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Oset Batteries Lithium (LiPo) Conversion Directions


betarambo
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Hi Frogger,

Ossa and Oset, perfect setup. Same here :)

Just "upped" the OSET battery capacity to 25AH (2.5 times standard OSET), I'm guesstimating that should give me a full days trial without worrying about hitting low voltage. Its a snug fit in the battery box.

I've ordered an adjustable low voltage alarm from HK.

Before I upped the capacity I did manage to discharge the LIPOs to below 3.6v which confused my charger into thinking they were 4S not 5S. Manual trickle/tickle on Nimh got them about 3.6 and back to 5S and back to LiPo charge, guess you know this!

It occurred after about 2+ hours, my son suddenly noticed the power meter light on the throttle went from 3 to 1 seemed to miss 2, and we were at 35.8v.

An aside - not for this thread but a couple of significant other upgrades is to put a mountain bike shock on the rear, 6" or 6.5" with a bit of welding made all the difference on rock steps and I raised the bars with a raised adjustable clamp.

i am curious about welding on these bikes... do you remove ALL electronics first? Do you use any type "anti-zap" device that clamps to the frame to protect electronics? Do you just disconnect the battery?

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i am curious about welding on these bikes... do you remove ALL electronics first? Do you use any type "anti-zap" device that clamps to the frame to protect electronics? Do you just disconnect the battery?

Moved my response to the Rear Shock Thread

Edited by NineFives
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i read all the time about these needing more attention.. but how much attention? what happens if the voltage runs too far down does it kill the battery? i wouldnt mind fitting one of these as its a pain having the bike die out so quickly

They behave just like normal batterys but more care is needed to look after them, if a cell is run down below the safe limit then this can damage the cell and you can risk ( at the very worst) having a lipo fire when you come to re-charge them. there are 2 main rules for lipo , never over discharge them and never over charge them. Special chargers are needed for lipo that take care of the over charging problem and you can get cell monitor alarms that warns if they cells are becoming to discharged in use or you can get a total BMS ( battery management system ) that will shut the battery down if any of the cells are getting to low or if to much current is drawn for the battery. The initial cost converting to lipo is expensive but well worth it. If a total newcomer wanted to start using lipo I would highly recommend never charge the battery on the bike and also charge the batterys in a safe place i.e i in a fireproof box and defiantly not in the house but this should also apply to any high density battery ( SLA is not a high density battery ).

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i read all the time about these needing more attention.. but how much attention? what happens if the voltage runs too far down does it kill the battery? i wouldnt mind fitting one of these as its a pain having the bike die out so quickly

Jonny - The best thing to do is have a conversation with folks in a helpful model shop about LiPo attention and maintenance. These guys really understand LiPos - that said - I think Frogger has some experience in that department - look back through the threads - his charge setup is awesome! LiPo safety has moved on with safe (and not expensive) chargers that have time/voltage/load/temp cutoffs. There is no doubt, there is the potential for fire that you do not get with Lead Acid, handling the batteries/charging etc is the responsibilty of an informed adult but it isn't nuclear bunker stuff. The biggest risk I see is grit or a stone getting into the battery case and puncturing a cell - that equals a fire - so protect them well.

If you do run the battery down to below 20-30% you may not kill the battery but you are in the pain in the A place, you need to nurse them back up with some TLC (or get Froggers recover setup). The prognosis is fair that they will pull through, but there may be complications meaning replacement - best not to go there - hence the low voltage alarms.

I understand the frustration on battery life, I love the bike - right size and simplicity for my kids (5 and 8) so bit the bullet and have spent about 300 quid on LiPos - but I now have 5 hours high voltage running (about 5x what I used to get) with the batts in a sealed metal case and it all weighs less than the 3 lead acids.

Edited by NineFives
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Do they get hot at all? I noticed one person sealing them with lots of tape, bubble wrap and more tape.. I thought this in itself could cause a fire with heat?

Lipo batteries do/should not get hot. At extreme performance draw (performance flying or RC car racing) I have felt packs increase in temp when pushed to their limits but only ever warm to the touch, never fire warm, never ever the sort of heat you would feel a NiCd or NiMH get to during charging. Lipo batteries should never exceed 140F/60C.

A lot of manufacturers now encase their lipo packs in hard cases to protect them against knocks and so one wrapped with bubble wrap or tape isn't a problem.

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Hi, you Lads on here post some fantastic info,

Reading all the posts on this topic is great info in to these little bikes,just got my kids the oset 16 24v 2011,they just love it, reading all the lipo upgrade info and looking at all the pics has me a bit confused,

the batteries in the bike we got are 12V 14AH / 20HR

can anyone recomend,the best set up or some help in building a set up, iff someone is building any would be great to hear from you,

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Hi,

1st - You want 24v - each LiPo cell gives 4.2v fully charged 3.6v lowest working voltage. So 24/4.2 = 5.7 so 6 gives 25.2v and when depleted to 3.6v you get 21.6v - that will work - so you need to use either 6S1P (6 cells in series giving 25-21v) - you could use 2 sets of 3S1P joined in series - same thing.

