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Discussion Starter · #21 ·
Yes many lead batteries need high 14's -even 15V to get to true Full.

FLA usually higher than sealed, and only GEL down below 14V.

Each model has its mfg specs, if the manual / data sheets / tech support are not readily available, not a brand worth buying
Just my opinion, but SLA is not worth the trouble.
Heavy, big, low capacity, saggy...yuck!
I don't need that....not when I have lithium cells.
 

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Discussion Starter · #22 ·
I was not talking cheap chinese gear, more EV level BMSs in a higher price range.

Not recommending any of these specifically, but CAN messaging with a failsafe protocol, BMS fails terminates charging:

Emus
Orion
Elithion
EPS
ZEVA
I've looked at several of these brands before. I'm not really needing battery management at that level for the stuff I do. Maybe if I build a car someday...
 

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Discussion Starter · #23 ·
Yes many lead batteries need high 14's -even 15V to get to true Full.

FLA usually higher than sealed, and only GEL down below 14V.

Each model has its mfg specs, if the manual / data sheets / tech support are not readily available, not a brand worth buying
You could say the same about LION cells. You charge an 18650 to 4.2v to get it to full charge, but there's no point. The amount of charge above even 4.05v is so small as to almost negligable. 4.2v is well into the non-linear charge zone of a LION cell and meaningless. I bet with SLA, it is no different. Basicly anything over 12v is into the non-linear zone for SLA and not very useful. I pretty much dismiss SLA due to it's weight, size and capacity limitations...so I'm just guessing that this is the case.
 

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You could say the same about LION cells.
..
I bet with SLA, it is no different. Basicly anything over 12v is into the non-linear zone for SLA and not very useful.
Sorry but that's totally wrong. Lead datasheets spec'd voltage points vary very widely. Care requirements just do not translate between lead and lithium.

Yes for all LI family chemistries, sitting at low SoC is best for longevity, anywhere high voltage means shorter lifespan.

But all lead chemistries need to sit at 100% Full to get good longevity, including a long AHT specified by trailing endAmps usually 0.005C or thereabouts.

PSOC abuse drastically speeds up EoL bank replacement, as in every 2-3 years, as opposed to a dozen or more.


I pretty much dismiss SLA due to it's weight, size and capacity limitations...so I'm just guessing that this is the case
Yes lead is vastly inferior to LFP for mobile applications

But guessing about this stuff "out loud" is counter productive
 

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Discussion Starter · #25 ·
Sorry but that's totally wrong. Lead datasheets spec'd voltage points vary very widely. Care requirements just do not translate between lead and lithium.

Yes for all LI family chemistries, sitting at low SoC is best for longevity, anywhere high voltage means shorter lifespan.

But all lead chemistries need to sit at 100% Full to get good longevity, including a long AHT specified by trailing endAmps usually 0.005C or thereabouts.

PSOC abuse drastically speeds up EoL bank replacement, as in every 2-3 years, as opposed to a dozen or more.




Yes lead is vastly inferior to LFP for mobile applications

But guessing about this stuff "out loud" is counter productive
Sooooo...I admit my ignorance and that's counter productive? I'm not sure about your logic.
I readily admit that I'm guessing and that's bad? How exactly?
I have NOT done any research into SLA...AKA...admitting my ignorance on them.
I think this is healthy personally! I don't need to impress anyone and I have no problem admitting I don't know something.

Does SLA have a linear charge curve all the way up to fully charged? This is the ony thing I was referring to. I've spent some time looking at LION chemistries and they do not have a straight line charge curve. This is why I said what I said about NOT charging to 4.2v. I did not mention longevity or how to care for a specific chemistry, but that is also true. I was focusing on the fact that at 4.2v to around 4.05v LION has VERY LOW capacity in this voltage range. My assumption is that this is also true for SLA.

This is all off topic of course...since this is a charger thread.
 

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For lead batteries, if you do not get them charged to 100% Full

and keep them there while not being cycled (Float charge)

then you are abusing them, throwing money away, being stupid.

So the question as to how "linear the curve" is, is irrelevant.

We are not trying to balance capacity utilization with longevity

The two goals are not mutually exclusive as they are with LI

With lead, they are both served by following proper care practices.

