# Need 80-100ah 4s 12v lithium



## GizmoEV (Nov 28, 2009)

You are mixing up amps with amp-hours so I'm going to assume you mean amp-hours when you say amps except when you say, 


hugocraft said:


> Looked at regular deep cells but they cant handle the 52amps I pull from my powersupply when I parallel charge all 4 lipos at once with my two chargers.


I don't know what "regular deep cells" you are talking about buy both my 8V T-875 pack and a 6V UB2200 pack had no trouble pumping out 250A on my hill climb home. All I can figure is you are talking about some marine battery or something. A golf cart battery will have no trouble keeping up with such a low current as 52A. There are also high quality AGM batteries which will do even better than that. Just make sure you have the correct charging algorithm for them. Those will be your cheapest route.

So I keep looking at the lifepo4 batteries and figure I need an 80ah-100ah and a 4s would work since my chargers are rated for up to 16vdc input. 

For LiFePO4 cells use the nominal voltage of 3.2V to calculate Wh capacity. This means that an 80Ah cell will have 80Ah * 3.2V = 256Wh. For a 4s pack that would be 80Ah * 3.2Vpc * 4cells = 1024Wh. 75% of that is 768Wh.

I think your calculations for your lipos might be right if you mean 3.6Ah * 0.70 = 2.52Ah (not amps!) Your 6s battery will take approximately 63.5Wh to recharge. Since we figured that your recharging battery has 768Wh of capacity you don't have to convert the 63.5Wh into equivalent Ah of your recharging battery. For losses and to be conservative say you need 75Wh for each of your batteries so for your 8 recharges you would need 600Wh so it does look like an 80Ah pack of 4s LiFePO4 will do the job.

You could get something like the Trojan T-1260 which has 113Ah at the 5 hour rate. This might just make it. The 5 hour rate for this battery is only 22.6A so you might be better off with the T-1275 which is 120Ah at the 5 hour rate or 24A so at 52A you should be able to accomplish what you want. The battery, however, is 82lbs! If you don't have to haul them around much you might just be better off getting a couple T-105 batteries. These are rated at 185Ah at the 5 hour rate so they will definitely handle 52A for charging and have plenty of energy left over if you happen to have a longer flying day.

Otherwise, you are into about $1.25/Ah for the LiFePO4 cells.

Great flying, BTW! How long did it take you not to get disoriented? I knew when I finally "got it" flying RC planes when I landed on a very windy day and realized I didn't have to think about what was left or right from the plane's perspective. That is simple compared to what you are doing!


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## hugocraft (Jan 6, 2012)

GizmoEV said:


> You could get something like the Trojan T-1260 which has 113Ah at the 5 hour rate. This might just make it. The 5 hour rate for this battery is only 22.6A so you might be better off with the T-1275 which is 120Ah at the 5 hour rate or 24A so at 52A you should be able to accomplish what you want. The battery, however, is 82lbs! If you don't have to haul them around much you might just be better off getting a couple T-105 batteries. These are rated at 185Ah at the 5 hour rate so they will definitely handle 52A for charging and have plenty of energy left over if you happen to have a longer flying day.


Well I like the idea of having 185ah deep cell that can handle 52a no problem. I need to look at the price and a charger. I could just leave it the back corner of my ford ranger bed and just plug it in when I get home. 

I haven't looked at regular deep cells in a while because I thought I couldn't pull any amps with them and that they don't like being discharged more than 30% down. Meaning that I wouldn't want to use more than 30ah out of an 100ah deep cell. I'm probably wrong but thats why I started this thread to get more help. 

But this is tempting:
http://www.atbatt.com/product/24246...ies&utm_campaign=frog1&utm_term=TROJAN-T-1275


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## GizmoEV (Nov 28, 2009)

hugocraft said:


> Well I like the idea of having 185ah deep cell that can handle 52a no problem. I need to look at the price and a charger. I could just leave it the back corner of my ford ranger bed and just plug it in when I get home.


You could also have a hook up to your truck battery so that if you needed more charge you could start your truck up and then connect the two. You could just use regular jumper cables. Depending on your trip home you might be able to fully charge it by the time you got home but running it on a proper plugin charger would be better. Look for a charger which has temperature compensation so it will be properly charged during all seasons of the year.



hugocraft said:


> I haven't looked at regular deep cells in a while because I thought I couldn't pull any amps with them and that they don't like being discharged more than 30% down. Meaning that I wouldn't want to use more than 30ah out of an 100ah deep cell. I'm probably wrong but thats why I started this thread to get more help.


It is nothing to pull 500A from a battery in an EV! You just don't want to do it for very long because things heat up. Soon after I bought my Gizmo I found a melted battery post. Fortunately I caught it in time and learned to always torque the terminal bolts on a regular schedule.



hugocraft said:


> But this is tempting:
> http://www.atbatt.com/product/24246...ies&utm_campaign=frog1&utm_term=TROJAN-T-1275


Did you check out the Application specs pdf listed at the bottom of the page? Note that there are three capacities listed for the T-1275 of 280Ah, 102Ah, and 70Ah at 25A, 56A, and 75A, respectively. The higher the current draw the lower the Ah capacity available. Since you only need 53A you should be able to get by with this battery. Just make sure that after a discharge of more than 5-10%, or if it will be sitting unused for a long time that you hook it up to a charger when you get home so that it won't sulfate, resulting in lower capacity. Properly cared for this battery should last for many years.

On second thought, you should get the DC-500ML. It is only 332 lbs.


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## Ziggythewiz (May 16, 2010)

GizmoEV said:


> You could also have a hook up to your truck battery so that if you needed more charge you could start your truck up and then connect the two. You could just use regular jumper cables. Depending on your trip home you might be able to fully charge it by the time you got home but running it on a proper plugin charger would be better. Look for a charger which has temperature compensation so it will be properly charged during all seasons of the year.


I think a couple golf cart batteries would work great, tied down in the corner or something. You can use a battery isolator to connect it to your alternator, and probably not have to worry about charging it.


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