Onboard Battery

[MichaelJ2K]

Recently I purchased a 7.2 volt, 1650ma NiMH 6 cell pack from Radical RC to run my radio. After 8 races and 3 hours of steady use, the pack still had plenty of power left. It's for the Multiplex transmitter and worth the $22. It's also lighter in weight compared to a 6 cell ni-cad. All you have to do is add your own connector.
http://radicalrc.secure-mall.com/shop/? ... art=412090

[PegLeg]

Mike

Why so much voltage??

I use a 5 cell (6v) pack rated at 4400 Mah in a Wheeler with 2 winches and 2 servos. My EC uses a 5 cell 2700 Mah pack for 1 winch and 2 servos.

Neither of these arrangements have run out of power after a full day of non stop sailing (6-->8 hrs).

I have the packs made up at the local Interstate battery shop. They are reasonably priced ($32 & $27), available in 2 hours or less and can be configured in any size or shape immaginable.

With the increasing use of cell phones and other battery powered gadgets there are several interstate type of stores popping up all over. [}:)]

[kahle67]

I think Mike said it was for his transmitter but I have never seen one that operates on less than 9.6v. I take it the cells are considerably smaller in size as 1650 mah is rather low for what is available these days (in AA size) but why worry about weight savings in a transmitter?



Reichard Kahle
Charleston, SC

[MichaelJ2K]

Let me be a little more specific. I bought the pack to run the 7.2V Whirlwind drum winch, receiver and servos. I was previously using 1000ma 6 cell nicads and was changing the pack after three or four races. The NiMH pack is lighter weight than the nicads and I no longer have to hassle with extra packs. I've not checked the MA draw of the Whirlwind but I know that with this winch, it is possible to run out of battery power after an extended duration. Sorry about the confusion.[:D]

[bigfoot55]

I am updating an old boat, and it seems that 6v nimh is the popular way to go with an RMG. I have an old Super Cycle (1976) which was for 4.8 Rx/9.6 Rx battery. Checked it out and it works. It outputs 6.8 on the Rx side. Can I use it to charge 6v pack- or convert it? I understand nimh do not need to be cycled, but still have nicad for the transmitter. Would anyone recommend using nicad for the boat anymore?

Tom P

[Skip Quinn]

Hi Tom
I am sure their are some skippers out still using nicads. I purchased a 9.6 nimh (2000mah) for my transmitter from batteryspace.com. I think the cost was $12.?? plus shipping and I have gone 2 days of sailing with no charge. I also use the old wall charger with no problem. Good sailing.

[yachtie]

Battery updates:

Reading the attached article says go and buy some real quick

http://www.rchobbies.org/lithium_batter ... hrough.htm

Helicopter guys are using them so they must be pretty good when you consider the big power usage they need.
Some of the key points are:

2 cells in series = 7.4 volts

Wiring two LiPo cells in parallel doubles the capacity (more run time), plus an important advantage of wiring in parallel is that each cell only sees half the total current

To charge a fully depleted pack typically takes about one and a half hours

LiPos don't develop memory or voltage depression characteristics like Ni-Cds. Do charge them without the worry of cycling or discharging them

Don't: Fully discharge your LiPo battery pack.

They are not the cheapest but hell they sure sound good when you read up on them - because of the no memory effect recharges are when you want and the larger capacity ones - 4000mah 2 cell are around $100USD but only weigh 180gms. Physical size is 125mm x 50mm x 20mm so may not fit most IOM's but the 12 ain't a problem!

Smaller packs are - 1320mah 60 x30 x12 mm and weigh a staggering 58 gms!!!!!!!!! These can discharge at a whopping 17A avergae with peak of 26A which can handle an RMG fine. These are around $35 USD so say 70 bucks landed for us kiwis. Pretty reasonable.

Next time the nicads start dropping off these will be on the shopping list

Please Note:
*****WARNING***** Charging Lithium Polymer batteries with incorrect charger WILL CAUSE FIRE, AND EXPLOSION. Please make sure your charger supports charging Lithium Polymer batteries. If you do not have an appropriate charger, please order one


Chris
NZL1 Longtack
NZL110 Swept Away NZL128 Ketch me if U Can

[kermwood]

I justed looked at web site and the warning about house fires being caused,and to quote..
"store and charge only in a fireproof container"
"watch over the charging process and never leave alone on charge"
On my wish list ?
l don,t think so !!!
Woody

[Les Ervin]

Why would a person be worried about battery weight with a boat? Doesn't it just become part of the ballast when it is installed?

[greerdr]

I hear Lipo's and water are a BAD mix!

R.C.Greer

[kahle67]

In the EC-12 you are right, it does not really matter. Some that were involved in this discussion sail other classes where it does. 2000 mah or better nimh are all that you need and can be found anywhere.

Reichard Kahle
Charleston, SC

[E Artz]

Lipos and water are indeed a bad mix. However, I do run lipos in my EC-12. I can't say that the few more ounces that the Nimh weigh would make that much difference in a 24 pound boat. The main reason I went with Lipos was that I fly electric airplanes as well and already had the charger. I just make sure they are wrapped in a plastic bag or condom. If they short out, they will catch fire. You do have to be careful with them. You can't abuse them during charging and discharging. Be careful.

Earl

[Jim Linville]

I've been using Lithium batteries in my US1Ms for some time now. First thing I did was to drop a cell in a glass of water and let it sit overnight: no fire, no explosion, no problem, cell still works. Cant say you will get the same results, but they work for me. --Jim Linville