A "Virtual Battery" for Mobile Home usage


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Cherry67

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Joined
May 13, 2018
Messages
506
As promised I will describe circuit and Plan of my bidirectinal converter.

I suggest you guys will ask and discuss about it, so i will transfer this building description to a separate thread in electrical section, You all Know his section is for concepts, not for discussions.

Since i had put the first ideas of this issues already in a thread there, i will continue there with the converters building details :
https://secondlifestorage.com/showthread.php?tid=7259&pid=68744#pid68744

I might add, belonging to this section, that the first build is still working in my mobile home, now during one year.

1st Build:

Size: 10s18p (three bicycle packs in parallel)

Electrics battery: 36 V 52 Ah nominal (limited to 4.0 v/cell it is about 46 Ah) Since it is used cells, it might be a bit less

Electrics converter: max 12 Amps Up direction. max 10 Amps low direction. Load voltage 12.8 V, Boost voltage 13.2 V (and higher)

Cycles: The systems has supplied close to 20 kWh to the car, so might be the aequivalent 10+ full cycles.


The second build i did for a friend of mine, which builds a small Mobile home based on a 24 V Car system:

2nd Build

Size: 10s12p (currently two bicycle packs in parallel, possible upgrade to double))

Electrics battery: 36 V 24 Ah nominal (Llmited to 4.0 v/cell it is about 22Ah) Since it is used cells, it might be a bit less

Electrics converter: max 5 Amps Up direction. Max 7 Amps low direction. Load voltage 25,6 V, Boost voltage 26.2 V (and higher)

Cycles: The build is just ready and will start operation next year.
 

Cherry67

Member
Joined
May 13, 2018
Messages
506
A while gone by since i was Here Last Time.
I have been living in the mobile home frequently, and allmost continuously during the last 4 months. The 3 bike battery Pack has done proud, but starts to degrade with each additional cycle.
Last i have about 800 Wh, which should have been 1200, at least.
I guess the bikebatterys may have very different aging, some by time, some by cycling.

For the matters i will build Up 24 V LiFePo. Will report soon.
 
Last edited:

Cherry67

Member
Joined
May 13, 2018
Messages
506
Just to make an update, i built an 8s drin 100Ah LiFePo Cells.
Currenty I am using it, quite A Progress to the ol Block, in Capacity.
 

Oberfail

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Joined
Jun 22, 2021
Messages
241
A while gone by since i was Here Last Time.
I have been living in the mobile home frequently, and allmost continuously die the Last 4 months. The 3 Bike battery Pack has done proud, but Starts to degrade with each additional cycle.
Last i have about 800 Wh, which should have been 1200, at least.
I guess the bikebatterys May have very different aging, some by time, some by cycling.

For the Matters i will build Up 24 LiFePo. Will Report soon.
Which voltage limits do you use for your ebike batteries?
 

Cherry67

Member
Joined
May 13, 2018
Messages
506
Hi, i go very conservative, because in summer i cannot avoid having the Battery fully charged by Solar. So i Use 3,95 V as top Voltage, as Well as 3.3 V lower Limit. There ist hardly usable Capacity below, and the 20 % loss in top in summer are no Problem. Still i have experienced notable, but not documented Capacity Loss.
 

Oberfail

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Jun 22, 2021
Messages
241
If you have some time, it would be interesting if you'd take apart the battery and test each individual cell again to find out which ones are the bad ones.
 

Cherry67

Member
Joined
May 13, 2018
Messages
506
Hi, no, in this Case i used old E-Bike Blocks as they are. The Panasonic Blocks with black silicon are very difficult to Rip apart, and over 20 Blocks i learned that the cells per Block are quite equal, even on undervoltage Blocks. That saves big Lot of Work.
Unluckily, my supply hast ceased, and due to other requirements i will Go to LiFePo, blue cells.
 

Cherry67

Member
Joined
May 13, 2018
Messages
506
Small Update, the 8s LiFePo4 100 Ah works like clockwork.
Absolutely No problems, the (now) 24 V converter to 12 V runs as well like i know it from the previous build.
 
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