Cheap battery meter

[butterbean]

Because I am installing a generator as part of a charging circuit to charge a 12v battery and don't want to overcharge my battery, I wanted a battery meter to tell me when my battery is fully charged so that I can disengage my generator to avoid overcharging. The generator is connected to a charger with a rectifier and regulator, but I don't know if the charger has overcharge protection built-in or not. I looked at a few motorcycle battery gauges, but they were way out of my price range. I found this one on Amazon for $10: http://www.amazon.com/gp/product/B00825NB24?ie=UTF8&force-full-site=1&ref_=aw_bottom_links but its not designed for a motorcycle (i.e doesnt come with a handlebar mount), its actually designed to snap into a panel on a boat dashboard. You can see from the pics in the link, it doesn't even have a back. So what I did was I took an old tail light that I no longer use and gutted it to hold the battery meter. Its a rectangular tail light, the type that you use a coin or flathead screwdriver to pry the cover off to change the batteries. I removed the cover and the led light strip, as well as the switch that controlled the light. I thought the wires might fit through the hole left by the switch, but I ended up having to make the hole a little bigger before the meter would sit level inside the tail light housing. The wires were getting pinched between the wire connector and the back of the tail light housing. Once I had made enough room for the wires and the meter was sitting level, I grabbed some quiksteel epoxy and epoxied the meter into the tail light housing. To be clear, the cover of the tail light is removed so that it doesn't interfere with the meter and the meter can be read clearly. After the epoxy cured (I used quiksteel because its what I had, left over from a gas tank repair), I wrapped electric tape around where the epoxy was to ensure the unit would be waterproof. I tried to take some pics, but the camera on my tablet sucks. Sorry. Anyway, I now have a battery meter that can be mounted to my handlebars (the tail light was the type that mounts on the seatpost, but I'll use the clamp to clamp it to handlebars instead). Actually, since I'm connecting it to my power terminal, it will tell me the voltage of the battery as well as the voltage from the charger, so I will always know that my charging circuit is working properly. When the battery voltage reads full (my generator is tire driven, so when I stop, only the battery voltage will be displayed) I can disengage my generator from the tire, only needing to engage the generator when the battery voltage drops enough to need charged again. Its a 12v battery, so I figure when it drops to around 10v or 10.5v its time to engage the generator again. Maybe 11v, just to be on the safe side. I'm also planning to install a rocker switch to turn the battery "off" (spst rocker switch, wired inline between the battery positive and the power terminal) so that the battery meter isn't constantly on, only when I need it to be. The battery meter draws very little current, but I don't see the sense in letting it run constantly. The switch will actually cut off the entire electrical system from the battery, but I see that as a good thing. It prevents anyone from being a smart aleck and turning my lights on when the bike is parked. I'm not planning to install the meter until the rocker switch gets here (sick bike parts, just ordered it a few minutes ago), so it will be a couple days. I'm installing the generator tomorrow after work, so I'll have to check the battery every time I ride with my digital multimeter until the switch gets here. Sorry for the long, rambling post. Anyway, thats a cheap diy battery meter solution for anyone who needs it.

 

[bigoilbob]

I wouldn't install another gauge to fix on, instead of the road. If you are worried about overcharging, change out your current charger for this one. http://www.amazon.com/Kintrex-SPC0601-Controller-Digital-Display/dp/B001HWQZNQ. I have been using it for 18 months or so and maybe 2000 miles, with a 12 volt, 5-6 amp alternator, and a $3 Radio Shack bridge circuit. I check battery volts ever month or so - always 12.15 +/- 0.01 volts. And that's with repeated ~10-20 second discharges at 30-60 watts followed by similar charging (unique to my build - long story), and the shaking of the ride, into and out of a very small lead acid motorcycle battery. So, I think it's an ok product.

And of course if yours is truly a DC generator, no need for the bridge circuit and it's ~0.7 volt loss.

 

[bigoilbob]

Apologies butterbean - my carelessness. The product I touted is unavailable there and might be hard to find at all. But I think, generically, I would take a chance on any similar, correctly sized (for your loads and generator), light, cheap, durable, solar power controller. I am sure they are out there. FYI, mine is in a fairly poorly ventilated box and has worked fine in lots of stop and go riding (more work for the controller), in 95 degree heat. This type of product is meant to work in the weather and with the shaking of wind turbines.

Repeating, why compromise safety by fixing on an extraneous gauge? If you are worried about overcharging, take your Radio Shack gauge with you on a ride. Check voltage after 2 minutes, then 10 minutes, then 30 minutes, and so on...... When you arrive at your comfort zone start worrying about something else.

