# Build your own DIY charger



## rishimaze (May 23, 2021)

Hi everyone,
I'll present several options that I know work super well since I have been using them myself since 2015 without issues.

Expect to need to solder wires together, buy parts on ebay or amazon and to do some wiring while you build your own DIY battery charger. I'll present 16S and 20S LION chargers I have built and use or have made for others.

A little about me...
1. I have been a hobby electronics experimenter since the 1970's.
2. I read stuff, buy stuff, try it out and see for myself if something is workable or not.
3. I don't care if you like what I do or how I do it. I'm presenting my work and my results.
4. Feel free to copy my efforts. This is why I post my work.
5. I really don't care if something was intended for XYZ job or not. CAN it do the job?
6. I build at my own risk. I assume you will too since this is DIY!


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## rishimaze (May 23, 2021)

DC-DC BOOST chargers: (MEH!)

I don't recommend building a charger this way, but it can be done. Chinese BOOST converters are not very good and you need to seriously derate them or else they overheat and burn out. If its "rated" for 1500 watts, divide that by 3 or 500 watts at least to "guess" at real world wattage. I messed with beefing up a couple of the better Chinese BOOST converters and got them to about 60% of their Chinesium (massively and overly exaggerated) ratings. 

This was 2015. I started here as an experiment to see if a single ATX power supply could be boosted to 82v and be used as a charger. I had several ATX PSU's so I got some 500w BOOST converters and started experimenting. This charger saw use for about a month, but the DC-DC converters were garbage and so was the ATX power supply so I abandoned it. The DC-DC's would over heat and burn out at 20% of their rated amperage so they each got a fan and I used 3 in parallel to get a fiddling 4 amps at 82v or about 320 watts total. Basically, it sucked in every way possible. Great experiment that was ultimately garbage.










This 2016 charger is a qualified success. The 1200w BOOST converters are really more like 400w each. It did fine at 9 amps total at 82v with active cooling. One fan blows air in between the heat sinks and the other sucks it out. I later added a cover over them so it created a wind tunnel in the space. These DC-DC's don't do current limiting very well so I added a couple of resistors to help with that. You can see them in the second picture. This charger is still in use today. The single SE-600 24v PSU is turned up to its maximum output to help with DC-DC conversion efficiency as much as possible...which is maybe 75-80% efficient.


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## rishimaze (May 23, 2021)

Lenovo 170w laptop PSU chargers:

NOTE 1: Buy legitimate Lenovo laptop PSU's. Do NOT buy the Chinese knock-offs thinking you are going to save a few dollars. You won't! They suck and are unreliable and the output isolation is 100% dodgy! 

NOTE 2: You need PSU's that have 100% DC output isolation from the AC input. Lenovo PSU's have this. They have current and temperature limiting so they are quite hard to burn out. They can get pretty warm over and over again and be unharmed. Lenovo did not scrimp on component quality in these PSU's. A 170w PSU will deliver about 9 amps...since they are slightly under rated.

I started with the smaller 90W PSU's. I had 10 of them given to me so why not? I built one with 4 PSU's in series and it made 81.5v and delivered about 4.5 amps. Not too shabby for 100% free! I used that charger for about 6 months before giving it to a friend as I had built one from the 170w PSU's and the 9 amps was getting my pack charged much faster.

This was the first 170w Lenovo PSU charger I built. I guess I have made 5 or 6 of them for people since 2016. This is a great charger solution that is cheap and reliable. The caveat is that it only works in 20v increments. If that's doable for your pack, this is a good solution. I used JB weld to hold the PSU's together. It got used at my office to charge my EV. No fans is very quiet!










This is my current Lenovo PSU charger. I built it in 2018 and it sees regular use. I wanted more of a "brick" instead of a "slab" so it could fit in the under seat compartment of my scooter. I used 1/4" x 1/4" sticks between the PSU's so air could get between them. I see 9.7 amps on the watt meter all the time when charging.










