60Ah LifePO4 battery project

Jordi

Solar Enthusiast
Joined
Oct 13, 2020
Messages
113
Dear all,

I would like to introduce you to my new project regarding batteries build up so you can give me feedback and save me some errors. In exchange I will keep you updated of purchases and the experience of assembling the whole system.

The main goal is: To build a 60Ah 12V (4S) LifePO4 battery that can be suitable for manual transportation and that in combination with an inverter can supply max. 500W continuously and comfortably. Expect to use it often at the range 100-200W. Purpose is recreational, so I want to keep expenditure as low as possible.

For that I believe I require:
- A source of energy: 100W 12V solar panel (I already have)
- A charge regulator 50A at least (May already have)
- 4 cells LifePO4 60Ah 3,2V
- BMS 50A at least (with BT for battery control and learning)
- Cables with cross-section between 10-25mm2
- A DC/AC inverter for at least 500W continuous discharge (I already have)

The rough diagram of the system is this one.
1633074031838.png

Facts and expectations:
- The battery will have 768Wh from which I expect to be able using 80% safely by selecting a proper disconnect discharge voltage.
- I will box the battery but leave big openings on the box to save adding a ventilator. Expect that natural cooling will be enough.
- I expect that so long the BMS stays connected to the battery, the data collection won't be interrupted or reset.

Questions:
- You always recommend the use of fuses. Should I put one between the battery and the regulator? Or you recommend another position? Could you suggest me a fuse to buy? I would like either a very cheap one or a reusable one (If they exist for such currents...)

- Regarding the BMS, I think a Dali one will do as many of you seem to have good experiences with it. Opinions? I have also found a BMS from Aliexpress that looks exactly the same but the brand is Southrol (https://es.aliexpress.com/item/1005002847675894.html?spm=a2g0o.cart.0.0.3e363c0032zVul&mp=1). The 60A model costs 17 euros less with same features. Any experiences with the brand? Southrol does not appear in the forum.

- I have 10 meters of cable with 2,5mm2 cross section, is it a feasible idea that I use 4 cables properly welded on the edges to achieve the required 10mm2 cross section? That would save me some money.
 

DThames

Photon Sorcerer
Joined
Nov 22, 2019
Messages
1,429
Suggest you consider,
Battery "cells"
BMS
Bluetooth

These are solid products. I have no connection to BatteryHookup.

Well, I see you mentioned Euros, so maybe not helpful for you.
 

upnorthandpersonal

Administrator
Joined
Dec 25, 2019
Messages
2,247
Location
63 degrees North, Finland
You always recommend the use of fuses. Should I put one between the battery and the regulator? Or you recommend another position? Could you suggest me a fuse to buy? I would like either a very cheap one or a reusable one (If they exist for such currents...)

You want at least a breaker that can act as a disconnect between your charge controller and battery. Definitely put a fuse between battery and inverter. I would only recommend Class-T type fuses (yes, they're expensive), but if you know what it means, ANL fuses can work too.

Asking 'which BMS?' on this forum will get you as many suggestions as there are BMS's out there. That Dali will do, an Overkill (JBD) is another popular choice.

- I have 10 meters of cable with 2,5mm2 cross section, is it a feasible idea that I use 4 cables properly welded on the edges to achieve the required 10mm2 cross section? That would save me some money.

You can, but it's not something I would recommend. Is this stranded or solid core?
 

Jordi

Solar Enthusiast
Joined
Oct 13, 2020
Messages
113
Suggest you consider,
Battery "cells"
BMS
Bluetooth

These are solid products. I have no connection to BatteryHookup.

Well, I see you mentioned Euros, so maybe not helpful for you.
Thanks for your suggestions. It is indeed a solid proposal, only that for learning purposes I want to use LifePO4 as I already have a smaller 18650 battery. I am mainly a hobbyist. Also, with Li-on cells I only have 1C continuous discharge versus the 3C from LifePO4, something that for a small battery makes an important difference I believe. Thanks for your time, I consider the proposal for next project.

You want at least a breaker that can act as a disconnect between your charge controller and battery. Definitely put a fuse between battery and inverter. I would only recommend Class-T type fuses (yes, they're expensive), but if you know what it means, ANL fuses can work too.

Asking 'which BMS?' on this forum will get you as many suggestions as there are BMS's out there. That Dali will do, an Overkill (JBD) is another popular choice.



You can, but it's not something I would recommend. Is this stranded or solid core?
Thanks for your advice; I do see indeed that this type of fuse is significantly more expensive. I will investigate the differences and consider it as a possibility.

About the BMS, then let it Dali be.

About the cable, it is solid core, that is why I thought that with some entanglement and thermo-sealers I can achieve some sort of thicker cable. At the end, so long there is good contact at the beginning and the end (I will use my spot welder), the rest matters less I believe.
 

Smokin

Solar Enthusiast
Joined
Sep 8, 2021
Messages
130
2 port BMS.
I use this one on my small packs. They have the leds that show balance mode.

This breaker trips at 50 amps DC. i use them on my small packs more as a cutoff switch that for protection. I have been using them on my ebike builds for years. Their so cheap at lowes.
 
Last edited:

DThames

Photon Sorcerer
Joined
Nov 22, 2019
Messages
1,429
Thanks for your suggestions. It is indeed a solid proposal, only that for learning purposes I want to use LifePO4 as I already have a smaller 18650 battery. I am mainly a hobbyist. Also, with Li-on cells I only have 1C continuous discharge versus the 3C from LifePO4, something that for a small battery makes an important difference I believe. Thanks for your time, I consider the proposal for next project.


Thanks for your advice; I do see indeed that this type of fuse is significantly more expensive. I will investigate the differences and consider it as a possibility.

About the BMS, then let it Dali be.

About the cable, it is solid core, that is why I thought that with some entanglement and thermo-sealers I can achieve some sort of thicker cable. At the end, so long there is good contact at the beginning and the end (I will use my spot welder), the rest matters less I believe.
Not sure how Li-ion came into the thread but okay. I thought you wanted LiFePo4, which is what the link was to. Those 100ah cell packs are solid, getting above rating consistently (if you happen to be in the US)
 

Jordi

Solar Enthusiast
Joined
Oct 13, 2020
Messages
113
Dear all,

I want to give you an update on latest events. Four LifePo4 cells 60Ah and a smart Dali BMS 60A have been ordered at Aliexpress. Following the advice of opnorthandpersonal I will also order soon 2 ANL fuses which cost only around 2,50 euros each.

Together with a solar charge controller that I already have for 10A; I aim to build something like the diagram below.
1633692932788.png

Please note the position of the fuses and let met know If I should use 60amp fuses according to BMS max output or If I may use 80-100amp. The idea of using 80-100amp is that I can (in counted occasions) by-pass the BMS to feed the full 750W that the inverter can offer; also because I wonder whether peak consumptions at the start of a device or a few seconds surge can directly blow the 60A fuse without being necessary.

You will also see that I am by-passing the solar charge controller. This is because I do not want to buy a new one and because anyway, the BMS (which happens to be the smart model) will already cut off the battery at discharge voltage. I will however use the solar charge controller to stop the charging If battery is full and as a second layer of protection.

Once again, comments and feedback is much appreciated!!
 
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