Lithium vs AGM again but different.
Submitted: Sunday, Oct 06, 2019 at 17:56
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Member - Boobook
I have seen a lot on forums like this about the benefits of Lithium batteries, and the capacity to weight ratio is a big benefit.
I read time and time again that another benefit is that they can be discharged to 80, 90 or even 100%. So compared to 50% discharge capacity of an AGM, you get extra capacity for the same size.
E.g. a 100AH in an AGM will give 50AH of usable capacity if you respect the battery life. And you will get 80AH out of a similarly sized Lithium.
But this seems to ignore the fact that lithium batteries have much lower life cycles at deep a discharge too. People quote 2000 to 3000 cycles using lithium, but this figure is generally at........50% discharge.
Specs I looked at (which are hard to find on many manufacturers websites) show life cycles of one tenth or one fifth of the quoted cycle rate when discharged to 80% DOD - that's 200 to 600 cycles. Same as a lead acid.
So the figures that you can get 80% DOD AND 5 times the battery life seem false to me.
So it seems to me that if you need to save weight or get a higher capacity from a restricted size, then Lithiums are great. At a price of 3 times the cost.
But if you think they will pay for themselves over time then thats not right unless you limit them to 50% DOD.
Am I missing something?
Reply By: Ron N - Sunday, Oct 06, 2019 at 22:14
Sunday, Oct 06, 2019 at 22:14
Boobook, I don't think you're missing anything, and I reckon you've figured it right.
Every style of battery is a trade-off, with varying features that appeal to certain types of use. You can't have it all, in the one style of battery.
The L-A battery industry is far from dead, it's fighting back strongly against Lithium, because L-A is proven technology, it's simple technology, and it's all fully recyclable.
L-A simply has a great weight penalty against it. But it's cheap power, as long as you treat it correctly.
Keep L-A batteries cool, don't run them down excessively, keep them regularly charged when you're not using them, and they will provide good value for money.
I for one, do not believe the Lithium mantra that Lithium lasts much longer than L-A.
I've regularly had 9 and 10 years life out of L-A batteries that were looked after.
It'll be a long time before we see cheap Lithium batteries.
Cheers, Ron.
AnswerID:
628031
Follow Up By: Dave B18 - Saturday, Oct 12, 2019 at 19:02
Saturday, Oct 12, 2019 at 19:02
LA battery technology in RV's is dead for regular travellers.
LA batteries are no longer cheap against LiFePo4 drop in replacements if you look at the facts and figures.
Well you may not believe the mantra that LiFePo4 batteries
well outlast LA batteries, so I would hate to confuse you with facts.
We are seeing cheap Lithium batteries now.
FollowupID:
902422
Reply By: HKB Electronics - Monday, Oct 07, 2019 at 11:02
Monday, Oct 07, 2019 at 11:02
I can only go by what I have found with my setup.
Camper was originally equipped with two very expensive (and heavy) gel type batteries. Even though I tried to look after them as best I could, on a few couple occasions had no choice to discharge them to around the 30% SOC level. After approximately three years I found one battery had died. As we were installing more power consuming devices into the van and I was sick and tired of managing battery levels I decided to bite the bullet and replace the gel batteries with two 100 hundred Ah CALB battery packs from EV power. These have been in the camper now for three years. We are much more power hungry now from the vans view as we now leave the van plugged into the car to supply the freezer in the car so we don't have to worry about maintaining the SOC level of the cars lead acid aux. We have also used the van a lot more in the past three years than the previous three and on many occasions the SOC of the batteries has dropped to around the 30%. I now only occasionally look at battery levels to see where they and as I no longer worry about dropping them below the 50% SOC level.
I did a discharge
test on the pair a few weeks back after returning
home and preparing them for storage. I found the voltage readings of both batteries at 5% increments from 100% down to 20% were the same as they were when I received the batteries. I'm not saying they have not suffered any degradation, I'm sure they would have probably lost some capacity but as I never discharged them empty levels when I purchased them I don't know what the actually total Ah capacity was new. At this point in time they would still be at least 100Ah.
For me it was a win win scenario and I would never go back to a lead acid setup. If only I could find an under bonnet Lithium unit that I was sure could handle the heat the aux in the car would also be Lithium.
AnswerID:
628037
Follow Up By: Allan B (Sunshine Coast) - Monday, Oct 07, 2019 at 11:36
Monday, Oct 07, 2019 at 11:36
.
Leigh, I like your attitude to monitoring your batteries. They do the job and you allow them to do so without constantly peering at them.
I reflect on those who constantly review their in-and-out Ah's and SOC and send it to a smart phone via Bluetooth only to agonise over the data.
FollowupID:
902317
Follow Up By: HKB Electronics - Monday, Oct 07, 2019 at 11:56
Monday, Oct 07, 2019 at 11:56
Allan,
Some seem to enjoy that, being a techo type initially I was the same but then found it was ruining our trips hanging around
camp and chasing the sun. Much nicer now travelling and camping knowing the system can take care of its self and not having to worry about it :)
FollowupID:
902318
Reply By: Iza B - Monday, Oct 07, 2019 at 16:05
Monday, Oct 07, 2019 at 16:05
The 50% myth for LA is just that, a myth. I have a 110AH Deep Cycle AGM that weighs 38Kg. After 9 years DOM, the battery still holds 12.7 and my Low Voltage cutoff is set at 11.6. Four of us bought these batteries ex-UPS 7 years ago. We all flog the batteries regularly down to LV cutoff. Care is to recharge as soon as possible and float for at least 8 hours. The weight and physical dimensions are a pain. Hoping the thing dies soon while recycling prices are high.
