DIY battery

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So i'm thinking of going electric with the TongSheng TSDZ2 36V 250W.
Battery wise I am also thinking of DIYing it. After looking around these Vicore LiFePo4 15aH cells look like a good buy at small money


I have searched a good bit and it seems that these cells deliver just about what they claim in terms of capacity. I have decided that LiFePO4 is the way to go in terms of safety and lifetime. Price wise this is going to be about €100.00 for the cells and then about another €30.00 for the BMS. The only unknown is the cost of a half decent case which will have to be custom for these cells.

So my question is, has anyone else gone down this path and if so what was your experience. Off the bat I have no issue with using AliExpress for components, but feedback on individual sellers is always useful.

Shoog
 
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Do you know the C rating of the cells? The Chinese are notorious for claiming any amount of capacity for their cells so only trust any independant reviews and tests you have read.
 
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I have seen a few people with batteries from the same brand doing reviews. they either report spot on AH capacities or slightly under. As to C ratings I would have to check a bit more. Whats a typical 250Watt motor pulling at peak ?

Shoog
 
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It seems that they now do a 25AH cell which is almost the same size, but these 14AH cells are no longer listed on the Varicore store. This seems to indicate that these are old stock which is coming from resellers. For about another €70.00 you can get nearly the same size pack with an extra 10AH which is still a bargain. Watching some of the solar vids on these packs there was a significant jump in energy density about two years ago which came as a surprise to the testers.

Shoog
 
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A motor will usually pull much more than it's rating if the controller lets it. I've read of some 250W motors peaking around 900w. Note peaking, not continuous. If that same motor was paired with a controller only allowing 500W then that would be it's peak limit. I'd expect that figure to vary considerably from one maker to another. Many 250W motors are also labelled as 300W or 400W etc according to the market they are sold in. Legislators have zero clue and policing of rules is so poor that manufacturers exploit this laxity at will. Same motor but different sticker or stamping.

I have seen tests on 18650 Chinese batteries off ebay. Labelled as anything upto 15000 mah (the South Koreans best efforts are sub 4000 real mah for comparrison) yet the Chinese rip offs tested at around a pathetic 500 mah. Even well tested and accurately rated Chinese batteries are libel to be ripped off by other Chinese so I'd only buy from the seller that supplied the independently tested ones.
 
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I am not so concerned about legitamacy as their are brand shops on Aliexpress and those brands have been tested by people. Usually the come out 5-10% down on rating which is OK by me. They state current draw but its not in C's so I will have to look at the detail.

Have to investigate the draw of one of the Tongseng motors.

Shoog
 
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The first battery is 18A 30second draw, 12A continous which might be a bit marginal.
The 25AH battery has a continuous discharge of 50A and instantaneous of 100A.

So in every way the 25AH is the better product with an increase of height of 3cm and weight of 150g for 500g per cell, all for just €170 on the total battery. Even if its down 20% on AH spec its still a steal.

Shoog
 
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The Tsdz2 is a great motor. I have it and it rides great.
One tip, check the amount of pins. There are 2 versions. One that supports throttle and o e that doesn't. The 8 pin supports throttle. As you don't need that, than just get one without. You safe a bit of money.

The lifepo has a lower V so you need ad least 11 cells and better 12 cells.
I have seen the review of that brand and it has the capacity.
I go for the 18650 cells. I have everything for that build and I know for surten that I don't need to pay extra import tax.
Maybe I get a few cells to test them.
But I will need a new charger and bms for it as I go for that.
 
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What Ah rating are you using on your install, and what sort of range are you getting from it. I really intend to use mine with minimal assist so am really wondering if 20Ah is overkill. Still the batteries using the Variocore Cells would be about the same size and weight if I cheaped out on the 14Ah. I also anticipate about 10% overstatement of Ah on these cells so that brings me down to 18Ah or 11Ah.

Good tip on the pin count, its not legal to run throttle where I live so I really don't want it because there are liability issues in case of an accident.

Shoog
 
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What Ah rating are you using on your install, and what sort of range are you getting from it. I really intend to use mine with minimal assist so am really wondering if 20Ah is overkill. Still the batteries using the Variocore Cells would be about the same size and weight if I cheaped out on the 14Ah. I also anticipate about 10% overstatement of Ah on these cells so that brings me down to 18Ah or 11Ah.

Good tip on the pin count, its not legal to run throttle where I live so I really don't want it because there are liability issues in case of an accident.

Shoog
For lifepo4 it will be a bit lower, but it is hard to say.
The range you get out of a battery, depends on several things. Weight, speed, wind, hills, assist mode and gearing all have influence on the range.
For 18650 cells, they calculate as followed.
As a speed of 20km/h, no hills and maximum assist, you get 11 to 14km range for each 100wh.
So a 10ah battery on 36v has 360wh.
This is about 39,6km to 50,4km range. It depends on the wind, gearing and weight, what it will be.

