Golden Motor 36v with 12v booster/turbo button???

[csm]

there was a post on how to add a 12 booster battery for temporary added power and speed. by running a 12 volt SLA battery in series with the 36v lithium battery. This is the diagram they posted ( I added instead of one 12 volt battery, to add two 12 volt batteries in parallel, in series with the 36 volt battery. Will this work?? what other electronics are needed to make this work. I am not sure if this is a do-able circuity or safe. Lookng for feedback from masters at ES.

"A 36V 16Ah battery in series with a 12V 7Ah battery would give 48V, but your usable capacity would be limited by the 7Ah battery.

The smaller capacity battery would obviously become discharged much sooner than the larger one, and if there is no battery protection on the lower capacity pack, it will soon become damaged simply by allowing its voltage to fall too low, and also by the larger capacity battery trying to reverse charge it when it becomes so depleted that it can no longer supply the current being consumed by the motor.

A smaller capacity battery could be used as a temporary power boosting feature as shown here:

It would be a good idea to have some sort of audible battery warning device (or perhaps a voltmeter) connected in parallel with the relay, to automatically allow monitoring of the 12V battery, but only while it is actually being used.
If wired this way, the monitoring device would not gradually discharge the 12V battery while the boost function was not in use."

Seems to me that a voltmeter in parallel with the 12v booster battery would gradually discharge the battery, even while the boost function was not in use, if the boost button was in the on position??

I am wondering if this setup could also be used as a way to have a battery backup or reserve power.. Say, for example the person uses 60 or 80 percent of the capacity of thier 36v battery. And it is not coming close to to triggering LVC of the BMS.. the person flips the switch that adds the additional 12v 7ah batter in series.. What would happen? what voltage would the system have? how many ah of capacity would it have? What would happen to the batteries?

 

[csm]

My revision of above wiring dieagram for turbo 12 volt booster of a 36 volt ebike system on Golden Motor with a Magic Pie II hub motor.

revision 3 of my turbo button/switch circuit.

 

[dnmun]

i would recommend you avoid the golden motor battery. there are a buncha threads on them here. maybe someone who had one will comment.

if you want 48V then you should just buy a 48V battery, but not SLA since the cost and weight do not compare to the lifepo4 packs. consider the battery a lifetime investment and be willing to pay for it up front. then take care of it.

the SLA can only be discharged down to about 10 volts so you need to monitor it also if you follow your diagrams. that is why the controller has an LVC, to protect the SLA since that is what most chinese use. for a 36V controller the LVC is set to 30 1/2V.

if you use a 48V lifepo4 pack like the ping or the ones from cell-man or BMS battery then the lifepo4 pack will produce power down to about 33V so you can use the 36V controller with the 48V lifepo4 pack and be able to use the entire capacity of the battery without it hitting LVC on the controller.

all so much simpler too.

 

[csm]

My revision of above wiring dieagram for turbo 12 volt booster of a 36 volt ebike system on Golden Motor with a Magic Pie II hub motor.

revision 5 of my turbo button/switch circuit with a volt meter connected in parallel with the booster battery. According to another person who suggested the use of the volt meter to track the usage and state of the booster battery, the volt meter would not cause drain of the batter when the booster button/swisth is in open or off state. I think the one of the volt meter wires would need to connect on the positive side of the turbo switch to cause disengagment of the volt meter circuit when turbo button is in open or off possition.

 

[dogman dan]

It's fine to add a 12v booster, for use when more power is needed. But to use additional voltage in series to extend range will ruin the primary battery by overdischarging it. Go far enough, and you trip the bms if bms protected. But if no bms, you will just run the primary battery down to zero.

To extend range, you want to paralell the same voltage battery in at the start of the ride. Or unplug one battery and plug in another.

 

[csm]

It's fine to add a 12v booster, for use when more power is needed. But to use additional voltage in series to extend range will ruin the primary battery by overdischarging it. Go far enough, and you trip the bms if bms protected. But if no bms, you will just run the primary battery down to zero.

So what you are saying essentially is that the primary battery would be safe as long as the BMS in the primary battery is working normally and would trip if the cells got too low. I am not clear how the primary battery would over discharge, unless you are just referring to normal discharge, on the main battery.. I can see how the booster battery could overdischarge if it does not have a bms to protect it. In this case the primary battery would have (36v) 16 ah and the booster battery would have (12v) 6 ah. In this case, it seems the 6ah battery would discharge first?

 

[Hillhater]

I can say for sure that 40a relay will weld its contacts within a few times of use.

 

[csm]

I can say for sure that 40a relay will weld its contacts within a few times of use.

Do you think that would happen even if the motor is not being engaged? or just when pushing while motor is drawing current?

 

[dogman dan]

I try not to write so much the clear becomes unclear, then write what makes no sense sometimes.

What I mean is say you have ridden for awhile with a battery with no bms. Could be lead, nicads, RC lipo whatever. Call it a 36v pack, meaning that you shouldn't discharge it below about 32-34v or therabouts. So you started the ride with 45v, and have ridden awhile and now are at 36v. Wanting to ride further, you add a 12v battery in series that has a voltage of 14v when you add it.

Now you have 50v, and can continue for quite a bit further right? No. Because the 12v battery added will not be recharging the 36v pack. Ride till your total pack voltage is 40v, and the original 36v pack will be at 31v or lower. Keep riding and it just gets worse. The original pack will be at 24v by the time you reach 36v total pack voltage.

If the 36v battery had a bms, then the same thing would happen, except the bms would cut off the pack. You'd get just a tiny bit further down the road, but no further than you would have gone anyway on just the original pack.

So what about adding some battery paralell. All the experts agree, it's a bad idea to paralell a charged battery with a discharged one. The charged battery will charge the discharged one rapidly. Perhaps rapidly enough to melt wires. Definitely rapidly enough to damage both batteries.


Backing up a bit to the start of the ride. At the start of the ride, its ok to add 12 in series for more voltage and range. Adding the 12v then, of the same capacity battery will add capacity to your total, and give you more potential speed or more potential range. If you use the added 12v sparingly, with a boost switch, you'd get the added power at times, but not much potential extra range. So really, it makes more sense to just add enough capacity of 12v to your system and ride the whole ride at 48v. The switch sounds cool, but it's much more practical to just have the extra power all the time. If you don't ride faster much, you will have more range. The bike will leave stop signs all the time better.

Or you could just add range by paralelling in more 36v at the start of the ride. This doesn't get you much more power up a hill, but your battery will like it because you lower it's discharge c rate. It may lower the depth of discharge, which the battery will also like. It will sag less, so you may still see a slight improvement up hills. And lots more range.

 

[dnmun]

i repeat, do not buy the golden motor battery. you should search here first.

 

[csm]

If the 36v battery had a bms...

Backing up a bit to the start of the ride. At the start of the ride, its ok to add 12 in series for more voltage and range. Adding the 12v then, of the same capacity battery will add capacity to your total, and give you more potential speed or more potential range. If you use the added 12v sparingly, with a boost switch, you'd get the added power at times, but not much potential extra range.

Basically, you are saying the circuit would work without injuring the circuits or the lithium battery that has BMS?

How are you calculating the added range? I am thinking that if each 12v 6ah can generate about 8-10 miles of range, then the added 12v 6ah batter could generate at least about 6 miles additional range (or more) of same consumption of energy riding. It would also give the rider access to added power during the ride (perhaps like getting up a particular steep hill? or added speed during a particular stretch of road which may require higher speed to be driven on safely?).

I am thinking the 12v SLA batteries and chargers are more readily available. And can be found at any auto and motorcycle parts stores. And some even have much higher AH capacity than 6ah.