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This newbie just got his EVE 280 amp hr cells.

Clavebob

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I'm a newbie in this forum but I have messed about with electrifying sailboats in the past. It was awhile ago so my options then were lead acid. I have joined the four cells that I just received together and they're charging up. It's interesting to observe how lifepo4 batts charge compared to lead acid. The voltage is slowly rising but so is the amperage. It that normal for these types of batteries? I'm going to bulk charge them up to 14 volts or so and then use the Dr Meter power supply to top balance. So far the batteries are sucking up 8 amps. Seems to be holding there. The pack reads13.4 volts.
 
I'm a newbie in this forum but I have messed about with electrifying sailboats in the past. It was awhile ago so my options then were lead acid. I have joined the four cells that I just received together and they're charging up. It's interesting to observe how lifepo4 batts charge compared to lead acid. The voltage is slowly rising but so is the amperage. It that normal for these types of batteries? I'm going to bulk charge them up to 14 volts or so and then use the Dr Meter power supply to top balance. So far the batteries are sucking up 8 amps. Seems to be holding there. The pack reads13.4 volts.

is your BMS installed? If not, stop immediately.
 
I get what you mean but I'm being careful. I don't have a BMS yet. I'm bringing the pack up to apx 14 Volt. Then I will rewire the pack in parallel and use my DC power supply to top balance. Thanks for the warning.

I figured out pretty quick that something was not right with the battery charger. It turns out the battery clamps that I had attached a long time ago were just twisted together. I've attached ring terminals now so I can directly attach to the batts. Now I'm charging at the max for the unit, 35 amps. Before with the twisted wires all I was putting into the battery was 8 amps. That could have caused a fire !
 
I get what you mean but I'm being careful. I don't have a BMS yet. I'm bringing the pack up to apx 14 Volt.
You NEED to be monitoring the cell voltages if you are playing the role of the BMS.

If you are only watching battery voltage and it gets to 14V, the cell voltages could be 3V, 3V, 3V, 5V and your game is over, you destroyed a cell.

You NEED to monitor them regularly. They may move slow until one cell gets over 3.4V then this cell will likely accelerate its voltage rise. At 3.5V you're minutes away. At 3.6V you're seconds away (maybe 60, maybe 600).
 
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I'll stay tuned to hear what happens --- Hopefully not what has happened to so many others -- one cell going way over 3.65v and you're looking for a single cell --- Good Luck
 
While you're babysitting your battery in your role as a BMS, there are things to do, hopefully not distract you from cell voltage monitoring.

Label your cells. I like letters A, B, C, D because the cell positions are numbers (cell 1 is the negative end of battery).

Keep checking cell voltages.

Put clear markings which end of a cell is positive and which is negative. I have big pieces of red tape with a + sign on the positive side. Duct tape with a - on the negative. Its surprising how often this reduces mistakes.

Keep checking cell voltages.

Take notes of your cells. Volts when you received them. Notes on how the voltages are increasing in relation to each other. The fast risers and fallers are the low capacity cells.

Keep checking cell voltages.
 
I get what you mean but I'm being careful. I don't have a BMS yet. I'm bringing the pack up to apx 14 Volt. Then I will rewire the pack in parallel and use my DC power supply to top balance. Thanks for the warning.

I figured out pretty quick that something was not right with the battery charger. It turns out the battery clamps that I had attached a long time ago were just twisted together. I've attached ring terminals now so I can directly attach to the batts. Now I'm charging at the max for the unit, 35 amps. Before with the twisted wires all I was putting into the battery was 8 amps. That could have caused a fire !

Human BMS have 100% failure rate.

You will miss 14V and over volt the cells. Guaranteed.

Stop immediately. This is how people ruin their cells.

Follow the guide. It exists for a reason.
 
Can you monitor all individual cells at least every 30sec till the cells are full?

Assuming you have 4 cells and arriving at 50% soc, charging with 8A is going to take 17-18 hours. But they might be at lower SOC, or higher.

So can you monitor the cells for the next 15-20 hours, without sleep and taking a piss? Fine.

In reality: Don't be tempted to try, just get the BMS connected FIRST.
 
I get what you mean but I'm being careful. I don't have a BMS yet. I'm bringing the pack up to apx 14 Volt. Then I will rewire the pack in parallel and use my DC power supply to top balance. Thanks for the warning.

I figured out pretty quick that something was not right with the battery charger. It turns out the battery clamps that I had attached a long time ago were just twisted together. I've attached ring terminals now so I can directly attach to the batts. Now I'm charging at the max for the unit, 35 amps. Before with the twisted wires all I was putting into the battery was 8 amps. That could have caused a fire !


Sounds good I have bookmarked this and will be monitoring this thread from time to time to see when the inevitable fireworks happen.
 
I agree that you need a BMS to bulk charge them in series. The charge curve is exponential and it takes very little time to spike.

Get a BMS or place them in parallel and just wait the few days for it to top balance with the power supply set to 3.65V.
 
Overkill has JBD in stock...get one in a couple of days. Comes with a nice BT dongle/app, and a very good how-to-do-it on building a battery as well.
Or just parallel them and charge at 3.65V. Might take a couple of days, but you won't over-volt any of the cells that way.
 
Ok then. I will stop trying to be a BMS and wait for the Overkill BMS to arrive a few days from now. BTW, I was monitoring individual cell voltages as I charged the 12 volt pack. All the cells are staying at the same voltage, 3.3 . I certainly have no desire to destroy the cells. I just had to play with them though. Thanks for all the feedback. Cheers !
 
