Main Batteries

[PhilCastle]

Hi, having been too tied up with work to get anything done on my MkIV, I'm hoping to do some planning over the Xmas break to get on in 2018, as I missed totally my original lofty plan to be really for the 100th anniversary last November. But I am re-enthused having managed to finally get my own copy of "following the tanks - Cambrai" Can somebody tell me the spec of the main drive batteries they are using please, particularly anybody using lithium.

Phil
Bayardo II (B36)

[Stephen White]

Phil,

Info in the Knowledge Base here:

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

I suspect the majority of Armortek builders have stuck with lead acid, on acquisition cost grounds, but lithium iron phosphate has a number of advantages and, with a longer service life, probably has a comparable whole life cost to lead acid. Note that LiFePO4 batteries come with battery management and do not suffer some of the combustability issues from which LiPo have spectacularly suffered. LiPo is not recommended. Next generation graphene is starting to become available in the lower capacities.

Hope that helps.

Stephen

[Daniel Scholefield]

My Mark IV has been running on two 12V 22Ah lead acid gel batteries as that what was recommended at the time and they have been fine. Unlike most other tanks there are no space limitations and access is easy so even if your tank becomes a battery eater (as mine has for as yet undetermined reasons in addition to my need to run it around as much as possible) it is easy to swap them out for spares or simply to recharge. Whilst I do not fully understand the technology I agree the LiFePO4 betteries are better, it is just a big up front cost; I will eventually replace mine but I am in no hurry.

[Chris Hall]

Phil -

You dropped out of sight there - welcome back !

My experience echoes Daniel's so I haven't really got much to add. I'm no electrical expert, but ampage seems to be the key to a long running time - I know one owner who runs 12v 36a batteries ! Daniel is right that there's plenty of room in a Mark IV, but you still need to plan it carefully to get everything in and accessible.

Looking forward to seeing progress reports on Bayardo II, and Merry Christmas,

Chris

[Gerhard Michel]

Hello,

in our models LiFes become increasingly interesting because they are smaller and lighter than lead acid batteries having the same capacity. Another large benefit: LiFe cells can be discharged to 100% without loosing much of their duty cycles, lead acid (AGM) batteries can only be discharges to 50 % under same conditions! Therefore one can replace a 30 Ah lead acid battery with a 15 Ah LiFe without losing operating time. A 15 Ah LiFe battery weighs much less than a 30 Ah lead acid battery and needs less than half the floor space requirement. LiFe cells have about 10 % more avarage voltage than comparable lead acid batteries (approx. 26,4 V to 24 V), which results in a more powerful driving when needed. Their internal resistance ist much less which results in a lower voltage drop when high currents are needed (e.g. table turn). Your vehicle is much more agile than before!

Another big benefit is the far higher allowed discharging and charging current! LiFes can be loaded with 1 C to 4 C charging current, depending on the used type. This means one can charge a 15 Ah LiFe battery with 15 to 60 A (!) without any damage to the cells. In other words, a nearly empty LiFe cell can be charged in 60 up to 15 minutes to approx. 85 % of its capacity! Now one can recharge his tank in a short pause while eating his snack.

An important requirement for these cells is a powerful charging equipment to get the needed currents. E. g. here the charging of my 40 Ah LiFes of my King Tiger with 1 C (40 A). The shown charger can emit up to 70 A charging current. The balancing of the cells is an important criterion which is fulfilled automatically by a good charging device.

[PhilCastle]

Sorry away over Xmas, lots to take in, so thanks for all your advice.