BMS for thundersky batteries

[auraslip]

I'm considering thundersky batteries for my trailer project.

I was wondering what you all thought of using a signalab BMS from high tech bikes.

Is the LVC and HVC good for TS? I understand TS cells are a little different from most lifepo4.

Also what would I need to wire the bms up?

Some sort of 16 cell connector? Is there a usa supplier of those?

 

[morph999]

Or you could get 2 cellog 8s monitors and a piezo alarm from radio shack. Wire it all up and put the cell log monitors in with the battery bag or battery box and the put the piezo alarm somewhere on the bike so you can hear it. Thundersky lifepo4 is no different from most other lifepo4. Cell voltage range is 2.5v - 4.2v. I usually charge mine to 3.65v. The cell log monitors aren't going to balance your cells, though but they'll keep them safe from any low voltage or over voltage. The cell log monitors are about $15 now at hobbyking.

 

[morph999]

Piezo buzzer like this. The cell log 8s monitors come with a wire just for the buzzer so shouldn't hard to hook it up.

http://www.radioshack.com/product/index.jsp?productId=2062397

 

[dumbass]

I agree with morph (again). The most important thing is to safe guard the discharge of the cells with a LVC. the CellLog 8 can also be connected to your brake system so if you get a LV in an individual cell it will cut the power to the motor until the voltage rises. For charging both morth and a lot of other are using SLA chargers without a BMS. However, while we are doing this it's not what many people would recommend. But then again there are a lot of people that have had their BMS damage their cells. Why I couldn't tell ya. But it has happened a lot.

 

[auraslip]

Listen I appreciate the advice guys. I've read through all your post about not needing BMS with TS cells, but I've also read through you post about you having problems with your TS cells. Additionally you say your a weekend rider, and never really discharge your cells all the way.

I don't have the luxury of a car, and will be relying exclusively on my batteries. Not having a BMS is NOT and option.

I will discharge my cells to LVC. I will plug them into the charger and walk away for 8 hours.

I will do dumb things like listen to my ipod while I ride; rendering a piezo alarm useless.

I don't know why you guys are so anti-bms. The signalab unit is only $100.

 

[morph999]

the cell log 8s monitor is a bms. ok, nevermind.

 

[amberwolf]

I'm working on getting a lightly used TS 60Ah 10-cell pack to use for various things; it'll be used with a Fechter/Goodrum v2.6 BMS (as will my LiCo pack(s)).

For connectors, you can use anything that will carry the balancing current. If that's low, you could even repurpose DB-25 connectors and cables from computer equipment. If you find "extender" cables for switchboxes, they'll have all 25 wires, often plus a shield wire, and a male on one end, female on the other. Just cut the cable in half, and use the female end on your pack, and the male end on the BMS or monitoring device(s). At most, you'd have to remove nuts from one end for them to fit together. They're usually even color-coded wires. I see them at thrift stores fairly often when I look in their spaghetti piles, usually for under $5.

 

[dumbass]

Elite Power Solutions is now selling 4 packs of differnet AH cells with BMS. I don't know when they started this but I noticed it tonight. So maybe your best bet is to buy the BMS with the packs (4 cells 12v and AH as required).

http://elitepowersolutions.com/products/index.php?cPath=16&osCsid=de0f70979b741c9d8406477c08688598

 

[icecube57]

Are you talking about the balancers... its not quite a bms. Its just a balancer. It bleeds the cells down to 3.7v and only work if your charger is in the voltage range close enough to allow it to work properly. If its charging voltage is to high it wont work so well. But the cells do have a wide working voltage range. My suggestion also is if you are trying to drag these Thundersky cells in the mud on every cycle then these arent the cells for you. You are just asking for charging and balancing nightmare. 16-18ah is as far as i would discharge on a regular basis. Discharging to 19-20ah will get this cells out of wack and you will have hours upon hours of balancing and the performance is just crappy at the end of the pack.

* They sell a bms on their site. Its like a bms on steriods and probably wont be cheap.

 

[dumbass]

Are you talking about the balancers... its not quite a bms. Its just a balancer. It bleeds the cells down to 3.7v and only work if your charger is in the voltage range close enough to allow it to work properly. If its charging voltage is to high it wont work so well. But the cells do have a wide working voltage range. My suggestion also is if you are trying to drag these Thundersky cells in the mud on every cycle then these arent the cells for you. You are just asking for charging and balancing nightmare. 16-18ah is as far as i would discharge on a regular basis. Discharging to 19-20ah will get this cells out of wack and you will have hours upon hours of balancing and the performance is just crappy at the end of the pack.

* They sell a bms on their site. Its like a bms on steriods and probably wont be cheap.

your correct. I just went back and reread the info it really only a balancer not a BMS.

 

[auraslip]

Sorry I was snappy earlier morph.
I burned myself on my sodering iron just before, and it hurts to type.
Plus my cat is in heat.
I didn't mean to be rude. Just another bad day.

 

[cell_man]

I've got some BMSs in stock in 12S and 16S. The 30A constant units are very compact and reasonably priced. I've used the 12S 30A model on my bike which pulls 75A peak and a pretty constant 60A plus and no bother at all. If you need serious current I have higher rated units in stock. I've used all of the models I have and they work very well, never had a problem with them and they do not trip easily like some I have tried. Drop me a PM and I can give you some specifics.

At the price of a BMS I can't see the point in risking it for few dollars (if any saving) or the additional hassles. Unless you are pulling very high currents where a traditional BMS becomes a bit pricey, better just to stick with a BMS IMHO.

