Replacement for 12v NiCad battery for a motorcycle (gas)

[KevXR]

Hi,

I have a gas powered motorcycle that uses a small 12v rechargeable NiCad battery to power the tail light, signals, and stop light if the engine is turned off. The battery is constantly being charged while the engine is on.

Are there other battery types, such as NiMh that would be safe to use? A battery fire on a motorcycle would be a bad thing. Or is there a circuit I can add to keep the battery from over charging? Fully discharging is something that happens on occasion.

Thank you,
Kevin

 

[Stevesie]

Has the existing battery failed? Are you hoping to improve on the existing battery in some way? Does the existing battery have any information on it? I.e Ah rating, brand or model? There is a good chance a Nimh can go in there. If you have an multimeter/amp meter handy it would be useful to find out the charge rate. Cheers.

 

[KevXR]

Hi,
I have had two battery packs wear out. Nicad 1000Mah packs made of 10 1.2 AA batteries.

The original battery pack.
http://www.bajadesigns.com/ProductDetail?ItemNumber=120315

Alternative
http://www.rockymountainatvmc.com/p/44/54/227/1156/-/26640/Tusk-Enduro-Lighting-Kit-Replacement-Battery-Pack/nicad+battery

Safety is number one. Cost and having the packs last longer would be nice, so I am looking into other battery formats, like NiMh.

 

[deardancer3]

You MIGHT be charging at too high a rate for the small batteries, which would cause over heating the pack and decreasing its life time.

to do this correctly, one would need to know the load current range minimum to maximum and the supply voltage minimum to maximum.

Its Life would be simplier if you changed the lights to LEDs, decreasing load and decreasing load range min to max.

how long do you need the light to run if engine off?

If you only need 20 minutes of lighting, the engine normally runs for over 20 minutes, and the Lights (LED) only draw total 100Millamps, this is easy. but with regular bulbs I doubt this is the case.

If you change bulbs, turn signals can be a bit tricky due to the flasher circuit.

d

 

[dnmun]

do you current ly have the 12V nicad charger? is there one bad cell you could just replace? i have some nicad cell if you need to replace a few and go on your way without throwing away more money on nimh.

 

[KevXR]

My main question is how safe are Minh batteries? I have ruled out LiPo after reading about stories of them catching on fire.

 

[Hillhater]

My main question is how safe are Minh batteries? I have ruled out LiPo after reading about stories of them catching on fire.

FYI.. I have had NiCad's burst into flames before now !!
Any battery can be "dangerous" if not charged, discharged, or maintained correctly.
NiMh is as safe as any other. ( Most packs will have a "Thermal cutout" installed to protect from overheating)
( Minh ???? )

 

[dnmun]

(Minh) are the new vietnamese manufactured nicads.

 

[Stevesie]

Yep I think there is a good chance the batteries are cooking due to an inappropriate charge rate or more likely and specifically, over charging because of design comprimises. You really need to measure the voltage and current when the pack is almost fully discharged, and when fully charged to see what is going on and how to fix it. This is the safest thing to do, rather than relying on the chemistry being non-venting-with-flame.

 

[amberwolf]

My main question is how safe are Minh batteries? I have ruled out LiPo after reading about stories of them catching on fire.

Every chemistry has had fire incidents, including explosions if the outgassing is too tightly constrained.

How does your MC charge the NiCd? Does it just put alternator voltage across the pack, or does it have an actual charger taht cuts off based on delta-V and delta-T, as well as protecting against overtemperature?

if the former, that's probably why packs are failing.

If the latter, then it might just be heat from environment or engine causing premature aging, or outgassing of electrolyte (which leaves the cell with less capacity each time this happens), or poor quality cells, or simply cells taht are too small for the load they see.

FWIW, typically you would want 12 cells in series, not 10, for a "12V" system in the automotive world, because it is not usually actualy 12V, it's usually more than that, up to 14.4V or more. To verify this for your own vehicle, start it up and turn on the lights, then check the voltage at the lights--it is probably higher than 12V.

 

[Stevesie]

Yes the best "lazy" option here is probably just to add one or two cells in the series string to reduce the overcharge that is probably occurring, and maybe use some larger cells if the charge rate is too high. A 12 cell cordless drill pack might be worth trying, or get a custom pack made by one of the online vendors.