Simple low current LiPo charger

[Jeremy Harris]

I'm putting together a small LiPo pack for a non-technically minded person, so was looking for a plug-in-and-go charging solution, one that didn't involve pressing buttons or looking at displays. The pack is a modest 7S one, and there isn't a need for fast charging, 10 to 12 hours would be fine, as it could be charged overnight. As others have found, there isn't an easy solution to this particular conundrum. Add in that I didn't want to spend more than the equivalent of around $50 on it, or weeks of time building something that was custom made, and the problem gets even harder.

HK sell these little balance chargers: http://www.hobbycity.com/hobbyking/stor ... oduct=7637 that will deliver around 0.8A, need no button pressing or whatever and which are dirt cheap at $4.49 each. They only charge up to 3S though and still need a 12V power supply.

A quick hunt around on ebay found some small 12V 1A isolated power supplies from this ebay seller: http://myworld.ebay.co.uk/bestvaluezone/ for just under $7 each, including shipping.

The plan is to fit three power supplies and three of the small chargers (minus their cases) in a small box, with an 8 way cable and connector that plugs in to the battery pack to charge the individual cells via the balance taps. The chargers will be hooked up with their top outputs in series, which should work fine with the isolated inputs. The charge current is nice and low , so the balance leads will take it just fine, and the chargers have a couple of LEDs on that I can extend out to the case. Charging should be as simple as plug it in, switch on the power and wait for the "charged" indication on all three LEDs. Pretty foolproof.

With three supplies and three chargers this unit will charge from 1S to 9S. Add more and you can build as big a balance charger as you need. The only things to watch is that the outputs are kept in the right sequence and that the charger outputs are kept isolated. This latter point needs checking carefully, as the negative output track can *just* touch the case clip - easily fixed by adding a sliver of tape and a little bit of bending of the case tab.

I'll post pictures of the finished unit, but here is a shot of one of these tiny power supplies and a charger:

3S charger and PSU.JPG (198.15 KiB) Viewed 1310 times

One thing that may be of interest is that these power supplies have a rated input voltage range of 86V to 230V +/-20%. They may well work OK on a DC input from as low as 70V or so. Might be handy for anyone looking for a cheap 1A, 12V DC DC converter. I'm reasonably sure one of these would make a 12V supply for the "simple BLDC controller" for anyone running at 70V or more.

Jeremy

[El_Steak]

I like the plug and play approach.

Another way of achieving something similar would be with 7 x single cell chargers.

For example, you can get 7 of these 4.2V / 1A chargers for 5.95$ each, free shipping:

http://www.dealextreme.com/details.dx/sku.5837

The advantage is that they each have their own AC Power supply. Also being single cell chargers, there is no balancing algorithm to go wrong.

You could take the plastic casing and AC cords out and rewire all AC inputs to a single cord. For the outputs, just make your own 8 pins connector that regroups the outputs of the 7 chargers and matches what you have on your 7s pack.

I think YPedal did something similar with 2A chargers for Lifepo4 cells.

*EDIT*: Found out there's already a great thread on this subject here:

viewtopic.php?f=14&t=2586&start=0&hilit=single+cell+charger

Some nasty setups with daisy-chained powerbars covered with wall warts in there

[Jeremy Harris]

Thanks for that. Had I spotted those I'd have probably gone for them instead.

The only snag I've found with Dealextreme is that stuff takes forever to arrive. I bought some LEDs from them around the end of November, they finally turned up about a week ago.

I remember the single cell charger thread, but only now you've reminded me of it! I dod look at getting a bunch of Voltphreak chargers a long time ago, but decided to mod a Meanwell power supply instead (and innocently start a thread on modding it, which seems to have run for years now).

Jeremy

[El_Steak]

The only snag I've found with Dealextreme is that stuff takes forever to arrive. I bought some LEDs from them around the end of November, they finally turned up about a week ago.

Agreed, shipping is hit and miss with DealExtreme. Stuff can take anywhere from 2 weeks to 2 months to get here. I'm still waiting on some ipod cases I ordered at the end of November.

[neptronix]

Deal extreme is a huge pain in the butt.

