Upgrading from 48 to 52 volt battery

[Garyjk]

I am new here, is it possible to go from 48 to 52 volt battery?

Ebike is made by Igo out of Montreal Canada Discovery Bonaventure.
500 watt motor.

My controller on the bike is made by Accelerated Systems Inc. model BAC555 I think max volts are 60.
When the 52 volt battery is fully charge to 58.8, with only 1.2 volts to the max…is that going to be to close to the top end of my max until the volts start dropping.

Just hoping somebody upgrade their Igo bike up to 52 volts battery and the controller can handle the extra volts.
TIA

 

[fechter]

That model of controller can handle a 52v battery no problem. But there may be something in the programming that needs to be changed. If it's made for a 48v battery, the low voltage cutoff may be a bit lower than you want for 52v. The pack has it's own BMS to prevent over discharging the pack to the point of damaging it, so it should still be OK. It's generally bad to run the pack to cutoff anyway.

 

[ykuga]

Hi Fechter and others,
My question is different from that of OP. Since we are talking about going from 48 to 52V, here is my question. Many of us have 48V setup with 48V batteries. I have some. I was interested in using 52V setup but purchasing a new 52V battery is expensive. So I created 52V battery using 48V and 4.2V 1S in series. It works very well. When I posted it long time ago in ES, I got a negative response but I want to know the opinion of other experts.

My setup
Two 48V 10Ah 13S3P with BMS and fuse in parallel. Effectively this is 13S6P (20 Ah).
4.2V 44Ah 1S20P using 20 2200mAh cells. No BMS but a 40A fuse is attached.
48V and 4.2V are connected in series to create effective 52V 20 Ah battery.
The Ah of 4.2V is much higher than that of 48V. The reason is 4.2V battery does not have a BMS and I wanted to make sure it does not go below 3.2V before 48V battery shut down. Usually I use up to 50% of the 52V battery capacity. Therefore, 4.2V battery never goes below 3.6V.
My only problem is charging 4.2V battery. I use a 4.2V CC CV power supply but it has only 3 A max output. It takes a long time to charge 4.2V battery up to the capacity. Since there is no BMS in 4.2V battery, I also monitor the charging voltage carefully.

My 52V setup has no issue driving BBSHD with up to 30A.

Do you see any issues or potential problems with my battery setup?

 

[Garyjk]

Thanks Fechter but in my display I can set it to 48 volts or 52 volts and when I set my display to 52 volts there is less bars on my display than when I set it to 48 volts. So I think I will see my cut of on my display as the battery goes down.

My concern is the controller going to handle the few extra volts.

Thanks
Gary

 

[Chalo]

Since there is no BMS in 4.2V battery, I also monitor the charging voltage carefully.

You could put a low voltage buzzer on the single cell.

Seems like it would be easier, cheaper, better to accept what you get from 48V, though.

 

[Garyjk]

Anybody know how if this controller can take 52 volt battery.

Controller Model # BAC555
made by Accelerated Systems Inc.

TIA

 

[fechter]

From ASI:

The supply voltage cannot exceed 60 volts. Typical battery chargers tend to charge at voltage
much greater than the nominal battery voltage and, as such, when the charging is complete a
certain amount of surface is left which typically increases the battery’s voltage by approximately 10
to 15% above nominal. The excess surface charge is, however, quickly dissipated when the system
is under load.

So if you charge to 58.8v, you will still be under the 60v maximum. And as they point out, this voltage will drop quickly as soon as you run the motor.

For the single cell in series with a 48v pack, no reason it won't work. It's just a pain to charge separately and if you forgot, it could get easily damaged.

 

[Garyjk]

Thanks Fechter

Just one last question Fechter or others…

I decided I am going with 52 Volt 20ah but which BMS 40A or 50A?

Or should I match my current in my controller which is 50A and max 75A..

What happens if I go with 40A less power or something?

TIA

Gary

 

[fechter]

The BMS should be rated a little higher than the maximum controller current. You don't want the BMS to trip under normal operation. The BMS could be rated a lot higher than the controller max current and still do it's job if something shorts.

If the BMS is rated too low, it will trip and cut off the power when you try to accelerate hard. This always seems to happen at the worst possible time too, like when you're trying to get out of the way of a speeding truck.

 

[amberwolf]

Also, note that just because a BMS is rated for a certain current, doesn't mean it actually senses current and controls it's output to protect against overcurrent. It's rating could simply be the rating of the FETs onboard, and *that* rating will depend on the ability of the board to shed heat--if it's enclosed within heatshrink inside a battery case, that ability is hampered, and will reduce the current the board can handle before overheating can cause FET failure.

If the BMS has current-sensing shunts on board, then it *can* sense current and do something about it. It's still possible that the designers didn't include the function in the control hardware or software, but it's more likely that they would, if they already spent the money on the sensing hardware.

But if there is no current-sensing shunt, then it's not very likely the board can sense current, and so probably has no overcurrent protection. (it is possible to sense current via other methods, such as based on voltage drop across the FETs, but that method only works if they always use the same FET model and the same number in parallel, and that the FETs don't vary Ri between batches. Other methods require other hardware that is more expensive than shunts, and so less likely to be used on cheap BMSs).

Most of the BMSs Iv'e seen do have current-sensing shunts on them. But most of them also have balancing shunts on them...however, these days, there are cheap BMSs that do not have balancers, and so there may also be some that skip other "essential" BMS functions like current sensing/protection. :/

 

[amberwolf]

I decided I am going with 52 Volt 20ah but which BMS 40A or 50A?

Or should I match my current in my controller which is 50A and max 75A..

What happens if I go with 40A less power or something?

