mrfixitwhite

Can i ask what would be the best option for my boat
im new to electrics... err and boats!
i want to power a boat but im not after a speed boat
im not even sure on motor sizes yet(but thats probably a different post!)probably a 400 -500 size
im after a good run time rather than breaking the water speed record and wondered what options i have for batterys
i was looking at a 6 cell 7.2 pack either ni-cd or ni-mh but not sure on the difference between the 2
then someone suggested lead acid as its a boat(fairly large 25-30" long)
ive seen some lead acid 6v batterys but what difference does the amps make?
i.e a 6v 1.3 amp lasts lets say 1 hr ish
would a 6v 7amp last 5hrs ish
or doesnt it work like that?

many thanks for any advice

Graham

bigB

what difference does the amps make?
i.e a 6v 1.3 amp lasts lets say 1 hr ish
would a 6v 7amp last 5hrs ish
or doesnt it work like that?

Yes, the more amp hours a battery has, the longer it will last. A 7 amp battery should keep it running for a long time. As to whether a lead acid battery is appropriate for a boat, I have no idea as I have no experience with boats.

ernest2

lead acid usually provide plenty of run time. like you said, more ah = more runtime. the only downside is that its a bit heavy. but if its a scale boat, it should be ok. also there is a big difference as sealed lead acid are mostly 6v and nicd or nimh packs are mostly 7.2v.

cowana

A lead acid battery that is 7ah will last one hour if 7 amps are used. Or 2 hours if 3.5 amps are needed.

Lead acid batterys are not capable of outputting a lot of power - eg the one I have infront of me is 68 Watts. This means that the maximum output it can give is 68 Watts. To calculate Watts, you need voltage * Current. As the voltage is 12V, the current is 5.6A.

This means my Lead acid battery can give out 5.6Amps max.

Ni-cads have MUCH shorter run times - eg a 1700mah (milliamps) will last only 14 mins (i think) with a 7 amp current draw. But, Ni-cads can give out huge amounts of current - over 20 Amps, so this is good in a speed boat. Lead acid batterys are heavy and slow, but good for scale boats.

Jimmbbo

Lead acid and NiCd batteries also differ in how they discharge over time. The voltage of a lead acid battery decreases linearly over time, while a NiCd will retain a fairly high, constant voltage then drop rapidly at the end of the discharge cycle.