Batteries - Lithium Iron Phosphate or Lead Acid Gel?

[phil fitzpatrick]

Good morning Stephen,
I was looking for the specification and prices when I came across the Aprilia
Forum.
Certainly confirmed from the manufacturer the need for respect and no abuse of these
systems.
The longer life and more cycles and lighter weight are big winners,shame about the
pricing,it cant be that more expensive than other batteries to make
Keep up the good work,I think its all down to carefull experimenting.
Another couple of thoughts,
I had spotted somewhere the minimum discharge voltage.
So I wonder how the better cycle rate would stand up to completely running down the
battery until the Tank stops,the safety equipment should stop this though.
RE the new motors.
I cant remember at what model stage the new motors were available,but
looking at Andreas list he looks to have probably a mix of new and old motors.
So there might not be any imeadiate short term problems with the charging spike.
Cheers
Phil

[Andrea Daviero]

Our tanks does not require extreme current draws, so the problem of overheating or damaging batteries is limited to the overvoltage during charge or overdischarge if not monitored.
A battery with low "C" factor (1C 2C and so on are a cherging/discharging values wich tells you how much current is supposed to safe for the battery) is sufficient for us.
Try this: Good price low C values, no BMS but a balancing plug or a BMS can be done with no problems (the cap of the battery can be removed, and cells are bolted).
http://www.lipotech.net/storeindustria/ ... er=product

Another difference between Pb batteries and LiFepo is the storage life. If a pb battery tank is left unused for over an year the batteries will lose power and usable life, sometime you will need to replace them also if you have not used them. LiFe batteries if left charged will remain charged (low discharge factor) and capacity remain costant over the time.

About chargers, modern model chargers support LiFepo batteries, few supports 8 cells batteries and few of them are very powerful. Icharger 308duo for example, robbe c8 eq-bid, lipotech 2x800W... Just to name few have good performance and internal cell balancing.

[Adrian Harris]

> I've ordered a DIY kit from "Battery Matrix", which appears to be very similar to
> what Eclipse are selling, but direct from the Orient, so a few pennies cheaper.

Unfortunately, these batteries never turned up, and the suppliers haven't responded to any of my emails, so I have been forced to raise a claim on Paypal

Adrian.

[Andrea Daviero]

Adrian, I'm sorry for the problem you had, I think that with paypal you will easily solve the problem. Take a look here: http://www.lipotech.net/industria/index ... &Itemid=72 and I hope you will find the best battery for your needs. Prices as good. As you seen above, all of us in Italy are using LTE 12,8V Batteries with a separate balance plug installed on them.
I don't know if they use paypal.

[Adrian Harris]

Thanks for the link Andrea

I've had bad luck with Paypal once before, where they wouldn't refund my money because there weren't any funds in the sellers account.

Given that the sellers Paypal account was at hotmail.com, not their registered domain, I'm not holding out much hope.

Adrian.

[Andrea Daviero]

It is sad Adrian! It is also strange that paypal needs that the seller has money on its account.

[Adrian Harris]

Paypal have found in my favour and, more importantly, recovered my money, which should be back with me "within 5 days"

Adrian.

[Maarten Schutjes]

Good news!

[Andrea Daviero]

Happy to see you solved Adrian!

[colin fairweather]

great protection from PayPal once your in the right

once I had my account dipped for €400 some scumbag in china didn't even notice first and only problem I've had with them they sent an email to inform me and I was refunded all good

[Tim Page]

Just out of interest, what is the aprox charge time for a 24v 20 or 22mah Life pack?
I am hoping it would be quicker than the PB Gel charge time.

I currently have a pair of old 12v 20mah gels that i am thinking of replacing. These are currently charged with a 4.5mah Mobility Scooter charger but it seems to take an absolute age to recharge and the green 'fully charged' light never comes on now.
Not too sure about run time as ive only really run for an hour max at any time to date.

Anyway, i am trying to decide if it is best to get a new pair of gels, and use the old set as a backup (field Recovery) set or invest in a set of Lifes.

I am not planning to sell my Panther in the near future so happy to make the investment.

What do you guys suggest?

Cheers
Tim

[Peter Silcock]

Personally I don't use Lithium batteries mainly because the size/weight saving is not much of an advantage in most tank models (different in halftracks etc) and the huge cost difference is not worth it to me. That said there is a huge apparent advantage in Lithium in much extended running times and many swear by them for this reason alone and I can see why. Certainly "old" gel batteries may not perform well and 12AH batteries are probably too small for your average 1/6 tank. A tiger and similar will easily take 22AH and a KT will take 4 of these. If you go down the gel route again , I would suggest deep cycle batteries such as Lucas. A good battery charger will also make a big difference. If your fully charged light is not coming on I think you will find your gels have reached the end of their life. Perhaps people who have experience in Lithium can weigh in.

[Stephen White]

Tim, hi.

The Tracer LiFePO4 24v 20aH battery quotes a charging time @5A of 5-7 hrs. In practice, after a day of running my Cent at the Tank Museum, I recharged fully in less than two hours.

I did a Knowledge Base Topic on battery selection which tries to set out the pros and cons of LiFePO4 cf AGM Lead Acid here:

http://www.armortek.co.uk/Forum3b/viewt ... =34&t=5790

Having used a LiFePO4 on my Cent, I wouldn't go back to lead acid, which I've got on my Pz III. The latter is permanently connected to an Accumate Pro charger.

The advantages of LiFePO4 include:

- flat discharge curve - constant power for longer
- weight (typically 50% of equivalent lead acid)
- no memory effect (as you've got with lead acid)
- short circuit protected
- capacity/charge state indicator fitted as standard
- also protected against overcharge, over temp, over current, deep discharge

The cost issue is a bit illusory. LiFePO4 typically have a duty cycle life of about twice that of lead acid. So the simple equation ia: "twice the cost, twice the life". Put another way, the whole-life costs of both types are about the same. I did some figures on an earlier post somewhere on the Forum.

I agree with Peter that weight is not a critical issue for our tank models but nevertheless, there are obvious advantages in lighter models.

Probably also worth consulting Mark, in view of his continuing development of the motion pack.

Overall, for me, the advantages of LiFePO4 are significant but I can also see the lower acquisition cost of lead acid could be attractive.

Hope that's food for thought.

Stephen

[Tim Page]

Hi Stephen, Thanks for this info, I had forgotten just how expensive those Tracer packs are.
The cost looks to be £529 for the pack, plus £66 for the charger and another £15 for a converter lead.

I could buy at least 6 sets of Gel batteries for that price.

I appreciate that i would also get faster charging times and a much more compact battery if i moved to the Tracer pack but the cost seems OTT at this time.

Need to do a bit more research.

Cheers
Tim

[Stephen White]

Tim, ouch. I see what you mean, that's gone up 25% since I bought mine.

I still think LiFePO4 has a lot of advantages, it might be worth reducing the capacity. I'd have to do some real data collection on discharge rates but at Tank Fest last year, I ran for a whole day outside and only used about 20% of the capacity of the 20aH battery. I reckon you could get down to about £350 by taking two 12v of lower capacity. It might be that there are other makes out there too. Interested to see what you find.

Stephen