84v input to 84v output dc-dc charger

[dylan.h.brown]

Hi guys...

Long time reader, first time poster.

I have a couple of batteries I'd like to use as a remote charging station for when I'm in the backcountry and would like to charge my e-moto.

Here's my specs:
Bike: 72V40ah battery (20s)
Charge Pack: 72V80ah battery (two 20s batteries joined together)

Here's what I'm trying to do: use the "charge pack" as a remote reserve for the bike. Instead of going through an inverter, then a rectifier, I would just like to use a DC to DC charger (or booster or whatever it may be called). Is there anything out there that can do this?

I would charge the "charge pack" at home using the same charger I use for the bike, and also trickle charge it off my truck's inverter (I'm not quite ready to go right off the alternator just yet), so in theory, I would get 2 full charges (not that I will drain my "charge pack" that low unnecessarily.

Thanks for the help!
- Dylan

 

[gobi]

DC to DC to chart your ebike battery. hmm,

I use a drok boost converter to charge my 80v batteries, my input volts is 40v for this.

I am not sure what the MAX input volts is for a drok boost charger.

https://www.amazon.com/Converter-10V-120V-Adjustable-Regulator-Conversion/dp/B08DNFJR4P

dang, it is 60v max, ouch.

So the other solution that I would use is a MPPT solar charge controller as a charger, but your battery to charge is high volts too, so scrap that.


workable solution

72v battery bank > drok buck converter to convert 72v to 48 > drok boost converter to charge battery

This will work but not pretty.

 

[JackFlorey]

I would just like to use a DC to DC charger (or booster or whatever it may be called). Is there anything out there that can do this?

Two RSD-300F-48's in series would do it. You'd have to hack them to reduce the output voltage.

 

[gobi]

Here is a simpler solution:


72v Charge pack > current limiter > ebike 72 battery

you cannot connect the them directly as a massive amount of current will flow depending on the voltage DIFFERENTIAL.

so you can use a current limiter (experts chime in here pls)

I use an inline resister for precharging my inverter/controller,

you could use one like that but it will generate heat and waste power.

 

[dylan.h.brown]

Here is a simpler solution:


72v Charge pack > current limiter > ebike 72 battery

you cannot connect the them directly as a massive amount of current will flow depending on the voltage DIFFERENTIAL.

so you can use a current limiter (experts chime in here pls)

I use an inline resister for precharging my inverter/controller,

you could use one like that but it will generate heat and waste power.

I like this option best. Where would one find a current limiter?

My current setup in my mind (the best way I understand it) would be this:
- Trickle charger from the onboard genset – 84v5A. This will charge my "bank" continuously, being regulated by charger limiter, and also BMS.
- Use an inverter (just received a 5000W output, 72V input from China) to power my ac->dc charger for the bike.

This is a system I think will work fine, but I don't like all the loss --> DC (truck's battery/alternator)->AC (can use shore power when available)->DC (battery bank)->AC (inverter)->DC (bike battery)

I really think there should be a simpler way... I'll continue researching current limiters.

 

[E-HP]

Here is a simpler solution:


72v Charge pack > current limiter > ebike 72 battery

you cannot connect the them directly as a massive amount of current will flow depending on the voltage DIFFERENTIAL.

so you can use a current limiter (experts chime in here pls)

I use an inline resister for precharging my inverter/controller,

you could use one like that but it will generate heat and waste power.

I like this option best. Where would one find a current limiter?

My current setup in my mind (the best way I understand it) would be this:
- Trickle charger from the onboard genset – 84v5A. This will charge my "bank" continuously, being regulated by charger limiter, and also BMS.
- Use an inverter (just received a 5000W output, 72V input from China) to power my ac->dc charger for the bike.

This is a system I think will work fine, but I don't like all the loss --> DC (truck's battery/alternator)->AC (can use shore power when available)->DC (battery bank)->AC (inverter)->DC (bike battery)

I really think there should be a simpler way... I'll continue researching current limiters.

