Hobby king multi star on offer

[danielrlee]

Cells in a healthy lipo pack should stay balanced within a couple of 0.01v of each other if you don't discharge past the 3.65v per cell point. Not that it will matter too much if you are only using two separate packs and intend on balancing every charge. Something to think about though for those of us bulk charging at full pack voltage without a BMS!

 

[awol]

Two chargers and split the batteries for charging is no problem. 39€ per charger, 78 € in all.

If you decide on 2xchargers there's also the cost of 2 power supplies too which has the benefit of charging twice as fast, and some cheap lipo alarms/monitors

 

[danielrlee]

The alternative to balance chargers is a BMS and bulk charger. With this solution you're left with a simple plug and forget type charging setup.

 

[awol]

The alternative to balance chargers is a BMS and bulk charger. With this solution you're left with a simple plug and forget type charging setup.

I would be interested in one of these, could you recommend any bms's suitable for use with lipo's which you may have used?

 

[anotherkiwi]

Thanks all for very useful feed back!

So if I stick with 10/4 = 2.5C is that for the packs wired in series Amps?

I think at 150 € I am going to play with a 10.4 Ah set up which would mean 25 Amp output at 2.5C

 

[Nealh]

Reading the Sphere the c rating is regardless whether serial or parallel or connected S & P, any of the 10c rating will be capable of 25amp draw or 2.5c. The thinking over their is that packs are best used paralleled in larger packs for a variety of reasons; packs less likely to get hot in use , balancing is better controlled when hooked up together, internal resistance (IR) remains lower, discharge on larger packs is kinder.

 

[KirstinS]

AK the folks over on the Sphere are saying that the C rates claimed by HK are ambitious, the Sphere guys reckon C rates are about 1/4 of the claimed rate. Not sure about LIHV but std lipo discharging to 3.1/3.2v is close to the cliff where they fall away very quickly, I currently set my alarms to 3.5v under load which settles down to 3.64 - 3.74 resting voltage and they appear to be staying balanced with no pack cells differing more then 0.016 volts.

From my own experience they fall offthe cliff at 3.1v

I set my alarms at 3.4v which with my setup gives me a mile in the tank (average)

 

[KirstinS]

The packs are 10 C which is about 100 Amps constant discharge. What are the consequences of pulling up to 18 A peak:

- little to no sagging?
- less heat (I am pretty sure about this)
- longer pack life?

I have run my packs as booster batteries on 36v bpm motor run at 50.4vnominal (48v mini controller at 15a)

I have done so for years using various 18650 packs of various makes and models.

When I changed to Lipo the lack of sag and instant torque was hugely apparent

 

[danielrlee]

I would be interested in one of these, could you recommend any bms's suitable for use with lipo's which you may have used?

As hinted in my previous post, I run my lipo packs without any BMS protection, sometimes referred to as 'bareback lipo'. This isn't a setup that I would ever recommend to anyone, but is perfectly manageable if lipo is kept within certain operating parameters. If these have to be explained, running bareback is not for you.

http://bestechpower.com is the goto source for BMS systems. They offer a huge range but I *think* require a minimum order quantity of two units.

BMS's can also be purchased from https://bmsbattery.com/82-lipo and from Ebay/Aliexpress anongst others. I'm not however currently aware of any UK sources.

 

[anotherkiwi]

Yesterday I went over to youtube to check out "lipo fire". If I don't crash at 70 km/h, if I don't over-charge, if I don't discharge at 20C continuous, if I don't mess up connections at charge time, if I don't fully charge before storing... I think the risk is pretty minimum. I will not be hitting the packs with an axe or a hammer any time soon... Charge to 41.5 V, discharge alarm set to 35.5 V (from my ES reading that should allow up to 600-800 charge cycles if I balance charge every time). At home stockage in storage mode: in the oven with a smoke alarm, extinguisher on hand. I know, don't open the oven door unless things get out of hand - I was a volunteer fireman back in the day. Oh and control the quality of the packs on arrival, if there is a duff cell break one of the balance leads at the plug and send it back because HK doesn't accept returns if one cell is slightly off...

That cleared out of my mind, this morning I made lots of paper models of packs (as an ex industrial design student first reflex = make a model) to see what is the maximum I can fit in the tiny triangle of my next bike. I have three options:

- I could fit 1 x 20000 mAh 6S + 1 x 20000 mAh 4S in series for 20 Ah at 37 V
- or 2 x 8000 mAh 6S + 2 x 8000 mAh 4S in series then parallel for 16 Ah at 37 V
- or 2 x 5200 mAh 6S + 2 x 5200 mAh 4S in series then parallel for 10.4 Ah at 37 V and make two packs and swap over when first is empty
- price difference is less than 10€ whatever the choice

I will be setting maximum Amps to 18 on the controller so under 1C for the first, just over 1C for the second and about 2C for the third. Experts opinions on this are welcome!

The battery box will be in ply because wood is what I do best. Interior will get lavish coating of M1 fire retardant paint and the ply should better insulate from external heat than some of the plastic boxes I have seen. Eventual internal heat build-up to be evacuated by a vent (Reminder: do not park in the sun).

 

[awol]

When I was checking out lipo's before getting into them I also checked ytube for lipo fire. At first I was worried but then realized most were caused on purpose by misuse, a bit like a video of putting a match to a can of petrol to see what how much it would flare up.
I've made up a 12s in a plastic tupaware type tub and a 10s wrapped in foam type packaging and wrapped in ducktape, with the idea they won't really get hot at the charge/discharge rates I will be doing them at, but I haven't started regularly using them yet.