Also btw SLA encompasses VLRA, which includes both GEL and AGM,

it is more of an umbrella category (not FLA) rather than anything specific.
 

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Discussion Starter · #27 ·
For lead batteries, if you do not get them charged to 100% Full and keep them there while not being cycled (Float charge)
then you are abusing them, throwing money away, being stupid.
Well maybe not stupid...I'd agree with ignorant or don't know better. And in that regard, I'll claim ignorance. I have to also admit that I don't really care very much either. It is SLA after all. I've had quite a lot of SLA batteries. Usually they just sit around and later (like a year or more) I'll decide to give them away or see if I can use one for something and the battery will be badly run down or dead. Some recover, some do not. I think you just explained why...they needed regular tending and just sitting there was bad for them. I do have an EV with SLA's in it. I guess I should pull out the charger so they "float" and not die.

Definition of stupid:
Slow to learn or understand; obtuse.
Tending to make poor decisions or careless mistakes.
Marked by a lack of intelligence or care; foolish or careless.

You can see why I don't think "stupid" is the right word usage here. I suspect if most people knew what SLA needed for care, that maybe possibly stupid would apply. Otherwise most people, myself included, are either ignorant of SLA care or simply do not care enough to find out.

I googled about SLA discharge curves. This is incredibly flat! I had no idea. Too bad lithium chemistries are not like this. However, I doubt I'll give up lithium chemistries just for a flat discharge curve.

 

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Discussion Starter · #28 · (Edited)
I built this charger over the weekend out of HP 230w PSU's that I picked up from ebay for $20 each. The PSU's are rated for 11.5 amps, but I know with some minor cooling they will deliver probably 1-3 amps more without issues. A real charger at this amperage and voltage can be bought for around $200 to $240 for those that are DIY adverse. Just my opinion, but where's the fun in that?! I like building my own from repurposed stuff and the reliability is pretty darn good. All told, my cost is $80 in PSU's, $20 for the watt meter and $36 for the 200mm fan = $135. This might not be a win to you if all you do is look at the cost, but these PSU's are really reliable and I could have done it without the fan. Do you have an 11.5 amp, 82v charger that cost you $100?

I used 4 of these exact HP PSU's. I call this a Rev 00 PSU. You can find other 230w HP PSU's and they will have Rev 01 to Rev 04 on the lable.



I won't bore you with the details, but if you look above, all the DC outputs are wired together just like I presented previously. I'm going to redo the AC chords so there is a single long chord with 4 short splits off of it instead of this mess. I put 1/4" wide strips of wood between the PSU's for airflow between them. Zip ties hold it all together.



I'm not quite done as this fan isn't mounted yet. I found a source for very cheap 12v PSU's. They are rated for 1 amp and are very small. They cost $2 each. Perfect for a fan! This 200mm fan is very quiet and massive overkill fpr the amount of cooling needed.


 

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Well maybe not stupid
yes if you do not care about longevity, fair enough

A decent size bank of quality AGM and GEL (better than cheap SLA) can cost many thousands of dollars.

Treated well may last 7+ years before hitting EoL at say 75% SoH

If you had to replace them every 2-3 years

I would consider that stupid.
 

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Discussion Starter · #30 · (Edited)
The HP 230w 82v charger is done. I decided to mount the fan and never use it with just passive cooling. I intend to use it at more than the 11.5 amps the PSU's are rated for and that will need active cooling. The fan blades didn't quite clear the PSU's so I put it on 1/4" stand-offs to lift it away a little and then filled in the gap with high density foam weather stripping. The fan is a puller instead of a pusher with the exhaust side out the grill. Pushing air into something needing cooling is better than sucking it through.

Last night I reworked the AC power cord and added a small extension for the 1A, 12v power supply for the fan. Since I was redoing the AC cord, I found 4 with similar looking connectors on them so they all match now. The 12v PSU has a JST connector on the AC and DC sides. 2 pin on the AC side and 3 pin on the DC side so they cant get connected incorrectly. If needed I can disconnect it easily. Since the amperage is so low, JST connectors are fine for this. The small AC wires are buried in hot glue at the JST connectors. Some heat shrink around that adds a second layer of electrical isolation so that getting shocked is remote. The 12v PSU is inside clear heat shrink. It's wires are secured with hot glue to the PSU board.