AC cord setup:

1. You will be cutting up the AC cords. You need 1 AC wall plug and 4 of the oval connectors into the PSU's. I cut off 4 cords right at the wall plug and all at the same length. One cord was extra long so that got used for my wall plug. You will be making a single AC cord with 4 parallel connectors on it for use at 20S or 82v out. Adjust for your output voltage needs.










2. The ends got stripped off about 1/2".










3. Holding 4 cords together while you get solder to flow into the bared ends isn't so easy. A zip tie to hold them bundled together really helps. This is the 4 ends that plug into the PSU's all soldered together.


















4. The wall outlet end gets 3 pieces of heat shrink on it like this. You'll see why in a minute.










5. Wall outlet plug ends soldered to the PSU AC input ends.










6. Those smaller and shorter sections of heat shrink isolating the 2 AC conductors from each other.










7. The larger and longer heat shrink in place to protect even further. The zip tie keeps from stressing the heat shrink and the solder joints inside.


















8. The completed AC cord with 1 wall plug and 4 plugs into the PSU's. This may seem like the wall plug will get way to hot with all that current draw, but it doesn't. 170w/120v = 1.41 amps.


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## rishimaze (May 23, 2021)

Lenovo 170w laptop PSU chargers 2:

DC output series connections:

1. The DC cables have a ferox core in them right before the DC connector. I cut off the cables right before the ferox core and at the maximum equal length for all 4 PSU's. Not all DC cords are the same length.










2. Bare the ends like this for each DC cord and tin the ends of both wires. White is +20v and bare is ground.










3. This is eventually what you are going for so that the DC outputs of the PSU's are in series, but not quite yet. The single white wire will be +82v and the bare wire ground.










4. You can see what happens if you just heat shrink over those solder connections. The bottoms of each bare wire are still exposed. Short them together and BAD things happen!










5. I heat shrink each bare wire. I also add heat shrink so it can be slid over the exposed bottoms so there is nothing exposed to cause shorts. You will need to slide on a section of heat shrink like this first.


















6. When that section of heat shrink is pulled up and all the wires are soldered together in series, there is nothing exposed to cause problems. The 2 bare ends should measure about 80-83v across them.


















7. I add 2 14 awg wires to the bare ends, heat shrink the solder joints and then heat shrink the whole thing. I've temporarily used a zip tie to hold it all bundled together as I work. It got cut off after a few minutes. A larger section of heat shrink went over all of this and then another 2 zip ties hold the wires bundled together so nothing gets stressed.










8. I use watt meters. I like to see voltage, amp draw and capacity. There are quite a lot of inexpensive watt meters out there that work well. This one does great at 82v and less than 20 amps. You can find them on ebay or amazon for about $20. The ground wire gets the internal shunt for current sensing. The meter needs to measure voltage and to get powered so all you need is a tiny positive wire. Secured together like this lasts a long time. IF you are worried about those exposed screw heads, put some hot glue over them.



























9. The other ends get stripped, tinned and heat shrink is added so they are ready for your charge connector.










10. I really like XT90 connectors. They are cheap, easy to find, durable, keyed so they can't get plugged in wrong and handle 90 amps. You can also get panel mounts for them. In the EV is the male connector and I use a female connector as a weather boot to keep out dirt and water. Some hot glue over the 2 exposed posts protects from shorts or electrical danger. All chargers and EV's since probably 2017 that I build, get an XT90 female connector on the charger and a male on the EV.










That's it! Happy charging!!! I have built more of them than I have pictures. Here's 2 I built for me and one I built for a friend.


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## rishimaze (May 23, 2021)

HP 230w laptop PSU teardown:

I recently discovered these HP PSU's and since they are good for 230w or 11.5 amps at 20v, they seemed rather compelling. The cost for used ones is around $23 each on ebay.

I want to show the internals of the HP PSU's they are nicely made and look to be easy to modify for output voltage adjustment. My next laptop PSU charger will be made from them. I have purchased 6 for when I get around to doing it.

