BMS for travel with XLR charger

[jefferso]

shirley_hkg mentioned a BMS which can be plugged in to a normal charger with an XLR plug

https://www.wheelchairdriver.com/board/ ... 40#p205009

He made one for me and it seems to be working well. It has an app for the phone to monitor the charge via bluetooth. I've been testing it with my Victron IP22 bluetooth 24V 12A charger which has a "power supply" mode which I've been using, set to 28.4V.

The IP22 is relatively small and light and the bluetooth is nice to see what it's doing. Adding the BMS and cables is a bit more to carry on a trip, but of course it's much less heavy and bulky than a PL8 and power supply.

It's great that for a day trip I don't even have to think about charging with the 160Ah pack. And with this I can safely charge overnight on longer trips. I guess in theory, if I charge 6 hours while sleeping it could put back about 70 Ah. I'll post some more details and screenshots from the app over the next few days.

[shirley_hkg]

My friend charges this way mostly, as carer always mess things up with PL8.

He charges with PL8 occasionally, to check status of battery.

[jefferso]

Here's a screen recording from my iPhone showing the charge after it started to balance.
In the individual cells view I'm not sure what the different colours mean; blue, green and red.


youtu.be/RamlHfE1XoA

[Burgerman]

The balance "looks" great at that low 3.46V per cell level, at this ow voltage point.
Its decieving though because while they are all very close together in voltage, they may be quite far apart in actual capacity. The cells only just begin to show a difference at this voltage level. It works to a degree but it really needs to be balancing at 3.550V. (Or according to manufacturer 3.6 to 3.65V with a BMS). At the top of charge. Its better than nothing, but you ideally should use the PL8 as well every few charges with full balance at 3.550V or 3.600V.

It will allow a "safe" charge however. Albeit slow.

[jefferso]

The device has a lot of settings in the "Advance Settings" section. My phone screen is small so it takes a lot of screenshots to show them all. I guess it would have kept going higher if I'd left it on longer. It does seem pretty slow at balancing. Seems good for travel anyway. I definitely prefer the speed of the PL8 when home so hopefully that will keep it balanced most of the time.

[Burgerman]

It will be ok for use when traveling.
But your cells are 160Ah?
So at say your 12A charge, even without any slow balancing stuff going on, it would take 13.5 hours to charge.
If you must use a BMS its much better to have it off board. Because of safety and because thers no space on a chair for it. And its only wanted for charging and all the so called safety features are not wanted on a powerchair.



Imagine how long it takes however with bigger 230Ah (245 tested) cells!
Well actually I dont need to imagine. 245Ah div by 12A is a crazy 22 hours...

Lithium is great because we can have a much bigger fuel tank at the same price, and same volume.
But its so much bigger (literally 6x bigger in the case of the 230Ah /245Ah) that we also need 6x the charger power output in order to charge in the same time frame (at least for the bulk of the charge). If your lead charger is 8A, then you need 48A charging to be equivelent! Which is where the 40A PL8 or other hobby charger becomes ideal.
BUT of course even on a busy holiday you dont always need a full charge though. Because lithium allows a bigger pack its much harder to use it all up to begin with.

[jefferso]

Yes, 160Ah cells. Hopefully I won't be needing to completely recharge. But if I start a trip with a full charge, and I use 20Ah in a day for my ventilator, I know I won't have much trouble putting that much back in overnight, plus another 50Ah. I'm not sure if I'll use 50Ah in a day driving around, but I guess it's possible if I go somewhere with lots of hills or take a really long trip. So even if I do use 100Ah on a long day, If I can put 70Ah back in overnight, and/or a few more on a train and/or in a cafe, I'll still probably have enough not to worry the next day, even if it's not completely full and balanced again.

I wish I had room for 230Ah, but having 160Ah is so much more than the lead bricks so I don't think I'll be complaining for a long time.

Below is how the Victron IP22 shows up in my phone in Power Supply mode in the Victron app.

[jefferso]

My friend charges this way mostly, as carer always mess things up with PL8.

He charges with PL8 occasionally, to check status of battery.

