Hi. Great timing for me on this as well. I have been told by supposed experts that a Golf Cart needs a different (48V) charger, but based upon this conversation, I don't see why, especially if they have a BMS. Has anyone done this?? The max voltage on a LiPO 48V battery is 57V, the max for lead acid should be 14.8x4=58.6V. That looks really nice to me, what am I missing? Low-Voltag cut-off? I don't think so. I'm thinking of starting a business buying-up used golf carts, replacing the lead-acid with lithium battery packs from China, and re-selling them.
Which Charge profile is ok for LifePo4?
- Thread starter Wapst
- Start date
Are you referring to Lipo cells or LifePo4 cells?
Pappion
Retired Engineer Tech
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I have a WFCO converter for lead acid. No equalization. 14.4v bulk, 13.6 absorption, 13.2 float. Never saw it go to 14.4v, even with discharged batteries. On some pictures I see a row of 3 blue pots. I'm tempted to grab my meter and go play. Might make a LifePo4 charger out of it.
Lithium Iron Phosphate. Sorry. I didn't know there was a Lipo (brand?)
Lithium Iron Phosphate = Abbreviated as LiFePO4 or LFP (also sometimes abbreviated as LiFe, by chinese sellers)
LiPo = Lithium Polymer
Pappion
Retired Engineer Tech
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- Nov 26, 2020
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NO! LiFePO4 are safest. from wiki: " LiPo cells are affected by the same problems as other lithium-ion cells. This means that overcharge, over-discharge, over-temperature, short circuit, crush and nail penetration may all result in a catastrophic failure, including the pouch rupturing, the electrolyte leaking, and fire."
LiFePO4.. I think you have a subconscious attraction to LiPo ?
Actually it's 58.4 (3.65x16) volts using LifePo4 cells.
But as I was trying to explain you may never be able charge that high because there will always be one cell that is higher than the rest before the pack voltage is reached, and the BMS will cut off the charge to protect the cell that first reached 3.65 volts. It's the same when discharging but tends to be worse on the bottom if the cells have been parallel top balanced.From what I have read and my own experience, it's best to parallel top balance the cells. Then when they are put in series, to keep them between the knees. This will extend cycle life and keep the delta between the cells low. Of course a BMS is mandatory...IMO.
Hi. Until I got on here, LiPO always meant Lith Iron Phosphate, so - yeah - it is a habit.Actually it's 58.4 (3.65x16) volts using LifePo4 cells.
From what I have read and my own experience, it's best to parallel top balance the cells. Then when they are put in series, to keep them between the knees. This will extend cycle life and keep the delta between the cells low. Of course a BMS is mandatory...IMO.
All the rest I understand and agree with 100%. It is too bad a BMS doesn't/can't top-balance until in the absorption phase, and at that, only like 50mA? So I get it regarding parallel top-balancing, and - call me a nerd it you want, but even if I wasn't in Canada where it is currently -20C, I would want a BMS. They are cheap insurance.
I know what you mean regarding passive balancing. I am not so sure active balancing is worth it either even though it's more effective in the absorption stage.
An active balancer takes current from the high voltage cells and transfers it to the lower voltage cells and we are talking amps...not milliamps. The problem is with LiFePo4 cells the voltage rises so quickly there isn't enough time for either method to work very well. The only way around this that I can see is to lower the charge current low enough so the balancing can keep up and do some good.
My overkill BMS can balance at any voltage as all of those parameters can be set. I can set it to balance when not charging and start balancing at any voltage I want it to. I can also set the Delta, right now it's set to .015. And it's set to balance while charging and to start balancing at 3.4 volts. But I have noticed if I set the charger to anything less than around 200 milliamps the balancing doesn't work...lol. Other than that I am very happy with it.
So I have decided to stay within the knees. If my voltages start to drift to the point I become concerned, then I will probably need to get an active balancer and that can be used with my BMS. IF I have to get an active balancer I will make sure I can set all the parameters like I can with the BMS I have.
Hi. Nice to hear, I don't know anything about the Overkill. I guess I'll look it up. Also, I was not aware of an active balancing BMS which can push 1,000s of mA! That sounds pretty-good to me, I'd like to know more. All slightly nerdy, but I'm very interested.
Jim
I suggest you do a forum search for Heltec to get started. Heltec makes full fledged BMS's with active balancing. But they make stand alone active balancers as well.
The Overkill Solar BMS is fairly popular and the seller is a member of this forum. I highly recommended it if it is suitable for ones use. The warranty can not be beat.
Overkill Solar – More is Better…
It can be purchased through Will's website and then Will gets a commission. If purchasing from Will's website the link will redirect to Overkillsolar's website so there is no confusion ordering.
