Building your own power supply for testing

[bobmcree]

To properly assemble and test the bms i designed for lithium iron phosphate cells it is necessary to have a power supply adjustable to 3.65v or whatever value is desired for the shunts, and 12v or so to test the current regulation section of the LifeCycle BMS. There are of course many other reasons an adjustable supply is worth having.

A simple diagram for a DC regulator circuit using the LM317 is included in the assembly / test instructions, but it is intended to be powered by several cells of the battery pack for people who do not have access to a variable supply. I have some suitable transformers to make it a 0-20V 2A supply by adding a bridge rectifier and filter capacitor. These transformers were made for the Coleco Adam personal computer that never made it, and i have about 100 out of the 500 i originally bought. I am putting together a kit for a 0-20V 2A supply powered by 110vac for $29 including shipping to the US. for $10 more i will include a 3 1/2 digit lcd display accurate to 1 digit. This kit will include all the components and the ac line cord but no case.

i need to find out if enough people want these to make it worth making a pc board. if you want one, send me $1 as a down payment towards $29 or $39 with lcd dispay, including $9 flat rate shipping for the ac powered kit, and if i get 10 people i will build them. otherwise if we cannot get 10 users i will refund the money.

i will give it a week to decide if enough people want them. if you do send a $1 refundable deposit to bobmcree@wildblue.net and you will get a chance to buy the supply or a refund.

 

[Ypedal]

Does this offer extend to Canadians ? !

If so.. i'm in ! ( I understand shipping will cost more.. that's not a problem as long as you ship USPS and not UPS )

 

[bobmcree]

$9 of the price is shipping so if it is more than that you can pay the difference

 

[Ypedal]

Awsome.. 8) -- will gladly pay the difference.

UPS with their mandatory brokerage 20 $ fee on every parcel ( over the shipping cost ), vs usps more reasonable 5 $ ( handling fee as it's called ) only on the boxes they check wich is 50/50 .. half the time i don't have to pay duties or brokerage at the postal outlet.

9 to go !

 

[bobmcree]

Awsome.. 8) -- will gladly pay the difference.

UPS with their mandatory brokerage 20 $ fee on every parcel ( over the shipping cost ), vs usps more reasonable 5 $ ( handling fee as it's called ) only on the boxes they check wich is 50/50 .. half the time i don't have to pay duties or brokerage at the postal outlet.

9 to go !

i always ship usps unless desired otherwise. if you want just the transformers i will let them go for $10 plus shipping they weigh over 3 lbs. i am hoping i can get deposits from 10 guys so it will be worth it to do a pcb otherwise it is not many parts to solder together.

 

[Joey]

Hi Bob,

Count me in. I just sent $1 via PayPal toward power supply with 3 1/2 digit LCD display.

RJF (Joey)

 

[Ypedal]

Heck.. if 8 more show up .. i' ll take 2 !

If nothing else.. a learning project, or a primer to the CMS/VMS.

A few years ago i would have walked away from something like this for fear of failure.. but with every new project comes more confidence .. with every screw up a lessson learned lol...

Example : I blew up a TP ballancer this weekend ( Sorry Gary.. i read the instructions a few times but still managed to mix up " Bank " with " Group " .. ) , Until recently, i would have chucked it and purchased a new one.. but i opened it up for the heck of it.. found a big black nasty spot on the board with 3 obviously burned out copper traces.. from reading on this forum ( Fechter i beleive suggested this at some point ) scrapped the green off the copper and using a few strands from a 12 gauge wire twisted together, connected the traces and , BAM.. works again.

Alright. damit. i'm rambling again.

 

[bobmcree]

Hi Bob,

Count me in. I just sent $1 via PayPal toward power supply with 3 1/2 digit LCD display.

RJF (Joey)

i am putting together a parts order. even if we only get 5 people i will still do it.

bob

 

[bobmcree]

Hi Bob,

Count me in. I just sent $1 via PayPal toward power supply with 3 1/2 digit LCD display.

