“Oh, btw...Overkill Solar has an 8s BMS”

[Larry619]

I just watched @Will Prowse latest video for the DIY Titan Solar expansion pack and he threw an “oh by the way” at the very end and my jaw hit the floor.

Overkill Solar has an 8S 120A continuous BMS!!
From Will’s site: https://overkillsolar.com/ product/bms-100a-8s-lifepo4/ ?myboi=187467879

So now my question is, should I get it custom with soldered copper lugs and 8ga wire? They have options for both and I don’t want to do any soldering if they can do it before shipment.

I guess I’m not going for the (now out of stock) Electrodacus BMS and no need to worry about relays.

 

[GMB]

Nice to have another option in the BMS realm. Hope they come out with a 200 amp model at some point. Just a note, you put 120 amp in your description above, but the link says 100 amp.

Overkill Solar has an 8S 120A continuous BMS!!

• Includes a Bluetooth communication module.
• BMS For 8 cell, 24v volt Lithium-iron-phosphate DIY batteries
• 100 amp continuous charge or discharge current
• Low Temperature Charging cutoff at -1c
• Remote shutoff switch
• Fully programmable with IOS app, Android app, or Desktop app

 

[Larry619]

Nice to have another option in the BMS realm. Hope they come out with a 200 amp model at some point. Just a note, you put 120 amp in your description above, but the link says 100 amp.

• Includes a Bluetooth communication module.
• BMS For 8 cell, 24v volt Lithium-iron-phosphate DIY batteries
• 100 amp continuous charge or discharge current
• Low Temperature Charging cutoff at -1c
• Remote shutoff switch
• Fully programmable with IOS app, Android app, or Desktop app

Oops I noticed that after revisiting their site. I thought I heard it 120a on the video but it must be a mistake.

Although, I heard some users really pushing the 4s version beyond 100A. Still, I’m happy to see Overkill has the 8s model. I’ve been wanting something with customizable charge and discharge parameters but with the ease of a Daly BMS in terms of installation.

would you happen to know what the lug options are for? It may determine if I need the 8ga wiring soldered or if I just get the lugs and use my own wiring.

 

[GMB]

would you happen to know what the lug options are for? It may determine if I need the 8ga wiring soldered or if I just get the lugs and use my own wiring.

I assume he is crimping on copper lugs for you in the event that you do not have a way to crimp your own. However, you would need to know that the standard wire lengths would fit your application, otherwise you would be chopping them right back off to make longer wire runs, especially when you start dealing with 8 batteries; depending on how they are arranged.

10 gauge standard wires seem a bit small if you're really going to be pushing large amps through this. The 8 gauge option is a nice touch by them.

Looks promising. Can't wait to start seeing some reviews roll in.

 

[nwillitts]

i bought 2 8s with 8 g wire and lugs.will let you fellers know when i play with them.

 

[Larry619]

i bought 2 8s with 8 g wire and lugs.will let you fellers know when i play with them.

When did you buy and what’s the ETA on shipping? I might be ordering on Monday but I’d like to know what these options are.

I’m assuming the lugs are are what are in the ends of the wires to attach to the battery or load?

 

[nwillitts]

bought them Monday,got them Friday..yes,lugs for battery hook up/load.gonna buy his batteries next.

 

[MrNatural22]

I ordered the Overkill 8s 100amp BMS today and in an email with Steve he said they are shipped free by 3day priority mail. I ordered the 12” 8g wire option on mine no lugs. He answers emails pretty quickly. ?
I didn’t pay enough attention to Wills clearly mentioning they were offered by Overkill and thought they were the big battery stock. My bad ?
I did order the battery in Wills video and the BMS from big battery then realized it wasn’t the one in the video Will clearly said was overkill ? and it being Saturday nobody in the office so I emailed and left phone message to cancel the BMS and not the battery. I’ll call Monday to confirm.
Working outside today This has been a hotter than h€ll day (108deg) of confusion. Glad it’s almost over. LOL

 

[Larry619]

Do you know if I can bolt wires on instead of opting for soldered wires? I saw someone do a bolt on The wires on the 4S version.

