e-Scooter modification (separate Battery Charging)

[ThomasEekels]

My son has a Chinese e-Scooter that currently needs replacement of it's 3rd set of led-acid batteries.
It is a 4-pack 48V system. We think the lifetime of the packs is not optimal and also the chargers tend to burn so it is an expensive km-price.

We now consider a modification for the new set batteries: Separate chargers.
He is looking for batteries now, but already has bought 4 equal 12V chargers with charge management and drip charge features. The idea is not to use a 48V charger for the series pack, but use 4 chargers in parallel, one to each battery.

I have 2 questions for this:

1) Do we need to disconnect each battery out of the series chain before charging them, or can we just keep the chain, connect each battery to it's designated charger and go....

2) I think it is handy to have one plug to connect the scooter to the chargers, so I consider to modify a male-female caravan 13pins Jäger connector set for this. Just designate 4 sets of 2 pins to the 4 individual batteries.


Any thoughts on the plan and on both questions ?

rgrds Thomas

 

[amberwolf]

As long as each charger is isolated, meanint it has no electrical connection between it's output (charging plug) and it's input (AC from the wall), then you do not need to disconnect the batteries to use them all at the same time.

But if (as is not uncommon) the ground of the output is connected to the ground or neutral of the AC side, then they cannot be connected in series because it will short out all but the most positive battery and charger.


To test for isolation, make sure each charger is not connected to anything at all. Set your multimeter to 2-ohms or continuity check, and put the red lead on either of the charger output wires. Then put the black lead on each of the AC connector wires, one at a time.

It should remain in OL on the display. If it beeps continuously (on continuity) or shows a steady reading (on ohms) on any wire, then it isn't isolated and can't be used in series.

If it doesn't beep/stays in OL, then put the red lead on the other charger output wire, and retest the black lead on each AC wire. If it still doesnt' beep/stays in OL, then it should work for them to all be in series. Otherwise...no.

 

[ThomasEekels]

Hi Amberwolf,

thanks for the reply. To be frank, I had no idea there could be a problem like you describe.
Anyway, I will do these test, that is not a problem. But as in AC, the plus and minus will change at 5 hz... would that connection not kill the DC charge end of the charger anyway?

But can you please elaborate on the why of burning some things in the circuit ?

 

[ThomasEekels]

Bytheway.. even if the test shows no connection... could this happen when under lead and switching to charge mode ?

 

[amberwolf]

But as in AC, the plus and minus will change at 5 hz... would that connection not kill the DC charge end of the charger anyway?

I don't understand what you mean.

There's no AC during the test, because as I said you must disconnect the chargers from *anything* before doing this test.

If the chargers *generate* AC even when not connected to anything, then you have a problem, becuase it means they have their own internal battery, and are always running, and then you cannot do this test, so I would then not recommend connecting them in series.


If you mean AC during the operation, when chargers are not isolated designs, then no, there isn't any. The neutral or ground shouldn't have anything on it, that's on the hot wire, which will not be connected thru to the DC side.

But can you please elaborate on the why of burning some things in the circuit ?

I don't know why you would see anything burning, unless you are shorting things out or connecting them backwards. If you see burning, fire, smoke, etc., you should immediately disconnect everything and find out what is shorted or connected wrong, and test everythign to see what still works, then replace all damaged wiring, connectors, etc.

Bytheway.. even if the test shows no connection... could this happen when under lead and switching to charge mode ?

If you mean, could it make a connection between the two sides when powered, when it does not when not powered: that's very unlikely. There would be no sense in a design that disconnects grounds when not powered (though many may disconnect positive side connections with a relay, but the positive side should never be connected to the AC side anyway).

 

[ThomasEekels]

Sorry if I was unclear.

To my knowledge, AC means that there is no permanent ground, but plus and minus will change every 1/50 second.
So having a connection between the charge output ground (minus) and the AC ' ground' , would connect plus to that DC ground also every 1/50. wouldn't it ?

 

[amberwolf]

To my knowledge, AC means that there is no permanent ground, but plus and minus will change every 1/50 second.
So having a connection between the charge output ground (minus) and the AC ' ground' , would connect plus to that DC ground also every 1/50. wouldn't it ?

No, AC ground wire is a literal ground connection, a wire in the building that connects to the actual ground, dirt, concrete, etc., via one of a number of methods.

AC neutral wire has no waveform on it, it is the reference that lets you see the sinewave on the hot wire.

So either of those could be connected to the DC side as "ground" or "reference", though the neutral would not be used if a ground on the AC plug is present (that would be used instead). In a two-wire AC plug, neutral is sometimes connected to DC side.

 

[ThomasEekels]

ok,
these chargers come with a 2 way mains plug, as they are ' double insulated', and have no ground.
I will check next time I see the son

 

[amberwolf]

Ok. In the USA a 2-way plug uses the wide blade for neutral; don't know about the Netherlands. So your first continuity/ohms check can be from that to the DC "ground" (negative).