Wondering about this thing? (How to charge with a 2 battery switcher)

Kingofgreens

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I bought a 2 battery switcher from AliExpress with a charger port.

Now , my question is , what exactly does that charger port do?

Do I put my charger to it and charge both batteries? I don't think so because the switcher dosent hook to the batteries charging connectors.

So , what is the charging option do?
 

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In my opinion that would allow you to charge the batteries while they are all connected to the dual battery discharge balancer.

Also in my opinion that isn't a good idea...just take the time to disconnect each one and monitor them with a voltage meter
during the charging proccess.
 
Just guessing, but it probably charges through the battery main output, bypassing the bms.
 
Just guessing, but it probably charges through the battery main output, bypassing the bms.
Thanks. That's what I was wondering about. I'm still learning every day about these things.

Is that a good idea to let the charger current go back through the output lines and bypassing the BMS?

I want to do everything I can to make these packs last me a long time.

In my opinion that would allow you to charge the batteries while they are all connected to the dual battery discharge balancer.

Also in my opinion that isn't a good idea...just take the time to disconnect each one and monitor them with a voltage meter
during the charging proccess.
Thanks for that input.

I do keep a good eye on my pack as it's charging. I have a nice Luna Charger that I've tested with my meter and ita display is spot on.

This will be my 1st try at a dual battery system. Im a throttle hog and from what I've read that's rough on a single pack while a 2 pack system it so far less stressful on each pack as it switches heavy load back and forth.
 
Thanks. That's what I was wondering about. I'm still learning every day about these things.

Is that a good idea to let the charger current go back through the output lines and bypassing the BMS?

I want to do everything I can to make these packs last me a long time.
I only know it's possible, but I've never done it before. The only advantage I can think of is you could charge at a higher rate than your bms might allow.
 
I only know it's possible, but I've never done it before. The only advantage I can think of is you could charge at a higher rate than your bms might allow.
Might be useful for balancing as well. I guess I'll keep researching before I try it

I'll tinker around with it and try to find some more information.
 
Battery splitters work, but you have to be careful to use matching batteries. You wouldn't want a 48v 20ah and a 48v 40ah on there. You probably want to make sure they are also using the same type and density of cells. It's a lot more risk but cheaper than buying a more expensive battery.
 
You would want different AH to make your AH bigger...for instance...some of these Dual Battery Discharge Balancers will allow
the use of different Voltages such as 48/52 volt batteries but not 48/60 not 52/72 not 52/60.. BUT..

They can be 48v and 52v batteries put together say....52v 25ah and a 48v 15ah will work ( with SOME DBDBs out there in the wild)

The best case scenario being a 48v 15ah and a 48v 25ah battery together....


Make sense now?
 
The bottom line is, charge them seperately and dont be lazy.
Do that and you'll have a long friendship with your batteries ;)
 
This is from https://www.sparkcycleworks.com/index.php/product/battery-blender/


"While it may sound simple, adding a second battery to your ebike is a major challenge. Connecting them in parallel can be is EXTREMELY dangerous. If the batteries aren’t charged exactly the same you risk permeant damage that is not repairable.


The Battery Blender solves this: You can now combine any two batteries of 1)different chemistries 2) different voltages 3)different outputs. The device will manage everything and protect your ride.

When using two different voltages, the Blender will “burn” charge from the higher voltage battery first, then engage the 2nd battery when within the lower voltage battery’s charge. As a result, it is important to turn off the higher voltage battery when it gets to a low level!

For example: If you combine a 52V and 48V Battery, the Blender will accept charge from the 52V only, until 54V is reached. From there, both batteries will output until 43V together. After 43V, only the 48V will be able to put out charge until 40V is reached. As a result, we recommend manually turning off your 52V if it does not have an intelligent BMS."
 
Battery splitters work, but you have to be careful to use matching batteries. You wouldn't want a 48v 20ah and a 48v 40ah on there. You probably want to make sure they are also using the same type and density of cells. It's a lot more risk but cheaper than buying a more expensive battery.
I've been using a generic 52v 20ah triangle for a while when I decided to get a decent quality pack. I then decided to get 2, 21700 52v 30ah packs
so they'll match up perfectly when using this switcher.

My main concern is how fast I take down that 20ah triangle. It does it's job , but I'm a big throttle hog and I don't want to get stuck pedaling my massive beast of a bike home 20 miles.

From what I've read a few places , that switcher will move the current load back and forth when I'm on the throttle hard so each pack won't discharge fast enough to do any serious harm then switch back again so they both get to rest intermittently.

$1000 worth of batteries is worth protecting with a $40 gadget
 
Parallel'ing batteries together is something you should only be doing if you know all the ins and outs already coming into the game. I've been doing it for years but only if I absolutely have to. I much prefer building one big battery than paralell'ing two smaller ones. Mostly because of the risk associated with bypassing the BMS when charging. The issue is that if you charge thru the controller (output) connection, that connection does not have overcharge protection via the BMS, which only provides that on the input (charger) connection. You can buy a BMS that does offer this protection, but its a special order item from your custom battery builder. And if you have a custom built battery you may as well just build one big one in the first place.

The whole charge-thru-the-controller thing happens when you parallel two batteries, then if you use the bike a lot (like, daily commuting with a charge cycle at home and at work... twice a day) you leave the batteries coupled and just charge the bike via one charge connection. The charge to the second battery in line will come in thru the connected controller cables.

