S120A S-Drive

[Petros1956]

Hi

On the S120A the battery charger input states max 12A, is this governed by the charging cable or the S Drive do you know? The charger I have is 16a.

Many thanks

[Burgerman]

Dont know about scooters. BUT 12A is the max that most mobility systems allow on an XLR style charging system. I charge at up to 100A easily enough on wheelchairs by adding an Anderson 50 connector. Those are 50A hot swap, or 100A+ rated.

According t this TECH data info for S drives, the max charge current for a normally wired and connected XLR is less than the 12A on a powerchair. And in fact limited to 9A maximum.

https://davilot2.ccvshop.nl/Files/10/26 ... manual.pdf

[Petros1956]

Morning

Thanks for the reply. I have been following your page for a few years now and like what you do. If I wanted to pump 16a in from the charger (which is adjustable up 16) I guess I need to bypass the XLR or disconnect the charge cable from the S-Drive.

I don't need a rapid charge as 16a would fill the batteries to 100% overnight. The most I use is about 45 to 50% of the 100AH capacity of the lifepo4's so theoretically it would easily reach capacity the next morning. in fact it did 40% at 8a last night.

Many thanks

[Petros1956]

Morning, can you answer this question please. If I fitted an Anderson socket do I need to disconnect the + lead from the S-Drive as it may back feed to the circuit in there?

Thanks

[Burgerman]

Not sure what you mean by feed back?

You connect the anderson directly to the battery.
The battery and charger no matter is 5A or 50A is a voltage controlled device. So hat if you set it for 14.5V for AGM, or 14.1V for Gel, then it will never exceed this voltage no matter what or where you connect the charger.

Bit its essential that you configure any charger to charge at
CC max Amps.
CV 14.5 or 14.1 depending on battery type.
Set a CV time limit of 8 hours and a termination current of around 0.4A if your charger also has float.
Or 0.2A if it doesent.
Set float to 13.5V indefinite with no time limit. Or to 13.7V if this will remain on charger for less than 1 day.

Double the voltages for 2 in series obviously. Currents do not double.

[Petros1956]

Hi there, thanks for the response

Regarding feedback, I Mean if I connect it to an Anderson socket and pump 16 A in there, which is the max that my charger Will go to. Will it feedback into the S drive via the Positive red cable from the XLR plug as obviously that is connected internally to the batteries Inside the S drive unless it isn’t?

Thanks

[woodygb]

"Feedback" will not be a problem.

[Burgerman]

"feedback" even at 500Amps wont be a problem as it doeent exist!

[Petros1956]

Thanks very much. My next project then.

[Petros1956]

"Feedback" will not be a problem.

Thanks very much appreciated

[Burgerman]

Heres how it works.

The battery is sat at x volts. Lower than the FIXED carefully choosen charge voltage. So when you connect a charger current flows to the battery because of the voltage difference.

How much flows in (in Amps) isnt up to the charger. Well it can be LIMITED by the chargers maximum, but it isnt "pumped in"... The current is determined by the difference between battery volts and charge volts.

The battery draws as much current as is needed to match the charge voltage. How high this current is depends on how low the battery voltage is, the battery internal resistance, how "meaty" the cables and connectors are, etc. Not the charger unless its small... At no point will it exceed the charging voltage. Which should be 28.2V for gel. 28.8 to 29.2V for AGM. And these voltages will be identical on a 5A charger, and a 50A charger. The difference being how long it takes to get to this Voltage point.
As the battery votage rises, the current in Amps naturally falls away. When its close to zero the battery is charged.

To achieve a FULL 100% charge takes around 10 hours with a very powerful charger. And double that with a weedy one. If your charger tells you its done any faster than this then it is wrong. The green "ready" light comes on far too soon on most chargers. And then after this it drops to a lower voltage called float. This will also finish the last 1% of the charge over the next 4 to 12 hours. Depending how early the charger told you it was ready.

This canot be speeded up. Does that last 1% matter as it takes many hours at a low current? Not for range, no. But the battery will die much faster if it only ever gets to 99%. Like less than half its normal cycle life.

The advantage of a powerful charger then is 2 fold:

1. it gets the BULK high amp stage done very fast. That leaves L O N G E R in time for the slow CV stage to complete and so you get closer to a 100% charge in the limited period we have overnight. So the battery lives longer!

2. It allows a boost to put a lot of power back in the middle of a day in a shorter time. So charge for 30 to 60 mins as you check email etc before going out at night. Or anytime you get chance. Batteries love to be full. Hate to be discharged. So that it lowers the average depth of discharge during daily use. Making the battery last 2 or 3x longer at least, before its replaced.

[Burgerman]

Charging at 12A

Took 10 hours here SO FAR and its not yet finished.

It was LIMITED to 12A during the first few hours. But this initial 12A stage put the bulk of the energy back. At 8A it would have added an extra hour or so.

[Petros1956]

Thanks very much great explanation.