years ago. I tested it at the beginning and it produced @ 14.5 Ah and seems to balance fairly quickly. My average trips are @ 6-10 kms, and have done a few 40km trips. I also do @ 100 trips a summer to back & forth to work that is only 2 kms (1km each way) and I end up charging the battery at the shop. I have done @ 2000 kms with the scooter with the 48v 15Ah LifePo4.

I just wanted to ask a few questions...

1) It came with a bulky 5amp charger (it also charges to 59.9v), but I tend to always use my spare 3amp 48v charger that appears to charge up to 59.9v and stays there while it balances the pack. Is the 59.9v a little high, and is it damaging the cells?

2) When I take the battery off the charger, the voltage drops to 55 or 56v, and if I ride the scooter a little, it will stabilize at 53.24v (I presume this is good since 3.3v x16 = 53.28v)...?

3) I am curious what is a normal voltage drop as when I ride and draw .5C (7-8amps) the voltmeter says @ 51v, and when I draw @ 1C (15-16 amps) the voltage drops to 49v. If I hammer the throttle and draw 25amps, the voltage drops to @ 47v. I presume that these are normal/healthy numbers for a 15Ah LifePo4 battery?

4) I am a big guy (250lbs) and ride at @ 22km/h (appears to be a quiet/efficient speed) and have figured out that the scooter consumes .4Ah per km, or 20Whr/km. If I did @ 2000 kms on the scooter, at 20Whrs/km, I assume I consumed 40k watt hours. So if my calculations are correct, I have only used @ 55 cycles from it, and the battery should do @ 1000 cycles...?

5) So it appears that I will never wear out the battery from exceeding it's cycle life specs, but how long does a LifePo4 used this way last.... 3,5,7,9 years?

You guys are simply amazing with all your knowledge, so thanks in advance for any replies and info that you can share.

IAN

IMO, your lifepo4 is acting pretty normal for two years old.

It's possible a lower charge would be better, say 58v, but lifepo4 is very tolerant of overcharge, and I see no particular problem with charging to 59v. So maybe better, but not so much better it will cost you much, if anything at all.

Expect at least another year, possibly two, but performance will be poor in the 4th year. Sounds like your needs are modest enough that even in year 4, you'll have all you need.

It's possible that it could last even longer, but typically a pouch cell pack like that eventually gets a hole, or enough dents in the end pouches to cause problems. Then when one cell puffs, its straining the other two. At that point, you actually only have a 10 ah pack. Then it gets harder discharges, and starts to fail other cells.

But I'm confident that it is acting normal now, and it should last you through next summer. Nevertheless, maybe start saving, or budget for a new pack ordered next spring.

It's getting harder for those guys to sneak batteries on planes illegally, after the hoverboard fiasco. So when your pack dies, you might have to wait to get another, or pay a lot for one that ships from a local vendor.

Dogman, thanks a lot for your reply and basically a confirmation of the thoughts that I was having.

I also thought that 59.9v (or basically 60v charging) was a little high, but it appears that all the chargers that come from SunThing are at 60v. Is it easy to open up those chargers and adjust them down to 58v, and is it even worth doing?

When I got the battery, I put some firm foam around the battery casing, and used a few (stick-on) floor tiles to build a protective casing for the battery before inserting it into my scooter. So hopefully that has protected it well from bumps and bruising

Like you said, when I will notice a large drop in capacity, I will likely order another battery from him again, as $315 for the battery including charger (slow boat 9 week shipping) is very inexpensive compared to some other higher quality cells. My usage is very light & minimal, and if I get 4-5 years use, I got my monies worth.

As for my Question 3, in regards to voltage drop under load, I presume those are normal numbers and indicate a typical SunThing pouch cell performance?

So, in summary, it looks like I will have my batteries die from old age, rather than exceeding discharge cycle specs.

Thanks again, IAN.

eTrike said:

Number seem typical for generic LiFePO4.

