Gotway Mcm4 battery

[milkmalks]

Hello, does anyone know where I could buy a 340wh battery pack for my gotway mcm4? I'm intending to increase the range as 15-20km isn't enough. I already have a 340wh pack and willing to buy one more. So if anyone knows where I can buy one, please post below! -I'm from Canada

[Samppa]

Just sold mine original 340wh battery some time ago. I had same problems. Low range and also little too big voltagedrops when accelerating. I tried to find another 340wh pack but did'nt find any reasonably. I decided change to lipo batteries. They give more amps than li-ion packs wich was one reason to chose them for me. I also have worked with them in years because i have rc multicopters and planes. Now i have four 4S 10Ah lipos in a serial connection. When charging i normally use gotway original charger and just monitor cells with external balancers/battery doctors. About ten charges now and not need to balance cells yet. Just before charging all cells are usually in perfect balance. After charge they are between 4.18-4.20v/cell. Im not sure is it because low charge/discharge amps or why they stay in so perfect balance but it is only good.  I have also good balance charger. I charge batteries separately or in paraller with it if they go unbalance. All batterywires comes to one side which makes monitoring easier. I removed skrews and made quick hitch for side cover. 

Lipos works like a dream. Voltage didn't drop even at hard accelerates. And now i can drive about 40km fast driving. But they need some knowledge and care. I dont recommend lipos if you need carefree solution. They give extra performance but need some extra care too.

[US69]

On ‎07‎.‎07‎.‎2016 at 0:39 AM, Samppa said:

Just sold mine original 340wh battery some time ago. I had same problems. Low range and also little too big voltagedrops when accelerating. I tried to find another 340wh pack but did'nt find any reasonably. I decided change to lipo batteries. They give more amps than li-ion packs wich was one reason to chose them for me. I also have worked with them in years because i have rc multicopters and planes. Now i have four 4S 10Ah lipos in a serial connection. When charging i normally use gotway original charger and just monitor cells with external balancers/battery doctors. About ten charges now and not need to balance cells yet. Just before charging all cells are usually in perfect balance. After charge they are between 4.18-4.20v/cell. Im not sure is it because low charge/discharge amps or why they stay in so perfect balance but it is only good.  I have also good balance charger. I charge batteries separately or in paraller with it if they go unbalance. All batterywires comes to one side which makes monitoring easier. I removed skrews and made quick hitch for side cover. 

Lipos works like a dream. Voltage didn't drop even at hard accelerates. And now i can drive about 40km fast driving. But they need some knowledge and care. I dont recommend lipos if you need carefree solution. They give extra performance but need some extra care too.

 

 

 

 

Very good mod!!!

 

Can you perhaps Show me/us some links what charger/balancers Controllers are needed and where to buy them?

Perhaps also for the batteries? And something about the costs?

[Samppa]

I start by planning a suitable configuration. First I measured the battery compartment (its 180x143x40mm), same size on both side. After that i search batteries which will fit. I've bought a lot from Hobbyking so i searched in the first instance from their store. First idea was to buy two 8S lipo. But i didn't find suitable models. And my existing lipo balance charger can charge only 2S-6S batteries. So i decided to buy four 4S batteries. I found two suitable models:

Graphene: http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=89635

+ little better C-rating (but less capa so not big difference in amps) 

+ Thinner (separate BMS will fit on top of it)

+ A little more advanced technology. May last longer (more cycle lifes)

- Expensive

- Less capasity

I decided to chose Multistar 10Ah http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=65272

+ More capasity

+ Cheaper (53€ * 4 = 212€)

- Less C rating but 10C is enough for EUC use (i get 100A constant and 200A for 10s)

Multistars comes with XT90- connectors. I changed em to XT60 and i also extended two battery cables (so they reach battery compartment at other side). For balance leads i used extension cables. I wanted all connections at one side because it's easier to monitor cells and charge batteries separated if needed. Batteries sits very firmly in housing.  I fastened them with high quality velcro (first photo). It's still easy to remove batteries if needed, but they dont loose accidentally. I made my own serial connection cable (second photo). It has connector for four batteries, chargeport and motherboard. 

Total costs were somewhere between 250-280€ (batteries, xt60- connectors, battery medics, 12awg lead, locks for cover etc.). I had balance charger ready so not need to buy it. it's otherwise might not be absolutely necessary. Soldering iron was also needed but i have one already.

I have used battery medics only in monitoring. If i need to balance packs i use my existing balance charger. https://www.hobbyking.com/hobbyking/store/__31468__HobbyKing_8482_Battery_Medic_System_2S_6S_EU_Warehouse_.html It's possible to balance packs with battery medics but it's important that all four batteries are in same cell voltages. Its easy to balance one pack cells with battery doctor but harder to try fit all four packs in same cell voltages. Not impossible however. For example i can set discharge voltage to 4.1V/cell and then discharge all batteries to that. Balance charger themselves does not pay much (cheapest ones are about 15-20€).