I thought the Lenovo 170w PSU's were huge for a laptop. These 230w PSU's make that look small! Both PSU's have rubber feet on the bottoms hiding 4 screws. Take them out and the plastic covers come off.










The HP PSU's have RF sheilding. There is 1 solder connection, metal clips and a small piece of tape holding them in place. A Lenovo PSU is many layers of tape, unsoldering, clips, screws and glue holding its RF shielding together. Can you say "overkill"?










































There is a plastic electrical shield over the exposed circuit board that peels off easily. The cured thermal glue comes up pretty easily and there is only one spot where it needs to be removed to get to the components under it. What takes an hour to get to in a Lenovo PSU, takes 3-5 minutes in an HP PSU.


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## rishimaze (May 23, 2021)

Meanwell based 25-30 amp chargers:

NOTE: If you are looking for a quiet charger, this is NOT it! The PSU fans are noisy.

NOTE: Your AC circuit may not be able to deliver the current requirements of these chargers. Watts is watts. At 82v and 30a, that's 2460 watts. At 120v AC, that's 20.5 amps. I added a 30 amp circuit in my breaker panel to accomodate my chargers.

NOTE to the skeptics: BOTH of the chargers presented below have seen regular use for many years without a single issue. I'm one of many people that have done this with great results!

I use Meanwell SE-600, 24v PSU's. They are rated for 25 amps. You can push them a bit more to just short of 30 amps before they shut off. 16S or 66v is 3 PSU's in series. 82v or 20S is 4 in series. I set all my PSU's to the same voltage so they share the current load equally.

You can find Meanwell SE-600 PSU's on ebay, amazon, Jameco and other places. I buy them where ever I find them for the lowest price. Expect to spend about $75 for a new one. They have over load and over temp protection. They shut down without damage.

Meanwell groups their PSU's based on feature set and wattage. SE-600 are all 600 watt PSU's. However, depending on the output voltage you will see more or less amperage. I have a 12v SE-600 and it is rated for 50 amps. The 24v SE-600's are rated for 25 amps.

The charger build:

1. Like the Lenovo chargers, all the AC inputs are in parallel. There is a rocker switch that disconnects the hot wire to turn off all 3 PSU's at the same time. Since all 3 PSU's are stacked vertically in the 66v charger, it was easy see how I ran wires to all 3 AC input screw terminals. I wrapped the bare 14 awg wires in kapton tape to prevent getting shocked. My 4 PSU, 82v charger is set up the same way, but the physical placement of the PSU's is different so it's less obvious that the AC inputs are all in parallel.


















2. It is not easy to see in the image, but the top most PSU is the "lowest" PSU in the series. Just like batteries in series, + of the top PSU connects to - of the middle PSU. + of the middle PSU connects to - of the bottom PSU. The bottom PSU is the "highest" PSU in the series. Each one is set to 22v for a total of 66v. I did some checking and the PSU DC outputs are isolated to 1000v. The chances I'll exceed this are remote!










3. You need a way to NOT exceed the current limits of the PSU's. Charging starts out with the battery pack taking in current very rapidly. As charge level increases, the pack "slows down" taking in current. I need to account for this as lower charge levels can easily over come the current capabilities of the PSU's. I used resistor banks for this. On my 82v charger is a row of 3 ohm, 100w resistors in parallel. There is a small rocker switch in parallel with them so they can be bypassed when charge current drops sufficiently. These 7 resistors get pretty hot! The 66v charger uses 10 ohm, 10w resistors. I had a lot more of them in parallel. The advantage is the heat/wattage was dissipated across a lot more resistors so that none of them got very warm. I'm adding resistance in series with the output of the PSU stack to keep total current draw under the maximum limits of the PSU's. Once current draw into the pack drops sufficiently with the resistors, I can flip the small bypass rocker switch and charge direct from the PSU's into the pack.


















