Batteries and New Battery Technologies

Hi Cameron, It is certainly cheaper, but heavier. What makes you still to stick to Lead Acid B's ?

I have asked this a number of times and nobody is willing to answer my question.

How do you connect Lead Acid Batteries parallel? Just like that or with some protection that the one battery cannot feed the other battery. Is there another methode than Diodes and maybe a better one?

Bert

 

No Bert, I use the adapter that came with the torch. It has all the little things you mentioned in it, but Vimes doesn't seem to understand what an adapter is. Let's leave it at that.

 

Hi Bert,

I will be sticking with lead acid for purely financial reasons. The purchase price for a 96v pack will probably be leas than $2,000. I'd be paying more like 3.5 or 4 thousand for Li, plus the BMS. What I will be paying with is weight. The car is going to be much heavier and have poorer range because of it.

Some people handle the charging issue with lead acid by simply using a separate charger for each cell (96v / 12v = 8 cells), so even when using 6v cells, you only need 16 chargers. However, it is also possible to buy more capable chargers that can handle large packs. I think that what it boils down to is the lead acid cells can handle the abuse of over charging. I know that flooded lead acid cells are happy to over charge a bit; the solution just boils. As long as the levels are topped up on a regular basis, little harm is done.

In the land(?) of boating, I'd assume the weight of lead acid is less of an issue, depending on what kind of boating we are talking about.

 

Cameron,

You are not alone. The Fed's are putting lead acid in our submarine during

refit as we speak. I too am going with SLA's on my tiny prototype but will

upgrade with better/cheaper down the road.

Your reference to single cells is off a bit but I'm guessing you realize that.

Even 6 volt batteries have three cells in them, so you're not actually

isolating each cell, just each battery.

Tom

 

Indeed. Sailboats in particular benefit from a heavy keel. Lead batteries could be used there to get a "three fer" - 3 issues solved by heavy lead batteries- cost, stability, electric power.

Porta

 

Why is everybody dodging my question? What is the best way to put batteries parallel !!! What is the best methode and do they differ for each kind of batteries.

Like: For new Lead Acid Batteries, no problem you do not use anything, but if a dud batteries get replaced, you have to be utmost carrefull to make sure that the new battery has the same parameters as the old ones. i.e. half charged or fully charged or whatever. Otherwise the new battery will feed the old batteries.

Like: For NiMH batteries, no problem ?????? (I doubt that)

Like: For Li-lion, no problem ??????? (I doubt that)

Who can put some lights on the above.

Bert

 

This follows my earlier post on lithium:
http://www.oxfonline.com/MMT/MMT1009.html?pub=MMT&code=EMMTKA24
I expect it is somewhat of a beat-up of the real picture but it could be that the battery production is starting to influence lithium supply.

Interestingly when I did my thesis on electric vehicles the idea of using lithium for a rechargeable battery was not even considered. High temperature Na/S batteries were being promoted as the best chance. Lithium was considered far too reactive for any useful purpose.

Rick W

 

Bert,

Sorry to semi-hijack your question. I am simply wiring my six volt SLA's in

series for six (making 36V's) and then paralleling those into two banks of

six (still 36 V's but now 36 batteries). I end up with two, 36 volt banks of

36 (six volt) batteries. Point being, no diodes, just varying gauge wires

and spade connectors so I can intermittently check in on each individual

battery's state of health. All are fused.

Tom

 

Bert, lead/acid is a compromise for me, (lightweight sailing cat), but I am not satisfied with the long term reliability (unpredictable failure and charging regime) of the other options and the high cost is another factor... Who knows what will mature to become the prime choice in 2 to 5 years?... Stay with the old plodders for the present, seems a prudent initial choice...

I am still keeping an active watch on potentials and new ideas, which is why I watch this thread with great interest...

 

Cameron
I think lithium are already close to being economic for electric vehicles.

Have you considered buying just enough lithium to get the power required so you can do some serious testing. Will not work if the range is your priority of course.

There is rapidly growing options for lithium and getting experience with them will be valuable as they will make battery vehicles comparable with ICE.

The Ah rating on lead-acid batteries is not a very meaningful performance indicator for vehicle use. This data sheet gives you an idea of the current efficiency at higher rates:
http://www.fullriver.com/products/admin/upfile/SPV70.pdf
So you think you are buying a 70Ah battery but that is only true for low rate of discharge. In a vehicle application it is more like 50Ah where you are accelerating often.

