Batteries for a newby

[John chamney]

Hi all ,
I know this subject has been covered before but could someone please point me in the right direction . I am a complete newby to these tanks and would appreciate if someone with there vast experience could let me know which is the easiest battery to get along with that will do the job . There is a lot of technical detail in other posts but unfortunately it all goes over my head , can someone please tell me which one is best suited , thanks in advance .

John

[jwwirds]

This is a question for me as well. On the forum people said they used a LiFePO4 battery, so I got one of these in 24 V with the appropriate charger. In the manual for the Sherman Easy Eight however it is stated it is better not to use Lithium metal batteries because the motors generate a regenerative current. So what should be done?

[simon_manning]

x 2 12 volt Golf Buggy Batteries, e-bay £70 the pair Delivered, simple, easy Maintenance, i am not a keen driver and this suites me, as newbies don't get involved with complicated electrical set-ups, i also charge my Batteries separately one at a time with a Normal 12 volt charger. regards simon manning.

[Adrian Harris]

I think the reason for that warning may be that lead-acid batteries are a tried and tested system and just work, or not. If a customer has a problem, it's very easy to diagnose if the batteries are at fault.

With LifePO4, there are so many combinations - sealed packs, separate cell packs, with BMS, without BMS. Some charge through the same connections as the tank electrics, others use a separate port. You can be apparently running fine, then BMS spots a problem and switches the tank off. I've had that a couple of times from overuse, hence my interest in voltage and capacity telemetry. The shutdowns undoubtedly saved the battery, but could confuse someone new to these models, who might then blame the electronics or RC system rather than the battery.

More than half of the work I do on customer tank electrics is related to bad batteries or bad wiring.

I bought my first LifePO4 battery in 2014 and it has been used regularly, and on occasions roughly, at shows throughout the years since with only the couple of shutdowns mentioned above. These models may be big and heavy but with their gearing, it's almost impossible to drive them like an RC buggy.

All my models going forward will be powered by LifePO4, but then electrics are my area of expertise and I do have a good understanding of what's going on inside my models.

Adrian.

[florian rudolf]

I also use LiFePo accus. _They are strong, easy in use and verry indestructible.
BUT you must know for what kind of model is the right accu. - try and error...
I use the same LiFePo for my submarines. I think the run lots of hour with that. - I have to try

Cheers
Florian

[Simon Peck]

I’m complete opposite of Adrian, no clue where electrics are concerned. What sort of range can be expected from a couple of lead/acid golf cart batteries? Do LiFePo really offer such a dramatic advantage in our models?

[Adrian Harris]

> Do LiFePo really offer such a dramatic advantage in our models?

It's hard to say as I don't know anyone who has done any comparative studies between them in one model.

It also depends on what you do with your model. Mine get around 30 days running during a normal year, so I like the fact that there's no slow down due to voltage sag with the LiFePO4. Once you've run lead-acid batteries down to the point that it's hard to get the tank back in the car, then you've probably taken a significant bite from their overall working lives.

I see quite a few models which are taken to shows, given maybe one or two laps of the running area and parked up. The price of LiFePO4 really wouldn't be cost effective for that, though they do have a better self discharge rate, so are happier with long term storage without topping up.

Adrian.

[Gerhard Michel]

I’m complete opposite of Adrian, no clue where electrics are concerned. What sort of range can be expected from a couple of lead/acid golf cart batteries? Do LiFePo really offer such a dramatic advantage in our models?

Hi guys,

well, I made the mistake to use two 12 V 45 Ah lead acid batteries in my Jagdtiger (not Armortek). It lastet just one year and they were down in a hot summer day while being charged by an automatic charger (without a malfunction of the charger). Then I used 8 Life (36 Ah) cells and saved 18 kilograms of weight (!) by earning significant more running time! This is because Lifes can be used to a DoD near 100 %, AGMs only up to 50 %.

[Stephen White]

John

In my Knowledge Base topic, I wrote this summary (SLA = lead acid LiFePO4 is Lithium Iron Phosphate):

Which Type of Battery?

So, SLA or LiFePO4? It really comes down to a personal choice.

SLAs have been the default for Armortek models and over the years have provided a good solution for most people. They are relatively cheap and commonplace across the globe and can manage high charge and discharge rates safely.

