UK mains (240V) and Luna Advanced charger: can it work?

[pickworthi]

I have a UK street legal (250W nominal) pedalec, and 36V (10s) batteries for it. I'm planning on building two bespoke 10s batteries, and want to find a charger that allows me to control the charge current and final voltage. From all I read, I can prolong the pack life by charging at less than 1C, and to 80% capacity (with occasional 100% charges to balance the cells).

This advanced charger from LunaCycle appears to be just what I need: https://lunacycle.com/luna-charger-36v-advanced-210w-ebike-charger/

But... in it's listing it specifically states: "110v AC input for North America".
The picture of the charger on their web site shows "AC Input: 110/220 VAC -- F6A".

So I wrote to Luna asking if the charger could work in the UK on the 240V mains supply. They replied: "Unfortunately unless expressly stated on the listing our chargers only work with 120V outlets."

I've tried various combinations of Internet search phrases, but I cannot find an equivalent to this model that is sold outside the USA and rated for UK mains voltage. I really don't want to fall back on the only chargers I can find, which are the enclosed fixed Volt, fixed amp variety. I'm looking for more control over the charging process, but not so much control as the Charge Satiator provides, and I will be wanting two chargers.

My first question is to any UK member that has used a charger similar to the Luna model - basically does it work on the UK mains, or is there an alternative that can be sourced from the UK that will do the same job?

My second question is whether using a step down transformer (like this one https://www.amazon.co.uk/dp/B00H404YOC/?coliid=I3LKFPVEMAXAF0&colid=2WBPAIA5VDOW6&psc=1&ref_=lv_ov_lig_dp_it ) would work. I know these things are quite common on building sites where the trades need to use tools that they get from the USA. So I'm thinking that if I plug two Luna chargers into it, they will feel right at home. However - I've been wrong before!

Any thoughts on this appreciated.
Thanks
Ian

 

[Hillhater]

Sorry i cannot help with the Luna charger other than to say there are threads on here very critical of that company !
But, A budget option for multiple charge voltages , with user set voltage ( 24-90v), current (0_10A), capacity monitoring , etc and variable input voltage,...is the MPT 7210A ..600W capacity and available for <$40 !
https://www.wish.com/product/lcd-displa ... =mobileweb
https://endless-sphere.com/forums/viewtopic.php?f=14&t=88930&p=1522940&hilit=Mpt+7210a#p1522940

NOTE:.. it needs a separate DC power supply ..server PSU or Meanwell etc,....but they are cheap !
Or, if you are handy with a soldering iron etc, you could do your own..
https://endless-sphere.com/forums/viewtopic.php?f=14&t=63230

 

[pickworthi]

Many thanks for the response, and that takes me down a route I wasn't expecting!

If you don't mind, I have a few questions (because I know 0% about solar things):
- I can see from product descriptions that the output voltage and amps are configurable, but no one mentions the input supply. You say it's DC, what voltage would it be expecting? (I'll keep looking for a data sheet...)
- Will it accept input amps greater then it outputs, or would they need to match?
- Being it's intended for solar storage, it seems to have a HUGE output capability. I'm thinking 1 or 2 amps - would it go that low?

Sorry - newbie question :-(

 

[john61ct]

Given that SC current limiting might not be that robust, get a PSU that's only 20% higher current than the max you want.

The input voltage usually just needs to be 5+V above your desired setpoint, so 19-22V should be fine, normal PV range for nominal 12V.

Best to find a manual or data sheet though.

 

[Hillhater]

If you don't mind, I have a few questions (because I know 0% about solar things):
- I can see from product descriptions that the output voltage and amps are configurable, but no one mentions the input supply. You say it's DC, what voltage would it be expecting? (I'll keep looking for a data sheet...)

It will work with any DC input voltage from 10v, but i would suggest something just BELOW your target pack voltage...IE 24-30v ...
That way if something fails internally, you wont over charge your battery.

- Will it accept input amps greater then it outputs, or would they need to match?...

