Oset Batteries Lithium (LiPo) Conversion Directions

[gwhy]

can your charger do 5A per channel or is that total ?

 

[greg555]

can your charger do 5A per channel or is that total ?

 

per channel luckily

[gwhy]

if the actual charge per pack is going to be 5a then you would be looking at around 4 hours to charge tehn possible 1 or 2 hours to balance

[gwhy]

it take one of my 16ah 44.4v batterys around 3hours total to charge and balance this is at 5.5A and only 50% dischargerd : so 8ah @5.5A =3hours to balance charge

 

: edit

 

the bulk of the charging is done quite quick but once the cells come upto around 4v the current starts to drop off  this is why the top off charge can take so long

 

edit2:

  if i crank my charger upto 10A it can still take upto 2 hours to put back the 8ah and balance the pack , so its not linear.. if that makes sense

 

Edited December 31, 2015 by gwhy

[greg555]

Question still remains - Lipo or Life?

 

Greg

[greg555]

How hard is it makr a battery pack with BMS? 

 

[gwhy]

How hard is it makr a battery pack with BMS? 

 

 

Its not hard as long as you are ok with soldering and testing the bms function after you have put it together , the hard part is finding a suitable bms for lipo that will be ok for these bikes..

 

lifepo4 :  more expensive, heavier,bigger ....  easier to source a bms .. more forgiving  .. bms should protect from abuse

lipo : cheaper,ligher,and smaller  .....   harder to source bms .. less forgiving  .. bms should protect from abuse

[greg555]

I am not a stranger to soldering so lets say I want to make some LIFEPO battery packs for my boys.

 

They are both on 36V osets. Whats the max V you would recommend and what BMS do I get and how do I wire it. Also am I assuming correctly that OEM Oset chargers can be used?

 

Thanks.

Greg

[gwhy]

if you do a lifepo4 36v battery as in the same voltage as 3x 12v sla batterys then the standard 36v charger will work but you must have a bms

 

you will need 12 lifepo4 cells to make the 36v battery

 

the easiest way would be to buy 3 of these http://www.hobbyking.co.uk/hobbyking/store/__14074__ZIPPY_Flightmax_8400mAh_4S2P_30C_LiFePo4_Pack.htmlthat will make up one 8.5ah 36v lifepo4 battery and source a suitable 12s bms tehn you just wire it together

 

edit:

just been looking for a suitable bms .. and found this  http://www.ebay.co.uk/itm/12V-90A-Battery-Protection-BMS-Board-w-Balance-for-4-Packs-LiFePo4-li-batteries-/171928485718?hash=item2807bc7f56:g:QoIAAOSw9N1VkUl2

 

if you buy 3 of the above bms then this will be cost effective.. you would need to fit a 4s bms to each battery.

 

 

Edited January 12, 2016 by gwhy

[will barley]

Hey guys,

 

This thread has been super valuable to me - thank you - particularly @gwhy and @betarambo - I am doing a conversion for a 12.5" OSET right now and will then do a 16" conversion.  My main interest is extended run time.  Currently trying to use some of the high density Multistar LIPOs from HobbyKing - made up of 2 x 6s1p 10AH batteries (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=56845), to make an overall 6s2p 20AH system... although I'm a little worried that I didn't adequately consider the space available on the 12.5" bike... we will see.  

 

Can you guys advise me on safety - I want to get this right with children riding around on top of LIPOs.

 

Overcharge - I will use a computerized, higher end LIPO charger from HobbyKing, and charge the batteries without removing them from the bike (please comment if this is a terrible idea).

 

Overdischarge - I will use a cell-monitoring voltage alarm on the balance cable for the whole battery.  I would eventually like to get something that cuts off current at a certain voltage - but I don't think this is necessary for version 1.

 

Physical damage/short-circuit - This is the main gap in my plan.  I like Gwhy's suggestion of a vented aluminum box.

