I recently bought some light accessories to add to my motorcycle in order to increase visibility and safety. I was planning to have a motorcycle shop install them, I usually am willing to DIY things myself but when it comes to anything electric I will pay a professional as I don't think it's worth the risk for me. After being quoted installation prices double what I paid for the products, I am now considering doing the installation myself.

I want to understand the risks involved, if possible death is on the table, then I won't take the chance. My understanding is that the risk is relatively low but I would like to ask this community to be sure.

According to the specifications in my owner's manual, my motorcycle's electric system is 12V and the battery is listed as a VRLA (Valve Regulated Lead Acid) 12 V, 6.0 Ah (10 HR). The installation will require cutting and stripping wires to add in some light modules and also using Posi-Tap connectors to tap into other wires.

So far my understanding is I will want to turn off the motorcycle then disconnect the negative lead to the battery and THEN the positive lead and then later connect them in the reverse order.

  1. Is this all I need to do to remove my risk of electrical shock (removal of leads)?
  2. What other risks exist?
  3. I am also gathering that 12V isn't enough voltage to push the amps through the body, is my understanding true?
  4. My understanding is capacitors can still hold a charge after an electrical source has been cut, do capacitors exist on vehicles such as motorcycles?

Please let me know if any other details are required and thank you in advance for any help and advice!

  • 3
    \$\begingroup\$ You are fine. Voltage isn't high enough to be dangerous here unless it's the spark plug. Just don't short the battery. \$\endgroup\$
    – DKNguyen
    Aug 25 at 4:03
  • 1
    \$\begingroup\$ If you short the battery, you will get a big spark, but you won't get electrocuted. Just do the work and learn from your mistakes if you make any. It will be fun, and you will be more confident after. \$\endgroup\$
    – mkeith
    Aug 25 at 4:28
  • \$\begingroup\$ Death risk utterly minimal except from fire. Shorting battery to ground/chassis via: switch can destroy switch. Via wiring can cause fire or melted wiring || Some modern electronics may but survive reverse polarity. | Be sure what you should do, be sure you do what you should, be tidy, insulate exposed joins and connections. Money saved is exceeded by experience and knowledge gained - well worth while. \$\endgroup\$
    – Russell McMahon
    Aug 25 at 6:57
  • 1
    \$\begingroup\$ As you disconnect battery leads, wrap some insulation round the ends and tape them to stop them flopping around. Just to be on the safe side. \$\endgroup\$ Aug 25 at 12:07

12V is not a shock hazard - nothing on a motorcycle, other than the ignition coil, generates enough voltage to cause you harm from electrocution.

Shorting the battery could potentially cause a fire, so it’s wise to disconnect it while you’re working on your wiring harness, if only to prevent damage to your wiring.

The biggest danger in motorcycle wiring is that, done wrong, it can fail and leave you stranded.

With this in mind, best realign your thinking about the task - away from the 'risks' you mention and focus more on the reliability of the modifications you intend to make.

The main considerations with motorcycle wiring are vibration, abrasion, weather, heat, and adequate circuit capacity.

As you do your work, think about these:

  • Get a wiring diagram for your motorcycle.
  • Make sure that your add-ons don’t overload the circuit they’re being added to. This goes double for a small bike, which probably has a wimpy charging system to begin with.
  • Make sure your wiring is secured against vibration, doesn’t rub or bind against anything, and that all your connections are weather-tight.
  • Avoid solder connections. If vibration doesn't kill them, corrosion will. I don't care what the links say, shrink tube and solder are not the way to go on anything exposed to vibration and weather.
  • Crimp is ok (and even preferred) for splices and connectors. Look for connectors that seal against moisture, there are heat-shrink sleeved ones that work nicely.
  • Motorcycles concentrate heat in surprising places (like under the subframe, gas tank, etc.), especially when not moving forward. This can melt electrical tape and other materials. Plan accordingly. (this tape stuff looks ok)

Specifically, I don't consider the Posi-Tap connectors you're considering to be weather-tight. They're also large, making them prone to vibration. These will not do well on a motorcycle. Consider a different option.

This might be helpful: https://advrider.com/f/threads/your-favorite-sealed-water-proof-electrical-connector.1318695/

And this: https://motorcyclemd.com/motorcycle-wiring-best-tips-and-tricks/

And this: https://www.motorcycle.com/how-to/mo-wrenching-how-to-properly-splice-wires (though I don't recommend solder - use barrel crimp that heat-shrinks instead.)

Deutsch connectors seem very robust. Worth a look: https://www.webbikeworld.com/deutsch-connectors-motorcycles/


Is this all I need to do to remove my risk of electrical shock (removal of leads)?

Removing the battery leads in the way you propose, and setting the battery aside where it cannot be accidentally short-circuited, is a suitable way of disconnecting the circuit to de-energize it. Be sure not to accidentally run the engine, as that can generate electricity (used to recharge the battery in normal operation) through the alternator.

What other risks exist?

However, a major risk in these 12 V systems for vehicles is the massive currents that can flow if the battery is shorted -- for example a spanner/wrench that accidentally touches both terminals of a car battery can allow massive currents, which can cause severe burns if you touch that wrench. While the circuit is disconnected, be mindful of the battery and its terminals. Don't wear metal jewelry.

The battery could also be mechanically damaged if dropped or struck/punctured, which could lead to a release of chemicals. The same could occur if you tipped it over and its seal was broken.