.. no need to match, the output charge max current is adjustable 0-10A in 10mV steps,. I run mine on a 17A Server PSU, but charge at 5A

- Being it's intended for solar storage, it seems to have a HUGE output capability. I'm thinking 1 or 2 amps - would it go that low?

Yes , as above adjustable current output 0 - 10 A
Full disclosure... the user interface is a bit fiddly with menues and stepping adjustments that can take time and be confusing (to me ?)..... but once set it holds multiple charge profile settings in memory.
I run both 36/40v packs and 48/50v pack at times.
Honestly, for the price ( < $50 ) , its hard to complain for a fully adjustable charger..rather than just a modified power supply.

 

[pickworthi]

Many thanks for your response.
It turns out that Amazon UK carries stock for the MPT 7210A, Prime next day delivery no less, just £42 as well, so much cheaper and faster than Bangood for example (and no import duty hassle).

It is in fact cheap enough to get one and play around with it, which is what I've done. From what you say this will be exactly what I need - I'll report back in a few days when I've had a chance to have a good fiddle.

Thanks again!

 

[Hillhater]

It is in fact cheap enough to get one and play around with it, which is what I've done.

That is exactly what i did..aa couple of years back..and it has not failed yet ! :wink:

 

[pickworthi]

So far I am very pleased with the MPT 7210A as a variable rate charger alternative.
£42 for it, and £14 for a 24 volt - 15 amp power supply is very much less than the approx $100 + shipping + 20% import VAT + £8 customs handling charge for the Lunacycle charger. And that's not even counting £50ish for a transformer. I can have three chargers for less than I thought two would cost me - result, and many thanks to Hillhater for setting me off on this path

First reaction - the user interface is crap. Coming from IT, I don't know how you electronics guys put up with this. I spent many hours getting to the point that I had three profiles I could use, and having it not automatically start charging when I powered it on. Got there in the end. Trick seems to be to set profile 00 as having 0V & 0A. Then it starts up and waits for me to select the profile I want.

I'm using this site for data on batteries: https://batteryuniversity.com/
According to it. 70mV equates to approx 10% capacity for Lithium ion batteries. So I've set 3 profiles for my 10S packs:
100% charge - 42.00 volts
90% charge - 41.30 volts
80% charge - 40.60 volts

I've had one go at the 90% setting. Amps set to 2A max. Amps started high and dropped off as expected, with voltage at around 4.25V. It then sat for an hour at 0.03 amps / 41.25 V. It looks to me like 0.03 amps may well be the "finished" state for the pack BMS. I'd appreciate any insight into that.

Fiddling continues...

 

[john61ct]

batteryuniversity.com is OK for general noob orientation, learning jargon etc, but a very flawed resource, full of over-generalizations, gets many details flat out wrong.

> the user interface is crap.

That is a given with cheap chinese.

> three profiles I could use

Be grateful there even is that feature, at all, most you need to manually set your parameters from scratch every time.


> 70mV equates to approx 10% capacity for Lithium ion batteries.

Not sure what you're saying there.

mV is voltage, capacity is mAh or Ah, charge rate is amps or mA, but usually expressed as a C-rate for apples to apples

 

[john61ct]

> 90% charge - 41.30 volts

> I've had one go at the 90% setting. Amps set to 2A max. Amps started high and dropped off as expected, with voltage at around 4.25V

You (or your setup) should **never** allow any cell to go over 4.20V

not just harmful to longevity but potentially damaging

even dangerous - hope you are not doing this stuff near any human living space!

For decent longevity, define 100% Full as 4.15V

For maximum longevity, 4.05V or maybe 4.10, depends on chemistry, specific cell model, takes some testing that's rather involved.

The SoC difference is likely to be low single digits in any case, so lower is better unless getting every mAh of range is critical to your use case?

There is **no** need to sit at the setpoint voltage at all (CV / Absorb stage) certainly not for more than a few minutes if precision is required stop when current falls to 0.05C

Really, CC-only, "charge to setpoint and Stop" is just fine and much easier to automate, a simple adjustable LVC cutting off your charger at its source.

A BMS or the main charge regulation can act as a redundant failsafe for when the primary stop-charge circuitry fails.

Safety first!

