i'm looking for a switch so i can switch between 2 batteries, so like two set of the two power wires getting switched betwen two controller power wires, so two three-way switches or one all-in-one switch\. it needs to take 100v 45a.
Switch between batteries
- Thread starter ian.mich
- Start date
wineboyrider
1 MW
Do you want a DPDT switch or Double pull double throw ? :lol:
TylerDurden
100 GW
If they are the same voltage, it may be better to run them in parallel.ian.mich said:
999zip999
100 TW
Ask wineboyrider. Mix it up. I think he only starts with wine.
dnmun
1 PW
you do not want to run the two packs down separately. combine them in parallel and use them like that and charge them both together too. they will last longer and you will get more power out of them. do not put a switch in between them.
Jeremy Harris
100 MW
dnmun said:
Normally I'd agree that this is the best thing to do with packs that are the same voltage and chemistry, but the OP has stated that the batteries are different voltages ("its a 26650 48v 17ah pack, and a 12S2P lipo"), so he can't parallel them, hence the request for the switch advice.
Monstarr
100 W
Why can't u simply use a Anderson SB50 switch configuration?
Much cheaper imho than a high current DC switch.
Much cheaper imho than a high current DC switch.
dogman dan
1 PW
A switch sounds cool, but they get expensive. Only takes about 30 seconds to stop and change batteries. I've never found it a burden on really long rides that take hours anyway.
Sounds to me like not quite close enough in voltage to paralell. Even if you discharged one till it matched the other, you'd risk overdisharging one of them.
Sounds to me like not quite close enough in voltage to paralell. Even if you discharged one till it matched the other, you'd risk overdisharging one of them.
wineboyrider
1 MW
http://www.allelectronics.com/index.php?page=seek&id[m]=pattern&id[q]=dpdt&x=0&y=0
A lot of cool switches here also, the currie ezips have a cool rocker switch that switches one left side pack to the right side pack..?
A lot of cool switches here also, the currie ezips have a cool rocker switch that switches one left side pack to the right side pack..?
Monstarr said:
So just use sb50s to disconnect and reconnect packs? sounds like a good option.
and wineboy thanks for the input, but i seem to only find ones that take 125V 20A? that won't work for the 45A that I would want to be able to do
dogman dan
1 PW
That's the problem in a nutshell. Big high amp switches cost a bit. Cheap ones can work, but not forever. But 45 amp andersons are quite affordable.
dogman dan
1 PW
That's affordable, only 30 bucks more than some andersons or bullets. I'll never get the need for the switch myself.
dnmun
1 PW
yep, did not read the part where you said one was lipo and the other was canned lifepo4. you will need to use high current diodes to combine these two in parallel. there is not much difference in voltage between the two packs so a 20V schottky is about the lowest i have seen. that keeps the forward bias to a minimum so you don't make a lot of heat.
so figure out how much current you need and then you will know what size diodes to use. you don't wanna have a lipo pouch pack in parallel with another battery without a diode to prevent it from being overcharged if one of the lipo pouches goes flat, 0V.
so figure out how much current you need and then you will know what size diodes to use. you don't wanna have a lipo pouch pack in parallel with another battery without a diode to prevent it from being overcharged if one of the lipo pouches goes flat, 0V.
Jeremy Harris
100 MW
dnmun said:
We don't know for sure the make up of the 48 V pack, so can't say with confidence that it will discharge safely to the point where the lower voltage pack will start to supply current. Maybe it will, maybe it has a BMS that cuts it off, but without knowing for sure I'd be very hesitant to recommend it to someone unfamiliar with the potential issues.
23skidoo
10 W
- Joined
- Feb 22, 2012
- Messages
- 98
Configured to handle the initial charging of the capacitors in the controller, one would need a switch with a dc current rating much above the controller rating. On the other hand, if the switch only has to handle the change in voltage between one pack and another, and switching is done with the throttle off, then a much lesser switch is needed. It's hard to know what the minimum switch requirement really would be.
darrel
darrel
hardym
100 W
I've been working with another ES member on a trike build with dual batteries (separate internal BMS'es), who wanted to switch batteries. Wants to ride 1 battery disance, stop, switch and ride home. The build has 2 48v li batteries with 40A controller.
I found this DPDT switch with a "center off" for $15, shipping included, which seemed too good to be true:
http://www.goodluckbuy.com/szl9-32-...h-combined-switch-rotary-switch-32a-440v.html
The switch arrived today (3 weeks shipping). Bigger size than I expected, and it needed to be disassembled and reconfigured to correctly work the contacts A--off--B. (perhaps that's the reason for the cheap price). I'll post some pics here in a couple days.
Mark.
