Battery type

[Captain Andy]

I've been using an old NiCad cordless drill battery for testing purposes but it's a few years old and doesn't last for more than a few minutes. What kind of battery would you recommend. Lipos? NiMh?  My motor draws about 2 amps and I need something between 8-12 volts. Ideally they should weigh about 500 grams which will exclude lead acids.

Here's a link to my supplier: http://www.sussex-model-centre.co.uk/shopdisplaycategories.asp?id=27&cat=Batteries+and+Lipos

[Talisman]

Hi Andy,
Welcome to the forum.
Regarding the batteries, Personally i use NiMH batteries and don't have the experience to comment on LiPo.

This company do NiMH batteries in 4300mah at a weight of 66g per cell so it is slightly over your 500gram mark but they could be assembled to ballast the boat well. They also have a 5000mah cells so you could sail for several hours happily on them if you can take the weight.

Personally, for paddlers I'm not a big fan of lead acid batteries.
Regards,
Kim

http://www.ebay.co.uk/itm/4300mAh-SubC-SC-NiMH-rechargeable-cell-solder-tags-/230551622621?pt=UK_ToysGames_RadioControlled_JN&hash=item35adf293dd

[Captain Andy]

Thanks Kim,NiMH it is then.  I think I can manage ok with 8 cells (9.6v) so that would save weight (and money!) , if I need 10 my boat would probably take a little more ballast. The motor is off set to one side and the 500 gram battery balances perfectly next to it.so I might need to shift one cell over to the motor side. Half an hour to an hour's running time would probably be plenty enough.

[Captain Andy]

Have found a new looking 8 cell Li-Ion laptop battery in the recycling bin at work, all cells are at a healthy 3.8 volts! I understand that you can charge these using a LiPO charger so not having to buy cells brings the total cost down from approx £50-60 to £20! Must be worth a try! Don't worry I'll only ever charge them outside.

[Captain Andy]

After reading this http://www.rcgroups.com/forums/showthread.php?t=209187it makes Lipos l (and therefore I take it LiIons look like incendiary bombs, even if I only charge them outside I don't want them catching fire in my boat... or my car! No wonder airlines are so wary of laptops!

[marinemole]

Andy

The big difference between Lipos and Lions is that the former catch fire and the latter EXPLODE. This is because Lions are encased in a thin metal casing.

Many years ago I had an accident with a first generation 2s 1200maH Li-Ion fitted with a small BEC type plug which I always struggled to grip and disconnect. After testing an installation I removed the battery and laid it aside. On smelling burning I checked the battery to find it intensely hot and the pins bare and touching. I had obviously pulled on the wires and not the socket and pulled the pins from the mounting. I immediately separated the cause of the short . As I pondered my next move I noticed the end start to glow and was then almost deafed by a violent explosion which left my ears ringing for half an hour. These Li-Ions were encased in thin metal with open ends and the effect was that of a shotgun cartridge. To cut a long story short I ended up with a very expensive insurance claim for scorch marks on a carpet due to the shower of intensely hot filmy debris ejected from the open end but very fortunately escaped injury in spite of debris hitting my face.

[Captain Andy]

OK thanks for that warning it's all starting to sound way too risky! Money is paramount at the moment bcz my job ends at the end of this month and I haven't  as yet found a new one so i think I'll take my boat out for a sail on the charge I have in those Lions I have  and get some photos and video then wait until I can afford a set of NiMH!