 

I do not really understand the use of the LIPO bags for on-bike use.  The batteries we are talking about are in the range of 15-20AH (huge amount of energy!) and a fire while on the bike will (in my reckoning) never be contained, in almost any way by a LIPO bag (similar to considering a motorcycle - you don't want to undergo the scenario where you light all the gasoline on fire and then try to contain it - you're better trying to prevent the fire from starting).  Therefore, I think (please disagree/give me your take) the main goal is to prevent a fire from starting - i.e. prevent short circuit (careful with the wires) and prevent physical damage (hard case).  

 

Fitting a hard case into the 12.5" OSET chassis is going to be hard I think - I may instead want to try to find some aluminum/steel panels that I can fit to the sides of the bike to prevent anything from poking into the under-seat/battery area.  I do not yet know where to source such panels or how to have them shaped (might have to get an angle grinder or something).

 

Short circuiting the wires also seems concerning - e.g. let's say I set up a voltage display or a watt meter on the handle bars - in the event of a crash let's say the wires get crushed because they're in a more exposed area on the bars or wherever they are routed to get to the bars.  My understanding is that shorting out the balance leads like that has the potential to produce a fire - but maybe slower due to the smaller gauge wires.  My thinking so far is: only put battery-connected accessories like that outside the battery compartment if necessary (e.g. maybe the watt-meter goes inside the compartment and the volt meter goes on the bars), protect the wires by using heavy gauge wire (although this may increase how much current could be transferred in the event of a short?), in the event of a crash teach/help the kids to get away from the bike quickly and then do an inspection.  

 

Would love advice! Thank you!

 

Will

[gwhy]

Hey guys,

 

This thread has been super valuable to me - thank you - particularly @gwhy and @betarambo - I am doing a conversion for a 12.5" OSET right now and will then do a 16" conversion.  My main interest is extended run time.  Currently trying to use some of the high density Multistar LIPOs from HobbyKing - made up of 2 x 6s1p 10AH batteries (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=56845), to make an overall 6s2p 20AH system... although I'm a little worried that I didn't adequately consider the space available on the 12.5" bike... we will see.  

 

Can you guys advise me on safety - I want to get this right with children riding around on top of LIPOs.

 

Overcharge - I will use a computerized, higher end LIPO charger from HobbyKing, and charge the batteries without removing them from the bike (please comment if this is a terrible idea).

 

Overdischarge - I will use a cell-monitoring voltage alarm on the balance cable for the whole battery.  I would eventually like to get something that cuts off current at a certain voltage - but I don't think this is necessary for version 1.

 

Physical damage/short-circuit - This is the main gap in my plan.  I like Gwhy's suggestion of a vented aluminum box.

 

I do not really understand the use of the LIPO bags for on-bike use.  The batteries we are talking about are in the range of 15-20AH (huge amount of energy!) and a fire while on the bike will (in my reckoning) never be contained, in almost any way by a LIPO bag (similar to considering a motorcycle - you don't want to undergo the scenario where you light all the gasoline on fire and then try to contain it - you're better trying to prevent the fire from starting).  Therefore, I think (please disagree/give me your take) the main goal is to prevent a fire from starting - i.e. prevent short circuit (careful with the wires) and prevent physical damage (hard case).  

 

Fitting a hard case into the 12.5" OSET chassis is going to be hard I think - I may instead want to try to find some aluminum/steel panels that I can fit to the sides of the bike to prevent anything from poking into the under-seat/battery area.  I do not yet know where to source such panels or how to have them shaped (might have to get an angle grinder or something).

 

Short circuiting the wires also seems concerning - e.g. let's say I set up a voltage display or a watt meter on the handle bars - in the event of a crash let's say the wires get crushed because they're in a more exposed area on the bars or wherever they are routed to get to the bars.  My understanding is that shorting out the balance leads like that has the potential to produce a fire - but maybe slower due to the smaller gauge wires.  My thinking so far is: only put battery-connected accessories like that outside the battery compartment if necessary (e.g. maybe the watt-meter goes inside the compartment and the volt meter goes on the bars), protect the wires by using heavy gauge wire (although this may increase how much current could be transferred in the event of a short?), in the event of a crash teach/help the kids to get away from the bike quickly and then do an inspection.  

