4000 watt Inverter on 12 V?

[Forbisher]

Interesting. Yeah, that's a tough one, I don't have a ton of money to play around to figure it out. I received my at 3.8v, so fully charged from the Electric Car Part Company (Will's primary suggested Fortune cell dealer).

3.8V is overcharged.
3.65V is full or 14.6V for a 12.8V battery.
10V is empty.

EDIT. Hopefully you are reading the voltage incorrectly! .

 

[Gazoo]

I received my at 3.8v, so fully charged from the Electric Car Part Company (Will's primary suggested Fortune cell dealer).

That's interesting. Did they say anywhere they ship the cells fully charged? And 3.8 volts? What does the spec sheet say about the max charge voltage. I am not familiar with those cells...just know they are available.

EDIT: I saw on the website they are to be charged to 3.65 volts. They should not have been shipped with that high of a SOC and they were overcharged to boot. What are you using to measure the voltage?

 

[Devin82m]

That's interesting. Did they say anywhere they ship the cells fully charged? And 3.8 volts? What does the spec sheet say about the max charge voltage. I am not familiar with those cells...just know they are available.

EDIT: I saw on the website they are to be charged to 3.65 volts. They should not have been shipped with that high of a SOC and they were overcharged to boot. What are you using to measure the voltage?

Oh joy. I'm using my cheap Klein multimeter testing each cell individually. I haven't bothered connecting them all together since I don't have my BMS yet. They arrived Friday.

 

[Gazoo]

I would contact them and ask they why they were overcharged and shipped that way. Test the capacity when you get your BMS. They are probably fine but it's my nature to be skeptical.

Assuming your meter is reasonably accurate I would discharge the cells to a lower voltage. It doesn't take much and the voltage will drop fast.

 

[Forbisher]

Oh joy. I'm using my cheap Klein multimeter testing each cell individually. I haven't bothered connecting them all together since I don't have my BMS yet. They arrived Friday.

A LFP cell or battery charged to full at 3.65V or 14.6V for four 3.2V nominal cells in series will have the voltage settle to say 3.4V or 13.6V over a few hours so how could your fortune cells be still at 3.8V after days of shipping to you and Friday?

LFP batteries are usually shipped at around 3.2V I think due to safety regulations.

 

[Gazoo]

A LFP cell or battery charged to full at 3.65V or 14.6V for four 3.2V nominal cells in series will have the voltage settle to say 3.4V or 13.6V over a few hours so how could your fortune cells be still at 3.8V after days of shipping to you and Friday?

LFP batteries are usually shipped at around 3.2V I think due to safety regulations.

Good point. After I parallel top balanced my EVE cells I let them sit for a couple of days. They were all above 3.5 volts when I disconnected them to hook up in series. But still 3.8 volts doesn't sound right to me either. The cells would have to been severely overcharged to settle at 3.8 volts after a few days and I think that's unlikely. I think something else is going on here.

 

[Devin82m]

I would contact them and ask they why they were overcharged and shipped that way. Test the capacity when you get your BMS. They are probably fine but it's my nature to be skeptical.

Assuming your meter is reasonably accurate I would discharge the cells to a lower voltage. It doesn't take much and the voltage will drop fast.

I looks like I was wrong, think I got the memory confused with my ham radio gear which is 13.8v. I emailed them too, so look more stupid. Nonetheless 3 tested as 3.28 and one as 3.25. I did ask them how they store them in their warehouse and why they ship at full charge instead of at the standard 50%.

 

[Devin82m]

Moving on... (Homer disappearing into hedge)

 

[curiouscarbon]

it’s all good buddy ?

 

[Devin82m]

OK, now that I figured out I don't know anything about LFP batteries, I'm going to go ahead and order an OverKill Solar 12v BMS so I can start using it, I will try to buy another pack in the coming month and a 24v BMS to make a 24v pack. I guess I will just start running it down to 50% then back up to full again for now until I setup the solar panels and start using it actively to power my home office.

So with that said, more questions.

1. Using a 1500 watt inverter, what size cables should I use for a 12V system. Then what should I switch them out for for a 24V system (if needed since I will most likely need the larger gauge for the 12V)?

2. Will my 15 Amp Victron Blue Smart Charger be acceptable for the 12v version of the system until I convert it to 24v?

3. What do you suggest I use to monitor the SOC to know when it hits 50%? I know I could use the BMS with the app, but does anyone suggest a specific easily visible meter or something I can put on it? I know Victron has their smart shunt too.

4. I would like the charge and 50% cutt-off to be automated if possible so I don't have to mess with the system. Even if that means going with something more like an all-in-one system. Suggestions are welcome.

 

[John Frum]

So with that said, more questions.

1. Using a 1500 watt inverter, what size cables should I use for a 12V system. Then what should I switch them out for for a 24V system (if needed since I will most likely need the larger gauge for the 12V)?

1500 watts / .85 conversion efficiency / 12 volts low cutoff = ~147 dc amps
~147 dc amps / .8 fuse headroom = ~184 fuse amps.
2 awg wire rated for 105C will get the job done.
But who wants their wires getting hotter than boiling water.
2/0 awg will stay under 90C.

BTW that is out of spec high for your overkill bms.

2. Will my 15 Amp Victron Blue Smart Charger be acceptable for the 12v version of the system until I convert it to 24v?

How many amp hours is your pack?
Ideally you want to shoot for a charge rate of .2 to .5c.
Charging at 15amps isn't that terrible though.
The other factor is how configurable is the charger?

3. What do you suggest I use to monitor the SOC to know when it hits 50%? I know I could use the BMS with the app, but does anyone suggest a specific easily visible meter or something I can put on it? I know Victron has their smart shunt too.