 

[jdcburg]

Gents - I just stepped up from 12 ah SLAs to a pair of Thundersky 12V 20ah packs w/o balancers. They're powering my mtb with a brushed Unite 24V 350W motor that drives the 8-speed derailleur through a shift kit. I have a 3.2 single cell charger and a digital multimeter and I have ordered a 3 amp Tenergy 8 cell LI charger. So far I have gone out a few times (4-7 miles) and haven't discharged the packs much. They are about 13.25V when I return. The cells have been within 0.06V when charged and are even closer when partially discharged. I have a few questions. What should I charge them to? The 3.2V charger turns green at 4.15V and the cells go down to 3.74 to 3.80 after resting. Is that too high? Also, how do you know how many AH you have used? Is it related to battery voltage in some easily calculated way? Thanks - jd

 

[morph999]

Gents - I just stepped up from 12 ah SLAs to a pair of Thundersky 12V 20ah packs w/o balancers. They're powering my mtb with a brushed Unite 24V 350W motor that drives the 8-speed derailleur through a shift kit. I have a 3.2 single cell charger and a digital multimeter and I have ordered a 3 amp Tenergy 8 cell LI charger. So far I have gone out a few times (4-7 miles) and haven't discharged the packs much. They are about 13.25V when I return. The cells have been within 0.06V when charged and are even closer when partially discharged. I have a few questions. What should I charge them to? The 3.2V charger turns green at 4.15V and the cells go down to 3.74 to 3.80 after resting. Is that too high? Also, how do you know how many AH you have used? Is it related to battery voltage in some easily calculated way? Thanks - jd

Don't charge them past about 3.8v . What kind of 3.2v single charger do you have? I use a Tenergy one and it charges to 3.65v. 4.2v is the maximum voltage but you don't want to get anywhere close to it on a daily basis. My Black and Decker takes the cells up to about 3.75v and then they settle down to about 3.55v . I think up to 3.8v is okay as I have been charging them up to that for the last 200 miles.

You know how many AH you've used by what the watt meter tells you. You should have some kind of cell log monitor or watt meter. If you go with a cell log 8s monitor, you won't know the AH used but you'll have the voltages. If you go with a watt meter, you'll know the AH used but not the individual cell monitors. Unless you have a cell log monitor that tracks the individual cell voltages, I wouldn't discharge more than 10AH. Once you get a cell log monitor, you can get more out of your pack but I'd still not discharge more than 80 % of the pack.

Until you get some way of monitoring them, going 7 miles should be fine as long as you are charging them after each ride.

 

[morph999]

The cell voltages are more important than AH used. You need to keep the voltages between 2.5v - 4.2v .

If you want to be safe, buy 2 of these...and you'll need also a way to hook it up to the batteries. You can find some 8s plugs on ebay I think. And then the recommendation is to buy a small piezo alarm or buzzer from radio shack or somewhere else. The celllog monitors come with a wire that is ready for an alarm to be hooked to it. You can program in the low voltage cutoff and over voltage cutoff.

http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10952&Product_Name=Cell-Log_8M_Cell_Voltage_Monitor_2-8S_Lipo

Or buy some kind of other BMS.

 

[jdcburg]

Thanks morph. I ordered a cell-log from Hobbycity. It's on backorder. I couldn't find an 8s harness but I'll keep looking. I mistyped - the single cell charger I have is a CE listed 3.7V 1.5A from BatterySpace.com, supposedly for LiFePO4 but actually it appears to be for Li-ion/polymer. I'll limit my use of that until I get the cell-log and can monitor charging voltage. Re discharge - 80% DoD would be about 2.6-2.8V/cell? Thanks for your help - jd

 

[cell_man]

Re discharge - 80% DoD would be about 2.6-2.8V/cell? Thanks for your help - jd

No doesn't work like that. Whilst you can tell something about the DOD by the no load volts after they have settled it is not a reliable method. Best way is to use a watts meter to estimate how much is still left in the tank. I don't advise running without a BMS. A 16S BMS with enough current handling for most people can be purchased for about the price of 2 Cell Log 8S.

 

[jdcburg]

A 16S BMS with enough current handling for most people can be purchased for about the price of 2 Cell Log 8S.

Where? - jd

 

[cell_man]

Well I sell them for a start For 54USD I have a nice little compact 16S BMS. It is rated 30A constant but I've used it with 65A controllers with 75A peak indicated on the CA without any trips. I have a bigger unit that is rated 80A constant for 95USD. Ecity/BMSBattery also have BMS boards and you might even save a few dollars on my price.

I can honestly say hand on heart that I have not had any problems with any of the different model controllers I've had from this supplier. Even though I've exceeded the ratings they claim, never had a failure. They're not as good as the Ggoodrum BMS but they are fine and will at least protect your battery from over charge and over discharge as well as give some protection in the vent of a fault.

BTW I do ship from China so there is a bit on top for shipping and paypal if used.

 

[jdcburg]

Thanks c_m. I'm going to use the cell-log for a while. If I think I need more help or when I start riding longer distances I'll get in touch with you - jd

 

[Doctorbass]

The Tppacks 24s+14s version i assembled for a friend work very nice with 100Ah 40s Thundersky cells.

I tested it with small 18650 A123 cells too.

here is the video:
[youtube]-yMgWl2xF2Y[/youtube]

[youtube]SwQ4OpxNrcE[/youtube]

Doc