4. I like having a watt meter on my chargers. This informs me about pack charge capacity, voltage and current. Inexpensive watt meters can be found on ebay, amazon, aliexpress or banggood easily. Be sure it can handle the amperage and voltage you need. Some meters need to be powered separately from the measured voltage. I like compact meters that include an internal shunt for chargers, but that's not an option above about 20 amps. My 66v charger started with this little black watt meter, but it's limited to 20 amps so I had to replace it with one that used an external 50 amp shunt like you see on my 82v charger. The shunt is just below the meter in the 3rd picture.


























5. I have found that for 30 amps or less that 14 awg silicon wire works nicely. It never gets warm. I'm part way into building a "super charger" from 8 SE-600 PSU's and I'll use 12 awg wire for it since it could see 4428 watts. These chargers are a bit large and heavy. You need your charge cable to be long enough to get to your EV so you are not lugging around the charger. My super charger is 8 of these PSU's. I'll be putting it where I want it to sit forever and bringing the EV's to it. The charger output cable needs to be long enough to reach the EV to be charged.

6. The resistor bank, current limiting solution is an efficiency concern. They do make a lot of heat when used. Incandescent or halogen bulbs won't reduce the waste heat, but it's another way for less component cost to keep the current draw under the PSU limits. My super charger will possibly use halogen bulbs instead of resistors.

7. I am toying with a couple of mosfet based ideas for current limiting. I still have the waste heat, but they are automatic and there is no need for a manual bypass switch. I found a ready made board that uses an ACS current sensor and a differential op-amp. It can be adjusted to account for the current limit I want. The output can be used to drive mosfets in their linear zone to create resistance. The important detail is keeping the mosfets cool. At lower charge levels, the board will turn on the mosfets only part way. This will be like my resistor bank in place. As charge current drops off, the mosfets will turn on a bit more thus lowering their internal resistance. Once charge current stays below about 25 amps, the mosfets can turn on fully.


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## MattsAwesomeStuff (Aug 10, 2017)

A bit ghetto, but, if it works it works.

I like a well-documented project, thanks for sharing.

I've done the same for my electric scooter charger, 3 different laptop packs gives me around 60v, which is what 4 lead acids can be topped up to. Added a little 1U fan next to them to keep them from overheating, and, it's never caused me a problem.


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## john61ct (Feb 25, 2017)

All of these devices are DC-DC Converters, or AC-DC PSUs, rather than "chargers"

Ideally an HVC would isolate the charge source input

so inattention, dozing off etc does not risk causing thermal runaway

boom bad


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## rishimaze (May 23, 2021)

The Super Charger:

From my 82v and 66v Meanwell chargers, I have 7 SE-600 24v PSU's. I bought an 8th PSU to build all of them into the Super Charger. For now, I'm using smaller chargers for my EV's until this project is done. I do miss that 25+ amps!

1. This charger will have the capability of producing 12S/49.2v, 16S/65.6v, 20S/82v, 24S/98.4v, 28S/114.8v, 32S/131.2v and 36S/147.6v. The outputs of the PSU's will be set so that this is accomplished at different locations though out the entire 8 PSU series.

2. Only the PSU's needed to provide the DC output voltage will be powered.

3. Since there are 7 potential output voltages, the correct DC output needs to be selectable.

4. A single watt meter capable of better than 150v and 30 amps is needed.

5. A single rotary switch will select the PSU's to power on and the correct DC output location among the 7 possible.

6. The current limiting needs to be automatic and universal to all DC output voltages.

I've redrawn schematics several times to get this as simplistic and reliable as possible. Many design ideas later, I finally came to this fairly tidy solution that does not require a high amperage rotary switch, isolates the AC and DC sides and doesnt require triacs or mosfets or other special parts. This schematic is close to the final design, but I have since had a few more ideas that change this somewhat for added safety, shut-off at low current draw and a few other things.