 

[butterbean]

The battery gauge is not extraneous. The pictures in the link probably make it look bigger than it is. Its actually 1.75" x 1". It fit inside a tail light housing, so that should tell you how big it is. Its not going to be in the way of anything on my handlebars, so no safety concerns. I simply prefer to have the gauge to tell me what is going on at all times. I already spent the money to buy this meter and did the work to fit it into a housing to mount it on my handlebars, so I'm going to install it. Disengaging the generator (not dc by the way, the charger I am using has a rectifier to convert it) when the battery is fully charged will also help the generator last longer, and thats part of the point as well. Having a gauge on the bike means one less thing to pull out of my toolbox or carry with me every day.

 

[bigoilbob]

2 each his own. I did not view it as "in the way of anything", but just as an avoidable way of keeping your eyes off the road more. I would rely on your charging circuit to "disengage the generator". Is that what U meant? Also, the process I described of repeated checks at lengthening intervals was only to give you confidence that your charger was operating ok. It was proposed as a 1 time deal.
No one I know, or read about, carries a volt meter around routinely, and I do not recall discussion of handle bar mounted volt meters on other bikes. (Forum, set me straight FIM wrong). My 650 Dakar does just fine with only a low volt idiot light.

Again, don't want to fight and even if I'm right it's no big deal......

 

[butterbean]

Well its common sense to keep your eyes on the road and not stare at your handlebars. I do fine keeping my eyes on the road using a smartphone for a speedometer, so having a battery gauge is no different. Just because no one else uses a battery gauge doesn't mean its not a good idea. Scooters have charge meters, I'd imagine some motorcycles do as well. What I meant by disengaging the generator was cocking it away from the tire. Its a bottle generator connected to a mini-charger with a rectifier and a regulator and I dont know if it has overcharge protection built-in or not. The bottle generator can be cocked away from the tire when its use is not needed. I thought about maybe using a switch to cut off the charging circuit, but I dont know if it would be ok for the generator to be producing voltage and have it not go anywhere. My last generator got fried from having too small of a drive wheel (the plastic one it came with got chewed up and I replaced it with a seatpost clamp bolt, way too small). The generator spun too fast, overheated and grenaded inside. I'm using a much larger drive wheel this time, a 2" r/c car tire, and it will produce rpm's in the generator comparable to those of a standard size drive wheel at pedal speeds, which these tire-driven generators were designed for. So when my battery gauge reads full, I can pull over when I'm able to do so safely and cock the generator away from the tire. Only engaging the generator when a charge is needed will help it last much longer, and having a battery gauge on the bike will let me know exactly when my battery is fully charged, and when it needs a charge. The fact that I'm the first person to think to use a battery gauge on a motor assisted bike makes me feel pretty proud of myself, as well as creative. The way I designed the battery gauge to fit on the handlebars also makes me feel pretty creative. So I like the idea I had, I like the way I implemented it, and I like how much money I saved with a diy solution, so I'm going to run with it. I checked out a couple motorcycle battery gauges, and they were $40 and up. Mine only cost me $10 and a little of my spare time. I consider myself an innovative person. Be a naysayer and insist you're right and then pretend you don't want to argue all you want. I personally feel that these types of debates lead to deeper understanding, and there really is no right or wrong. You do what works for you, I'll do what works for me. Have a good day.

 

[bigoilbob]

Sorry to have riled U up, butterbean. If UR proud of yourself 4 thinking of something no other MB rider ever bothered with, then IM proud of U2.

But (1) gauge fixation is hit on time and time again as an accident causer at CHP motorcycle training (at least mine and my daughter's), and (2) among those MB riders who THINK they have great road awareness, some do, some are fooling themselves. Don't know U. U might be God's own safe rider - even watching your smartphone riding down the road. I certainly hope so....

 

[butterbean]

As I said before, you do what works for you, I'll do what works for me. Have a good day, buddy.

 

[butterbean]

Ok, so since the only reason for the battery gauge is to know when my battery is charged, it doesn't need to be on all the time. I ordered a rocker switch from sick bike parts, and I was originally going to wire it to the battery, but I think I will just wire it to the battery gauge instead. This way, I can turn the battery gauge off when I don't need to see the voltage. I have a 6 mile round trip to work each day, and my battery charged about 0.5v going to and from work today. This was without running my headlight at all, just my brake light. If I run my headlight all the time, my battery shouldn't ever overcharge. But I'll wait until the battery is fully charged to start doing that. That will probably be about 5 days unless I wall-charge it before then, which I could.

 

[butterbean]

Well, I got the rocker switch from sick bike parts today and wired it up to the battery gauge. The switch is intended as a killswitch and would normally short out a circuit by connecting the positive and negative, but if you wire two positive or two negative wires to it, it completes the circuit instead of shorting it out. Of course, the on/off positions are now reversed, but that's not a big deal. I am now able to control the battery gauge so I don't have to fix on it while driving.