52v battery at 80% max charge as 48v alternative?

[unclejemima]

I’ve been running my 48v battery for years. Right now it’s a 14ah 48v 13S battery with 20 amp bms.

I use the bike mainly for commuting, 10km each way.

I’m running a bbs-02 currently but would like to upgrade to a bbs-hd later this year.

I was hoping to get a new higher rated bms battery so I can run 25 amp on my bbs02 and or bbs-hd later.

I’ve got my eye on a new 14S 21ah 52v 40amp bms unit. A big upgrade in ah and high rated bms.

Because I have a habit of plugging in each time I park my bike, I was thinking that instead of getting another 13S battery, I could run the 14S and the battery seller said they could program the bms to max charge at 80%…there by staying in the sweet spot of battery longevity with my habit of always plugging my battery in.

With now 52v at 80%, and larger 21ah battery capacity…it should run similar power and range to my 48v but with a much longer lasting battery.

Is there any downside to my logic of getting the 52v and running it max 80%?

Are there any chargers that I can regulate the charge to max 80%…with the option to go to 100% if a long ride is in the cards? Instead of having to hard program the BMS?

Thanks all!

 

[harrisonpatm]

A 13s charger should have a max charging voltage of no more than 54.6v (13s x 4.2). If you use the same charger on a 14s battery, assuming the cells are well balanced, each cell should top off at about 3.9v (54.6v / 14s). There's nothing inherently wrong with doing that, you shouldn't need to reprogram the BMS or anything, and you are correct that charging it to 80% or so will increase its longevity.

You just need to be okay with carrying around the weight and bulk of a battery whose capacity you won't be making full use of. Perhaps a better option for you would be to stick with 13s with your new battery, but find one that is higher rated for both capacity and discharge. That way you'd still be taking advantage of the full voltage range of your battery. Does that make sense?

For example, you said you were considering 14s 21ah, or about 294wh. For the same wh rating (meaning, same number of cells), you could potentially get a 13s 23ah. Plus, having even more cells in parallel than your considered 14s battery means the cells will experience less discharge stress, which will have your desired result of longer battery life. If you still want to reduce max charge voltage, you can still do that with a 13s.

Up to you

 

[2old]

Luna (and many others probably) has a 52V charger that has 80%, 90% and 100% capability.

 

[999zip999]

Will the 52v battery balance at 80% .
Will the batteries BMS be able to balance the cells with it's circuitry . I don't know if it's set to balance at lower volt.

 

[Jeff23spl]

most low cost bms only balance when cells are fully charged or close to be. You would need a bms that can balance at lower voltage. an active balancer bms is doing that but good chance to be a custom built or you would have to replace it yourself....My JK can be configured as you wish but i dont know for others.

80% voltage isn't directly 80% capacity you may have to do some tests. I would rather target 90-95% to still avoid overvoltage and use a low amp charger. Then, the extra Ah should remain in the pack each time you recharge it so, battery won't discharge as much as it was for the same use before and this kind of ''half use'' will help reduce the wear also.

For the 25a vs 20a, is it something you can set in your ebike controller? Can you configure the max amperage limit ? If not, having a BMS with higher max amp won't help much. It is like replacing a 20a fuse by a 25a....The extra capacity should reduce voltage sag a bit and this may add some fraction of volts to the load but this alone, won't be night and days...

 

[amberwolf]

I was hoping to get a new higher rated bms battery so I can run 25 amp on my bbs02 and or bbs-hd later.

I’ve got my eye on a new 14S 21ah 52v 40amp bms unit. A big upgrade in ah and high rated bms.

If your cells can handle that bigger BMS, sure. Remember that a BMS doesn't have Ah, as that's just the capacity of the cells, so no matter what the BMS says on it, it won't increase the Ah of the cells you connect it to.

The BMS needs to be rated no higher on output or input than the cells can handle, so if you are replacing the BMS on an existing pack, it's safer not to go any higher than the original one. (less if the pack is old as it's cells have aged and are less capable than they were).

If you are referring to buying a whole new battery, with a new BMS, then the above shouldn't matter, if you are buying a quality pack built of parts actually capable of what the ad says. (many are not, especially if they're cheap).

