What do you want in a Battery Pack (+additional hardware) ?

[Twan]

Hi fellow battery enthusiasts,

Every now and then I make a custom 18650 li-ion battery pack to provide hobby projects with a (mobile) power supply. Just like me, you might have found tons of guides and information on the web on how to build your own pack. In my opinion the variety of information and guides is too large. - Is this a problem that you recognize?

Something like standard or modular configuration seemed useful to me.

That is why I am curious, what do you need a (custom) battery pack for?
Functional:
- Camping
- To work in the garden
- A day out
- E-bike
- Powerwall

Or else; What are features you would like to see attached to a small or larger battery pack?
Technical:
- 12V, 24V, 36V, 48V or more?
- DC output
- AC output
- Solar Input
- USB Quick Charge
- USB PD
- LED
- etc...

Mechanical:
- Weight
- Volume
- Shape

All input is welcome.

From this input I want to make a design that others could possibly use as well.

Thanks

 

[cak]

I have been building ammo can batteries after being inspired by seeing several other folks doing batteries in ammo cans. I am still prototyping but I like the format and think it is very versatile. The main version I am building is a 24vdc 7s26p with two sets of Anderson pp 45a connectors and a USB C PD plug(also has a USB A but whatever). My goal is 50amp nominal 90 amp max but one needs good cells for that. My intended use is as a portable power station for a wall tent or similar powering dc lights phones and misc, or plug in an inverter for a mobile power tool station, or use it to power an electric mower walking tractor atv... I am hoping for one pack design that I can use in lots of situations for easy logistics and if I need higher voltage for bigger tools I can put 2-3 of these "Ammobats" in series. I have also calculated that I could do a lot of different voltage configurations in the same ammo can container for specific uses. 15s13p to power my Dewalt Flexvolt table saw, 14s13p for 48v situations where you can't fit two Ammobats in series, 20s8p for 72v(80 or 82v max) for higher power motors or certain brand tools.

I am also thinking about building a larger powerwall but still considering what design would fit my situation. Option 1; just parallels lots of Ammobats. Option 2; 100 cell 5x20 packs in series of 7 or 14 depending on desired system voltage. Option 3; 5-6 cells connected in parallel that slot into plastic 18650 holders setup with fuses connecting lots of the mini packs in series and parallel for a large 7 or 14 s powerwall. Each option has its tradeoffs.

Overall I feel like most folks who are DIY building batteries are inclined towards highly customized projects but that being said there does seam to be some basic standards that many folks use in designing and building largely influenced by available supplies and amperage needs.

 

[OffGridInTheCity]

In the beginning (3yrs ago) I was enamored with replacing lead-acid, then saving money.

- 1st - a 12v nominal 18650 (3s) battery in a smaller portable power supply was not so good - mismatch of voltage range!
- 2nd - 7s 18650(s) work great in my APC UPSs. The APC UPS efforts work but it was not the 50% 'savings' I imagined... and a fair amount of effort... but it was good learning exercise.
- 3rd - I did a 50lb 'portable' solar generator with 3.5kwh in a cooler with wheels... and it was indeed a fraction of the price.
- 4th - A large 18650 powerwall for my home. Fantastic savings! and it works!
- 5th - A 13kwh battery bank for a cargo trailer -> camper conversion. Fantastic savings and it works!

Today - I've started buying these cheaper LifePo4 units for 12v lead acid replacements - for my generator starter motor, as lead-acid replacement for mobility scooter. Prices are good (not so much savings for DIY) and way easier

For powerwall and RV/trailers ... there are huge $ savings in DIY!

For solar generators - there can be significant $ savings.

 

[italianuser]

This is one of my hot topics in these days. My application is powerwall.

For me the main features around my coming-soon battery packs derive from the fact I don't have a smart BMS (I have 4 entry level Daly over-voltage/over-current protection and balancing BMSs), so I must use Arduino/ATTiny/ESP boards to make a safe environment around the battery. So my needs involve the environment design of the place where batteries will stay.

Note:
"monitoring" is about: measuring a value and transporting it to a control system;
"controlling" is about: a system which can make actions based on values coming from "monitor".

1) Battery voltage monitoring, for each series in the pack (*);
2) Battery temperature monitoring: for each series in the pack (*); maybe I'm a bit paranoid but I'd really make a thermal moving camera on X-Y axis to monitor a whole pack;
3) Battery Enclosure temperature monitor and control. This system should have a backup system because it's critical. Its made of fans, temperature sensors, 20W heating system ( and 20W cooling system;

(*) Ye, I will buy a smart BMS LOL

 

[floydR]

3) Battery Enclosure temperature monitor and control.
https://www.ebay.com/itm/163868037674with two of these you could have one for heater, and one for cooling fans. They display the temperature if you need a wifi/ethernet solution you could use a 1 wire network with a RPI using DS18B20 sensors Use the RPi to trigger relays. if you use this method may as well use the one wire network to add a lot more Ds18b20's, 52 would give you three per parallel group in one 14S battery.
Better yet DS2438z temperature and voltage.
Later floyd

 

[italianuser]

3) Battery Enclosure temperature monitor and control.
https://www.ebay.com/itm/163868037674with two of these you could have one for heater, and one for cooling fans. They display the temperature if you need a wifi/ethernet solution you could use a 1 wire network with a RPI using DS18B20 sensors Use the RPi to trigger relays. if you use this method may as well use the one wire network to add a lot more Ds18b20's, 52 would give you three per parallel group in one 14S battery.
Better yet DS2438z temperature and voltage.
Later floyd

Very nice device, appreciated that; very small footprint, too. The relay on that board is AC, suppose it would work with low wattage DC fans.

I'll be using an Arduino and a transistor to power (possibly) all of the 18B20s. One Dallas for each series makes 14 x 4 packs = 56 sensors. At 4mA current each makes 224mAh, I'll use a 400mAh transistor. My homemade platform should be able to manage this extra data flowing around the 433MHz band and then going to a data collector (a web API) via an ESP8266. For Wolf's (and the forum's) pleasure I'll add Logstash and Graphana sooner or later.


[Arduino with a ESP8266 connected on TX/RX pins; Arduino receives data from all sensors in the house via 433MHz and sends it to a Web API thanks to the ESP8266 - web real-time charts here - Raw data is shown on the display, message protocol uses an 18 byte fixed message size]

EDIT: to not go too much OT, Additional hardware, yes please, monitoring & control using microcontrollers! LOL

 

[floydR]

Very nice device, appreciated that; very small footprint, too. The relay on that board is AC, suppose it would work with low wattage DC fans.

The one sitting on my desk is 20A 14VDC, 20A 125VAC SRA -24VDC-AL

later Floyd