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Add 36V Battery Block to 48V Battery System
#11
I was thinking the inverter was the load only, and the charging would be handling by a separate solar charge controller.
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#12
No,

I don't want to rearange my whole system, all my Pannels are and future ones will be connected to my two PIPs.
So the 36V Bank should just be added to the system.
It's ok for me to buy a bms and DC converter every time I add new 5-6 Battery blocks to my System, that is still less work then taking them apart.

regards

cadric
1. Grid-Tie System 09.2017 16,5kWp:  55 x 300Wp BenQ, SMA Tripower 15000-TL30 (18-east/17-south/20-south)
2. Offgrid System 09.2019 7,5 kWp: 25 x 300Wp Solarworld (5x( 3S + 2S )), 2x PIP-5048MS, Batrium WM4, 1st Battery Bank: 840 cells in 14S60P with 80Ah cap in use, 2nd Batterybank 840 cells in14S60P with 90Ah in use, more to be build.
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#13
To be honest isnt it easier to rebuild the battery or even better sell them and buy ones that fit? It will be far cheaper long term than looking into bi-di converters that actually work decently. They basically need to be programmable so the energy only flows during certain conditions

Have you drawn down on a paper when energy should flow as an example? In what direction and so forth? If you do that you realize that it can be done pretty complex. Yes it can be done simpler as well but then y ou end upp with uneven wear.
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
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#14
(09-16-2020, 01:12 PM)cadric Wrote: The short description is using a dc stepup module for loading the 48V Battery with the 36V one.
I thought about it and wonder how to load that 36V battery again.
I don't think that connection a step up in one direction and a step down module in the other direction is the right way, at least not without switching between them.



[...]
Does anyone have an idea of such an equipment that can deliver maybe 1500W?

I understand the 48V is the main system with the charger/inverter, and 36V is the supplemental battery..?

Pretty sure the idea is to only switch ON the 48V->36V buck converter when the 48V battery goes above say ~70% SoC.  And only switch ON the 36V->48V buck converter when the 48V battery drops below say ~30% SoC.
With these working margins (SoC 30%~0% range), a much smaller converter (300W?) will be able to provide enough assistance power to keep the 1500W inverter running for hours.  But that'll depend on the battery capacities and other factors.

I'd use an Arduino to measure the 48V SoC and PowerMOSFETs to switch the converters.  And add some more logic to avoid needless conversions, like 48V->36V when solar is not providing much/any power, 36V->48V when solar is providing a lot of power, etc.
The converters need to have soft current limits to prevent them from overheating and burning out.


It's a lot of work for a rather inefficient system.  I also strongly suggest you take the 36V batteries apart and expand on the 48V batteries.
Besides, you're getting the 36V ebike batteries, because they have issues, right?  The safe & right thing to do is take apart and test each cell anway
Modular PowerShelf using 3D printed packs.  60kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#15
Thanks Guys,

for your input.
Of all the e-Bike batteries I got, minor were bad, mostly the BMS.
Just now, from 15 tested, some were over 3 V completely, some were 0 Volt,
but I was able to reload them, on one Block  4 Cells didn't take any Power.
So in general they are very good quality.

Taking them apart is done atm with an 18mm milling cutter, not all cells survive this.
Then I drag them out from the positive side with a plasic pipe.
All this make a lot of waste.If I would be able to get rid of this black mass, that would really solve some issues.

But I see, it was not such a glorious Idea to put them into the system.
Thanks again for cleaning my Brain.

regards

cadric
1. Grid-Tie System 09.2017 16,5kWp:  55 x 300Wp BenQ, SMA Tripower 15000-TL30 (18-east/17-south/20-south)
2. Offgrid System 09.2019 7,5 kWp: 25 x 300Wp Solarworld (5x( 3S + 2S )), 2x PIP-5048MS, Batrium WM4, 1st Battery Bank: 840 cells in 14S60P with 80Ah cap in use, 2nd Batterybank 840 cells in14S60P with 90Ah in use, more to be build.
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#16
Hi. Smile

I was PM´d by "cadric" where he asked me to specify how I did.

First, the previous message from "ajw22" pretty much hit it on the spot Smile

At the time I operated my system from  48 Volts 750 Ah Lead Acid.

Li Ion cells were sparse and getting 1400 working cells seemed a long time project and even 1400 cells would only give me 200 Ah, so switching to Li Ion was not an option.

Having collected the first 1000 good cells I started building 10 banks each 100p.

Winter rapidly depleting my Lead Acid bank gave me the idea of using the Li Ion as a reserve that could give the lead acid battery  a boost.

The booster was able to transfer 500 Watts, and apart from needing an extra cooling fan it was steady.

When the Lead Acid was at float I tried to recharge the Li Ion with one of these new buck power supplies and I soon found out that the two breeds should never be left connected. they simply kill each other.

Bill: One new booster and one new buck power supply. So now I know Smile

This arrangement got me through the winter of 2018.

Feeding a 48 volts inverter form 36 volts through a booster is not a good idea. The largest booster I have come across is 1000 Watts or 48 Volts 20 Amps, not nearly enough to feed the PIP 4050.

As "ajw22" points out, You need to take the e-bike packs apart to sort the good cells from the bad.

Re: E-bike battery packs, the black mass, do You mean cell spacers? No problem, the recycling station accept these as soft pvc and the casing as hard plastic. Sort the nickle strip remains into "small combustible", and the screws as metal. This works for me, but make sure to correlate this with Your local recycling station.

Best of luck from Denmark and

ChrisD

Smile
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