Is this setup possible?

[Jonasan-san]

A battery blender typically measures the voltage of each battery with a shunt and disables current from flowing into the weaker battery via a MOSFET. Some controllers are actually incompatible with some cheaper battery blenders and throw an overvoltage error when used with them because they expect to be able to dump current back into the battery in some situations (non-clutched motor when running as a generator, etc.). More expensive battery blenders also allow charging, though, which doubles the number of FETs needed.

If your two batteries are the same voltage and capacity, typically better to just parallel them, making sure they are exactly the same voltage when you do.

what are the advantages of parallel vs using the blender?

 

[neptronix]

Battery Blender™ - www.sparkcycleworks.com

Add a second battery to your electric bike today! NOT COMPATIBLE WITH REGEN! Blend any 2 batteries using even different voltages and chemistries Compatible with 72V and Under XT60 Connector: 30 Amp Rating/ 35Amp Rating Experimental (must allow adequate air flow around device)

www.sparkcycleworks.com

Dual battery combiner for e-bike 24V-72V DC input pack balancer | Johnny Nerd Out Cust

Dual battery converter with wide DC input 24V -72V. Output: DC 24V -72V, max 40A current. Input with Anderson connector; output with Anderson connector. Xt90 connectors can handle up to 80a. If you have two batteries(24V-72V) with different voltages or the same voltage, you want to use the two...

www.johnnynerdout.com

Spark cycle works unit: what's inside it? i really wonder how reliable such a simple electronic unit is.. controlling current flow and voltage is difficult and circuits that do that kind of work are usually big / need heatsinking. That looks a little DIY.

A battery blender typically measures the voltage of each battery with a shunt and disables current from flowing into the weaker battery via a MOSFET.

If the above is true ( i imagine it is since the unit is so small ), then this won't result in lower sag and therefore better efficiency.


The second unit is a DC-DC ( more sane approach, electrically ), but with that comes a 5-20% conversion loss ( depends on the circuit design ), so it's very likely you'll end up losing or not gaining efficiency in the end.

If you do not have the batteries already then now would be the time to spec them correctly so you don't need corrective devices like these.

 

[Jonasan-san]

Spark cycle works unit: what's inside it? i really wonder how reliable such a simple electronic unit is.. controlling current flow and voltage is difficult and circuits that do that kind of work are usually big / need heatsinking. That looks a little DIY.


If the above is true ( i imagine it is since the unit is so small ), then this won't result in lower sag and therefore better efficiency.


The second unit is a DC-DC ( more sane approach, electrically ), but with that comes a 5-20% conversion loss ( depends on the circuit design ), so it's very likely you'll end up losing or not gaining efficiency in the end.

If you do not have the batteries already then now would be the time to spec them correctly so you don't need corrective devices like these.

I already have a 52v 20ah 40a continuous battery that came with my bike. How would I know how to spec my 2nd battery correctly?

 

[neptronix]

Warning. this is technically impossible. At most a lithium battery can tolerate 15-25% energy loss ( becomes heat ), depending on the chemistry, before catching on fire. It is technically impossible that such a device could save this much power because a battery would shut down ( hopefully ) or catch fire before that happened.

This would be the ideal device to stretch out an old saggy battery by pairing it with a stronger battery but if you are buying a new one, this isn't the case.

I'm kind of dubious now, i suggest you look for long term experiences with these before you buy; maybe they are legit but IDK.
When i see a seller making claims like that, i think this is more of a marketing company than an engineering company, let's say

I already have a 52v 20ah 40a continuous battery that came with my bike. How would I know how to spec my 2nd battery correctly?

Yes, take the maximum continuous current of the smaller motor, double it, and find a battery that meets that 2x the output you need spec. This will result in ~5% energy loss which is acceptable.

Ideally i like 4x the output power i need because the voltage drop will be more like a volt or two at most, somewhere in the 98-99% efficiency range is pretty nice out of the gate; as the battery ages and the internal resistance goes up ( resulting in more sag ), i still have plenty of headroom and therefore

Worst case scenario for selecting a battery is putting a 40a motor on a 40a output battery.. in these conditions you can be losing 10-15% efficiency at peak power.. and freezing temperatures can cut your amp output by 1/4th so in those situations, a battery with 'just enough power' at ambient temperatures becomes one that is inadequate when the cold comes. Not so much with the 4x overspecced battery

 

[lnanek]

That's a completely valid benefit. I've used a battery blender before where my OEM battery was 13Ah and my new secondary battery was 22Ah, for example. Range of the bike obviously goes up over 100% in such a case. People often use them to add a higher voltage battery as well. It's perfectly valid to use one with a 52V battery and a 48V battery, for example. Something you can't do by paralleling the batteries.

 

[neptronix]

That's a completely valid benefit. I've used a battery blender before where my OEM battery was 13Ah and my new secondary battery was 22Ah, for example. Range of the bike obviously goes up over 100% in such a case. People often use them to add a higher voltage battery as well. It's perfectly valid to use one with a 52V battery and a 48V battery, for example. Something you can't do by paralleling the batteries.

