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...been thinking a lot about what I WISH was available as far as a charger goes, and not being an EE, I want to just put the functional requirements out, and ask if anyone can put it together, or maybe already has?
first some assumptions/goals:
- as a mechanical DIY guy, I am not interested in huge amounts of flexibility, data recording, etc. I want to 'set it, and forget it'.
- primary goal is a safe, reliable on-board charger designed for LIFePO4 prismatic cells (TS, CALB, and the like).
- huge amount of flexibility is not required because once installed, I hope it lasts at least 10 years along with the batteries.
- minimum cost while meeting functional requirements is primary, but also important to minimize size, weight, and be sealed against dust, water durable with regard to cycle life, vibration, temperature, etc.
major functional specs:
- plug into 110v, or 220v, and self limit to no more than 15 amps so as not to blow the typical house breaker. I think the major slice of the DYI market is fine with a 6 to 10 hour charge time, and not about to install a dedicated high-amp line to the garage.
- have a built in interlock terminals that would pass thru the usual 13v key-on juice to the main contactor solenoid when not charging, and open the circuit when plugged in to prevent key-on closing the typical circuit. Eliminating the need for one external component.
- have multiple (perhaps 50) terminals to accept 24ga wire monitoring individual cells. one wire per cell, plus one. 50 would allow enough for typical packs up to 48 cells.
(this is the tricky part)
- have internal brains to scan thru all cell monitor voltages, and switch from CA mode to CV mode at a cell level as soon as any cell hits target voltage. When in CV cell mode, output amps would be ramped down as needed to hold cell(s) at or below target voltage. No real attempt made to shunt or balance, just monitor and ramp the charge down per the highest cell.
possible? is this kind of 'scanning' the problem, or is that not really very expensive to build?
The least expensive internal design would probably be to not even attempt to ramp down, but use a fixed target finish of something like 3.70v and just stop the charge as soon as the first cell hits the limit. One extra that would be nice if it could be done without too much cost would be user-settable finish voltage... perhaps pre-set to 3.70, but able to move up or down a little in .05v increments. Extras would be some external display of which cell hit the limit first with something as simple as an external LED. Slightly more complex might be internal settings to show 'yellow' when cell is within .05v of target, and then 'green' when at target. It would be a quick visual of balance to see if the first high cell is more than .05 higher than MANY cells, then it may need to be balanced down a little.
....so my question is whether there is already a simple foolproof relatively inexpensive charger like this I don't know about, or if ya'll think something like this would even appeal to the typical DYI as a minimum charger/monitor system at moderate cost.
I know I for one don't feel I need or want a super adjustable super smart charger with completely settable voltage rnges and data bus, nor do I want to spend $1000-$2000 for a BMS. What I really want is a simple charger guarenteed not to overcharge any cell with simple single-strand monitoring loom terminal block built in.
first some assumptions/goals:
- as a mechanical DIY guy, I am not interested in huge amounts of flexibility, data recording, etc. I want to 'set it, and forget it'.
- primary goal is a safe, reliable on-board charger designed for LIFePO4 prismatic cells (TS, CALB, and the like).
- huge amount of flexibility is not required because once installed, I hope it lasts at least 10 years along with the batteries.
- minimum cost while meeting functional requirements is primary, but also important to minimize size, weight, and be sealed against dust, water durable with regard to cycle life, vibration, temperature, etc.
major functional specs:
- plug into 110v, or 220v, and self limit to no more than 15 amps so as not to blow the typical house breaker. I think the major slice of the DYI market is fine with a 6 to 10 hour charge time, and not about to install a dedicated high-amp line to the garage.
- have a built in interlock terminals that would pass thru the usual 13v key-on juice to the main contactor solenoid when not charging, and open the circuit when plugged in to prevent key-on closing the typical circuit. Eliminating the need for one external component.
- have multiple (perhaps 50) terminals to accept 24ga wire monitoring individual cells. one wire per cell, plus one. 50 would allow enough for typical packs up to 48 cells.
(this is the tricky part)
- have internal brains to scan thru all cell monitor voltages, and switch from CA mode to CV mode at a cell level as soon as any cell hits target voltage. When in CV cell mode, output amps would be ramped down as needed to hold cell(s) at or below target voltage. No real attempt made to shunt or balance, just monitor and ramp the charge down per the highest cell.
possible? is this kind of 'scanning' the problem, or is that not really very expensive to build?
The least expensive internal design would probably be to not even attempt to ramp down, but use a fixed target finish of something like 3.70v and just stop the charge as soon as the first cell hits the limit. One extra that would be nice if it could be done without too much cost would be user-settable finish voltage... perhaps pre-set to 3.70, but able to move up or down a little in .05v increments. Extras would be some external display of which cell hit the limit first with something as simple as an external LED. Slightly more complex might be internal settings to show 'yellow' when cell is within .05v of target, and then 'green' when at target. It would be a quick visual of balance to see if the first high cell is more than .05 higher than MANY cells, then it may need to be balanced down a little.
....so my question is whether there is already a simple foolproof relatively inexpensive charger like this I don't know about, or if ya'll think something like this would even appeal to the typical DYI as a minimum charger/monitor system at moderate cost.
I know I for one don't feel I need or want a super adjustable super smart charger with completely settable voltage rnges and data bus, nor do I want to spend $1000-$2000 for a BMS. What I really want is a simple charger guarenteed not to overcharge any cell with simple single-strand monitoring loom terminal block built in.