2 x 100amp 12v batteries - questions

Treecrest14 · Senior Member

2 x 100amp 12v batteries - questions

Aus-Kiwi · Guru

To solar over both batteries. I guess they are parallel wired for 12v ? Depends on regulator ? If it's 24v then yes connect series as in 24 v lighter cable required . But IMO would keep it the same as supply ., depends what you use ? These days we tend to buy appliances which run on 12v DC direct . So other than microwave, elect jug . The inverter is not used as much ..

oldtrack123 · Guru

Q1

It will not make any real difference which way you go provided ALL connections to the batteries are clean metal to metal contact &are tight

[2]Why are even considering a DC DC charger??????

What do you hope to gain??

Treecrest14 · Senior Member

The background:

I had the charger wired to the + on 1 and the - on the other. But then got to thinking it might be better to connect the charger to the one battery. Anyway now noticing that the battery seems to be slowly discharging, and can't find any item/appliance switched on (except a volt meter which is connected to the batteries)! Hence the questions..

DC to DC was grasping at straws as to why the slow discharge.

oldtrack123 · Guru

It could be that one or both of the batteries has high internal leakage [self discharge] it would also pull the other one down
Suggest you either get them both tested or do a simple check yourself by:
[1[ disconnect the batteries from each other & any load
[2]fully charge each individually
[3]disconnect charger from battery, let stand for a few hours then check voltage
[4]recheck voltage after say 24 hours

if either shows much less than 12.6/12.7v it could be the problem.[n any case come back with those readings

[a]Is this a problem that has suddenly occurred?

Are they van batteries??

[c]Over what period do time do they discharge & to what voltage?

[d]Amphr rating of each?

-- Edited by oldtrack123 on Tuesday 20th of September 2016 11:26:59 AM

Aus-Kiwi · Guru

If they are bridged to be 12v ? Both will charge anyway . My assumption on DC 2 DC is when you have batteries some distance away and cables MAY have voltage drop over distance . So increasing voltage ( pressure) is one simple step . As you need higher volts to charge another battery . 12v can be very lazy .. Think of the old cars with 6 volt systems ? Sheesh !! Lower volts / higher amps to do same.. Always proportional ..

macka17 · Guru

Stop at a battery/tyreplace on travels.
Get them to do a "load test" on each battery.
Most will.

Simple. quick and will tell you what each battery is. usage wise.
Do same on car batt at same time too.

Everything deteriorates. even you (me. us.)

Could also be that you don't have or not giving enough input from solar too.
2 x 100a Battery's.
you'll need around 340w of panels Minimum...to maintain capacity.
and that's up here in the North.
More down South.
Wire Pos to Pos. and Neg to Neg. , then pos/neg to van wiring/fuses..
Regulator to the single Pos/neg wired that come from there.
Closest to battery's.
AC Charger to same Battery connections in boot/battery space.

Genny in tray or boot of car for bad times.

Peter_n_Margaret · Guru

oldtrack123 wrote:
It could be that one or both of the batteries has high internal leakage [self discharge] it would also pull the other one down
Suggest you either get them both tested or do a simple check yourself by:
[1[ disconnect the batteries from each other & any load
[2]fully charge each individually
[3]disconnect charger from battery, let stand for a few hours then check voltage
[4]recheck voltage after say 24 hours

if either shows much less than 12.6/12.7v it could be the problem.[n any case come back with those readings
[a]Is this a problem that has suddenly occurred?
Are they van batteries??
[c]Over what period do time do they discharge & to what voltage?
[d]Amphr rating of each?

Take note of what Peter said above...

Battery testing by retailers is useful to determine the crank capability of a battery. It is not necessarily relevant or useful to indicating the condition of lower recombination rate house batteries.

Cheers,

Peter

Aus-Kiwi · Guru

Trouble is SOME say battery is buggered when it isn't !! Well ? I got another 3 years out of one set . Even then sold on .,'