RJF (Joey)

i am putting together a parts order. even if we only get 5 people i will still do it. btw check out mpja for your panel meters and other surplus needs.

bob

 

[slayer]

ok Bob just sent my dollar for one with the lcd display please

Guy

 

[vanilla ice]

I prefer with the display also!

 

[bobmcree]

ok, i have enough people committed that i will put together at least 15 kits. here is a description of what you will get:

1) multiple output transformer with one winding to power the 9v meter and others that can provide 0-20v @ 2A.

2) two full wave bridge diodes, one for the meter power and one for the output power

3) filter caps for the 9v and 20v outputs

4) LM317 to permit up to 2A output from 0-20v, with required resistors, and a pot to adjust the voltage output.

***3/15 A PCB IS NOW INCLUDED FOR THE LM317 CIRCUIT.*****

5) LCD 3 1/2 digit panel meter accurate to 1%, including appropriate scaling resistors for 0-20v display

6) separate regulator to provide 9v to the meter. i am not positive of the best way yet but it will be a couple of resistors and a 3 terminal regulator. the other option is to power the meter from a 9v battery for about 6 months but i am providing the parts to do without the battery.

7) ac line cord, fuse holder, and ac fuse. i am not providing a pilot light but of course you can add that. i am also not providing a case. I will try to have some cases available soon with a cutout for the lcd meter and outputs for an extra $10 plus shipping if that is desired.

i think this covers it all, please let me know if there is something i missed. i intend to provide a piece of perfboard and detailed instructions for assembly. if i can get 25 orders i will make a pcb, but the circuit is very simple and putting it together on a perfboard is fairly simple. if i do make the pc boards they will be included in the $29 basic kit and the $39 kit which includes the 3 1/2 digit meter. So far i have the 10 orders that was my cutoff to do the project.

i am looking at the possibility of providing a switch that permits the meter to select between voltage and output current display. i think i will be able to offer this as an additional $5 option.

for those who have made deposit thank you. if you want to send me a check for the balance that will avoid paypal fees, but i will absorb the paypal cut if you want to pay the balance that way. i will let you all know individually when i am ready to ship, so you can pay the balance before that or after.

the kits will be shipped in the order of receipt of the orders and deposit. hopefully i can get them all out by 3/21. I will get a batch of parts together and take a photo so you can see what you are getting before paying more than the $1 deposit.

 

[disadvantage]

Count me in, for the deluxe kit. I just paypal'ed a buck to you at bobmcree@wildblue.net

Would it be too costly to add a second LM317T and another pot, for adjustable current limit?

If you can't add this feature, that's okay. I could probably figure it out myself.

It would extend the usefulness of the kit for me; sort of making it a mini lab power supply.

I might like to get a second LCD for output current display.

I don't mean to patronize, but thanks for putting this all together for us at ES.

disadvantage

 

[bobmcree]

Count me in, for the deluxe kit. I just paypal'ed a buck to you at bobmcree@wildblue.net

Would it be too costly to add a second LM317T and another pot, for adjustable current limit?

If you can't add this feature, that's okay. I could probably figure it out myself.

It would extend the usefulness of the kit for me; sort of making it a mini lab power supply.

I might like to get a second LCD for output current display.

I don't mean to patronize, but thanks for putting this all together for us at ES.

disadvantage

i'm glad to do it, my wife has been hassling me for years for carrying around all these transformers. they weigh about 3.5 lbs and have 4 output windings, two low current windings supply 10v and 15v, and the two high current windings are 10V and 16V, so the two high current windings in series and a bridge rectifier will provide a regulated output up to 24v dc and at 1.5A continuous 2A max.

the inexpensive lcd display, like many others, requires a separate isolated power source, often provided by a 9v battery. i am including a separate rectifier and components to power the meter from the 10v low current winding to avoid the need for a battery.

i will think about the current limiting and see if i can do it without adding too much extra cost. I was figuring on the single LM317, bridge, and caps could go on a perfboard but if we add current limiting it probably will need to be a pc board and that will add at least $10 to the cost.

