An 80-year-old friend helps control his diabetes by riding his bike about 2km to a coffee shop a few times a week. He depends mostly on one leg, the knee of the other was ruined by many years as an amateur baseball catcher. Return trip is slightly uphill, I'd say about a 10-15 degree grade, so for parts of that he needs the assist of the Currie 12V bike motor, otherwise he has to get off and walk.
The original two 12V SLA batteries (12 AH as I recall) were fine for about a year. Then we got some 8AH ones from another friend who works for an alarm company, by regulation they have to replace alarm batteries after a year or two even if they've never been used. In the process of replacing the batteries we fried the Currie 24V charger (we assumed white wire was negative and red wire was positive when for some reason, red was negative and white was positive!). So we found a 28V wart adapter and for the next year or so he'd plug that in for a couple of hours after each ride.
What I've noticed is that with both setups, one battery went south long before the other, based simply on checking them with a little PulseTech conductance tester that estimates CCA's. For example one of the original 12AH batteries measured 170 CCA or so (still does, I put it on a maintainer for a day or so every month or two). Whereas the other measured less than 50 CCA. Similar difference between the two 8AH batteries, the good still measures a bit over 100 CCA.
I'd say my friend does this routine about 150-200 times a year, so he and I aren't unhappy about the longevity of these batteries and we're basically getting them for free. However, I have a couple of small maintainers I got on sale and since I know very little about circuit analysis beyond the most simple kind such as a single voltage source and load, I'm wondering if it's possible to charge the two remaining batteries that look good to me while they remain connected in series, each connected to one of the 12V maintainers, without having to install a switch to open the series connection.
Grateful for any pointers or reasons why this might be a stupid idea!
The original two 12V SLA batteries (12 AH as I recall) were fine for about a year. Then we got some 8AH ones from another friend who works for an alarm company, by regulation they have to replace alarm batteries after a year or two even if they've never been used. In the process of replacing the batteries we fried the Currie 24V charger (we assumed white wire was negative and red wire was positive when for some reason, red was negative and white was positive!). So we found a 28V wart adapter and for the next year or so he'd plug that in for a couple of hours after each ride.
What I've noticed is that with both setups, one battery went south long before the other, based simply on checking them with a little PulseTech conductance tester that estimates CCA's. For example one of the original 12AH batteries measured 170 CCA or so (still does, I put it on a maintainer for a day or so every month or two). Whereas the other measured less than 50 CCA. Similar difference between the two 8AH batteries, the good still measures a bit over 100 CCA.
I'd say my friend does this routine about 150-200 times a year, so he and I aren't unhappy about the longevity of these batteries and we're basically getting them for free. However, I have a couple of small maintainers I got on sale and since I know very little about circuit analysis beyond the most simple kind such as a single voltage source and load, I'm wondering if it's possible to charge the two remaining batteries that look good to me while they remain connected in series, each connected to one of the 12V maintainers, without having to install a switch to open the series connection.
Grateful for any pointers or reasons why this might be a stupid idea!