Have you really ruled out the hobby chargers? I mean, for my small 5ah pack i basically just plug my pack into the charger and hit 'start'. It beeps when it's done. How much more simple does it need?

[Jeremy Harris]

Deal extreme is a huge pain in the butt.

Have you really ruled out the hobby chargers? I mean, for my small 5ah pack i basically just plug my pack into the charger and hit 'start'. It beeps when it's done. How much more simple does it need?

More or less. A hobby charger set up would most probably need two boxes, the charger and a PSU, there's a distinct possibility that the user (an elderly lady technophobe) might be a bit daunted by this and the display etc, plus there's always the chance that the charger programming might be unwittingly altered. The user is around 70 miles away from me, so I want something that's as foolproof and easy to use as I can make it.

It'd be really good if nice and simple LiPo chargers were readily available, ones with nothing more than a plug that goes to the battery pack and an indicator for full charge.

Jeremy

[liveforphysics]

Wanted to post the link to the 12v 1a supplies as the first link didn't find the product for me.


http://cgi.ebay.co.uk/DC-12V-1A-Regulat ... 056wt_1139

[spinningmagnets]

1.5A charger, 22.2V only, $37...I have never tried this unit, its just on my list of options. Since its only 6S, it doesn't look like it will help your situation...

http://www.batteryspace.com/smartcharger15afor222vli-ionpolymerrechargeablebatterypack.aspx

[liveforphysics]

The beauty of Jeremy's method over a charger like that battery space unit is as follows:

1. It balance charges.
2. If a cell dies, it can't over charge the pack.
3. No matter how out of balance a pack gets, it can correct it, even if you have a cell at 100% SOC and another cell at 0% SOC.
4. It can be safely left unattended during charging.
5. It would take an fantastic idiot to botch the charging process, which consists of plugging a cord into the wall, and plugging the pack in (or any order of the same 2 steps).

[texaspyro]

5. It would take an fantastic idiot to botch the charging process, which consists of plugging a cord into the wall, and plugging the pack in (or any order of the same 2 steps).

Believe me, they abound in vast, Vast, VAST quantities...

[el_walto]

I bought 5 of those turnigy chargers to charge my 15S 5Ah battery pack. My plan was to run them all off one Toshiba laptop power supply(since i got lots of these 15v 6A supplies). Then someone told me i can't run all the chargers off one power supply.

Why does this work(because i tested it and it does work):
12V SLA > 5 Chargers > 5batteries

Why will this blow up my chargers:
12V Laptop adapter > 5Chargers > 5batteries

If those two things are true, will this blow up my chargers?
12V Laptop adapter > 12V SLA > 5 Chargers > 5batteries

[Pasadena]

viewtopic.php?f=2&t=24540

I bought 5 of those turnigy chargers to charge my 15S 5Ah battery pack. My plan was to run them all off one Toshiba laptop power supply(since i got lots of these 15v 6A supplies). Then someone told me i can't run all the chargers off one power supply.

Why does this work(because i tested it and it does work):
12V SLA > 5 Chargers > 5batteries

Why will this blow up my chargers:
12V Laptop adapter > 5Chargers > 5batteries

If those two things are true, will this blow up my chargers?
12V Laptop adapter > 12V SLA > 5 Chargers > 5batteries

[Jeremy Harris]

I bought 5 of those turnigy chargers to charge my 15S 5Ah battery pack. My plan was to run them all off one Toshiba laptop power supply(since i got lots of these 15v 6A supplies). Then someone told me i can't run all the chargers off one power supply.

Why does this work(because i tested it and it does work):
12V SLA > 5 Chargers > 5batteries

Why will this blow up my chargers:
12V Laptop adapter > 5Chargers > 5batteries

If those two things are true, will this blow up my chargers?
12V Laptop adapter > 12V SLA > 5 Chargers > 5batteries

The answer is as has already been linked by Pasadena, you need to drive the chargers from isolated supplies. You only need small power supplies for these baby chargers, as they draw just less than an amp from 12V, hence my choice of mini isolated 12V supplies (but do check the circuit board mount adjacent to the LED, as in some of mine the case was touching the 0V output track).