 

[Larry619]

I ordered the Overkill 8s 100amp BMS today and in an email with Steve he said they are shipped free by 3day priority mail. I ordered the 12” 8g wire option on mine no lugs. He answers emails pretty quickly. ?
I didn’t pay enough attention to Wills clearly mentioning they were offered by Overkill and thought they were the big battery stock. My bad ?
I did order the battery in Wills video and the BMS from big battery then realized it wasn’t the one in the video Will clearly said was overkill ? and it being Saturday nobody in the office so I emailed and left phone message to cancel the BMS and not the battery. I’ll call Monday to confirm.
Working outside today This has been a hotter than h€ll day (108deg) of confusion. Glad it’s almost over. LOL

Thanks for the info!! I’m ordering one in the morning. I spoke with him on Reddit and he said a lot of orders came in for the 8s ?.

And I better stop complaining about our 85 degree “heat” here in San Diego. ?

 

[Sunny Days]

And here i am with an ANT bms from aliexpress in my cart, allthough the ANT says its 400amps i may consider getting this one just because of shipping! Sad its only 100amps. Leaves me no room for future growth.

 

[Sunny Days]

I just contacted IC GoGoGo and their 400Amp BMS is only 150a with 50a ???charging..... So i tried buying Overkills but he doesnt seem to have shipping to Puerto Rico for some reason.

Sent him an email, id prefer buying from him than from aliexpress since it takes so long to ship..

 

[Mad_Texan]

I've heard a rumor... Still waiting on cells.

 

[MrNatural22]

I've heard a rumor... Still waiting on cells.

Mine came in today. Battery coming Monday or Tuesday. ?

 

[Stewfish]

Couple noob questions for you overkill solar enthusiasts. I live in FL and want to give them my business to support a local business and get cheaper shipping than China.

1.) Can I use 4 of these BMS and watch all 32 cells at once or only one BMS at a time?

2.) If not how could I swap bluetooth to be able to be changed from 1 to another unless each BMS has its own different name and keep track of what I have already seen?

3.) How hard would it be to set up a PC or phone to monitor all 32 cells at once? I plan to build in April and I think I read or saw that they are building a new app/software so maybe I should wait.

I guess worst case I can do 4 usb modules and swap the usb cord to each one, then refresh, or use different com ports. After its running maybe check it every 6 months or so.

Build Plan:
I'm thinking do 24v/8s and wire them 2s2p = 32 cells at 48v. Instead of buying eight 12v BMSs. I'll have probably about 30 to 40 ground mount 250w/36v panels feeding three stacked MPP 48v off grid boxes.

 

[HRTKD]

1.) Can I use 4 of these BMS and watch all 32 cells at once or only one BMS at a time?

No. At least on the Android app, it's one BMS viewed at a time. Kind of sucks.

2.) If not how could I swap bluetooth to be able to be changed from 1 to another unless each BMS has its own different name and keep track of what I have already seen?

Using the app, you can name each BMS. Also, the bluetooth "dongle" lights up when it is active.

3.) How hard would it be to set up a PC or phone to monitor all 32 cells at once? I plan to build in April and I think I read or saw that they are building a new app/software so maybe I should wait.

The PC uses a different interface. I don't use that, so I don't have any experience with it. My guess is that the serial cable (is it serial?) connects to one BMS at a time. It's not on a bus. But that would be cool to have it on a bus.

I guess worst case I can do 4 usb modules and swap the usb cord to each one, then refresh, or use different com ports. After its running maybe check it every 6 months or so.

Build Plan:
I'm thinking do 24v/8s and wire them 2s2p = 32 cells at 48v. Instead of buying eight 12v BMSs. I'll have probably about 30 to 40 ground mount 250w/36v panels feeding three stacked MPP 48v off grid boxes.

If it was me, I would go 16s to get 48v and find a different BMS. As much as I'm satisfied with the 4s Overkill Solar BMS, I don't care for putting BMS batteries in series.

 

[Stewfish]

No. At least on the Android app, it's one BMS viewed at a time. Kind of sucks.



Using the app, you can name each BMS. Also, the bluetooth "dongle" lights up when it is active.



The PC uses a different interface. I don't use that, so I don't have any experience with it. My guess is that the serial cable (is it serial?) connects to one BMS at a time. It's not on a bus. But that would be cool to have it on a bus.



