Building first battery

[Rope103]

This will be my first battery/ solar power station I have ever built and want to get some input to make sure this will work before I buy everything and it blows up in my face. Please let me know if this plan is dangerous, especially connecting the split wires together. These 2 batteries are from 2 almost new identical power stations that I fried the circuits on, both still have a voltage of around 13-13.5 volts so I assume they still work. The plan is to connect these two 500 wh LiFePO4 batteries together in parallel using the xt60 parallel connectors connected to the two reds and 2 black xt60s. Then connect the Y splitter connectors to each side. Then take the XT60 male to banana and cut off the banana ends and strip some of the wire to expose it. Then twist the red and black together on the separate cables turning the 4 wire into 2, one coming from the original black wires and red wire from the battery. Then I will connect these twisted wires to my renogy 10A charge controller(I know my photo has a 30A, I’m using a 10A). Now back to the other 2 unused wires on the Y splitter. On each one I will connect an xt60 to O ring connector and then connect those to the 700W pure sine inverter. Like the charge controller I will have four wire (2 red 2 black) so I will connect the red and black to each other to create 2 O rings that I can connect to the inverter. The solar input will be a 100watt solar panel. (yes I do understand that doing it this way will make solar charging the only way to charge the battery.)

 

[Tomthumb62]

What BMS do those batteries use?

 

[chrisski]

You lost me on the description of twisting the wires together. Makes me think you are using wire nuts for this.

That does not look like a 1000 wh battery pack when both are added together.

You'd need to check the wire size to ensure the wires are thick enough for the inverter. The wire does not look that thick either, so whatever the gauge of the wire is, ampacity would be limited to that. I think it may be 12 gauge , so perhaps 20 amps max, or about 240 watts per each of the two batteries, but if its 14 AWG would be less.

 

[Supervstech]

Far more info is needed about the batteries you have.

 

[Rope103]

What BMS do those batteries use?

I assumed I could ignore the BMS on the batteries since it’s being connected to a charge controller and an inverter. Is this assumption wrong?

 

[Rope103]

Far more info is needed about the batteries you have.

They came out of 2 identical 550 wh (advertised) LiFePO4 power stations that I fried the circuits on. Again the batteries appear to still be in working order from testing in my multimeter

 

[TacomaJoe]

I assumed I could ignore the BMS on the batteries since it’s being connected to a charge controller and an inverter. Is this assumption wrong?

The BMS is the safety net to protect the cells.

 

[Rope103]

You lost me on the description of twisting the wires together. Makes me think you are using wire nuts for this.

That does not look like a 1000 wh battery pack when both are added together.

You'd need to check the wire size to ensure the wires are thick enough for the inverter. The wire does not look that thick either, so whatever the gauge of the wire is, ampacity would be limited to that. I think it may be 12 gauge , so perhaps 20 amps max, or about 240 watts per each of the two batteries, but if its 14 AWG would be less.

I’m twisting the wires together because the xt60 connectors that I could find always split into 2 wire, even though the battery has one positive and one negative once I connect the initial parallel adaptor. I don’t want them to split because I’m trying to keep one positive wire and one negative wire.
The batteries come from 2 550 wh (advertised) LiFePO4 power stations that I fried the circuits on. I took the batteries out of the power station. They appear to be multiple cells in metal casing connected together.

All the wires that I will use are 10AWG.
The main point of this project is to create a way to safely charge my other power stations via solar panels. 200 watts would be all I need. Also it’s a good way to get me into this “world” a good starter project I thought. And obviously it would be nice to have to use it for other stuff if I need to. I just want make sure that this will not blow up

 

[Rope103]

The BMS is the safety net to protect the cells.

