Help on Lipo Configuration

Greetings!

I am upgrading a razor e200 scooter - making it longer and upgrading to 48v 1000w motor and 1000w 48v controller. (min 41.5v max 60v - but was told to keep it under 55v)
I want to use lipos's for the first time to gain some experience. (I have used Luna Lithium packs for my e MiniBikes in the past)

So my question is, can I mix different voltages for lipos to get the desired voltage?

For example:

For a total of 51.8v:
Two Multistar High Capacity 4S 10000mAh Multi-Rotor Lipo Pack 4S1P / 14.8V / 4Cell
One Multistar High Capacity 6S 10000mAh Multi-Rotor Lipo Pack 6S1P / 22.2V / 6Cell

Do they need to be the same mAH when running in series? or can I combine a 12000mah in there since they are $30 cheaper today?

Forget those nominal voltages and calculate based on 4.2V/cell. 14S will be 58.8V HOC (hot off charger). Seems like that will put you over your 55V limit.

12S (2qty 6S in series) HOC will be 50.4V

13S, 54.6V HOC is probably what you’re looking for but that’s gonna be very oddball RC Lipo pack combination.

If the 55V is a deal breaker I’d just do 12S and enjoy 50V HOC.

Unless you’re cell level monitoring during discharge, you’re playing a very dangerous game using different capacities in series strings.

Thanks!

I will go for two of the MultiStar High Capacity 6S 12000mAh Multi-Rotor and call it a day. They are $60 each.. pretty cheaper than the 10000mAh's weird.

Ykick said:

Forget those nominal voltages and calculate based on 4.2V/cell. 14S will be 58.8V HOC (hot off charger). Seems like that will put you over your 55V limit.

12S (2qty 6S in series) HOC will be 50.4V

13S, 54.6V HOC is probably what you’re looking for but that’s gonna be very oddball RC Lipo pack combination.

If the 55V is a deal breaker I’d just do 12S and enjoy 50V HOC.

Unless you’re cell level monitoring during discharge, you’re playing a very dangerous game using different capacities in series strings.

Click to expand...

While it's better not to mix & match capacities in a series string, the only adverse effects would be total capactity limitation down to that of the smaller packs, while those packs would likely experience expedited wear VS the (larger) 12ah pack(s) as depth of discharge is increased.

Mixing different voltage packs in series SHOULD have no real-world issues, but it's generally better to match the packs if possible, for simplicity if nothing else.

I'd also use max charge voltages to relate to controller friendliness since their limiting factor is generally the mosfets and ~60v capacitors. I'm running 58v (14s) fully charged on my 48v controller w/ no problems. It gets me another few mph over my 12s pack.

What speed are you shooting for on the scooter?
That, in conjunction with how much amperage your system can handle is kinda a determining factor on a target voltage. Generally 25-30a and 12-14s is good for 25-30mph with standard wind hub motors in a standard bicycle wheel.

Thanks nutspecial. I decided not to mix, and go with the two 6s 12000mah's. Ordered and done $120 is not a bad deal! Luckily I already had a lipo charger, although its only a 50w 6amp.

The scooter I have is a E200 razor, I am cutting the frame midway and lengthening it 12" just for feet space (and the motor will be mounted on top near the back). The motor sprocket is a 11 tooth to a rear 55 tooth (default on the e200) I'd like to see if I can manage to put a fatter rear E300 tire and 65 tooth rear sprocket - I dont know the clearance difference yet, I have a email out to some suppliers.

I am hoping to get 25mph on it (for my kid who is 12 and 150lb - he's 5'5" already) . I had this same motor and controller with 48v sla's in a baja mini bike conversion that got 25mph - and it was HEAVY!

nutspecial said:

While it's better not to mix & match capacities in a series string, the only adverse effects would be total capactity limitation down to that of the smaller packs, while those packs would likely experience expedited wear VS the (larger) 12ah pack(s) as depth of discharge is increased.

Mixing different voltage packs in series SHOULD have no real-world issues, but it's generally better to match the packs if possible, for simplicity if nothing else.

