Portable / Solar Rechargeable Battery Pack

Hey all,

Just finished my first project. 3S15P battery pack adhered to a set of solar cells.

The solar cells provide a max 1 amp at 15 volts connected to the pack through a charge control circuit and then into a 3S BMS and finally into my 3S15P battery pack. The pack has about 36 Ah capacity and a 20A max steady current output.

I dont have a specific need for this project, except to serve as an instructional project in building power walls / battery packs. The solar cells will take a while to recharge it full (days), so its a back up pack for sure. (Also, I know the wiring of the panels is dumb. They are 5V .5A cells that are in 3S2P...I accidentally placed the left one upside down, and didnt realize until the glue had already set.)

My next plan is to get a 12V 20 A inverter (something small), so I can use this as an emergency battery pack for a refrigerator. Maybe Ill get a 3D printed waterproof case made, and replace the golf cart battery powering my trolling motor.

Finally, I was going to do a STDP switch to go between output power and solar recharging....before I do that, anyone have good ideas on how I can wire the solar into output power? So if I had a load, I pulled power from the solar array and battery at the same time, but if I turned off the load, the solar power would start charging the battery again?

Kinda proud of it. Its compact and portable, and I thought a fun project!

Very nice! Watch out - it's addictive and before you know it there will be 100(s) then 1000(s) of cells rolling around

I have a 3s16p built for powering a 12v electric fence but I put it on hold after not finding a simple 3s solar charge controller. There are users using a12 v lead acid controller with active balancing. Others jump up the battery to 24 volts but then drop the voltage down for output of the pack.

Was using the 5v solar panels a cheaper way to go or what was motivation over above methods.

Tks

Chablism said:

I have a 3s16p built for powering a 12v electric fence but I put it on hold after not finding a simple 3s solar charge controller.

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Did you look at the semi-famousMPT7210a ? Its cheap and can charge 12v (completely customize-able) from a range of solar panel inputs higher than 12v It has 10a output limit - 10a*12v = 120watts. https://www.amazon.com/RONSHIN-MPT-7210A-Controller-Aluminum-Lithium/dp/B07ZNW82TT

There are lots of youtubes so you can check it out before purchase. I use one for my DIY portable solar generator.

Yes I looked at the MPT7210, My understanding is that it is not compatible with a 12V setup without using a buck converter form a 24V battery (My current battery is 12V).

Are you running a 24v or a 12 v battery for your portable generator?

Sorry not trying to hijack a thread, just wondering the if using a plurality of 5V solar panels is less complex then building a new 24v battery.

Chablism said:

Yes I looked at the MPT7210, My understanding is that it is not compatible with a 12V setup without using a buck converter form a 24V battery (My current battery is 12V).

Are you running a 24v or a 12 v battery for your portable generator?

Sorry not trying to hijack a thread, just wondering the if using a plurality of 5V solar panels is less complex then building a new 24v battery.

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Edited this post to correct my earlier comment here. You're right - the minimum output is 15v per the specs. I mis-remembered/confused the minimum input (12v) with output (15v). MPT7210a accepts 12v-60v input and can reduce or boost the input for DC output anywhere in the range of 15v - 60v. The 10a output is max regardless of voltage - so 150w to 600w output depending on settings (and sufficient input)

It cannot redue. Its a buck converter only and no buck. Note that it also isnt a pure mppt but you set variables where it try to sink to.

Chablism said:

I have a 3s16p built for powering a 12v electric fence but I put it on hold after not finding a simple 3s solar charge controller. There are users using a12 v lead acid controller with active balancing. Others jump up the battery to 24 volts but then drop the voltage down for output of the pack.

Was using the 5v solar panels a cheaper way to go or what was motivation over above methods.

Tks

Click to expand...

If Im totally honest, the 5Volt panels were left over from another project...basically this has been an evolving project to cheaply teach myself the intricacies of using solar power and 18650 to get off the grid.

That said, the charge controller I used is super cheapXY-L10A; 6-60v input and 10A. You can upgrade to the XY-L30A for 30A max.