ElectricMotorcycleForum.com
Makes And Models => Zero Motorcycles Forum | 2013+ => Topic started by: Jepe on December 26, 2025, 12:50:24 PM
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Hello.
A question about a 2025 SR/S: I understood that the 12v battery is charged from the main battery when the bike is in use, but when I charge the main battery without turning the key on contact first, will the 12v battery also be charged at the same time, or only when you turn the key on (for example, to unplug the cord from the bike at the end of a charge)?
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Whenever the 12v lines are active this means the DC-DC converter is also active. That is the thing that charges the 12v battery.
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So, let’s say I charge the bike till 55 %, and when the charge is finished, I put it on contact, disconnect the plug, set the chargegoal to 60 % for the next charge, and turn of the key.
The next time I connect the plug, so, without turning on the key, the main battery is charged but the 12 v is not?
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I believe that is the case yes. Annoying because the 12V battery doesn't last all that long on its own - make sure to turn the key on for an hour every couple of weeks.
Cas :)
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but wouldn't it also charge every time you rode the bike too, sipping off the main battery?
aaron
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Yes. As MVetter said, whenever the 12V lines are active, the DC-DC converter is converting main battery voltage to 12V and charging the 12V battery. If the dash is on, the 12V lines are active.
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but wouldn't it also charge every time you rode the bike too, sipping off the main battery?
aaron
Yes, that’s right, but the reason I asked is my situation in winter, when there’s frost and salt on the road. I don’t ride the bike in these conditions, so my plan was to put in the garage after “the last ride” and charge it till 55%, and after 3 or 4 weeks till 60%, a few weeks later till 65%, etc, in that manner I can span two or three months. That’s why I wondered if the 12v was charged too in this way, but it doesn’t seem te be the case.
Strange that you have to leave the bike with the contact on for an hour or so to keep the 12v in good health, I guess I’m still in the “internal combustion”-mood, where you cannot leave the contact on for such a long time without damaging the circuit ;) .
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So besides the bikes electronics periodically checking on the main batteries health, what else is sucking off the 12 volt bus when it is off? unless it's got a bunch of parasitic loads, or just a cheap shit battery, probably the case with oem batteries, or very old, a normal 12v sli/sla should handle that without too much of a pain.
get yourself one of these 2amp battery tenders, plug it into the battery direct, you should have fairly decent access to it, and keep it topped off that way. it's probably lead acid, they are cheap and fairly reliable, BUT don't like to sit partially charged. keeping them topped off on a trickle constantly, they love it, unlike lith, which hates it. this way when spring rolls around, you top off your lith, which DOES like to sit around 80 percent, and your LA, which loves to float at 100 percent, are both good to go.
aaron
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Yeah, there's nothing wrong with getting yourself a separate battery tender, ideally one designed for lithium batteries that doesn't bring it up to full and keep it there. Also, something else to consider for winter, this is the time of year when people load up the accessory port lines with things like heated gear. The DC-DC is only a 300W unit, and the 12v battery is there to sort of bolster it. The point is if you're pulling 300+ Watts during winter riding the 12v battery is actually being discharged and can't refill itself until the load on the 12v lines is reduced.
I'm not saying you're doing that, I'm just pointing out additional complications during times of cold weather riding.
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From what Morgan said, 300 watts, that's running your lights, accessories, abs pumps, sensors, bikes brain, heated hand grips etc, those watts go fast, there really are not a hell of a lot left for you to go plugging in a lot of extra toys. You may be saying, well my heated suit only takes 180 watts, gloves and all.. but if your bike is already pulling 200 watts just to run. you are already running a deficit on the battery. Now lets throw in the cold weather that's making you have to wear all that stuff. That can be killing your battery 30 percent of it's capacity, so now those loads are really taking their toll.
A lead acid battery sitting a day or two, at less than full charge, can start sulfating, (losing capacity permanently), so no matter how it's being used, having a trickle charger for a lead acid battery to keep it topped, is really a good idea.
Aaron
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It's also funny because Zero started out with a 300W unit but bumped it up to a 500W unit in 2015 when they added ABS which required extra power. Then, when the gen 3 bikes were designed with the 12v battery as an additional power bank they opted to save a couple bucks and drop back down to the more cost-effective but weaker 300W unit. The units are functionally identical, so I would consider seeing if you can find a scrapped gen 2 Zero and scavenging a 500W Sevcon DC-DC then putting that in your gen 3 bike.
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Thanks for all the answers regarding the 12 volts battery. Now that I’m reading reactions about lead acid batteries I’m prepared to read advices about changing the cooling fluid on my SR/S soon too :D .