 

[pickworthi]

Sorry to send you off on a safety rant with a typo :-(
Of course I understand 42 volts is max for this pack (4.2 per cell).

What I meant to type was 41.25 Volts.

And ths 70Mv figure relates to the battery OVC when capacity reduced by 10%.

 

[john61ct]

Sorry to send you off on a safety rant with a typo :-(
Of course I understand 42 volts is max for this pack (4.2 per cell).

What I meant to type was 41.25 Volts.

No harm in reminding, even if only for others, many do not (act as if they) appreciate just how quickly these can burn buildings down.

Since this is not a proper charger, just a power supply, it is up to **you** to ensure this

> with voltage at around 4.25V

doesn't ever happen.

A bulk charge profile at lower pack-level voltage helps

but is not sufficient if the cell balance delta gets out of whack at the top, end of charge SoC ranges.

> And ths 70Mv figure relates to the battery OVC when capacity reduced by 10%

I still have no clue what you mean there, maybe someone else can translate, ELI5

 

[Hillhater]

.......Since this is not a proper charger, just a power supply, it is up to **you** to ensure this.....

John, why do you say this is not a “proper charger”. ?

 

[pickworthi]

I still have no clue what you mean there, maybe someone else can translate, ELI5

I know you have already dissed this source, but the article here explains it:
https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Table 4 is the gist of it.

 

[john61ct]

John, why do you say this is not a “proper charger”. ?

Because that implies a device that automatically stops charging based on some algorithm designed to estimate when the target pack is Full.

Better if it has a choice for selecting say 80%/90%/100% Full

Best of all, both voltage setpoint and AHT (CV / Absorb stage hold time) are user-custom adjustable.

 

[john61ct]

the article here explains it:
https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Table 4 is the gist of it.

Still no idea of which of the many ideas there this wording might relate to.

ths 70Mv figure relates to the battery OVC when capacity reduced by 10%.

The term "capacity" usually refers to a fixed attribute of a cell measured in mAh, not something that changes with SoC%. Capacity does get reduced over time as cells wear, so 50% SoC is a different mAh quantity after 100 cycles (if you get that many)

HVC or high voltage cutoff is the more useful term for what I think they are saying with OVC, over-voltage implies maybe a dangerous level?

The central idea is the general statement

"Charging to a lower charge point results in more life cycles"

but below 4.05V most people feel they are "sacrificing too much capacity" i.e. range.

________
So the 70mV means relative to the drop-dead high point specification from the vendor, so 4.13?

Am I on the right track?

Try to formulate a concise sentence that expresses your understanding of the idea, happy to help as a learning exercise for both of us.

Note that page's caveats about cobalt-related LI chemistries, its details may or may not apply to the different ones (likely manganese) used in yours.

Something on that page kept crashing my browser, I do have script/ad blockers, so I did not do more than skim.

 

[Hillhater]

For sure its not perfect..its chinese, cheap, lousy interface, etc etc.
But mine certainly cuts off when the set voltage is reached, and rather than random %% settings you have to use accurate voltage settings ( a charger does not know what 100% capacity is anyway !..you have to tell it)
But basicly it is a charger with Lithium cc/cv programe... the same as the majority of home chargers but with more flexible inpu and output settings, charge monitoring, ( amp rate, ah cumulative, time, voltage)
So in common terminology, it is a lithium charger,...not the ultimate and possibly not exactly what you want, but a charger no less)
Can you suggest a charger with better functionality for under us$50 ?

 

[john61ct]

OK great didn't know that, thanks for clarifying.

Fully off, no voltage at all on the charge circuit to the battery?

Someone was saying they couldn't get their Satiator to do that, seems suss to me

 

[markz]

BMS Battery has some chargers for 240V
https://bmsbattery.com/13-ebike-charger-ev-charger

This place has a couple, one reasonably priced but out of stock ATM, another kinda pricey.
https://ebikes.ca/shop/electric-bicycle-parts/chargers.html

Meanwell has some good units, HLG for use with LED's,
I've used the HRP model with good success.
Find them on ebay, mouser.com and the like.