This originally started out as something just for testing the bms kit, and it could easily grow into something too expensive, so i want to be careful of that. If I can add current limiting and not make it too much more expensive or difficult i will do it. There would not be the need for a second meter, just a switch to select voltage or current.

I will provide values that will let the supply go up to 24v, but the meter will only go to 19.99 unless you want to switch it to read 199.9 max. the meter basic function is 200 mv so making it read current is fairly simple.

i found some pc boards for the LM317 circuit so assembly will be fairly easy. the pcb does not have current limiting so if we add that it will be a separate module. i don't want to make it too complicated, so the current limiting inherent in the LM317 may have to do for the basic version, and if enough people want it we can come up with another module to add that function.

i should be able to start shipping the kits by the end of next week.

 

[bobmcree]

POWER SUPPLY UPDATE 3/17/08 - I now have enough orders that i am putting together the first 15 kits. About 5 people have paid $29 or $39 with meter (both including priority mail shipping) for the kits and 5 more have given me $1deposits, so i have the parts on order and should be able to ship the kits starting 3/24. I was not able to get the LCD i originally ordered so i got one that is a couple of bucks more but i will still keep the price the same $10 extra even though my cost is about $11 with shipping. the new meters are larger and have the resistors in them for 20v or 200v so if you want to put in a switch you can go above 19.99v and still have the meter work by switching ranges to read up to 199.9v.

MPJA is a great source for this kind of thing, the meter i am using is this one http://www.mpja.com/prodinfo.asp?number=12305+ME

the meter has huge .8" digits, for those older eyes. MPJA.com is a great place to know about. definitely ask for a catalog.

Anyone who has ordered a kit without the meter can certainly add it for another $10. I will post a photo of the pc board and other parts later this week when they come in. The kit will include everything needed to build a 0-24v 1.5A supply except the case. If I sell out the first 15 kits i have plenty more transformers.

 

[chessir]

bob,

Count me in. I just sent $1 via PayPal toward power supply with 3 1/2 digit LCD display.

 

[bobmcree]

OK guys, the meters are in and i will start shipping the kits on monday to the people who have paid in full, then to the rest as the balance of the price of the $29 or $39 is received. I am very happy with the LCD meters, they are easily accurate to .5% and are very crisp and big enough for tired eyes (not old, just tired). There is no reason you cannot use the meter to measure battery voltage on the bike if you do not have a drainbrain or cycleanalyst. The meter has .2,2,20.200v full scale, so i set them to read to 19.99v even though the supply will go up to 24. It is a simple matter to add a switch to change the meter scale.

The LM317 will adjust from 1.2v to 37v, but the transformer will only provide about 25v, which is sufficient for most testing purposes. The output current is limited to 1.5A continuous so you can hook up a controller and give it a bit of throttle and it will run with the wheel off the ground, or it will not work, but smoke will not be as likely to come pouring out, as it sometimes does when testing with the full battery current.

I got some nice little pcb's for the regulator and associated components. and the kit includes the LM317 with mounting hardware and this pcb, a power switch, fuse and holder, pot, knob, diode bridges for the 9v and main power, power transformer, instrument cord and receptacle, LCD 3-1/2 digit .5% meter, 9v regulator, lm317, a pair of red/black 5-way binding posts, and all the necessary resistors and caps, and . It does NOT include a case or screws to mount the circuit board and other parts into your case. A photo is attached, i have about 15 orders now, with 3 paid that will go out first, ahd i will ship the rest in the order i receive payment. Please make sure you have the right shipping address on your paypal payment, or you can send me a check.

some of you know this started as just an assembly tool so people could calibrate my new bms, but i have received so much positive feedback i see it was a need that was not fulfilled. The cheapest equivalent variable supply would be about $100, so i am pleased i can offer this kit to my friends.

btw if i sell 20 kits my profit will be $100. If i could have squeezed that much profit out of the batteries i tried to sell i might still be doing it. this project is more a "labor of love" and an opportunity to share the opportunities i found to get good prices on the parts. Here is a photo of the meter, pcb, and heat sink:

 

[disadvantage]

Splendid!