On a daily driver bike, its just not practical to disconnect each battery, then go down to your parking spot during the day and switch the charger to the other battery. And God help you if your charging process allows anything more than a few fractions of a volt of voltage difference between the two because when you reconnect the two batteries the current will *instantly* equalize voltage from one flowing to the other and that can be youtube-worthy (and ambulance-worthy).

The solution to this practical necessity (leaving parallel'd batteries connected) is one of these battery equalizer kajiggers. Would I trust one from a Chinese seller on Ali-Express? Hell no of course not. What about the westernized ones? Only if their output matched my output needs. Which they pretty much never do. I parallel batteries on 2wd systems that have current limits in the 60a continuous range and only a very few of those gadgets can be had in ratings that high.

@Kingofgreens you seem to have figured out one of the other absolute musts of paralleling, which is to use identical packs with identical charge cycle counts.

Your analysis on what that kajigger does is a big maybe. Many of them do very different things. Some flip back/forth like you describe. Some pull from one pack, then switch to another when #1 reaches a certain voltage. Still another type draws them both down at once and one I know of even has an option to safely charge both of them thru the battery port via a single input. One thing is for sure... a good one is not going to cost any $40.

BTW that linked Battery Blender is one of the many DATEx variations and that is the one that has all the bells/whistles, as well as the good rep among DIY builders. Here is the only retail seller I know of with proper options. The DATEx web site is the most modern web site of 1994, assuming its still in the state it has been for years. All transactions are email-based.


Two batteries and 60a capacity with charger port (which will learn the hard way you want) is $483.95.
 
Here is the Datex2 direct web site. Sort of. this is his Facebook group, and if you click on the web site link (a Bit.Ly short link) you go to his real web site... which is a Google Docs page. There, to find his Datex2 battery kajiggers, search the page for "Date Dx" and give it a couple of clicks until you see all the different options.

Or wait just try searching on this:

DATE DX2C-60A-XT90S

That will jump you right to a 60a-capable kajigger with proper XT90S plugs and charging function. It says you can safely charge the batteries individually while connected too. Buying directly from him drops the price to about half of that those other guys want that I linked above.

 
So it looks like that charger port is a 5a out power supply and not for charging the packs at all.

Maybe use it for lights , horn , sound , alarm
 

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Pretty sure what it is telling you is YOUR charger output can be a max of 5a. Also note it has a max output of 40a, so whatever your motor wants to drink in, it had better not exceed 40 amps.

You mentioned a Luna charger. I lost three of them (They graciously replaced the first two for free but by the time #3 went bad I moved on). I charge twice a day for a commuter so my duty cycle on chargers is accelerated quite a bit over what most people do.

The owner of Luna acknowledged in straightforward and public fashion (on their FB group if I remember correctly) that they went thru hell trying to find reliable manufacturers for those.

The problem they kept having was they were not shutting off at the designated voltage, and kept charging. Its what caused me to do this, which stopped all my reliability issues:

 
Pretty sure what it is telling you is YOUR charger output can be a max of 5a. Also note it has a max output of 40a, so whatever your motor wants to drink in, it had better not exceed 40 amps.

You mentioned a Luna charger. I lost three of them (They graciously replaced the first two for free but by the time #3 went bad I moved on). I charge twice a day for a commuter so my duty cycle on chargers is accelerated quite a bit over what most people do.

The owner of Luna acknowledged in straightforward and public fashion (on their FB group if I remember correctly) that they went thru hell trying to find reliable manufacturers for those.

The problem they kept having was they were not shutting off at the designated voltage, and kept charging. Its what caused me to do this, which stopped all my reliability issues:

Both of my 2 new packs came with a 58.8v charger .

I prefer the Luna , but I can fall back on those if need be.

I will eventually get a top quality charger , but 5hwta a bit lower on my priority list at the moment
 
Here's a more technical approach to this, that pre-dates the balancing gadgets. It tells you how to do it safely without them, but you need to know something about electronics to put it into play. It also has an extensive Q&A on the subject that can be informative. Note in particular that regen from a direct drive hub also puts power into a battery from the controller side so charging thru the discharge port is not entirely alien to a normal ebike. Just not something the clueless should undertake. Myself, I charged at 1a and I tried to do it to 80% to prevent most (not all) possibilities for overcharge to occur. I still did monthly balance charges but I tried to keep a more direct eye on those.

 
Here's a more technical approach to this, that pre-dates the balancing gadgets. It tells you how to do it safely without them, but you need to know something about electronics to put it into play. It also has an extensive Q&A on the subject that can be informative. Note in particular that regen from a direct drive hub also puts power into a battery from the controller side so charging thru the discharge port is not entirely alien to a normal ebike. Just not something the clueless should undertake. Myself, I charged at 1a and I tried to do it to 80% to prevent most (not all) possibilities for overcharge to occur. I still did monthly balance charges but I tried to keep a more direct eye on those.

That's pretty much the way I've been thinking about it too.

I may at times carry my Luna charger and use it as a little top up here and there if I'm traveling. Set it to 1 or maybe 2a and 80% when the opportunity presents it self while I'd be resting.

Otherwise just charge each pack separately.

Which reminds me .... I need to test and look inside these chargers I got with the packs to see if I can pot them down a little to about 57ish
 

Found the answer.

Looks like there's a couple MOSFETs , a capacitor and a little more circuitry who's function is still dubious but seems to be better than hardwire tethering.
 
My question is with these 2-battery balance dischargers, do they have a transistor that limits current to flow out but not in? Seems like there should be, or else you could build one in, in series, and then the balance discharger would not serve as a bridge between the batteries when charging.
 
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