36V battery not outputting full amount of actual battery voltage

[jbjsabu]

10s3p scooter battery shows 38.4V between B+ and B-.
The 10 individual cell groups vary from 3.94V to 3.78V.

The BMS output on the XT-60 connector going to the scooter
is only 28.3V. The charger indicates "charging" and
output voltage is slowly rising about 1.7V per hour.
Charger output is 42V.

The batteries are not warm, but the charger is pretty
warm. I am wondering why the output voltage is not
the full 38.4V of the B- to B+ voltage.

Will the BMS kick in after awhile and deliver the full
battery voltage? Is this going anywhere?

 

[Chalo]

Read the voltage at the + plug terminal and the B- pad on the BMS. If it's correct and steady, then your problem is the BMS isn't happy and has cut off output power, or is malfunctioning.

 

[jbjsabu]

It is showing 29.7 V up from original 28.3V (with actual battery B- to B+ now up to 40.4 V from original 38.4).
However, the charger is now showing green so I guess it's done trying.
What part in a BMS decides to quit charging? The charger is still
putting out 42V.

 

[Chalo]

Maybe you have a busted sense wire to the BMS, or a bad solder joint on one of them.

 

[jbjsabu]

Wires and joints are OK. There is a steady increase of 4v each battery group step
between B- and B+ including right on the sense wires right up to 40V.
The BMS is this kind:

 

[jbjsabu]

I have read about putting 42V directly on the XT-60 output to reset? wakeup? poke the BMS.
If this is a real thing, how long to leave it on. Is there a danger of ruining more stuff?

 

[Chalo]

I have read about putting 42V directly on the XT-60 output to reset? wakeup? poke the BMS.
If this is a real thing, how long to leave it on. Is there a danger of ruining more stuff?

There's no harm in it. Don't leave it on for long, or you could overcharge one or another cell group. Just a moment should do it if it works at all.

 

[jbjsabu]

Oh well, nothing doing. Two groups are setting at 4.15 so I don't want to do that
too many times.
I have a simple Daly BMS I bought just in case for something like this so I will try to hook that baby
up this weekend.

 

[jbjsabu]

AND Thanks for the ideas!

 

[jbjsabu]

I was just thinking, the Daly BMS has one short-wired temp sensor - the old BMS has three
temperature switches - 50C, 65C and 70C.

What if I put these in series with three various sense lines?

Will the Daly BMS safely shut down until the temperature cools off again?

Since Daly doesn't have thermal protection, maybe overheating is not really a
problem with these battery packs? Also, 50C (122F) seems kind of low for a summer ride.

I have sent Daly an email asking these questions, but have not heard back yet.