Two batteries on one charger...request for advice.

Need some advice...

I busk using a Fender Amp Can and a head set mic. The Fender amp can is a complete unit with speaker, amp, battery and charger (15v 400mha). The headset mic I run off a separate 12v SLA battery.

I currently open up the Amp Can disconnect the internal battery, attach the external battery and charge it, then put the whole unit back together. I want to make an external terminal to connect the external battery for charging and this should be simple enough says I...hmmm...So I am canvassing for second opinions regarding possible problems and whether I should set the batteries in parallel or series?

The Amp Can is an awesome little unit and Fender have stopped producing them so I don't want to do it any harm.

I know I could just buy a separate charger for the battery but that would be more crap for me to carry and I don't have the $25  to spare just now...it would also be lame...

Thanks for listening,

Some specs on the Amp Can:

PART NUMBER 022-1270-000  (100 V)
022-1200-000  (120 V)
022-1230-000  (240 V) Aust
022-1240-000  (230 V) UK
022-1260-000  (230 V) Euro
POWER OUTPUT 14.5 W into 4 � @ 5%THD
with fresh battery 
INPUT IMPEDANCE > 1 M� both channels
INPUT SENSITIVITY 500 µV@ 1 kHz - gain switch in
GUITAR 20 mV @ 1 kHz - gain switch out
SPEAKER 4 â�¦, 30 W Special Design 6” speaker
w/16 oz. magnet and paper coil former
(P/N 050543)
DIMENSIONS Height: 8.75 in  22.3 cm
Width: 7.75 in 19.7 cm
Depth: 6.75 in 17.2 cm
WEIGHT 13 lbs 5.9 kg
Amp Can™ is a trademark of FMIC.
®, Tone-Master
® and Twin Reverb® are
registered trademarks of FMIC.
Product specifications are subject to
change without notice.

lemonie7 years ago
If you're taking the battery out to charge it, not taking it out should be simple. You should install a heavy-duty switch and a socket. Or if you want to swap between two sources just wire a little differently.

tkosam lemonie6 years ago
Hello, i bought a fender amp can and hooked it on a solar panel, that is, i charge the big battery 12V/40Ah and from this battery, through the regulator, i charge the fender amp can, BUT, it is not charging, although the light green IS ON the amp, but, yesterday i charged it like 8 hours, it was completely empty (the light, that shows how much battery is in, was RED) and today i plugged an electroacustic guitar, set the amp only on 2, and after 2 minutes the light went from green to red, without gradation....

Im asking for advice, what to do to make the charging efficient?

thanks in advance

lemonie tkosam6 years ago
Your big battery can supply (for example) 1A for up to 40h. To charge that back up from flat, you'd need the same again, or fast-charge with 4A for 10h.

How many amps can the solar panel supply?

Second consideration: are you getting more than 12V out of the solar panel? Because it will have to "fight against" the battery's 12V to push current through it.