For your lifepo it will be with a 10ah, 320wh.
This will give you about 35,2km to 44,8km range.
Also know, that because of the lower voltage, you will feel that the assist has less power.
Also, you need to adjust this in the settings, especially as you go for the 10s. The motor will else think, that the battery is low and cut off earlier. This isn't possible on the display, so you need to hack into the firmware of your motor.
Or go for 12s. As 2 cells. You also get more punch with your motor.
I only think that you will never reach that 18ah, on a 20ah. I think that it will be lower, especially with 10s.
 
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Looks heavy per cell. But the pricetag is worth a test.
Bought one and will test it to the limit. (and possibly beyond). My gut tells me 10Ah .

And like Emiel wrotes, go for 12S. That is just a tad over the voltage limit of the the 10S LiPo, nothing the electronics can't handle, and it will smooth out the drive a lot.
Also, it makes it easier to recharge. You can divide the pack up, and use affordable 6S chargers from the Radio controlled stuff. Like the Imax B6.
Those chargers have the BMS build in and can charge more than 1 kind of battery.
 
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I didn't think of that Maddox.
That hobby charger is a good idea. I have it and that way I don't need a bms. Safes me money on the bms and charger.

I still go first for the 18650 build. I know that it will be 19,25ah, where with the lifepo4 I think that it will be a bit lower.
But I think I will try them some time.
Easy to build and lighter then 18650. And with 32ah making 2 6s and connect them, is a great option. Also great for weight ballance. You can mount one on each side.
 
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All great info people. I think I will pull the trigger on the 25Ah Variocore's. The only thing I don't like is the move from terminal posts to flat terminal pads. I was hoping not to have to bodge together a spot welder and I really don't like the idea of spot welds taking that much current.

i have seen the 14Ah ones described as 15Ah, so I think they are probably derated from original specs because they are old stock - you might be surprised and get the full 14Ah.

Shoog
 
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Let us know how it went and how the battery specs are.
I am surtenty interested. The lifepo4 battery keeps his voltage for a long time while in use, so you keep power for a long time, especially with 12 cells.
Charging with a charger that has a balancer inside and split it in 2 as Maddox says, safes you money on the bms and those hobby chargers work great. You can set them up as you want and also use it to charge other things.
 
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This basically looks like a repackaged version of the 25Ah cells, about 5cm taller so not exactly the same and might suggest that the Varicore ones will come out at 20Ah or there abouts.
 
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I wanted to update my this with my researches and where they have taken me. I have been pouring over this for weeks now and have found it really difficult to come to a decision.
After researching the solar forums I came to the conclusion that the AliExpress route is high risk for the following reasons:
-its impossible to know with certainty what you will get, no matter how hard you research the seller, a lot seem to be selling B grade or salvaged units which are likely down to 80% of their capacity and half used up. Those that are A grade are likely to be overstated by at least 10% judging by their basic dimensions and weights.
-free postage is a high risk route to customs impoundment and loss of goods, or high charges.

I looked into Alibaba but came to the conclusion that:
-finding a reputable seller is even harder
-those reputable sellers charge big bucks on carriage. I was quoted $100 and $250 carriage from known reputable brands. This still doesn't cover import tariffs and VAT on arrival. When all costs are tallied then they ultimately come out on a par with reliable European and American sellers.

The European supplier GWL sells these units which when all costs are accounted for are on a par with similar prismatic units from China. Ultimately for the 36V 20Ah battery the cells come out at about €320.00. Capacity is guaranteed, carriage is guaranteed, duties are zero since they are from Europe so no nasty surprises and delays at customs.

However there is a better option which even though they come direct from the USA they are about half the price:


These are army surplus and guaranteed capacity cells with excellent characteristic. The box as sold with all carriage and duties paid so will come out at about the same price as the GWL prismatics. However there are enough cells here to build 2x 36V 19Ah batteries or roughly double the value.
This would allow me to buy a box, build a battery and sell on the 60 surplus cells to recover half my costs. This give a realistic cell cost of about €160 at my door. All from one of the most reliable battery sellers in the world.

Anyone critique my logic ?
 
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No comment on your logic, just a suggestion that you may want to check out the forums at endless-sphere.com. It's a site devoted to electric vehicles that caters to DIYers; they could definitely help with finding a reputable vendor for batteries and/or steer you away from questionable vendors. I've been lurking there for a while researching motors and come across a smattering of related discussions on batteries including suppliers and build discussions.

If you don't want to do a lot of reading you could do a search on each vendor you're considering and see what comes up to help you decide. Doing a quick search on "batteryhookup" gives 122 matches including multiple hits from amberwolf, who some members on this forum may remember. And searching on "GVW" gives 51 matches but most of them appear to be in context of "gross vehicle weight".
 
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