For comparison I've got a few year old generic 48V LiFePO4 pack that had a bum BMS, corrosion and 1-2 bad cells when I got it. The remaining 14 cells all had 95-98% of original capacity. The internal resistance (as seen in your voltage drop under load) is much higher than my 6-8 year old A123s that have been flogged without regard, so it isn't nearly as powerful, but this cheap 10AH pack is capable of running a 1000W setup. If the same holds true for your pack @15Ah, I would expect it is within its limits seeing only 25A peak.

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eTrike, If I understand correctly, you are using A123 cells which are amongst the top tier cells, I didn't think that the SunThing Lifepo4 pouches would produce the same specs.

One thing that I have learned here is that you really have to identify your usage parameters : current draw, distance, lifespan, cycles, cost, and cell composition (ex: fire/explosion), budget, etc....

For $315 for a 48v 15Ah Lifepo4 pack, that appears to be giving me the performance according to the manufactured specs, I am pleased to have gotten basically a Plug & Play battery pack that beats lead, nicad, nimh, and doesn't require me to become a battery engineer and charge them in a BBQ...

From what I see, a 25amp controller, with a 1000 km distance per summer season is really low on the requirements scale. I would like to ask Santa for 16x GBS Lifepo4 20Ah cells (the grey hard plastic casings) and build a 48v 20Ah battery, but it would be @ $700. Maybe Santa will think I have been good and surprise me... lol

Thanks again for replying, IAN

It IS a lot of sag. But that's fairly typical for the inexpensive lifepo4 pouches. And the use is a bit harsh, at least relative to a lighter rider on a bicycle, who pedals to help an amps worth.

Two solutions possible for your next battery,,

One would be a much higher c rate pack. But I'm not sure the problem really makes the pain in the ass and hazard of lipo worth it.

The other would be a bigger pack, 20 ah would make the c rate lower on all the cells, splitting the amps between 4 pouches instead of 3 like now. But really? to go 2k per charge? Honestly, for that length trip you could go back to lead.

By the 4th summer as internal resistance increases, that sag may get really bad, but as long as it doesn't hit the LVC of the controller or bms, you can keep on going with it.

I don't think the charger you have will be adjustable. The metal case ones usually are, but not the cheaper plastic. You could buy a very cheap 48v lithium charger, for 16s lifepo4, that is set to 58v. More typical is 15s with lifepo4 nowdays, and that would be too much undercharge, at 54.6v.

A more expensive charger, like from EM3ev, could be custom set to the voltages you prefer. three way switch, so one could be 59v, the other 56v, the third a half charge that is used when you will store the battery with the bms unplugged.

eTrike said:

Yep I mainly use A123 but was comparing a cheap pack I've got here. The A123s are able to tolerate abuse beyond normalcy but the cheaper stuff still lasts

As you say you have to weigh all the facets for yourself and you listed several good reasons to choose LiFe. The battery is the heart of system performance.

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I agree with you that a 15Ah pack could cost from @ $350 (shipping by slow boat) to a top quality one that would cost $1000-$1200 (with express shipping). We really have to analyse our ebike's needs and go according to our budget.

If money wasn't an issue, I would surely get a better quality battery....

dogman dan said:

It IS a lot of sag. But that's fairly typical for the inexpensive lifepo4 pouches. And the use is a bit harsh, at least relative to a lighter rider on a bicycle, who pedals to help an amps worth.

Two solutions possible for your next battery,,

One would be a much higher c rate pack. But I'm not sure the problem really makes the pain in the ass and hazard of lipo worth it.

The other would be a bigger pack, 20 ah would make the c rate lower on all the cells, splitting the amps between 4 pouches instead of 3 like now. But really? to go 2k per charge? Honestly, for that length trip you could go back to lead.

By the 4th summer as internal resistance increases, that sag may get really bad, but as long as it doesn't hit the LVC of the controller or bms, you can keep on going with it.