 

Would love advice! Thank you!

 

Will

Thanks for the high five :-) ..

 

HK chargers are ok and when balance charging a battery will make a 97% reliable charging setup, the lost 3% can be down to user error, faulty charger or incorrectly setup charger.

 

the balance taps/plugs are the weak point on these batterys they are not very robust also the balance wires are quite fragile so this is the biggest point of failure.  so you need access to the balance taps if charging on the bike and keeping the plugs protected when bike is in use.  Personally I would not do on bike charging ... if something should go wrong then you will loose the bike if its not contained.  its easier to put just the battery's in a fire safe area to charge than the whole bike.

 

 

lipo alarms are a very good idea but comes back to physically connecting them to the balance plug , the plugs/wires are fragile.

 

A hard case/box is a very good idea and will protect from physical damage but never---never---never put them in a strong sealed box ,  the box needs to be vented .. I have been using army surplus ammo boxes ( with vents ( very important )) to store/use and charge my batterys .. they are cheap and available 

 

charging sacks are designed for 1 battery in each sack and each sack needs a lot of free space for it to be effective. 

 

fit a main fuse (40A+ depending on oset model, dont use a blade fuse) as near to the battery as possible on the main discharge lead of the battery this fuse should stay with the battery even if the battery is removed from the bike, this will protect from shorts whilst on the bike and when its removed for what ever reason. do not run a watt meter upto the handle bars , this increases the high power wire lengths which cause a voltage drop also it increases the likely hood of a short happening , keep a watt meter as close to the battery as pos as it goes inline between the battery and the controller , voltmeter on the handle bars is fine , but fit a small fuse inline with it as near to the battery as possible.

 

the balance wires are thin but this is sort of a good thing,, should a balance wire short to another the wire acts like a fuse and normally burns through ( but never assume this will happen ) the 3 batterys that I have been asked to look at where the balance wires have shorted have all just blown the actual wire.

 

A main fuse if positioned in the circuit well will protect the batterys and the wiring from a short as will a small fuse for a voltmeter . 

[will barley]

Thank you for the advice gwhy - really helpful.

 

I hear you on the weakness of the balance taps - I will have to think of something there.  I was intending to use them a lot (balance charge every time and use for volt meter / volt alarm on the bike).

 

Main fuse is a good idea - can you recommend any good place to get the type of fuses (40A and the small one) you recommended?  Why wouldn't a blade fuse work?  I guess this means I should remove the 10A blade fuse that comes inline with the OSET SLA batteries.

 

On that, should I expect to draw more amps from these batteries than I was when using the OSET with the SLAs?  I assume the OSET is drawing less than 10A constant if it's got a 10A fuse inline.  With the batteries I am hoping to use (Multistart LIPO 2(parallel) x 6S1P 10AH = 6S2P 20AH) I am expecting them to put out about 40A continuously (rated at 10C, but in an earlier post you said to consider them 2C * 20AH = 40A continuous).  I am guessing that this is sufficient since, judging only by the 10A fuse on the OSET, but I am wondering if I should expect more power out of the bike with this set up? e.g. on a hill where it might climb slowly should I expect a greater amp draw and faster acceleration up the hill?