As long as your circuit design has proper circuit protection with fuses, you don't have an undue risk of causing a short circuit upon a correct, careful reconnection. It would be helpful to get the light module design peer-reviewed and ensure that your posi-tap connectors won't create a risk of short circuit. Getting familiar with the use of multimeter for continuity testing and resistance measurements will also be helpful here.

I am also gathering that 12V isn't enough voltage to push the amps through the body, is my understanding true?

12 V is generally not enough to push amperes through your body through unbroken, dry skin. Deliberately applying 12 V to broken skin can be potentially dangerous depending on how low of a resistance is left.

Capacitors exist in many different circuits, and motorcycles almost certainly have them. In their most common use, they will only have 12 V across them at most (meaning that they won't be able to shock you). For a motorcycle, I would have concerns about the spark plug circuit which may have a capacitor holding high voltage. Be sure not to run the engine while working on it, and if you have a disconnect for the ignition system (e.g. a fuse or similar), disconnect it.

  • \$\begingroup\$ Thank you very much for your answer, it was very informative! When you say "It would be helpful to get the light module design peer-reviewed", is that something this community would do? I have the wiring diagrams and installation guides for each light accessory that the company provides \$\endgroup\$
    – User9123
    Aug 25 at 4:24
  • \$\begingroup\$ @User9123 I'm not 100% sure as it depends on how detailed the schematics are. Asking a question that mentions your specific concerns (like you did here) and includes the relevant diagrams will be helpful. If they're from a reputable company and have a fuse or other protective element, there's a good chance that it'll be fine, but I can never write "definitely" in an answer like that. \$\endgroup\$
    – nanofarad
    Aug 25 at 13:56

I cannot miss this one.
First of all, your question will be removed in no time, because it is not of a StackExchange question, but of the bike gangs. I am one of them, though. And, I did that all LED bike, too. :-).

Is this all I need to do to remove my risk of electrical shock (removal of leads)?

Yes, the reason is that (-) is connected to everywhere (chassis ground). I forgot the exact reason, but once I remove (+) first and caused spark while removing (-). And, though no one told me, I learned that.

What other risks exist?

I don't see any other risks from the battery. May be yo can wrap the battery terminals with tape, just for in case.

I just recalled; I got the spark when I was removing the screw on (+) first, accidentally my flex wrench handle touched the chassis and shorted the battery, sparked. Chassis (and '-') is everywhere wile working on (+), and more chance to short, while (+) is only on the terminal.

I am also gathering that 12V isn't enough voltage to push the amps through the body, is my understanding true?

That is not true. You can go with whatever voltage with your lights, but anything connects to the existing bike switches or regulators, never go over 12V. The parts are designed to use 12V. You never push voltage (more properly say; current) through the body (chassis). That will cause fire someday. Instead, you need to make the wires have good contact to the METAL chassis. Plastics are tolerant to electric force.

If you meant body of human, DC 12V is not enough to "push through" energy. Energy (not the 5 hours boost thing) comes from the current, and your body supposed to be above 100k ohm and up to a few Meg ohm on your fingers, thus the current is about 100uA at the max, while you get million times larger energy from static zap. But, if you'd like to volunteer, you can put your tung on the battery (try with 9V first) and get good adrenaline running. Though, I have not heard someone suicide using a 12V battery.

My understanding is capacitors can still hold a charge after an electrical source has been cut, do capacitors exist on vehicles such as motorcycles?

Yes, motorcycles have any sort of capacitors, usually. But, it is small CAPACITY, not going to kill even an ant.

If you draw too much power from the battery, battery can drain when the engine not running, if the lights are on. And, then you would attempt to put bigger battery, and kill the alternator. The worst is the lights suck the power while the motor is idling, then you will see the lights dimming, and the motor dies. So, you need to moderate. Meantime, LED lights use less power, and if you are replacing the "incandescent" lights, you may install many more lights. Whatever you do, make it sure the lights are more and brighter, not less or dimmer. I almost ran over by a big truck at a red light on one dark rainy night, with "minimalist style" led lights on my bobbed bike. Anyway, bikers die while riding, but never while working on lights and battery.

  • \$\begingroup\$ Thank you for your answer. All 3 addons are LED systems, how can I know if I am adding too much for a battery to handle? Is there a way to know if certain light systems are going to be drawing too much power from the battery? Will these LED accessories be drawing power when the engine is off? These are all universal fit type light systems from CustomDynamics and Denali \$\endgroup\$
    – User9123
    Aug 25 at 4:22
  • \$\begingroup\$ I would say you wouldn't overload the battery or alternator by just replacing the existing lights to LED system from "legit" manufactures, and say universal fit for bikes. Meantime, the box usually contain some sort of instructions and cautions. If that LED was super high power, then that paper may tell it. Another way is measuring current before and after the lights replacement. You need some tricks to do that, and that may not be trivial. \$\endgroup\$
    – jay
    Aug 25 at 4:33
  • \$\begingroup\$ I would just replace the lights, and see if the bike bogs down with al the lights on. My good guess is that you will be fine. \$\endgroup\$
    – jay
    Aug 25 at 4:35
  • \$\begingroup\$ While the lights are off, lights (either olden ones or LED) do not draw any power. So, cut the light switch, and you are ok. \$\endgroup\$
    – jay
    Aug 25 at 4:38
  • 1
    \$\begingroup\$ Aha.. I see. It sounds like those are not going to use much power. Yah,, just install and see if it works. Not gonna hurt too much. \$\endgroup\$
    – jay
    Aug 25 at 4:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.