Need a 48v battery, have a few questions

[Chris456345234]

I have have 500 watt motor (says Shengyi hybrid on it) and some unknown controller. My current pack is dead after storage in the winter (was a 'free' rebuild, I opened it and it looks like they threw in 7 of some sort of polymer batteries). Want to buy a new battery, thinking of a 13S5P Samsung 35E from em3ev with Grin Satiator and setting it up to charge to 80% as the default profile (good choice?).

https://em3ev.com/shop/em3ev-48v-13s5p-jumbo-shark-ebike-battery/

My goal: Buy something good that will outlast my current ebike, my next motor will probably be 750w or 1000w hub motor.

Few questions:
1# With only 13 batteries in series doesn't that mean the moment the battery hits 3.7v ill be under the 48v my motor expects? At what point should I expect my controller to send a 'low voltage' error (aka shutoff)? <- I know this is probably hard to answer without knowing exact motor/controller I have.

2# Is the Grin Satiator worth it, or should I just get a more basic charger that can be set to 80%? I figure with the Satiator I can setup exact profiles (max voltage and charge amperage) thereby extending the life of the batteries and use it on future battery packs. I guess the main question seems to becomes 'will the satiator last long enough to pay for itself'?

3# I might upgrade to a 750w/1000w motor in the future and it seems to be the 35e batteries should be good enough. Is this math right: 1000w divided by 48v = 20.8 amps, but this pack is 5p, so 48v/5p=4.16amps per cell. Does that mean I should still be only using about 50% of this batteries continuous CDR rating even with a 1000w motor (thereby extending the life even more)?

4# Lets say I want to store my batteries at 3.7v for the winter, can't I do 3.7v*13 = 48.1v, then just discharge my battery down to 48.1 and hope the BMS more or less will have all the cells at the same 3.7 voltage? And Ive never tried this, but can't I attach two wires to the output of the battery to an incandescent light bulb and drain the battery that way instead?

 

[amberwolf]

Some thoughts:

I opened it and it looks like they threw in 7 of some sort of polymer batteries).

If there were only 7 cells (presumably in 7s1p configuration), that makes a "24v" pack, presuming a 3.7v-average chemistry. (if it's some other chemistry, it would be even less voltage).

So...you'll almost certainly need a new controller as well, as few generic controllers can run from 24v to 48v; a number of things may not work with that great a difference:
--LVC won't cut off to protect the battery, so you're dependent on the battery's BMS, which can be hard on it.
--HVC (controller may not operate above 28-30v; possibly 42v if it's a 24v-36v controller)
--LVPS that runs the controller brain may burn up; often uses a resistive voltage dropper from pack voltage to something the 7812 (or lm317) can take and convert to 12v for later stages, and this has a narrow operating range; exceeding it overheats the resistors, and can burn them out (or overheat nearby components, or the PCB, and burn or damage them, too). This can usually be overcome by changing the resistors.
--primary capacitors and FETs may not be rated higher than 35v (or 50v for a 36v controller), and can blow up used at voltages above that.


(some newer units use SMPS instead; these usualy have wider input voltage range, have componets rated for higher voltage in general, and are usually either jumpered or set in software for their LVC/HVC, eliminating the above problems)

Want to buy a new battery, thinking of a 13S5P Samsung 35E from em3ev with Grin Satiator and setting it up to charge to 80% as the default profile (good choice?).

As long as you're not usualy drawing high currents from it that might unbalance the battery, then until it begins to age it'll probably only need the 80% charge. But to balance it you'll have to charge it to full, whcih youc an do periodically as needed and charge oly to 80% the rest of the time.

If te pack has access to teh balance connector from outside you can manually check it periodically and then just full charge whenever tha'ts rquired.

1# With only 13 batteries in series doesn't that mean the moment the battery hits 3.7v ill be under the 48v my motor expects? At what point should I expect my controller to send a 'low voltage' error (aka shutoff)? <- I know this is probably hard to answer without knowing exact motor/controller I have.

As you say, can't really answer that one. Depends on the controller's LVC.

But for the contgroler you have now, if it worked ona 7s battery, it isn't going to be affected by any voltage a 48v battery would ever be at and remain functional / safe to use.

2# Is the Grin Satiator worth it, or should I just get a more basic charger that can be set to 80%? I figure with the Satiator I can setup exact profiles (max voltage and charge amperage) thereby extending the life of the batteries and use it on future battery packs. I guess the main question seems to becomes 'will the satiator last long enough to pay for itself'?

Probably. Mine's seen a lot of physical abuse, including a St Bernard carrying it around sans cables as if it were her toy. So far the only stuff that broke from any of that was the external part of the plastic connector for the output, and the ring got lost that holds it in place. (might've been eaten) Mostly I use mine to charge my 4s lighting pack at the Satiator's 8A max, but before I installed a Meanwell LED PSU (donated to me) on the trike itself for higher current charging, I used it every day for charging the main traction pack, and I've got profiles in it for other packs I dont' use a lot these days.

The main attraction of the Satiator is for those with mulitple packs of different votlages, so they don't have to keep a bunch fo chargers around. (which is less of an issue for me ATM, but was one big reason I liked it wehn I got it)

The other main point is that it's environementally sealed, so youc an mount it on the bike or vehilce, and leave it connected to the battery all the time (it self-disconnects internally), so you can just plug the bike/vehcle into the wall and let it charge, with whatever default profile you setup in it. (which is the use I have for it on my trike)

1000w divided by 48v = 20.8 amps, but this pack is 5p, so 48v/5p=4.16amps per cell.