This is a work in progress. My old 82v charger was added on top of the other 4 PSU's and has been partly dismantled, but not completely. The AC chord for the 82v charger got slightly warm at the outlet. It's now inadequate and will get replaced with something larger.


































1. This is the 8 position rotary switch. 3 sets of its 4 poles are all in parallel. They are rated for 10 amps so that's enough with 3 in parallel for my DC output switching. I won't be switching the outputs under load so there is little chance of arcing issues. The 4th pole is for selecting the correct AC output to turn on only the required PSU's. The switch contacts don't apply AC power to the PSU's. Position 1 is off. No DC output is selected, but AC is applied to the first two PSU's via rocker switch SW2. AC is disconnected from everything else. Position 2 on the rotary switch is 12S, 3 is 16S and so on.










These 12v relays apply AC to the other 6 PSU's. They are rated for 10 amps per contact which is double what is needed for each PSU. They have 2 poles in them and I am using them in parallel. They get "selected" or rather their coils get powered by that 4th pole on the rotary switch. The small DC-DC converter converts the output from the first 2 PSU's to 12v for powering the relays.










I probably need to do this wiring a bit differently to the 6 relays. A single hot wire to all 6 relays might be pushing it. I might need a distribution block so each relay gets a separate hot wire. There's a potential of 30 amps AC across 6 relays. I'll know soon enough if that single wire to all 6 relays gets too warm. It should be OK.










This is the current sense board that I'll use to drive the mosfet bank for automatic current limiting.










I have a couple more ideas in mind...

I found a monitoring board that has settable thresholds. I can set it based on a voltage. Using the current sensing board to provide the DC control voltage to it would work. When current draw drops below some low threshold, I could use one of its outputs to deactivate a relay that disconnects 12v to the relays. This would power off all the PSU's when charging current drops below a threshold.
I want the watt meter powered long after charging is done. I'd like to turn off all 8 PSU's when charging is done. I need the watt meter to stay powered so I can see final pack Ah. A small independent 12v PSU could do this and could also provide power to the relays. This eliminates the DC-DC. All 8 Meanwell PSU's would only get powered up when rotary switch position 2 or above is selected.


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## rishimaze (May 23, 2021)

john61ct said:


> All of these devices are DC-DC Converters, or AC-DC PSUs, rather than "chargers"
> 
> Ideally an HVC would isolate the charge source input
> 
> ...


I use switching PSU's as DC-DC's. Bypass all the AC stuff into the PSU and go right to the HV electrolytics and you have a DC-DC converter. Some PSU's work well for this, others not so much. 82v is pushing the limits for something designed around 120v, but I've found a few PSU's that will work like this.

PSU's only make the voltage they are set to. Meanwell makes reliable and trustable products. Same for Lenovo and HP laptop PSU's. I know output voltage immediately when the charger is powered up. The watt meter displays charger voltage. I use smart BMS's and set pack and cell HVC's appropriately. I test the C- mosfets to make sure they work so that if there is an over voltage situation, they will shut off charge current. That's redundant safety measures. Another safety measure is not really needed. I have gone to bed many times (years) after starting a charge to wake the next morning to a fully charged battery pack. I do tend to go look at charge status from time to time just in case, but my comfort level is pretty high with this charging solution.

