jimmy
Junior Member
Posts: 20
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Post by jimmy on Mar 4, 2020 23:56:25 GMT
I could look around for 3 for sale second hand and wire them in parallel that would give me 90 amps
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jimmy
Junior Member
Posts: 20
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Post by jimmy on Mar 5, 2020 0:00:58 GMT
One thought is if you can get the stirling 30 amp for £150 and the bigger 60 amp one is over £300 pound what is in these things to justify the massive price hike
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Deleted
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Post by Deleted on Mar 5, 2020 0:12:38 GMT
One thought is if you can get the stirling 30 amp for £150 and the bigger 60 amp one is over £300 pound what is in these things to justify the massive price hike The comment that they are pricey is true enough. But if you want to charge at 90 or 150 amps, I think more information is needed to see how that might be safely accomplished. My guess would be that you would need to have a battery bank of multiples of 12v to do this.
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Post by Telemachus on Mar 5, 2020 0:23:27 GMT
One thought is if you can get the stirling 30 amp for £150 and the bigger 60 amp one is over £300 pound what is in these things to justify the massive price hike The comment that they are pricey is true enough. But if you want to charge at 90 or 150 amps, I think more information is needed to see how that might be safely accomplished. My guess would be that you would need to have a battery bank of multiples of 12v to do this. One of the main advantages of Li is its ability to charge fast. Up to 1C, or even more, although I’m not sure that is a good idea for longevity. We would have 450Ah or so, 1C therefore being 450A. 4C would be 112A which is pretty conservative. I will plan on about 125A from our 175A alternator to avoid it getting too hot. Once I have finished developing my control system I doubt it will cost more than £100 in components. Controlling the alternator (by means of adjusting the few amps in the field current) is the elegant way to do it, not inserting some rather complicated and expensive power electronics in the high current path.
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Post by JohnV on Mar 5, 2020 8:43:00 GMT
As I understand it one of the limiting factors is heat ....... because of the difference in the way they charge it means even a comparatively low charging rate can, in practical terms, be adequate ...... it continues to charge at the maximum rate until it is virtually full.
If you take Nick's figure of 450 Ah assume 20% left (ie flat) that's a requirement to charge 300 Ah ..... that's a days cruising with a 30A charger.
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Deleted
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Post by Deleted on Mar 5, 2020 12:57:18 GMT
As I understand it one of the limiting factors is heat ....... because of the difference in the way they charge it means even a comparatively low charging rate can, in practical terms, be adequate ...... it continues to charge at the maximum rate until it is virtually full. If you take Nick's figure of 450 Ah assume 20% left (ie flat) that's a requirement to charge 300 Ah ..... that's a days cruising with a 30A charger. Thanks John. Is it also true that this rate of charge is only possible with LiFeP04 batts and that if (say) 50a was presented to a pb batt it would result in a shorter lifespan?
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Post by peterboat on Mar 5, 2020 13:03:50 GMT
My LifePo4s [same as Johnvs and Krises] are charged by solar, recently I have had 80 amps going in @ 24volts these batteries just take it all!! Its interesting to watch as they get fully charged its like somebody has flicked a switch and the amps drop to 2-3 amps and then nothing. put the electric kettle on and straight back up to 80 amps
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Post by kris on Mar 5, 2020 13:08:02 GMT
As I understand it one of the limiting factors is heat ....... because of the difference in the way they charge it means even a comparatively low charging rate can, in practical terms, be adequate ...... it continues to charge at the maximum rate until it is virtually full. If you take Nick's figure of 450 Ah assume 20% left (ie flat) that's a requirement to charge 300 Ah ..... that's a days cruising with a 30A charger. Thanks John. Is it also true that this rate of charge is only possible with LiFeP04 batts and that if (say) 50a was presented to a pb batt it would result in a shorter lifespan? my names not John but, leadacid just won’t take the 50a for very long or at all. The amperage the battery takes dropping as it charges up. The difference is the lithium’s will take the full charge for all of the time until full or 80% if you want to prolong their life.
