Scalable multiples of 12V packs? first ebike than off grid

joe81

joe81

100 W
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Oct 11, 2015
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131
Location
Berlin
I am wondering if there is already a solution available for easy DIY pack and layman BMS building that is reconfigurable? The idea is reusing of the ebike battery later in an off grid solar setting.
Now I'm thinking about getting myself a big 60 or 72V battery for the bike and say in two years I will have to replace my lead acid 24V battery. By this time the bike battery will start to show first signs of wear but be still good for many years connected to a solar charger.
But how to strategically buy a battery i this case? I guess buying many 12V batteries with each having their own BMS is tricky, much more expensive, and inconvenient when charging, right?
 
If you can use a 48 volt pack, or for longer range and better/more amp draw, use two 48 volt packs in parallel,
because
there are 48 volt DC , products for Off-Grid Solar enthusiasts.

Then a couple of years in the Future you can charge up each 48 volt pack.

I forgot what exact products are available ( 48 volt solar charge controllers ) are still available
at this time.

Also, there used to be plenty of inverters that would take that 48 volts DC and change it to AC to run your household products .

The advantage of using 48 volt charge controllers and 48 volt DC to AC True-Sine Wave Inverters, is that you can use thinner gauge wires with your system.
 
Hey ScooterMan.
I was debating switching to 48V/60V in the off grid system too. So in this case I would mainly need a new solar controller and inverter (both relatively cheep). But I was hoping I can do without AC at all - except for the fridge. And here I already bought a ridiculously expensive solution that runs on 12/24 or 110/240V. Wouldn't do it again like that.. Anyway these days most loads actually want DC so no need to convert into AC in between (laptop, LED lights...). Have an inverter from 24V to AC - nearly never had a need for it for myself.
I don't want TV and all the consumer electronics stuff - for sure that would be much cheaper to get in the mass market AC versions - so for my current situation staying with 24V for all the small loads would probably be best.
 
Hi, I just got a small inverter for the occasional 110v item also. Microwave and tv!

Anyway, wouldn't they have stepdown converters from xx to 12/24v? Otherwise there must be 12v + bms packs available (or at least cells for diy bms), though unless you could find used from industrial back up systems or the like (tho defeating the purpose of dual purpose ebike/offgrid), they would have to be fairly expensive. Don't some ev packs have modules of the proper voltage?

So I guess I'd look at step down converters if they exist or get a new charge controller, cheapy mod sine inverter, and sell the expensive one you don't use much. Potentially easy and simplest route if you don't want to modify the pack again for 12/24 use.

I was thinking of sourcing ev or industrial backup supply lithium to suppliment and eventually replace my small bank. I'd def read a post/ writeup on your setup, as I'm very new to 'offgrid'. Also interested in high functioning (like the $2k models) composting toilet diy.
 
Being completely off Grid does have its benefits, the only setbacks are in regards to
1) washers and dryers
2) heaters
3) air conditioners
and any other very high amp drawing appliance .
( or you win the Lotto and can afford a Tesla Car but still live out in the country and away from the grid )

People get around those situations by just using a generator when needed.
Generators are much cheaper now. ( however its is still best to get a good name brand with warranty )

I was current on what products were available in regards to 24 and 48 volt DC , some 10-14 years ago so I forgot much of that now.

From what I do remember, there were plenty of off grid appliances that ran on 24 volt DC, and a few that ran on 48 volts DC .

There are more and cheaper DC to DC converters these days, don't know how reliable they are though.

But most of the 48 volt DC stuff , if I remember correctly was military, so if you can find a place that sells older military stuff , there might be some products there.

Electric motors can be repaired if not working, however in the case of absorption refrigerators they are expensive to repair, the main killer of them is the person not having the
Fridge level ( on flat ground ) . there are groups that live and know allot about Off-Grid Living, I lost track of them ( the bookmarks ) many computers ago.




joe81 said:
Hey ScooterMan.
I was debating switching to 48V/60V in the off grid system too. So in this case I would mainly need a new solar controller and inverter (both relatively cheep). But I was hoping I can do without AC at all - except for the fridge. And here I already bought a ridiculously expensive solution that runs on 12/24 or 110/240V. Wouldn't do it again like that.. Anyway these days most loads actually want DC so no need to convert into AC in between (laptop, LED lights...). Have an inverter from 24V to AC - nearly never had a need for it for myself.
I don't want TV and all the consumer electronics stuff - for sure that would be much cheaper to get in the mass market AC versions - so for my current situation staying with 24V for all the small loads would probably be best.
Click to expand...
 
What about 7s packs, for 24v? Then two make up a nice 14s 48v pack. Isn't there plenty of 24v solar stuff?

12v is kind of awkward for lithium, most types that's 3s for just 12.6v, and 4s is 16.8v. and Ideal would be more like 13.5v?
 
Dan, I had a look at the nominal voltages given here:
http://www.batteryuniversity.com/learn/article/types_of_lithium_ion
NMC chemistry should be possible with 12V comfortably too.
But yes 24V is very common in the offgrid world. It should be fine for me. So the bike will have to run on 72V :evil:

@ scooterman
Wondering about efficiency with these DC/DCs. Are there considerable losses?

@ nutspecial
Let me know if you find some good solution.
 
Research the entire system before committing to the major components.

Most of the solar battery inverters (that produce 120V AC) accept an input of 48V or 52V. I don't know if that will affect any of your design purchases, just a thought.
 
Interesting, I thought the inverters ran on 24v, which is the common output of some of the larger panels. Or was ten year ago. :roll:

The tiny cheap inverters may still be mostly 12v, the harbor freight stuff. Not sure what big RV's have now days.

It just occurred to me 24v packs can be bought, then they can be 48v,72v for the bike. One bms when you stack em in series to use on the bike.
 
I looked into the step down converters and now realize they won't be realistic for that voltage, and especially current.

Also checked the info on my latest inverter, and can confirm it (~140$ 1500w) is 11-15v input. They're like a controller with set limits to protect circuitry and draws I guess.

Also, that's a good point on LI modules for 12v wouldn't be realistic because of the chemistry voltage VS most inverters lvls. And I know I wouldn't look to use lipo in a residential setting like this even if carefully monitored, so the 24v packs sound good.

https://www.victronenergy.com/batteries/lithium-battery-24v-180ah
But, unless you have alot of ebikes, and/or a very small bank, I would probably stick with lead for the bank.
For perspective, 180ah is still pretty small, but 10x the size of the average (similar volted) bike battery.
I am really curious what it costs though.
 
Greetings,
I have two 24V 10ah battery packs with B.M.S. from VPower. I need to know if they can be used in series for 48v 10ah system.
No response from the company, please help.
 
sure you can in principle gaiacycles.
but i guess the charging will be inconvenient.. do you want to charge each pack separately?! also need to think about balancing between the packs from time to time..
hence my initial question if there are some ideas about a 'variable' bms that works for changeable configurations.

solar contollers up to 48 or 60V are common these days. when the better efficiency mppt type of controller is used the acceptable solar panel voltage range will be bigger and the much cheaper rooftop kind of panels can be used instead of small volume rv stuff.
 
To be fair, you can definitely find solar PV panel systems that output 120V AC, using an input of 12V and 24V DC (sailboat sites have info on this). Higher voltage takes thinner less expensive wire. I have never owned one of the "off-grid" systems, but from reading, it just seemed that 48V was the most common for a cabin.
 
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