If it was me, I would go 16s to get 48v and find a different BMS. As much as I'm satisfied with the 4s Overkill Solar BMS, I don't care for putting BMS batteries in series.

I can't find a legit 16s BMS that someone hasn't said sucks except for overkill.

All the Alibaba stuff is under rated wires for 16s with more than 100a, sometimes even 12g vs overkills 8g.

Chargery has relays that get 135 deg F and always have a draw on them like leaving a car dome light on.

electrodacas, doesn't do 16s,

Some BMS cost more than the battery

 

[HRTKD]

If you want to play with the high voltage, you're going to have to pay a little more. You could keep the voltage to 24v instead.

 

[Stewfish]

What an I missing? I don't understand how 4s 100a is usable, that's only 100ax12v = 1200watts so you can only basically run a 1000w inverter? So the BMSs must be able to be added in series or parallel. People keep saying don't do Parallel, but how do you get a basic 12v 2000w inverter running then?

How do I calculated usable watts?
8s + 8s + 8s + 8s = 32 cells at 48v with 400amps = 19200watts or is that 100a @24v = 2400w x 4BMS = 9600w the system came put out at one time max?

If its 19200 watts - with four 4k inverters two stacked for the house and two to feed the RV/mother in law/shop when needed = 16000w so that seem pretty future proof and 3200w below the max. Then I will have two extra inverters that are only used when family visits or I am in the shop so I can quickly swap out a broken MPP all in one.

What about at 4s?
If I buy 8BMSs = 4s + 4s + 4s + 4s + 4s + 4s + 4s + 4s= 32 cells at 48v with 800amps = 38400 watts? So eight 4k inverters = 32000? Or is it 100a x 12v= 1200w x 8BMS= 9600 watts?

With 48v the end result is my cableing on a huge property vs something small like an RV is cheaper, and in my opinion safer at 48v with less amps vs lower volts and way more amps. It's why 600v goes to your house and then down to 110v x two hot bars. bc 110v would never make it that far. To the nearby transformer I think its 11k, 16k, or 60k volts I can't remember. Higher volts = less heat bc of less amps. My shed, shop, RV pad, are not right next to my house.

 

[wings2004]

@Stewfish I'm currently using a 1200w system for a backup powerwall system for my computer and 3d printers. Currently that's 12v and I'm upgrading to a 24v system. I can't integrate with my house wiring due to renting and these work for my purposes of having large capacity backups for critical demands.

Your math kind of hurts my brain a bit so let's try to step back a bit. Let's assume you're cells are 100Ah with a 1C discharge rate or 100A/hour), 1s1p at LiFePo4 is 3.2V. A nominal 8s1p (which means 8 in series 1 parallel) is 24v at 100Ah. . Putting 2x 8s1p systems in series would be 16s1p at 100Ah nominally 48v. 1C discharge rate of 100A/hour or 4800W/hour.

Now to extrapolate to a more real situation, 32x 280Ah cells (often at .5c discharge rate or 140A/hour max per cell) this is a total of 8960Ah of batteries in some combination of cells in series and parallel. Let's say it's 16 series 2 parallel or a nominal 48v 560Ah capacity. This would often be discharged at a Max 280A or .5c discharge rate based on the batteries.

Now you think about the BMS. You want your BMS to be able to cover all the power you are going to draw from that system. When you have sets in parallel that is where you add. In the previous example, a 16s2p, if you used 100A BMS with 2 in parallel, your system could draw up to 200A.

This kind of works but really you should have one BMS to cover the battery bank. The reason you want one BMS is because if you have 2 BMS in parallel,let's say 2x 100A each supporting 16s for a total load of 200A at 48V or 9600W, and one of the BMS' trips due to a low cell, now that entire load needs to be serviced by the one battery and BMS so you are likely to over draw. The ideal solution is to have a bms that is sized for your battery and intended load but if you must putting 2 in parallel to increase draw is a reasonable option. I say one battery and BMS because you don't want to parallel BMS on the same battery bank because then you have the possibility of one BMS getting out of sync with the other BMS when it comes to charging profiles and cut off currents and voltages.

I hope this helps some. In my mind if you have 32 cells and a 16s BMS you would want to have a 16s2p battery bank with a BMS that covers the max current needed up to say a .5C discharge rate to keep the batteries happy.