I knew YOU wouldn't connect them without a BMS, but sometimes it's helpful to say WHY as well as what for the readers, particularly if there are explosions involved. Forgot you were a bloke, must be the ZZ top look and the mincing, it's confusing. xx
Yeah, I may have jumped the gun a bit posting the thread before doing a full write up. I'm going to edit the first post and add more info. With better explanations and links to some videos. Sent from my Pixel 4 using Tapatalk
It's got me thinking. I'd need 3 and £3k I would not spend but £1200 I would. We're due batteries and solar on the boat and been putting it off while we weigh up cost/effect. £400/110 useable (mostly) Ah makes it a no brainer for us.
The BMS is definitely needed, but once it is connected it makes the battery safer than a lead acid gel battery. Even the little 18650 cells can produce about 3kW of heat each when they thermally runaway according to NASA who had to work out what happens when a power tool in space has a faulty cell, and if the fault can be contained in one cell.. yes if the battery pack is big with lots of spacers . Not like your average 18volt DeWalt pack.. I like the idea of this battery. With a bank of supercaps the other side you wouldnt need a starter battery either...
some info on the chemistry make up of this battery. this is different to (for example) a tesla car battery Lithium Iron Phosphate(LiFePO4) — LFP In 1996, the University of Texas (and other contributors) discovered phosphate as cathode material for rechargeable lithium batteries. Li-phosphate offers good electrochemical performance with low resistance. This is made possible with nano-scale phosphate cathode material. The key benefits are high current rating and long cycle life, besides good thermal stability, enhanced safety and tolerance if abused. Li-phosphate is more tolerant to full charge conditions and is less stressed than other lithium-ion systems if kept at high voltage for a prolonged time. (See BU-808: How to Prolong Lithium-based Batteries). As a trade-off, its lower nominal voltage of 3.2V/cell reduces the specific energy below that of cobalt-blended lithium-ion. With most batteries, cold temperature reduces performance and elevated storage temperature shortens the service life, and Li-phosphate is no exception. Li-phosphate has a higher self-discharge than other Li-ion batteries, which can cause balancing issues with aging. This can be mitigated by buying high quality cells and/or using sophisticated control electronics, both of which increase the cost of the pack. Cleanliness in manufacturing is of importance for longevity. There is no tolerance for moisture, lest the battery will only deliver 50 cycles. Figure 9 summarizes the attributes of Li-phosphate. Li-phosphate is often used to replace the lead acid starter battery. Four cells in series produce 12.80V, a similar voltage to six 2V lead acid cells in series. Vehicles charge lead acid to 14.40V (2.40V/cell) and maintain a topping charge. Topping charge is applied to maintain full charge level and prevent sulfation on lead acid batteries. With four Li-phosphate cells in series, each cell tops at 3.60V, which is the correct full-charge voltage. At this point, the charge should be disconnected but the topping charge continues while driving. Li-phosphate is tolerant to some overcharge; however, keeping the voltage at 14.40V for a prolonged time, as most vehicles do on a long road trip, could stress Li-phosphate. Time will tell how durable Li-Phosphate will be as a lead acid replacement with a regular vehicle charging system. Cold temperature also reduces performance of Li-ion and this could affect the cranking ability in extreme cases. Figure 9: Snapshot of a typical Li-phosphate battery. Li-phosphate has excellent safety and long life span but moderate specific energy and elevated self-discharge. Source: Cadex Summary Table Lithium Iron Phosphate: LiFePO4 cathode, graphite anode Short form: LFP or Li-phosphate Since 1996 Voltages3.20, 3.30V nominal; typical operating range 2.5–3.65V/cell Specific energy (capacity)90–120Wh/kg Charge (C-rate)1C typical, charges to 3.65V; 3h charge time typical Discharge (C-rate)1C, 25C on some cells; 40A pulse (2s); 2.50V cut-off (lower that 2V causes damage) Cycle life2000 and higher (related to depth of discharge, temperature) Thermal runaway270°C (518°F) Very safe battery even if fully charged Cost~$580 per kWh (Source: RWTH, Aachen) ApplicationsPortable and stationary needing high load currents and endurance Comments 2019 update:Very flat voltage discharge curve but low capacity. One of safest Li-ions. Used for special markets. Elevated self-discharge. Used primarily for energy storage, moderate growth.
Bottom line what I take from that Matt is that whilst your new battery is pretty stable, it requires a less aggressive charge profile than a standard fla. So as you know I've recently fitted an AGM on the leisure side of the T3. Something I've always advised against lol because mixing battery chemistry in a linked system is not ideal. Soooo. What I've done is lowered the max input of my solar charge controller to 13.7 volts from 14.4 or whatever and I'll use the panels as the primary charge source. I've put an battery isolator in line between the starter battery and the vsr that splits alternator charge. I can then choose on a journey if I feel the lb needs a bit of a boost. It seems your lithium set up perhaps needs similar protection but to be honest is way way more efficient than lead acid tech. I'm loving the weight advantage yours has and the size coz for us space is a premium. What's not to like. I'm looking forward to the discharge/recharge cycle tests we chatted about...may have to start saving my pennies
Weight comparison. LiFePo4 battery 10.2 kg 115ah Halfords leisure battery 26.4kg Sent from my Pixel 4 using Tapatalk
And that's just a cheap battery. My very expensive 200Ah boat batteries were 70Kg each and probably compared in useable capacity! They lasted the previous owner 10 years living on the towpath with engine alt and a generator so were good, but not 2,000 cycles and 70KG compared to 10kg... I think they go for about £450 best price now so yours are cheaper too.