On that topic of "boom". I have tried to get cells to burst into flames and to date failed.
1. I had an 8000mah 12S LIPO pack with no BMS in 2015. I connected the SLA charger that came with the EV and walked away. SLA needs 13.8v to charge to 12v or 55.2v total. I had a charger set for 49.2v for my LIPO pack, but dumbly grabbed the wrong charger. I came back much later to check on charge status. 55.2v into 12S LIPO is 4.6v per cell. All 12 cells were seriously OVER charged! I freaked out! I grabbed the pack out of the EV and hauled it over to bare concrete floor. It was really hot and waaaaay over charged! I let it sit until it cooled down and then used an incandescent bulb to bring down it's voltage slowly. That pack got used as is for another 6 months. I then took it apart and reused its cells for 20S for another year.
2. I had a 3S 750mah LIPO pack and a 4S 16,000mah lipo pack. Both fully charged. I connected them in parallel. Yes...parallel so the 3S pack would get a HUGE current dump from the much larger 4S LIPO pack. I wanted to see what would happen. The 3S pack after 10-20 seconds started puffing up and all 3 cells burst open. A small puff of smoke was all there was.
3. I've seen videos of people driving nails through LIPO cells and they burst into flames. OK..let me try that. Boring! 3 fully charged LIPO cells from a Multistar pack each with 3 nails in them. A little smoke around the holes, a little heat in the nails, a little sparking in the holes...no fire or explosions.
4. I charged a LIPO cell and then used scissors to cut open the pouch and unwrap the internal layers, they did warm up and there was a pungent odor, but again ZERO FIRE!
5. I have hundreds of used 18650's. If they drop below 1500mah capacity, I drain them to dead flat and recycle them. I had 10 cells like that...let's see what we can do with them. I soldered 14 awg bare copper across the battery posts of 5 so each cell was dead shorted. Never mind what the heat from soldering did to the cells! They got hot...too hot to touch. No fire, no leaking liquids, nada. Once the cells were run down, they cooled off again. BORING!
6. I took one of those lower than 1500mah cells and slammed it on the concrete floor over and over again. It did eventually split open and leak. No fire, no smoke...nada! Bugger!
7. I can spot weld battery packs with my KWELD. I had a bunch of brand new 3400mah Panasonic cells I was using for a new pack. I had the KWELD turned up far too high and blew right through the bottom of a charged cell. The spot welds immediately started leaking clear fluid. The cell warmed up a little. No fire!

I have seen videos and read about battery fires, but I sure can't get one to happen! AND not for lack of trying either! 

I used to be a fire fighter. The other shifts, they would get calls for fires all the time. Any shift I worked...never. After a while, people started associating this with me being on duty and so I acquired the nick name "Silver Cloud". We didn't really believe it, but the truth was, 6 years as a fire fighter and I never went on a fire call! The closest I ever got was some smoldering grass in a ditch from a lit cigarette. It was out before I ever arrived on scene.


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## rishimaze (May 23, 2021)

MattsAwesomeStuff said:


> A bit ghetto, but, if it works it works.
> 
> I like a well-documented project, thanks for sharing.
> 
> I've done the same for my electric scooter charger, 3 different laptop packs gives me around 60v, which is what 4 lead acids can be topped up to. Added a little 1U fan next to them to keep them from overheating, and, it's never caused me a problem.


If "ghetto" means DIY, then yup...all the way!
Thanks...I try to make what I do reproducible by others. Pictures and lots of explanation help.
That's a bit high for SLA. The need 13.8v to charge to 12v. 60v is 15v per SLA battery. It's probably not a huge deal. My Expedition runs at 15v since it was new in 2005 and it doesn't kill car batteries.


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## john61ct (Feb 25, 2017)

My take, BMSs are there as failsafe backup for when the primary regulation / stop-charge fails.

Obviously different battery types have different levels of risk

and each owner has their own tolerance, circumstances, e.g. kids around? other families?


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## rishimaze (May 23, 2021)

john61ct said:


> My take, BMSs are there as failsafe backup for when the primary regulation / stop-charge fails.
> 
> Obviously different battery types have different levels of risk
> 
> and each owner has their own tolerance, circumstances, e.g. kids around? other families?


It is a good point. I would not depend on the BMS protection by itself either. For example, knowing a charger is delivering 82v to a 66v pack and depending on the BMS C- mosfets to stop any over charging is risky. This leaves a single point of failure with no redundancy.

Reliable PSU's producing a known voltage such as 82v into an 82v pack is in itself fairly low risk. The battery pack can't charge to 90v or whatever in this scenario. It would require something going badly wrong in a PSU for that to happen.

