60 volt vs 72 volt

E-HP · Jul 18, 2019

I'm getting ready for a transition from my 52 volt battery pack to either 60 or 72. Ideally I'd like to start with a controller upgrade that is flexible enough to run at all three voltage levels, but soon after that, I'll need to solve the voltage/battery part.

My original plan was just to go to 60 volts, since I'm really happy with my bike's performance when the battery is fully charged and for the first 10 miles of battery. After that, the sag makes it less peppy on acceleration or hill climbing. I'm hoping that with the added cells and voltage, the bike will perform at that level longer. My specific question is what are the downsides of going all the way to 72 volts instead of 60 volts per my original plan? I like the bike's manners right now, and I ride mostly with PAS and use throttle when I want to accelerate or riding up a steep incline.

In order to use my current pack, I'm going to add a 6S5P pack to my rack to run in series (if I go to 72 volts), when I want the extra performance, and I can upgrade to a 72 volt single pack later. I think the weight of the small pack won't be too much of a factor, balance-wise.

EDIT: sorry, current setup is 1000W generic rear hub, 52 volts 20 ah triangle pack with cheap Chinese cells, 36/48 volt sine wave controller, 40 amp max.

billvon · Jul 18, 2019

E-HP said:
My specific question is what are the downsides of going all the way to 72 volts instead of 60 volts per my original plan?

Assuming everything can handle both voltages, and assuming that phase current is the limiting factor on power, the only difference will be a higher top speed at 72 volts, but slightly less efficiency.

devo1223 · Jul 18, 2019

I progressed in a similar way. Upping the voltage is the easiest way to increase power(and top speed). Went to 72v until I melted my motor, bought bigger motor, then bigger battery, better frame,etc. So yeah go to 72v and have fun.....

thundercamel · Jul 18, 2019

E-HP said:
My original plan was just to go to 60 volts, since I'm really happy with my bike's performance when the battery is fully charged and for the first 10 miles of battery. After that, the sag makes it less peppy on acceleration or hill climbing.

I'd say you should first confirm whether it's less peppy due to an overall lower voltage, or if the controller is getting close to it's low voltage cutoff point, and is starting to limit current draw.

This screenshot is from the SmartBMS on my wife's bike, which originally had some significant voltage sag from the Vruzend 3.5 amp caps being pushed past their limit. You can see the linear nature of the current limiting on the green line, as the voltage under load got lower. Once I rebuilt the pack with nickel strips spot welded, the voltage sag was greatly reduced, and that current limiting doesn't kick in until the pack is almost empty. The bike now feels like it has the same amount of power from 100% through 15% instead of the previous 100% through 40%.

I don't suppose you have any way to monitor current draw? What I'm trying to get at, is it's possible that a 52 volt battery that didn't sag much could produce your desired power level longer.

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E-HP · Jul 18, 2019

devo1223 said:
I progressed in a similar way. Upping the voltage is the easiest way to increase power(and top speed). Went to 72v until I melted my motor, bought bigger motor, then bigger battery, better frame,etc. So yeah go to 72v and have fun.....

Well if I have to melt a motor I guess that will just accelerate my next planned motor upgrade

. My motor has a slower wind (23 mph @ 52 volts), so I think upping the voltage will only provide modest increases in velocity. Did yours melt because you pushed it harder, or just developed more heat with the same riding style?

E-HP · Jul 18, 2019

thundercamel said:
I don't suppose you have any way to monitor current draw? What I'm trying to get at, is it's possible that a 52 volt battery that didn't sag much could produce your desired power level longer.

I have a meter, but I removed it and the shunt during my last updates to my bike, to get rid of the clutter. The battery definitely sags, but I'm pretty sure not enough to trigger LVC based on looking at the voltage and power on the LCD3 display. At about 90% charge, it may sag to 50 volts when riding up a steep grade and pulling 2000 watts. In the end, I want to be able to use my existing battery up, but still enjoy the extra power from upping the voltage using the extra series pack. Then replace the packs with a 60 volt or 72 volt pack at a later point.

I also haven't even started looking into charger options for the mini pack. I think my first step is to buy a flexible controller, so I can start tinkering with other options.

thundercamel · Jul 18, 2019

E-HP said:
My motor has a slower wind (23 mph @ 52 volts), so I think upping the voltage will only provide modest increases in velocity.

That's right, I remember that now from your build thread. If that's the case, I would go straight for 72 volts then (which I don't have any experience with btw), and it most certainly will increase your speed significantly!

23 mph would become 31 mph.

E-HP · Jul 18, 2019

thundercamel said:
E-HP said:

My motor has a slower wind (23 mph @ 52 volts), so I think upping the voltage will only provide modest increases in velocity.