And this is only one part of the story. The voltage drop also needs to be considered. The curve shows well under 12V if you are pulling decent current.

My 22V 5Ah, 715g LiPo battery delivers al least 4 times the power of two small 12V, 10Ah 3.5kg VRLA batteries.

Rick W

 

Tom,

Good call on the cells vs. batteries point. Like I said, I'm not the most experienced!

Bert,

Sorry to dodge the question, it wasn't intentional. I think that with lead acid it is simply: wire them up. As for replacing dead/damaged batteries, a lot of people will tell you to replace the whole pack, as that is the ideal solution. Of course, it isn't always an option, in which case matching is important, as you mention.

I'm not sure if people use the hardware store "marine deep cycle" lead acid batteries to built large packs on boats, but I would advise against it. There are lead acid batteries that are much more robustly 'deep cycle'. These are usually sold as gold cart batteries, lift truck batteries, etc. My understanding is a properly cared for pack can last 3-4 years. Hopefully this would mean that you wouldn't need to replace too many individual batteries in that time.

Rick,

Yes, it is true that the performance of the lead acid batteries is dreadful compared to Li. Really, this translates into Li batteries costing less than it appears (the useable AHs being so much greater with Li that a smaller pack is an option). The low sag is great too.

I think that you are right in terms of economics, when longevity/life cycle is factored in. However, I've been told by many people who have built and driven EVs that killing the 1st pack is almost a certainty, simply from inexperience. I think I'll wait on the Li until I'm certain I'll get the long-term payback that makes them attractive.

 

I have only been playing around with little VRLA and lithium batteries but have explored their short term potential in some detail.

A year ago I was convinced VRLA was the way to go but have completely changed since trying the little lithium.

I still think it worth your while to have a close look at how much lithium battery you need to do some decent testing. If you get it right you can add to them to improve range. If you stuff them then you have a lesson out of the way. You will be further up the learning curve.

You can do a lot of experimenting with the charging systems. The vehicle performance should be lively because it is not lumbered down with batteries. It will enable real life performance evaluation.

I think you will find lithium batteries already have a good cost advantage over VRLA per kW. So you could do full power testing at less cost.

The main reason I got the lithium was so I could get something like 1kW to do useful testing. The two little VRLA run out of puff around 260W. At that level the output is only 18V and the battery protection on my controller comes into play.

Rick

 

Cameron
I was looking around the Fullriver site and see they are now into LiFePO batteries:
http://www.fentbattery.com/en/Cylindrical.asp?id=452
The 48V 20Ah battery looks interesting. It is good for burst of 80A and continuous discharge up around 40A. The literate states it has inbuilt BMS.

A couple of these in series to give 96V nominal would give you about 8kW in burst. They only weigh 7.5kg each. How big is your vehicle?

Rick

 

Rick, do you have any technical information on those batteries -
- Charging regime and appropriate controllers / requirements?
- Cost for 220Ah 48V package for my boat, ( 11 units in parallel? = 82.5kg )
- Special considerations for wiring up,
- Maintenance and lifespan/cycles
- Risk factors when compared to spiral wound AGM lead/acid system?

Current nominal charging system availability includes 1600W solar panels
22hp Kubota with twin 48V Delco configured in parallel to give 100A

Draw includes a full 240VAC galley (via 48V inverter 3800W / ~ / 10000Wpeak) and two torqeedo electric outboards peak draw of 8800W @ 48VDC but usually between 2000 and 4000W when used and with alternator/genset operating in parallel to the batteries if motoring or motor/sailing...

 

Paralleling batteries always causes charge distribution between the stacks, but when all cells are healthy there is no problem. The voltage difference is so small it can be compared with a trickle charger.

Yesterday evening I added a new 12v140Ah battery to the battery bank of my home solar system. The other batteries were almost fully charged, the new one came from a store where it had been standing for months.
The voltage difference was approx. 0.5 volts and the current flow initially 1.3 Amps. After 10 minutes the current had dropped to 0.2 Amps. This morning with abundant sunshine shows 13.85 V for the whole 440 Ah bank.

As long as you do not mix different technologies, I see no problem with NiMh or Li either.