I could write the book on maximizing battery life and performance, sharpening the blade every mow, mowing dry lawn twice per week, graphite coating on perfectly smooth underside of deck, etc. I have also figured out that swapping batteries seems to make the mower recover faster and run longer before overloading again.
Since both batteries were fully charged, and I noticed they come out of the mower much hotter than usual, I decided to stick the other one in the freezer when not in the mower as I swapped them out. 5 minutes in the freezer doesn't even get a hot battery down to room temperature, but much cooler than sitting in a 95 degree garage. Cooling the battery for a few minutes doesn't keep the mower from overloading, but it does keep it working between shutoffs for a few precious seconds longer.
So, if a little cold is good, is a lot better? Could I stick my fully charged batteries in the freezer overnight before mowing the next day, putting an ice cold battery in the mower instead of room temperature? I don't know a lot about battery cells, but I do know that heat is bad so it seems like cold would help extend life and run time, as well as reducing overload shutoffs.
Hi Big Dave,
You took me down memory lane, when I was a kid, the engineers stored all of their batteries, from flash light batteries on up in their fridge.
My batteries are getting a bit more heated than last year, but it's 10 degrees warmer outside than last year, it's just plain brutal! I wonder if a small vend/fan inside the battery compartment of the mower would be helpful. Not an unreliable circular fan, but one of those blower types. They never burn out, use next to nothing with current and move a lot of air.
However, a refrigerator usually stays a few degrees above freezing which is well within the operating range of the battery. Sticking your fully charged packs in the fridge over night might get you a little bit more mowing time before the cells get hot.
Do keep in mind, the mower has its own overload protection that will intervene regardless of battery temperature.
It hasn't been hot enough this summer where I live for overheating to be a problem, but to SCDC's point, I often wonder whether simply removing the green plastic cover over the battery compartment would be a good idea on hot days to allow more air to circulate around the battery.
Instead of continuously swapping batteries to cut one pass at a time between overloads, I fully charged the 4Ah battery and put it in the freezer for three hours. (This was before I realized 32 degrees is the minimum operating temp, but did not experience any pulsating as described in the manual so may not have gotten core temp down below freezing.)
I resumed mowing where I left off with nothing else changed, and finished the rest of my back yard and all of my front yard on a single charge without a single overload shutoff.
If my lawn caused the thing to overheat every few minutes I would call it a day and return it. I have pretty dense grass and have it turn yellow every once and a while, but if you are getting so many overloads I would raise your deck height to max, check for debris/sharpen. Maybe you have defective battery?
When I say that, however, I must add that the packs are never warm where it counts; that is, they are cool to the touch down on the body and in the center of the pack where the terminals are. If the battery cells were getting hot this is where you would feel the heat.
I HAVE noticed that, when cutting the grass under bright sunny skies, that the TOP of the battery pack is quite warm. I believe this is due to the sun heating the black rubber battery cap and the lack of ventilation in the battery compartment.
I have wondered if putting a reflective "shield" under the battery compartment lid would help keep the top of the battery cooler while cutting. The issue I see with this is it would keep you from seeing the status light on the battery, but since the mower has its own status lights I don't see this being an issue.
Clearly the ambient temperature of the battery is the issue, not the amount of heat generated by the battery or motor during use. So starting with cool (but not frozen) batteries on excessively hot days should solve this problem going forward. Storing them inside the house after charging might even be enough to solve the problem.