Best choice of battery type for cost/weight/power |
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Jack1991
Registered User Joined: 05 February 2020 Location: Bristol Status: Offline Points: 491 |
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Posted: 19 February 2020 at 9:43pm |
Just wondered what choice of battery people are using or reccomend?
Im building a 12v off grid rig, consisting of car amplifier & car head unit, speakers/subs. Im not clued up on the battery front. I only really understand that the higher the AH the better for lasting longer. Car batteries are heavy though! Wondered what other options i got? -Ideally id like lightweight as i want to tow my rig on my bike (not all the time but sometimes) to get from A to B so weight is an issue. - Amplifier is Pioneer Class D and will be putting out 2x 300w rms. - Would running multiple batteries in parrallel or series be better than 1?
Edited by Jack1991 - 19 February 2020 at 10:27pm |
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imageoven
Old Croc Joined: 28 March 2007 Location: Scotland Status: Offline Points: 2186 |
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Cost / weight / power is horses for courses - it entirely depends on application. From your other thread it looks like weight is a major issue for you, so you need to do some research into the various lithium technology batteries, these offer a far greater power density (they are lighter) than lead acid. They are more expensive and 'complicated' - 12v lead acid batteries are what much kit is designed to work with, so are much more plug and play. in terms of Lead acid batteries, car starter batteries are not ideal. They are designed to give lots of energy quickly. 'Leisure' batteries are better (for this application) as they are designed to give out energy for extended periods and survive greater discharge. Remember you don't need all you energy in one place all the time. You can use multiple smaller batteries and transport them separately and change when necessary. A big lead acid battery is fairly easy even off road with a decent sack truck. 7Ah lead acid batteries weigh about the same as 4 cans of beer so are easy to carry in a rucksack (give one to all your mates to carry). |
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Keep pushing on, things are gonna get better.
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imageoven
Old Croc Joined: 28 March 2007 Location: Scotland Status: Offline Points: 2186 |
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If you are running standard car amp (s) then you need to give them a nominal 12v so any multiple batteries used should be in parallel (assuming 12v batteries). it is a good idea to only parallel 'matching' batteries ie those of the same capacity and state of charge. This is to prevent one battery charging the other. Many of the amplifier boards available from suppliers like Sure need higher voltages to get full power, so you may want to use batteries in series for these, or voltage boosters such as buck converters.
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Keep pushing on, things are gonna get better.
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Jack1991
Registered User Joined: 05 February 2020 Location: Bristol Status: Offline Points: 491 |
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Thank you imageoven for both of your in depth replies ๐๐๐ผ
I will take a look at 12v lithium batterys, im new to anything like this so easier would be better if they are complicated to do, but as long as i got good instructions i should be alrite. 12v Deep cycle batteries is what i have been mainly looking at as the vast majority seem to use these and good that they are "plug & play" but yeh as weight is an issue the lithium route might be better (if i can get my head around it). If not last resort is like you said get mates to bring batteries down to save the weight rather than all in one go. Im led to believe this way of working out how much AH i need is correct? Amplifier output wattage RMS, divided by volts So in my case 600w รท 12v = 50AH I assume thats playing at full volume so if using a 50Ah battery it could last longer than 1 hour if played quieter? I will also have a bluetooth car head unit linked up for the input too though but id imagine they dont require much amps? If thats not correct could you help me out please? As i need to make sure im in the right ballpark figure for AH. Cheers ๐๐๐ผ
Edited by Jack1991 - 20 February 2020 at 11:40am |
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Monkeys
Registered User Joined: 30 August 2012 Location: Melbourne - Aus Status: Offline Points: 429 |
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I've just done a decent amount of research on this recently, and in my opinion Lithium Iron Phosphate (LiFePO4) batteries are the way to go at the moment. From my view they offer the best balance between weight, capacity, reliability and affordability.
They are more expensive than Lead Acid batteries per watt hour, around $8-10 per amp hour (AUD, not sure about other currencies) vs about $2-3 per amp hour for lead acid. Seems like a big price difference initially, but the problem with lead batteries is that they can only be discharged to around 40% before they need to be recharged or they will get permanently damaged (or even no more than 50% in a lot of cases). If you ever fully discharge them it will really damage them badly, do that a few times and they are basically cactus. LiFePO4 batteries can be fully discharged without damaging the battery at all so they are much more durable in that sense. Even the cheap LiFePO4 batteries come with a 2+ year warranty (some have 5 year!) for that reason. The "rated" capacity of lead batteries is fairly misleading, since you can't (or shouldn't if you want them to last at all) really deplete more than 50-60% of that capacity. With that taken into account LiFePO4 batteries are only slightly more expensive than lead per "usable" watt hour. Not to mention LiFePO4 are about 40% of the weight for the same rated capacity (about 20% of the weight for usable capacity). Also, LifePO4 can be used in any orientation whereas most lead batteries need to be kept upright (except LGM, but even then they say you should keep them upright ideally). Steer clear of Lithium Ion for anything other than small scale stuff at the moment I reckon. They are way too unreliable and there are heaps of dodgy cheap batteries on the market. The cheap 18650 lithium ion cell based batteries look tempting but look at a few reviews and see that they often don't last more than a few cycles before they fail. Hard to find warranties on any lithium ion batteries for this reason.. My $0.02, hope it's helpful =) Edited by Monkeys - 23 February 2020 at 11:12am |
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carlosdelondres
Registered User Joined: 21 June 2012 Location: London Status: Offline Points: 243 |
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You can pick up used LiFePO4 cells on ebay or gumtree, need a bit of knowledge to use but nowhere near as dangerous as lithium ion. Still fairly easy to ruin them though! Building a 2P8S 25.6V/120Ah battery for mobile sound out of recycled cells at the moment. Here is a good bit of info on charging and setup (the other lithium battery posts on the site are well worth a read as well). |
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