Thread: Problem Charging Aux Batteries with Smart Charger

Ok chaps we are making progress with my problem

I disconnected the negative cables from both batteries so they are separated

then hooked up the charger ( set to normal car battery mode ) to the crank battery .....30 mins later it goes to phase 7 ...float

I then switched the charger ( now set to AGM mode ) over to the optima and about 30 mins later it also goes to float

so what should I try now ....re hook the two batteries together and see if I can get them both
to go to float ...and which battery should I hook up to given the crank is a normal wet battery
and the optima is a AGM and my charger has a mode for each ? .....I think the charging voltage for the agm mode on the charger is higher ( 14.7) than the normal capacity mode (14.4)

Hi again Landoman, first off, you can leave your charger set to anything but CALCIUM mode, if your charger has that setting.

Next, as you have suggested, connect up your batteries as normal, and then try charging them with your charger connected to the cranking battery.

Hey Drivesafe, just confirming that the SC80 will allow current to flow back through the unit from auxillary to main battery??

Hi Chris, if it is a first generation SC80 isolator, then while the voltage is above 12.0v, current will flow in either direction.

Current will flow from the highest charged battery to the lower charged battery, regardless of whether the cranking battery or the auxiliary battery is the highest charged.

With the new Second Generation SC80 isolators ( all SC80 units sold after April 1, last year ) will operate the same as above, but if a new SC80 has either Timedout or the common voltage has dropped bellow 12.0v and the isolator has turned off, then if a charge is applied to the auxiliary battery, once this voltage rises above 13.2v, the SC80 ( or a DT90 ) will turn on, allowing the cranking battery to be charged as well.

Originally Posted by drivesafe

Hi Chris, if it is a first generation SC80 isolator, then while the voltage is above 12.0v, current will flow in either direction.

Current will flow from the highest charged battery to the lower charged battery, regardless of whether the cranking battery or the auxiliary battery is the highest charged.

With the new Second Generation SC80 isolators ( all SC80 units sold after April 1, last year ) will operate the same as above, but if a new SC80 has either Timedout or the common voltage has dropped bellow 12.0v and the isolator has turned off, then if a charge is applied to the auxiliary battery, once this voltage rises above 13.2v, the SC80 ( or a DT90 ) will turn on, allowing the cranking battery to be charged as well.

Thanks. Mine will be an older version so as long as the batteries are linked (solid light) then I can charge either battery and it will cross link and charge the other battery also.
Thanks,
Chris.

Originally Posted by drivesafe

Hi again Landoman, first off, you can leave your charger set to anything but CALCIUM mode, if your charger has that setting.

Next, as you have suggested, connect up your batteries as normal, and then try charging them with your charger connected to the cranking battery.

Ok reconnected the two batteries the SC80 was turned off ( blinking light ) so started the engine and it came on ( solid green light ) and put the charger on the cranking battery and in a few minutes it went to float

I then switched the charger to the optima and again after 5 -10 mins it also went to float

now here is the thing ...I then plugged in the charger to the anderson plug at the rear ( which
goes to the optima via 8 AWG cable ...and it's seems stuck on phase 4 absorption ....been like that for about 30 mins now ....the voltage at both batteries is 14.69 coming From the charger at the anderson plug at the rear . The charger is set at AGM mode which according to the charger manual charges at 14.7 volts

so what can I conclude from all this ?

While I would expect it might eventually go into float mode, but because of the voltage drop caused by the 8B&S cable and possibly some bad connections causing more voltage drop, it may never go into float mode.

You could experiment with just charging the auxiliary battery.

To do this, again, disconnect the two negative battery clamps for a minute or so and then reconnect the clamps but don’t start your motor, just connect your charger to the Anderson plug and see if it can go into float while charging just one battery.

Originally Posted by drivesafe

While I would expect it might eventually go into float mode, but because of the voltage drop caused by the 8B&S cable and possibly some bad connections causing more voltage drop, it may never go into float mode.

You could experiment with just charging the auxiliary battery.

To do this, again, disconnect the two negative battery clamps for a minute or so and then reconnect the clamps but don’t start your motor, just connect your charger to the Anderson plug and see if it can go into float while charging just one battery.

Ok so it looks like we have a win .......I disconnected the charger from the anderson plug
and put it back on to the optima ....after a short while it went into float ......so I took it back to the anderson plug left it connected ....and finally it is in float with both batteries connected
Via the SC80 and the charge coming from the anderson plug at the back .........Hooray !!

So can I conclude that given both batteries connected together have gone to float that they are both ok .....???

and yes Tim perhaps the 8B&S cable may be making the charge harder to get through from the anderson ..............for those chaps who charge this way ...what B&S cable do you have ?


perhaps given my batteries have only only ever been charged over the last few years via the alternator and the optima has been run down quite low on a few occasions they needed a long time on the charger to get them to float

Anyway delighted that at least it all seems to work ...and I can always get the batteries to float stage by connecting the charger to them directly .....although I like the idea of going via the back anderson plug