Interesting, by any chance did you note if it increased watt draw etc from conversion losses?

Battery blender here is quoting 7.5w of loss which seems extraordinarily low; this would be ~99.9% efficient at 1000w and typically even the most expensive and ornate power modulating circuits don't reach this kind of efficiency.

Admittedly equalizing 48v and 52v battery happens at a low duty cycle ( imagine this contributes to efficiency because the switching losses may be lower ) so IDK, hoping for more info

 

[lnanek]

7.5w doesn't seem low to me. You could check the data sheet for the MOSFET used if you really need to know the number. Another name for the battery blender circuit is "ideal diode". That's because it's the same as sticking a diode/schottky diode in front of each battery, but doesn't have the high voltage drop associated with that approach. That high voltage drop of the diode approach is what burns a lot of watts and makes a lot of waste heat. Using MOSFETs instead is using exactly what the typically ebike BMS and controller use anyway, so you aren't going to get more loss and heat from this than from your BMS.

 

[neptronix]

I'm thinking 7.5w is low if we're doing any kind of switching/current limiting to combine the two batteries power.. 7.5w is average or maybe even high if we are just using it as a periodic switch between battery A and B. If this is how the above device is designed, then OP won't get the benefit of balancing the load between two batteries that he's looking for..

Could use more info on how this device works to be certain.

 

[DanGT86]

what are the advantages of parallel vs using the blender?

Advantages of parallel without the blender are:

1. simplicity- You have 2 batteries that now function as one large battery. They will stay at the same voltage together during charge and discharge.
2. Capacity- You add the AH capacity together to get the total.
3. Range- more capacity=more range
4. Less voltage sag- Discharging from a larger battery puts less stress on each individual cell
5. You can have the possibility of regen depending on motor and drive choices

Advantage of the blender

1. You can combine batteries of different voltages or combine batteries of the same nominal voltage regardless of their state of charge.

I agree with the others that if you arent trying to run different voltage batteries the blender is unnecessary. No reason to add points of failure and expense if you dont need to.

As for specs on the 2nd battery I would just total up the current needs of both systems and make sure the sum total of the two batteries is up to the task. So if you need 30amps for each drive make sure you have a battery that can output 60amps. This is not an absolute rule but its probably the safest and simplest way to figure it out.

 

[Chalo]

That foolish thing is a solution looking for a problem. Just charge both batteries to the same voltage and then connect them in parallel. Complicating it adds points of failure without contributing anything of value.

 

[E-HP]

That foolish thing is a solution looking for a problem. Just charge both batteries to the same voltage and then connect them in parallel. Complicating it adds points of failure without contributing anything of value.

The one thing I've had an issue with a couple of times was accidentally turning off the switch on one of the paralleled packs. When it happened on the road, I noted the pack voltage of the pack still hooked up, then disconnected it and turned on the other pack and rode until the voltage matched, then reconnected in parallel. It was a pain, but at least I didn't have to cut the ride short. I put a piece of tape over the switch as a reminder.

 

[Mongo]

I can't contribute anything to the OP. Still, I wonder how a linked by a single throttle hub motor and (presumably multi-geared) BBSHD could work at their respective optimal RPMs, in tandem - at least at anything other than in a particular narrow speed range?

You've got a steep hill to climb. So you gear down the BBSHD, so it's spinning and happy, but now the hub motor is lugging, and it's mostly making heat versus oomph. From my armchair and admittedly naive view, the arrangement sounds like a mess - versus a single, high-power-capable & modified BBSHD, a big honking WA and high-current BMS'ed battery, and a beefed-up drivetrain.

 

[Jonasan-san]

I can't contribute anything to the OP. Still, I wonder how a linked by a single throttle hub motor and (presumably multi-geared) BBSHD could work at their respective optimal RPMs, in tandem - at least at anything other than in a particular narrow speed range?

You've got a steep hill to climb. So you gear down the BBSHD, so it's spinning and happy, but now the hub motor is lugging, and it's mostly making heat versus oomph. From my armchair and admittedly naive view, the arrangement sounds like a mess - versus a single, high-power-capable & modified BBSHD, a big honking WA and high-current BMS'ed battery, and a beefed-up drivetrain.

The torque from one motor helps the other maintain speed.

 

[bengxe]

I ran a bbs02 with a direct drive rear hub for a few months, both paralleled off 1 battery. I tried a lot of different throttle setups but what worked best for me was 2 thumb throttles next to each other, set so I can either press the hub throttle alone or both motors together. I did it for extra reliability through redundancy, I had a long commute and it was my first e-bike. Nowadays my hub has proven perfectly reliable while making more power than the 2 motors ever did together.
You'll want to check the free speed of your mid drive in each gear so you can match the hubs free speed, and then only cruise in that gear.

