Lead acid chargers with lipo

[Scottyf]

Hello All,
I've long been thinking about using a standard Pb charger with my Lipo. A kind of slow bulk charger if you will to top up my batteries while at work, or act as an emergency charger when further away from home.

Obviously carrying around my Lipo Balancer / Charger and Xbox Power supply are quite large and not portable and simple soloution would be better.

My question is the following...
If I used a pb charger such as http://www.zenid.com/charger.htm

Using say the nominal 60v (72v output @ about 2amps) I could use my 66.6v nominal pack to charge while i'm out.

This would give each cell 4v max if perfectly in balance (Which they won't be as such). But 4v gives a 0.2v headroom should they become out of balance.

I will still always balance charge at home.


Is this possible. Or are the charging charateristics not the same as CC/CV for pb batteries?

I wouldnt balance or constantly charge with this charger. But use it as a top up.
I also wouldn't need them charged in a hurry just a nice light portable charger.


Your answers are much appriciated.

 

[wesnewell]

Voltage is voltage. If it cuts off at 72v or even if it keeps voltage present at that rate or up to 75v, it's perfectly safe to use for an 18s lipo pack. I used my 60v sla charger on my 14s lipo pack for quite a while and just unplugged it when it got to 58.8v.

 

[Scottyf]

Thanks for the above. I keep the watt meter on it and lipo alarms to check pack voltages but it was really making sure there was no difference in the charging characteristics for using one of the chargers.

 

[dogman dan]

Keep an eye on it though. I tried using a ping 36v lifepo4 charger on 10s lipo.

It was supposed to stop in time, but between one check and another, I had two paralelled packs take one cell up to 4.4v.

Clearly more the packs fault than the charger, but one lower capacity cell in each pack allowed the voltage to climb into the toss it before it flames zone before the charger ever shut off.

Doing the math, I realized I was setting myself up to charge to 4.6v per cell if the charger shut off at 46v. I had dialed the voltage output down, but the shutoff point wasn't changed I guess. In any case, the charger was not slowing the charge at the top of the charge like an RC charger does. So it took very little time for it to go from needs a bit more time, to whoops, ruined some packs. I was keeping an eye on it, but not close enough clearly.

I see no problems though, if your calculations show you'd need 2 hours to fully charge, and you gave it 1 hour or whatever. Just enough charge to get you home, but not a full recharge. No danger of overcharge in that situation.

 

[Scottyf]

Hello,
Thanks for the above I guess I will just keep any eye on it to make sure it wouldn't go over.
It would obviously not balance but as a top up charger that's 500g it could work quite well.
Also means greater range at the higher voltage.

 

[jhusak]

I charge my 14S18P li-ion with MeanWell PB charger. It's 48V and has very good 3-phase charge cycle. There's a pot which let you set "end-of-charge-process" voltage cutout. I have set it to 58.4V. Every month (several charges) i check the balance and there is no "out of balance" since two years. However, I have manually balanced the cells by fully charging them one by one. A year passed. I have rechecked them, two of them needed little charging (3-4AH) - about 10% of nominal capacity (about 36-40AH).

I have assembled my cells by my own getting four or five year old cells from "not used" laptop batteries. It was a bargain, single cell costed about 30 US cents (the full package costed about 120 US Dollars). They do very well, but they were selected: charged, discharged and charged again; their voltage was written on them, after the day and week the voltage was checked and if it was the same - cell was good.

The two points. 18P single cell is a little to weak (well, laptop batteries). at 10Centigrades there is a little less power, at 0centigrades (frost) there is very less power, its hard to go by full speed.

The next point - the charger shuts off at 58.4, but does not turn on above 54V. I have to accelerate for a short while to lower the battery voltage to turn on the charger, when by cells are almost full.

 

[John in CR]

You should avoid using lead acid chargers with lipo. The voltage doesn't cut off like you'd think, and you'll end up with the dangerous combination of over-charged lipo. Sure you could get away with it as a portable opportunity charger with you acting as the cutoff. eg A typical 12V lead batt charger will typically bring the lead batt up to what 13.5V, but it doesn't actually cutoff at 13.5v . It reduces to a float charge current which the battery sheds as heat. Connect a lipo battery to that same charger and it will go up to 16v or 17v, because lipo likes to wait and shed its heat all at once.

For lithium you want CC/CV chargers, Constant Current which switches to Constant Voltage once the cutoff voltage is reached and the current tapers down.

Personally, I wouldn't use a lead charger even as an opportunity charger, because sure enough I'd lose track of time and come back to ruined batteries if not flaming ones.

John

 

[darth_elevator]

....14S18P li-ion with MeanWell PB charger....

I have assembled my cells by my own getting four or five year old cells from "not used" laptop batteries. It was a bargain, single cell costed about 30 US cents (the full package costed about 120 US Dollars). They do very well, but they were selected: charged, discharged and charged again; their voltage was written on them, after the day and week the voltage was checked and if it was the same - cell was good.

Hi! I realize this thread is old, but I'm wondering where did you get your "not used" laptop batteries? That sounds like a fantastic deal. I'd love to build my own pack.

 

[Allex]

Assume I have 14s li-ion battery, those are 58,8V fully charged
I have Lead acid charger laying around, the label states:
Output: 48VDC 2.5Amp
3-stage charging mode:
CC/CV, floating charging

.3-stages charging mode
1.Constant current
2.5A

2.Constant voltage
58.8Vdc;

3.Floating voltage
55.2Vdc;

I assume that it will fully charge my pack and then go into float mode. But what does this mean for my battery? Is it possible to disable float mode by modifying a lead acid charger?

 

[slowhands]

The output voltage will be a little low, which is safe. You won't fully charge them but you won't damage them either. If your need is for a small portable charger, this will be fine You might want to put a BMS on the battery if you want auto balance all the time.

Edit: I was thinking of dumb LA chargers, that typically charge in multiples of 14V in my experience. These are typically low current, slow, but light and portable for my backpack. This smart charger seems to overvolt the batteries, take care. My BMS would stop the charging in this event, but better not to have the problem to begin with.

 

[Allex]

But the charger have 58,8V on output right? so therefore they will be at 4,2V per cell.

 

[ecycler]

What it says it will do and what it actually will do may likely be very different things. Try doing a closely monitored charge and keep checking voltages, etc. That is the only way to really know how it will behave under load.

 

[Allex]

The charger went up to almost 60V and when it did a full charge of 48V lead acids it went over to Float voltage of 55,2
So it will overcharge the cells. But the remain questions is what happen with the cells when it goes to floating state