Power up.... Power down

[scottyb]

Post #5 concerns me JB

I'm going to guess a battery short can be intermittent too.

[Dela]

Reading about reconditioning batteries with Epsom salt, should I try that johnnie/Scotty?

They are fairly new, under a year old, but could I have ruined them by going to far?

Originally Posted by Dela

Reading about reconditioning batteries with Epsom salt, should I try that johnnie/Scotty?

They are fairly new, under a year old, but could I have ruined them by going to far?

[Sir Nuke]

Originally Posted by crash test dummy

you need a bigger bag of pop corn.......


BIG POPCORN.jpg

[JohnnieB]

Originally Posted by scottyb

Post #5 concerns me JB

I'm going to guess a battery short can be intermittent too.

It concerns me too. And I've been in electronics long enough to accept the fact that almost anything is possible.
I have no idea what the likelihood of an intermittent short in battery cell is, but I believe it is possible.

The pack voltage appears to be dropping to a ridiculously low value, and three things can cause that. (Maybe more, but they don't come top mind.)
1. An Amp draw of several hundred Amps.
2. Excessive resistance in the High current circuit.
3. Bad cell or cells.

I took a peek at Dela's build thread and he is using six CR-190 (8V 190AH) batteries, so the motor or something ought to be glowing red and smoking if the Amp draw was actually high enough to drop the pack down to 25.5V (1.06VPC). Of course, if the batteries were taken that low, they are probably boat anchors now, since anything below 1.5VPC (36V for a 48V pack) causes irreversible physical damage to the plates.

Excessive resistance within the battery pack itself, wouldn't cause a low voltage reading of the pack itself. The batteries are connected in series, in fact, all twenty-four 2V cells are connected in series, and the voltage measured across a series circuit is the sum of all voltage sources and drops within that circuit.

If the dash mounted DVM used to monitor the pack voltage isn't connect ed directly across the battery packs main terminals, it may be possible that excessive resistance in the high current circuit to cause a low voltage reading on the DVM. Need to know where exactly the DVM is connected.

Monitoring individual battery voltages with a handheld DVM, would be about the only way of narrowing the problem down more.

[JohnnieB]

Originally Posted by Dela

1. Reading about reconditioning batteries with Epsom salt, should I try that johnnie/Scotty?

2. They are fairly new, under a year old, but could I have ruined them by going to far?

1. Personally, I would make absolutely sure the batteries are bad before I tried any snake oil remedies.

2. Yes, if the voltage you saw (25.5V) was truly the pack voltage, rather than an erroneously low reading caused by factors unknown at this time, the batteries have very likely been seriously damaged.

Anything below 1.5VPC (Volts per Cell), which is 36V for a 48V pack, starts sucking active material off the plates and it becomes conductive sludge in the bottom of the jug, if it doesn't lodge between the closely spaced plates and create a short before it settles to the bottom.
(FWIW: This is roughly the same thing that happens when snake oil is used)

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Attach a handheld DVM to each battery, one at a time, and record what the voltage drops to when the cart is misbehaving.

Also, where are the Dash mount DVM leads attached?
What controller are you using?

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Let's find the problem before throwing parts at it.

Originally Posted by JohnnieB

1. Personally, I would make absolutely sure the batteries are bad before I tried any snake oil remedies.

there it is !!!

[yurtle]

Originally Posted by JohnnieB

It concerns me too. And I've been in electronics long enough to accept the fact that almost anything is possible.
I have no idea what the likelihood of an intermittent short in battery cell is, but I believe it is possible.

"Short" or "long"? Think about it.

Originally Posted by yurtle

"Short" or "long"? Think about it.

i don't get it !!

[scottyb]

Originally Posted by crash test dummy

i don't get it !!

Of course you don't get it - none of us get it - it's electrical engineer humor

Which is akin to insurance humor...... 'I got you covered' - see how i did that there ?

Seriously though for Dela - test individual batteries under cart load (as suggested). & Give us the results and we can go from there.