Can the BMS handle more than 12A? The XLR plug has an XT connector on the other end to plug in to the XT plug on the BMS. I imagine that can handle more current than XLR but what's the limit for the BMS itself?

[wes4dbt]

Jeff,

It looks like the IP22 doesn't come with an output cable. I've got a couple of the IP65, It has an two wire output cable that I cut off the end and connect an XLR plug cable.

How does yours work?? Also, where did you find the XLR cable? All I could find basically was very small wire microphone cables. I've been buying cheap used wheelchair chargers from ebay and just cutting off the cable.

Thanks for any info.

[Burgerman]

That all sounds highly dubious quality wise. And cable quality wise. You need a genuine branded Neutrik Male XLR connector, at 12A.
Or melt issues can occur. Poss damage to joystick too. Ask permobil! They may all look the same... They tried a cheaper connector on their "special" charger and had to replace countless joysticks

And just ordering a quality connector is cheap and easy. I get a bag of 6 for about £15. Soldering a cable onto it is literally a 1 minute job. If you honestly cant do it take it to any hobby shop or anyone that can do electronics, or you local college or school. etc. Its really quite trivial. They probably wont charge you. Buying chargers to cut off the cable?

The ones you NEED for 10 and 12A are these NC3MXX only. Lesser ones dont like high currents...
Are actually safe and certified at 16Amps. And buying just 1 at a time still only £4.50... Use 2 to 2.5 sqmm cable. 14swg.

https://www.ebay.co.uk/itm/261112022664

Neutrik NC3MXX
Connection Type XLR
Gender male
Electrical
Capacitance between contacts ≤ 4 pF
Contact resistance ≤ 3 mΩ
Dielectric strength 1,5 kVdc
Insulation resistance > 10 GΩ (initial)
Rated current per contact 16 A
Rated voltage < 50 V
Mechanical
Cable O.D. 3.5 - 8.0 mm
Insertion force ≤ 20 N
Withdrawal force ≤ 20 N
Lifetime > 1000 mating cycles NOTE 3 YEARS DAILY USE, REPLACE!!!
Wiresize max. 2.5 mm²
Wiresize max. 14 AWG

[wes4dbt]

We've had this "make your own connector" discussion before and I tried solder my own. Didn't work, don't have the hands and not steady enough. I'm sure I could find a way to someone else to do it but don't see the need.

Why should there be a melting issue? The XLR cables are rate for higher amps than the IP65 8amp output. What am I missing?

[Burgerman]

The connectors. Some are not capable of even 5A and get loose or oxydise and burn the joystick sockets and the heat causes more oxidation, rinse and repeat. Gets worse over a couple of charges.

At 5A any cheap connector probably OK.
At 8A the cheap ones start to get hot after some use, and can cause burning on odd occasions but usually ok.
At 10A as many chair chargers now are you need heavy 2mm cable and quality branded XLR. (like the permobil 10A CHARGER that can melt the joystick socket as permobil found out to their cost when using a crap make of XLR on their chargers. $$$$$.)
At 12A its quite critical that you use a genuine Neutrik NC3MXX or sooner or later it is likely to get very hot and melt the joystick connector. Those are quality, and good for 16A so have a bit of reserve! Dont exceed 12A though.

An example...
https://www.wheelchairdriver.com/board/ ... =2&t=11183

[wes4dbt]

The connectors. Some are not capable of even 5A and get loose or oxydise and burn the joystiv=ck sockets and the heat causes more oxidation, rinse and repeat.

At 5A any cheap connector probably OK.
At 8A the cheap ones start to get hot after some use, and can causeburning but usually ok.
At 10A as many chair chargers now are like the permobil one that can melt the joystick socket as permobil found out to their cost when using a crap make of XLR on their charger. $$$$$.
At 12A its quite critical that you use a genuine Neutrik NC3MXX or sooner or later it is likely to get very hot and melt the joystick connector. Those are quality, and good for 16A so have a bit of reserve! Dont exceed 12A though.

An example...
https://www.wheelchairdriver.com/board/ ... =2&t=11183

Good to know.