That would be 20.8 amps / 5p, not 48v / 5p, but you do have the right answer in amps.

Does that mean I should still be only using about 50% of this batteries continuous CDR rating even with a 1000w motor (thereby extending the life even more)?

Generally you get longer life when keeping discharge and charge rates low, relative ot the cell capabilities.

4# Lets say I want to store my batteries at 3.7v for the winter, can't I do 3.7v*13 = 48.1v, then just discharge my battery down to 48.1 and hope the BMS more or less will have all the cells at the same 3.7 voltage?

The BMS will not do anything about cell voltage in this operation.

The only time a common BMS will balance cells is at the top of full charge, because they just drain high cells taht are above the HVC limit (uusally 4.2v or thereabouts for common Li cells).

So if the cells are already out of balance at the time you drain it for storage, they'll be out of balance (possibly further) once down to the storage level.

And Ive never tried this, but can't I attach two wires to the output of the battery to an incandescent light bulb and drain the battery that way instead?

Yes...but when you do store the battery at lower voltage, you should either disconnect the BMS from it (assuming it doesnt' have a switch; most don't) to prevent it draining the pack over winter, or periodically (weekly to monthly) check it to be sure it isn't draining cells too far, especially if it runs on only a few cells; it can severely unbalance those.

 

[Chris456345234]

Thanks for the reply. Think my latest plan is to get the 52v pack with the Satiator. Will probably setup my main profile to charge to 3.8v*14s=53.2v while also having a 3.9 and 4.0 profile for 54.6v and 56v for a few rare longer trips per year. In theory that should give me lots of power and put in the 'very safe' +200 battery cycle range.

If there were only 7 cells (presumably in 7s1p configuration), that makes a "24v" pack, presuming a 3.7v-average chemistry. (if it's some other chemistry, it would be even less voltage).

I took a closer look (it's still glued in its protective metal case, tho I took out some of the padding which gave me a better look) It looks like 7x2 cells (setup in 14s I guess). Its definitely a '48v' battery as the multi meter would give me ~+54v on full charge.

As long as you're not usualy drawing high currents from it that might unbalance the battery, then until it begins to age it'll probably only need the 80% charge. But to balance it you'll have to charge it to full, whcih youc an do periodically as needed and charge oly to 80% the rest of the time.

I was thinking of doing something like that for good measure, tho that being said they list one of the features of their BMS as being able to balance anytime its charging or when the battery is over 50% charged.

The main attraction of the Satiator is for those with mulitple packs of different votlages, so they don't have to keep a bunch fo chargers around. (which is less of an issue for me ATM, but was one big reason I liked it wehn I got it)

My current battery 'slides' onto the back of my bike and I need to connect an Anderson connection each time. Since it has that cheap metal lock I basically never leave my bike without my battery (unless sub 2m run into store). So I like the idea of a quicker disconnect battery (that will also be 2-3 lbs lighter). So I try to leave as little valuable as possible attached to my bike.

Generally you get longer life when keeping discharge and charge rates low, relative ot the cell capabilities.

I read that, but I don't know how low to go. As it stands it means id be doing 25% max (2amp), which sounds low in paper, and only do 50% if I eventually end up getting a 1000w.

 

[kcuf]

cells survive longer avoid draining lower soc

80% 90% soc dangerous no balancing

use packs with recent 100% charge

avoid sitting unused full soc

don’t over complicate

listen to experience

 

[amberwolf]

I was thinking of doing something like that for good measure, tho that being said they list one of the features of their BMS as being able to balance anytime its charging or when the battery is over 50% charged.

These days, that's still an unusual feature; most still only balance at top of charge. So it's good that it can. I would suspect it is a charge-shuffling type of balancer, rather than the more common resistive-drain type. Might be slower at balancing but it is more efficient at it, and does a more thorough job if it starts halfway up instead of only at the top.

My current battery 'slides' onto the back of my bike and I need to connect an Anderson connection each time. Since it has that cheap metal lock I basically never leave my bike without my battery (unless sub 2m run into store). So I like the idea of a quicker disconnect battery (that will also be 2-3 lbs lighter). So I try to leave as little valuable as possible attached to my bike.

FWIW, that doesn't really have anything to do with what charger you use for it.

But it is often good practice in high-loss areas. I've thankfully not had problems in a long time, since I started building completely custom bikes like Crazybike2 and especially the SB Cruiser trike. But I used to have all sorts of theft issues with regular bikes; never lost a whole bike but would be missing lights, tiedowns, etc., on a too-frequent basis. I kept my bikes looking like junkpiles, which made them less of a direct target, but it didn't stop stuff taht wasn't bolted on from going missing.

(that is part of why SB Cruiser has the enclosed locking cargo pod and underseat cargobox--they won't stop someone that really wants to break in, but they'll make it obvious that's what they're doing, which may deter them under many circumstances if people are around...and then I park in high traffic areas visible from everywhere possible).

 

[999zip999]

How about a pic or link of your setup. No guessing.

 

[999zip999]

Em3ev is a great battery maker good support. They will support you. At your amp demande should last many years . I would get the 3 stage em3ev charger or if money permits get a grin model and always charge your battery once a month use it or not. Some of the new batteries Bluetooth BMS so you can monitor. Really I feel just use every day if you ask me.

 

[Chris456345234]

View attachment 1

Here is picture of bike and the battery with the back cover open.