I’ve no budget. No that’s doesn’t mean I’ve an unlimited budget. Far from
I’ve a target and then decide the price is right for what I get.
Less weight for the same usable capacity is something I would pay extra for.
Possibly I’m going to recharge using a simple solar panel. When I do I want to take full advantage of the sun when available. I don’t really care if recharge takes 10 hours, but still I want it much faster in case it gets cloudy. For lead-acid the adviced charging amps are C/10. For LifePO the numbers I found vary to much to be of any use. Anyway, if LifePO can recharge at a much higher speed, that would be something I would pay extra for.
My target is quite modest. 500 Wh would be very good, but half is acceptable.
This is also a learning experience. If I know the ins and outs of a small setup, it’s quite easy to upgrade.
As far as I know even the shittiest LiFePO4 battery can be charged pretty fast: at 1C rate I'd bet. In fact, speaking of LiFePO4 I don't see a reason not to try even higher rates, at least for decent quality cells.
Only 500Wh, ZoomieFan?
If you are willing to solder, spot weld cells or just order a pre-assembled battery, take a look at this 26700 cell: LiitoKala 26700 4000mAh Lii-40E (Orange) -in fact, now that I recall I paid for these cells to get reviewed at lygte-info.dk LoL-. This cell is also made by Power Long Battery (can't say 100% sure, but considering that the flat-top geometry of cells is like a fingerprint, that is the reason I say such a thing; it also is a pretty good cell, while PLB is probably the most reputable cell manufacturer in China… the numbers match).
The cell delivered above 13Wh at 1C discharge, and pretty close to that even at much higher rates. Even if you consider a little bit less energy density per cell to “stay on the safe side”, for 500Wh the price of a pack can be very affordable. Take a look here at this LiFePO4 26700 custom search. Out of it: https://www.aliexpress.com/item/1005001556693880.html Under $50 for a 20-pack to USA or Netherlands, shipping included. They also sell many other big battery cells, and so you may be able to order some special request like a preassembled 8S6P (12V) or 4S12P (24V) battery. With 48 cells, the pack would yield above 600Wh guaranteed.
Barkuti,
I’ve been considering 18650’s and 21700’s.
But how am I going to charge them?
That same question applies to the LiFePO4 batteries. I assume ordinary car battery chargers won’t work.
And even if they do, high amp chargers are quite ‘rare’. The most certainly exist but most seem to be around the 5-10Amp mark.
HJK suggests 2A charging for the orange cells. That 0.5C, not very high. But the 4C discharge is very nice.
That $50 will turn out a bit higher…
Above e22, 21% tax is added. Plus a e15 processing fee.
If I really pay that depends what the Chinese shop puts on the package. Quite often it’s hardly half of what I paid. Perhaps it’s the price they paid to the factory.
I could order them when in the USA. But lockdown…
Absolutely don’t let a car battery charger in the same zip-code as a lithium battery. Unless you like fire.
A completely different set of charging parameters is used for Lithium batteries.
Some lithium battery packs are designed with BMS built in so that they can be used with conventional chargering applications. The Battle Born batteries come to mind that can be used as a direct replacement for many lead cell applications. Bring the big checkbook.
Anytime you put cells in series and expect to charge them without separating them, you will need a BMS.
A Battery Management System. This is a device that equalizes the charge across the pack so that poorer cells will not get pulled down after multiple charge – discharge cycles.
This is what typically happens in older NiCd power tool packs. Eventually one or more of the batteries actually reverses polarity and needs replacement.
Modern packs (should) have a BMS to prevent over discharge, overcharge, and keep the cells equalized.
It’s the red thing in the video in my previous post.
All the Best,
Jeff