Ok then. I will stop trying to be a BMS and wait for the Overkill BMS to arrive a few days from now.

Might as well upgrade the charge leads per the guide and get a few days of parallel charging with the power supply set to 3.65V BEFORE it's connected to the pack (per the guide).

With good leads, that's ~720Ah into them in the next 3 days.

BTW, I was monitoring individual cell voltages as I charged the 12 volt pack. All the cells are staying at the same voltage, 3.3 .

And they will stay almost perfectly within 0.05V even if horribly imbalanced until the moment that one rockets above limit leaving the others below 3.4V. This might not happen to you, but it happens more often than it doesn't.

The voltage curve of LFP is so flat in the operating range (3.1-3.4-ish), cells at wildly different states of charge may read almost exactly the same voltage.

I received 9 EVE cells that varied by 12Ah in their states of charge (4.2% variation). This is a massive difference when talking cell voltage differences at peak charge. I've personally seen a cell SoC difference of 0.1% cause a cell runner.

I certainly have no desire to destroy the cells. I just had to play with them though. Thanks for all the feedback. Cheers !

Thank you. Those of us that have been hear awhile have seen too many posts with a tale of exceeded voltage and often bloated cells accompanied by, "are my cells ruined?" The answer is almost always "yes."
 
The overkill manual also has some good explanation and examples supporting top-balancing. The how and why, and what can happen if you don't.

I still had to do quite a bit of bleeding down of high cells at high-knee - near full charge. I used a 12V headlamp bulb during the last few amps of charging to even all the cells up - right at about 3.55 or so. Even still, If I try to charge past about 14.2V or that magic 3.55Vpc or so, one will or more will tend to reach full charge and its voltage will shoot up - bms will shut down charging. Which is not a great way to manage your battery charging. So you set your peak voltage and duration on your charge source so it gets your pack to full charge without cells going over the volt max you've set in your BMS. The closer matched the cells are the more even they'll be near full charge - same can be done for near full discharge, but most don't need to bother with that.

Overkill by default sets nearly everything up for you and tests it. Another value-added perk for sourcing from them, plus you can call Steve for technical support if you have trouble. Try doing that with alibaba. ;)
 
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You know we're terrible -- you know the few that would check this thread to see how bad he damaged a cell or two --- Good job backing off and waiting on a BMS -- I always just Parallel them up and wait
 
The overkill manual also has some good explanation and examples supporting top-balancing. The how and why, and what can happen if you don't.

I still had to do quite a bit of bleeding down of high cells at high-knee - near full charge. I used a 12V headlamp bulb during the last few amps of charging to even all the cells up - right at about 3.55 or so. Even still, If I try to charge past about 14.2V or that magic 3.55Vpc or so, one will or more will tend to reach full charge and its voltage will shoot up - bms will shut down charging. Which is not a great way to manage your battery charging. So you set your peak voltage and duration on your charge source so it gets your pack to full charge without cells going over the volt max you've set in your BMS. The closer matched the cells are the more even they'll be near full charge - same can be done for near full discharge, but most don't need to bother with that.

Overkill by default sets nearly everything up for you and tests it. Another value-added perk for sourcing from them, plus you can call Steve for technical support if you have trouble. Trying doing that with alibaba. ;)
I've never purchased anything from Alibaba. I did buy my cells from Docan, an Asian company but they have warehouses in Texas. So. it took less than a week to get them. Overkill seems like a great outfit to do business with. I have exchanged email with Troy. Have not met Steve yet. I need to do some reading instead of just watching YouTube videos about it all. I have learned a lot from the videos though. Will Prouse if very good. He led me to this forum and to Docan for the cheapest batteries that aren't being shipped from China.
 
You know we're terrible -- you know the few that would check this thread to see how bad he damaged a cell or two --- Good job backing off and waiting on a BMS -- I always just Parallel them up and wait
Well, the people here or some of them have been witness it seems to many battery disasters. As folksy dude put it, 'Smart people learn by observation and from other's mistakes but some of us just have to pee on the electric fence themselves.'
 
The overkill manual also has some good explanation and examples supporting top-balancing. The how and why, and what can happen if you don't.

I still had to do quite a bit of bleeding down of high cells at high-knee - near full charge. I used a 12V headlamp bulb during the last few amps of charging to even all the cells up - right at about 3.55 or so. Even still, If I try to charge past about 14.2V or that magic 3.55Vpc or so, one will or more will tend to reach full charge and its voltage will shoot up - bms will shut down charging. Which is not a great way to manage your battery charging. So you set your peak voltage and duration on your charge source so it gets your pack to full charge without cells going over the volt max you've set in your BMS. The closer matched the cells are the more even they'll be near full charge - same can be done for near full discharge, but most don't need to bother with that.

Overkill by default sets nearly everything up for you and tests it. Another value-added perk for sourcing from them, plus you can call Steve for technical support if you have trouble. Trying doing that with alibaba. ;)
I've downloaded the manual. Now all I've got to do is make myself read it.
 
I've never purchased anything from Alibaba. I did buy my cells from Docan, an Asian company but they have warehouses in Texas. So. it took less than a week to get them. Overkill seems like a great outfit to do business with. I have exchanged email with Troy. Have not met Steve yet. I need to do some reading instead of just watching YouTube videos about it all. I have learned a lot from the videos though. Will Prouse if very good. He led me to this forum and to Docan for the cheapest batteries that aren't being shipped from China.

Both are good choices and seem to deliver consistently.
 
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