I found this DPDT switch with a "center off" for $15, shipping included, which seemed too good to be true:
http://www.goodluckbuy.com/szl9-32-...h-combined-switch-rotary-switch-32a-440v.html
The switch arrived today (3 weeks shipping). Bigger size than I expected, and it needed to be disassembled and reconfigured to correctly work the contacts A--off--B. (perhaps that's the reason for the cheap price). I'll post some pics here in a couple days.
Mark.
dnmun
1 PW
yep, just connectors instead of a switch is simpler.
if you combined them in parallel you would have to use a diode to prevent charge flowing from one pack to the other. since your lifepo4 pack is 16S it would charge up to 58V and the lipo 12S would charge up to 49V so the lifepo4 pack would try to push current into the lipo and it would result in the lipo over charging and possible being damaged or going into thermal runaway.
but by combining the packs in parallel you would reduce the current demand on each pack so they would be able to deliver the current without as much power lost in the internal resistance that these lithium ion storage cells show when called on to release those ions from their storage spots inside the cathode matrix of the cells.
the lipo would discharge down to about 12S X 2.8V = 34V or so and the lifepo4 would discharge down to about 34V or so and the two packs would be totally discharged at that point.
if you had a diode on the lipo pack the regen would block the lipo from accepting the charge, but if there was no diode on the lifepo4 then the regen could recharge the lifpepo4 pack. but if the lifepo4 was pushed up in voltage by the regen then that voltage would not drain into the lipo either so it would remain protected from overcharging.
since your lifepo4 BMS would protect the lifepo4 pack, and the cellogs that monitor the lipo would alarm if the lipo was below the cutoff then you would have some measure of protection of each pack while in operation.
since you decided to just use each pack individually and pull the full current from each pack sequentially, this is more of a rhetorical exercise and will just give others an idea of how to approach the combining in a more analytical way. the one diode you would need capable of 20V25A, .45V forward bias is only 28 cents from mouser.
if you combined them in parallel you would have to use a diode to prevent charge flowing from one pack to the other. since your lifepo4 pack is 16S it would charge up to 58V and the lipo 12S would charge up to 49V so the lifepo4 pack would try to push current into the lipo and it would result in the lipo over charging and possible being damaged or going into thermal runaway.
but by combining the packs in parallel you would reduce the current demand on each pack so they would be able to deliver the current without as much power lost in the internal resistance that these lithium ion storage cells show when called on to release those ions from their storage spots inside the cathode matrix of the cells.
the lipo would discharge down to about 12S X 2.8V = 34V or so and the lifepo4 would discharge down to about 34V or so and the two packs would be totally discharged at that point.
if you had a diode on the lipo pack the regen would block the lipo from accepting the charge, but if there was no diode on the lifepo4 then the regen could recharge the lifpepo4 pack. but if the lifepo4 was pushed up in voltage by the regen then that voltage would not drain into the lipo either so it would remain protected from overcharging.
since your lifepo4 BMS would protect the lifepo4 pack, and the cellogs that monitor the lipo would alarm if the lipo was below the cutoff then you would have some measure of protection of each pack while in operation.
since you decided to just use each pack individually and pull the full current from each pack sequentially, this is more of a rhetorical exercise and will just give others an idea of how to approach the combining in a more analytical way. the one diode you would need capable of 20V25A, .45V forward bias is only 28 cents from mouser.
wineboyrider
1 MW
http://www.amazon.com/Ezip-Switch-C...1_10?s=cycling&ie=UTF8&qid=1340839154&sr=1-10
Here is the currie switch.... 8)
Here is the currie switch.... 8)
Kin
10 kW
dnmun said:
Hi Dmnum, since you are going through the exercise anyway, can I ask you if I understand the situation? I think only just the other weekend I used a diode in a circuit (other than an LED- which i still consider magic) and started figuring out what this diode business is about.
So, as I believe it, you are suggesting to connecting both LiPO4 and LiPo ground together, and that goes to the black of the controller batt input. Then, a schottky diode goes facing "forward" out of the LiPo battery, at which point it connects to the LiPO4 battery positive, and the line continues to the controller.
So the operation will be that the LiPo battery, which starts charged at a lower voltage, will lose .2v across the schottky but otherwise contribute to the bike. Meanwhile, the LiFePO4 battery can't dump into the LiPo battery because although things can go "out" of the Lipo battery, they can't go into the Lipo battery.
I'm thinking this through in my head, but I still can't quite understand what's going on where the LiPo and LiFePO4 is connected. So...uhh...does the LiPo just not do anything until the LiFePO4 is of the same voltage (actually, .2v lower, technically)? It feels odd, but I guess diodes feel odd.
Uhhh, wineboy, to clarify, because someone might read your link, the currie switch isnt going to help you here....It just switches the controller on and off switch. It's only like 10A
wineboyrider
1 MW
10A is right, but you are wrong it is a dpdt switch that switches one batter pack to another
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