I've avoided the little 3 or 5 amp charger cables. Glad I did.

[jefferso]

Jeff,

It looks like the IP22 doesn't come with an output cable. I've got a couple of the IP65, It has an two wire output cable that I cut off the end and connect an XLR plug cable.

How does yours work?? Also, where did you find the XLR cable? All I could find basically was very small wire microphone cables. I've been buying cheap used wheelchair chargers from ebay and just cutting off the cable.

Thanks for any info.

Here's a post with a photo:

https://www.wheelchairdriver.com/board/ ... 16#p134916

I think I ordered some cable, or possibly cut one from a broken charger, then soldered an XLR plug from ebay to it with the help of my partner. It was one of her first soldering jobs. I know it seems incredibly easy once you're experienced, but especially if you don't have a very good soldering iron, it can be difficult if you've never done it before. It actually stopped working because the soldering wasn't very secure and had to be resoldered. It has been fine for years now though it probably doesn't look very pretty inside.

The IP22 has some weird terminals with screws on top which cause metal plates to squeeze together. The bare ends of the XLR cable are twisted and folded over between the metal plates then tightened down with the screws. It has a little plastic cover which snaps over the fuse holder and the access to the screws.

Once someone picked it up by the XLR cable and one side slid out while I was on a trip. I was worried it was broken but we found it had been pulled out. Just had to twist the bare end of the cable again, loosen the screw, slide it in and tighten it down well again and it's been fine since. It's useful to have a multi-tool while traveling.
I've trained most people who help me to not pick things up by their cables but you never know what someone will do when they're in a rush.

[wes4dbt]

Thanks Jeff,

Thought you might have found a cable supplier I missed. I'm always hoping. lol

[shirley_hkg]

Can the BMS handle more than 12A? The XLR plug has an XT connector on the other end to plug in to the XT plug on the BMS. I imagine that can handle more current than XLR but what's the limit for the BMS itself?

The XT60 can do 25A easily, but limits to 10a by the XLR.

BMS is rated @40a in and out.

[Burgerman]

Are actually safe and certified at 16Amps. And buying just 1 at a time still only £4.50... Use 2 to 2.5 sqmm cable. 14swg.
Its the joystick internal wires that limits it to 12A max.
If you dont use that, then:

https://www.ebay.co.uk/itm/261112022664

Neutrik NC3MXX
Connection Type XLR
Gender male
Electrical
Capacitance between contacts ≤ 4 pF
Contact resistance ≤ 3 mΩ
Dielectric strength 1,5 kVdc
Insulation resistance > 10 GΩ (initial)
Rated current per contact 16 A
Rated voltage < 50 V
Mechanical
Cable O.D. 3.5 - 8.0 mm
Insertion force ≤ 20 N
Withdrawal force ≤ 20 N
Lifetime > 1000 mating cycles NOTE 3 YEARS DAILY USE, REPLACE!!!
Wiresize max. 2.5 mm²
Wiresize max. 14 AWG

[jefferso]

I went on a 4 day trip via Eurostar train to the Netherlands and then Stena overnight ferry back to the UK. I used the BMS with Victron IP22 charger once overnight on the third night at 6 amps. I guess it put back about 40 Ah, which was good because a full charge after I returned put back about 120Ah, so without the BMS charge, it would probably have fully discharged the 160 Ah capacity of the pack.

40 Ah is an estimate based on the BMS software showing it was charging at about 5.75 amps (Victron charger set to power supply mode at 6 amps) for about 7 hours. I couldn't figure out if the BMS software shows the total Ah added to the pack anywhere.

It was so great to be able to go wherever we wanted without having to think about "can I sit next to a socket at the cafe and charge while we eat…" or "will it charge enough tonight for all of tomorrow?" I actually forgot about charging for the first two days. That never would have happened with the MK batteries. Charging used to be on my mind all the time.


Full charge on return:

[Burgerman]

Would the 230Ah (244 actual) cells have done the whole trip without charging? Presumably yes. Shame those didnt fit.