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fluids should be changed at least annually imo.
brake fluids pick up moisture, which reduces it's effectiveness and can cause corrosion, pitting, and very undesirable results during a hard stop. Changing it once a year is also a great time to check your brakes for leaks, cracked covers, seals leaking, how much pad is left etc etc.
your fork oil picks up dust and grime from the roads you ride on, can break down, it's viscosity changes and it does not perform well. the ports can get plugged causing further loss of performance. a quick flush / inspection there can give you early warning of issues creeping up on you.
anti freeze / cooling fluids, likewise can pick up contamination that reduces their effectiveness. changing it, and seeing it's condition can give you an indication of your engines health, do you have any leaks starting, head gasket issues etc. excessive corrosion and so on? in our case, inverter motor wear but same principles. also it lets you check for leaks, running out of that will cook your stuff in very short order.
oils in gear boxes can pick up moisture, metal shavings etc which can give you grief, cause foaming, reduce effectiveness. inspecting this lets you check for abnormal wear, indicating potential misalignments or bearing wear. this is something you absolutely want to catch early on before it gives up the ghost. the type of metal you do find, if any is a very good indication of which component is having issues.
so yes, it's your life, your safety, i honestly can't recommend doing this once a year highly enough. if you can't, don't know how, don't have the time, etc, then have someone else do it for you, but this is stuff you really shouldn't be neglecting.
just my thoughts.
Aaron
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For someone that assumes everything is AI that has to be one of the most AI responses I've seen from you ::) Talking about headgasket leaks and gearbox fluid when it comes to a Zero.
Come to think of it are there any fluids in the gen 3 bikes other than brake fluid? Of course the battery, motor, controller are all air cooled but I thought the chargers still were as well.
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im giving him the general reason to change the fluids on any bike annually. given he is asking if he should bother changing the fluids or not, it seems he is new to bikes, so i am explaining to him, yes you do need to change them, inspect them and why, not just saying yes and walking away.
the energca has gearbox oil that you change, it's not much but you change it, it also has fluid for the inverter, again not much, that's about a cup or two i think in there. the brakes you should always check because the fluid gets shitty especially if you use them hard. same goes for the forks. my point being you should change your fluids annually because you also should be taking a good look at your bike at least annually too, don't just ride it until shit starts falling off, it's not a harley. this is something that should be done with every bike, not just electrics. some people have gas bikes too, and if you have problems it can show up when you start getting antifreeze / oil where they don't belong or mixed. just like with a car.
aaron
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I'm pretty sure that was satire
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Come to think of it are there any fluids in the gen 3 bikes other than brake fluid? Of course the battery, motor, controller are all air cooled but I thought the chargers still were as well.
From the top of my head, on top of the brake fluid, there is oil the forks and damper.
I've never understand why dampers are generally not serviceable item (without expensive special equipment). One of the fastest wearing items on the bike, huge negative effect on handling when worn, and MOT failure if leaking. In most cases you need to replace the whole damper for something like 1000 dollars (if buying original).
Forks are a bit easier but require lots of disassembly if you want to remove all the oil. Small plug at the bottom to empty the oil and fill plug at the top would not be prohibitively expensive to implement.
Annual fluid change is a bit over the top IMHO. You can do inspections without changing fluids. I usually change brake fluid every 2-3 years. Forks depend on mileage, shocks if I have the budget. Sometimes I just replace worn shocks with cheap new aftermarket ones.
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Come to think of it are there any fluids in the gen 3 bikes other than brake fluid? Of course the battery, motor, controller are all air cooled but I thought the chargers still were as well.
From the top of my head, on top of the brake fluid, there is oil the forks and damper.
I've never understand why dampers are generally not serviceable item (without expensive special equipment). One of the fastest wearing items on the bike, huge negative effect on handling when worn, and MOT failure if leaking. In most cases you need to replace the whole damper for something like 1000 dollars (if buying original).
Forks are a bit easier but require lots of disassembly if you want to remove all the oil. Small plug at the bottom to empty the oil and fill plug at the top would not be prohibitively expensive to implement.
Annual fluid change is a bit over the top IMHO. You can do inspections without changing fluids. I usually change brake fluid every 2-3 years. Forks depend on mileage, shocks if I have the budget. Sometimes I just replace worn shocks with cheap new aftermarket ones.
