I inherited a 24V 20Ah lead acid mower, the battery is beyond shot, and instead of investing in a new lead acid battery is there something out there (a hobby charger or power supply) that would let me use the mower, it needs 24V, and i’m guessing 20-30Ah of juice.
bump
If all it needs is a battery it just may be worth the investment. It sounds like it is one of those Worx machines.
its similar, the replacement batteries would cost about $125 so a solution that is cheaper would be nice.
I hate lead acid batteries, they are fickle, lose capacity almost arbitrarily (i take care of them extremely carefully), and are dead in a few years anyways.
The cheapest lipo for 500Wh at hobby king (6s) would run me about $200 so its not any cheaper and i just don’t have that kind of money. I may even need 7s which may be more expensive.
Say you need 24V and 25AHr. Total is 24*25=600W.Hr
One 18650 is about 10W.Hr.
You need 60 of them.
Say you can get 1 18650 for $1 (laptop battery pulls.)
$60 + the danger of using unmatched 18650s.
Probably not worthy it to build by yourself. Maybe look for some discount product.
500Wh, if i had the equivalent in laptop pulls i would be using it if i could find a way to link them all together and charge them and balance them
I have a grand total of 6 laptop batteries from one pack
I use 2 x 5000mah 11.2v LiPo’s in series on my 24v Pb lawnmower with no problems. The price for both batteries was around $50 at hobby king
These ones
I did consider these
but it would take 4 to equal the original output, costing $160, more then the replacement battery, the one you mention requires 8 batteries which would cost $200
You don’t really need to match the Wh or Ah rating of the original battery pack. Doing so will give you the equivalent runtime, but if you’re fine with shorter cycles, you can go with a smaller battery pack and less cells.
Just make sure you have the same voltage and current rating, you don’t want to overload the cells.
According to a review of the mower the current battery is 1/2 U1 @ 12v, two of them in series, they seem to cost about $60 each
i never got to use it when the battery worked so i don’t know how much of the charge is used per mowing, i wish i did know
You can approximate the current draw by dividing the rated battery capacity and dividing it by the rated run time.
An AC adapter probably can’t deliver enough current to power it though.
its rated runtime is an hour, so 20A, i just don’t know if i use it on my lawn how much of the charge is used up, if i had to guess i would think all of it.
24x20 is 480 W, an outlet can put out 1500W, so thats not a problem, but i have no AC to 24V20A DC converter.
Apparently this is the battery in it (i should pop the cover and check)
These are pics, right click view image for full size
I am guesstimating my yard at 4000 sq/ft
If i go the Lipo route what can i use to charge it, the only lithium chargers i have are a ML102 18650 charger so i assume i need a hobby charger, whats a good and cheap one with a power supply?
How fast can one charge lipo, 1C, 0.5C? Is there an ideal charge rate for maximum life?
You really don’t need that many batteries with LiPo’s remember that Pb have voltage sag under load that’s why they put 20ah batteries in them, My lawnmower has a 15 amp startup current and a 9-10 amp continuous working current, the LiPo’s can easily give that current and more, I usually mow the back yard in about 10 mins and the LiPo can handle it. I have been using LiPo for about a year now.
When it’s time to replace the LiPo I might consider a 7S 5000mah battery just for the extra voltage and probably a bit more runtime. which is really not that important, because I can charge the pack in 1 hour or less with the hobby charger.
Edit, you need a Hobby charger I have an accucel-8 also from hobbyking and charge at 1C (5amps)
And this is my Dell 13.8v 100amps server power supply
Here is my setup, way lighter than yours :bigsmile:
The problem I found powering these sort of things from the mains through a transformer, was the initial start up current draw which can often be 3 to 4 times the running current draw
Have a look on an electric bike forum if you want to get an idea of people building battery packs from laptop cells, should be quite easy as you only need to build a small pack compared to some of the huge ones they build.
That’s not to say you won’t get good advice on here, it’s just that they like building battery packs, like we like building ever better brighter lights
Although I often just resort to using sla batteries, if you get quality ones and keep them on a float charge when not in use , i’ve got many years out of them without issue.
But buy them from somewhere that has a high turn over of stock, so you know they are new and not stock that has been sitting around deteriorating (often the reason people complain they don’t last long before failing) somewhere that sells mobility scooters is a good place to get sla/gel batteries
They don’t seem to fair to well if left idle, even with a full charge before being left idle
Can i use an old laptop charger its 19V i think, it says 18V max input