I'd also use max charge voltages to relate to controller friendliness since their limiting factor is generally the mosfets and ~60v capacitors. I'm running 58v (14s) fully charged on my 48v controller w/ no problems. It gets me another few mph over my 12s pack.

What speed are you shooting for on the scooter?
That, in conjunction with how much amperage your system can handle is kinda a determining factor on a target voltage. Generally 25-30a and 12-14s is good for 25-30mph with standard wind hub motors in a standard bicycle wheel.

Click to expand...

KozmoK said:

Thanks!

I will go for two of the MultiStar High Capacity 6S 12000mAh Multi-Rotor and call it a day. They are $60 each.. pretty cheaper than the 10000mAh's weird.

Click to expand...

I dunno if you're in USA but if you want a great yet dirt cheap bulk charger grab 1 or 2 of these:

http://www.ebay.com/itm/222222564090?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Just don't use it on bare pack unless you're certain cell balance is in pretty good shape. Adjust it to about 50V and limit about 3A. An RC power meter becomes very useful here.

Cool KozmoK, I don't know why I was thinking in hub motor terms- of course you can gear for whatever mph you want!. +1 on bulk charging. It's a pita and actually unnecessary to primarily use a balance charger for a multipack setup.

This is very interesting! I want to do this, so I dont have to charge individually and using the jst blance cables.
now you say done use it on a bare pack, is there a device that will plug into the jst balance connectors and stop when its fully charged? like one of these: http://www.buddyrc.com/3-in-1-battery-checker-balancer-discharger.html

Ykick said:

KozmoK said:

Thanks!

I will go for two of the MultiStar High Capacity 6S 12000mAh Multi-Rotor and call it a day. They are $60 each.. pretty cheaper than the 10000mAh's weird.

Click to expand...

I dunno if you're in USA but if you want a great yet dirt cheap bulk charger grab 1 or 2 of these:

http://www.ebay.com/itm/222222564090?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Just don't use it on bare pack unless you're certain cell balance is in pretty good shape. Adjust it to about 50V and limit about 3A. An RC power meter becomes very useful here.

Click to expand...

https://endless-sphere.com/forums/viewtopic.php?f=14&t=85665
There's some basics and starting points in this recent thread ^^^

My packs are in good enough condition that they would be fine charging without a BMS but I still tend to use one. At least for charging. High power discharge BMS can be rather large and expensive so I often discharge directly from battery leads and simply charge using a low power BMS.

I’ve used these BMS before and they’re okay but it’s a bit of money and work to install cleanly:

http://www.ebay.com/itm/44V-48V-50-4V-12S-60A-Lithium-ion-Li-ion-LiPo-Li-Polymer-Battery-BMS-PCB-System-/221644780045?hash=item339b0ef20d:g:aXsAAOxy06hSEdYj

If you wanna draw more than the 60A max or use a smaller cheaper BMS you can always wire it for charging only and power out directly from the main power battery leads?

I dare say majority of folks don’t use a BMS to charge/discharge RC Lipo. They set the charger or power supply to a fixed voltage for the cell count (50V in this case) and it will stop when it charges up and reaches equilibrium.

The only real problem with that manual management scheme is if a cell becomes unbalanced or completely shorts and you attempt to charge the pack anyway?

Or, what if the charger/supply fails in some manner and the voltage goes sky high over charging the pack?

These are things that don’t happen very often if at all but if it did, what would be the ramifications in your home/shop? Can your location deal with such an exothermal event? Or, can you keep a close enough eye on the cell voltages to catch something before it gets out of hand?

12S from 2qty 6S hobby packs will be fairly easy to balance any number of ways. But I don’t like those cell bleed balancers at all. They’re alright for folks without an RC Charger but if you have an RC Charger?

Can your 50W RC charger do single (1S)? Just make a lead with pins that can tap into the RC Lipo balance plug and charge/discharge whatever cell needs to be brought into balance as a single cell. Keep it under 2A, small wire you know.

Once you go down the RC Lipo road, Cell Log 8M is a damn handy tool to have on hand for quick checks of your packs. See video:
https://www.youtube.com/watch?v=uxyri4jOSm8
[youtube]uxyri4jOSm8[/youtube]