It's easy to whip the cover and circuit board out of these small power supplies and either mount them directly in a box or fix the potential case to 0V short with a bit of tape and a judicious squeeze on the alloy case mounting tab to give extra clearance. Once modded like this they are completely isolated.

Jeremy

[NeilP]

Hi John

just posting here now on a remote computer...cant e-mail or book mark ...and I'll forget to come back to this thread to have aread unless I mark it in some way...at least now it will appear under the My Posts section of my control panel.

I need a slow overnight charger..int

[cwah]

That's a nice and cheap idea for safe bulk charging!

Would that work if I get 8 of them to bulk charge a 24s pack, but with the connection in series still plugged in?
And use a single 12V 150W power supply on all the balance charger (via parallel connection)?

That would be a cheap, safe and plug and play power supply+charger combo I can use it to charge my pack overnight?

[Jeremy Harris]

That's a nice and cheap idea for safe bulk charging!

Would that work if I get 8 of them to bulk charge a 24s pack, but with the connection in series still plugged in?
And use a single 12V 150W power supply on all the balance charger (via parallel connection)?

That would be a cheap, safe and plug and play power supply+charger combo I can use it to charge my pack overnight?

Unfortunately that wouldn't work, as each one of these chargers needs an independent, isolated, 12 V supply, so that the outputs can be fed to a series connected pack. It's why I ended up using three 12 V supplies to run three of these chargers.

If you wanted to charge a 24S pack, then you'd need 8 of these chargers and also 8 isolated 12 V power supplies to run them.

[cwah]

Thanks Jeremy for this nice explaination. With 8 different power supply I think I better forget it lol.

Having a cheap "charge and forget overnight" lipo solution is so hard to get. Haven't found the perfect solution yet

[Jeremy Harris]

Thanks Jeremy for this nice explaination. With 8 different power supply I think I better forget it lol.

Having a cheap "charge and forget overnight" lipo solution is so hard to get. Haven't found the perfect solution yet

The tiny 12V power supplies I used were pretty cheap, around £3.50 each, inc delivery. They are also pretty small, around 30mm x 40mm by 70mm. It was no problem to mount then in a plastic box, with their main supply inputs connected in parallel and their outputs each feeding a separate charger. Here's a link to the same type of supply: http://www.ebay.co.uk/itm/12V-1A-12W-DC ... 27c6666de1

[deVries]

Thanks Jeremy for this nice explaination. With 8 different power supply I think I better forget it lol.

Having a cheap "charge and forget overnight" lipo solution is so hard to get. Haven't found the perfect solution yet

The tiny 12V power supplies I used were pretty cheap, around £3.50 each, inc delivery. They are also pretty small, around 30mm x 40mm by 70mm. It was no problem to mount then in a plastic box, with their main supply inputs connected in parallel and their outputs each feeding a separate charger. Here's a link to the same type of supply: http://www.ebay.co.uk/itm/12V-1A-12W-DC ... 27c6666de1

Cwah, this is a very low-cost & safe way to slow charge your 24s lipo. You won't bulk charge using the 2 MW & 2 Hyperion you have already, crazy that you won't, so go for this solution instead. Jeremy has used this for a long period of time, so it is a safe low cost way to charge slow.

Otherwise, just wait for your BMSBattery bulk chargers, or try some King Pans too.

BUT bulk charging at such high voltages won't be nearly as safe as Jeremy's solution that's low cost too.

HK sell these little balance chargers: http://www.hobbycity.com/hobbyking/stor ... oduct=7637 that will deliver around 0.8A, need no button pressing or whatever and which are dirt cheap at $4.49 each. They only charge up to 3S though and still need a 12V power supply.

[Jeremy Harris]

The only thing I'd add is that it makes sense to fit a fan if you decide to put them in a box, as I did. I found that the inside of the box got a bit warm after an hour or two. A cheap 12V fan fitted at one end, with some holes drilled in the other end fixed the problem and it now runs cool.

It charges at a bit less than 1A in practice, so will charge a 50% drained 10 Ah pack in about 5 to 6 hours, but is pretty safe to leave on overnight. The person it was for wouldn't have been able to cope with making lots of connections and working through menus on a typical RC charger. I fitted a single multiway charge connector to the battery box, connected to the balance ports of internal battery packs, and a multicore cable to the charger with a matching connector on the end, so all the user has to do is plug it in and turn on the mains. Once charged all the green lights go out as an indicator, making it pretty foolproof.