Until about 20 years ago almost all fork female-sliding suspensions had a small hole sealed by a nut at the bottom of the fork tubes that would allow you to drain the fork fluid and refill the forks from the top cap without removing the forks. It only took a few minutes and I used to change fork oil every other year, at the same time I would change brake fluid. Garage maintenance life was a lot easier when mechanical things were simpler. Maybe they didn't work quite as well as they do now, but for me, the ease of maintenance was worth it. And that goes double for manufacturers doing away with all of the grease nipples that used to be on most chassis pivots, such as at the swing arm, suspension and steering bearings, which are now long gone. :(
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Even when you do your own fork work, many of them now need expensive custom parts / tools to work on. If you have any specialized stuff on them, like the andriani gas system in them, that'd even more custom tools. They really don't want you to do your own work anymore. This is pretty much what keeps the shops in business anymore imo, is doing work you no longer can. with newer bikes, even ice ones, getting more and more electronic oversight and control over crap, expect even fewer items being user serviceable.
everybody bitches about parts being married to the bike / assembly, well it's a sure fire way to pretty much guarantee you bring it to the shop and they get your money... expect more of that in the future too.
i remember reading an article a little ways back where new cars and trucks etc, are all going to be made, just one way, with all the shit on them, saves money not having to run different assembly lines, and you basically do subscriptions to the stuff you want to use. so you want the extra hp, that's 50 a month to unlock that on the chip, so you want to use the ac, that's 12 a month, and it's all going to be subscription based. many of them are moving that way already, they really don't want it where you own it, but lease it... with a title ::) they'll do you just like the cellphone scumbags. every few years, your shit just isn't really working really well anymore... well for 1500 and 120 a month, we can unlock an upgraded power package for you... i can see that happening .
aaron
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For someone that assumes everything is AI that has to be one of the most AI responses I've seen from you ::) Talking about headgasket leaks and gearbox fluid when it comes to a Zero.
My impressions are that this individual dabbles in AI & that has caused this individual to suspect that others are doing the same (paranoia).
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hush and go take your pills child, the adults are speaking.
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Yeah, there's nothing wrong with getting yourself a separate battery tender, ideally one designed for lithium batteries that doesn't bring it up to full and keep it there. Also, something else to consider for winter, this is the time of year when people load up the accessory port lines with things like heated gear. The DC-DC is only a 300W unit, and the 12v battery is there to sort of bolster it. The point is if you're pulling 300+ Watts during winter riding the 12v battery is actually being discharged and can't refill itself until the load on the 12v lines is reduced.
I'm not saying you're doing that, I'm just pointing out additional complications during times of cold weather riding.
I had that problem because of extra lighting, and a horn set that draws 12a when active. It might have contributed to the DCtoDC having problems and having to be replaced. I bought one used from a breaker in CA.
Also the 12v battery lost most of its capacity and I had to replace that too.
I added a separate additional 12v battery ( i think its sold for storing solar power ) in the saddle bag that is the power source for those accessories now. Its not connected to the motorcycle at all, a separate system.
No more problems, but I do have to connect to charger to that battery every couple weeks; something else to keep track of.
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I added a separate additional 12v battery ( i think its sold for storing solar power ) in the saddle bag that is the power source for those accessories now. Its not connected to the motorcycle at all, a separate system.
No more problems, but I do have to connect to charger to that battery every couple weeks; something else to keep track of.
I just... I mean. We're hearkening back to 2007 memes with Xzibit.
(https://i.imgflip.com/agm702.jpg)
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……..
I had that problem because of extra lighting, and a horn set that draws 12a when active. It might have contributed to the DCtoDC having problems and having to be replaced.
…….
On my DSR I power the aux horns via a NO set of contact on a relay & power the heated gear & hand grips through the NC contacts. (load shed/share to reduce power requirements on dc/dc converter).
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Guess I have to answer my own (original) question, after reading the manual, which says:
The 12 volt battery is charged from the motorcycle’s power pack. During regular operation and when connected to a charging cable, the MBB (Main Bike Board) will monitor the 12 volt battery’s charge level to ensure that it’s charge level is maintained.
So, the 12 volt battery seems to be monitored / charged when the charging cable is connected, (and I assume they are talking about the cable of the main battery).
By the way, I did not yet check if the voltage of the 12 volt battery does indeed go up to 13+ Volts when I charge the main battery, will do that next time.
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I have a strong suspicion that even if a powered charging cable is connected to a Gen3, that if the bike is not actively charging, the 12V system is turned off. I verified the signs of this myself just last night: when I plug in, the bike springs into life, the dash comes on, and it displays the charging progress for several hours while the main contactor is connected. Then, when charging finishes, the contactor clicks off, and the dash goes off - which would mean the 12V system is no longer activated.
tldr; don't just shove in your charging cable over winter and expect the 12V to maintain charge for months. You have to be actively charging.
Cas :)