Every now and then I’ll stupidly let my motorcycle battery die. This means I have to take the battery off the bike, haul it up to my apartment, trickle charge it, then reinstall it in the bike. I’ve often wished I had a second battery that I could use to jump-start the bike.
Well, as I was doing some housecleaning, I found an unused 12v battery (sealed, lead-acid) that came with an old burglar alarm system. Hmm, I thought, maybe this could come in handy toward solving my battery woes. But, before I do anything stupid I thought I’d ask a few questions of any electrical engineers or battery gurus out there:
The alarm battery is about 15 years old, but it has virtually never been used. Would it still hold a charge?
The alarm battery is rated at 12v / 7.0Ah My motorcycle battery is rated at 12v / 12Ah. Would my jump-start scheme even work?
How do I charge the alarm battery? Would my trickle charger do the trick? (No, the alarm system is not installed, so I can’t use that.)
Again, no. The burgler alarm battery (probably a lantern battery, like this) does not provide enough amps to turn over the motor.
Again, gotta say no. The trickle charger is rated for the higher amp motorcycle battery. Using it on the battery not designed to hold as much of a charge could have VERY BAD results. As in, it could explode.
I’m going to say **maybe **. The battery shown in the link is not designed to be recharged, and will most likely explode if you tried. A rechargeable battery needs to vent hydrogen to the atmosphere, and lead-acid batteries do that. So do NiCad and LiON.
A trickle charge is the minimum amount of current you can pass through a battery and still charge it. The idea behind trickle charging is that you can leave the battery on the charger an indefinite (and unattended) time. Provided you have two batteries of the same architecture, say lead-acid, but of different ampere ratings, the charger designed for the higher battery will trickle charge the smaller one just fine, because the battery itself provides the ultimate load on the circuit.
All bets are off if you have batteries of different types. That said, there are battery chargers on the market that can accomodate differing architectures, but not at the same time.
Depends on the battery, but probably not (especially since yours is probably deader than a doornail).
You need to know how many cranking amps the battery can supply. The amp-hour rating tells you how much total “juice” the battery can supply, but it doesn’t say how quickly it can squeeze it out. The amp-hour rating is determined by how much lead and how much acid you have, but the cranking amps is determined by how much surface area there is on the lead. You can make the lead plates skinny and long, which has lots of surface area, which will give you more cranking amps over a shorter amount of time, or you can make the lead plates short and fat, which gives you less cranking amps, but you can crank for a longer period of time. Alarm systems typically don’t need to put out a high amount of current, so they may be the equivalent of “deep cycle” batteries, meaning that they have short fat plates inside. It will make your alarm beep longer, but won’t give you so many amps to crank over a motorcyle engine.
If lead-acid batteries get discharged too much (like when they’ve been sitting for say 15 years) the battery cells self destruct chemically. No amount of charging will bring them back. If the battery wasn’t quite so dead then your trickle charger would probably work.
To add a little information, this might not be the type of battery stuyguy is interested in. It might be more like the batteries here. In fact, there is a 12V/7Ah battery shown on the right side colum of that page.
Not that that changes the answer at all, but, since I had to search heaven and hell for a replacement for my alarm about 2 years ago (finally ordered it on-line and paid more for shipping than the batery cost), I felt qualified to shed some light on the subject.
15 yrs is pretty darn old for a lead acid battery, but yes you could easially jumpstart it if it were new assuming your battery can still accept the charge. Simply hook it up to the dead battery, wait a bit, perhaps as small as 10 seconds or so, maybe longer, and the good battery will charge the dead battery, so when you crank it you will be getting both batteries supplying power.
Trickle charge as I understand it, is the charge rate a battery can withstand if left on contionusly, and differs depending on the battery.
Watch out - people might **jump ** all over you for a pun like that!
Even if your old alarm battery were new, it probably can’t source enough amps in one blast to start the bike. It’s meant for steady and relatively low-draw applications like keeping an alarm or telephone system running.
A new SLA battery like this one might have the guts to source one or two starts, but there’s a fair chance that the internal plates would warp from the heat generated, or the internal connection from the plates to the terminals might melt and then it would be toast.
What WILL work in this case is a couple of RC car NiCAD packs in series (7.2V x 2 = 14.4V). NiCads have extreamly low internal resistance.
This is, however, fairly hard on your bikes alternator. Not the starting, but the running afterward. Forcing your alternator to charge a deeply discharged battery is hard on it, and many motorcycle alternators are margional under the best of circumstances.
Not exactly what was asked, but be aware there is a type of combined charger/battery/jumper-cable set you can buy for something like $35-$50 US. It’s about the size of a hardcover dictionary. You leave it pluged in, then take it to whatever vehicle has the dead battery. It’ll start a car, so a 12V motorcycle shouldn’t be a problem. Very handy. The local gas station keeps one around for loan - much simpler than using jumper cables between two vehicles (especially if the ‘dead’ one is in a difficult location)
