Paralleled Li-po Packs - Feedback Needed

[StrechM]

Who has wired together 2 li-po packs in parallel?

I have 2 smaller compartments to fit li-po packs into. Both are not large enough for 1 standard 2-2200mah pack so my thoughts are to run 2 smaller 11.1v packs in parallel.

1. What’s the best connector or connection method to use?

2. What is the best method for charging? Leave them connected in parallel or separate and charge each pack individually?

 

[sweetdiesel]

I run my 4S 4000mah packs in parallel. I made a simple Y connector with 12ga deans wire and 2 male and 1 female deans ultra connectors. Try to keep the wire runs as short as possible. Keep one male end covered when hooking up your batteries to prevent shorting. I use a female connector with shrink wrap on the exposed soldering tabs.

For quick charging you can leave them hooked up and charge through the Y connector. Every few runs I charge them individually with a balancer. If I had a second balancer, I could charge through the Y connection and balance at the same time, which would be the fastest way of charging and balancing.

When charging individually, make sure each pack is within .05 volts of each other when hooking up to the Y connector to prevent a large charge/discharge condition between them. I use my balancer to bring down the voltage of the higher voltage pack until it is within .05 volts of the other.

 

[FastEddy]

Your Mr. LiPo now arent you.
Great info Dom!
Learn that on Broke-Back when you had nothing better to do?

 

[sweetdiesel]

I used two presoldered Deans male pigtails to cut down on soldering time on the Y connector.

 

[StrechM]

I appreciate the info and picture sweetdiesel.
.05v is tight. Doesn't leave much room for error. It also makes me want to invest in another balancer and the new li-mn packs. I'll have to build pigtails with approximately 3/4" of ultra wire. Maybe I should put the bandaids on my fingers before soldering instead of having to afterwards

Here's the victim. Its got BPP's Wraith in it now (not in pic) and I think there is a way to mount two 3s packs and rest of the gear to lower deck with no room to spare. The real tricky part is the work around the drive belt. If not the rx or esc will have to sit up top.

Thanks again!

 

[sweetdiesel]

I forget how little room you have to spare on the 1/18 scale cars. What are the dimensions of the battery that is sitting in the car right now?

 

[StrechM]

Zero right now but the one in the picture is approx. 100 x 35 x 18 mm and a 2s. I've been looking at TP and Apogee but leaning towards li-mn but have not had time to finnish the research yet. I need 3s, its a current whore.

Whats up?

 

[sweetdiesel]

Maxxamps carries a 3S 20C 2100mah pack that is 34x98x20mm. Can you spare another 2mm in thickness between the upper and lower deck? Or were you thinking more along the lines of mounting two small packs on each side of the chassis and running the electronics in the middle?

 

[StrechM]

I reconfigured the battery with a 1320mah TP. It ran ok but was grossly underpowered. It needs 3s, 20c.

The one in the picture is a 2s 2100 Maxxamps. There is no additional room between the upper and lower decks for another 2mm. It requires spacers in the old configuration for the pack to clear the belt above the lower deck.

The only way that I can see to add 2000 or more mah is to split it up with 2 1000 to 1300mah packs. I can mount them on both sides or side by side across like the in photos.

Here are some pictures taken by the gentleman I traded with to give you a better idea of what I'm working with.

 

[sweetdiesel]

If the reason why you need 2000+ mah is to increase the available amps from a 15C pack, would getting a pack with a higher C rating meet your requirements? Flightpower has a 1200mah pack but is rated at 25C/40C max. The dimensions are thinner than the TP 1320 pack by 4mm (assuming the TP pack is 20mm thick). You can draw 30amps continuous on the FP packs versus 20 amps with the TP pack.

http://www.espritmodel.com/index.asp?PageAction=VIEWPROD&ProdID=5090

But back to your original post about running dual packs...Two of these packs would give slightly better punch and longer runtime than the single FP pack above.

http://www.espritmodel.com/index.asp?PageAction=VIEWPROD&ProdID=5089

Dimensions are 77mm x 34mm x 14mm and rated at 20C/40C. Judging by the length and width of your receiver, these packs would fit right in between the two chassis braces and might stick out slightly outside of the chassis.

 

[StrechM]

The chassis is 4.125" (104.7mm) width at the center.

The runtime won't be long but this one may work.;

FP1200 3S (11.1V)
Rating: 25/40C Norm/Max Discharge
Output: 11.1V Nominal, 1200mAh
Dimensions/wt: 4" x 1 1/4" x 5/8", 3.7 oz.
103mm x 32mm x 16mm, 105g

The rx and esc can be placed about anywhere. I have Hitec HFS-03MM's or DCX rx's, the esc's are Castle's so there's not much weight there.

The chassis was designed to take 6 - 4/5 Sub-C batteries and a 540 can but that is a lot of weight to control at more than 50 mph.

I've opted for the Wraith with lipos to reduce weight.
With a 1500ma 20c 3s lipo and correct gears should = 300+ watts which should be somewhere in the neigborhood of 1.75 times the output from the Castle/Tekin 8000kv. 7-8 times that of a speed 300 with 6 cells and much more torque than either produce.

I'll dig out the calipers to see how much more room there is.