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Post by Telemachus on Mar 5, 2020 13:08:13 GMT
As I understand it one of the limiting factors is heat ....... because of the difference in the way they charge it means even a comparatively low charging rate can, in practical terms, be adequate ...... it continues to charge at the maximum rate until it is virtually full. If you take Nick's figure of 450 Ah assume 20% left (ie flat) that's a requirement to charge 300 Ah ..... that's a days cruising with a 30A charger. Thanks John. Is it also true that this rate of charge is only possible with LiFeP04 batts and that if (say) 50a was presented to a pb batt it would result in a shorter lifespan? A Pb battery’s ability to take charge depends on various things including temperature, but mostly on its state of charge. You simply cannot force 50A into a Pb battery that doesn’t want to take it. Well you can using very high voltage, but then most of the “charge” just goes to gassing (converting water to H2 and O2). The battery is in charge! (Pun intended). So whilst force charging them probably does reduce life, the main issue is that they simply refuse to take it. By contrast Li batteries can pretty much hoover up all you can give them, right up until they are nearly full.
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Deleted
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Post by Deleted on Mar 5, 2020 13:20:14 GMT
So...instead of desirable but hugely expensive LiFePO4s (you have to admit the cost is staggering), I sometimes have imagined (and I could be wrong) that to maximise charge acceptance it would be better to have (say) two 60AH pb batts linked in series to form one 24V batt than one 120AH 12v batt. Is there any validity in this?
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Post by Telemachus on Mar 5, 2020 13:40:41 GMT
So...instead of desirable but hugely expensive LiFePO4s (you have to admit the cost is staggering), I sometimes have imagined (and I could be wrong) that to maximise charge acceptance it would be better to have (say) two 60AH pb batts linked in series to form one 24V batt than one 120AH 12v batt. Is there any validity in this? No. A battery’s ability to absorb charge, other things being equal, is proportional to its capacity. The 120Ah battery could absorb twice the current of the 60Ah ones. But since the 60Ah ones are set up for 24v, you only need half the Ah to get the same Wh. So it would all pan out the same.
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Deleted
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Post by Deleted on Mar 5, 2020 13:48:50 GMT
Whatever happened to Peukert and his laws ?
I remember the highly technical discussions on canalworld with the famous gibbo and the equally famous monkey puzzle tree man Chris w. They were quite amusing.
The people and their views were funny in equal measure.
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Post by JohnV on Mar 5, 2020 13:54:14 GMT
er ...... got lost so puket
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Deleted
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Post by Deleted on Mar 5, 2020 15:19:08 GMT
So...instead of desirable but hugely expensive LiFePO4s (you have to admit the cost is staggering), I sometimes have imagined (and I could be wrong) that to maximise charge acceptance it would be better to have (say) two 60AH pb batts linked in series to form one 24V batt than one 120AH 12v batt. Is there any validity in this? No. A battery’s ability to absorb charge, other things being equal, is proportional to its capacity. The 120Ah battery could absorb twice the current of the 60Ah ones. But since the 60Ah ones are set up for 24v, you only need half the Ah to get the same Wh. So it would all pan out the same. So when batteries are used for propulsion, the utilisation of multiples of 12v is advantageous only in terms of output? I was under the impression that such a config also allowed for faster charging times (which now appears to be entirely a facet of the type of batt being used).
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Post by peterboat on Mar 6, 2020 9:04:08 GMT
No. A battery’s ability to absorb charge, other things being equal, is proportional to its capacity. The 120Ah battery could absorb twice the current of the 60Ah ones. But since the 60Ah ones are set up for 24v, you only need half the Ah to get the same Wh. So it would all pan out the same. So when batteries are used for propulsion, the utilisation of multiples of 12v is advantageous only in terms of output? I was under the impression that such a config also allowed for faster charging times (which now appears to be entirely a facet of the type of batt being used). I use LifePo4s for propulsion the alternatives are 2 volt traction batteries, but they charge no faster than normal 12 volt Pb batteries, and the life of them is very poor in comparison to LifePo4s
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