Chris Bott - Moderator

Does anyone have any figures on current capability of different capacity nimh's? I keep hearing the advice "for a receiver pack, get the highest capacity AA's you can" I'm not convinced. As we all know, 4 or more servos can take a high instantaneous current at times during a flight. So the amount of current the battery can deliver is very important. I believe that as a general rule, for a AA's at least, to get higher capacity they use thinner plates to pack more in, and thinner plates mean lower current capacity.

Within the DeWalt pack, there is a device that is connected to every cell junction. It is immersed in opaque epoxy so its impossible to know for sure what it is. But being connected to all cells like it is, it is almost certainly a balancer.  Which says a lot about the need for balancing.... PS I have on test a Lead Acid battery de-sulphator. This is an electronic device wich claims to reverse the main cause of ageing in Lead Acid batteries.  It takes weeks to work, so I cant report any success or otherwise yet. 

I just stumbled across another car/leisure battery supplier with many more types than I have ever seen. Field batteries for most pockets here. But even then there isn't one that says Engine Starting and Deep Discharge like is on the side of the one I have.  another battery supplier

I should try and get some A123's then David, it might add another dimension to your review

Hi David Unfortunately I don't know.  He's part of our "wednesday crew", the lucky ***s that don't have to work any more. I can'tmake it on a Wed and have only seen the test flight. That wasn't timed but seemed nice and long... If I remember right (and the memory isn't as infallible as it was) It was set up at 13V and 30ish amps giving 400W.  30A from A123's gives almost 5 minutes Wide Open Throttle. So flight times will depend totally on where the throttle stick is for most of the flight. He's an IC flier and is very satisfied with this setup. How much are you putting back into the3200's ?  Don't forget that you can use every last drop of the 2300 fromA123's, at full power if required. And a 4S A123 setup will be higher volts lower current than a 3S LiPo for the same power. (But heavier  of course)

One of my club colleagues built one of these and I recommended a 4S A123 battery from Puffin Models He bought two for under £90 and an A123 compatible charger from Hobbycity. They fit the Mentor battery bay perfectly and fly it superbly. He can charge one while he's flying on the other so can fly on these continuously all day. They are much safer and last much longer than LiPo's too. (But are a little heavier) And Puffin items nearly always arrive next day. This is a perfect model to try them out in.

Peevie I wouldn't put much faith in data on other LiFe's (as you already mention). It seems that many of the advantages off A123's is the very small particle size (the word nano keeps cropping up). This is a proprietry patented manufacturing technique. The advantage is so huge that they have attracted millions $ investment from vehicle manufacturers. Have a look at this link for example.. which includes the line:- Excellent performance over a wide temperature range (-30 to 60 degrees C).

Argh... just peeked at another thread after a long typing session and its all gone from here, even opened a new tab!  Oh well... heres an abridged version:- A123's are fine being cooled after charging, it is not an issue. When I started with them I bought the lightest car battery I could find for about £25, thinking I needed the current capability. This worked well for a season. For the last 18 months I've been using a hybrid Leisure/Starting battery as designed for use in Motorhomes for Engine starting and deep discharge while camping. Note: Deep discharge seems to mean 50% of capacity. I think they can be discharged further if its during starting, but would then be charged immediately while driving. There has been some discussion about charging sources on my A123 thread.. A123's at end of life.

many thanks Pete, plenty to think about there while I get squirreling away some pennies... Cheers Chris

Sounds a reasonable idea, especially if its lighter to carry. But if the cost is the same as quite a few leisure batteries, then I'll stay with what I have for now.  It reminds me that my very first A123 charges were by directly connecting my old LiPo's to my flat A123's. The LiPo's were beyond flying the planes, but they discharged to the right voltage for a fully charged A123 pack.   Not recommended without very close monitoring, but it did the job, Till the DIY chargers got built.

Guys As a complete hotliner numpty, I've always fancied a try, but wouldn't know where to start. Is there any low cost way to dip ones toe in the water??

You seem to have come up against the same issue as me now with using A123's, and thats the charging source is limiting! We've thought of generators at the field - (would we only be allowed to during noisy I/C sessions??) It would be interesting if anyone could find a lead acid battery that will last for more deep discharges. I guess maybe a true leisure battery might, as they are made to deep discharge in a caravan or boat etc. But what current will they supply without being damaged? Don't forget that if you charge A123's at 10A and the charger is doubling the voltage, Then it has to be taking at least 2x10 from the 12V source to do it! 

I use a Deans shorting plug to arm big scale models. To charge I have a single 2mm socket near to it. My +ve charge lead uses 1 connection on the deans - the battry side. (I cant plug that in wrong as the deans only goes in 1 way. My -ve charge lead goes into the 2mm  socket.  Also means I cant possibly charge with the arming plug in.