Because I have a habit of plugging in each time I park my bike, I was thinking that instead of getting another 13S battery, I could run the 14S and the battery seller said they could program the bms to max charge at 80%…there by staying in the sweet spot of battery longevity with my habit of always plugging my battery in.

With now 52v at 80%, and larger 21ah battery capacity…it should run similar power and range to my 48v but with a much longer lasting battery.

Available power (watts) wouldn't change from higher capacity, other than potentially less voltage sag, assuming your new cells are at least as capable as your old ones.


Note that if you have the BMS factory/seller-programmed to not allow charge beyond 80%, you won't have the option to do 100% later, unless you get a BT-programmable BMS that uses a phone/etc app to change settings (like ANT+, JBD, etc). So, that's an option, too.

But, you might have them go ahead and program it's balancing to start at the cell voltage equivalent to 80%, so that it will still balance them regardless of charge voltage. Just make sure that they aren't being drained down to that cell voltage, only that they are kept equal at whatever the final voltage is, if the BMS is smart enough to be able to do that (vs having a fixed specific final balanced voltage)

Is there any downside to my logic of getting the 52v and running it max 80%?

Are there any chargers that I can regulate the charge to max 80%…with the option to go to 100% if a long ride is in the cards? Instead of having to hard program the BMS?

If the cells are well-matched and don't need to be balanced, then you can use any charger that has a max voltage of whatever you want to charge the pack to. So, around 54-55v for a 13s-capable motor system. (under whatever that system's HVC is).

Then just use the charger that comes with the 14s pack to fully cahrge the pack whenever that's needed.


If you only want to use one charger, then there are cahrgers with switches for 80 / 100 %, or a voltage adjustment knob, etc. There is also the Cycle Satiator from ebikes.ca that you can setup with preset profiles for different charge rates and voltages; it's worth the money if you have a lot of different packs of different voltages or you need a vibration-proof and weatherproof bike/vehicle-mounted charger.

 

[E-HP]

I was thinking that instead of getting another 13S battery, I could run the 14S and the battery seller said they could program the bms to max charge at 80%…there by staying in the sweet spot of battery longevity with my habit of always plugging my battery in.

80% is a pretty low sweet spot. I’m assuming the Seller is saying setting the max to 54.6v, not a percentage, but it would be a good clarification to know what he means by that. If you’re moving to the BBSHD later, I see no reason to do this, especially if you get a pack with good matched name brand cells. IF the Seller clarifies that the 54.6v setting starts balancing at that voltage, that might be a consideration, if it’s built with generic cells, otherwise just charging with a 48v nominal charger should be fine for a good while.

 

[999zip999]

Different chemistries have different sweet spots lifepo4 is charged to 3.6 - 3.65v for the BMS to balance. The real top of usable charge or sweet spot is 3.45v or are where it starts to level out. There's many different chemistries that have many different personalities. So what is the sweet spot of the cell you choose.

 

[E-HP]

Luna (and many others probably) has a 52V charger that has 80%, 90% and 100% capability.

Seems like most folks define 100% as 4.2v/cell for lithium ion, but what does Luna define as 0%. Most people don’t have the equipment to determine state of charge, and chargers appear to use voltage as a proxy. Is there a voltage the represents 0% that’s standardized for setting and comparing these percentages?

 

[2old]

I looked at a SOC vs voltage chart for 52V systems and at 80% and 90% the Luna charger was close (AIR within a couple of tenths which is probably the extent of accuracy of the voltmeter). 100% was 58.6V. Everything was close enough.

 

[999zip999]

E-HP what is zero ?
So what is zero for lifepo4 ?
What is zero for the different lithium chemistries ?
What is a good list of the different chemistries ?
As some are 3.4v to 3.6v or 3.7v normal?

 

[E-HP]

E-HP what is zero ?
So what is zero for lifepo4 ?
What is zero for the different lithium chemistries ?
What is a good list of the different chemistries ?
As some are 3.4v to 3.6v or 3.7v normal?

That’s the point. Even with the same chemistry, does 90% mean the same to Luna as it does to Grin, or anyone else that says they are charging to 90%? What is Your definition of 90%? Pick whatever chemistry you want.