LiFePO4 on the other hand, whilst more expensive and needing to be paired with a battery management system (BMS) are becoming more and more commonplace as the prices come down. The two main advantages of LiFePO4 over SLA are that (a) they are much more compact and lighter than SLA, allowing more flexibility in placement of the batteries, and (b) they provide a significantly longer usable power duration in the field.

In practice, if you want longer running times in one session, go for Lithium Iron Phosphate, if you only want shorter runs and can recharge, Lead Acid is perfectly OK. Lead acid are cheaper to buy but don't last as long as Lithium Iron Phosphate. So over a span of say two years, they're pretty equal in cost. There are a lot of other Pros and Cons to both. On balance, people are gradually moving from Lead Acid to Lithium Iron. Unless you're running a Universal Carrier and know what you're doing, avoid LiPos (Lithium Polymer) - they can be risky if mishandled.

Do have a look at the Knowledge Base Topic for more detail.

[Gerhard Michel]

In addition to Stephens post:

there is a strong difference between LiPo (Lithium Polymere) and LiFe or LiFePO4 (Lithium Iron Phosphate). LiPo batteries are some risky in use as posted by Stephen; LiFes are similar safe as SLAs. I used LiPos for nearly 20 years in model airplanes, where they are nearly the only usable power source, when high efficiency and low weight are necessary. We could see some accidents even though the cells were treated well. Therefore I can't recommend these cells for models with enough available space like our tanks. LiFes however are safe, small, light weighted and can endure much higher charging and discharging rates than SLAs. My CALB cells may be charged at up to 40 amps and discharged at up to 120 amps. Therefore a charging in the field (if necessary anyway) will use quarter the time of SLA cells, if the charger is powerful enough (and the car battery doesn't break down )

[Gary Richardson]

Hi
I am also new to tanks and am at the point of deciding which battery / batteries to get for Tiger no. 13.
I like the idea of LiFePO4 with the weight saving and longer running times but am unsure whether to get 1 x 24v battery or 2 x 12v batteries, I understand that if the BMS does cut in for any reason you have to give the battery a quick charge which will then reset the BMS. If you are out in the field is it easier to do this with the 12v batteries and what method would you employ.
I do have experience with LiPo batteries from flying model aircraft and using a 12v car battery with a charger to do the recharging but not sure how this would work with a 24v LiFepo4.

Regards
Gary

[Adrian Harris]

> using a 12v car battery with a charger to do the recharging but not sure how this would work with a 24v LiFepo4.

You will get a dedicated mains charger with the battery, so use an inverter on the battery and power the charger from that.

I think I have only ever had to charge once 'in the field', due to leaving some electronics attached overnight, so what I thought was a 'fully charged' tank was actually on its last legs and only managed to get to our pitch. That time we were at a school, so had access to mains power.

I usually keep a spare battery in the van, so if a tank gets too 'tired' during the day, I just swap out the battery, or run it back to the van with the donor battery on the rear deck. I had standardised on a four way spade connector system, so could use either pairs of SLA or a single LiFe pack. Now I'm moving everything over to XT150 connectors.

Adrian.

[Gerhard Michel]

Hi Gary,

I think it's not a good idea to combine two 12 V LiFe batteries with a BMS at each battery in your tank. IMHO it is much better to either combine 8 LiFe cells to a 24 V battery with a single 24 V BMS or to spare a BMS at all, like I do. But then you must monitor each single cell when charging or discharging with suitable methods and devices. This way prevents you from sudden stops in the field like a BMS can cause, because you can get early warnings in your transmitter via telemetry, if a cell comes near to its final voltage.

[John chamney]

Thanks all for your responses , as I said at the start all the technical stuff goes over my head and I was after a simple answer which I had from Simon manning . This post seems to have gone a bit astray and not really answering the question I asked . I have looked at Phil Woodard’s posts with the chieftain and have noticed he has fitted the batteries mentioned by Simon , so I will go this route . Once again thanks for your replies although they started to go over my head cheers all

John

[Adam Osga]

I put in 2 of these: https://www.amazon.com/gp/product/B00BS ... UTF8&psc=1

I have separate maintainers on each that come through my rear hatch so I don't have to disassemble the tank to remove them. Not sure if that's a smart idea or not but not much different from maintaining my boat batteries while storing the boats in the garage over the winter.