Between using highly reliable PSUs that run and run and run for many years without issues and also having the BMS protection, this is pretty safe. I've been charging this way since 2015 without incident. All my EVs have LIPO or LION batteries. These chemistries are the most "volatile" of the lithium options. It's possible to have a problem, but then so is dying of a sudden anurism.

My super charger will implement a cut off when charge current drops below a threshold. I'm doing it mostly becasue all those PSU's running after they are no longer doing anything is pointless. It will also add another layer of protection...just in case.


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## john61ct (Feb 25, 2017)

Yes, so three elements here.

PSU or DCDC charge source

2. an extra device to automate charge termination, really no CV/Absorb cycle is required for LI, CC-only is fine HVC is KISS, simple is more reliable.

3. a BMS for protection against failure of either the two above.

A proper charger incorporates the first two.

Some BMS control the process very reliably but then an HVC can play failsafe.


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## rishimaze (May 23, 2021)

john61ct said:


> Some BMS control the process very reliably but then an HVC can play failsafe.


 I know...off topic to my thread...but related to batteries...

What do you consider to be a reliable BMS?

I've been using Xiao Xiang or BDS smart BMS's for a number of years. I've tried a few ANT BMS's, but the android app for them is not as usable as the BDS app. As far as I know, BDS does not make more than a 31S BMS and ANT does. There's a few others I've considered trying, but the BDS BMS's do most of what I think I need in a smart BMS. If you have other smart BMS's that you think are better, please post them. I'm always open to trying new stuff!


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## MattsAwesomeStuff (Aug 10, 2017)

rishimaze said:


> If "ghetto" means DIY, then yup...all the way!


No, by ghetto I mean prioritized for low cost and scroungeability above safety, reliability, effectiveness, etc.



> That's a bit high for SLA. The need 13.8v to charge to 12v. 60v is 15v per SLA battery.


It's a bit high for starter batteries or in standby use, but deep-cycle batteries are often spec'd for 15v cycle use at 20'C, bit less if it's hotter.

Random first thing I googled for example.


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## rishimaze (May 23, 2021)

MattsAwesomeStuff said:


> No, by ghetto I mean prioritized for low cost and scroungeability above safety, reliability, effectiveness, etc.


:/ to each their own I suppose!
Id have to stridently disagree with all of these! 

1. Cost: does $600 for a 4000 watt charger seem low cost to you? That's about what the 8 SE-600 PSU's cost me over time for the super charger. I agree that Lenovo PSU's since they are old/used stock are now inexpensive, but they aren't when they were new. Expect to pay over $100 for a new one!
2. Scroungable: Lenovo PSU's...highly! Meanwell PSU's...good luck scrounging them! They just don't EVER get replaced!
3. Safety: All the PSU's I talk about are overload and temperature protected. They have isolated DC outputs good for 1000v. That's pretty safe! 
4. Reliability: The PSU's I use, They reliably make their set voltage year after year. I've had the displeasure of having at least 5 chargers die on their own. A Lenovo or Meanwell PSU will probably still be working in 20 years while a typical charger will not.
5. Effectiveness: VERY EFFECTIVE at charging...LOL! I've been using them like this since 2015 without a hitch and in that same time frame, seen 5 chargers die.

Using your definition of "ghetto" definitely does not apply.


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## ebug (Mar 8, 2014)

Awesome info, thanks a lot !


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## john61ct (Feb 25, 2017)

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


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## john61ct (Feb 25, 2017)

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


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## rishimaze (May 23, 2021)

john61ct said:


> 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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## rishimaze (May 23, 2021)

john61ct said:


> 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:
> 
> ...


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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## rishimaze (May 23, 2021)

john61ct said:


> 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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## john61ct (Feb 25, 2017)

rishimaze said:


> 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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## rishimaze (May 23, 2021)

john61ct said:


> 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.
> 
> ...


