Insight MK1 Battery Pack Options

[retepsnikrep]

Sadly it looks like the Lifebatt option is going to be too expensive to make a viable product for all our ageing nimh packs, plus it requires a lot of up front investment £50,000. Anyone won the lottery or want to invest?

So we need something cheaper please see this thread for battery options and discussion.

We will leave the other thread for lifebatt updates.

To start the ball rolling here's a link.

Headway battery,lithium battery,Power lithium battery,E-bicycle lithium battery,E-motor bicycle li-ion battery,E-automobile lithium battery,Auto Strat lithium battery,Large equipment spare lithium battery,spare emergency power lithium battery,lithium

Whatever we use IMHO has to satisfy a number of requirements.

1) Must fit into the oem battery space using standard mounting points and probably a modified oem battery case.

2) Must be capable of full 100A discharge and 50A charge.

3) Must be minimum of 8ah useable capacity

4) Will require 48-52 lifepo4 lithium cells.

5) Must have screw or bolt terminals (No solder tags)


Note the lifebatt cells have their own BMS, so we will have to source one to suit our application it doesn't need to be very advanced, simple over/under V & temp with a 350ma bypass balancing capability. Over to you.

[IamIan]

Although I do see the Li options as giving more Ah per kg ... if we are trying to keep costs down maybe we should just say some of the other things on the list as what we want the battery to do... and not unnecessarily restrict ourselves in the type of battery or battery chemistry.

Whatever ends up filling the bill and being the best fit wins ... no matter what chemistry it turns out to be.

[retepsnikrep]

Ian.

Lead acid is a total non starter IMO.

So that really leaves nimh or lithium as the only viable mainstream alternatives.

If we want to use nimh then we may as well stick with what we have. Someone just needs to source some suitable cells and job done. Ron might be able to do this at some stage.

That leaves lithium of some sort, I'm open to persuasion but firmly believe we should be looking forwards trying to improve performance, reduce weight add phev function etc. I agree cost is important but I also want better performance not necessarily the cheapest solution.

[MN Driver]

IamIan, I see what you are getting at. It all depends on the goals that one has for a pack replacement. I don't think there is one answer to this and it comes down to the goals of the individual, it's why the pure-EV community is using batteries of every chemistry, shape, size, brand, etc.

Post what you have in mind. I see the cheapest option could possibly be lead acid but I see limitations to that such as cycle life issues, peukert effect especially based on 100Ah loads, weight, extra size, the requirement of float charging, charge efficiency issues. Post your goals and we can share thoughts, maybe you had something else in mind.

I like Lithium because of its great size and energy density which means we might be able to fit it within the same form factor pack ...maybe, measurements will need to be taken but getting everything in the OEM 'hidden space' shouldn't be an issue.

I'm looking for similar performance to the original pack, or better.

Peter was pointing in the same direction as I was looking at with the Headway cells. There are 38120s which is a 10Ah cell and 38120p which is a 8Ah cell. Their cells have screw terminals available so no solder tabs or discharge welding would be neccessary, just the proper torque to the cell and proper wire or plate size would be needed. I've seen pictures of plastic frames with aluminum(I think they are aluminum). The lower capacity cell has less voltage sag under load and I think it would be the best option for a single string of these if they have a decent voltage profile that we can work with under short duration 100 amp loads. I'm currently in a car traveling to meet family out of state so I don't have links of tests people have done in EV forums with me but I know there is data out there. The 38120p cells stay around 3 volts at 5C but at 12.5C they will sag lower than the 2.9vpc that we would need to keep them above 140 but with Peter's work this shouldn't be an issue, but we don't know if there is a lower voltage where things shut down, but we won't be running at 100amps over a long time so I'm thinking these should work. These are rated at 20C pulse and 5C continuous(40 amps). The other cells are also rated at 5C continuous but the smaller cells might just use 5C as it is more of a round number. I'm sure that as long we can keep the cells cool 50 amps should work out.