 

Thank you again-

Will

[gwhy]

yes I would balance charge every time just for the fact that the charger will only charge the battery if all the cells are ok and will also warn you fir there is a problem wiht the individual cells.  The small blade fuses at around 5A start to warm up and this constant warming up and cooling down messes with the blade fuse holder so you start to get a bad connection to the fuse then its just down hill from there .. you can end up with a melted fuse holder and still a bad connection.  the maxi blade fuse/fuse holder is much better as there is more mass so it remains cooler so it not so effected .. strip link/midi fuse holder I have found to be very good and dont suffer from the heating and cooling effects.  ebay is always good for getting these sort of things i.e  http://www.ebay.co.uk/itm/Strip-Link-Midi-Fuse-Holder-with-50A-60A-80A-100A-Fuses-for-Car-Truck-Van-/171248103184?var=&hash=item27df2eaf10:m:mYBx3QtIVk71W-qroogCW9Q

 

for the small fuse a blade fuse/fuse holder will be ok or someting smaller like a mini blade fuse/fuse holder  http://www.ebay.co.uk/itm/In-Line-Mini-Blade-Fuse-Holder-with-6-Fuses-12V-30A-Car-Automotive-/262131520883?hash=item3d08419573:g:YTwAAOSw3ydV3v76  5A fuse or lower will be fine.

 

the bike will perform better with the new batterys, it will have a little more power and a little more top speed, I would have thought it would be a 20A minimum fuse as standard maybe even 40A fuse..

 

the new batterys will be able to output maybe 200-300A if shorted together ( you dont want to do that!! ) , just because i said real life only 2C dont mean to say thats all they will put out, 2C is what I tested them for that give the rated capacity and voltage and they will not warm up at a constant 2C , a constant 5C starts to get a bit of warm in them so its more to do with looking after the batterys but even a 2C 20Ah battery will be fine on a small bike and should give a long service life.  24v @ 40A is around 960W and the motors at not even rated for that. The controller will limit the current to I tihnk around 40A anyway ( ok it may be a bit lower on the 12.5 but on the 16 its 40A ).

 

you will get better pull on hills just because of the fact that the voltage will not sag as much as sla's  ,  e.g a sla 24v @ 40A will sag down to maybe around 16v and 16v @ 40A is  around 640W  but lipo will only sag around 2v max so 22v @40A  is 880W  these are just examples as it depends on age of the sla's and how cold the weather is and what the current limit is set for on the controller.

 

 

[thepod]

Great source of information here.  Thanks to everyone that has posted.   I've just bought my son his first Oset and I'm excited to convert it to a LiPo or LiFePo4 battery .  

 

 

Has anyone looked into this option?

 

Assuming it would fit in a Oset 16 24V it seems like a pretty easy turnkey solution for a lighter battery and better range.  Having read the entirety of this thread (several times) I'm not sure I want to venture into LiPo simply because I'd rather not have to fuss with battery charging and storage etc.  I'm not too worried about LiPo safety on the bike, but the charging regimin for LiPo seems laborious.  

[gwhy]

The pack in the link will not supply enough current for reliable operation,  The bms has a spec of constant 20A peak 35A, for a 16 I would guestimate you would need at least constant of 40A peak 80A ( but this still may not be enough , its a gamble).

 

The storage issues will be the same for any soft pouch Li chemistry , and charging can be as simple as turnkey ..   

 

 

if you do a lifepo4 36v battery as in the same voltage as 3x 12v sla batterys then the standard 36v charger will work but you must have a bms

 

you will need 12 lifepo4 cells to make the 36v battery

 

the easiest way would be to buy 3 of these http://www.hobbyking.co.uk/hobbyking/store/__14074__ZIPPY_Flightmax_8400mAh_4S2P_30C_LiFePo4_Pack.htmlthat will make up one 8.5ah 36v lifepo4 battery and source a suitable 12s bms tehn you just wire it together

 

edit:

just been looking for a suitable bms .. and found this  http://www.ebay.co.uk/itm/12V-90A-Battery-Protection-BMS-Board-w-Balance-for-4-Packs-LiFePo4-li-batteries-/171928485718?hash=item2807bc7f56:g:QoIAAOSw9N1VkUl2

 

if you buy 3 of the above bms then this will be cost effective.. you would need to fit a 4s bms to each battery.