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Forum Index : Solar : LiFePO Batteries
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| cs41 Newbie  Joined: 08/08/2016 Location: AustraliaPosts: 27 |
Hi All, I have a project where we need reliable solar power (12 v approx 200AH batteries )in remote areas (in the Pacific Islands) for emergency communications systems. Many of these locations are difficult to access because of infrequent shipping services so need reliable power supplies. Previously we have used tried and tested SLA/AGM cells but we are interested in the newer LiFePo batteries that are being advertised for RVs and 4WD vehicles. These seem to have similar characteristics to SLA and supposedly have built in protection etc. Advertised advantages are smaller, lighter and longer life / more lifetime cycles. All seem good points for the application and locations we have in mind. In this case initial cost is not so important, long life is. Not sure how they would stand possible lightning induced surges with control electronics internally. I have been involved with solar power supplies for telecoms use for nearly as long as solar panels have been commercially available, but havent had any experience with these later batteries. Appreciate anyone's experience or comments on these batteries vs SLA/AGM. Thanks in advance cs41 |
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| Warpspeed Guru  Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Smaller, lighter, and more lifetime cycles for sure. And being fully sealed, no fumes acid or regular maintenance required. They have only one real disadvantage, in that they can be very easily and permanently damaged (or destroyed) by just a single overcharging, or over discharging event. A very reliable system of battery protection needs to be used to ensure that the battery voltage never stray beyond the safe operating range. That can be achieved electronically, especially if the user has some technical knowledge. Suggest you do some research into this aspect, and judge for yourself the suitability. Not trying to scare you off Lithium Iron batteries, I use them myself for off grid power, and am extremely happy with the performance. But I have heard horror stories about university students destroying very expensive lithium batteries intended for a student electric vehicle project, by overcharging the battery just once. The batteries themselves are great, and if suitably treated will work reliably for a very long time. Cheers, Tony. |
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mackoffgrid Guru Joined: 13/03/2017 Location: AustraliaPosts: 460 |
I've been using LiFePO4 winston batteries since 2012, and I'm like them. For the most part they are easy to deal with, but as Tony says Don't over Charge, and Don't completely discharge them. Given you're looking at remote locations and you're battery requirements aren't huge, I'd be tempted to stick to SLA/AGM. Back to Winston batteries or LiFePO4, they seem much more tolerant to abuse than other lithium technologies. They're using these winston batteries in electric car conversions, see Trevs conversion, - that's tough on a battery. They don't like heat. I actually think these batteries would handle surges better than SLA, in any case I don't believe that's a problem unless the surge is massive enough to heat up the chemistry. A direct strike may be catastrophic  With good electronics, they would be better and cheaper. Cheers Andrew |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Having had some personal experience of maintaining radio communications in the Antarctic, it may be worth talking to people that have similar problems to your own. I am not sure who coordinates and manages the Flying Doctor radio system in outback Australia, but the Bureau of Meteorology also run their own small HF long distance radio network to some very remote weather stations. You may be able to pick up some valuable technical advice from one of their technical Gurus that have up to date hands on experience with lithium batteries at similar remote radio sites. Cheers, Tony. |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1122 |
Another alternative would be Lead Carbon sealed batteries, here is an example Link Here in NZ where ALL batteries are exorbitantly expensive, they cost slightly more than Gel batteries and 1/2 cost of Lifepo4 cells. Cheers Mike |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Just a few comments re Lead-carbon link ... sounds a bit tough. My understanding is lead-acid become relatively inefficient getting the last part of the charge in, ie absorb phase. Isn't 80-85% more reasonable ... LiFePO4 would have to win here but may have other degradation mechanisms ... think there is some confusion between Li-ion and LiFePO4 Charging at –7C could be a bonus, as I shut off charging below 5C for LiFePO4. What voltage is 100% DOD? I suspect one does not want to go down to 0 Volts. On re-reading I see there is a "termination voltage". So, under-voltage is as important for lead-carbon as LiFePO4 LiFePO4 are damaged by over-charging but would expect lead-carbon would be too, if proper charging regime is not followed. What is calendar-life ageing for lead-carbon? Also, cycle life …. at 30% DoD I see figures getting up around 10,000 for good LiFePO4. What % of the capacity is left after those 7000 cycles to 30% DoD for lead-carbon. Is there an industry standard for % capacity after a cycle-life test, ie 80%? Good luck with your choice. I'd suggest that you buy quality charging and monitoring equipment to look after your investment. Good luck! Edited 2019-08-06 05:25 by davef |
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| cs41 Newbie Joined: 08/08/2016 Location: AustraliaPosts: 27 |
Thanks all for your thoughts. Guess I need to do more research.. The FiFePo4 batteries that I was interested in have a built in battery management system for each battery (12v 100AH) so hopefully that would take care of charging management. Maybe with the BMS included charging etc is not so critical.. not sure. https://www.revolutionpoweraustralia.com.au/wp-content/uploads/2019/05/12v-100Ah-Lithium-Battery-Spec-v2.pdf Above is just a sample of what's currently available... maybe just sales talk or what ?? We would be getting the correct Li rated solar controllers so again maybe the problems seen with stand alone cells may not apply. Again thanks for input cs41 |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
cs41, Several things that I would want clarification on: Recommended Charge Voltage 14.6V± 0.2V 14.6 / 4 = 3.65 Volts/cell 3.45 to 3.55V gives better life-cycle BMS Charge Cut Off Voltage 15.6v 15.6 / 4 = 3.9 Volts/cell is getting rather high. BMS (top) balancing. There is an issue if you are not determining charge cut-out based on your highest cell. Otherwise, if you are basing it on the total across 4 cells then one or more cells could be above their stated BMS Charge Cut off voltage of 3.9V I am curious why there is a recommended charge voltage and then they apparently cut-off at a higher voltage. Search around the forums as I have heard negative comments about integrated battery/BMS systems. One issue is at least with individual cells if one should go faulty you might stand a chance of replacing it. Happy searching. |
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