Well I see that at 22 amps or 1C , the SLAs will get < 40% capacity. Capacity is 22 AH so only about 8 Ah.
The LIFEPO4s are 19 Ah but only go about 5 or 6 miles and are at around 25% capacity according to the meter ???????
Not sure but think a SLA battery is considered empty at 11.5V right ?????
If I measure the SLAs after 6 miles or a simple trip to Wall-Mart and back and they are > 12V or close to 12.5V then all those graphs are wrong. I will be doing that next week.
My guess is the SLA will be empty or around 11.5V * 3 = 34.5V somewhere around 15 miles at 1C and the LIFEPO4 packs will trip the LVC before 10 miles at 1C.
I will want to use a phone app. to measure miles and be like a couple blocks away when the LVC happens though.
I have not rode SLA in awhile but know they will go farther than my LIFEPO4 packs. No graph will tell me different. I will need to measure voltage and test the theory out in real time.
Not sure if I should spend the money to build a 36 Ah - LIFEPO4 pack. If the 19 Ah pack I got now has a usable range of < 10 miles then I am paying $400 to get a 20 mile pack. Not sure if worth it. I would like some honest answer from anybody who has run LIFEPO4.
The graphs DA. posts and the graph I downloaded show LIFEPO4 to have tons of capacity. It shows that the 19 AH packs I got now should go 20 miles when in reality the LVC will trip at 10 miles and will be pushing it home that far. It is why I ordered SLAs. I know this as I pushed the Currie 3 miles home the third time I used the LIFEPO4 packs and it was about 10 total miles.
How would the graph look if I ran the SLAs in parallel with 12S - LIFEPO4 ??????? Would there be any benefits in doing it ?????
I am NOT letting other ES members do all the work doing the research this time. I found this page and see that it has been done before. I would still like some feedback as these pages are over 10 years old. 2008. Almost 15 years ago.
https://www.endless-sphere.com/forums/viewtopic.php?t=7740
by safe » Dec 06 2008 9:48am
The whole point of running the SLA's in parallel is to cut the "C" rate. So it makes no sense to run them separately.
But the other issue is about balancing of the two paths (SLA and "Other") and what happens when the SLA's start to drain in capacity.
I've found that the SLA's do indeed "balance" with the "Other" chemistry, but that balancing simply adjusts the rate that the two paths drain. If one chemistry is more energetic than the SLA's (like NiCads, NiMh, or LiFePO4) they will prevent the "sag" by participating more in the delivery of energy.
The "problem" is that when the SLA's finally do start to run low (as the overall system runs low) the individual cells revert back to their normal tendency to become imbalanced. The "runt" cell is still there no matter if you ran pure SLA's or with a parallel assist.
The moral of the story is:
"Putting SLA's in parallel with another chemistry does NOT eliminate 'runts'."
WOW !!!
The runt cell. I never even knew there was such a thing until I just read that.
However if it can happen even when NOT in parallel then I guess it wont make any difference.
I am thinking that in parallel I could get a performance increase from the rear chain as less SAG so more usable wattage going to the controller
The one guy on that post has a switch for putting in parallel or NOT. Since fast charging is NOT possible for the SLA without damage my idea would be to plan my trip so could run either SOLO but simply plug them in to a XT60 when running together. No fancy switch required.
I would have a choice of running together for the first 1/2 of the trip or the second half as could run the LIFE - SOLO until at around 25% capacity and then recharge to FULL then put in parallel to get back home. I would NOT have the option of running together for the whole trip though unless it is less than the capacity of both in parallel.
I would have to see how far each goes. I already know that the LIFE packs are limited to < 10 miles. NOT sure about the SLA. I am only guessing they can go further. Hopefully together I can get somewhere between 15 and 20 miles. If I can then will be worth doing especially if I can get a little better performance from the rear chain drive on the Currie.
I am looking for a better controller. Electric scooter parts has 40 amp - 36V brush controllers for about $60. I would like to find something for about $20 but do NOT see it. Just those ones that have a speed control knob for a throttle.
I am going back to read more on that 2008 post.
If anyone wants to post on their experience with LIFEPO4 running SOLO or in parallel with SLA or LTOs please post. My LISHEN - LTOs are rated at 18 Ah. The LIFE - 19 Ah but a sketchy 19 Ah.
OK. That is the end summery of that 2008 post.
Balancers are still too expensive. I'm just fishing for ways to balance my SLA's for around $40 and this "hack" could do it.
I suspect that since this balancer is looking for a range that is at most 26 volts that my four cell 48 volt SLA set would need to use two of them. So I'm already up to $80.
At present I've figured out a "caveman balancer" that exploits the parallel connection of the SLA's and it seems to be working, but I'd like to drop the NiCads and go back to just the SLA's one day. The SLA's without a balancer create "runts" too fast and it gets expensive to replace the "runt" all the time.
--------------------
As for the main topic:
"Yes" we can conclude that mixing chemistries works great. You can change the behavior of the battery by altering the way you mix the chemistries in both series and parallel configurations.
SLA + LiFePO4 or NiCad ----> Parallel : Eliminates SLA "Sag".
SLA + LiFePO4 or NiCad ----> Series : SLA's placed in parallel can reduce the "C" rate and give low tech balancing. SLA "Sag" will be present.
There was a link to some sort of charger to use for the SLA to prevent a runt cell however that link went nowhere as almost 15 years old. I am basically trying to shed some new light on a very old topic.
All I know is it could work for awhile but eventually will want a larger higher capacity LIFEPO4 pack or switch back to Lion/LiPo.
I remember DA. saying that solor power is a waste of $$$$$ as will only get 11 cents of energy.
HOWEVER!!!!!
What if the grid goes down !!!!!! The unthinkable !!!!
It would be nice to have some energy that is renewable off grid. something beats nothing !!!! Those old SLAs even at 50% capacity could work and battery isolators for 12V are common. Four to six - $24 - 225 cranking amp lawn mower batteries are around 33 Ah each. Add some old SLAs as well as a bunch of 18650 cells using 12V battery isolators for each chemistry.
Looking at either building a shed or getting a pre fab if I get a trailer or finding a place with a garage to put solar panels on the roof. Inside will be a charging station and all my e bike batteries fully charged on a charger 24/7.
Now to my biggest question. What is the difference between a battery isolator and a diode ?
That illustration could represent the hooking of different battery chemistries to a controller just delete the solar panels and switch the DC to AC converter to an e bike controller.
Obviously will not be doing all those different chemistries together for an e bike but could do two different battery chemistries using the diodes but any two chemistry combinations, NOT just LIFE and SLA. ???????
Not sure where to buy or order diodes but wondering what the difference would be running the LIFEPO4 in parallel with the SLAs using diodes. They would still share the load but one battery chemistry would NOT feed the other. Would that lower the chance of the runt cell discussed in that 2008 thread or make no difference ????
Please let me know.
Thanks.
LC. out.