 

[Jonasan-san]

I ran a bbs02 with a direct drive rear hub for a few months, both paralleled off 1 battery. I tried a lot of different throttle setups but what worked best for me was 2 thumb throttles next to each other, set so I can either press the hub throttle alone or both motors together. I did it for extra reliability through redundancy, I had a long commute and it was my first e-bike. Nowadays my hub has proven perfectly reliable while making more power than the 2 motors ever did together.
You'll want to check the free speed of your mid drive in each gear so you can match the hubs free speed, and then only cruise in that gear.

I've been wondering the best way to match the motors, you've really helped me out thank you!

 

[JgossofArk]

I recently replaced a blown set of controllers on an Ariel Grizzly. I bought the no name linked controllers off amazon for $130 they seem to work fine. I did lose pedal assist. Another issue I am working around is that the front wheel seems to spin wildly faster than the rear so it's not worked out perfectly yet but I am getting darn close. Some one mentioned to me that I might try identical controllers with 1 throttle but have a potentiometer set up so you could adjust one motor speed as needed for fine tunning.

Linked controllers

Again this is my first dive into this but I am enjoying it. Take it for what it's worth....

 

[DanGT86]

I recently replaced a blown set of controllers on an Ariel Grizzly. I bought the no name linked controllers off amazon for $130 they seem to work fine. I did lose pedal assist. Another issue I am working around is that the front wheel seems to spin wildly faster than the rear so it's not worked out perfectly yet but I am getting darn close. Some one mentioned to me that I might try identical controllers with 1 throttle but have a potentiometer set up so you could adjust one motor speed as needed for fine tunning.

Linked controllers

Again this is my first dive into this but I am enjoying it. Take it for what it's worth....

Check your hall and phase wiring on the front motor. Some of the wire combinations will spin the motor way fast and use draw lots of current.

 

[JgossofArk]

Check your hall and phase wiring on the front motor. Some of the wire combinations will spin the motor way fast and use draw lots of current.

Thank you! I will there is something out of whack with that as the controller was getting real hot fast which is exactly what you are saying- I will double check that and should be on my way! I did plug in the self learn wires maybe there is only so much they can do- it was spinning in the right direction after all. Thanks for the pointers, this is my next mission!

 

[JgossofArk]

Thank you! I will there is something out of whack with that as the controller was getting real hot fast which is exactly what you are saying- I will double check that and should be on my way! I did plug in the self learn wires maybe there is only so much they can do- it was spinning in the right direction after all. Thanks for the pointers, this is my next mission!

Sure enough. I have 2 bad hull sensors. It's #3 and the speed sensor #4 that works off the button magnets on the case cover. For future reference this thing was rusty when I cracked it open. I soaked the entire assembly in evaporust. We will see if it works I tested phase wires for the same resistance they passed and shorted out all combos which provided noted feedback when turning the stator so I am on the right track. I had some concern that evaporust would harm the winding tha does not appear to be the case.
Cheers.

 

[DanGT86]

Thank you! I will there is something out of whack with that as the controller was getting real hot fast which is exactly what you are saying- I will double check that and should be on my way! I did plug in the self learn wires maybe there is only so much they can do- it was spinning in the right direction after all. Thanks for the pointers, this is my next mission!

Glad you are making progress. The false correct hall/phase combo is annoying. I have had some motors that spun but were just a little unhappy sounding. If it weren't for the high amp draw on my meter I wouldn't have known they were wrong.

I have never successfully used those self learn wires on most cheap controllers.

 

[E-HP]

Also the elimination of voltage sag.

A battery blender will do nothing for voltage sag. Paralleling the batteries will. It's good for folks that may get careless and keep them from blowing things up or starting a fire when working with more than one battery. All of the performance advantages come from directly paralleling.

 

[lnanek]

Yeah, when I was using one I had to set the max battery amps of my controller to 20A to match the 20A max discharge of my weakest battery even though my other battery could handle double that. Anything else and the BMS on that battery would often trip and I'd have to turn it off and back on again to get it contributing to my range again. The blender may have either battery cut off at any time depending on the voltage measurements it makes. So you are limited to the max discharge voltage and voltage sag characteristics of the weakest one.

Paralleling requires similar batteries, but gives 2x the matched max discharge of a single one and reduces the voltage sag effect since both batteries are always active.

 

[REDHAWK RIC]

If your two batteries are the same voltage and capacity, typically better to just parallel them, making sure they are exactly the same voltage when you do.

Is this true? I have same voltage, same capacity and same maker, if I always charge both to fully charged can I run parallel?

 

[Chalo]

Is this true? I have same voltage, same capacity and same maker, if I always charge both to fully charged can I run parallel?

Absolutely. Best practice is to separate them for recharging (to the same voltage), but run them in parallel every time. That way, each pack only has to work half as hard, and they both get the same duty cycles.

 

[E-HP]

Well in terms of current yes, but motor efficiency changes with gear ratios on a mid-drive as well as the motors being rated for different wattages so there are discrepancies to be evened out. Also the elimination of voltage sag.

Neither of the devices you linked will help with voltage sag. Paralleling batteries without the hokey box will reduce sag.