12V battery selection

[HoverBoarder]

Hi,

I was wondering if anyone had a suggestion on a light and safe 12V 40AH battery pack that I could use.

I am currently using three 12V 10AH Nimh packs, and I think the best choice for what I need is Lipo (although I am worried about the fire risk from overcharging).


I have a 40AH 13.3V LiFe battery that I would love to be able to use, but the BMS will not let it go down to 12V, and I am not sure if I can safely change this BMS to one that will let me pull 12V.

Thanks!

 

[dumbass]

Hi,

I was wondering if anyone had a suggestion on a light and safe 12V 40AH battery pack that I could use.

I am currently using three 12V 10AH Nimh packs, and I think the best choice for what I need is Lipo (although I am worried about the fire risk from overcharging).


I have a 40AH 13.3V LiFe battery that I would love to be able to use, but the BMS will not let it go down to 12V, and I am not sure if I can safely change this BMS to one that will let me pull 12V.

Thanks!

Do what I do with my 24v packs and install a CEllLog 8 and an alarm. YOu can set the individual cells and the pack voltage for both High and low voltage. The CEllLog8 can handle up to 8 cells. And it only cost $23 + alarm from Radio Shack.

Bob

 

[HoverBoarder]

Do what I do with my 24v packs and install a CEllLog 8 and an alarm. YOu can set the individual cells and the pack voltage for both High and low voltage. The CEllLog8 can handle up to 8 cells. And it only cost $23 + alarm from Radio Shack.

Bob

Thanks!

The CellLog 8S looks like a great device that also works on LiFe batteries. Do you think that I could just replace the BMS on my LiFe battery with a CellLog 8S to be able to run at 12V, or should I get LiPo cells to run with it?

I really like this device though, thanks for the tip:

http://www.jun-si.com/UploadFiles/CellLog_8S.pdf

 

[999zip999]

What brand is your battery round or puch cells ? It sounds like prefect battery what you using it for ?

 

[HoverBoarder]

What brand is your battery round or puch cells ? It sounds like prefect battery what you using it for ?

It's a round cell pack from BatterySpace.

It's very similar to the model shown below, but my battery pack says 20.4Ah while their packs now say 19.8Ah:

http://www.batteryspace.com/LiFePO4-26650-Battery-12.8V-19.8Ah-253Wh-32A-rate-w/-PCB-CU-MM173-PID.aspx

I am going to use this pack to power two 12V 18A fans to put on my bike, but I would like to have a 40-60AH pack to power four fans.

 

[dogman dan]

Why the need to overdischarge the lifepo4 battery? You should have plenty of watthours before the bms clicks off.

 

[Pure]

I don't see what the problem is running th fans off of the Life battery at it's current voltage. 1 volt over 12 volts shouldn't be an issue.

 

[dumbass]

Do what I do with my 24v packs and install a CEllLog 8 and an alarm. YOu can set the individual cells and the pack voltage for both High and low voltage. The CEllLog8 can handle up to 8 cells. And it only cost $23 + alarm from Radio Shack.

Bob

Thanks!

The CellLog 8S looks like a great device that also works on LiFe batteries. Do you think that I could just replace the BMS on my LiFe battery with a CellLog 8S to be able to run at 12V, or should I get LiPo cells to run with it?

I really like this device though, thanks for the tip:

http://www.jun-si.com/UploadFiles/CellLog_8S.pdf

Yes/no.....Remember a CEllLog8 is a monitoring device that can activate an external alarm if a problem exists. However, it does not direct protect the cells. Some will tell you you should run a BMS for lipo and lifepo4 cells. So changing cell type doesn't solve your problem. But as I've said I use my CellLog8 more or less as a BMS in the monitoring sense. And it would work for you as well.

Bob

 

[HoverBoarder]

Why the need to overdischarge the lifepo4 battery? You should have plenty of watthours before the bms clicks off.

I don't think that I was overcharging the lifepo4 battery, I basically just had a 12V fan, and when I plugged it into the liFepo4 battery, it didn't work, but when I plugged it into the Nimh, it did. It was a brand new battery, so I am guessing that it was the limitation of the BMS.

 

[HoverBoarder]

I don't see what the problem is running th fans off of the Life battery at it's current voltage. 1 volt over 12 volts shouldn't be an issue.

Perfect, just need to replace the BMS and than I should be good to go.

 

[HoverBoarder]

Do what I do with my 24v packs and install a CEllLog 8 and an alarm. YOu can set the individual cells and the pack voltage for both High and low voltage. The CEllLog8 can handle up to 8 cells. And it only cost $23 + alarm from Radio Shack.

Bob

Thanks!