Recharge looks perfect. Those are Docan eve cells are they not?

It good regardless. When you consider that you only get around 35Ah if you run a set of GRP 24 lead batts until the thing stops... And return about 40.
So you returned roughly THREE complete charges for sets of grp 24 lead batteries! (120Ah) when you got home. Or 4 sets of batts overall if you include the single 40Ah charge.

[Burgerman]

Thanks Jeff,

Thought you might have found a cable supplier I missed. I'm always hoping. lol

If you were not the wrong side of the atlantic I would take your connectors, solder you a cable and send it back!

It may be easier to call into some RC hobby shop, preferably not a big store, toy type place but some back street operation that has real hobby enthusiasts. Theres one in most towns. Getting a volunteer to make you a cable should be easy! If you are used to that stuff it really is trivial, a matter of 5 mins.

[Burgerman]

Thanks Jeff,

Thought you might have found a cable supplier I missed. I'm always hoping. lol

If you were not the wrong side of the atlantic I would take your connectors, solder you a cable and send it back!

It may be easier to call into some RC hobby shop, preferably not a big store, toy type place but some back street operation that has real hobby enthusiasts. Theres one in most towns. Getting a volunteer to make you a cable should be easy! If you are used to that stuff it really is trivial, a matter of 5 mins. About 15 seconds of actual soldering once you have the skills.

I make up leads and cables for hobby stuff, chairs, in fact many things all the time. I am probably better now after 50 years of doing that stuff than most. But I started doing that at about 13 on batteries etc for my model planes. And to make "tin plate" fuel tanks for Control Line stuff. And Free Flight. Once learned its invaluable. Unless your hands cant do it... With me its my eyes! 65...

[jefferso]

Would the 230Ah (244 actual) cells have done the whole trip without charging? Presumably yes. Shame those didnt fit.

Yes, 230 Ah would have easily done the whole trip without charging. I still wonder if there is a way to fit them…

Recharge looks perfect. Those are Docan eve cells are they not?

Yes, Docan EVE 160Ah solar grade A cells.

It good regardless. When you consider that you only get around 35Ah if you run a set of GRP 24 lead batts until the thing stops... And return about 40.
So you returned roughly THREE complete charges for sets of grp 24 lead batteries! (120Ah) when you got home. Or 4 sets of batts overall if you include the single 40Ah charge.

It would have impacted the experience of the trip to have to charge MK gels every night. And a late night with an early start might mean a not quite full charge, and I'd have to think about whether I'd use the vent on the back of my chair which uses the chair batteries, or my usual nighttime vent with its external batteries and think about how much charge is left in them, etc.

[Burgerman]

Since the cells are spot on, stay in perfect balance, you could actually charge without any BMS or anything at all, as long as you dont put back all the Ah. So if it gets above say 3.4V per cell, stop.

That would likely lighten the travel load, some.

[jefferso]

The extra load to bring the BMS shirley_hkg put together is pretty low (see circled in photo) so it's nice to have the option to do a full charge and monitor the cells' individual voltage.

But it's good to know if the BMS got lost/stolen/broken, or I had an unexpected trip, I could charge with an ordinary XLR charger as long as it doesn't go too high.

[Burgerman]

The days when it was over a grand to fit a decent lithium pack are long gone now.

Steve ordered a set of 230Ah ones from Amy at Docan recently.
I dont think it matters as much how we charge them any more. They dropped another £100 since this time last year when I bought a set.
I added red parts...

******************************

The total cost is $508USD via bank wire , all included: £373.60
Breakdown:
✔️ $46 ×8pcs EVE 230Ah LiFePO4 cell with welded M6 studs=US$368 £270.2
✔️ Door-to-door sea shipping: $140 £102.96

Set MK gel lead Grp24 is:
https://www.powerhousegolf.co.uk/acatal ... MK011.html
£299 +£299 = £598 plus delivery...

*******************************

So its not as much of a worry £££ now.
Thats stupidly cheap for quality low impedance EV rated A+ EVE cells that actually measure 244Ah each.
7X the range. 7X the lifespan.
LESS money!