Off-Grid Solar Battery?

[WaterWiz]

Hello all!

Let me cut to the chase. I have a 15KW off-grid solar panel set up with 50KW of home battery storage. I have also modified my golf cart with a 5KW lithium battery. I can monitor all batteries using Solar Assistant via RS485 communication. I want to dive into powering my bikes and kayaks with lithium batteries. I have 3 kayaks and 3 bicycles. I envision a bank of 6 wall-mounted *48V batteries connected in parallel to my solar charge controller output and my home/golf cart batteries. When not using the bikes/kayaks they will contribute as battery backup to the home.

Questions:
1. Why are ebike batteries labeled 48v and 52v? 48V lithium is nominal they charge well above 52v but its still a 48v battery
2. Are there any prebuilt ebike batteries with rs485?
3. I assume the ebike batteries have BMS that will limit incoming/outgoing currents. Can ebike batteries charge/discharge at 30-60 amps?

Thanks!

 

[HumanPerson]

Hello all!

Let me cut to the chase. I have a 15KW off-grid solar panel set up with 50KW of home battery storage. I have also modified my golf cart with a 5KW lithium battery. I can monitor all batteries using Solar Assistant via RS485 communication. I want to dive into powering my bikes and kayaks with lithium batteries. I have 3 kayaks and 3 bicycles. I envision a bank of 6 wall-mounted *48V batteries connected in parallel to my solar charge controller output and my home/golf cart batteries. When not using the bikes/kayaks they will contribute as battery backup to the home.

Questions:
1. Why are ebike batteries labeled 48v and 52v? 48V lithium is nominal they charge well above 52v but its still a 48v battery
2. Are there any prebuilt ebike batteries with rs485?
3. I assume the ebike batteries have BMS that will limit incoming/outgoing currents. Can ebike batteries charge/discharge at 30-60 amps?

Thanks!

Welcome to the forums

 

[HumanPerson]

Hello all!
Questions:
1. Why are ebike batteries labeled 48v and 52v? 48V lithium is nominal they charge well above 52v but its still a 48v battery
2. Are there any prebuilt ebike batteries with rs485?
3. I assume the ebike batteries have BMS that will limit incoming/outgoing currents. Can ebike batteries charge/discharge at 30-60 amps?

Thanks!

48v batteries are normally charged up to 54.6v, where 52v batteries usually charge up to 58.8v

Li-Ion Ebike Battery Charge Charts

Whats an 80% charge on a 48v battery? These charts give answers to questions like this on common ebike battery voltages: 36v, 48v, 52v, 60v and 72v.

talesontwowheels.com

Not sure about the rs485

Yep the BMS built into the battery if you get one of good calibre will have va good BMS and some you can get upwards of
400 amps, those usually go on Surrons or big ebikes/emotorcycles.

Hope that helps

 

[WaterWiz]

Does this sound correct? When charging solar batteries I have absorption and float modes. If I apply 55-57 volts to a 48v pack the BMS will limit input. Or should I just use 52 volt packs and not charge to 100%. Is balancing and viewing cell voltage not done on e-bikes via BT? I'm not seeing the discussion.

 

[Rockbike]

Hello all!

Let me cut to the chase. I have a 15KW off-grid solar panel set up with 50KW of home battery storage. I have also modified my golf cart with a 5KW lithium battery. I can monitor all batteries using Solar Assistant via RS485 communication. I want to dive into powering my bikes and kayaks with lithium batteries. I have 3 kayaks and 3 bicycles. I envision a bank of 6 wall-mounted *48V batteries connected in parallel to my solar charge controller output and my home/golf cart batteries. When not using the bikes/kayaks they will contribute as battery backup to the home.

Questions:
1. Why are ebike batteries labeled 48v and 52v? 48V lithium is nominal they charge well above 52v but its still a 48v battery
2. Are there any prebuilt ebike batteries with rs485?
3. I assume the ebike batteries have BMS that will limit incoming/outgoing currents. Can ebike batteries charge/discharge at 30-60 amps?

Thanks!

You might get more high-quality feedback if you use the proper terms for power and energy. Power is kW, energy is in kWh. Two very different things and it's hard to follow what you are saying when you label everything as power, even when you mean energy.

 

[smritte]

Not an "e-bike" battery/controller expert but I build my own battery packs for projects and have been playing with off-grid solar for a couple of decades in my campers. Unfortunately, your questions really need to be directed at the diffrent E-Bike battery manufacture's.
It's possible I can answer a few questions based on my experience building battery packs..
If any of my comments appear snarky, it's not intended.

