swapping and charging batteries

[swimmer_spe]

I have a 1 year old trailer. It came with a deep cell battery, and it is good. I plan on adding a second battery. I have 2 older ones,that at the time, were good. Today,I swapped out my good battery for one of the older ones to let it change for a week or so with the trailer's charging system. When I plugged it in,it was at 12.5V. I have not charged it since sometime last summer, or the fall before. Not bad...

[swimmer_spe]

wa8yxm wrote:

swimmer_spe wrote:


12.5v after plugging it into the trailer,not into shore power.

I sort of thought that was what you meant But it's not how I'd have said it (hooking up the battery to trailer)

Which is why I covered all options (I hope)

12.5 after sitting on the shelf for a month or even a week is not bad at all. In fact with most meters it's within the margin of error for PERFECT. less you lab calibrated (Gads... Been a lONG time since I lab calibrated a meter)

This one sat at least a year. Could be even longer. I have another that has sat that long that next week I'll be swapping it onto the trailer so it can get a good charge before using it.. Both of these batteries will only be used once a year, for about a week.

[wa8yxm]

swimmer_spe wrote:


12.5v after plugging it into the trailer,not into shore power.

I sort of thought that was what you meant But it's not how I'd have said it (hooking up the battery to trailer)

Which is why I covered all options (I hope)

12.5 after sitting on the shelf for a month or even a week is not bad at all. In fact with most meters it's within the margin of error for PERFECT. less you lab calibrated (Gads... Been a lONG time since I lab calibrated a meter)

[swimmer_spe]

valhalla360 wrote:

wa8yxm wrote:

opnspaces wrote:
12.5 after a week of charging is bad. A fully charged battery would be 12.67 or above.

He said 12.5 when he "Plugged it in".. Not sure if he mean plugged the battery into the Trailer or the trailer into 120vac

But 12.5 after a long time on the shelf is actually quite good.
12.5 if trailer plugged into 120v is not good.

Agreed, the original post made it sound like he had left it on the charger for a couple weeks.

If it had been sitting on a shelf for an extended period of time not charging, 12.5v isn't bad.

12.5v after plugging it into the trailer,not into shore power.

[valhalla360]

wa8yxm wrote:

opnspaces wrote:
12.5 after a week of charging is bad. A fully charged battery would be 12.67 or above.

He said 12.5 when he "Plugged it in".. Not sure if he mean plugged the battery into the Trailer or the trailer into 120vac

But 12.5 after a long time on the shelf is actually quite good.
12.5 if trailer plugged into 120v is not good.

Agreed, the original post made it sound like he had left it on the charger for a couple weeks.

If it had been sitting on a shelf for an extended period of time not charging, 12.5v isn't bad.

[wa8yxm]

opnspaces wrote:
12.5 after a week of charging is bad. A fully charged battery would be 12.67 or above.

He said 12.5 when he "Plugged it in".. Not sure if he mean plugged the battery into the Trailer or the trailer into 120vac

But 12.5 after a long time on the shelf is actually quite good.
12.5 if trailer plugged into 120v is not good.

[swimmer_spe]

valhalla360 wrote:

time2roll wrote:

swimmer_spe wrote:
When I plugged it in,it was at 12.5V. I have not charged it since sometime last summer, or the fall before. Not bad...

If the battery held 12.5v after sitting for a year... that would generally indicate good condition.

Put them all in use together and see what goes.

12.5 after a week charging is not good. May be marginally OK but not good. Swing by an auto parts store. Most will do a load test for free.

Mixing batteries you get the lowest common denominator so your good battery will be drug down by the marginal battery

12.5v is what it read before charging. I will let it charge for a week and see how it is.

[valhalla360]

time2roll wrote:

swimmer_spe wrote:
When I plugged it in,it was at 12.5V. I have not charged it since sometime last summer, or the fall before. Not bad...

If the battery held 12.5v after sitting for a year... that would generally indicate good condition.

Put them all in use together and see what goes.

12.5 after a week charging is not good. May be marginally OK but not good. Swing by an auto parts store. Most will do a load test for free.

Mixing batteries you get the lowest common denominator so your good battery will be drug down by the marginal battery

[swimmer_spe]

time2roll wrote:

swimmer_spe wrote:
When I plugged it in,it was at 12.5V. I have not charged it since sometime last summer, or the fall before. Not bad...

If the battery held 12.5v after sitting for a year... that would generally indicate good condition.

Put them all in use together and see what goes.

That is the goal.

[time2roll]

swimmer_spe wrote:
When I plugged it in,it was at 12.5V. I have not charged it since sometime last summer, or the fall before. Not bad...

If the battery held 12.5v after sitting for a year... that would generally indicate good condition.

Put them all in use together and see what goes.

[swimmer_spe]

CA Traveler wrote:
It's not clear when you saw 12.5 vs plugged it in, but if it was charging then the voltage doesn't reflect battery charge state.

Regardles now that it has charged do a load test to determine the battery condition.

Shore power was disconnected. It jumped to 13.7v once plugged in.

[CA_Traveler]

It's not clear when you saw 12.5 vs plugged it in, but if it was charging then the voltage doesn't reflect battery charge state.

Regardles now that it has charged do a load test to determine the battery condition.

[opnspaces]

12.5 after a week of charging is bad. A fully charged battery would be 12.67 or above.