Is this safe to do with Lifepo batteries?????

[Deleted member 9967]

I will [hopefully] be getting my 280Ah lifepo batteries this week.
However the special charger and BMS won't come for a while yet.

Is it safe to use my 8Amp 24 volt Gel lead acid charger on my Lifepo batteries until the proper charger and BMS comes?

Yes I know it will be 35 hours if I have to charge it from a full discharge.
However I will not be charging them fully, nor discharging them fully either.

Just that I need to use my mobility scooter and the lead acid batteries in them now are not going very far as it gets colder.
So it would be great if I can use the Lifepo ones for now.

Thanks

 

[j_t_l]

I'd go with "no, not safe".

It depends on what you mean by safe... Everything will be fine as long as no cell goes over the voltage limit. Cells get damaged over 4.2v, and degrade a lot faster over about 3.6v. Over about 3.5v the voltage spikes up VERY quickly even with only 8 amps of charging -- so it's easy damage something if you're not very attentive.

At that low of a rate (8 amps, 0.03c) you'll be fully charged at 3.4v per cell. You could do something like this:

• Make sure your cells are properly top balanced
• Connect the lead-acid charger
• Set a 30-minute repeating timer
  • Check all cell voltages manually by hand -- if any cell is at/over 3.35v-3.4v, stop.
  • If you think you'll miss the 30-minute timer for ANY reason, stop charging and continue some other time

Given all that: I'd say "not safe" because it's a pain in the butt and mistakes can damage cells. Humans are not very good at these tasks. A BMS is great at it ;-).


You didn't mention discharging the battery in your scooter -- but this is also not safe. The cells will be severely damaged if the voltage drops below 2.0v, and really should never go below 2.5v. There's nothing in the scooter which will protect the cells. You'll have to be very careful to avoid draining the batteries, and you'll have to manually check each cell yourself periodically.


It might be fun to do once while you wait for the BMS to arrive. But be careful.

 

[zorlig]

It's fun, but safe? No, you'd have to watch it like a hawk. You are the bms!!

 

[Deleted member 9967]

Thanks. With these new batteries I will be able to go well over 50 miles distance. However, at 5 mph, that is 10 hours of driving. Something of which I have no intention of doing.
So no worries about them going to low to soon.
As for charging them too high.
I was shown a video of the batteries being sent to me that said they were all 3.32.
So no worries there either of over charging them any time soon according to charts on this site.
It will take so many hours that I am not too worried.

But yes, I will be careful and test the voltage often.
Thank you.

 

[Deleted member 9967]

It's fun, but safe? No, you'd have to watch it like a hawk. You are the bms!!

Then that is not a problem. Thanks.

 

[Deleted member 9967]

I suppose I should add that Will said it was ok because the top voltage for lead acid is safe for Lifepo batteries.
I was just wondering what other concerns there might be is all.

 

[j_t_l]

I was just wondering what other concerns there might be is all.

As Zorlig said, you are the bms
It should be fine as long as you make sure:

• Each cell stays within the proper voltage range
  • Conservatively 3.0v-3.4v per cell
• Don't charge/discharge outside of temperature limits
  • You mentioned cold weather -- especially don't charge if the batteries are below freezing! This isn't as much of an issue at a 0.03c charge rate.
• Stay within current limits
  • doesn't sound like a problem here
• Use proper fuses / protection
  • I assume the scooter probably has fuses, and I hope the battery charger has it's own protection too

I suppose I should add that Will said it was ok because the top voltage for lead acid is safe for Lifepo batteries.

This assumes that the cells are top balanced.

A 12v charger typically charges at something like 14.4v.
If not top balanced 14.4v could be one cell at 4.2v, and 3 cells at 3.4v -- and then you've damaged one cell. A good top balance would probably prevent something this bad. When balanced you could get something like 3.7v for the highest cell (still not great) and 3.57v for the other 3.

At 24v, it's easier to fry individual cells. Keeping the same "3.57v" for 7 cells and 28.8v charging voltage, now the 8th cell would be 3.81v which is definitely not good (but I wouldn't be worried if it happens once or twice -- lifepo4 is fairly forgiving up to 4.2v).
And if it's not top balanced, you could easily get something like 7 cells at 3.4v and 1 cell at 5v -- and that cell will be destroyed (and hopefully doesn't start a fire).