1. Why are ebike batteries labeled 48v and 52v? 48V lithium is nominal they charge well above 52v but its still a 48v battery

The quick answer is "Yes" Why do they label them like that?
It's not just e-bikes but most of the industries and not just batteries. It's confusing, that's why you need to learn about the diffrent lithium types and the required voltages. Almost all of my knowledge stems from this problem. If you think this is bad, you should see the Auto Industry.

2. Are there any prebuilt ebike batteries with rs485?

It wouldn't surprise me to learn that someone did but for the most part, if I was a manufacture, I wouldn't see the need to add in the extra expense. My experience with batteries and BMS's showed me that some battery pack manufactures don't even run a BMS. I'm not referring to exclusively E-Bikes but across the board. With blue tooth, BMS controllers, there's almost no need. My large battery systems use a blue tooth controller and my small systems have no communication..

3. I assume the ebike batteries have BMS that will limit incoming/outgoing currents. Can ebike batteries charge/discharge at 30-60 amps?

Again, this is something that needs to be addressed by a manufacture. All of my BMS units are for charging/balancing, none control output. I would be surprised if any of the E-Bikes actually had a BMS capable of controlling output also. If the battery pack is built correctly, this shouldn't be an issue using a fuse for safety.

One of my next projects is going to be a range extender for my Levo. A spare battery is (US) $1300 and being a class 1 the battery isn't quick to change.

Good luck with your project. It looks like you have a bit of research ahead of you.

 

[WaterWiz]

Thanks for the response! I agree there is a lot to learn but honestly, that is half the fun for me personally. I enjoy the journey almost more than the destination.

Here is where I am now and please forgive me if I do not label my units correctly.

1. I assumed e-bikes primarily used LifePO4 batteries, apparently a lot of them use Li-ion. Based on my limited research I am not even going to consider Li-ion due to potential safety issues. I am going to focus on LifePO4 cells with a BMS so that I can monitor each cell's condition and have enough intelligence to shut down issues. I get there are millions of "safe" Li-ion batteries.

2. It appears that the confusion on the voltages for me is the Li-ion vs LifePO4 battery (still researching). Again I am used to a LifePO4 cell that is rated 3.2v in a 16S configuration. The Li-ion cell appears to be a 3.7v cell in a 13S configuration (or some variation).

3. It appears some e-bike batteries have no BMS at all. Is this the reason for the super slow charging factor? It seems crazy to charge a Li-ion battery with no regulation. Is a BMS however why a Tesla with 18650 cells can be hooked up to a supercharger and be charged at a crazy high amperage? Even with a BMS why the typical slow charger on an e-bike? To clarify the 3.2 LifePO4 with BMS cell can almost charge as fast as it discharges. The battery creates heat on discharge and charge so this cannot be the only limited factor. Again I am learning. I am not an electrical engineer. Can a good Li-ion be charged quickly? I.e. Where does the energy go on a non-BMS-equipped Li-ion battery on a long downhill run? For example, the regenerative charging in my golf cart is 50 amps plus going downhill. I can only assume a 200-pound rider going 20 mph downhill for 20 minutes creates way more energy than a typical e-bike charger. Does this become a potential fire bomb between my legs in this exaggerated scenario?

Thanks, smritte, and good luck with the Levo!

 

[smritte]

For the exact reasons you posted, I wont deal with anything other than LifepO4. Where I live is mostly desert. Lithium is not happy with heat but LifePO4 isn't as bad. In the way of BMS's, I never realized how many diffrent types there were and the fact that some manufactures decide its really not necessary to run one.
In realty, all a basic BMS does is insure each battery has the same voltage. As long as you don't have an issue with a battery, the cells will somewhat balance themselves. The difference in capacity may not be noticed so why go through the expense of a BMS? This is what I believe some manufactures think.

Most of my battery packs are 12 volt, small and power small motors. I charge them by literally plugging into a port tied to my trailer battery. This usually means, unless its daytime and everything is charging by solar, my battery pack only reach's 95% at best. The slight undercharge is not noticeable to me so it's accepted. Batteries don't mind slight undercharge, you never over voltage them.

Your comment about powering your Kayak made me wish I had a picture of the electric motor one of my buddies installed in his. No battery and it was powered my a couple of the narrow long flex panels. two 24 volt panels in series, tied to pool noodles dragging behind. He ran them in series and the 48 volts would shock him if he got into the water near the panels. The fun thing is he drove around all day (slowly) without issue.