How much do you hope to get out of the big battery? First charge, assuming your big battery starts at 84V, will probably get your bike battery up to maybe 74V-75V, since the big battery will be dropping voltage as is discharges, so can never charge any higher. Second charge, starting out at 74V, you may get your bike battery charged up to 70V or so. Just ballparking, but you get the idea. You'll never get all of the energy or even a full charge out of the big pack if you just connect it to the bike battery.

Parallel everything and pull the big battery on a trailer.
https://www.amazon.com/Cycle-Force-Bicycle-Surfboard-Trailer/dp/B071HGY2FX/ref=asc_df_B071HGY2FX/?tag=&linkCode=df0&hvadid=385369212868&hvpos=&hvnetw=g&hvrand=1439759411721380855&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9032086&hvtargid=pla-834261752608&ref=&adgrpid=84216683248&th=1

 

[DogDipstick]

nevermind my reply: I read the question wrong.

72v 80Ah?

 

[999zip999]

Why does the charge battery have to be 72 volts can you get it to a lower voltage so you use a boost charger.

 

[dylan.h.brown]

Why does the charge battery have to be 72 volts can you get it to a lower voltage so you use a boost charger.

The main reason is I own these two batteries. I designed an e-moto from the ground up, found a company that would build a battery pack for me (LG Lipo), but as things would have it, the bike design changed, and thus the batteries no longer fit. I have already spent the money on the packs, so would like to utilize them best I can.

 

[999zip999]

Yea yea I order a custom battery and wanted 27100 cells to fit em3ev triangle bag ,Oh it's for 18650 so the zipper couldn't close. Plus to heavy for the sitching. diy. Will follow your thread
I can run a heater and a hairdryer on my 72 volt battery can you run a charger on your DC 72 volt battery ? I'm just guessing I don't know what the uck I'm talking about. Don't try at home.

 

[dylan.h.brown]

Yea yea I order a custom battery and wanted 27100 cells to fit em3ev triangle bag ,Oh it's for 18650 so the zipper couldn't close. Plus to heavy for the sitching. diy. Will follow your thread
I can run a heater and a hairdryer on my 72 volt battery can you run a charger on your DC 72 volt battery ? I'm just guessing I don't know what the uck I'm talking about. Don't try at home.

I bought a 72V inverter – 5000w, so I can run a heater, hair dryer, water heater, etc. This is a very cool setup for winter camping – no genny running or even wood stove in the tent, just a space heater. This is an added bonus, for sure, but ultimately, I want to be able to ride from camp, come back and charge up the bike w/o turning on my truck to charge.

 

[999zip999]

What battery do you use and how big is it is this the same battery that you use for your bike ?

 

[dylan.h.brown]

What battery do you use and how big is it is this the same battery that you use for your bike ?

Yes, same battery, but I have two I am planning on wiring up in parallel to use for the "bank".
These batteries are LG LiPo 20s. 72v40ah.

 

[E-HP]

What battery do you use and how big is it is this the same battery that you use for your bike ?

Yes, same battery, but I have two I am planning on wiring up in parallel to use for the "bank".
These batteries are LG LiPo 20s. 72v40ah.

Ah, didn't pick up on that from the other posts. So these are pouch cells?

 

[dylan.h.brown]

What battery do you use and how big is it is this the same battery that you use for your bike ?

Yes, same battery, but I have two I am planning on wiring up in parallel to use for the "bank".
These batteries are LG LiPo 20s. 72v40ah.

Ah, didn't pick up on that from the other posts. So these are pouch cells?

I believe so, yes. I didn't build the packs myself, and haven't open them up to see. But yes, that is my understanding.

 

[gobi]

Op,
You best solution is to find a DC to DC boost converter that will take in put as high as your batts fully charged voltage and use that to charge your other cell, the downside is that you are NOT going to charge very fast.

Better solution is to get a 72v inverter and use that with your A/C charger.