gooseF22

I wanted to know if anyone had run A123 two cell with the wren ECU yet, and if it will work. I had heard it had been done in other motors, but couldn't find any information on wren. I have a wren super sport with the 1500 lipo that came with it, but I have converted most of my other planes to A123's.

Its no big deal if it doesn't, and I wont want to violate any warranties of course.

Any of you wren smart guys out there know for sure?

If its ok, will wren also endorse it?


thanks to all.
goose

ghost_rider

My Feedback: (20)

http://www.rcuniverse.com/forum/m_70..._1/key_/tm.htm

Wren Turbines USA

My Feedback: (39)

Hi Goose,

As we discussed at the shop on Monday, the battery supplied with your new SS has passed the test of time. I have forwarded your link to Roger at Wren, and I am sure that a reply will follow.

gooseF22

Thanks for the response Ben. Thanks for forwarding Ron. Still on Plan A as discussed, just wanted to know.

dave

WrenTurbines

We have just been investigating this on behalf of the customers. We can see a couple of potential problems:

First, the A123s have only 3.3v per cell instead of the 3.7 per cell in our Lipos. This means that a 2-cell pack will only give 6.6v instead of 7.4v, so it may be sluggish when starting. You can't add an extra cell because 9.9v will be too much.

Second, the guys are concerned that at the end of the cycle there is no warning, it doesn't slow down like other batteries but just stops.

So, the official advice from Wren is that it is best to stick with the supplied LiPo. You can try the A123's but it is at your own risk.

Things may change if these batteries start to become mainstream, but at the moment we'd prefer to stay with what we have.

Sara Parish
Wren Turbines

gooseF22

Thank you Sara, just got off the phone with Ron as we discussed the same issue. Stick to the Lipo.....Thanks for the quick reply

dave

Tom Antlfinger

My Feedback: (24)

I converted my Wren SS on my Bobcat ARF from the NiMh that came with it to a Duralite Li-Mn.....7.4v/2200maH......it weighs 5.8 oz and the 1500 maH version weighs just 3.7 oz......I have been using the 4400 maH version on my Titan, Rhino, and P-180 with excellent performance and reliability on my other planes for the last year.....

I don't use LiPo's in my jets as the batts are often tucked away where I can't see them or get them out readily for charging.....

LiMn are a non-combustible chemistry much like the Li-Ion or A123......the current draw capabilities are superior to the regular Duralite Li-Ions, especially noticeable on the P-180 which really sucks the juice during startup.....

I usually go for (5) 10 minute flights on the SS before recharging and they can be recharged at 1C(2.2 amps), although to maximize pack life, I usually recharge at 1 amp through the Charge Safety module on the pack.....

Eddie P

My Feedback: (4)

The main reason I'd like to see A123 compatability is the charging issue with Lipolys and having to remove them from the jet to charge safely. Plus, they can be charged so rapidy, and they behave better, voltage wise, in cool weather conditions. I'll never go back to Nimh or Nicd, so that is not an option. Thank you for your results you posted with the Duralites. Though I have pretty much standardized entirely to A123 cells for my receivers and Jetcat ECU's, I'll look into the Duralites for the Wren. Just my opinion but I have a feeling A123's might be be mainstream pretty soon as battery replacement cycles continue.

I assume you are flying the SS with the 2200mah Duralite to get five flights, right [&:]

SinCityJets

I have spoke with Gaspar specifically about the Wren. His concern with Wren is that the starter they use will require more than 6.6v, as Sara has suggested. The problem with going to a 3 cell is it may be too high for their current kero valve.

So far, the only two engines A123's are known to work well with are the Jet Cat's with a 3 cell (GSU set to 8 cell nicad) and the Jet Central's with a 2 cell. I'm sure we will begin to see more components becomming more A123 friendly.

Bob_B

My Feedback: (11)

Eddie,
Take a serious look at the FMA CellPro Chargers. These are the best Lipoly/A123 chargers for the money.
They feature Built-in balancers and the new CellPro 10s displays the RI of each cell in the pack.

http://www.fmadirect.com/new_applica...0s_charger.htm

cactusflyer

My Feedback: (4)

OK, I have started my kit-built MW-54 MKII a couple times with a two-cell A123 pack. It seems to work fine. The start seems to take a bit longer but the temps are nominal. I haven't flown it yet because the airplane that the engine is in NEEDS the nose weight of the 4400 mah battery that is in it. I'll probably install the pack along with some lead weight and give it a flight test this week. My MKII has a noisy, starter...........48+ hours on the engine.....so I think that it is doing remarkably well on the 2-cell pack. As far as the flat discharge curve goes, I don't check my Li-Ion FADEC power packs anyway. I just fly a few times and recharge. I might try a start on the Super Sport to see how it works as well.

I think that using the 2-cell Li-Polymer is the best way to go if it is convenient to remove the pack for charging.

Tailwinds,

John

Eddie P

My Feedback: (4)

I'm using that exact charger for my A123's. Works like a champ

Bob_B

My Feedback: (11)

I have zero concern charging the packs installed in the model with the CellPro chargers.

ianober

My Feedback: (12)

What about using the A123's in 3 cell with a Reg on the Wren? You should be able to either find a 7.4 volt reg or someone could whip one together.

SinCityJets

Ian,

One of the real "pulls" foir A123's was the ability to not have to use a regulator for receiver applications. You could use one if you wanted to use A123's, but you would be "losing" one of the advantage.

cactusflyer

My Feedback: (4)

OK,

Here is an update regarding A123 usage the the Wren engines.

Yesterday, I flew my MW-54 MkII with a 2-cell A123 pack on the FADEC. I flew four 9 minute flights and utilized the auto cool down...ie; no external blower. The Hand Data Terminal showed a steady 6.6 volts during the start sequence. The starter seemed to hang at about 27K RPMs but the start temps were normal though.. This seems reasonable due to the lower pack voltage. The starter is set to run until 31K. I am going to try resetting the starter cutoff to 28K to see if the starter was slowing the acceleration during the fuel ramp stage. I did an fast charge at the field with a ThunderPower 1010 charger to check the consumption and it put in 792 mah. The cells are rated at 2300 mah. Right now, I'm cycling the pack to see what the actual capacity is with the 1010. I'm amazed at the small draw for the 4 flights. I did the recharge at 4 amps and it took 12 minutes....About the time it takes to drink a soda.

The A123 replaced a Cermark 3600 mah NiMH pack which weighs 8 oz more than the A123. This moved the CG back about 2 inches on the Boomer and it flys A LOT better! After witnessing a Cermark NiMH ECU pack catch fire and EXPLODE at the field, I have NO DESIRE WHAT SO EVER TO USE ANY MORE OF THOSE!............But that's another story altogether[]

Tailwinds,

John