I wish everyone would at least read these engineering white papers about LiFePo4 battery before they just posted any crap.
nordkyndesign.com
Lithium battery systems | Nordkyn Design
nordkyndesign.com
I wish everyone would at least read these engineering white papers about LiFePo4 battery before they just posted any crap.
Lithium battery systems | Nordkyn Design
I wish everyone would at least read these engineering white papers about LiFePo4 battery before they just posted any crap.
Lithium battery systems | Nordkyn Design
Hi. I'm starting a company up here in Canada (or at least trying to). The idea was to build second-life battery solutions, so BMSs are very important. Among other things, I'm gathering candidates for BMSs, and then will take a bunch of mis-matched cells which are near their end of life (say, 40-60%?) and run them. I have a research grant for this.
Thank you both for helping me, I am still learning about this. Yes they will be top balanced I've just started that process the other day. I am assuming that top balancing and having the smart BMS is going to keep them balanced but I will of course check them often. So I should have no runaway problems? right?
I myself am in Vancouver Canada and have spent 2400$ on 16x 280AH Xuba eve cells and I don't want to take any risk either, that is why I am here asking for anyones help/experience.
If I understand this correctly what you are saying is that picking the AGM setting might overcharge my batteries? I thought the lower voltage was going to protect them from being overcharged? I guess what I am trying to ask is why/how is it a bad thing when the lower voltages are a good thing?
So this is not how I thought it would work. I thought that my charger being a dumb device would just charge away and when the BMS decided the batteries were full it would cut them out... now you're telling me I'm wrong about that and that the charger should know when they're full and stop charging? I'm reading my charger/inverter manual and it looks like it never wants to stop charging and I thought it was the BMS that was going to stop the batteries from receiving more charge then they should? I am so confused right now.
According to my math, If it takes 1 hour to charge the batteries then T0=1 and T1=10, and if it takes 5 hours to charge my batteries then T0=5 and T1=50. The absorb voltage isn't stated anywhere but it looks like I will almost always get a 10-12hr absorb time. And in 10 days the charger tries to kill my batteries all over again? I am thinking that the BMS needs to cut the batteries out at full charge and keep them under lock and key?
One of the reasons I was thinking it was no big deal to use the AGM1 setting is that the LiFePo setting is also labeled AGM2.
I have the Sigineer Power 3KW charger/inverter.
I myself am in Vancouver Canada and have spent 2400$ on 16x 280AH Xuba eve cells and I don't want to take any risk either, that is why I am here asking for anyones help/experience.
I have tried it and yes it works. But as I paid almost $1200 for my batteries I would rather not have taken the risk is all. It is simply not worth destroying my batteries.
But hey, if you have money to throw away then go for it.
The ONLY other suggestion I would have is that if you have OCD as I do then you won't mind checking them every 5 minutes to make sure they do not do a runaway on you is all.
But there is a reason for the settings. Otherwise they would never had made them.
Just my thoughts on this.
If I understand this correctly what you are saying is that picking the AGM setting might overcharge my batteries? I thought the lower voltage was going to protect them from being overcharged? I guess what I am trying to ask is why/how is it a bad thing when the lower voltages are a good thing?
So this is not how I thought it would work. I thought that my charger being a dumb device would just charge away and when the BMS decided the batteries were full it would cut them out... now you're telling me I'm wrong about that and that the charger should know when they're full and stop charging? I'm reading my charger/inverter manual and it looks like it never wants to stop charging and I thought it was the BMS that was going to stop the batteries from receiving more charge then they should? I am so confused right now.
According to my math, If it takes 1 hour to charge the batteries then T0=1 and T1=10, and if it takes 5 hours to charge my batteries then T0=5 and T1=50. The absorb voltage isn't stated anywhere but it looks like I will almost always get a 10-12hr absorb time. And in 10 days the charger tries to kill my batteries all over again? I am thinking that the BMS needs to cut the batteries out at full charge and keep them under lock and key?
One of the reasons I was thinking it was no big deal to use the AGM1 setting is that the LiFePo setting is also labeled AGM2.
I have the Sigineer Power 3KW charger/inverter.
Which one of us is posting crap?I wish everyone would at least read these engineering white papers about LiFePo4 battery before they just posted any crap.
Lithium battery systems | Nordkyn Design
This is what I want to do! Thanks for putting it into good words for me.
Hi. Just ignore the way that information was delivered. What you have done and written is admirable, and I'll bet you would really like to hook it all up! As a relative novice, you are right where you need to be, and without a Pro Installer, you cannot be too careful, and (like many of us DIYers), you prefer to do it yourself, so you can understand what is going on and relax, knowing if something weird happens you are not helpless. We all have our own path. If you would like to have a chat on the phone, I can help you think this through.