You overkill bms does current accounting.
If you want a discrete meter get a shunt based battery monitor.
Victron is the Caddilac, Aili is the Chevy.

4. I would like the charge and 50% cutt-off to be automated if possible so I don't have to mess with the system. Even if that means going with something more like an all-in-one system. Suggestions are welcome.

You do this by setting the charge voltage based on observing the shunt and seeing what charge voltage correlates with 50% charge.
Hopefully your charger does sensible charge termination.

To figure out what 50% is you need to figure out what 0% is and what 100% is.
You do this by fully cycling the battery.
You need to top balance first before you can fully cycle your battery.

 

[GXMnow]

1) 1,500 watts on a 12 volt system is about 150 amps. How long will the wire run be? I would not go smaller than about 2/0 at that current. Windy Nation rates their 2/0 at 325 amps, but that is 105C temp rated, the NEC lists 75C 2/0 cable at 175 amps. But you also need to take the length in account. Losses at 12 volts add up fast. Lose 1.2 volt, and that is 10%.

2) I do not know that Victron unit. Are the voltage settings able to be dialed down for 12 volt? 15 amps will charge slow, as that is under 200 watts, but it will charge.

3) I am happy using the app in my JK BMS, the Overkill looks similar.

4) Setting the charge controller to 3.4 volts per cell on LFP will get you about 95% charged. The discharge side is a bit tougher. LFP cells near 50% do not change voltage much at all. Even after doing a full cycle to know your full capacity, you would need to watch the battery SOC to see when you get close to 50%. Most inverters etc. only go by voltage, and with LFP, you wont se a drop in voltage until down more like to 20%. Are you doing this for the storage of the cells? You could run a heater on a timer, once you know what your capacity is. Dial it in from the SOC on the BMS.

 

[Devin82m]

1500 watts / .85 conversion efficiency / 12 volts low cutoff = ~147 dc amps
~147 dc amps / .8 fuse headroom = ~184 fuse amps.
2 awg wire rated for 105C will get the job done.
But who wants their wires getting hotter than boiling water.
2/0 awg will stay under 90C.

BTW that is out of spec high for your overkill bms.

How many amp hours is your pack?
Ideally you want to shoot for a charge rate of .2 to .5c.
Charging at 15amps isn't that terrible though.
The other factor is how configurable is the charger?


You overkill bms does current accounting.
If you want a discrete meter get a shunt based battery monitor.
Victron is the Caddilac, Aili is the Chevy.



You do this by setting the charge voltage based on observing the shunt and seeing what charge voltage correlates with 50% charge.
Hopefully your charger does sensible charge termination.

To figure out what 50% is you need to figure out what 0% is and what 100% is.
You do this by fully cycling the battery.
You need to top balance first before you can fully cycle your battery.

Well, I won't be using the full 1500 watts to power what I need, so does the rule still apply?

My pack is 100 ah Fortune cells.

The charger was suggested by Battleborn (they sell on their site), it has an app via Bluetooth. It has a bunch of settings like: Storage, ABS, Bulk, Normal, and High. It does 4 amp or 15 amp.

 

[John Frum]

Well, I won't be using the full 1500 watts to power what I need, so does the rule still apply?

How much will you be using?

My pack is 100 ah Fortune cells.

The charger was suggested by Battleborn (they sell on their site), it has an app via Bluetooth. It has a bunch of settings like: Storage, ABS, Bulk, Normal, and High. It does 4 amp or 15 amp.

Should be fine.

 

[Devin82m]

How much will you be using?

Should be fine.

700 watts or less for now. The BMS 120 Amp continuous, with 200 amp surge I believe. The cells are 200 amp with a 600 amp pulse.

 

[John Frum]

700 watts or less for now. The BMS 120 Amp continuous, with 200 amp surge I believe. The cells are 200 amp with a 600 amp pulse.

That is ~70 amps dc.
Should be fine.

 

[Devin82m]

1) 1,500 watts on a 12 volt system is about 150 amps. How long will the wire run be? I would not go smaller than about 2/0 at that current. Windy Nation rates their 2/0 at 325 amps, but that is 105C temp rated, the NEC lists 75C 2/0 cable at 175 amps. But you also need to take the length in account. Losses at 12 volts add up fast. Lose 1.2 volt, and that is 10%.

2) I do not know that Victron unit. Are the voltage settings able to be dialed down for 12 volt? 15 amps will charge slow, as that is under 200 watts, but it will charge.

3) I am happy using the app in my JK BMS, the Overkill looks similar.

4) Setting the charge controller to 3.4 volts per cell on LFP will get you about 95% charged. The discharge side is a bit tougher. LFP cells near 50% do not change voltage much at all. Even after doing a full cycle to know your full capacity, you would need to watch the battery SOC to see when you get close to 50%. Most inverters etc. only go by voltage, and with LFP, you wont se a drop in voltage until down more like to 20%. Are you doing this for the storage of the cells? You could run a heater on a timer, once you know what your capacity is. Dial it in from the SOC on the BMS.

As for cable length, I don't know, 1ft to 2ft, just enough to mount it on a board directly above the pack. I assume once I convert to 24v the cable will be overkill for that system and totally reusable?

 

[Zwy]

As for cable length, I don't know, 1ft to 2ft, just enough to mount it on a board directly above the pack. I assume once I convert to 24v the cable will be overkill for that system and totally reusable?

The cable is usable, at 24v it can carry twice the watts of 12v. Amps stay the same.

 

[Devin82m]

Hey guys, since my BMS is on a 30 day back order, what should I do with my cells that are at such a high state of charge? They have already sat for a week.

 

[John Frum]

Hey guys, since my BMS is on a 30 day back order, what should I do with my cells that are at such a high state of charge? They have already sat for a week.

What SOC are they at?