As i wrote earlier, packs stays in very good balance even though they are charged by original gotway charger. You can charge at least ten times before some cells are very very slightly unbalanced. So using lipos are rather carefree but just in case i always check the cell voltages before charging. Because of that i installed quick relase system in side cover.

Today i charged batteries with my balance charger. it was not even necessary, but I just wanted to try it. I used paraller charging board. With it i can paraller charge all packs at same time. But now i charged them in pairs. (last photo). They weren't unbalanced bad (differences between cells were max 0.02V). I suspect that cells can remain in balance at least 10-20 charge times with original charger. Maybe even more.... I'm going to figure this out.

Pros for lipos:

+ Range is increased more than I had expected (lipos give lot of power until theyre almost empty)

+ I can accelerate as hard as i can and battery bars does not drop at all (no voltage drops because batteries can supply enough amps)

+ Batteries stays much more cooler than li-ions. Theyre not pushed in limits so they do not heat up and can last longer

+ This is weird one. I have only third speed alarm in use. At original battery it triggered when real speed was about 28kph. Now when lipo is charged more than ~60% last alarm comes at 30kph. I dont know why..

Negatives

- No BMS board so i have to monitor cells. Not big problem..

[Pasi]

Today I connected another 340Wh battery I bought from @Samppa (thanks again). I had to wait this long before I got XT 60 connectors I ordered from Aliexpress. In Finland they were sold out in every place. 

So now I have 680Wh, I drove this evening 14km and app show drop from 97...... to 70% battery. What is the final battery voltage you can go? I think voltage is more precise than apps % because you dont know how they are programmed to show it.

I tried to put it in my backpack too, but now it is very (too) heavy.

[Samppa]

Good job. With lipos i try to stay over 58V. Lipos may suffer if they are drained too empty. After ~16km my app shows somewhere around 60% if i remember right. I'll check it today when i go to home. I came to work today by euc. Now 8km driven and 85% battery left (64,4V). It was good tailwind at morning. It's interesting to hear how far u can drive with original batteries.

 

 

[US69]

@Samppa

i really like this solution!!

if i ever run into batterie problems i will also try lipos....

[Samppa]

Okay, 20km quite fast driving behind. It was headwind now when I drove home. App shows 58% battery level (61,5V). Newer app does not show volts but it shows 60% charge level. I shut euc off and measured cells by battery medic. Cells were between 3.88-3.89V and total voltage 62V. Voltage was little higher because euc was shut off and battery has no load. I know from experience that next 20km does not drop the battery charge level as much than first one (as a percentage of app).

[Pasi]

7 hours ago, Samppa said:

Good job. With lipos i try to stay over 58V. Lipos may suffer if they are drained too empty. After ~16km my app shows somewhere around 60% if i remember right. I'll check it today when i go to home. I came to work today by euc. Now 8km driven and 85% battery left (64,4V). It was good tailwind at morning. It's interesting to hear how far u can drive with original batteries.

 

 

So yesterday I rode 14km and today 20km(sports tracker) , (21,2km GW app) and now app shows 37%, 58,7V, temperature 53C.

[Samppa]

I tested how far i can rode on a single charge. Yesterday i rode 20km. Today i did 7,9km, 9.9km, 6,8km and 5.7km trips. In total 50,3km.

After 38km i had 41% / 59,3V left. After 48km 33% / 58,15V and after 50,3km 32% / 58,07V. Temps remain below 50C (41-46C after trips)

Batteries still have charge remaining maybe even to ride 10km trip. But i want to spare batteries and i'm not going to test it. Good to know however how long i can drive if necessary. Average speeds were over 20kph. Not much stops and pretty flat terrain.

 

edit: After ~30min cooling down i measured cells. 3.67-3.68V left = 58,85V total. So still juice left ;D It seems to be pretty safe to rode 50km on a single charge. I really love these lipos (photo of one battery stats below)

edit2: Sometime i try to do a one long 50km trip and record logs. I'll publish gw app log and endomondo stats then

edit3: Now I recorded only one log. It's from first trip today (7,9km). In log total distance is 8,2km but 7,9km is real distance measured by gps. You can download log here. At start battery level were about 60%: https://dl.dropboxusercontent.com/u/1669036/euc/data-160720-072309.csv

[Samppa]

Battery charged again. It took about 5,5h by stock charger. Charger used 0,82kWh (820Wh) from electricity network. I don't know what is charger efficiency, at least it warms up pretty hot. Charging current is 1,75A (according to the charger specs). So 5,5h*1,75A = 9,62Ah. 9,62Ah*67V=644Wh. I'm pretty sure that actual amount is closer to 8Ah, referring to voltages before charging. After 5h of charging charger dropped current to half. It took 0,66A from socket at beginning. After 5h of charging i check and it was dropped to 0,33A. When green led turned on it still take 0,13A