 

[john61ct]

Aha, I forgot that 7210A unit was designed to be a solar controller.

Charger it is then, of course it terminates, great hack!

Link to the upstream PSU/Charger you use to feed it?

Input min/max range for voltage?

Real life safe (not stressful) input current max?

 

[Hillhater]

Link to the upstream PSU/Charger you use to feed it?..

I wish i could !
Currently i ise a “ Multi -Out charger...an unbranded 220v charger that came from a busted Escooter.
I have never been able to find ANY reference to this unit online anywhere ?
I run it at 40v 10A
BUT, i have also run it friom a 24v, meanwell “clone” without issues.

Input min/max range for voltage?

For the 7210 ?.... that is 12v up to 60v
Spec’s here..
https://www.ebay.com.au/itm/LCD-MPPT-Solar-Regulator-Charge-Controller-24-36-48-60-72V-Boost-MPT-7210A/112451914404?_trkparms=aid%3D1110009%26algo%3DSPLICE.COMPLISTINGS%26ao%3D1%26asc%3D20200220094952%26meid%3D796afbe9fca042d09af12abd6c4b37d7%26pid%3D100008%26rk%3D3%26rkt%3D12%26mehot%3Dpp%26sd%3D353189510581%26itm%3D112451914404%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3Ddefault%26brand%3DUnbranded&_trksid=p2047675.c100008.m2219

Real life safe (not stressful) input current max?

. 7210 charging current ?.... I have never tested that... but it is rated at 10 A max, 600W

 

[john61ct]

If you ever do get a round tuitt, I would appreciate it

Also curious if they could be stacked, set to the same output voltage

inputs isolated of course I bet the SC is not, at all

 

[pickworthi]

the article here explains it:
https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Table 4 is the gist of it.

Still no idea of which of the many ideas there this wording might relate to.

ths 70Mv figure relates to the battery OVC when capacity reduced by 10%.

The term "capacity" usually refers to a fixed attribute of a cell measured in mAh, not something that changes with SoC%. Capacity does get reduced over time as cells wear, so 50% SoC is a different mAh quantity after 100 cycles (if you get that many)

HVC or high voltage cutoff is the more useful term for what I think they are saying with OVC, over-voltage implies maybe a dangerous level?

The central idea is the general statement

"Charging to a lower charge point results in more life cycles"

but below 4.05V most people feel they are "sacrificing too much capacity" i.e. range.

________
So the 70mV means relative to the drop-dead high point specification from the vendor, so 4.13?

Am I on the right track?

Try to formulate a concise sentence that expresses your understanding of the idea, happy to help as a learning exercise for both of us.

Note that page's caveats about cobalt-related LI chemistries, its details may or may not apply to the different ones (likely manganese) used in yours.

Something on that page kept crashing my browser, I do have script/ad blockers, so I did not do more than skim.

Apologies, another typo. I am dyslexic, but no excuse on here really.
OVC should be OCV which is Open Circuit Voltage.

An there is this paragraph right next to table 4:
"Guideline: Every 70mV drop in charge voltage lowers the usable capacity by about 10%"

So I've set 3 profiles for my 10S packs:
100% charge - 42.00 volts
90% charge - 41.30 volts
80% charge - 40.60 volts

All there is to explain really, that and, as I said, this is a starting point from which I will calibrate (for fiddling read calibrating).

 

[john61ct]

Yes, all that just reaffirms my comment about BU as a resource,

overall the article does convey the right general concept,

but not to be relied on for specific details, poorly worded, over-generalised to the point of inaccuracy.

I think you understand well enough no point in parsing it further.

______
The key is knowing that there are hundreds of V/A combinations that will get to the same SoC-at-rest result.

Voltage is just one component, 4.13V can get you to 85% or 95% or even overcharged if held long enough.

So long as you get to where you want, measured at rest isolated for an hour doesn't matter much how you get there.

 

[electric_nz]

For what it’s worth I have the exact same charger 240V version and 52v output, so they do exist! Worked well for years but recently the 80-90-100% stopped working and only charges to 100%- 58.8V. Still just fine, generally I just turn it off sometime before termination.