Replacement cells for automatic lawnmower battery packs

[Mowerguy]

Hi, Im looking to restore some old battery packs I got laying aroud to see if there are good replacement cells that may be a good choice instead.
Originally they are equipped with Sony/ Murata VTC3 and VT5 depending on age and capacity.
I know that these are really good cells, and they use to last very long. Many times 2-3000 cycles before capacity is that low so that the machine cant go home by itself anymore. The mean current draw on these machines is not that high, usally a 5000mAh pack lasts for around 3h operation, and with some margin in SOC of cause.
Charge on the other hand can be up to 0.8C and it could be a sunny hot day or cold.
I guess most after market packs use energy type cells because they are cheap, but probably with shorter life of the pack.
So focus must be to find suitable good priced cells that can make a almost as good pack as the original ones, with service life as close as possible.

I have been looking at EVE 25P and 33V as a good choice that is not that pricy. Could these cells be a good choice?
Some advice would be apreciated!

Thanks

 

[TDA78]

I would assume the designers had a good reason for choosing a 20A cell over higher capacity. The EVE 25P is a good budget replacement. I'd go with Molicel P30B if money was no object, they were available, and they fit in the cell holders.

 

[Mowerguy]

Thanks for your reply.
I am sure the full power capacity of the cell is never used, but probably its good for long service life and charging at higher temperatures.
The BMS shutoff is around 15A.

The Molicel looks very good and i see they had lower capacity power type cells too.
I am looking at the Eve as they have a good price and is very close too original spec. But I have not seen any test with power type cell in lower C-rate charge and discharge and life cycle test during those conditions.
And the 33V I have seen been tested with very good results up to 1000 cycles. And it's a bit higher capacity so it should also be good for many cycles as the machines only uses a fixed amount of Ah regardless of cell capacity, so SOC window usage will be lower on bigger cells. And also this 33V cell seems reliable.

 

[TDA78]

Even if a 10A cell doesn't overheat, the voltage may sag too low when the blade spins up. The BMS low voltage cutoff may be triggered or the guidance processor may lose power.

 

[Mowerguy]

Thanks for that!
I did not noticed the Molicel brand before, and now it seems like a obvious choice!

Its better to take any chances then.
I looked at bit into Molicel and their older cell P26A seems like a good replacement for the VTC5. And if i go with the 28 or 30 the performance will be better than original.
I will go ahead and try that!

Many thanks!

 

[amberwolf]

If you ever need to compare various cells, I recommend the various cell testing threads here on ES and the Flashlight information battery testing site.