SMC Factory Spec Lipos
02-08-2016, 09:02 AM
#1
SMC Factory Spec Lipos
Hi guys,
Long time member here, but I don't usually frequent this battery forum. Just wondering if anyone else here has had experience with SMC Lipos? Last year my buddy and I bought a couple of their "Factory Spec" packs since they were decently priced, used fat wires, great construction, were 2200mah "bigger", and they already had Traxxas plugs installed. At first they were awesome. 7200mah 60C was a step up from the Gens Ace 5000mah 50C packs we'd been running. We noticed better mid-range "punch" and were getting close to 30min run times.
But after 6mo, they were starting to swell, and I noticed the run time was significantly reduced. One pack I only get 10min out of it. Turns out that one of the cells is weaker than the other. Once it drops below storage voltage, that cell rapidly looses voltage compared to the other one. Consequently, the LVC kicks in sooner because it's seeing the total voltage.
This is really disappointing because they were so good at first. Now, our 2 year old Gens Ace packs are better than the SMCs. We've been very happy with Gens Ace packs. Just wish they'd come out with some 6000- or 7000mah packs. Or is 5000mah pretty much the limit that the technology allows?
Long time member here, but I don't usually frequent this battery forum. Just wondering if anyone else here has had experience with SMC Lipos? Last year my buddy and I bought a couple of their "Factory Spec" packs since they were decently priced, used fat wires, great construction, were 2200mah "bigger", and they already had Traxxas plugs installed. At first they were awesome. 7200mah 60C was a step up from the Gens Ace 5000mah 50C packs we'd been running. We noticed better mid-range "punch" and were getting close to 30min run times.
But after 6mo, they were starting to swell, and I noticed the run time was significantly reduced. One pack I only get 10min out of it. Turns out that one of the cells is weaker than the other. Once it drops below storage voltage, that cell rapidly looses voltage compared to the other one. Consequently, the LVC kicks in sooner because it's seeing the total voltage.
This is really disappointing because they were so good at first. Now, our 2 year old Gens Ace packs are better than the SMCs. We've been very happy with Gens Ace packs. Just wish they'd come out with some 6000- or 7000mah packs. Or is 5000mah pretty much the limit that the technology allows?
02-28-2016, 09:35 AM
#2
I emailed SMC:
Hi SMC,
About a year ago, I bought two of your 7200mah 2S Factory Spec Lipos. I was really impressed with the construction, and pleased I could buy them with Traxxas plugs installed (my preferred connector). Initially, the performance was impressive. I noticed a significant mid-range punch, and was getting 25min run times. But soon I noticed the packs were swelling. A certain amount of expansion is expected. But these guys are REALLY swelling, and starting to split the case. Not only that, the run times were WAY down. I discovered that both packs, one in particular, had one weak cell. One that would drop its voltage much quicker than the other. So while one cell was only down to 3.80V, the weak cell was already down to 3.50V. No wonder my run times were down. And this on batteries that are less than a year old? I've got Gens Ace packs that are 2-3 years old that now out-perform the SMC packs! What the hey?? I thought you guys tested cells and matched them up better than that. 8^/ I'm very disappointed. Unless you can give me a good reason, I don't think I'll be buying anymore Lipos from SMC. Too bad. I'd LIKE to support a US company.
Their reply:
Hi Rob, What's the part number on the packs you purchased ?
What are you using them in ? What's your cutoff set at ?
We do test packs and make sure the packs we sell are quality packs. When it comes to Lipos the way they are used and treated will determine cycle life and how well they hold up. We have certain customers who get 300+ cycles out of a pack and others who may only get 100 as the vehicle it's used in and how it's being used will impact cycle life.
Regards,
Danny Sullivan
My reply:
Hi Danny,
The pack part number is 7260-2S2P. I also noticed that next to the part number is a Watt-Hour rating of 53.28wh. That does work out to 7200mah. (53.28 x 1000/7.4 = 7200)
I run them in a 4wd short course truck, running a 120Amp ESC and a Novak Ballistic motor. LVC cut off is set at 3.4V. I ALWAYS balance charge my Lipos, and I storage charge them right after I'm done.
Problem is, the cells in both packs have become un-balanced. One cell drops below 3.5V while the other is still at 3.80V. That shouldn't happen with packs that have been very well cared for. The cells are obviously mismatched, or, one cell is defective. None of my other packs have done this, and they're twice as old and have many more cycles on them. That is why my run time has been cut in half, one cell is weak and drops off the cliff.