 

[Gazoo]

I suppose I should add that Will said it was ok because the top voltage for lead acid is safe for Lifepo batteries.
I was just wondering what other concerns there might be is all.

If you had the BMS then it would be safe. I know that's not the answer you are looking for but it is the correct answer.

The cells first need to be parallel top balanced. Even after top balancing the cells will still not be perfectly matched at the top.

What Will says is true but only if using a BMS. If you could watch all the cells voltages at the same time 24/7 and shut the charger off when you notice a runner then it would be safe. I don't think I would be able to do it....lol

For our DIY applications, when charging or discharging one needs to think of each cell in the pack, not of the battery as a whole.

You have previously said you don't have money to burn, I don't either. So do things properly and keep your cells safe..

 

[Luthj]

You have little or no warning when the highest cell spikes. Even at low charge rates it may only take 15 minutes. If you are unfailingly vigilant it's okay. If you aren't, one or more cells could be destroyed.

 

[JoeHam]

The cells first need to be parallel top balanced.

Well that’s not true.

My 16 cells have never been top or bottom balanced and they live a happy life in harmony and balance with each other.

They are used every day, BMS balanced during the charge cycle only. Solar charging only as well.

People have ruined brand new cells trying to top balance with much safer setups than the OP is considering.

I would wait for the BMS to arrive and then put the cells to work and make them earn their keep ?

 

[Gazoo]

Well that’s not true.

My 16 cells have never been top or bottom balanced and they live a happy life in harmony and balance with each other.

They are used every day, BMS balanced during the charge cycle only. Solar charging only as well.

People have ruined brand new cells trying to top balance with much safer setups than the OP is considering.

I would wait for the BMS to arrive and then put the cells to work and make them earn their keep ?

And you are using 60 or 100ah Fortune batteries if I recall correctly? Were they capacity matched when you purchased them? Regardless we are talking about the EVE 280ah cells. These will take forever to balance using using a typical BMS and one won't be able to get full capacity until that happens. Granted these cells are closely IR and voltage matched but not capacity matched.

I have noticed you have posted several times your reasons for not parallel balancing and your reasons for avoiding it. And I actually agreed with you until I read the threads and understood the importance of doing it and how to do it safely to avoid ruining them. I will feel much better top balancing mine and then testing the capacity.

Having said that I have concerns about the OP as well based on OP's post. And in the OP's case it might be best to forgo balancing. But it could come at a substantial loss of battery capacity initially.

 

[cinergi]

I think it's unwise to say "cells never need top balanced" or "cells must always be top balanced" .. but rather, understand that safe top balancing will increase your chances of having a longer-living problem-free battery. Have people created batteries that work fine w/out top balancing? Sure. But there are too many factors at play to make such broad statements.

 

[Deleted member 9967]

As Zorlig said, you are the bms
It should be fine as long as you make sure:

• Each cell stays within the proper voltage range
  • Conservatively 3.0v-3.4v per cell
• Don't charge/discharge outside of temperature limits
  • You mentioned cold weather -- especially don't charge if the batteries are below freezing! This isn't as much of an issue at a 0.03c charge rate.
• Stay within current limits
  • doesn't sound like a problem here
• Use proper fuses / protection
  • I assume the scooter probably has fuses, and I hope the battery charger has it's own protection too

This assumes that the cells are top balanced.

A 12v charger typically charges at something like 14.4v.
If not top balanced 14.4v could be one cell at 4.2v, and 3 cells at 3.4v -- and then you've damaged one cell. A good top balance would probably prevent something this bad. When balanced you could get something like 3.7v for the highest cell (still not great) and 3.57v for the other 3.

At 24v, it's easier to fry individual cells. Keeping the same "3.57v" for 7 cells and 28.8v charging voltage, now the 8th cell would be 3.81v which is definitely not good (but I wouldn't be worried if it happens once or twice -- lifepo4 is fairly forgiving up to 4.2v).
And if it's not top balanced, you could easily get something like 7 cells at 3.4v and 1 cell at 5v -- and that cell will be destroyed (and hopefully doesn't start a fire).

Well the cells are being delivered at 3.32 as I said.
And the temps are outside temps.
The scooter stays inside with me. So room temp.
Lots of fuses on the scooter.
Top balancing comes once the BMS etc gets here.