You need a battery (both cells *and* BMS) that is designed to continously handle the continuous current you will actually use, and that can handle the max peak current you will actuallly use for the amount of time you will use it.

If you use a battery whose parts can't handle those, then it depends on what the battery's design and response is as to what will happen to your system during overcurrent events.

If the battery's cells are designed to handle the current, but the BMS is not, *and* the BMS is designed to cut power on overcurrent, then everytime you exceed it's current limit it will shut off all power to your bike. What happens at that point depends on what you are doing; if you're in traffic trying to get out of someone's way, you might get squished.

If the battery's cells are designed to handle the current, but the BMS is not, *and* the BMS is *not* designed to cut power on overcurrent, but instead is just a FET rating, then everytime you exceed it's current limit it will overheat the FETs. If the heat builds up enough to cause FET failure, they'll fail, which usually means shorted (stuck on). If the heat that now builds up (because their resistance in this state is higher than normal, so heat is greater for a given current) is not enough to desolder them or cause further failure that opens the circuit, and not enough to cause cell damage for any that are next to the BMS, then the primary result (besides heat generation inside the BMS, and voltage drop to the controller), will be that the BMS now can no longer ever protect the pack against overdischarge, becuase it can no longer turn off the output FETs. (if the input (charge) FETs happened to also heat enough to be damaged into a stuck-on state at the same time, then it also can no longer protect against overcharge).

The above failure is a "silent" failure, externally, unless it heats enough to create a smell you'll notice and check out, or enough of a voltage drop to cause you to investigate and find the FET failure. So at this point you're now essentially using a BMSless unprotected pack of cells with a space heater attached to them.


There are other situations with their own consequences I didn't type out.

 

[Garyjk]

Ok thank you

So I should go with min of BMS 50.

52 volt 20ah BMS50 battery to match my current in my BAC555 controller.

I assume the batteries on Amazon are corrected made.

What brand do you recommend?

 

[amberwolf]

So I should go with min of BMS 50.
52 volt 20ah BMS50 battery to match my current in my BAC555 controller.

If the controller has a maximum current of 50A that it will ever draw, then yes.
Otherwise, you need a BMS that can handle the maximum current the system will ever draw. Preferably one that can handle some percentage (20-25%) more, so there is margin for safety and to keep from hammering it so that it lasts longer and is less likely to fail from a momentary system overload.

If you get a battery incapable of the current draw of the controller, you'd then need to reprogram the controller current limit to match what the battery could handle, or less, to get that safety margin--this will then reduce performance of your system.

Keep in mind that even if the BMS can handle the current, if the cells can't, the voltage sag during those loads will mean less watts to the wheel (and more wasted as heat in the cells), so the system won't perform as well as it should.

I assume the batteries on Amazon are corrected made.

I'd personally rather assume that any battery on any website is incorrectly made junk unless and until proven otherwise. It's a lot safer, and unfortunately more likely to be correct.

What brand do you recommend?

Nothing on Amazon I can think of. (there might be good ones, but I haven't seen one I know for sure is--Amazon, like Ebay and any other marketplace, is full of fake garbage).

EM3EV, Grin Tech, maybe LunaCycle (they've improved since my pack from them was made), and probably some others posted about in various "what's a good battery brand" type threads, but whose names I cannot remember right now, would be ones I would trust.

Some places that might be trusted (like UPP) have many options, and the cheaper options may not have everything you need to operate your system. You'd need to specify each option and requirement you have, including making sure the BMS they use has a balancing function built in (they don't all), or else you might not get a safely usable pack.

Additionally, it is very unfortunate, but many sellers of batteries (well, everything, really) do not know what they sell, and don't make them themselves. They generally don't understand how they're rated, or how they work, and even if they wanted to (they likely don't) they couldn't provide usefully correct information about them. Many of the ads for them don't even have info on the pack actually for sale, just generic info about the *series* of packs they sell, or a mix of jumbled info on several different kinds. Some are outright lies, some are just mistakes. But you can't know if any of it is right until you get the pack and test it, and probably actually disassemble it to see how well it is made.

Some manufacturers of batteries don't even use new, tested parts to build them with; some actually use recycled garbage cells from scrapped batteries, that may not even be the same kind of cells (brand, model, etc) for the whole pack. Some of them actually make "fake" packs, lying (often in the extreme!) about what they manufacture. The sellers don't know this is the case, or what means when they get packs from these places.... Some sellers themselves flat out lie about what they sell, knowing that it isn't what they say it is.

So...be careful out there.

I highly recommend that you post a link to whatever you are considering buying before you click the buy button, so that someone experienced with this gigantic mess can help you make sure it is really what you need first.

 

[E-HP]

Nothing on Amazon I can think of. (there might be good ones, but I haven't seen one I know for sure is--Amazon, like Ebay and any other marketplace, is full of fake garbage).

Some places that might be trusted (like UPP) have many options, and the cheaper options may not have everything you need to operate your system. You'd need to specify each option and requirement you have, including making sure the BMS they use has a balancing function built in (they don't all), or else you might not get a safely usable pack.

Amazon carries UPP packs, and the more expensive ones list the cells used (e.g. LG). Unfortunately, their prices are a good deal higher than buying them from ebay. 52V 26.5Ah using LG cells is $738. My UPP pack from ebay, with Samsung 35E 52V 28Ah was $633 delivered. The generic cell UPP packs on Amazon are also more inline with ebay prices. My generic cell 52V 20Ah UPP pack was $355 and on Amazon is $373, actually a decent deal given my generic pack was purchased several years ago.

 

[fechter]

If the controller is 75A max, you want at least a 80A BMS. 100A would be better.