Does the charge controller not act as one? I don’t see BMS cables coming from typical fishing/car batteries that just have the 2 nodes

 

[Rope103]

Does the charge controller not act as one? I don’t see BMS cables coming from typical fishing/car batteries that just have the 2 nodes

Does the charge controller not act as one? I don’t see BMS cables coming from typical fishing/car batteries that just have the 2 nodes

Would something like this work as a charge controller and mppt?
60A MPPT Solar Charge Controller, 12V/ 24V Solar Panel Battery Intelligent Regulator with Dual USB Port, LCD Display and Timer Setting ON/Off Hours https://a.co/d/fEZ22Mj

 

[Rednecktek]

You'll want a pair of BMS's for those. That bundle of white & red skinny wires is your balance leads most likely. Get a couple simple JBD 4s units from Sirko and get those involved. That's also going to take care of the negative wires as the BMS is going to have 2 terminals on the board for those negative wires.

Would something like this work as a charge controller and mppt?
60A MPPT Solar Charge Controller, 12V/ 24V Solar Panel Battery Intelligent Regulator with Dual USB Port, LCD Display and Timer Setting ON/Off Hours https://a.co/d/fEZ22Mj

Nope, that's a cheap PWM controller trying to rip you off. A true MPPT is going to be in the $100+ range and (usually) doesn't have USB ports, that's a dead giveaway that it's fake.

 

[Skypower]

Those small wires need to be attached and the big black negative to a bms. Those small wires monitor the cells and the bms cut off the flow from the BMS negative load wire as needed. You would need two bms’s for two batteries unless you open the packs to put more cells in parallel. Look up bms wires wiring diagrams. Fuses, low flammable assembly area and a combination ionic and photoelectric smoke detector would be wise.

 

[Skypower]

As a word of warning. Those small wires go right to the cells and should they short together in any combination, you will have glow worms, smoke and fire in that order.

 

[Rope103]

Those small wires need to be attached and the big black negative to a bms. Those small wires monitor the cells and the bms cut off the flow from the BMS negative load wire as needed. You would need two bms’s for two batteries unless you open the packs to put more cells in parallel. Look up bms wires wiring diagrams. Fuses, low flammable assembly area and a combination ionic and photoelectric smoke detector would be wise.View attachment 164679

This is starting to sound like a bad idea, both economically and safety wise. So on to the next part, how do I dispose of these/ do you think someone on this forum would want them?

 

[Rednecktek]

You mail them to me! PM me if you're looking to get rid of them cheap!

 

[Tomthumb62]

Does the charge controller not act as one? I don’t see BMS cables coming from typical fishing/car batteries that just have the 2 nodes

No the charge controller doesn’t act as a BMS. And the car batteries you’re referring to are lead acid, which don’t require a BMS.

You NEED a BMS for safety. EDIT: You need two BMS, one for each pack.

Don’t skip out just yet, you’re over halfway there!

 

[Supervstech]

Does the charge controller not act as one? I don’t see BMS cables coming from typical fishing/car batteries that just have the 2 nodes

No.
A bms is required to monitor and prevent catastrophic cell damage from cells out of balance.
All a charge controller does is monitor high and low pack voltage.

 

[chrisski]

Fun part of attaching the BMS would be figuring which wire goes to which cell in which order. I think there’s about 50 ways those four wires could be arranged. Not undoable, just need a multimeter for it.

Black wire to BMS wire reading around 3 volts plus or minus a half volt, then from that wire to the next one.

If the cells are low voltage, to find the order of the wires you could charge without a BMS, but at a voltage much less than charging like 11 volts or 12 volts. The BMS prevents runaway cells, over and under voltage.

If you take precautions, you could continue with the project.

 

[Rope103]

No the charge controller doesn’t act as a BMS. And the car batteries you’re referring to are lead acid, which don’t require a BMS.

You NEED a BMS for safety.

Don’t skip out just yet, you’re over halfway there!

Ya I don’t won’t to give up, but I was really trying to stay inside the $200 range and with what I’m hearing it’s gunna be more like $350

 

[OffGridForGood]

Don't Bail!
You going to miss out on a great learning experience!