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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## john61ct (Feb 25, 2017)

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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## rishimaze (May 23, 2021)

john61ct said:


> 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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## rishimaze (May 23, 2021)

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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## john61ct (Feb 25, 2017)

rishimaze said:


> 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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## rishimaze (May 23, 2021)

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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## rishimaze (May 23, 2021)

john61ct said:


> 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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## rishimaze (May 23, 2021)

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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## rishimaze (May 23, 2021)

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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## hallkbrdz (Jan 2, 2018)

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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## rishimaze (May 23, 2021)

hallkbrdz said:


> 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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## rishimaze (May 23, 2021)

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).






AP4310 pdf, AP4310 Description, AP4310 Datasheet, AP4310 view ::: ALLDATASHEET :::


AP4310 Datasheet, AP4310 datasheets, AP4310 pdf, AP4310 integrated circuits : BCDSEMI - DUAL OP AMP AND VOLTAGE REFERENCE ,alldatasheet, Datasheet, Datasheet search site for Electronic Components and Semiconductors, integrated circuits, diodes, triacs and other semiconductors.



pdf1.alldatasheet.com






















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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## rishimaze (May 23, 2021)

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.









180.0US $ 10% OFF|Intelligent 72v 15a 20a 25a 30a Charger For72v 20s Li-ion - AliExpress


Smarter Shopping, Better Living! Aliexpress.com




www.aliexpress.com





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!









Shenzhen UNIS Technology Co., Ltd. - Li-ion battery, Battery charger


Shenzhen UNIS Technology Co., Ltd., Experts in Manufacturing and Exporting Li-ion battery, Battery charger and 0 more Products.




unistechnology.en.alibaba.com





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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## rishimaze (May 23, 2021)

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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## john61ct (Feb 25, 2017)

Try this guy on eBay

seller:barbjb


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## rishimaze (May 23, 2021)

john61ct said:


> 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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## rishimaze (May 23, 2021)

A friend recently suggested I look into public charging via J1772. I've been looking at solutions and I can implement this on any of my EV's as I get around to it. For now the Zap is the only one I care about getting set up for public charging. I bought a 220v charger for it, but the seller/factory has refused to fix their mistakes in its firmware so that's getting benched until I can hack the PIC micro controller. It's too large to fit on the Zap...so its not going on there no matter what. I have a 12 amp charger that is easy to waterproof and runs on 220v. I'm getting that worked out for permanent mounting on the Zap. It's not as good as 30 amps, but it will do the job for now. I'm thinking I want an onboard breaker into the charging port. I want to arrest any back feeding into the charger from the pack when I'm not charging. I want to mount a J1772 and 220v plug inside the seat compartment. I want to add a watt meter too. This will let me use either option for powering the onboard charger and see how much capacity I put into the pack.

I'll need to get one of these. They are sold from all sorts of places and not just EV West. You don't have to pay $45 for one if you look around. This box communicates with the J1772 charging station to negotiate charging. Without it, the charging station home or public won't apply 220v to the EV.





__





J1772 Active Vehicle Control Module AVC2 - For Public Charge Stations, EV West - Electric Vehicle Parts, Components, EVSE Charging Stations, Electric Car Conversion Kits






www.evwest.com





I bought a J1772 charger for use at home. It was sold as used and I got it for $115 including shipping. I can see that the screw holes used for hanging it on the wall show minor wear from screws. Otherwise this thing looks absolutely brand new! There is no dust or wear on it. Usually chords from sliding on concrete show scuffs on them. Usually the plug from connecting to a car over and over again show signs of wear. Its like this charger never saw use or maybe got used once or twice. From every way I can look at it, it's virtually brand new. When it arrived to me, it was all in its factory packaging. It was clear the packing tape had been reapplied on the outer box, but that was all. I was thinking it was a 30 amp unit, but it's 20 amps. Oh well, I'm not charging a car with it. This will hardly matter for my scooters. It's not smart and doesn't use an app or track current usage. I really didn't want to pay $800+ for a smart J1772 charger anyway. This unit will let me test public charging at home before I need it on a longer ride.


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