I don't think the charger you have will be adjustable. The metal case ones usually are, but not the cheaper plastic. You could buy a very cheap 48v lithium charger, for 16s lifepo4, that is set to 58v. More typical is 15s with lifepo4 nowdays, and that would be too much undercharge, at 54.6v.

A more expensive charger, like from EM3ev, could be custom set to the voltages you prefer. three way switch, so one could be 59v, the other 56v, the third a half charge that is used when you will store the battery with the bms unplugged.

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Thanks Dogman for the info. I don't see myself going with Lipo, as my main desire is to have something simple & very safe to use.

You bring up a few points:

1) Now about the charger charging to 60v, it appears that it is the norm, and not a huge problem in respect to any longterm damage or performance loss? I don't see myself spending $100 for a metal charger, especially since I have a few of the 3amp & 5amp SunThing chargers as spares.

2) Now about my short trips to the shop (1 km each way), am I better off to charge it every 3rd or 4th day, VERSUS putting it on the charger every day and topping it up?

3) Now you mention a 20Ah pack, I agree with this. However aren't these 48v 15Ah batteriess made up with 16s (thus 16 x 15Ah pouches)?

4) As per my original post (question #4), are my calculations correct. I have done @ 55 cycles in 2 years, so irregardless of battery cells, they will die of old-age versus dying of exceeding performance life?

Thanks for your replies, IAN.

Normally, I'd say charge daily, but since your trips are that short, It could result in a longer lifespan to charge only when you need to. Not weeks, but certainly you could get by with charging only one time a week. That's 10k of riding. Ideally, have the pack sit around 100% full as short a time as possible without being inconvenient. So one charge a week will be easier on it's lifespan, in your case. Charge Mondays, at work maybe?

IMO, your pack is going to eventually die of old age, 3-4 years being typical for that kind of lifepo4 pack. But your use is so light, maybe longer. I just haven't heard of sun thing, or similar ping packs lasting much longer than 4 years.

As for the size of the next pack, so far those type packs use 5 ah pouches. So you can get them in 10-15-20 ah and so on. Possibly sun thing only offers one size though.

dogman dan said:

Normally, I'd say charge daily, but since your trips are that short, It could result in a longer lifespan to charge only when you need to. Not weeks, but certainly you could get by with charging only one time a week. That's 10k of riding. Ideally, have the pack sit around 100% full as short a time as possible without being inconvenient. So one charge a week will be easier on it's lifespan, in your case. Charge Mondays, at work maybe?

IMO, your pack is going to eventually die of old age, 3-4 years being typical for that kind of lifepo4 pack. But your use is so light, maybe longer. I just haven't heard of sun thing, or similar ping packs lasting much longer than 4 years.

As for the size of the next pack, so far those type packs use 5 ah pouches. So you can get them in 10-15-20 ah and so on. Possibly sun thing only offers one size though.

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Dogman, I think I will follow your suggestion about charging the pack at the end of the week, since I may have only used it so lightly. I guess the daily charging is coming from my SLA days...

Like you said, my LifePo4 pack will die from old-age rather than cycles, so even if I get 4-5 years out of it, I will definitely get another similar pack. It's serving my needs well and virtually Plug & Play.

SunThing sells 15, 20, 25, 30Ah versions, so from what you tell me it is 3p16s (3 x 5Ah packs in parallel, and 16 of those in series)? Either way, I find that I got lucky, and it's an excellent value (considering).

Thanks again for taking the time to reply to my post, IAN.

PS: How is that battery pack you got from (I think ) AliExpress recently going...?

imorton said:

Hi Guys & Girls, I have a scooter and had SLA's and when it was time to change them, I bought a 48v 15Ah LifePo4 16s battery from Sun Thing @ 2 years ago. I tested it at the beginning and it produced @ 14.5 Ah and seems to balance fairly quickly. My average trips are @ 6-10 kms, and have done a few 40km trips. I also do @ 100 trips a summer to back & forth to work that is only 2 kms (1km each way) and I end up charging the battery at the shop. I have done @ 2000 kms with the scooter with the 48v 15Ah LifePo4.

