I want to replace my Schwinn Global GS battery with a free Schwinn Tailwind battery. I want to make sure there's no problem with the match to the Global GS box on the rack (controller?) I'm seeking opinions/warnings. I can solder, but don't know much about electric. The old GS battery is 29.4V 10Ah Lithium Ion polymer. The new Tailwind is 24V 4.2Ah Lithium Ion. Am I right to assume it's ok because the replacement is less powerful? The Global rack won't accommodate the Tailwind battery and I can't get the box free without disconnecting all the wires. So, I plan to leave the box in the rack, and extend wires to the battery in a pannier. I want to leave the cylindrical pin connectors anchored securely to the battery and remove the battery via new in-line insulated connectors. That way I won't have to worry about arcing at the "butt joint" connection (spring loaded pins' contact to flat terminal surfaces on the battery), which I will leave strapped tightly together. The original failure was due to arcing of the locked-on pin to battery terminal vs. short battery life. I can still use the old battery, but there's not much left in it. I severely ration my use of it. When this replacement battery fails I'm on to a better system.. Thanks for the tips!
Battery replacement retrofit to Schwinn GS
- Thread starter klr
- Start date
Actually, that makes it potentially problematic. Since it isn't as high a voltage, it is possible that the low-voltage cutout on your controller may trip before the new pack is actually discharged very far. Lower voltage will also give you less top speed, usually.klr said:
Also since it's capacity (Ah) is less than half of the original pack, it'll give you less than half of the range you had with the old pack. (actually since it is also less voltage, then the total Wh (watt hour) of the pack is a lot less than half, and thus a lot less than half the range).
One more problem is that since many of these packs are made with low-C-rate cells, they can't supply as much power at peak or sustained when they are made in smaller capacities. If they have a BMS built into the pack to protect it against overcurrent, this isn't that big an issue for the pack, but it may cause it to shut off the motor whenever you accelerate harder or go up hills, etc. If it does not have anything to protect against overcurrent, it could damage the pack itself (either immediately or over time, depending on how the cells are made and how it all reacts to that) if the current drawn by motor is higher than what the pack can safely supply.
Most likely it will work, just won't give as high a speed or as much range. You will want to use the charger from the new battery with the new battery, and only use the charger from the old one with the old one, since they are different voltages.
Basically it's like having a smaller gas tank with less-effective gas that doesn't let your motor run as fast as it would with the original.
dogman dan
1 PW
That's a bit of an odd voltage on the original battery. A lot would depend on the actual setting of the low voltage cutoff of the controller. If it's set to 28v or so, you'd be screwed dropping to 24v, which likely comes off the charger right about 28v.
Many of us here would be more inclined to just leap to 36v. 7v higher is not that likely to burn out the controller or motor, and you'd have a peppier bike. My suggestion would be to splice on a 36v 10 ah lifepo4 battery from pingbattery.com
Many of us here would be more inclined to just leap to 36v. 7v higher is not that likely to burn out the controller or motor, and you'd have a peppier bike. My suggestion would be to splice on a 36v 10 ah lifepo4 battery from pingbattery.com
Does anyone know if there is a BMS in the Tailwind battery? I'm wondering if I should go ahead with my plan, or cut my losses, not risking a battery destruction and all the unknown that entails. I'll skip the long story, but what I have now is two Schwinn Global GSs with their dying batteries; and a new Tailwind battery with it's matching charger that doesn't fit my bikes. The first Global bikes' terminal got fried, likely from arcing. It burned the little plastic housing aligning the connector dowel-shaped pins, and burned the connector end. Because of that (not a used-up battery) I got a replacement bike; but now it's battery has as little left as the original. I wanted to salvage what I could without buying a $800 Global battery with it's likely short life span. I managed to get a new, less-powerful Tailwind battery free, but had to buy a matching charger for $300! I bought the original GS new for $1000, so I'd like to have one functional electric bike for my $1300, that I can turn on for hills, at least. I've come to understand that I can't tax the batteries on hills nor run it down to the flashing light level. I'm disappointed since all I wanted was to get to work fast with stuffed panniers; and get up hills to get home (11 mile one way, charge at work) and ride up hills on weekends. I'm getting in better shape under the present rationed-battery circumstances. My spouse asks why I persist with this electric idea. I know you'd understand!