 

[derf]

Yesterday I went over to youtube to check out "lipo fire". If I don't crash at 70 km/h, if I don't over-charge, if I don't discharge at 20C continuous, if I don't mess up connections at charge time, if I don't fully charge before storing... I think the risk is pretty minimum. I will not be hitting the packs with an axe or a hammer any time soon... Charge to 41.5 V, discharge alarm set to 35.5 V (from my ES reading that should allow up to 600-800 charge cycles if I balance charge every time). At home stockage in storage mode: in the oven with a smoke alarm, extinguisher on hand. I know, don't open the oven door unless things get out of hand - I was a volunteer fireman back in the day. Oh and control the quality of the packs on arrival, if there is a duff cell break one of the balance leads at the plug and send it back because HK doesn't accept returns if one cell is slightly off...

That cleared out of my mind, this morning I made lots of paper models of packs (as an ex industrial design student first reflex = make a model) to see what is the maximum I can fit in the tiny triangle of my next bike. I have three options:

- I could fit 1 x 20000 mAh 6S + 1 x 20000 mAh 4S in series for 20 Ah at 37 V
- or 2 x 8000 mAh 6S + 2 x 8000 mAh 4S in series then parallel for 16 Ah at 37 V
- or 2 x 5200 mAh 6S + 2 x 5200 mAh 4S in series then parallel for 10.4 Ah at 37 V and make two packs and swap over when first is empty
- price difference is less than 10€ whatever the choice

I will be setting maximum Amps to 18 on the controller so under 1C for the first, just over 1C for the second and about 2C for the third. Experts opinions on this are welcome!

The battery box will be in ply because wood is what I do best. Interior will get lavish coating of M1 fire retardant paint and the ply should better insulate from external heat than some of the plastic boxes I have seen. Eventual internal heat build-up to be evacuated by a vent (Reminder: do not park in the sun).

I angsted over many models too - even bought cash boxes and tried to convert them: then I had an epiphany that really helped: just wrap it in fat bubble wrap and stuff it in a carrradice camper saddlebag ( I have yet to come off a bike in away that damages the saddlebag area significantly). it works great for me

 

[footpump]

I am reading this thread with interest, but getting bogged down with charge/discharge rates series/parallel.
I have 10.4ah bottle battery 36v-250 w and new bottle battery but they have totally different connections on mounting frame.

I was thinking perhaps I could use a single lipo pack and connect up to controller when 10.4 battery is depleted for a longer journey.

heres where I am confused hk 6s 1600ah lipo £85 is the capacity similar to say 15ah bottle battery but I believe its 48v rather than 36v .

is there a lipo pack 36v that would suite my needs and if possible exactly what would I need
I am thinking its easier to carry a single lipo in frame bag /bottle cage than a bulky battery.

ps do hk do jst to bullet connector leads

 

[anotherkiwi]

10S = 36 V go back to the beginning and read again! so you need 2 x 5S or 4S + 6S to make a 37 V battery.

 

[anotherkiwi]

I angsted over many models too - even bought cash boxes and tried to convert them: then I had an epiphany that really helped: just wrap it in fat bubble wrap and stuff it in a carrradice camper saddlebag ( I have yet to come off a bike in away that damages the saddlebag area significantly). it works great for me

I am going to first off build a 10.4 A pack to get the hang of things and it is going to live in one of my pannier bags in a nice IKEA plastic box for perforation protection with a bit of foam to stop the individual packs from moving around.

 

[anotherkiwi]

Been reading lots of threads over on ES about Multistar packs and it always comes down to 18650 cells are better bang for the buck. I think we are living in parallel universes. The NiHV packs are not the cheapest Lipo packs on the market but compared to a 10.4 Ah bottle battery sold in Europe (importing batteries from China is not my tasse de thé...) they come in at around half price, less than 2/3 with the charger and bits and bobs. So even if the pack only does a year it is still equivalent in cost.

The posters all seem to have had puffing incidents and some have had fires but... if you are feeding tens of Amps to a 2 kW+ motor at speeds closer to the speed of sound than 25 km/h you are asking for issues IMHO.

The hills around here are not being kind to my Samsung 26F cells I doubt that I shall get more than 2 years from my bottle battery. The sagging is becoming annoying and I am only asking for 1.5C from it! I would love to have the latest generation cells in my bottle capable of 10C but at $320 + cost of having someone re-cell that is not going to happen soon.

One of the threads mentions parallel connection of like voltage Li-Ion and Lipo packs to get the best of both worlds, have any of you played with that?

 

[Nealh]

ES does make for interesting reading.

 

[anotherkiwi]

HEADS UP!

The 16000mAh packs seem to be down in price, they are cheaper than both the 12000 and 10000 for me today.

129.79€ for a 16 Ah 37 V battery with 2 lipo alarms and 1 series wire!

 

[danielrlee]

HEADS UP!

The 16000mAh packs seem to be down in price, they are cheaper than both the 12000 and 10000 for me today.

129.79€ for a 16 Ah 37 V battery with 2 lipo alarms and 1 series wire!

Woah, that's a great price! I'm waiting it out until the summer then I plan to buy some 20000mAh packs. Haven't seen any discounts on them like this though.

 

[danielrlee]

Just noticed that at current prices, the 10000mAh packs match the 16000mAh on a Wh/£ basis. Not quite as convenient, but more flexible for filling small or awkward shaped spaces.

EDIT: Also, the 4S Multistar packs are even better value than the 6S packs.

You can fit 6 4S 16000mAh packs in an EM3EV triangle bag, giving you 32000mAh @ 12S, with a 'real world' draw of 80A at 2.5C. I can't think of a better way to do this for under £220.

I might have to re-think my plans for 20000mAh packs and jump on these now.