These have been bought by many people using them in electric motorcycle conversions on DIYelectriccar forum and are sold at 17 US dollars per cell from a vendor called <vendor removed, terrible outcome where many lost money>, they were able to successfully get a few bad cells that came through replaced and they made the process of ordering and buying smooth based on what I was reading from the members posts there. The vendor buys them in a large lot as a group buy that they organize to bring the price per celll down. They have shipped Thunder Sky and Sky Energy cells internationally and I think they do the same for these too. The cost for duty, ocean shipping is 10% over the standard price and add ground shipping costs too. There site is <removed>

Another option is Thunder Sky, Sky Energy or HiPower cells for 40Ah. This is Thunder Sky and Sky Energy's smallest size and for HiPower I wouldn't want to go any smaller when a 100 amp load is involved with a prizmatic cell. Figuring the TS cell costs would be about $2420 for 50 cells if adding the 10 oercent added US fees, ad shipping for final cost. The 8Ah cells would be 850 US$ plus the 10% plus shipping costs. So it all depends on the size and budget that someone wants. The Thunder Sky cells are rated for a longer cycle life by their manufacturer at 5000 cycles at 70% depth of discharge, but who knows what that really ends up being in real life. They are rated 3C continuous so I wouldn't expect any performance issues with them. Who knows what is happening to the prices of these because last year this time they were much more expensive than they are now.

That is the information I have at this moment. I'll try to get some links for the Headway cell discharge charts when I get the chance.

[retepsnikrep]

Gents' I've changed the thread title to reflect that this is a discussion about multiple cell chemistries. Fire away. I just don't like the lead acid option, and I've had a few sets in EV's over the years. Unless they were huge capacity they just could not stand the high rate discharge and cycling. Having had two sets of Lithium batteries I've been spolit and could not go back to anything with less capacity/weight etc.

I think the prismatic cells like TS/highpower are fine but you need a minimum of about 40ah cells to stand the high charge/discharge and they will not fit into the IPU compartment. A 50 cell pack of 40ah is a big heavy pack as you can see from my own experience. Lots of off the shelf BMS solutions available for those though including my own of course.

With headway cells I might be prepared to risk the cost of one pack to see what they are like, I also now have remote multicell 16 cell slave boards for my BMS for non prismatic cells so I can build a BMS for a 144v 48 cell headway pack fairly easily. Be very interested to see the discharge curves MN.

I'm picking up an empty oem battery case on 06/12 so I can then start a few measurements.

I suspect the internals of the battery case will have to be cut out, but then see the cells in layers seperated by some sort of plastic seperator. A stack of the little headway bus bars reqd. I wonder if it is possible to use a short piece of threaded rod and screw cells directly together in series sticks. Might need a small thin locking nut in between cells but that would make assembly much quicker. Just thinking out loud! If they protrude slightly out of the end of the right hand side of the battery case that doesnt matter so long as suffcient clearance remains between the end of sticks and the IPU case. I had a look recently at the wiring for the IMA breaker and the four pack connection points. I think that can be done away with and reduced to two with the HV switch on the + end of the giant string. I agree that may not be best but depends how the organisation of the cells lines up with the relay board points. Just my 10 cents.

Some Headway testing data.

http://www.zeva.com.au/tech/headway/

http://endless-sphere.com/forums/vie...hp?f=14&t=3374

http://headway-cn.en.alibaba.com/pro...e_battery.html

I had a quote from Ian Goodman who supplies the lifebatt cells for just the 8ah cells on their own, this is considerably better, but we have to assemble them in our own case with our own BMS etc. But they are higher quality than the headway and more likely to be able to stand the abuse. 8ah cells are $28 each (Plus vat and delivery here in UK) We would need 48-52 cells. About $1400 plus taxes for 48 cells. Actually that's not too bad. But then we have to add cost of BMS call it $300 call it $2000 for a 8ah pack weighing 14kg about 8kg less than nimh with x 2 capacity.

[IamIan]

Thank you for opening up the possibilities of the discussion... I guess I just prefer the needed criteria to pick the best option no matter what it turns out to be.

I think a replacement battery pack needs to go in one of three directions ...
#1> less cost than the Honda IMA battery for equal performance.
#2> about the same cost as the original IMA battery for better performance.
#3> more cost for better performance.