Rob
His reply:
Hi Rob, The 4wd SC class is very hard on packs as the truck is very heavy and uses a powerful motor. The cells are well matched but over the cycle life cells don't drop off at the same level. This class should be run on 3S or 4S packs and not 2S but ROAR doesn't seem to understand this. Unfortunately there is nothing I can do for packs that have been used for awhile that are dropping off specially in the 4wd SC class. You can try packs from another supplier and see if they will hold up better. One thing I recommend is for you to check the voltages of the cells when the LVC cuts in. Ideally you want them to be now lower than 3.60v. This will improve cycle life if you don't discharge them to low under load.
Regards,
Danny
Sorry Danny, not buying it. I've been using Gens Ace 2S packs in the exact same way, in the same truck, for twice as long as the SMC packs, and they have not puffed, and the cells stay in perfect balance all the way down to the 3.4V cutoff. These SMC packs haven't seen more than 90 cycles. (We keep track of these things)
Doesn't exactly fill me with confidence. Too bad.
Rob
I won't be buying any more SMC packs.
Hi SMC,
About a year ago, I bought two of your 7200mah 2S Factory Spec Lipos. I was really impressed with the construction, and pleased I could buy them with Traxxas plugs installed (my preferred connector). Initially, the performance was impressive. I noticed a significant mid-range punch, and was getting 25min run times. But soon I noticed the packs were swelling. A certain amount of expansion is expected. But these guys are REALLY swelling, and starting to split the case. Not only that, the run times were WAY down. I discovered that both packs, one in particular, had one weak cell. One that would drop its voltage much quicker than the other. So while one cell was only down to 3.80V, the weak cell was already down to 3.50V. No wonder my run times were down. And this on batteries that are less than a year old? I've got Gens Ace packs that are 2-3 years old that now out-perform the SMC packs! What the hey?? I thought you guys tested cells and matched them up better than that. 8^/ I'm very disappointed. Unless you can give me a good reason, I don't think I'll be buying anymore Lipos from SMC. Too bad. I'd LIKE to support a US company.
Their reply:
Hi Rob, What's the part number on the packs you purchased ?
What are you using them in ? What's your cutoff set at ?
We do test packs and make sure the packs we sell are quality packs. When it comes to Lipos the way they are used and treated will determine cycle life and how well they hold up. We have certain customers who get 300+ cycles out of a pack and others who may only get 100 as the vehicle it's used in and how it's being used will impact cycle life.
Regards,
Danny Sullivan
My reply:
Hi Danny,
The pack part number is 7260-2S2P. I also noticed that next to the part number is a Watt-Hour rating of 53.28wh. That does work out to 7200mah. (53.28 x 1000/7.4 = 7200)
I run them in a 4wd short course truck, running a 120Amp ESC and a Novak Ballistic motor. LVC cut off is set at 3.4V. I ALWAYS balance charge my Lipos, and I storage charge them right after I'm done.
Problem is, the cells in both packs have become un-balanced. One cell drops below 3.5V while the other is still at 3.80V. That shouldn't happen with packs that have been very well cared for. The cells are obviously mismatched, or, one cell is defective. None of my other packs have done this, and they're twice as old and have many more cycles on them. That is why my run time has been cut in half, one cell is weak and drops off the cliff.
Rob
His reply:
Hi Rob, The 4wd SC class is very hard on packs as the truck is very heavy and uses a powerful motor. The cells are well matched but over the cycle life cells don't drop off at the same level. This class should be run on 3S or 4S packs and not 2S but ROAR doesn't seem to understand this. Unfortunately there is nothing I can do for packs that have been used for awhile that are dropping off specially in the 4wd SC class. You can try packs from another supplier and see if they will hold up better. One thing I recommend is for you to check the voltages of the cells when the LVC cuts in. Ideally you want them to be now lower than 3.60v. This will improve cycle life if you don't discharge them to low under load.
Regards,
Danny
Sorry Danny, not buying it. I've been using Gens Ace 2S packs in the exact same way, in the same truck, for twice as long as the SMC packs, and they have not puffed, and the cells stay in perfect balance all the way down to the 3.4V cutoff. These SMC packs haven't seen more than 90 cycles. (We keep track of these things)
Doesn't exactly fill me with confidence. Too bad.
Rob
I won't be buying any more SMC packs.