The reworked AC cord and 12v PSU.



The completed charger. I ran it for a little while on my Zap scooter, but it's at near full charge already so that's not a good test of the charger. The charger fits nicely in the under seat compartment if I want to take it with me.

 

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Discussion Starter · #31 · (Edited)
A decent size bank of quality AGM and GEL...
I like debates as much as anyone, but this is a Make Your Own DIY Charger thread. Let's stay on topic please. Batteries and debates over them are not relevant here. I'm not innocent as I should stay on topic too. If you have suggestions on improving DIY chargers, please post on that topic. If you have built your own charger I definitely want to see that!
Thanks
 

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Discussion Starter · #32 · (Edited)
A couple of ideas I'd like to implement:
***DIY chargers are based on fixed voltage PSU's. Charger voltage does not track slightly ahead of pack voltage to create constant current.
***If you have implemented the below ideas, please post your work. IF you have ideas about how to implement them, please post that too.

1. Active current limiting: Use an ACS current sensor, mosfets and op-amps to control the linear region of the mosfets to maintain a current limit that adjusts as current draw into the pack changes. I have found a small board that has most of this on it already that I'll eventually get around to trying out.

2. Cut off: I think the ACS current sensor could provide control to mosfets for disconnecting DC out and to control a relay to shut off AC power as well or both via a dual pole relay.
 

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Discussion Starter · #33 · (Edited)
Resistor current limiters:
I have been using resistor banks for current limiting for many years. It's cheap, easy and simple to implement. They do get quite warm and adding a heat sink and fans keeps that heat down. The voltage drop across the resistors is a nice power source for the fans. Most brushless DC fans will run on a fairly wide range of voltages so this works pretty well. At first the voltage drop is high and the resistors are making a lot of heat so the fan runs faster. As the voltage across the resistors drops so does the heat they are making and the fan slows down. It's a natural feedback loop.

This could be a current limiter and I have used it at 82v. The "T" made of an XT30 and 2 XT90's lets it be used as a charger current limiter, but that's not it's intended use. It's intended to safely discharge cells to dead flat. I have a supply of scrounged 18650's and recently capacity tested all of them to find everything at 1300mah or less so they could get recycled. I put them in 18650 battery holders all in parallel and used this resistor bank to discharge them for recycling. Anything above about 2v runs the 5v fans. Anything below that and the resistors barely get warm and the fans are not needed.





This is my recently built current limiter for the laptop PSU chargers. With the new HP 230 watt charger now built, I need to add a few more resistors to it. It was built around the Lenovo 190w PSU current limits. I think a rocker switch and a few more resistors can make it work for both. The resistors are glued to the heat sink with thermal glue. The rocker switch you see in the first picture bypasses the resistor bank once current draw drops off sufficiently and pack voltage is close to full charge. The dual 12v fans and the heat sink do a good job at keeping the resistors cool enough to hold comfortably in your hand. As is, it's meant for use at 82v into a 20S pack. Adding a 7812 linear regulator could make it usable for higher voltages like 32S or 36S so the fan voltage limits are not exceeded.



 

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Did I understand correctly that you said the HP power bricks were voltage adjustable?

I'm looking for a low cost solution for reliabily charging 14S7P 21700 batteries I'm building for some sprint kid karts. Max charge rate I'd want to use would be 4.2 Amps (1C), but something less than that is very acceptable. While my high-power adult kart uses a $$ can-bus charger with an $$$ Orion BMS, that is totally overkill (and a big added expense) for the kid karts that don't need rapid charging. Open to suggestions.
 

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Discussion Starter · #35 · (Edited)
Did I understand correctly that you said the HP power bricks were voltage adjustable?