Isn't Google great   now I have something to search for.: What does CCA mean? Cold Cranking Amps is a rating used in the battery industry to define a battery's ability to start an engine in cold temperatures. The rating is the number of amps a new, fully charged battery can deliver at 0° Farenheit for 30 seconds, while maintaining a voltage of at least 7.2 volts, for a 12 volt battery. The higher the CCA rating, the greater the starting power of the battery.

just came to me.  Is it Cold Cranking Amps?  a measure of a starting battery for starting a car engine???

dod means depth of discharge so 100 cycles if you discharge to half empty.  No idea what 600 cca means though

Tom your experiences sound promising. It does sound like the cells may have been reduced in capacity a little during the soldering though..  10S2P sounds like an awful lot of batteries/weight!  The extra wot is about a 10lb model isn't it? My rule of thumb has been to use 1cell per 100W and therefore about 1 cell per pound. Adding more if power or duration arennt sufficient. You might be better with 6S2P or 8S2P A clubmate just electrified the new YT International Adrenaline90 with 8S2P giving over 2KW max and apparently it is "amazing"

Hi John Are you concerned about LiPo batteries because of either the safety aspect (charging fires) or the longevity and ease of which we can render them useless (by over discharging etc)? Either way, the A123 batteries absolutely address both these concerns. The manufacturers claim that the chemistry is inherrently safe. Have a good look round A123 Systems website  Where they say "A123Systems is one of the world's leading suppliers of high-power lithium ion batteries using our patented Nanophosphate™ technology designed to deliver a new combination of power, safety and life." I can vouch for the robustness and long life. See my thread A123 cells acytually at end of life.

And, the battery can be used in other models...

Now for the items for a well powered 40 sized model. Franks 4250A-700 motor is ideal at about $30A Super Simple 60A ESC is under $20 (this replaces a throttle servo too)a 6S A123 Battery from Puffin under £70Sundries like balance charge adapter lead and some plugs etc to connect battery to speed controller say another £5Total in the model $30+$20 = £35  add £70 and £5 comes to £110 to put in the plane. This is for a setup with only one battery, but it will charge safely, without taking it out of the model. It will charge in 10-20 mins depending how much you took out. It will suffer less from the cold and gives full power right to the end of the flight. It will last much longer than a LiPo. A second battery would mean pretty much continuous flying... I hope that gives you some idea of the costs. It also means no more buying of fuel too, which is not insignificant these days.

OK there are a number of parts to this if you are starting from scratch. NOTE: I'm going to aim at the very cheapest by buying from China direct. I don't always do this as I believe we should support the UK too. There are suppliers in the UK that sometimes get close to these prices. I'll do prices in $ and convert at the end. You'll need the kit that isn't directly involved with the model, and then the models electric setup. A. List of common use kit for all your models:- A charger , many and varied. If you want to charge A123's in 20 mins at the field then how about Under $80 ChargerA supply battery to charge from. I use a Leisure battery and suorce from the UK. From Ebay say £60Something to measure volts/current/power so you know you are not overloading any of your powertrain. This one even has a built in servo tester for controling the speed controller when testing. $35 power meterI make that under £80 +£60 = £140  You'll need these or similar whichever electrics you do. 

John  Well done for sticking with this, many people either give up before starting or "have a go" and give up at the first sign of problems.  I have many 40 sized and above electric models. And it doesn't have to be that expensive. Although starting from scratch, the costs can add up right at the beginning. I would recommend the use of A123 batteries at this size of model. Others think they are too expensive. But I think any beginner would struggle to get more than 50 flights out of his first set of LiPo's, and far less of any of a number of simple mistakes are made. Whereas A123's are likely to give to 500 or more. A 5S (yes 5Cells in series) Lipo could cost say £40-£50  Whereas the equivalent 6S A123 is around £60 from Puffin.   I'll do a complete example "low" cost setup in the next post, see what you think about the cost.

Having said that, these people seem OK on price and delivery, theres loads more on Ebay too. Ebay seller 85Ah battery

Peevie the trouble with buying on line is that postage costs are very high. Try your local Motorhome dealer... 

Because of the currents involved in 200W plus A123 charging, I've been using a 110Ah Hybrid Leisure/Traction battery for 18 months. This is now the main limiting factor in how fast I can charge 6S2P or 8S2P packs. I can separate the packs into 1P packs and charge with 2 chargers, but would really need 2 110Ah batteries then and that's just getting too much to take across to our pitts area. The Hybrid battery is designed for motor homes where it is able to do high currents for engine starting and deep discharge for camping.