Thank you for sharing your dream with us. Please take everything that I share back to the Holy Spirit as He Alone gives the accurate interpretation.
To answer your question, I have had one dream about 4-6 years ago of my former boss at the time riding a lawnmower and he looked much thinner that he did in real life. I new the meaning.
In the context of your dream, the lawn could represents the “area or environment” of your husband work/ministry. The actual lawnmower could represent his actual work/ministry. The fact that the lawnmower broke down may mean that he might have challenges with his work and I sincerely hope it doesn’t “break down.” Nevertheless, he went to a car dealership looking for a battery and a man (who I believe it is God/Holy Spirit/an angel) guided him appropriately. Your husband may need to seek God’s direction when things start going awry with his work, but the good news is that he WILL get clarity and direction. Hallelujah!