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The batteries can put out 3-5C bursts of current, you just need to work out your 'C' (capacity) so that you can get enough power out of them to accelerate. A 60Ah pack can put out 180A at 3C and 300A at 5C... a 100Ah pack with do 300 and 500 amps.

If you are driving at 160A max then it sounds like a 60Ah pack will do everything you need without straining the batteries much at all and you still have some room to play with for acceleration.

What DoD do you go to on your lead pack? As far as voltage sag goes real world anecdotal evidence seems to suggest thundersky lithiums sag 0.2v per 1C of current per 3.2V cell. If you are going to 50% DoD then you have 170 x 0.55 x 0.5 = 46.75 usable Ah. If you multiply by 1.32 for the lithiums you should get around 62Ah to match your Lead pack- not counting the weight savings... if you are already doing 80% DoD then it will take about 100Ah to match the LA.

Then you just need to work out whether they will give you enough current at 3-5C.

Moving along slowly, I have just moved in the last couple of months which made it difficult to get any work done but I just moved the bike into a friends garage on Wednesday which will make it heaps easier to work on. I'll hopefully be getting started on fixing up the bike itself and then doing the motor mounts in the next month or so.

Hey DVR where are you getting your batteries from? Foundry and Fiberglass or somewhere else... What are you doing for BMS? Honestly the thing was pretty skewed towards lead and lithium still came out neck and neck. You're very unlikely to get that many cycles from lead to 80% DoD.

Thanks for the feedback Bazza, its good to hear... I'm still saving up for my TS pack.

Well as I worked out in the blog, Peukert's effect and DoD play a big role in the usable energy of the packs. If you go to 80% DoD with Lead Acid (and a lot of EVers prefer to stay above 50%) and assuming you get 55% of the 20hr rate at the 1hr or so you will actually use the battery at you only get 44% usable energy for Lead Acid Batteries whereas Lithium would give you 76%. Rehashing your numbers that means that:

Manntis uses the 90AH lithium cells at 3.2V each, and 3KG per unit
3.2V X 90AH = 288AH X 98U = 28224WH of storage x 0.76 = 21450 usable Wh
98U X 3KG = 287.76KG
28224WH / 287.76KG = 95.92W/KG = 74.54 usable Wh/kg
(3.2V*90AH)/3KG=95.92W/KG

There was repeated mention of the T605 as a solid contender for the Lead camp, so using that as an example:
6V X 210AH = 1260AH X 24 = 30240WH of storage x 0.44 = 13306 usable Wh
24U X 22.08KG (50lbs) = 529.8KG
30240WH / 529.8KG = 57.08W/KG = 25.11usable Wh/kg
(6V*210AH)/22.08KG=57.08W/KG

So for a given weight you can have three times the energy with Lithium, or for the same sized pack your lithiums should weight 1/3 the weight.

On the discharge note, most controllers are only 500A which only requires a 100Ah battery pack which would be a pretty small range for most EVs so I don't think that's an issue, if you want higher discharges there are more expensive lithiums that can do bursts of up to 40C.

The only real advantage Lead Acid has is upfront cost, which is a big advantage I'll admit, but I don't think its worth the maintenance, weight, size and inefficiency of Lead, especially when the high cycle #'s of lithium make the lifetime cost comparatively similar (at least within the ballpark).

This method would also work pretty well for you car guys too...

Well where I live it is cheaper or at least just as cheap to go with lithium in the long run, assuming they hold true to their 2000 cycle life. That's not taking into account the added benefits of their smaller size and weight. It may be different for you where you live, so I suggest you do your own research, just make sure you size your pack with the usable energy not the total energy rating of the pack. You can use a much smaller lithium pack due to peukert's effect as I outlined in the blog.

Sorry there isn't a more conclusive answer but I guess its just 'It depends', I'm glad you liked the thread though

I didn't know you used TS manntis? What sort of current are you getting out of them? I am hoping I can squeeze 5c every once in a while but it looks like 3c is the norm.

I'm going with the 3.2V 60Ah cells, they weigh 2.2kg each so my total pack weight weill be around 53kg. Considering the engine weighed 66kg that is pretty good . You need one slave module per cell so the higher the voltage the higher the cost, but its not too bad.

There have been serious issues with Thundersky in the past, and a lot of the EVDL guys have been burned by them and are completely against them which is understandable. A lot of it I think had to do with Chinese vs western Quality control expectations, something I think thundersky has learnt their lesson from. I haven't heard any negative reports about the latest model of thundersky batteries. Rob from EV power has done 10,000km on them without any problems. Ian from Zeva is using them in his MX5 even after his extensive testing of lithium batteries. Trev from Foundry and Fiberglass has no problems with his new batteries. I will be monitoring those conversions up until I buy my own batteries but I think the newer batteries are trustworthy, and have not heard of a single report of bad cells of the LFP batteries.

Well the MX5 should be finished in early june so I will pass on any performance reports I get.

I've never heard it explicitly explained but it is basically 3x Capacity or a discharge rate in amps of three times the capacity in Ah. SO for a 60Ah pack, 3C means a 180A discharge. A 100Ah pack gives 300A at 3C.

Lol, for a simple comparison on paper I didn't think I'd be under so much scrutiny! Mitch the battery specs that are half what is advertised is the current rating. They only put out 3-5C not 10C as advertised. I have already designed my ReCYCLE project around the tested parameters i.e. 300A peak from my 60Ah pack. But thanks for the research.

If anyone wants to disagree with my conclusions then go ahead and do a comparison with the batteries you are considering. I just did it for the batteries I was considering, and as they were both from vendors inside Australia they already included the tax.

Well I've looked at like 6 suppliers here in Oz and I can't find any Trojan's cheaper than that $225 mark. Are they made in the US? That would explain the price difference between here and there. If you can get them for $92 then go for it. I have only seen 2 suppliers of thundersky cells in Australia and I actually used the more expensive price of $2.50 per Ah when my other supplier can do it for $2.40 normally or even as low as $1.83 for bulk orders. As I said in the blog, it would be different for different countries.