Add 36V Battery Block to 48V Battery System

cadric

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May 3, 2018
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107
Hi,

ChrisD gave me a hint last year how he combined a 36V Battery to the 48V Main Battery System.
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.


image_ukvmvj.jpg


So another Idea was to find a bidirectional converter module, but up to now I did not find one fitting the needs of 36V to 48 Volt.


image_tbntzr.jpg


Does anyone have an idea of such an equipment that can deliver maybe 1500W?
Or any other solution that fits the needs to combine 36V and 48 Volt Batteries?

I also asked Chris via PM for a description of his system, maybe that already would fullfill the requirements, but I'm still curious about any other idea.

thanks in advance

cadric
 

OffGridInTheCity

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Dec 15, 2018
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Step up/down at any kind of seriouspower level doesn't sound practical. How many ampsare we talking here?

Mayberebuild the 36v battery packsinto a 48v configuration?
OR
2 parallel systems? - e.g. 2 x Charge Controllers (one to charge 48v battery bank and 1 to charge 36v battery bank) and maybe 2 x Inverters?
 

Crimp Daddy

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Feb 21, 2018
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A good quality step up/down converter will have a 10-20% loss is power conversion... it's pretty significant, along with the cost of the converter.

Its viable for smaller loads, but a poor solution for a pack/system voltage mismatch on a large system.
 

cadric

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May 3, 2018
Messages
107
Hi,

I have 2 PIP5058 that I planned to cascade for the 48V system.
But as the main source now are 36V 10S e-bike batteries I didn't want to take these apart any more,
because that always destroise some of them and aditionally makes a lot of work afterwards.
20% loss is not a problem, because the Batteries are free except the Converter and BMS.

Regards

cadric
 

cadric

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I don't know how much current. I thought about 4 to 6 batteryblocks connected to one dc-,dc convertermodule , so maybe Up to 30 to 40 A. Compareable to the DC Booster Module ChrisD used.
 

Crimp Daddy

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cadric said:
I don't know how much current. I thought about 4 to 6 batteryblocks connected to one dc-,dc convertermodule , so maybe Up to 30 to 40 A. Compareable to the DC Booster Module ChrisD used.

I would use the Victron Orion Isolated DC-DC. They are fully isolated so you can put them in parallel.

https://www.victronenergy.com/uploa...DC-DC-converters-isolated-100-250-400W-EN.pdf

The 48/48-6 (280W model)accept an input voltage of 32-70v, so you could supply that with the 10s battery and ouput stable 48v (adjustable)

Add as many as you need in parallel for the required load.

Note, the larger 48/48-8 380 watt model input range is 40-70v so I would not use that one. I still think its better to just change the battery setup. I have a bunch of 36v stuff, and I get the struggle.
 

cadric

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Hi Crimp Daddy,

But are they bidirektional? I can't see that exactly.
Regards

cadric
 

Crimp Daddy

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cadric said:
Hi Crimp Daddy,

But are they bidirektional? I can't see that exactly.
Regards

cadric

They are not bi-directional... most DC converters (at least the one I know of)are directional.
 

cadric

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107
OK.

Thanks for clarifying.

Regards

cadric
 

Crimp Daddy

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I was thinking the inverter was the load only, and the charging would be handling by a separate solar charge controller.
 

cadric

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May 3, 2018
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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
 

daromer

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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.
 

ajw22

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cadric said:
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.


image_ukvmvj.jpg


[...]
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 smallerconverter (300W?) will be able to provide enough assistance power to keep the 1500W inverter running for hours. But that'lldepend on the battery capacitiesand other factors.

I'd use an Arduino to measure the 48V SoC andPowerMOSFETs 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 softcurrent limits to prevent them from overheating andburning 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 the36V ebike batteries, because they have issues, right? The safe & right thing to do is take apart andtest each cell anway
 

cadric

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May 3, 2018
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107
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
 

ChrisD5710

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Sep 13, 2017
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Hi. :)

I was PMd by "cadric" where he asked me to specify how I did.

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

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 :)

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

:)
 

cadric

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May 3, 2018
Messages
107
ChrisD5710 said:
Hi. :)

I was PMd by "cadric" where he asked me to specify how I did.

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

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 :)

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

:)
Hi Chris,

thanks for your reply.

I'm still working on an optimized solution to extract the cells from the black block.
Best would be to find a creamic forstner drill or milling cutter.

regards

cadric
 

ChrisD5710

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Sep 13, 2017
Messages
162
Q: Are the cells casted in this black goo?

I thought it was plastic spacers, but if the cells are indeed casted in this black hard goo, You are out of luck, sorry.

ChrisD
 

cadric

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Joined
May 3, 2018
Messages
107
No, I have a working solution to extract the cells, but it's a whole lot of work :

https://secondlifestorage.com/showthread.php?tid=7682

and I would like to save this time and work.

Another Idea I have is to only use 7s of this 10s Blocks and combine 2 Blocks to 14S 48V.
I already build a test example and this works.
Problem here is a good BMS.

regards

cadric
 
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