TIFU'ed - Valence U1-12RT

[RschDev]

I bought a used Valence 40AH battery mainly because the manufacturer's website said that "Built-in automatic protection for over-charge, over-discharge and over-temperature conditions". I hooked it up through a volt/amp meter to a small compressor refrigerator to see how long it would run. It ran overnight and in the next morning the volt/amp meter was blank. An analog voltmeter showed 0 volts. I connected it to a 2 stage 3 amp 12 v Battery Tender charger and have run it for about 36 hours. In the first hour the voltage climbed to 3 volts and now shows 4v with the charger disconnected. The green light on the top of the battery is still blinking. Is it safe to assume that the battery is toast? Where did I go wrong?

 

[RschDev]

I may have found the problem. I removed the shunt from the circuit and now the charger is showing that it is supplying 12 volts to the battery instead of 3 volts. If this works, I'll have to figure out how I monitor the state of the battery and charge it.

 

[PHoganDive]

Is the shunt open circuited? They are normally darn near a short circuit (a few milli-ohms)...I can't see how removing it would make any difference if it was still ok.

 

[RschDev]

Is the shunt open circuited? They are normally darn near a short circuit (a few milli-ohms)...I can't see how removing it would make any difference if it was still ok.

Maybe it has to do with the smart charger thinking that the battery is charged and putting it in float mode?

 

[RschDev]

So I let the 3 amp charger run overnight. This morning the battery is reading 4volts without a load and 3 bolts while hooked up to the charger. This is without the amp meter connected. I am so confused.

 

[b.james]

So I let the 3 amp charger run overnight. This morning the battery is reading 4volts without a load and 3 bolts while hooked up to the charger. This is without the amp meter connected. I am so confused.

Me too but its a 12V battery yeh? You have connected a 12 V charger to it and let it charge overnight . Its a Valence 40AH battery and that has a BMS built inside it . If any of the fault conditions occur the BMS will disconnect the battery.

So if you connect an external charger to it how will the BMS turn back on?
If it does not then no charge will flow into the battery. You say current was flowing but 36hours?? Crikey 3 amps for 36 hours is 108 Ahs nearly 3 times its capacity . What were you thinking.

It comes with a special connector and it might only accept charge through that I think. If you can get the top off you can find the BMS negative wire to the battery and connect the neg charger wire there. The pos goes on the normal pos terminal. Otherwise you must connect the charger to that charge lead correctly and not short anything. You should check the battery voltage at that place first and if over 14 volts don't give it any more.

If you do this only charge for 15 minutes or so then try connecting to the two outside terminals again as the BMS will switch itself back on as the cell voltages rise and you don't want to overcharge it. At this point I don't think you will have done any damage to the battery hopefully as the BMS should protect it. But I don't understand why you get 4 volts atm anyway.

If all else fails , rip the plastic top off ,pull out the BMS ,connect your chargerto pos and neg leads on the inside and charge . You can always buy a cheap BMS for $20 and solder it in. Seal the plastic back up a bit. It'll last 10 more years.

 

[RschDev]

I connected it to my truck battery with jumper cables today for about a half hour, with the engine running. It's now reading 10V, so progress. I have a special edition of the battery tender coming today that says it's for lithium batteries.

 

[RschDev]

I have a new cheap wall wart charger that has a setting for LiFePo batteries. That one is working well. Thanks for all the help.