I was hoping to use this power supply to test motor controllers, after using it to calibrate my new BMS.

Glad you thought of this alternate use also.

disadvantage

 

[Ypedal]

Excellent !!!

This will come in handy when i decide to retro-fit my eZee motor with a Clyte controller ! ( Unless someone here already knows the right color combo ? !! )

 

[bobmcree]

Excellent !!!

This will come in handy when i decide to retro-fit my eZee motor with a Clyte controller ! ( Unless someone here already knows the right color combo ? !! )

i have an ezee and instructions on how to disable the low voltage cutoff. do you think it needs a more powerful controller than the stock one, or is it just the low voltage that is your problem?

 

[Ypedal]

The plan is to re-lace the hub in a 20" rim .. and then UP the voltage ! ( to make up the speed difference )

20 amps is enough on the eZee motor, but i could be tempted to try more and see what happens !

what is the default lvc on the stock controller ?

 

[bobmcree]

what is the default lvc on the stock controller ?

i believe it is 31v because of the li ion battery standard in the kit. there is also a high voltage cutoff, i think 45v. i have the document from justin i will dig it up and send it to you. you have to dig the controller out of the potting to change it and that probably voids the warranty. he is having the low voltage cutoff dropped to 29v on the next batch and raising the high limit to permit 48v operation. i don't want to burn it out, but it would be fun to see what it can do at higher voltage.

 

[bobmcree]

i have the first batch of 15 power supplies sorted out and will be ready to ship them on monday. those who have paid $29 or $39 with the meter will have theirs shipped out by priority mail on monday, those who have made a deposit can pay the balance by paypal or send me a check.

the kit includses the power transformer with multiple secondaries that can provide 2A continuous at >24v and has windings that can be used to provide 2 additional isolated voltages, one of these windings is used to generate 9v to power the meter and the power on led. the pcb provides convenient connection to the LM317 and the 5k pot and resistors provided will permit adjusting from about 1.2v-24v with current limited to 1.5A. The LCD 3-1/2 digit meter can be configured to read 200 mv 2v 20v or 200v, and could be used to display current by adding a switch and resistor. (to220 mounting hardware for the LM317 is included)

This supply started out as a tool to adjust the bms, but it seems there is enough demand that it seemed like a good idea to offer them to anybody who wants them. profit margin is very slim so don't expect me to hold your hand while you build it.

 

[Ypedal]

Looks good !

Edit : ps: .. Thank you.

 

[bobmcree]

i will be shipping out the first batch of the power supply kits tomorrow. a few things have come up as i write the manual that make the system even more verstatile and wonderful than i had first anticipated...

the transformer is capable of providing well over the 1.5A limit of the LM317, so there is even room for expansion. There are 4 independent isolated secondaries, 2 high current and 2 low current. the two high current windings can be connected in series or used separately. and depending on how the connection is made to the provided full wave bridge rectifier, the secondary voltage at 1.5A can be about 10,20. or 30v. If the user wanted to add a second LM317 or 723 to generate a second voltage or provide current regulation,there are lots of possibilities,

with the two high current secondaries in series, the supply can provide close to 37v at low current, and about 32V@1.5A with the supplied LM317 and heat sink. This is just right for troubleshooting a typical ebike controller without causing disastrous damage if things are not quite connected properly. if lower DC voltages are desired it would be best to choose the transformer tap that results in the least amount of power to be wasted as heat. The LCD meter has the necessary gain adjustment resistors attached, so to provide a meter function that switches between 20v fs and 200v fs a simple dpdt switch could be attached. the meter has a 200mv scale as well that could be used with a shunt to measure current.

i will try to get a complete description of the kit up on my website tonight. check out bobmcree.com later this evening. right now there are some chili rellenos with my name on them that are calling....