[cwah]

The tiny 12V power supplies I used were pretty cheap, around £3.50 each, inc delivery. They are also pretty small, around 30mm x 40mm by 70mm. It was no problem to mount then in a plastic box, with their main supply inputs connected in parallel and their outputs each feeding a separate charger. Here's a link to the same type of supply: http://www.ebay.co.uk/itm/12V-1A-12W-DC ... 27c6666de1

Thanks Jeremy. So that's finally maybe possible to bulk balance charge my 24s made of 4s packs?

On the charger side:
- I get 8 mini power supply as you mentionned: (http://www.ebay.co.uk/itm/12V-1A-12W-DC ... 27c6666de1)
- They will be connected via a main power cable I'll strip and put the wires in parallel to the power supply (http://www.ebay.co.uk/itm/NEW-HIGH-QUAL ... 2a1eebd296)
- These 8 power supply will be used to charge 8 other 2-3s turnigy charger (http://www.hobbyking.com/hobbyking/stor ... 2S_3S.html)
- These power supply will have 8*3s extensions connected to them (http://www.hobbyking.com/hobbyking/stor ... _bag_.html)
- These 8*3s extensions will be all connected to a DB37 connectors male (http://www.ebay.co.uk/itm/D-SUB-37-Pin- ... 19d3c6eeeb)

On the battery side:
- My 6*4s pack will each have a 4s extension (http://www.hobbyking.com/hobbyking/stor ... _bag_.html)
- These extensions will be connected to a DB37 connector female (http://www.ebay.co.uk/itm/D-SUB-37-Pin- ... 1c29c40851)

So I can leave the charger always connected to the main power at home, and when I come back from work, I can just plug the 2 DB37 connectors togethers and go to bed.

Seems like a much safer plan and small enough to be carried anywhere!


ps for devries: I have 2 meanwell and 2 hyperions but they are simply not plug and charge. I want something I can plug (one time) and go to bed. Hyperion are too noisy, you have to plug battery wires and balance wires, you have to provide setting to each hyperion, and it's also bulky. 2 meanwells and 2 hyperions are quite massive, and you can't bring it with you when necessary. Alternative is required

[Jeremy Harris]

Yes, that would work OK, as long as you take care with the wiring.

It's pretty safe, as the charge current is low and the wire gauge is thin enough to fuse if something goes wrong, but I personally wouldn't be at all happy about overnight charging unless you have somewhere fire proof to charge. I had a battery fire when I used to charge indoors, I was woken at around 4am by a loud bang coming from my study. I got up to investigate and was just in time to be able pick up a burning battery pack by the leads and chuck it outside, where the cells exploded one by one in a fairly fierce fireball. Never again will I charge indoors while I'm asleep!

[cwah]

Thanks Jeremy!

I also found this balance charger:
http://www.ebay.com/itm/Titan-B3-Balanc ... 4576wt_922

The power supply is integrated with the charger, and the whole is even charger. Probably worth a try!

How did your lipo happened to be on fire?

[Jeremy Harris]

Thanks Jeremy!

I also found this balance charger:
http://www.ebay.com/itm/Titan-B3-Balanc ... 4576wt_922

The power supply is integrated with the charger, and the whole is even charger. Probably worth a try!

How did your lipo happened to be on fire?

Funny thing, but I just found exactly the same unit a few minutes ago!

Looks OK to me, and saves needing the extra power supplies. Cheap enough, too.

The fire I had wasn't LiPo, it was around four years or so ago and was a NiMH pack I built, using lots of RC type NiMH packs (before we really started using LiPo on ebikes). I'd left the pack on a very low charge overnight, thinking it would be safe, but I was wrong. The thread is here: viewtopic.php?f=14&t=3241&p=47328#p47328

[cwah]

Thanks Jeremy.

It appears that no battery are safe finally! From the NimH to the lipo's. I have to think of an area to charge my pack without too much damage in case of fire, even if it's a minor possibility.