| Lead Acid,UV-18 & UV-26 | Nickel Metal Hydride (N-19, UV-N-37) | Lithium Polymer (Magnus) |
| At end of dive, lead acid batteries gradually become
slower, allowing
the diver to safely return to the shore of boat if the burntime has
been slightly exceeded. | NiMH batteries will cut-off suddenly at as soon as they
have been fully
discharged, possibly leaving the diver stranded. At best, the diver
will always have to make the dive shorter than necessary, to ensure the
scooter does not completley shut off requiring the scooter to be towed
or swum back to shore. | Can
have a hard cut-off, or if used with a Electronic Speed Control (ESC)
can have a soft power down mode, making it perform similar to lead acid. (Magnus has soft power down) |
| Lead
acid batteries are a very mature technology, having proven
characteristics of reliability and low cost. This chemistry should long
outlast NiMH batteries. | NiMH batteries are a relativley
new technology, hence they are more expensive. Also, they may be
obselete in less than 10 years, replaced by lithium chemistries. | Most expensive, with the shortest track record, but with promising specifications. |
| The
high quality Genesis batteries have 200 to 500 cycles (standard quality
lead acid may not perform well after 50 to 100 cycles in a deep
discharge device, such as a scooter) | NiMH batteries
specify 500 or more cycles. however, this is unproven in underwater
scooters. Realistically, don't expect more than 3 years service life
out of any battery chemistry. | At least as good as lead acid; better than NiMH. |
| Lead acid batteries are double the weight of similar
capacity NiMH batteries. | NiMH batteries are lighter than lead acid batteries | Lithium Polymer batteries are the lightest batteries currently available. |
| Geneis lead acid batteries recover well from over
discharge, if re-charged as soon as possible. | NiMH battereis can suffer from "cell reversal" when
charged
as a pack, if the individual cell voltage is allowed to drop lower than
1 volt per cell. This is quite possible as NiMH batteries have a high
rate of self-discharge, meaning they will comtinue to discharge even
after the low voltage protection ciruit has prevented active discharge. | Electronics protect cells. |
| Lead acid batteries are really easy to charge, and have
an
exremely low rate of self discharge. Only problem with charging is if
ambient tempertature is less than about 5 degrees Celcius. | NiMH have as much as 10% self discharge on the first
day
after charge. The higher the temperature, the higher the self
discharge. Unfortunately, the batteries heat up during charging,
especially at the end of charge, so you loose a noticable amount of
capacity during the first few hours after charging. | Almost zero self discharge. Do not loose capacity from lack of use. No need to cycle to maintain performance. |
| Lead Acid
batteries perform and charge better the
higher the temperature (up to a temperature of about 55 degrees Celcius) | Nickel
Metal batteries are extremely difficult to
charge to full rated capacity if the ambient tempertature is high. | Avoid high temperatures. Easy to charge. |
| Legal for passenger aircraft | Legal for passenger aircraft. | NOT legal for passenger aircraft. |