 

[Deleted member 9967]

And you are using 60 or 100ah Fortune batteries if I recall correctly? Were they capacity matched when you purchased them? Regardless we are talking about the EVE 280ah cells. These will take forever to balance using using a typical BMS and one won't be able to get full capacity until that happens. Granted these cells are closely IR and voltage matched but not capacity matched.

I have noticed you have posted several times your reasons for not parallel balancing and your reasons for avoiding it. And I actually agreed with you until I read the threads and understood the importance of doing it and how to do it safely to avoid ruining them. I will feel much better top balancing mine and then testing the capacity.

Having said that I have concerns about the OP as well based on OP's post. And in the OP's case it might be best to forgo balancing. But it could come at a substantial loss of battery capacity initially.

No, I am using 280 Ah batteries from Xuba who uses Eve batteries.
I NEVER said I own or wnat or in any way have 60 or 100 Ah fortune batteries.
Also I watched the video of my batteries being tested as I said up above, at 3.32 volts each.

Not sure how you get that I posted several times about parallel balancing, as I know so little about it.

I have no clue who you are talking about, but it is not me. That is very clear.

You have a LOT of things wrong about me.
I am not sure why though.

 

[Deleted member 9967]

Hey guys. It is only for a couple of weeks. And once charged, I doubt it will need more than 3 or 4 more charges in those two weeks.
But I understand your concerns and thank you for things to watch out for.
Which is what I was after.

Thanks

 

[Gazoo]

No, I am using 280 Ah batteries from Xuba who uses Eve batteries.
I NEVER said I own or wnat or in any way have 60 or 100 Ah fortune batteries.
Also I watched the video of my batteries being tested as I said up above, at 3.32 volts each.

Not sure how you get that I posted several times about parallel balancing, as I know so little about it.

I have no clue who you are talking about, but it is not me. That is very clear.

You have a LOT of things wrong about me.
I am not sure why though.

I was replying to JoeHam. The only part that was directed at you was the last paragraph...solely out of concern. Good luck. I will need some too.

 

[Deleted member 9967]

If you look at my reply you will see it was not directed towards you. The only part that was directed at you was the last sentence...solely out of concern. Good luck. I will need some too.

AHA. Ok got it now.
Thanks.

 

[Metalophile]

It depends on the lead acid charger, but I think a lot of the lead acid chargers will use a voltage much higher than recommended. If you could find yourself a constant voltage power supply which can be adjusted to about 3.4 volts for cell, or about13.6 V for a 4S battery, I think that would be good for charging to a good level with very low risk of overcharging any cells. I echo others in that if you do go ahead, check the voltage of each cell as if you had OCD. If the cells are out of balance voltage wise when you receive them at all, I would parallel balance them first. Or you could parallel charge them all to 3.6 volts at the same time if you have a good bench power supply.

 

[Deleted member 9967]

It depends on the lead acid charger, but I think a lot of the lead acid chargers will use a voltage much higher than recommended. If you could find yourself a constant voltage power supply which can be adjusted to about 3.4 volts for cell, or about13.6 V for a 4S battery, I think that would be good for charging to a good level with very low risk of overcharging any cells. I echo others in that if you do go ahead, check the voltage of each cell as if you had OCD. If the cells are out of balance voltage wise when you receive them at all, I would parallel balance them first. Or you could parallel charge them all to 3.6 volts at the same time if you have a good bench power supply.

Actually, I do have OCD.
I consider it a help and not a disability though LOL.
Especially when I want to study something. ?
Well they are all at 3.32 as I have said a few times above.
So they are balanced to a degree already.
As for the high level of charge.
It is no higher than regular Lifepo chargers.
But yes, as I have said before. I will be checking the voltages often.
And at only 8 Amps for the charger, it will take a day or two to fully charge the large batteries anyhow.
EDIT: And being so large, I do not have to fully charge them to use them for what I want anyhow.
So checking every few hours and then stopping before full charge works as well.

 

[Gazoo]

Well they are all at 3.32 as I have said a few times above.

The voltage is not a good indicator of the SOC of each cell. If it was no one would need to parallel balance when the batteries are first received. I do hope you don't ruin any cells.