Recommendation for LIPO pack for BBS02, 13S or 14S

[gridlok]

Building my first Lipo pack for a BBS02 750W trail machine. Currently lugging my 22 lb LiFe 20Ah battery in a backpack which gives me 3+ hrs of riding but I want to build something much smaller and mount it to the frame of the bike. I'm very interested in the Multistar

http://www.hobbyking.com/hobbyking/store/__1387__85__Batteries_Accessories-MultiStar.html

Trying to decide whether to build a 13SP1 (3x3 & 1x4) or 14SP1 (3x2 & 2x4) pack. I don't want to use a BMS and would rather have the low voltage cutout on the BBS02 controller save my pack. 12S seems like the voltage levels would be too low to get the most power out of the pack before the Low voltage cuts in. I think the low voltage setting is 41v from the factory, but I don't know because I haven't programmed mine. This is the only screenshot I can find for the BBS02 settings

http://endless-sphere.com/forums/viewtopic.php?f=28&t=58780&p=901524&hilit=+bbs02+lvc+factory+default#p896424

Also interested in opinions on the best inexpensive charger I can get that will balance charge all 4 packs at once (I don't want to bulk charge)

I'm thinking of getting this one

http://www.hobbyking.com/hobbyking/store/__10327__HobbyKing_8482_Quattro_4x6S_Lithium_Polymer_Multi_Charger.html

You guys are the experts. Looking for the safest configuration (not killing batteries from overdraining) to get without having to reprogram the BBS02 with different lvc or having to use a BMS.

Karl

 

[snowranger]

You will need to reprogram the controller. 41 volts is too low for 13s.

The charger linked only puts out 50 watts. That will take forever to charge. Try something like a hyperion 1420 or similar that puts out about 500 watts up to 14s, but you will need a good power supply at 26 volts or so.

 

[tln]

I'm no expert, but I'm interested in hearing answers from them on this... I have BBS02 + 12S, would like to know if I'm "leaving capacity on the table"

If the LVC is 41V that would be 3.41v at 12S... That's not as deep as the batteries can be discharged, but deeper than I probably want to for everyday use (advice I've seen says preferably no lower than 3.5 to 3.6V for best life). You want to be able to discharge more deeply than that regularly?

 

[dnmun]

I'm no expert, but I'm interested in hearing answers from them on this... I have BBS02 + 12S, would like to know if I'm "leaving capacity on the table"

If the LVC is 41V that would be 3.41v at 12S... That's not as deep as the batteries can be discharged, but deeper than I probably want to for everyday use (advice I've seen says preferably no lower than 3.5 to 3.6V for best life). You want to be able to discharge more deeply than that regularly?

you do not seem to recognize that the voltage sags rapidly below 3.5 V under load so having 3 V/cell for the LVC is totally normal and reasonable since the cell will rebound to above the 3.6 V resting level when the load is removed.

 

[tln]

Ah, good point, thanks

 

[snowranger]

3 volts at cell level is reasonable but not 12 X 3 Volts for the whole pack. The cell voltages diverge when the battery empties. That plummeting cell will be masked by the averages of the other cells if you use pack level protection at that level.

 

[gridlok]

So what I'm hearing is that 41v is a decent cutoff for a 12S pack, but not a 13S or higher pack.

I guess I'll spring for 3x4Cell batteries and make it a 12S cell. Thanks for the input.

Karl

 

[dnmun]

using the controller LVC for protecting the battery from over discharge is kinda primitive imo. i find it no problem to build a pack by removing the shrink wrap and putting the pouches in compression and protect it with a BMS. eliminate the risk of damaging the pouches and protection from short circuits on the output. plus high rate charging using a bulk charger.

 

[teslanv]

I would go with a 12S Pack, and max out the LVC on the controller, which I believe can go as high as 42V.

For the record, 12S is very respectable power wise, and if your gearing is adequate, the BBS02 will climb hills like a billy goat.

You may want to get a chainring adapter and throw on a 34-38T Front chainring for the best hill climbing power, especially if you don't need to go fast.
I also highly recommend installing a simple watt meter on your bike, so you know what you are using.

http://www.amazon.com/High-Precisio...1414379648&sr=8-1&keywords=GT+power+wattmeter

 

[gridlok]

I already burned out the mosfets on the controller, so I'm waiting for upgraded ones to come in from Digikey to solder them in.

I ordered 2 chainring adapters from Australia, the 48 is way to big. I also got a 36 cog for the rear. I'm thinking 34/36 in the front and 36 in the rear should give me a lot of pedaling torque on a 26.

I'll get the watt meter, I also got a temp sensor to install when repotting in the BBS02 controller.

I would go with a BMS if I could find a cheap one somewhere that was easy to install.

Thanks again for the input.

Karl

 

[KINNINVIEKID]

I use a pair of Multistar 16Ah batteries on my BBS02 and have installed a £6 wattmeter so I can see when my batteries are getting down at a glance.
http://www.ebay.co.uk/itm/121454683866?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I have a 46T chainwheel and an 11-30T freewheel and it climbs great.
Going too undergeared could result in inadvertant wheelies on steep hills if you hit the throttle (done it on mine on a 20% hill)