The CellLog 8S looks like a great device that also works on LiFe batteries. Do you think that I could just replace the BMS on my LiFe battery with a CellLog 8S to be able to run at 12V, or should I get LiPo cells to run with it?

I really like this device though, thanks for the tip:

http://www.jun-si.com/UploadFiles/CellLog_8S.pdf

Yes/no.....Remember a CEllLog8 is a monitoring device that can activate an external alarm if a problem exists. However, it does not direct protect the cells. Some will tell you you should run a BMS for lipo and lifepo4 cells. So changing cell type doesn't solve your problem. But as I've said I use my CellLog8 more or less as a BMS in the monitoring sense. And it would work for you as well.

Bob

Thank you very much for your help!!

I think from what I have been reading, that I would definitely want a cellLog8, and a new BMS.

 

[HoverBoarder]

As a side note, does anyone know where I can get some A123 batteries?

It sounds like cellman is no longer selling them as far as I understand fromm looking through the threads...

 

[Pure]

I don't see what the problem is running th fans off of the Life battery at it's current voltage. 1 volt over 12 volts shouldn't be an issue.

Perfect, just need to replace the BMS and than I should be good to go.

Unless there is some sort of voltage inhibitor/regulator on the fan, it should run off of your LiFe. Most BM S's that I'm failure with don't give 2 hoots what is drawing power from the battery nor do they care about said devices power needs are..so long as you don't draw too much current. It should be pumping 13+ volts into that fan. Have you hooked a volt meter (dumb question I know) to that LiFe to ensure it's holding a charge? How many amps does the fan pull under load from your 12 volt batteries? Perhaps it pulls to many for the LiFe BMS (although I find that kinda hard to believe unless that fan is toast or soon to be toast)

 

[dogman dan]

I said overdischarge the battery, not overcharge.

If your bms is clicking off too soon, that's different, but I misunderstood in the first post. A proper 12v lifepo4 bms should be clicking off at right about 12v, and should be at at least 14.6v fully charged. What voltage is the bms clicking off at? It could be just clicking off for over amps too, btw.

So it does sound like a bms replacement might help. Or, discharge without the bms and monitor with a cellog or such.

 

[HoverBoarder]

I don't see what the problem is running th fans off of the Life battery at it's current voltage. 1 volt over 12 volts shouldn't be an issue.

Perfect, just need to replace the BMS and than I should be good to go.

Unless there is some sort of voltage inhibitor/regulator on the fan, it should run off of your LiFe. Most BM S's that I'm failure with don't give 2 hoots what is drawing power from the battery nor do they care about said devices power needs are..so long as you don't draw too much current. It should be pumping 13+ volts into that fan. Have you hooked a volt meter (dumb question I know) to that LiFe to ensure it's holding a charge? How many amps does the fan pull under load from your 12 volt batteries? Perhaps it pulls to many for the LiFe BMS (although I find that kinda hard to believe unless that fan is toast or soon to be toast)

I have not checked it with a volt meter....

I have A LOT to learn, and I am not sure what type of volt meter I would need

I am not sure if something like this would work:

http://www.amazon.com/gp/product/B0..._m=ATVPDKIKX0DER&pf_rd_r=0QXT8Q9M0XS8NC6ZXDVR

 

[HoverBoarder]

I said overdischarge the battery, not overcharge.

If your bms is clicking off too soon, that's different, but I misunderstood in the first post. A proper 12v lifepo4 bms should be clicking off at right about 12v, and should be at at least 14.6v fully charged. What voltage is the bms clicking off at? It could be just clicking off for over amps too, btw.

So it does sound like a bms replacement might help. Or, discharge without the bms and monitor with a cellog or such.

I am just guessing that it is clicking off at 12V, but I don't know how to check what volt it is clicking off at.

I was under the impression that I had to disconnect it from a power source before checking the voltage.

 

[dumbass]

I said overdischarge the battery, not overcharge.

If your bms is clicking off too soon, that's different, but I misunderstood in the first post. A proper 12v lifepo4 bms should be clicking off at right about 12v, and should be at at least 14.6v fully charged. What voltage is the bms clicking off at? It could be just clicking off for over amps too, btw.

So it does sound like a bms replacement might help. Or, discharge without the bms and monitor with a cellog or such.

I am just guessing that it is clicking off at 12V, but I don't know how to check what volt it is clicking off at.

I was under the impression that I had to disconnect it from a power source before checking the voltage.

I don't remember what charger you said you had. But most chargers except the higher end charges can be checked without even connecting to a battery. Just connect your meter to the charging leads and plug in the charger. What ever the voltage reading is actually will be the turn off votage on that charger. Bob