desmond007 said:
I think Li-ion 18650 cells usually get empty at around 2.75. So 2.75*13=35.75. My charger is 48V. So what you think how much it can put in? 50%? What is the equation to calculate?
You'd have to look at the spec sheet for your specific cells from the manufacturer, to get their charge/discharge curves.
I have only written on my charger that it's 48v 4A. Nothing else I know about it.
Well, that's probably not the actual output voltage if your SLA pack was four SLA bricks in series. It's probably more like about 58V That's usually what a 14s Li pack would charge up to (about 57-59v depending on chemistry and cell specs).
But it isn't designed to output the right curve of voltage/current for charging Li packs, so it may not do the charging you want it to do, depending on the Li cell chemistry and specs--you'll have to look at those from the cell manufacturer to see if they'll match up. Most likely, it won't matter--it'll probably work anyway, as long as the voltages are right and the current is not too high.
The problem you might have is that if you have a 13s pack, and the charger keeps outputting anywhere near full current up to the top of it's voltage, it'll be a lot more current than the BMS can shunt around the cells, so they'll all get overcharged each time. If the BMS correctly shuts charge off when any cell gets above a certain voltage (4.25v, etc) , then drains down the high ones, that shouldn't be a problem, and would just ensure they always get balanced.
IF the BMS does not shutoff when a cell goes too high, it could potentially overcharge the cells to 4.5v+, which is not healthy for them, and if they are not good cells (or a cell has a problem) could even start a fire.
My main concern is if I charge my Li-ion pack with this charger (which is designed for only VRLA batteries and maybe not CC/CV), will it eventually damage my cells?
If it's voltage (or current) output is higher than what your cells can take, and your BMS (if you have one) doesn't prevent overcharge, then yes.
If it's voltage is less than your cells can take, then it probably wont' hurt anything--but if it doesn't get to the point the BMS can balance the cells at, then if the pack is prone to getting unbalanced, the BMS can't fix that.
My bms config is something like this
View attachment 1
Will it support undercharging rather than 4.2v per cell?
You can always charge less but most BMS won't balance the cells unless you charge to the balance point.
About discharge one thing I want to know, if I discharge via BMS (rather than direct) how the cut-off works? when a cell group reaches 2.7v does it particularly cuts off that cell group and continues to take charges from other groups or it cut off the whole power?
No, it has to cut the whole pack--there's no way for the BMS to shuffle power around like that.
So to increase the battery life if I charge it by a 54.6v charger and stop it when it charges to 80%, will it work? or I have to specifically charge it by 13x4.05v=52.6v charger?
Depends on the charger--the Cycle Satiator from Grin Tech http://ebikes.ca can be programmed for whatever you want it to do. But it's not cheap.
And again, if you don't charge to the balancing point of the BMS it can't balance the cells. If they don't get out of balance it doesn't matter, but if they do, it does matter, because they get further and further out of balance every cycle, and you get less and less total capacity from the pack, and the low cells are pushed harder and harder each cycle.
You don't have to balance charge every cycle, just whenever they are getting out of balance.
P.S: Amberwolf, I just read about your dogs and can't imagine it can happen with someone. God must be evil. I had one many years ago, when he was gone I can't get another. Hope you are well and I'm sure they are well also. Good wishes to you brother. Live strong!
Thanks--it was the hardest time I've been thru so far. I have new dogs now, Yogi and Kirin (there are always more dogs that need help and a home); I do permanent fostering for the local Saint Bernard rescue group (http://www.saintrescue.org/arizona.html) and the dogs help me as much as I help them. I couldn't live without them (wouldn't have a reason to, either).
:lol: 