AGMs in the caravan are over 6 years old now and I just use them. They hold 12.82 rested so I am not concerned in any way about trying to track cycles or DOD post using a low voltage cutoff.
LiFePo4 I have is constructed from discrete cells with a DIY BMS. Top is kept to 14.2 and low is set at 11.8. The Lithium is in a campervan specifically for the smaller size and low weight. 4 years so far and they capacity
test above nominal rating.
I ignore the cycles discussion because no one ever defines what a cycle is and under what conditions.
Li-ion is latest interest. I use the Li-ion for the electric outboard and to run the quad I am converting.
Iza
AnswerID:
628042
Follow Up By: Malcom M - Tuesday, Oct 08, 2019 at 08:06
Tuesday, Oct 08, 2019 at 08:06
Iza
A cycle is defined as a charge and discharge event.
Doesn't matter what volts are involved. Even if not fully discharged, the charge action is another cycle.
Theoretically you use them up quick when camping with constant topups from solar but you get thousands of cycles. Anyway who's counting. I just use it and enjoy teh benefits.
FollowupID:
902341
Follow Up By: Iza B - Tuesday, Oct 08, 2019 at 11:51
Tuesday, Oct 08, 2019 at 11:51
Yes, a good example of a totally useless definition of a cycle and why I never get into any discussion of Life as a count of cycles. Avoiding the discussion is a great way to avoid any of the anxiety that comes with trying to get maximum life out of a battery. Naughty of me but I often get people upset when I ask them how they work out what is that magic 50% SOC level when damage starts to occur. Having a battery is the cost of doing business. I'm doing
well the way I do it so no need to be concerned.
Iza
FollowupID:
902342
Reply By: SCUBADOO - Wednesday, Oct 09, 2019 at 09:47
Wednesday, Oct 09, 2019 at 09:47
I have no interest in "cycles" and look forward to someone attempting the impossible task of counting them for me. Outside of the lab do they even exist especially in the typical RV environment?
Our 4 cell 300Ah Sinopoly LiFePO4 battery pack has now survived 5 years of fulltime travel here in NZ. It is the only battery we have on board and also starts the 3.9l turbo diesel engine, often multiple times daily.
Cyle count? No idea but I can report the last capacity
test @ 30A last November ( year 4) was 311Ah when the first cell dropped to 2.80V and the counting stopped.
I will report back in another 5 years.
Neville
AnswerID:
628078
Reply By: Member - peter_mcc - Friday, Oct 11, 2019 at 20:27
Friday, Oct 11, 2019 at 20:27
Most of the datasheets I've seen for individual LiFePo4 cells indicates 2000 cycles at 80% discharge - not 50%. They usually give a discharge current as
well - a CALB 180A cell was 2000 cycles at 0.3C/80% (ie drawing 54A from it). A 160A Thunder Sky Winston cell was > 5000 cycles at 0.5C & 80% discharge (ie 80A discharge current).
I can't comment on assembled "batteries" as I haven't done any real research on them. But looking at just the cells it seems 2000 cycles at 80% DOD is pretty common. 5000 is possible.
I've just installed a 216Ah pack made up of 12 x 72A CALB cells in our Tvan. That gives me around 173Ah of usable capacity (80% DOD). It fits into one battery box (poking out the top a bit but I'm ok with that), leaving the other box free for storage. It weighs 22kgs.
To replicate that with AGM batteries would need 3 1/2 105Ah ones at 30kgs each - 90kgs if you had 3. The CALB cells cost $1450 delivered to
Sydney - 3 x Full River 12V 105Ah batteries would have cost about $1000 delivered.
I realise my solution isn't for everyone - it doesn't include a battery management system and I use a Manager30 to charge it instead of the usual Tvan Projecta charger. But LiFePo4 batteries can be done reasonably cheaply.
AnswerID:
628120
Reply By: Member - Stefan F2 - Tuesday, Nov 05, 2019 at 20:58
Tuesday, Nov 05, 2019 at 20:58
hm I moved to LiFePo4 about a year ago
https://youtu.be/Ea91vaNttq8
Most quality 100AH LiFePo4 will really be 125AH and 25% is reserved for battery safety and can't be accessed so my Revolution LiFePo4 100AH battery I have 100 usable AH.
If you look at the DCS LiFePo4 battery you will see that they have a cycle of 2500 at 100% DOD
https://www.deepcyclesystems.com.au/lifepo4-cell-technology/
which is 5 times of an AGM and around 5000 cycles of 40% DOD
An AGM will just die a LiFePo4 will reduce the capacity it can hold so may work much longer at a reduced capacity.
A good quality LifePo4 is safer inside the vehicle (The DCS LiFePo4, for example, uses a fire retardant electrode so they can't combust vs an AGM which has lead-acid so would leak hydrogen which is explosive when mixed with oxygen)
Depending on the LiFePO4 you can also recharge much faster (my dual DCS 100ah under the bonnet of Cruiser will be charging at 270amp from my M2k high output alternator.
It provides a constant current much better for winching and charging my camera and drone equipment.
So in my book, there is quite a few more reason for LiFePo4 beside weight savings.
AnswerID:
628548