I'm looking for a low cost solution for reliabily charging 14S7P 21700 batteries I'm building for some sprint kid karts. Max charge rate I'd want to use would be 4.2 Amps (1C), but something less than that is very acceptable. While my high-power adult kart uses a $$ can-bus charger with an $$$ Orion BMS, that is totally overkill (and a big added expense) for the kid karts that don't need rapid charging. Open to suggestions.
For your uses or 57.4v at full charge you might be able to get away with 3 HP PSU's without adjusting anything. They are all slightly under 20v as far as I can see so that ought to work to your advantage. Of course this will charge at around 12 amps if you use the HP 230w PSU's. Lenovo makes a 90w PSU that will deliver the current you mentioned. My first ever laptop PSU charger was made from 4 of them. You can buy them on ebay for around $15 each. If you really want that low of a charge current, there are tons of chinese chargers that cost $40-60, are adjustable and deliver 3-5 amps. I want lots of current and cheap so I build my own chargers from repurposed PSU's.

Rapid charging...not sure what you think is "rapid". My definition of "rapid" might not be the same as yours. A 30Ah pack charging at 30 amps will take about an hour. That's pretty quick IMHO. 2 HP PSU's in parallel will deliver 22-24 amps. Into a 30Ah pack that's just a little over an hour charge time. A big reason I built this 230w HP charger is I thought the 190w Lenovo charger took way too long charging the Zap scooter. My 3 packs in the Zap total about 130ah. At 9-10 amps from the Lenovo charger that's about 13 hours. This charger at 12-13 amps will shave a couple of hours off that. I could use the Lenovo and HP chargers in parallel to boost that to around 22 amps or 6 hours.

Above I showed stuff about my Super Charger project. It will deliver about 30 amps once it is done. I set it aside to work on other things as it was "less important" and needs lots of time to get it finished enough to use. With these stupid long charge times I have, it has become more important to me. 30 amps into 130ah will reduce charge time to about 4.5 hours...which I think is "rapid enough" for my needs. This charger needs a dedicated 40 amp circuit. It does a maximum of 4430 watts or 37 amps at 120v AC. I can't plug it into any old wall outlet without immediately popping breakers!

Most switching PSU's are adjustable. There will be a control chip inside most any of them. The specifics vary a little. Some have 2 resistors that make a voltage divider. They can easily be replaced with a trimmer POT. Some use a zener diode and resistor to create a reference voltage. These ones can often times be adjusted by replacing the resistor with a trimmer POT. Some need a different zener. PSU's like come from Meanwell place a trimmer POT where you can get to it easily to adjust the voltage.

Purpose made PSU's are "set" in one of the 3 ways I just mentioned to some output voltage. HP, Lenovo, Dell and many other laptop PSU's are set to 20v or are supposed to be close to that. All you need to do is open up the PSU, find that voltage divider or resistor and zener and set them to the voltage you want. Most switching PSU's have a range they will work at. A 12v Meanwell will adjust down to 9v or up to 15v. Laptop PSU's will have a "range" too.

My HP 230w charger I just built is making 79.9v and I want 82v. I'll be taking it apart again. Then looking at the PSU board to figure out the adjustment circuit. I assumed they were making 20v or a little above as this is pretty common. I was not expecting them to be a little under so I never checked their individual voltages. Live and learn...should NOT have assumed...FML!

HP 230w PSU's come in several revisions. The ones I used above are the original 230w PSU's. They have no REV number on the label. I'll call this REV 00. There is also REV 01 to REV 04 that I have seen. I have two 03's and an 04 that came in the batch of 6 I originally bought. I didn't notice this until I had purchased the 6 PSU's and then was looking them over. I have taken the shells off a REV 00 and a REV 03 and they are not alike inside. If you are considering making a charger, probably getting all the same REV PSU's is a good idea. This will make figuring out how to adjust them all the same too. Why there are 5 revisions of these PSU's is not known to me right now. Maybe there were issues with the earlier versions? Maybe it was done for value engineering and making them cheaper? My charger is made from 4 REV 00 PSU's.

I have since checked the voltage from a REV 03 and a REV 04 and they are both lower than 20v. I'm wondering if the factory did this for HP on purpose? This probably means you'll get any HP 230w PSU and need to adjsut it no matter what. FEH!
 