Click to expand...

That's right, I remember that now from your build thread. If that's the case, I would go straight for 72 volts then (which I don't have any experience with btw), and it most certainly will increase your speed significantly!

23 mph would become 31 mph.

Thanks. I did some searching and I saw one post that said the throttle would be more sensitive. That could be an issue since my crappy throttle seems to not have a low range, and kicks in at about half power when it does. Not sure if PAS would be an issue, but I wouldn't want to start at each intersection with a wheelie.

neptronix · Jul 18, 2019

ebikes.ca motor simulator will answer this question. :thumb:

electric_nz · Jul 18, 2019

Is it easier to get chargers and BMS for 60V or 72V applications? The only ones I can see at a glance seem to be the generic ones.

Tommm · Jul 18, 2019

72v ecosystem is better for going above 2500w.

neptronix · Jul 18, 2019

electric_nz said:
Is it easier to get chargers and BMS for 60V or 72V applications? The only ones I can see at a glance seem to be the generic ones.

BMSes are fairly easy. The problem is the selection of chargers once you get above 50.4v/14S. This is a big reason that i like making power with more amps and less volts.

Tommm · Jul 18, 2019

neptronix said:
electric_nz said:

Is it easier to get chargers and BMS for 60V or 72V applications? The only ones I can see at a glance seem to be the generic ones.

Click to expand...

BMSes are fairly easy. The problem is the selection of chargers once you get above 50.4v/14S. This is a big reason that i like making power with more amps and less volts.

Aliexpress is full of them. I use kingpan 72v 5a.

neptronix · Jul 18, 2019

Tommm said:
Aliexpress is full of them. I use kingpan 72v 5a.

Yah... because DC-DC/DC-AC devices are expensive to build properly, a lot of Chinese companies sell cheap ones that are poorly engineered. I remember kingpan chargers being regarded as disposable a long time ago.

Another issue is that the cheap chargers are not programmable, and only a few are easily modified. What if you want to charge to 90% to save battery life, or the factory set the voltage to 4.21v, or some other goofy crap? these things do happen.

There's a lot of stuff on aliexpress that isn't worth touching with a ten foot pole

E-HP · Jul 18, 2019

neptronix said:
ebikes.ca motor simulator will answer this question. :thumb:

Thanks for the reminder. Switching between 52 and 72 volts using the MXUS XF07 as the motor (not mine, but I noticed that the specs are very close when I've used it before), there's a measurable increase in torque at max, but the torque curve provides a lot more torque longer, so at 15 mph , the torque was double (35 vs 70 N-M). It looks like it will have the desired effect, until I push it too hard.

amberwolf · Jul 18, 2019

E-HP said:
That could be an issue since my crappy throttle seems to not have a low range, and kicks in at about half power when it does.

Most likley the throttle thing is the controller's response to teh throttle, not the throttle itself.

If it is the throttle itself, then if you have a Cycle Analyst v3 you can tune the throttle input and output voltages to get the response range you want, as long as the throttle doesn't literally just output nothing until it gets to the middle of it's physical range. That you'd have to fix by moving the magnets inside the throttle.

amberwolf · Jul 18, 2019

E-HP said:
I also haven't even started looking into charger options for the mini pack.

If you don't mind the cost, the Cycle Satiator has a 72v version.

If you need cheaper but still sealed/potted for weatherproof (or just plain durability and silence), the Meanwell HLG series will work--you can series two of them for the voltage (probably two of the 48v units, each turned down to half of the total final charge voltage you want. Two HLG-300H-48A would give you charging at something around 6-7A max.

I'm sure there's cheaper stuff...but the above would likley be more reliable, and can be adjusted for voltage and current.

E-HP · Jul 19, 2019

amberwolf said:
E-HP said:

That could be an issue since my crappy throttle seems to not have a low range, and kicks in at about half power when it does.

Click to expand...

Most likley the throttle thing is the controller's response to teh throttle, not the throttle itself.

If it is the throttle itself, then if you have a Cycle Analyst v3 you can tune the throttle input and output voltages to get the response range you want, as long as the throttle doesn't literally just output nothing until it gets to the middle of it's physical range. That you'd have to fix by moving the magnets inside the throttle.

It's actually the crappy throttle that came with the kit. I was using another throttle that worked well, but the kit on has a switch that I wanted to use with my headlight. I didn't realize how bad it was until installing it. It's literally an on off switch and surges when it kicks in. Dangerous when I navigate around foot traffic, so I'm swapping it out this weekend.

E-HP · Jul 19, 2019

amberwolf said:
If you don't mind the cost, the Cycle Satiator has a 72v version.

