Charging to 24s with 14s charger and boost converter?

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hypertoric_amplituhedron   100 W

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Charging to 24s with 14s charger and boost converter?

Post by hypertoric_amplituhedron » May 21 2018 1:15pm

All right, I don't see how this wouldn't work, but may as well pass it by you guys as a sanity check. I have one of the affected Cycle Satiator 72v chargers that needs to go back for warranty. So, in the mean time, I still want to ride my ebike with a 24s battery. I have a 58.8v 3a charger, and I may borrow a friend's 5a. So, why not hook up my 14s charger to a boost converter, and push it to 97v?

I'm considering this boost converter :

https://www.amazon.com/DROK-Numerical-R ... erter&th=1

The input would be, at best, 58.8v and 5a : equates to ~300w . Figuring in the claimed 85% efficiency , that's 250w of output .

At 97v , that's 2.5a charging current for my 24s pack. That will only take twice as long as my usual 5a charge(13hr vs. 6.5hr), which I can afford.

Thoughts?
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amberwolf   100 GW

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Re: Charging to 24s with 14s charger and boost converter?

Post by amberwolf » May 21 2018 1:52pm

At least some chargers wont' start charging (outputting voltage/current) until they detect a voltage on their outputs that meets their limitation. If yours is like that, the boost converter will prevent it from seeing the battery and thus it's voltage, and so it won't start charging.

(the Satiator is like this, but it has a Force Start mode; other chargers like that don't).


If yours won't work without seeing the battery, you could charge the battery it was meant for, then use that battery to run the boost converter. (even leaving the charger connected to the battery so it keeps running without discharging the battery too far).

That would enable you to use a higher current / wattage output booster than otherwise, as well.

hypertoric_amplituhedron   100 W

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Re: Charging to 24s with 14s charger and boost converter?

Post by hypertoric_amplituhedron » May 21 2018 3:30pm

amberwolf wrote:
May 21 2018 1:52pm
If yours won't work without seeing the battery, you could charge the battery it was meant for, then use that battery to run the boost converter. (even leaving the charger connected to the battery so it keeps running without discharging the battery too far).

That would enable you to use a higher current / wattage output booster than otherwise, as well.

Now that sounds like a better plan. My 52v charger won't start until it detects voltage, as you suspect. So I will have to rig this to work, where the higher amp input would be a real benefit. My 14s 20ah battery will have to go through two cycles to fill my other 24s 38.5ah pack, but it can be done!

I'll probably look around for a better boost converter. I don't like the negative reviews of this thing, and concerning that it's only $30, they're likely legit. You know how that goes :D
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amberwolf   100 GW

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Re: Charging to 24s with 14s charger and boost converter?

Post by amberwolf » May 22 2018 1:26am

hypertoric_amplituhedron wrote:
May 21 2018 3:30pm
My 14s 20ah battery will have to go through two cycles to fill my other 24s 38.5ah pack, but it can be done!
As long as the charger is left on the 14s pack while it's running the booster, it'll probably keep the pack from having to run too far down during the highest current phase of charging the bigger pack.


I'll probably look around for a better boost converter. I don't like the negative reviews of this thing, and concerning that it's only $30, they're likely legit. You know how that goes :D
FWIW, if you're spending any serious money on a booster, you might just look at the HLG or ELG meanwells, if there are any with the output voltage range that is the difference in voltage between your 14s charger and your bigger pack's voltage. Lot of threads/posts about them (look up ELG or HLG ; there are other models too).

Then you can use it in series with your charger, to give the total correct voltage on the bigger pack, and your charger will perform the current limiting /etc that's necessary.

Or use two of the meanwells in series (I know the HLGs are isolated and will work that way).

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