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

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

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.

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.

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!

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.

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!