Thanks. I didn't see the 72v version until you mentioned it. I think I'll eventually get there, but hoping to defer the purchase a little while. For my current transition plan, using my existing 52 volt pack (14s8P, so if I go with 60v, then I can rebuild the pack later with 16s7P, which should fit perfectly) and a smaller pack in series (to get to 60 or 72 volts), I'm wondering if the 72v Satiator has the range to charge the smaller pack (60v version looks like it goes lower). I'm probably not going to use a BMS for the smaller pack.

Thinking out loud, if there's a creative way of doing proof of concept testing for 60v and 72v, then I could easily see how those voltage levels would behave. I haven't used lipo, but will eventually get there at some point, so if adding a pack or two in series with my pack would work, at a reasonable cost, I could test and decide. I just need a controller that will handle both, or all three voltage levels (52v, 60v, 72v).

john61ct · Jul 19, 2019

Satiator 72V model starts at minimum 20V, so 4S for most LI chemistries, 5S for LFP.

max is 103V

48V version is 12 - 63V

Both are 0-360 watts, so their rated amps max only applies when volts are lower.

ZeroEm · Aug 12, 2019

A little late. CA3 states not to use PAS with 72V. So I did not try it. There maybe a work around.

amberwolf · Aug 13, 2019

You can use PAS with 72v; the only problem is if you have a higher than (48v?) pack *and* you are using a torque sensor that runs off the 10v power from the CA on the PAS connector, it can cause too high a current thru the main regulator and blow it up. (ask me how I know

)

As long as you are using only a cadence sensor, or you are powering the torque sensor off a separate DC-DC from your pack, then there's no problem I'm aware of.

E-HP · Aug 14, 2019

Thanks everyone for the helpful info. I keep flipping back and forth, but right now I think 60V will get me what I'm looking for.

Ideally finding a sine wave controller that can work both with my current 52v pack, or a new 60v pack would be great, but I'm budgeting $1k to upgrade, so after the battery, I have about $175-$200 to go toward the controller, limiting my options. By far the easier upgrade would be to get the same battery pack, but in 60V and the same controller, but in 60V. KT has a 60V sine wave, which I found were carried by several vendors, that I had bookmarked a month or so ago. All of those bookmarks now say out of stock, right when I was getting close to pulling the trigger.

For the battery, which will be a UPP pack, I'm now trying to decide on the cells. They offer Samsung 2900 mah, and Sanyo 3500 mah. The Samsung are in a 16S7P configuration, and the Sanyo are 13S6P. I need to research this more since I'm not sure how they both land at 60V, with 3 less cells in the Sanyo series. An advantage of the Sanyo cells are that the packs are lighter. I just want to understand the chemistry better before pulling the trigger on the battery purchase.

So, basically I'm very close to upgrading now, but still have things to work through. It might work out better this way, since ideally I'd find a sine wave controller that handles both 48V and 60V, and within the $200 budget, which I will continue to search for.

john61ct · Aug 14, 2019

What is UPP?

E-HP said:
The Samsung are in a 16S7P configuration, and the Sanyo are 13S6P. I need to research this more since I'm not sure how they both land at 60V, with 3 less cells in the Sanyo series.

Not possible, brand does not matter, basic math and chemistry rules.

16S is 59.2V nominal, charge at 64-67.2V, cutoff at 48-56V.

13S is 48.1 nominal, charge at 52-54.6, cutoff at 39-45.5V

Unless you include LFP or LTO choices, which I believe neither of those makers produce, at least not in tiny cylindricals.

A pack being lighter per kWh (energy density) usually is not a good sign for longevity.

garyal1 · Aug 15, 2019

thundercamel said:
E-HP said:

My original plan was just to go to 60 volts, since I'm really happy with my bike's performance when the battery is fully charged and for the first 10 miles of battery. After that, the sag makes it less peppy on acceleration or hill climbing.

Click to expand...

I'd say you should first confirm whether it's less peppy due to an overall lower voltage, or if the controller is getting close to it's low voltage cutoff point, and is starting to limit current draw.

This screenshot is from the SmartBMS on my wife's bike, which originally had some significant voltage sag from the Vruzend 3.5 amp caps being pushed past their limit. You can see the linear nature of the current limiting on the green line, as the voltage under load got lower. Once I rebuilt the pack with nickel strips spot welded, the voltage sag was greatly reduced, and that current limiting doesn't kick in until the pack is almost empty. The bike now feels like it has the same amount of power from 100% through 15% instead of the previous 100% through 40%.

I don't suppose you have any way to monitor current draw? What I'm trying to get at, is it's possible that a 52 volt battery that didn't sag much could produce your desired power level longer.

Thanks to Thundercat for this post. It was the answer to my problem on my newest Frey Ebike! Great explanation and it was correct.

60 volt vs 72 volt

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