2nd - you need the capacity AH to keep the OSET running for long enough - your current setup is 14AH. Each 6S1P or 3S1P battery comes in many different capacities - eg 5000ma or 8000ma. 2 x 5000ma in parallel = 10AH logically 3 x 5000 will give you 15AH but you cannot fully deplete these suckers so you need to build 20AH giving 14AH usable (leaves 30%). If you pockets are deep enough you can add another bank so would run twice as long. I recommend stick with 4 batts to begin with.

3rd - Each battery is rated in C eg 15C 25C etc - this is to do with the battery's ability to take load either discharge or charge, OSETs are gentle in this regard compared to some RC model use so I was advised earlier in this thread 15C is fine - the higher the C the more expensive the battery.

4th - Look at the sizing so that after being protected the batteries fit in the battery compartment well protected and tidy Hobby King (Hong Kong) website gives the dimensions so tape measure and paper and do the sums how to fit them in - that may be when you decide between 3S1P and 6S1P and also whether 5000 or 8000ah (the 8000 will be bigger (longer I think). Lots of flexibility here :)

5th - You need the connectors to connect the batteries in parallel 6S1P or parallel and series if 3S1P

6th - Chargers - I'm happy with my chargers - see my earlier shopping list - 3 would mean that you can charge each battery at the same time - less faffing about but 1 would suffice. Don't forget a 12v - 18V power supply - computer power didn't work they are 18.5v so outside charger input tolerance. I use a battery connected to a charger and also an AC to 12V converter with car plug (order the car plug power lead at the same time as the charger - they come with croc clips)

7th - I'm on the fence on changing the connectors, its a PintheA but once done pretty solid 1 way setup - ie can't accidently mix polarity, although not sure its that easy to do with the connectors they come with - Frogger didn't change and he has worked with LiPos before.

I think thats it - but its late and check everything I suggest. And remember the health warning.

Have fun

Edited by NineFives
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Depends a bit on what you want from it. I've posted some stuff above about my minimal conversion on a 24V Oset 16. I used two 5000mAh 6s batteries in parallel. While this is nominally a little less than the standard batteries, in practice it goes much further on a charge. The lead acid batteries shouldn't be fully flattened either, I suspect you don't get anywhere near the rated capacity. There is certainly room for plenty more batteries.

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7th - I'm on the fence on changing the connectors, its a PintheA but once done pretty solid 1 way setup - ie can't accidently mix polarity, although not sure its that easy to do with the connectors they come with - Frogger didn't change and he has worked with LiPos before.

NineFives is right, it really is worth changing the connectors to something that prevents shorting them out or accidentally connecting them together. Throw kids into the mix with anything and sooner or later you will have a problem. I am lucky in that my kids have learnt to stay well away from lipo batteries and their connectors and I have developed a very consistent way of working with lipo's from using them in our RC cars so this really is the first time in my life that I have just left the standard connectors on. I've never been a fan of bullet connectors.

It's been playing on my mind and I've been looking around for other suitable connectors that will prevent shorting them out. I also want a more secure and reliable way to connect my low voltage alarms. Th project is far from done, watch this space. :)

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Hi,Thanks NineFives,mikeduffy,and frogger great reading the posts and some nice photo's of your work,

so best to start off with ( 4 x 6S1P 5000 / 8000ma/ 15/25c, chargers ,various conectors and leads all from HK ),to repace 2 x 12V 14AH / 20HR,

after reading all the ups and down with charging,mantainance and saftey also talking to a few clued up people,will be cautious and learn as i go,

will be interested to read more on the low voltage alarms,do you have to take the voltage reading direct from the batts or can you get an overall reading fron the controller or the throttle ?,im new to these bikes so sorry if im way off the mark

have been in all kinds of bikes for 20 yrs and in to to nitro 1/8 scale for a few years not racing only fun,must be something on the market that can be adapted to cut off when at dangerous levels,

my 2 kids boy 5 girl 9,are light weight to say the least so i hope the will benefit with the wieght reduction and long ride time,

Thanks again

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If you want to start small, my set up with 2x5000mAH batteries and a single charger works well. I usually charge the batteries at once in parallel, you can do them separately for a balance charge every so often, but they seem to stay balanced pretty well for me. I've kept the standard connectors so I could swap the Lead acid batteries back in for extra run time if needed, but have never needed to so far. I did get a bit of range anxiety on some trails recently and have now ordered a third battery and some battery monitors.

It is easy to do in small stages and add extra batteries/chargers etc if needed later. The main downside would be possibly extra shipping costs from Hobby King, though they now have a few local warehouses. I got my latest extra battery with cheap shipping from their Australian warehouse.

The battery monitors generally plug into the balance connector on the battery pack. I ordered extension cables for these balance connectors to allow more convenient placement of my monitors when they arrive. The cable on the battery is quite short.

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