I just wanted to ask a few questions...

1) It came with a bulky 5amp charger (it also charges to 59.9v), but I tend to always use my spare 3amp 48v charger that appears to charge up to 59.9v and stays there while it balances the pack. Is the 59.9v a little high, and is it damaging the cells?

2) When I take the battery off the charger, the voltage drops to 55 or 56v, and if I ride the scooter a little, it will stabilize at 53.24v (I presume this is good since 3.3v x16 = 53.28v)...?

3) I am curious what is a normal voltage drop as when I ride and draw .5C (7-8amps) the voltmeter says @ 51v, and when I draw @ 1C (15-16 amps) the voltage drops to 49v. If I hammer the throttle and draw 25amps, the voltage drops to @ 47v. I presume that these are normal/healthy numbers for a 15Ah LifePo4 battery?

4) I am a big guy (250lbs) and ride at @ 22km/h (appears to be a quiet/efficient speed) and have figured out that the scooter consumes .4Ah per km, or 20Whr/km. If I did @ 2000 kms on the scooter, at 20Whrs/km, I assume I consumed 40k watt hours. So if my calculations are correct, I have only used @ 55 cycles from it, and the battery should do @ 1000 cycles...?

5) So it appears that I will never wear out the battery from exceeding it's cycle life specs, but how long does a LifePo4 used this way last.... 3,5,7,9 years?

You guys are simply amazing with all your knowledge, so thanks in advance for any replies and info that you can share.

IAN

Click to expand...

well hi there OP

as one noob to another ...


i confess i bought ~same 5 months ago, & have been too slack to install it as an upgrade

same brand & probably same vendor

~US$400~ delivered here in oz - 8 weeks also

mine is the 36v 15ah w/ 3ah charger

so i am delighted to read the results you are getting from yours.

frankly, i think they are awesome results. if u r pulling 25 amps at ~48v thats 1.66c, or ~1200 watts, in bursts at least.

Gosh, if, as above, i can get 1.66c on my 36v one, thats 600w for my 350w bike.Plenty i think. At full 350w, i only draw .66c i think.

(i wish i could have got 48v, but its a nice factory bike i dont wanna mess with, so 36v it is)

So, NB, its not a big deal if they lose a little oomph over the years, hang the expense.

for you esp., as a big guy, any weight penalty of lfp is a trifle vs gvm of u & the scooter.

i heard lfp degradation with age is mostly in c-rate rather than capacity.

Why do all say they are crap. I dont get it?

did u just get a spare charger w/ the purchase? If so, and both agree on charging voltage, then there would seem to be no mistake about the makers intended charge voltage.

i dont think it was said in posts? NB. each lfp cell is 3.2v or even 3.3v officially, so 16x 3.3v is 52.8v, not 48v. Its a substantial voltage bonus over other "48v" packs, and it is of course normal and necessary to charge at higher voltages than the pack.In short, dont worry about it. sounds about right. The makers engineers presumably dont want problems either. Their guess is better than yours. leave the charger be.

So it sure seems, as u say, it will last forever. The trick is dont fry it, ie, over charge/discharge is probably the main cause of pouch swelling, which seems the main cause of pouch failure. yep, u need to relax a bit with charging. why bother AND invite trouble?

i like that a noob has a fair chance of replacing a failed cell - its only 12/16 cells in series - simple vs 18650 paks.

keep it charged in its comfort zone of say 30% to 80% (most batteries dont like being stored full or very low for long), and an occasional full charge w/ balance sounds good.

Using the slower charger sounds right.

i dont think its a case of the scooter being too good for the pak, its the other way around. A 10ah like this would do

btw folks, my pak, as above, is 5.5kg.

How often do you ride in the winter ? Or does the beast go in a winter cave for the hibernation ?