Mac 8t with Sunthing 48V 15Ah?

[RyanT]

I've been running hk lipo for 2-3 years. In the last 2-3 weeks however I left the battery hooked up to my controller and it drained it far to low..

So, I'm in the market for a new battery. Trying to stay away from hk lipo. I looked up my controller and I have a 9 fet 30a with the mac 8t. Would Sun-thing28's 48v 15 ah battery work? It seems like it would be a little too much drain for it. The battery specs list 20 amp continuous and 30 amp peak..

http://www.ebay.com/itm/NEW-48v-15ah-LiFePO4-Battery-5A-Charger-BMS-For-Ebike-Kits-Powerful-8-Weeks-Gift-/131205444269

 

[imorton]

I'm thinking the 48v20Ah might be better, but I will let the "more knowledgeable" here reply.

 

[dnmun]

this is why i keep trying to get people to use a BMS to protect the battery. thanks for posting this up so people know it happens, and congrats too, you are one of the few who admit it, but it happens a lot.

how low is low and did you try charging them up again?

if you charge with a bulk charger initially then you can see which of the cells now has high internal resistance to charging by showing a high high voltage at the terminals of the cell, and if none of them show a huge difference in voltage as you apply the charge to the entire series then they may be able to work together again. but lower than 1V is gonna be a problem i expect. 2V really, but i know lotsa the RC guys start from this low a lot and never have the kinda problems that get blown up here.

 

[RyanT]

Humm, that's interesting they are at 2.8 v per cell for most of the packs. One bank of 4 packs has 1 cell at 1.6v. Maybe I should try to charge them. The iCharger doesn't seem happy though (no bulk charger).

 

[dnmun]

i will give you one. i have a bunch here. but the idea is to NOT use the balancing charger.

if you apply a current though all the cells in the series then the voltage across each cell would show you the internal resistance to the charging of that cell.

that is called internal resistance and is what you want to learn about. kinda like the most important thing to know.

 

[RyanT]

Ok, I usually do a bulk charge anyways I.e. I do not hook up balance wires to the iCharger. I tried to charge up a pack that was all at 2.8 and I can tell on my cell log that it stayed in balance up to 3.6(then I stopped charging). Maybe I should just bulk charge the other 4 packs that are still in balance at 2,8v and throw out the ones that had a cell at 1.x. I'm not sure how to check the internal resistance.

 

[dogman dan]

The ones above 2.8v have not been ruined yet. Don't trust the ones that went below. Maybe you can just buy one or two packs to get rolling again.

Re the sunthing pack, I would not recommend that small a pack with a 30 ah controller, But a 20 ah should work. It will sag more than lipo though, for sure.

 

[RyanT]

Yeah, looks like I am down just 1 pack since I had a couple spare ones and I was able to salvage 5 that didn't go below 2.7-2.8v. I'm going to throw the others out.

 

[dnmun]

drop them off here if you throw them out.

 

[999zip999]

If you have a C.A. I would turn the amps down to 20amps for 15ah pack and 25amps for a 20ah sunthing pack. As 30 amps is to much with amp spikes and hills ect.

 

[dnmun]

i doubt if the 2C is a problem. as i recall the sunthing pack has a 60A BMS. almost identical to the ping signalab 60A but without the leds.

 

[999zip999]

I live in a land of hills and will eat up a 48v20Ah Ping over time at 30amps. It depends on the lay of the land and length of the hills. So you want a 1000 cycle battery or 200-400cycle battery ?