The now ~10 year old NiMH technology battery pack from the I1 was about ~43 wh / kg... about ~139 Wh / L ... a peak burst of about ~663 W / kg ... and a peak burst of about ~2,140 W / L.

To meet the space requirements to fit in the same space as the original any alternative battery must have at least equal or better Wh/L and W/L... if it can not meet this than it will use more space to do the same job... some improved battery arrangement might potentially still allow a slightly larger volume of battery to still fit in the same OEM battery module space... which does have some room for volumetric packaging improvement.

In order to meet the performance requirements of equal or better energy use time ... any alternative must have equal or better Wh/Kg and W/Kg... if it can not meet this it will use more weight to accomplish the same job... a minor increase in weight might be acceptable for a significant increase in total Wh of usable energy.

A Honda OEM battery cost ~$2,000 U.S. ... less from a junk yard, but might need parts replaced or serviced... options #1 and #2 would have to avoid going much over this for the complete replacement.... #3 could go over it by as much as we are willing to spend extra for it... individual budgets may vary.

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While the wh/kg of modern PbA might be close to this ~10 yeaer old NiMH tech ... even modern PbA do not stand up to the other performance requirements ... of wh/ L ... or the peak burst W/kg or W/L... even Modern PbA would have a very hard time surviving for very long if they were put into such an harsh treatment... PbA might be able to cope for a short time ... but to have it handle these stresses for an equal amount of time it would have to be significantly larger and heavier... which is fundamentally reduced performance... Although PbA would be cheaper the reduced performance to me is a deal breaker for PbA.

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Aside from PbA there are many other types of batteries ... but we are limited to just the ones we can buy and use ... so batteries that are still just in the lab ... will not be an option until they are out of the lab and become available to buy and use... That removes some of the 'futuristic' in just a few years types of batteries... if we can't buy it we can't buy it ... its that simple.

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I'll have to do some more poking around and see what I can find... among the more modern NiMH and other Li options.

Nice to see the this type of thread though ... I hope to pans out eventually.

[jonnyvtec]

When I was at Land Rover we had a Freelander 2 hybrid prototype running a 300V NiMH pack in the typical D cell arrangement.

I was surprised to hear it was only a 5Ah pack, but asking the battery guy apparently they were Sanyo items that did 100A discharge and charge. Would there be any merit in pusuing that. My drive is a B road so capturing more energy when slowing would probably yield decent improvements. That said the costs is still probably prohibative.

Do we just way for the large format patent to run out ? :P That said apparently Samsung have bought Cobasys.

[JimIsbell]

PbA is so cheap and so available in so many sizes and shapes that I dont see them as being that bad since they might be replaced every 3 years cheaply enough to offset that short life. That would give a platform to wait on until the next train comes in. I dont like Li because they havent convinced me that the fire potential has yet been managed. And between those is only NiMh as I see it.

[retepsnikrep]

Gents perhaps we need three threads, pb, nimh & lithium then supporters of each can investigate them. I won't be working on a pb pack but I'll offer my thoughts if reqd. I will help with a nimh one if it is a straight cell replacement project which would be the easisest if we could get suitable cells. Johnny please follow up on your ideas and find out about those cells, price availability etc. Any info I discover with Lithium will be passed on and the BCM fooler & interceptor are there for everyone to use/modify. Each to there own and variety being spice of life and all that.

The simplest solution would be for us to order the same cells as honda uses and club together to make the minimum purchase reqd. I'll have a set if someone wants to organise that.

Headway quoted me today for 52 cells

The 38120P 8Ah high power cell is 14usd/piece FOB Shanghai, so for 52pcs. the cost is 728USD.

Half the price of the lifebatt but possibly a false economy?

[retepsnikrep]

Originally Posted by IamIan

A Honda OEM battery cost ~$2,000 U.S. ... less from a junk yard, but might need parts replaced or serviced... options #1 and #2 would have to avoid going much over this for the complete replacement.... #3 could go over it by as much as we are willing to spend extra for it... individual budgets may vary.

You very lucky over there, a replacement over here in UK is about $3500 so I'm looking at a higher overall budget for the project. I'll try and get an accurate price later.

I think Ron probably has the US junkyard pack market sewn up so not many old packs about now.