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Discussion Starter · #36 · (Edited)
My last few posts were about the HP 230w PSU's and building them into a charger. The charger I made was from the rev 00 PSU's. They lack current limiting and just shut off if they overload. They need an external resistor bank to limit current to under that 11.5 amps max. I've been using the charger I built previously quite a lot for the past few months. Other than the less than 82v output, it has worked well.

I've wanted to explore the later revision PSU's to find the voltage control circuit since I discovered they existed. My assumption is that each new revision fixes issues with older revisions. I finally got around to it...

I've recently acquired more of the rev 03 and rev 04 PSU's and been scrutinizing the circuitry so that the output voltage can be adjusted. I believe they do current limiting unlike the older variants. HP sets the PSU's to 19.5v. 4 of them in series is 78v. I can't use them to charge to 82v without a little tweaking. I found the circuitry that adjusts the output voltage.

NOTE 1: The 3 large through holes at the left of the board are as follows. Inline with the shunt is negative. In the middle is positive. The smaller through hole is the control signal...which you don't need for a charger.

NOTE 2: I replace a precision resistor with a 10 turn POT. A small adjustment of the POT creates a significant change in the output voltage. I don't recommend using a trimmer POT. They are simply NOT accurate enough for the small changes in resistance needed.

NOTE 3: The rev 03 and rev 04 variants both use the same AP4310 dual op-amp package. It has an internal voltage reference (zener).





This is the rev A03 voltage and current control section. The trimmer POT above and left of the IC sets the current as measured as a voltage drop across the 2 milliohm shunt resistor at the left. It does NOT adjust voltage! Right below pin 3 is a precision 10.3K resistor. This resistor sets the output to 19.5v.



I unsoldered the precision resistor and used 2 small wires to add a 20K 10 turn POT in its place. I can now adjust down to about 7.5v and up to 25v. Go much lower and the switcher shuts down on its own. I think 25v is its maximum. I'm impressed at the output voltage range I got from the PSU!



The A04 variant is slightly different. The resistor is about 5.3K to set 19.5v. A 10K POT ought to work in place of the resistor.

 

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Discussion Starter · #37 ·
OK OK...NOT a DIY charger...LOL! It is a charger, so I'll post it here anyway. The idea is to add DIY onboard J1227 charging to my EV's.

I found this charger on aliexpress. Anyone selling these chargers will want you to specify your pack type, cell count and the connectors you want on the charger cables. It is set for 82.3v and supposedly capable of 30 amps.


I believe I found the manufacturer for it. The seller was NOT remotely helpful in this regard and insisted that the charger could not be set to some other voltage. I disagree! It got set "somehow" and these chargers can be purchased for use at all sorts of voltages and pack chemistries. OF COURSE they can be adjusted!


It's a bit larger than I imagined. I'm not sure how I'll mount it onboard my Zap scooter. I don't think I have a space that is large enough. Losing the handle will help, but not a lot. I've bought parts so I can make up a Y cable for plugging into my drier outlet. This will give me easy access to 30 amp 220v power for the charger. I'll see about setting up J1227 on the Zap once I have the charger mounting worked out.




The 2 JST connectors are for external options I opted to NOT get. I thought they were poorly executed so I didn't ask for them.








PIC16F1936 micro controller. The 7 pin connector is the programming port. I've never messed with PIC programming, but I bought a PICKit3 so I can give it a shot. This is the only way that I see of changing the output voltage. I'm pretty sure it can be adjusted down to about 60v and up to about 90v. Maybe it uses a voltage divider to set the output voltage? I haven't spent any time analyzing the IC's on the control board to determine if this is the case or not. I really think output settings are programmed in the PIC.

 

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Discussion Starter · #38 ·
If/when I discover how to reprogram these chargers for any voltage, I'll make that public here. I really hate all this trying to keep things secret nonsense! Gotta love(hate) Tesla, Apple and others for trying to do the same thing! Just me perhaps, but I'm a strident advocate for "Right to Repair"!!!
 

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Discussion Starter · #40 · (Edited)
Try this guy on eBay

seller:barbjb
He's a good guy! His real name is Dave. I've known him since 2016. We do EV stuff for each other from time to time. One of my favorite people! Me and a buddy in California were just talking about Dave a couple of days ago. We've both had many pleasant and positive experiences with him.
 
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