Trickle Charge from External Battery

Ballardst · March 12th, 2017, 12:40 PM

I street park in a city and have nowhere to plug in my battery. But, I sometimes go awhile between rides.

Is it possible to charge up a lithium jump starter, extra motorcycle battery, or other in my apartment, and then plug that into my SAE haves downstairs to trickle charge my bike from that? Would it be as simple as plugging it in our would I need some additional wiring/fuses/whatever to make it work?

Thanks.

EDIT: Sae Harness

Triple Jim · March 12th, 2017, 01:15 PM

Quote:

Originally Posted by Ballardst

Is it possible to charge up a lithium jump starter, extra motorcycle battery, or other in my apartment, and then plug that into my SAE haves downstairs to trickle charge my bike from that? Would it be as simple as plugging it in our would I need some additional wiring/fuses/whatever to make it work?

Not sure what an "SAE haves" is, but trickle charging takes a regulated power supply or "smart charger" to avoid overcharging. I don't know if one exists that is made to be powered from a battery. If not, you'd be designing your own.

I think your best bet would be a small solar charger that is inconspicuous so it's not attractive to thieves. I put a 4 amp solar panel on the roof of my Dodge van a few years ago, and built a charge controller for it, and it's really nice to not have to be concerned about the battery running down if I dont' drive it for a month. Something for a motorcycle could be pretty small.

Searching for "motorcycle solar batttery charger" turns up tons of results. Look for one with a charge controller so it doesn't overcharge the battery.

Ballardst · March 12th, 2017, 01:30 PM

That was a typo, I just changed it to SAE harness. The "pigtails" permanently attached to my battery, but that are probably too thin to jump start through.

I'd love a solar charger, but it would just get stolen if I left it on the bike all the time.

I figured a full motorcycle battery equivalent to the one in my bike couldn't overcharge it - it would just charge the more dead one until they reached an equilibrium. I'd feel more confident if someone could confirm that, though.

Triple Jim · March 12th, 2017, 02:59 PM

You need about 13.8 volts to maintain a lead-acid battery. Terminal voltage at rest is around 12.5, so a fully charged battery won't charge one that's not fully charged very well. That's why I said you'd need to buy or make a charger made for the purpose. It would need a DC-DC converter in it to get the voltage up, and then a charge controller to properly charge the motorcycle battery.

You might be better off modifying the battery box and cables to make them quick-connect, and just take the battery inside when you want to charge it. Anderson Powerpole connectors rated for 100 amps or so would be suitable to put a 2-pole plug on the battery + and ground so you could just unplug it when needed.

Ballardst · March 12th, 2017, 09:07 PM

OK. I'd only need to charge it up enough to start once. On a semi-related note, do you know what voltage the battery needs to drop down past where the bike will have trouble starting?

Mohawk · March 13th, 2017, 04:19 AM

If you are thinking of using a secondary battery, then just get a Lithium based one. They hold their charge much longer & provide better cranking amps. I can leave mine for over a month & it starts right up. If you do want to do a second battery, then a Lithium based one that can fit under the seat one a short heavy duty extension harness should do the job of starting the bike.

March 12th, 2017, 12:40 PM	#1
Ballardst ninjette.org member Name: J Location: Washington, dc Join Date: Aug 2016 Motorcycle(s): '08 Ninja 250 Posts: 18	Trickle Charge from External Battery I street park in a city and have nowhere to plug in my battery. But, I sometimes go awhile between rides. Is it possible to charge up a lithium jump starter, extra motorcycle battery, or other in my apartment, and then plug that into my SAE haves downstairs to trickle charge my bike from that? Would it be as simple as plugging it in our would I need some additional wiring/fuses/whatever to make it work? Thanks. EDIT: Sae Harness

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March 12th, 2017, 01:30 PM	#3
Ballardst ninjette.org member Name: J Location: Washington, dc Join Date: Aug 2016 Motorcycle(s): '08 Ninja 250 Posts: 18	That was a typo, I just changed it to SAE harness. The "pigtails" permanently attached to my battery, but that are probably too thin to jump start through. I'd love a solar charger, but it would just get stolen if I left it on the bike all the time. I figured a full motorcycle battery equivalent to the one in my bike couldn't overcharge it - it would just charge the more dead one until they reached an equilibrium. I'd feel more confident if someone could confirm that, though.

March 12th, 2017, 02:59 PM	#4
Triple Jim Guy Who Enjoys Riding Name: Jim Location: North Carolina Join Date: Jul 2016 Motorcycle(s): Ninja 250 Posts: A lot. MOTM - Oct '18, Aug '17, Aug '16	You need about 13.8 volts to maintain a lead-acid battery. Terminal voltage at rest is around 12.5, so a fully charged battery won't charge one that's not fully charged very well. That's why I said you'd need to buy or make a charger made for the purpose. It would need a DC-DC converter in it to get the voltage up, and then a charge controller to properly charge the motorcycle battery. You might be better off modifying the battery box and cables to make them quick-connect, and just take the battery inside when you want to charge it. Anderson Powerpole connectors rated for 100 amps or so would be suitable to put a 2-pole plug on the battery + and ground so you could just unplug it when needed.

March 12th, 2017, 09:07 PM	#5
Ballardst ninjette.org member Name: J Location: Washington, dc Join Date: Aug 2016 Motorcycle(s): '08 Ninja 250 Posts: 18	OK. I'd only need to charge it up enough to start once. On a semi-related note, do you know what voltage the battery needs to drop down past where the bike will have trouble starting?

March 13th, 2017, 04:19 AM	#6
Mohawk ninjette.org guru Name: Chris Location: Bristol, UK Join Date: Feb 2016 Motorcycle(s): ZZR250, VFR800 Posts: 478	If you are thinking of using a secondary battery, then just get a Lithium based one. They hold their charge much longer & provide better cranking amps. I can leave mine for over a month & it starts right up. If you do want to do a second battery, then a Lithium based one that can fit under the seat one a short heavy duty extension harness should do the job of starting the bike.