I like the idea of this, might give it a try when our leisure battery packs up. My solar controller has a LiFePo mode so should be good to use as well Sent from my Pixel 4 using Tapatalk
How does it cope with battery memory ? I remember big problems with certain battery types losing capacity when the didn’t get a full discharge and charge cycle. Might have been nicad? Sent from my iPhone using Tapatalk
We've had lifepo4 batteries on our narrowboat for over 18 months now (off grid liveaboard). Bought some used cells from www.ev-support.co.uk, and sourced all the parts online. Total cost around £1000 for 320ah capacity (but that included several additional improvements not strictly necessary). Best investment by far in 10 years of boat ownership. No detectable loss of capacity in 2 winters usage, if anything we've ended up increasing our electrical usage due to the ease and speed of charging. Old batteries would last about 12 months before being so down on capacity as to be useless, and that was with 500w solar, and charging for around 4-6 hours a day by generator in winter. Our winter charging has now been cut to around 1-1.5 hours per day. They work superbly with solar as soak up any charge until full. You do need to be very careful if charging from alternator though - most alternators are not designed to run at max output and can be quickly destroyed charging lifepo4 batteries. It is also recommended not to charge them below 0C unless very very slowly. Probably not an issue in campers, but definitely a consideration for us. That is why we decided to relocate them to just inside the bedroom at the back of our boat. I think they are generally safer than lead acid batteries when installed correctly (I've seen the results of a lead acid explosion!). Be mindful of using default lifepo4 settings on chargers and solar controllers though, most will result in charging at far too high a voltage! General consensus seems to be to limit charging voltage to max of 14.0v, with several people opting to charge at 13.8-13.9v to give extra safety margin. The best advice I was given (and the hardest to take onboard!), was to completely forget EVERYTHING you already know about battery charging and maintenance and start from scratch! Finally a point on safety, these lithium batteries DO NOT explode. If overcharged, you will ruin them, and they will swell and vent electrolyte, but unlike other lithium chemistry types, they will not explode or burn. They are by far the safest type. They can however produce very high discharge currents, so extra care is needed to avoid accidental short circuits such as dropping spanner across terminals etc, that will produce some spectacular sparks! Happy to answer any questions based on my research, experience and installation. Tom
Not a problem at all. Ours have generally been cycled between 20-80% all winter for the last 2 winters, with no detectable loss of capacity. Also do not suffer from sulfation which is by far the biggest killer of leisure batteries. Reports online are that these are capable of 10000+ cycles if treated gently.
It’s always good to hear some real world experience especially with any technology that requires an initial large financial outlay. May I ask what charging system your using? This is going to make for a very interesting thread Sent from my iPhone using Tapatalk
Currently (in this nice sunny weather) all charging is by 500w solar connected via Tracer MPPT charge controller with custom settings. Winter charging is via boat engine, with twin 70a A127 alternators, controlled using an Arduino based alternator controller on 1 alternator, and split charge relay for 2nd alternator bulk charging (you did ask). Can go into more detail if anyone is vaguely interested. Quite complex, and although useful and does everything I need really well, would opt for simple (read cheaper ) system in future. Back up winter charging is via petrol generator and 40A Sterling pro charge ultra battery charger (again, with custom settings). I learnt the hard way about not over driving the alternators and have now slightly dialed back the charging rate. Have a much simpler system in mind if I was to do it again, and will probably use that in our camper if we ever have enough money to upgrade from discarded boater batteries Tom
Ahh your a boat dwelling person There are big differences between van living, boat living and leisure use boats and vans. Like I said this is going to be a very interesting thread. Every battery and charging type has its pros and cons For a lot of people on here I’d imagine it’s a balance between cost, simplicity and battery longevity. This comes from the guy that has moved house many many times but each move has taken ten car batteries with him each time and charged them four times a year. It might have seemed daft to most people but during power cuts and for remote work coupled with the inverter we’ve carried on when others have struggled. Sent from my iPhone using Tapatalk
I thought the issue was that the AGM needs a slightly higher peak charge voltage 14.4 vs 14.2 volts than the wet battery, so the result of putting them both in parallel is that you succeed in boiling out the wet battery and not quite charging the AGM. With them separated, just set the solar setup to AGM and as you say enable the VSR link for driving.Or just fit a small stop/start AGM on the starter side in the longer term and then forget it.
You are correct, of course, regarding the bulk or topping phase requirement being slightly higher on AGM than FLA wet batteries. However, AGM are sensitive to over charging in the float phase. The solar panel is maintaining float at 13.7 on the AGM, the battery switch allows me to bulk charge manually. I think we're saying the same thing Mike... I can alter the charge controller to whack a higher bulk charge into the AGM every now and then. It's needs a bit of management running with different chemistries. Not sure an older alternator only system would be ideal for running an AGM only system.. Anyway, Matt's lithium leap looks pretty interesting so far don't you think?