Thanks amberwolf and dogman. Of course I would like to skip to Ping's 36V, but I want to consider the cost/benefits of maximizing what's left vs. dispensing with some or all of it. Should I be looking for answers regarding the controller's low voltage cut off threshold to avert potential damage to the battery, or is a trial and error approach safe and worthwhile? Is there any risk to other parts of the system in this type of novice play? I don't want to damage something that precludes an eventual switch to a ping battery. does it even matter with the crap I've gotten stuck with? I'm wondering if I should try to unload the free Tailwind battery and it's $300 charger...Thanks for the guidance.
The best way I can think of to salvage the whole battery mess is to take both of the original batteries apart, and check the cells to find the bad ones or bad connections that are causing the problems you're having with them.
Then if there are bad cells use both packs to build one bigger good pack out of the good cells left from each. As long as it is the same number of series cells, you can also still use the BMS from either original pack for this new one (and have a spare in case something goes wrong).
This new pack probably isnt going to fit inside the original box, so you will likely have to come up with something that fits in a pannier to hold it instead, and then use the connector method you've already worked out to hook it to the bike if you are not wanting to just replace the original problematic contact scheme.
(FWIW, that kind of spring-loaded-pin to plated-pad contact scheme is problematic even on wheelchairs and powerchairs that don't have to deal with bumpy roads; I have an SLA pack from one, given to me just because of that problem, which had melted the cotnact point on the bottom of the pack container.)
Having more cells in parallel will actually make it easier on the whole pack to provide more power for longer periods, for those hills, without wearing the cells as much.
Without doing any calculations for distance and terrain vs. power usage, I'd guess that the rest of the bike is more than good enough to do what you want if only the battery could handle the power usage and had good connectors. Right now I would guess that rebuilding the two originals is your lowest-cost alternative for fixing the bike up to get what you want out of it.
Then if there are bad cells use both packs to build one bigger good pack out of the good cells left from each. As long as it is the same number of series cells, you can also still use the BMS from either original pack for this new one (and have a spare in case something goes wrong).
This new pack probably isnt going to fit inside the original box, so you will likely have to come up with something that fits in a pannier to hold it instead, and then use the connector method you've already worked out to hook it to the bike if you are not wanting to just replace the original problematic contact scheme.
(FWIW, that kind of spring-loaded-pin to plated-pad contact scheme is problematic even on wheelchairs and powerchairs that don't have to deal with bumpy roads; I have an SLA pack from one, given to me just because of that problem, which had melted the cotnact point on the bottom of the pack container.)
Having more cells in parallel will actually make it easier on the whole pack to provide more power for longer periods, for those hills, without wearing the cells as much.
Without doing any calculations for distance and terrain vs. power usage, I'd guess that the rest of the bike is more than good enough to do what you want if only the battery could handle the power usage and had good connectors. Right now I would guess that rebuilding the two originals is your lowest-cost alternative for fixing the bike up to get what you want out of it.
dogman dan
1 PW
Nothing to lose by fiddling with the old dead batteries, that's for sure.
No danger in exploring the lvc of the controller with some lead batteries, or the tailwind 24v battery. Lead would be nice, simply because they have no bms to shut off. So any cutoff would have to be the controller, not a bms.
Connect it up and see what happens, since you have the battery now. I'm going to assume that 24v is close to where you should stop discharging with the tailwind battery, so run it, and see what happens. If you can run it a few miles great. If it only goes a block and starts cutting out, then you need a higher voltage battery.
You never know, some bikes are built with shockingly low lvc's in the controllers.
No danger in exploring the lvc of the controller with some lead batteries, or the tailwind 24v battery. Lead would be nice, simply because they have no bms to shut off. So any cutoff would have to be the controller, not a bms.
Connect it up and see what happens, since you have the battery now. I'm going to assume that 24v is close to where you should stop discharging with the tailwind battery, so run it, and see what happens. If you can run it a few miles great. If it only goes a block and starts cutting out, then you need a higher voltage battery.
You never know, some bikes are built with shockingly low lvc's in the controllers.
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